When was the training for the TA supposed to resume?


How much of the UK's troops are provided by the TA?

In October 2009, the MoD was heavily criticized for withdrawing the bi-annual non-operational training £20m budget for the volunteer Territorial Army (TA), ending all non-operational training for 6 months until April 2010. The government eventually backed down and restored the funding. The TA provides a small percentage of the UK's operational troops. Its members train on weekly evenings and monthly weekends, as well as two-week exercises generally annually and occasionally bi-annually for troops doing other courses. The cuts would have meant a significant loss of personnel and would have had adverse effects on recruitment.


How often do the TA troops regularly train?


By how much did the MoD go over its equipment budget?

In 2013 it was found that the Ministry of Defence had overspent on its equipment budget by £6.5bn on orders that could take up to 39 years to fulfil. The Ministry of Defence has been criticised in the past for poor management and financial control, investing in projects that have taken up to 10 and even as much as 15 years to be delivered.


When was the overbudget amount discovered?


What are some of the criticisms that have been directed at the MoD?


What is a long-range estimate on fulfillment of some of the equipment orders made by the MoD?


Past projects ordered by the MoD have taken what type of time frame to fulfill?


The term "high definition" originally described televisions systems from what year?

The term high definition once described a series of television systems originating from August 1936; however, these systems were only high definition when compared to earlier systems that were based on mechanical systems with as few as 30 lines of resolution. The ongoing competition between companies and nations to create true "HDTV" spanned the entire 20th century, as each new system became more HD than the last.In the beginning of the 21st century, this race has continued with 4k, 5k and current 8K systems.


Earlier television systems were based on what?


During which entire century were companies and nations trying to achieve true HDTV?


In what century were 4k, 5k, and 8k systems introduced?


What is the most current HDTV system development?


The British high-definition TV service started trials in August 1936 and a regular service on 2 November 1936 using both the (mechanical) Baird 240 line sequential scan (later to be inaccurately rechristened 'progressive') and the (electronic) Marconi-EMI 405 line interlaced systems. The Baird system was discontinued in February 1937. In 1938 France followed with their own 441-line system, variants of which were also used by a number of other countries. The US NTSC 525-line system joined in 1941. In 1949 France introduced an even higher-resolution standard at 819 lines, a system that should have been high definition even by today's standards, but was monochrome only and the technical limitations of the time prevented it from achieving the definition of which it should have been capable. All of these systems used interlacing and a 4:3 aspect ratio except the 240-line system which was progressive (actually described at the time by the technically correct term "sequential") and the 405-line system which started as 5:4 and later changed to 4:3. The 405-line system adopted the (at that time) revolutionary idea of interlaced scanning to overcome the flicker problem of the 240-line with its 25 Hz frame rate. The 240-line system could have doubled its frame rate but this would have meant that the transmitted signal would have doubled in bandwidth, an unacceptable option as the video baseband bandwidth was required to be not more than 3 MHz.


Which country developed the 441-line system?


What prevented France's 819-line system from achieving the definition it was capable of?


Which system used interlaced scanning to correct the flicker problem of the 240-line?


What year did color broadcasts start in the US?

Colour broadcasts started at similarly higher resolutions, first with the US NTSC color system in 1953, which was compatible with the earlier monochrome systems and therefore had the same 525 lines of resolution. European standards did not follow until the 1960s, when the PAL and SECAM color systems were added to the monochrome 625 line broadcasts.


How many lines of resolution did the US NTSC color system have in 1953?


The PAL and SECAM were color systems where?


How many lines of resolution were the European monochrome broadcasts?


What is the Japan Broadcasting Corporation called?

The Nippon Hōsō Kyōkai (NHK, the Japan Broadcasting Corporation) began conducting research to "unlock the fundamental mechanism of video and sound interactions with the five human senses" in 1964, after the Tokyo Olympics. NHK set out to create an HDTV system that ended up scoring much higher in subjective tests than NTSC's previously dubbed "HDTV". This new system, NHK Color, created in 1972, included 1125 lines, a 5:3 aspect ratio and 60 Hz refresh rate. The Society of Motion Picture and Television Engineers (SMPTE), headed by Charles Ginsburg, became the testing and study authority for HDTV technology in the international theater. SMPTE would test HDTV systems from different companies from every conceivable perspective, but the problem of combining the different formats plagued the technology for many years.


What was the aspect ratio of the NHK Color?


What organization became the authority on testing and studying international HDTV technology?


How many major HDTV systems were tested by SMPTE in the late 70's?

There were four major HDTV systems tested by SMPTE in the late 1970s, and in 1979 an SMPTE study group released A Study of High Definition Television Systems:


Who tested the four major HDTV systems in the late 1970's?


Who released A Study of High Definition Television Systems?


In what year was A Study of High Definition Television Systems released?


What was released by an SMPTE study group in 1979?


Since the formal adoption of digital video broadcasting's (DVB) widescreen HDTV transmission modes in the early 2000s; the 525-line NTSC (and PAL-M) systems, as well as the European 625-line PAL and SECAM systems, are now regarded as standard definition television systems.


When was widescreen HDTV transmission modes formally adopted?


In addition to the 625-line PAL system, what European system is considered a standard definition television system?


In addition to the NTSC system, what 525-line system is considered a standard definition television system?


525 and 625-line systems are now considered what?


In what year did France start transmissions using and 819 line system?

In 1949, France started its transmissions with an 819 lines system (with 737 active lines). The system was monochrome only, and was used only on VHF for the first French TV channel. It was discontinued in 1983.


What country started transmissions using and 819 line system in 1949?


What did France start transmissions with in 1949?


When was France's 819 line system discontinued?


In the end what was the Soviet Union's Transformator system used for?

In 1958, the Soviet Union developed Тransformator (Russian: Трансформатор, meaning Transformer), the first high-resolution (definition) television system capable of producing an image composed of 1,125 lines of resolution aimed at providing teleconferencing for military command. It was a research project and the system was never deployed by either the military or consumer broadcasting.


When did the Soviet Union develop Transformator?


How many lines of resolution could an image using the Transformator system have?


What was the goal of the Transformator system?


In what year did NHK first develop consumer HD television with a 5:3 aspect ratio?

In 1979, the Japanese state broadcaster NHK first developed consumer high-definition television with a 5:3 display aspect ratio. The system, known as Hi-Vision or MUSE after its Multiple sub-Nyquist sampling encoding for encoding the signal, required about twice the bandwidth of the existing NTSC system but provided about four times the resolution (1080i/1125 lines). Satellite test broadcasts started in 1989, with regular testing starting in 1991 and regular broadcasting of BS-9ch commencing on November 25, 1994, which featured commercial and NHK programming.


Who first developed consumer HD television with a 5:3 aspect ratio?


When did satellite test broadcasts of Hi-Vision start?


When did regular broadcasting of BS-9ch start?


When did regular testing of Hi-Vision start?


When was the MUSE system demonstrated in the US first?

In 1981, the MUSE system was demonstrated for the first time in the United States, using the same 5:3 aspect ratio as the Japanese system. Upon visiting a demonstration of MUSE in Washington, US President Ronald Reagan was impressed and officially declared it "a matter of national interest" to introduce HDTV to the US.


What aspect ratio did the MUSE system use when demonstrated in 1981?


Which president declared it "a matter of national interest" to introduce HDTV to the US?


Which system was demonstrated in the US for the first time in 1981?


Which system was demonstrated in Washington to President Ronald Reagan?


Why did the FCC reject systems such as MUSE?

Several systems were proposed as the new standard for the US, including the Japanese MUSE system, but all were rejected by the FCC because of their higher bandwidth requirements. At this time, the number of television channels was growing rapidly and bandwidth was already a problem. A new standard had to be more efficient, needing less bandwidth for HDTV than the existing NTSC.


What was increasing and consuming a lot of bandwidth?


Who rejected systems such as MUSE as the new standard for the US?


What was one of the requirements for a new standard system in the US?


What was the existing system at the time?


What constraints kept HDTV from being widely adopted in the 90's?

The limited standardization of analog HDTV in the 1990s did not lead to global HDTV adoption as technical and economic constraints at the time did not permit HDTV to use bandwidths greater than normal television.


What was HDTV not permitted to do in the 90's?


How much more bandwith was required from early HDTV commercial experiments than an SD broadcast?

Early HDTV commercial experiments, such as NHK's MUSE, required over four times the bandwidth of a standard-definition broadcast. Despite efforts made to reduce analog HDTV to about twice the bandwidth of SDTV, these television formats were still distributable only by satellite.


Efforts were made to reduce analog HDTV to how much of the bandwith of SDTV?


Despite the reduced bandwith, HDTV format still had to be distributed how?


What kind of experiments required over four times the bandwith of a SDTV broadcast?


How many broadcasters did Japan have sharing a single channel?

In addition, recording and reproducing an HDTV signal was a significant technical challenge in the early years of HDTV (Sony HDVS). Japan remained the only country with successful public broadcasting of analog HDTV, with seven broadcasters sharing a single channel.


Which country had successful public analog HDTV broadcasting?


What was particularly challenging in the early years of HDTV?


What accomplishment in early HDTV did Japan have?


Since 1972, International Telecommunication Union's radio telecommunications sector (ITU-R) had been working on creating a global recommendation for Analog HDTV. These recommendations, however, did not fit in the broadcasting bands which could reach home users. The standardization of MPEG-1 in 1993 also led to the acceptance of recommendations ITU-R BT.709. In anticipation of these standards the Digital Video Broadcasting (DVB) organisation was formed, an alliance of broadcasters, consumer electronics manufacturers and regulatory bodies. The DVB develops and agrees upon specifications which are formally standardised by ETSI.


What did the Grand Alliance propose as the new standard for SDTV and HDTV?

DVB created first the standard for DVB-S digital satellite TV, DVB-C digital cable TV and DVB-T digital terrestrial TV. These broadcasting systems can be used for both SDTV and HDTV. In the US the Grand Alliance proposed ATSC as the new standard for SDTV and HDTV. Both ATSC and DVB were based on the MPEG-2 standard, although DVB systems may also be used to transmit video using the newer and more efficient H.264/MPEG-4 AVC compression standards. Common for all DVB standards is the use of highly efficient modulation techniques for further reducing bandwidth, and foremost for reducing receiver-hardware and antenna requirements.


Which standard were ATSC and DVB based on?


Who created the standard for DVB-2, DVB-C, and DVB-T?


Who proposed ATSC as the new standard for SDTV and HDTV?


When did ITU-R start trying to work towards setting a single international HDTV standard?

In 1983, the International Telecommunication Union's radio telecommunications sector (ITU-R) set up a working party (IWP11/6) with the aim of setting a single international HDTV standard. One of the thornier issues concerned a suitable frame/field refresh rate, the world already having split into two camps, 25/50 Hz and 30/60 Hz, largely due to the differences in mains frequency. The IWP11/6 working party considered many views and throughout the 1980s served to encourage development in a number of video digital processing areas, not least conversion between the two main frame/field rates using motion vectors, which led to further developments in other areas. While a comprehensive HDTV standard was not in the end established, agreement on the aspect ratio was achieved.


What did ITU-R start trying to do in 1983?


What was one of the issues with setting a single HDTV standard?


What was used as a conversion between the two main frame/field rates?


How many frame/field rates were primarily being used in 1983?


What aspect ratio was agreed upon due to the influence of widescreen cinema?

Initially the existing 5:3 aspect ratio had been the main candidate but, due to the influence of widescreen cinema, the aspect ratio 16:9 (1.78) eventually emerged as being a reasonable compromise between 5:3 (1.67) and the common 1.85 widescreen cinema format. An aspect ratio of 16:9 was duly agreed upon at the first meeting of the IWP11/6 working party at the BBC's Research and Development establishment in Kingswood Warren. The resulting ITU-R Recommendation ITU-R BT.709-2 ("Rec. 709") includes the 16:9 aspect ratio, a specified colorimetry, and the scan modes 1080i (1,080 actively interlaced lines of resolution) and 1080p (1,080 progressively scanned lines). The British Freeview HD trials used MBAFF, which contains both progressive and interlaced content in the same encoding.


What was a leading factor in the 16:9 aspect ratio being chosen?


Which encoding contains both progressive and interlaced content?


Which aspect ratio was the early favorite?


What scan format is also included in MBAFF?

It also includes the alternative 1440×1152 HDMAC scan format. (According to some reports, a mooted 750-line (720p) format (720 progressively scanned lines) was viewed by some at the ITU as an enhanced television format rather than a true HDTV format, and so was not included, although 1920×1080i and 1280×720p systems for a range of frame and field rates were defined by several US SMPTE standards.)


What was viewed by some as enhanced television format and not true HDTV format?


A mooted 750-line was seen by some at the ITU as what?


What were 1920x1080i and 1280x720p defined by?


HDTV technology was introduced in the United States in the late 1980s and made official in 1993 by the Digital HDTV Grand Alliance, a group of television, electronic equipment, communications companies consisting of AT&T Bell Labs, General Instrument, Philips, Sarnoff, Thomson, Zenith and the Massachusetts Institute of Technology. Field testing of HDTV at 199 sites in the United States was completed August 14, 1994. The first public HDTV broadcast in the United States occurred on July 23, 1996 when the Raleigh, North Carolina television station WRAL-HD began broadcasting from the existing tower of WRAL-TV southeast of Raleigh, winning a race to be first with the HD Model Station in Washington, D.C., which began broadcasting July 31, 1996 with the callsign WHD-TV, based out of the facilities of NBC owned and operated station WRC-TV. The American Advanced Television Systems Committee (ATSC) HDTV system had its public launch on October 29, 1998, during the live coverage of astronaut John Glenn's return mission to space on board the Space Shuttle Discovery. The signal was transmitted coast-to-coast, and was seen by the public in science centers, and other public theaters specially equipped to receive and display the broadcast.


AT&T, Philips, Zenith, and MIT, among others, made up what group in the 90's?


When did the first public HDTV broadcast happen in the US?


When did the first HDTV transmissions happen in Europe?

The first HDTV transmissions in Europe, albeit not direct-to-home, began in 1990, when the Italian broadcaster RAI used the HD-MAC and MUSE HDTV technologies to broadcast the 1990 FIFA World Cup. The matches were shown in 8 cinemas in Italy and 2 in Spain. The connection with Spain was made via the Olympus satellite link from Rome to Barcelona and then with a fiber optic connection from Barcelona to Madrid. After some HDTV transmissions in Europe the standard was abandoned in the mid-1990s.


What event was the first HDTV broadcast in Europe?


When did Europe abandon standard transmission?


Where was the FIFA World Cup able to be watched in HDTV?


When did regular broadcasts start in Europe?

The first regular broadcasts started on January 1, 2004 when the Belgian company Euro1080 launched the HD1 channel with the traditional Vienna New Year's Concert. Test transmissions had been active since the IBC exhibition in September 2003, but the New Year's Day broadcast marked the official launch of the HD1 channel, and the official start of direct-to-home HDTV in Europe.


What event was first broadcasted on January 1, 2004?


The New Year's Day broadcast officially launched which channel?


When did test transmissions of HDTV begin in Europe?


Euro1080 was a division of what former company?

Euro1080, a division of the former and now bankrupt Belgian TV services company Alfacam, broadcast HDTV channels to break the pan-European stalemate of "no HD broadcasts mean no HD TVs bought means no HD broadcasts ..." and kick-start HDTV interest in Europe. The HD1 channel was initially free-to-air and mainly comprised sporting, dramatic, musical and other cultural events broadcast with a multi-lingual soundtrack on a rolling schedule of 4 or 5 hours per day.


What "chicken or the egg" stalemate prompted Euro1080 to broadcast HDTV channels?


What was Euro1080 hoping to kick-start by broadcasting HDTV channels?


How much did viewers have to pay for the HD1 channel?


What was on HD1 for 4 or 5 hours per day?


What format did the first European HDTV broadcast use?

These first European HDTV broadcasts used the 1080i format with MPEG-2 compression on a DVB-S signal from SES's Astra 1H satellite. Euro1080 transmissions later changed to MPEG-4/AVC compression on a DVB-S2 signal in line with subsequent broadcast channels in Europe.


What compression did the first European HDTV broadcast use?


What signal did the first European HDTV broadcast use?


What compression did Euro1080 later change to?


What signal did Euro1080 later change to?


According to the 2010 Satellite Monitor market survey, how many HD capable TV's were sold in Europe?

Despite delays in some countries, the number of European HD channels and viewers has risen steadily since the first HDTV broadcasts, with SES's annual Satellite Monitor market survey for 2010 reporting more than 200 commercial channels broadcasting in HD from Astra satellites, 185 million HD capable TVs sold in Europe (£60 million in 2010 alone), and 20 million households (27% of all European digital satellite TV homes) watching HD satellite broadcasts (16 million via Astra satellites).


According to the 2010 Satellite Monitor market survey, how many European households were watching HD broadcasts?


How many pounds were spent in Europe on HD capable TVs in 2010?


What percentage of European digital satellite TV homes were watching HD broadcasts in 2010?


The number of European HD channels and viewers has done what since the first HDTV broadcasts?


Which European country first deployed HD content using the new DVB-T2 standard?

In December 2009 the United Kingdom became the first European country to deploy high definition content using the new DVB-T2 transmission standard, as specified in the Digital TV Group (DTG) D-book, on digital terrestrial television.


When did the UK deploy HD content using the new DVB-T2 transmission standard?


What transmission standard did the UK start using in December 2009?


How many HD channels did the Freeview HD service contain as of December 2013?

The Freeview HD service currently contains 10 HD channels (as of December 2013[update]) and was rolled out region by region across the UK in accordance with the digital switchover process, finally being completed in October 2012. However, Freeview HD is not the first HDTV service over digital terrestrial television in Europe;


When was the digital switchover process completed in the UK?


Which service contains 10 HD channels and finished its roll out in October 2012?


How was the Freeview HD service rolled out in the UK?


If all three parameters are used, they are specified in the following form: [frame size][scanning system][frame or field rate] or [frame size]/[frame or field rate][scanning system].[citation needed] Often, frame size or frame rate can be dropped if its value is implied from context. In this case, the remaining numeric parameter is specified first, followed by the scanning system.


Which two parameters can be dropped if its value is implied from context?


When can the frame size or frame rate parameter specification be dropped?


When a parameter is dropped, the remaining numeric parameter is specified first, followed by what?


For example, 1920×1080p25 identifies progressive scanning format with 25 frames per second, each frame being 1,920 pixels wide and 1,080 pixels high. The 1080i25 or 1080i50 notation identifies interlaced scanning format with 25 frames (50 fields) per second, each frame being 1,920 pixels wide and 1,080 pixels high. The 1080i30 or 1080i60 notation identifies interlaced scanning format with 30 frames (60 fields) per second, each frame being 1,920 pixels wide and 1,080 pixels high. The 720p60 notation identifies progressive scanning format with 60 frames per second, each frame being 720 pixels high; 1,280 pixels horizontally are implied.


The 1920x1080p25 notion identifies progressive scanning format with how many frames per second?


The 1080i25 or 1080i50 notion identifies interlaced scanning format with how many frames per second?


The 1080i30 or 1080i60 notion identifies interlaced scanning format with how many frames per second?


The 720p60 notion identifies progressive scanning format with how many frames per second?


What three scanning rates do 50 Hz systems support?

50 Hz systems support three scanning rates: 50i, 25p and 50p. 60 Hz systems support a much wider set of frame rates: 59.94i, 60i, 23.976p, 24p, 29.97p, 30p, 59.94p and 60p. In the days of standard definition television, the fractional rates were often rounded up to whole numbers, e.g. 23.976p was often called 24p, or 59.94i was often called 60i. 60 Hz high definition television supports both fractional and slightly different integer rates, therefore strict usage of notation is required to avoid ambiguity. Nevertheless, 29.97i/59.94i is almost universally called 60i, likewise 23.976p is called 24p.


SD television fractional rates were often rounded to what?


Strict notation is required with HD fractional rates to avoid what?


What is usually dropped for the commercial naming of an HDTV product?

For the commercial naming of a product, the frame rate is often dropped and is implied from context (e.g., a 1080i television set). A frame rate can also be specified without a resolution. For example, 24p means 24 progressive scan frames per second, and 50i means 25 interlaced frames per second.


When naming a commercial HDTV product, a frame rate can be specified without what?


Is there a single standard for HDTV color support?

There is no single standard for HDTV color support. Colors are typically broadcast using a (10-bits per channel) YUV color space but, depending on the underlying image generating technologies of the receiver, are then subsequently converted to a RGB color space using standardized algorithms. When transmitted directly through the Internet, the colors are typically pre-converted to 8-bit RGB channels for additional storage savings with the assumption that it will only be viewed only on a (sRGB) computer screen. As an added benefit to the original broadcasters, the losses of the pre-conversion essentially make these files unsuitable for professional TV re-broadcasting.


Before being converted to RGB, colors are ususally broadcasted using what color space?


Colors are typically broadcast using YUV and then converted to what?


When transmitted over the internet, colors are typically to what?


What assumption is made with colors being transmitted over the internet?


At least how many times more linear resolution does HDTV have over SDTV?

At a minimum, HDTV has twice the linear resolution of standard-definition television (SDTV), thus showing greater detail than either analog television or regular DVD. The technical standards for broadcasting HDTV also handle the 16:9 aspect ratio images without using letterboxing or anamorphic stretching, thus increasing the effective image resolution.


HDTV increases the effective image resolution by not using what?


HDTV handles what aspect ratio without using letterboxing or anamorphic stretching?


If more bandwith is required than is available, a very high resolution source my not be able to transmitted without loss of what?

A very high resolution source may require more bandwidth than available in order to be transmitted without loss of fidelity. The lossy compression that is used in all digital HDTV storage and transmission systems will distort the received picture, when compared to the uncompressed source.


The compression used in all HDTV storage and transmission systems will do what if resolution is too high?


A very high resolution source may require more of what?


A broadcasts optimum format depends on what two things?

The optimum format for a broadcast depends upon the type of videographic recording medium used and the image's characteristics. For best fidelity to the source the transmitted field ratio, lines, and frame rate should match those of the source.


For best fidelity to the source, what three things should match the source?


For best fidelity to the source, the transmitted field ratio, lines, and frame rate should match what?


The type of videographic recording medium used and the image's characteristics determine what?


PAL, SECAM, and NTSC frame rates apply to what definition televisions?

PAL, SECAM and NTSC frame rates technically apply only to analogue standard definition television, not to digital or high definition broadcasts. However, with the roll out of digital broadcasting, and later HDTV broadcasting, countries retained their heritage systems. HDTV in former PAL and SECAM countries operates at a frame rate of 25/50 Hz, while HDTV in former NTSC countries operates at 30/60 Hz.


PAL, SECAM, and NTSC frame rates do not apply to what broadcasts?


In former PAL and SECAM countries, what frame rate does HDTV operate at?


In former NTSC countries, what frame rate does HDTV operate at?


At what rate is standard 35mm photographic film exposed and projected?

Standard 35mm photographic film used for cinema projection has a much higher image resolution than HDTV systems, and is exposed and projected at a rate of 24 frames per second (frame/s). To be shown on standard television, in PAL-system countries, cinema film is scanned at the TV rate of 25 frame/s, causing a speedup of 4.1 percent, which is generally considered acceptable. In NTSC-system countries, the TV scan rate of 30 frame/s would cause a perceptible speedup if the same were attempted, and the necessary correction is performed by a technique called 3:2 Pulldown: Over each successive pair of film frames, one is held for three video fields (1/20 of a second) and the next is held for two video fields (1/30 of a second), giving a total time for the two frames of 1/12 of a second and thus achieving the correct average film frame rate.


To be shown on SDTV in PAL-system countries, at what rate is cinema film scanned?


The technique in which with successive pair of film frames, one is held for three video fields, and the next is held for two, is called what?


The 3:2 Pulldown techniques gives what total time for two frames?


What is achieved by the 3:2 Pulldown technique producing a total time of 1/12 of a second for two frames?


What two formats are typically used to recorde non-cinematic HDTV video intended for broadcast?

Non-cinematic HDTV video recordings intended for broadcast are typically recorded either in 720p or 1080i format as determined by the broadcaster. 720p is commonly used for Internet distribution of high-definition video, because most computer monitors operate in progressive-scan mode. 720p also imposes less strenuous storage and decoding requirements compared to both 1080i and 1080p. 1080p/24, 1080i/30, 1080i/25, and 720p/30 is most often used on Blu-ray Disc.


Which format is typically used for internet distribution of HD video?


Most computer monitors operate in what mode?


1080i, 1080p, and 720p are often used on what kind of disc.


In the US, what kind of tuner is needed for residents to receive free, over the air programming?

In the US, residents in the line of sight of television station broadcast antennas can receive free, over the air programming with a television set with an ATSC tuner (most sets sold since 2009 have this). This is achieved with a TV aerial, just as it has been since the 1940s except now the major network signals are broadcast in high definition (ABC, Fox, and Ion Television broadcast at 720p resolution; CBS, My Network TV, NBC, PBS, and The CW at 1080i). As their digital signals more efficiently use the broadcast channel, many broadcasters are adding multiple channels to their signals. Laws about antennas were updated before the change to digital terrestrial broadcasts. These new laws prohibit home owners' associations and city government from banning the installation of antennas.


Laws regarding antennas were upated before what?


Who do these laws prohibit from banning the installation of antennas?


Laws about antennas keep home owners' associations and city government from banning what?


Most television sets sold since what year have an ATSC tuner?


HD content can be displayed by cable-ready TVs without using what?

Additionally, cable-ready TV sets can display HD content without using an external box. They have a QAM tuner built-in and/or a card slot for inserting a CableCARD.


Without using an external box, cable-ready TVs can display what?


What features allow the cable-ready TVs to display HD content without an external box?


What kind of built-in tuner will allow a cable-ready TV to display HD content without an external box?


What kind of card will allow a cable-ready TV to display HD content without an external box?


High-definition image sources include terrestrial broadcast, direct broadcast satellite, digital cable, IPTV (including GoogleTV Roku boxes and AppleTV or built into "Smart Televisions"), Blu-ray video disc (BD), and internet downloads.


Internet downloads, Blu-ray videos, and Apple TV are examples of what?


Terrestrial broadcast and direct broadcast satellite are examples of what?


Digital cable and Roku are examples of what?


Why does the PlayStation 3 have extensive HD compatibility?

Sony's PlayStation 3 has extensive HD compatibility because of its built in Blu-ray disc based player, so does Microsoft's Xbox 360 with the addition of Netflix and Windows Media Center HTPC streaming capabilities, and the Zune marketplace where users can rent or purchase digital HD content. Recently, Nintendo released a next generation high definition gaming platform, The Wii U, which includes TV remote control features in addition to IPTV streaming features like Netflix. The HD capabilities of the consoles has influenced some developers to port games from past consoles onto the PS3, Xbox 360 and Wii U, often with remastered or upscaled graphics.


In addition to having a Blu-ray player the Xbox 360 also features what?


What high definition gaming platform did Nintendo recently release?


The HD capabilities of modern gaming systems has inspired developers to do what?


Sky HD's set-top box, TiVo's Series 3, and Dish Network's VIP 622 are examples of what?

HDTV can be recorded to D-VHS (Digital-VHS or Data-VHS), W-VHS (analog only), to an HDTV-capable digital video recorder (for example DirecTV's high-definition Digital video recorder, Sky HD's set-top box, Dish Network's VIP 622 or VIP 722 high-definition Digital video recorder receivers, or TiVo's Series 3 or HD recorders), or an HDTV-ready HTPC. Some cable boxes are capable of receiving or recording two or more broadcasts at a time in HDTV format, and HDTV programming, some included in the monthly cable service subscription price, some for an additional fee, can be played back with the cable company's on-demand feature.


Some cable boxes are capable of doing what?


What restriction does W-VHS recordings have?


When was the Hauppauge 1212 Personal Video Recorder introduced?

The massive amount of data storage required to archive uncompressed streams meant that inexpensive uncompressed storage options were not available to the consumer. In 2008, the Hauppauge 1212 Personal Video Recorder was introduced. This device accepts HD content through component video inputs and stores the content in MPEG-2 format in a .ts file or in a Blu-ray compatible format .m2ts file on the hard drive or DVD burner of a computer connected to the PVR through a USB 2.0 interface. More recent systems are able to record a broadcast high definition program in its 'as broadcast' format or transcode to a format more compatible with Blu-ray.


How does the Personal Video Recorder store content?


Recent systems can record a broadcast HD program in what format?


What uncompressed storage option was introduced in 2008?


W-VHS recorders are capable of recording what kinds of signals?

Analog tape recorders with bandwidth capable of recording analog HD signals, such as W-VHS recorders, are no longer produced for the consumer market and are both expensive and scarce in the secondary market.


What kind of recorder is no longer produced for the consumer market?


In the secondary market, analog tape recorders are considered what?


Prior to 2004, what were US cable companies required to provide customers who rent HD set-top boxes?

In the United States, as part of the FCC's plug and play agreement, cable companies are required to provide customers who rent HD set-top boxes with a set-top box with "functional" FireWire (IEEE 1394) on request. None of the direct broadcast satellite providers have offered this feature on any of their supported boxes, but some cable TV companies have. As of July 2004[update], boxes are not included in the FCC mandate. This content is protected by encryption known as 5C. This encryption can prevent duplication of content or simply limit the number of copies permitted, thus effectively denying most if not all fair use of the content.


When were boxes with "functional" FireWire no longer included in the FCC mandate?


Content is now protected by what encryption?


In addition to being used to build things, what has wood been used for over thousands of years?

It has been used for thousands of years for both fuel and as a construction material. It is an organic material, a natural composite of cellulose fibers (which are strong in tension) embedded in a matrix of lignin which resists compression. Wood is sometimes defined as only the secondary xylem in the stems of trees, or it is defined more broadly to include the same type of tissue elsewhere such as in the roots of trees or shrubs.[citation needed] In a living tree it performs a support function, enabling woody plants to grow large or to stand up by themselves. It also conveys water and nutrients between the leaves, other growing tissues, and the roots. Wood may also refer to other plant materials with comparable properties, and to material engineered from wood, or wood chips or fiber.


What kind of strong fibers are part of the composite of wood?


What one word describes the function wood provides to a tree or plant?


What does wood convey to leaves, roots, and other tissues of a woody plant in addition to water?


How many cubic meters of growing stock forest are there on the planet?

The Earth contains about 434 billion cubic meters of growing stock forest, 47% of which is commercial. As an abundant, carbon-neutral renewable resource, woody materials have been of intense interest as a source of renewable energy. In 1991, approximately 3.5 cubic kilometers of wood were harvested. Dominant uses were for furniture and building construction.


What percentage of the Earth's stock forest is commercial?


In addition to buildings, what is wood often used to make?


About how many cubic kilometers of the vast stock forest's wood were harvested in 1991?


In addition to being carbon neutral, what other adjective describes wood that makes it compelling as a renewable energy source?


What year were the earliest plants that grew wood discovered?

A 2011 discovery in the Canadian province of New Brunswick uncovered the earliest known plants to have grown wood, approximately 395 to 400 million years ago. Wood can be dated by carbon dating and in some species by dendrochronology to make inferences about when a wooden object was created.


In which Canadian province were the oldest woody plants found?


If dendrochronology can't be used, what method would scientists employ to date wood?


How many millions of years old were the plants that were discovered in New Brunswick?


What has been the primary purpose of wood for millennia other than fuel?

People have used wood for millennia for many purposes, primarily as a fuel or as a construction material for making houses, tools, weapons, furniture, packaging, artworks, and paper. The year-to-year variation in tree-ring widths and isotopic abundances gives clues to the prevailing climate at that time.


What is often made of wood that provides shelter to people?


For clues about the climate of a place, we can look at variation in isotopic abundances or what other thing?


What could be made out of wood that could be used to fight off attackers?


What category of items often constructed from wood does a chair belong to?


Wood, in the strict sense, is yielded by trees, which increase in diameter by the formation, between the existing wood and the inner bark, of new woody layers which envelop the entire stem, living branches, and roots. This process is known as secondary growth; it is the result of cell division in the vascular cambium, a lateral meristem, and subsequent expansion of the new cells. Where there are clear seasons, growth can occur in a discrete annual or seasonal pattern, leading to growth rings; these can usually be most clearly seen on the end of a log, but are also visible on the other surfaces. If these seasons are annual these growth rings are referred to as annual rings. Where there is no seasonal difference growth rings are likely to be indistinct or absent.


What forms in a tree to increase its diameter?


What is the process of trees growing out to get bigger around called?


What do many places have four of that would cause growth rings in a tree?


If a place has annual seasons, what are the growth rings on the trees there called?


If a growth ring has differences over one season, would the part nearest the tree's center be narrower or wider?

If there are differences within a growth ring, then the part of a growth ring nearest the center of the tree, and formed early in the growing season when growth is rapid, is usually composed of wider elements. It is usually lighter in color than that near the outer portion of the ring, and is known as earlywood or springwood. The outer portion formed later in the season is then known as the latewood or summerwood. However, there are major differences, depending on the kind of wood (see below).


What name, besides springwood, is used for the part of a growth ring formed in the beginning of the growing season?


If the opposite of springwood is summerwood, what's the opposite of earlywood?


Is earlywood usually lighter or darker than the part of the growth ring that forms later in the season?


Is summerwood the inner or outer portion of a growth ring?


What is the sort of circular imperfection in a piece of wood called?

A knot is a particular type of imperfection in a piece of wood; it will affect the technical properties of the wood, usually reducing the local strength and increasing the tendency for splitting along the wood grain, but may be exploited for visual effect. In a longitudinally sawn plank, a knot will appear as a roughly circular "solid" (usually darker) piece of wood around which the grain of the rest of the wood "flows" (parts and rejoins). Within a knot, the direction of the wood (grain direction) is up to 90 degrees different from the grain direction of the regular wood.


What property of wood does a knot usually reduce in the wood around it?


In what direction is wood often sawn so that a knot appears as a solid circle that the grain flows around?


Are knots usually lighter or darker than the surrounding wood?


The direction of grain in a knot can differ by as much as how many degrees from the regular wood?


Other than the base of a side branch, what tree feature causes a knot?

In the tree a knot is either the base of a side branch or a dormant bud. A knot (when the base of a side branch) is conical in shape (hence the roughly circular cross-section) with the inner tip at the point in stem diameter at which the plant's vascular cambium was located when the branch formed as a bud.


What shape is the knot formed by a side branch's base?


What measurement of a stem determines a knot's inner tip placement?


Because a knot's shape is conical, what shape does a cross-section of it have?


What will the lower limbs of a tree usually do during development?

During the development of a tree, the lower limbs often die, but may remain attached for a time, sometimes years. Subsequent layers of growth of the attaching stem are no longer intimately joined with the dead limb, but are grown around it. Hence, dead branches produce knots which are not attached, and likely to drop out after the tree has been sawn into boards.


For what length of time can a dead lower limb stay attached to a tree?


Rather than being joined to the limb that died, where do subsequent layers grow?


Are the knots that dead tree limbs form attached or not attached?


A detached knot will probably drop out of the wood when someone saws it into what?


What's the process in which knots are classified called?

In grading lumber and structural timber, knots are classified according to their form, size, soundness, and the firmness with which they are held in place. This firmness is affected by, among other factors, the length of time for which the branch was dead while the attaching stem continued to grow.


Along with firmness, soundness, and form, what property of a knot is classified?


What property of knots does the amount of time a branch stayed on a tree while the stem kept growing affect?


What is wood's breaking strength susceptible to?

Knots do not necessarily influence the stiffness of structural timber, this will depend on the size and location. Stiffness and elastic strength are more dependent upon the sound wood than upon localized defects. The breaking strength is very susceptible to defects. Sound knots do not weaken wood when subject to compression parallel to the grain.


Depending on the placement and size of a knot, what property of structural timber can be affected?


What do stiffness and elastic strength depend on more than defects?


What direction of compression in relation to its grain won't weaken wood with sound knots in it?


What positive visual component can knots sometimes add to decorative pieces?

In some decorative applications, wood with knots may be desirable to add visual interest. In applications where wood is painted, such as skirting boards, fascia boards, door frames and furniture, resins present in the timber may continue to 'bleed' through to the surface of a knot for months or even years after manufacture and show as a yellow or brownish stain. A knot primer paint or solution, correctly applied during preparation, may do much to reduce this problem but it is difficult to control completely, especially when using mass-produced kiln-dried timber stocks.


What term is used to describe what knots can do to affect the finish of things made from wood even when they've been painted?


The stain from a knot bleeding is usually brownish or what other color?


In what stage of processing does knot primer need to be applied for maximum effectiveness?


Heartwood (or duramen) is wood that as a result of a naturally occurring chemical transformation has become more resistant to decay. Heartwood formation occurs spontaneously (it is a genetically programmed process). Once heartwood formation is complete, the heartwood is dead. Some uncertainty still exists as to whether heartwood is truly dead, as it can still chemically react to decay organisms, but only once.


What is heartwood naturally resistant to?


How does heartwood formation occur due to its being genetically programmed?


What adjective describes fully formed heartwood?


Despite being considered dead, what can heartwood have one chemical reaction to?


In what part of a tree's cross-section is heartwood visible?

Heartwood is often visually distinct from the living sapwood, and can be distinguished in a cross-section where the boundary will tend to follow the growth rings. For example, it is sometimes much darker. However, other processes such as decay or insect invasion can also discolor wood, even in woody plants that do not form heartwood, which may lead to confusion.


What simple color distinction can heartwood have that makes it stand out from living wood in a tree?


Along with insect infestation, what process can discolor wood and make it look like heartwood?


What kind of plants never form heartwood?


What is the living wood in a tree called?


What term is interchangeable with "sapwood"?

Sapwood (or alburnum) is the younger, outermost wood; in the growing tree it is living wood, and its principal functions are to conduct water from the roots to the leaves and to store up and give back according to the season the reserves prepared in the leaves. However, by the time they become competent to conduct water, all xylem tracheids and vessels have lost their cytoplasm and the cells are therefore functionally dead. All wood in a tree is first formed as sapwood. The more leaves a tree bears and the more vigorous its growth, the larger the volume of sapwood required. Hence trees making rapid growth in the open have thicker sapwood for their size than trees of the same species growing in dense forests. Sometimes trees (of species that do form heartwood) grown in the open may become of considerable size, 30 cm or more in diameter, before any heartwood begins to form, for example, in second-growth hickory, or open-grown pines.


Is sapwood the younger or older wood in a tree?


What essential liquid is the sapwood tasked with carrying around a tree?


How much of the wood in a tree is sapwood at some point in its life?


Does a tree growing quickly out in the open have thinner or thicker sapwood for its size than the same kind of tree in a dense forest?


If a tree starts forming heartwood right away, will its sapwood layer be thin or thick?

The term heartwood derives solely from its position and not from any vital importance to the tree. This is evidenced by the fact that a tree can thrive with its heart completely decayed. Some species begin to form heartwood very early in life, so having only a thin layer of live sapwood, while in others the change comes slowly. Thin sapwood is characteristic of such species as chestnut, black locust, mulberry, osage-orange, and sassafras, while in maple, ash, hickory, hackberry, beech, and pine, thick sapwood is the rule. Others never form heartwood.


What property of heartwood that has nothing to do with how important it is to trees got it its name?


Does a beech tree usually have thin or thick sapwood?


Does a sassafras tree typically have a thin or thick sapwood layer?


Would a thin or a thick sapwood layer be found in a pine tree?


What part of a tree is the cross-sectional area of the sapwood approximately proportional to?

No definite relation exists between the annual rings of growth and the amount of sapwood. Within the same species the cross-sectional area of the sapwood is very roughly proportional to the size of the crown of the tree. If the rings are narrow, more of them are required than where they are wide. As the tree gets larger, the sapwood must necessarily become thinner or increase materially in volume. Sapwood is thicker in the upper portion of the trunk of a tree than near the base, because the age and the diameter of the upper sections are less.


Are more rings necessary if they're narrow or wide?


As a tree grows bigger, if the sapwood layer doesn't increase in volume, what will it become?


In what part of the tree trunk is the sapwood layer thinnest?


Along with the smaller diameter of the upper trunk, what factor leads to thinner sapwood higher up a tree?


What usually covers the whole trunk of a very young tree?

When a tree is very young it is covered with limbs almost, if not entirely, to the ground, but as it grows older some or all of them will eventually die and are either broken off or fall off. Subsequent growth of wood may completely conceal the stubs which will however remain as knots. No matter how smooth and clear a log is on the outside, it is more or less knotty near the middle. Consequently, the sapwood of an old tree, and particularly of a forest-grown tree, will be freer from knots than the inner heartwood. Since in most uses of wood, knots are defects that weaken the timber and interfere with its ease of working and other properties, it follows that a given piece of sapwood, because of its position in the tree, may well be stronger than a piece of heartwood from the same tree.


What evidence of the stubs of the limbs a tree loses can always be seen in the wood?


In a very old tree, are you more likely to find a lot of knots in the heartwood or the sapwood?


What hides the stubs of a tree's lost limbs from being visible later in its life?


Since knots are defects that weaken lumber, would the heartwood or the sapwood from the same tree be stronger?


What do broken limbs and deep wounds open a door for in a tree?

It is remarkable that the inner heartwood of old trees remains as sound as it usually does, since in many cases it is hundreds, and in a few instances thousands, of years old. Every broken limb or root, or deep wound from fire, insects, or falling timber, may afford an entrance for decay, which, once started, may penetrate to all parts of the trunk. The larvae of many insects bore into the trees and their tunnels remain indefinitely as sources of weakness. Whatever advantages, however, that sapwood may have in this connection are due solely to its relative age and position.


Decay can spread to all of what part of a tree?


What growth stage of insects bore holes into trees?


What part of a tree often stays impressively sound even when hundreds or thousands of years old?


What evidence do some insect larvae leave in a tree forever?


In what stage of its life does a tree usually grow the fastest?

If a tree grows all its life in the open and the conditions of soil and site remain unchanged, it will make its most rapid growth in youth, and gradually decline. The annual rings of growth are for many years quite wide, but later they become narrower and narrower. Since each succeeding ring is laid down on the outside of the wood previously formed, it follows that unless a tree materially increases its production of wood from year to year, the rings must necessarily become thinner as the trunk gets wider. As a tree reaches maturity its crown becomes more open and the annual wood production is lessened, thereby reducing still more the width of the growth rings. In the case of forest-grown trees so much depends upon the competition of the trees in their struggle for light and nourishment that periods of rapid and slow growth may alternate. Some trees, such as southern oaks, maintain the same width of ring for hundreds of years. Upon the whole, however, as a tree gets larger in diameter the width of the growth rings decreases.


As a tree ages, do its growth rings usually get wider or narrower?


What part of a tree opens and spreads out more as it matures?


Is wood production of a tree lessened or increased as it ages?


Along with nutrients, what do trees growing in forests have to compete for?


When a big tree is cut up, will the pieces of wood differ or all be the same?

Different pieces of wood cut from a large tree may differ decidedly, particularly if the tree is big and mature. In some trees, the wood laid on late in the life of a tree is softer, lighter, weaker, and more even-textured than that produced earlier, but in other trees, the reverse applies. This may or may not correspond to heartwood and sapwood. In a large log the sapwood, because of the time in the life of the tree when it was grown, may be inferior in hardness, strength, and toughness to equally sound heartwood from the same log. In a smaller tree, the reverse may be true.


In a large log, will the heartwood or sapwood usually be stronger and tougher?


If you need really hard, strong wood from a small tree, would it likely be better to use the heartwood or sapwood?


Besides big trees, what trees are more likely to have a range of different kinds of wood?


When trees have a visible difference in color between sapwood and heartwood, which is darker?

In species which show a distinct difference between heartwood and sapwood the natural color of heartwood is usually darker than that of the sapwood, and very frequently the contrast is conspicuous (see section of yew log above). This is produced by deposits in the heartwood of chemical substances, so that a dramatic color difference does not mean a dramatic difference in the mechanical properties of heartwood and sapwood, although there may be a dramatic chemical difference.


What is deposited naturally in heartwood that changes its color?


Is the color difference between heartwood and sapwood usually very subtle or conspicuous?


What type of properties of heartwood and sapwood is often the same even if their colors are very different?


Although heartwood and sapwood might be similar mechanically, if their colors are very different, what other type of difference would they have?


What type of tree has resin that makes it stronger when it dries?

Some experiments on very resinous Longleaf Pine specimens indicate an increase in strength, due to the resin which increases the strength when dry. Such resin-saturated heartwood is called "fat lighter". Structures built of fat lighter are almost impervious to rot and termites; however they are very flammable. Stumps of old longleaf pines are often dug, split into small pieces and sold as kindling for fires. Stumps thus dug may actually remain a century or more since being cut. Spruce impregnated with crude resin and dried is also greatly increased in strength thereby.


What's the funny name for resin-saturated heartwood?


What is fat lighter practically impervious to in addition to termites?


If spruce is shot full of crude resin and dried, which of its properties is increased?


Since it's highly flammable, what do people often use little pieces of longleaf pine tree stumps for?


Which of the wood in a growth ring is usually darker?

Since the latewood of a growth ring is usually darker in color than the earlywood, this fact may be used in judging the density, and therefore the hardness and strength of the material. This is particularly the case with coniferous woods. In ring-porous woods the vessels of the early wood not infrequently appear on a finished surface as darker than the denser latewood, though on cross sections of heartwood the reverse is commonly true. Except in the manner just stated the color of wood is no indication of strength.


Which property of a tree's wood that gives clues about its strength and hardness can be judged by it's color?


What category of trees show this difference greatly?


What type of woods might sometimes appear to have darker earlywood on a finished surface?


With the exception of earlywood/latewood difference in some types of trees, how much of an indication of strength is a wood's color?


What condition does an abnormal color usually indicate in wood?

Abnormal discoloration of wood often denotes a diseased condition, indicating unsoundness. The black check in western hemlock is the result of insect attacks. The reddish-brown streaks so common in hickory and certain other woods are mostly the result of injury by birds. The discoloration is merely an indication of an injury, and in all probability does not of itself affect the properties of the wood. Certain rot-producing fungi impart to wood characteristic colors which thus become symptomatic of weakness; however an attractive effect known as spalting produced by this process is often considered a desirable characteristic. Ordinary sap-staining is due to fungal growth, but does not necessarily produce a weakening effect.


What other property can you assume of wood that is diseased?


What causes the black checked pattern in the wood of western hemlocks?


What animals cause the reddish-brown streaks of color in hickory wood?


What's the name for the pretty coloring effect caused in some wood by rot-producing fungi?


What does wood retain in its cell walls despite being air-dried?

In heartwood it occurs only in the first and last forms. Wood that is thoroughly air-dried retains 8–16% of the water in the cell walls, and none, or practically none, in the other forms. Even oven-dried wood retains a small percentage of moisture, but for all except chemical purposes, may be considered absolutely dry.


Air-dried wood keeps up to what percentage of the water in its cell walls?


What kind of dried wood retains a small quantity of water but is considered absolutely dry?


Often the water in wood makes it more pliable and what else?

The general effect of the water content upon the wood substance is to render it softer and more pliable. A similar effect of common observation is in the softening action of water on rawhide, paper, or cloth. Within certain limits, the greater the water content, the greater its softening effect.


What material sometimes used for dog chews reacts similarly to wood because of its water content?


What material we use to write or print on, like wood, becomes softer and more pliable when wet?


When water content increases within certain limits in wood, does is have a less or greater softening effect?


What type of action does water create in cloth?


What will drying often increase in wood?

Drying produces a decided increase in the strength of wood, particularly in small specimens. An extreme example is the case of a completely dry spruce block 5 cm in section, which will sustain a permanent load four times as great as a green (undried) block of the same size will.


What color is also used interchangeably with "undried" for wood?


What type of wood can hold four times as much of a load when dried?


What type of "ultimate" strength is one of the two types increased the most by drying wood?

The greatest strength increase due to drying is in the ultimate crushing strength, and strength at elastic limit in endwise compression; these are followed by the modulus of rupture, and stress at elastic limit in cross-bending, while the modulus of elasticity is least affected.


What property of wood is least affected by drying?


Is strength at elastic limit in endwise compression or stress at elastic limit in cross-bending increased more by drying wood?


Is the strength of the modulus of rupture or elasticity increased more when wood is dried?


Along with hygroscopic, cellular, and anisotropic, how is the material of wood described?

Wood is a heterogeneous, hygroscopic, cellular and anisotropic material. It consists of cells, and the cell walls are composed of micro-fibrils of cellulose (40% – 50%) and hemicellulose (15% – 25%) impregnated with lignin (15% – 30%).


What part of wood's cells are composed of cellulose and hemicellulose?


What makes up 40-50% of the cell walls in wood?


What substance is hemicellulose impregnated with?


What type of cells makes up most wood cells in coniferous trees?

In coniferous or softwood species the wood cells are mostly of one kind, tracheids, and as a result the material is much more uniform in structure than that of most hardwoods. There are no vessels ("pores") in coniferous wood such as one sees so prominently in oak and ash, for example.


Are hardwood or softwood species more uniform in structure?


What are the visible vessels in hardwoods commonly called?


What hardwood that starts with the letter "O" would have pores?


Besides oak, what's an example of a hardwood with prominent pores?


Is the structure of hardwood simple or complex?

The structure of hardwoods is more complex. The water conducting capability is mostly taken care of by vessels: in some cases (oak, chestnut, ash) these are quite large and distinct, in others (buckeye, poplar, willow) too small to be seen without a hand lens. In discussing such woods it is customary to divide them into two large classes, ring-porous and diffuse-porous.


What handles most of the water conduction in hardwoods?


Are the vessels in chestnut wood large or small?


In wood from a willow tree, what would you need to use to see the tiny vessels?


Besides ring-porous, what's the other class hardwoods are often divided into?


What species of hardwood are hickory and mulberry trees?

In ring-porous species, such as ash, black locust, catalpa, chestnut, elm, hickory, mulberry, and oak, the larger vessels or pores (as cross sections of vessels are called) are localised in the part of the growth ring formed in spring, thus forming a region of more or less open and porous tissue. The rest of the ring, produced in summer, is made up of smaller vessels and a much greater proportion of wood fibers. These fibers are the elements which give strength and toughness to wood, while the vessels are a source of weakness.[citation needed]


In what season do the growth-rings of ring-porous species form with larger vessels localized?


In what season does the part of the growth-ring with smaller vessels form in ring-porous species?


What fibers does the summer's section of growth-ring have more of?


Along with strength, what property do wood fibers lend to wood?


What kind of woods have pores that are uniformly sized?

In diffuse-porous woods the pores are evenly sized so that the water conducting capability is scattered throughout the growth ring instead of being collected in a band or row. Examples of this kind of wood are alder, basswood,[citation needed] birch, buckeye, maple, willow,and the Populus species such as aspen, cottonwood and poplar. Some species, such as walnut and cherry, are on the border between the two classes, forming an intermediate group.[citation needed]


What species do aspen, cottonwood, and poplar trees belong to?


With walnut, what's another tree in the intermediate group?


What capability is spread through the growth ring in ring-porous species?


Is maple wood diffuse-porous or ring-porous?


What kind of softwoods often have significant differences in their earlywood and latewood?

In temperate softwoods there often is a marked difference between latewood and earlywood. The latewood will be denser than that formed early in the season. When examined under a microscope the cells of dense latewood are seen to be very thick-walled and with very small cell cavities, while those formed first in the season have thin walls and large cell cavities. The strength is in the walls, not the cavities. Hence the greater the proportion of latewood the greater the density and strength. In choosing a piece of pine where strength or stiffness is the important consideration, the principal thing to observe is the comparative amounts of earlywood and latewood. The width of ring is not nearly so important as the proportion and nature of the latewood in the ring.


Is latewood denser or less dense than earlywood?


Does strength come from the walls or cavities of wood cells?


Are the cell walls of earlywood thick or thin?


What general size are the cavities in the cells of very dense latewood?


Comparing a heavy and a lightweight piece of wood from a pine, which would have a greater proportion of latewood?

If a heavy piece of pine is compared with a lightweight piece it will be seen at once that the heavier one contains a larger proportion of latewood than the other, and is therefore showing more clearly demarcated growth rings. In white pines there is not much contrast between the different parts of the ring, and as a result the wood is very uniform in texture and is easy to work. In hard pines, on the other hand, the latewood is very dense and is deep-colored, presenting a very decided contrast to the soft, straw-colored earlywood.


What feature of a piece of pine with more latewood would be more clear and pronounced?


What type of tree has very little contrast between parts of its growth rings?


Is white pine easy or difficult to work with because of its texture?


What kind of pines have very deep, darkly colored hardwood that stands out against the light earlywood?


Having a high proportion of latewood isn't all that matters; what else is important?

It is not only the proportion of latewood, but also its quality, that counts. In specimens that show a very large proportion of latewood it may be noticeably more porous and weigh considerably less than the latewood in pieces that contain but little. One can judge comparative density, and therefore to some extent strength, by visual inspection.


What can we judge in wood just by looking at it?


What property of wood could we project some indication of by looking at its density?


What could we call some specimens with a high proportion of latewood that explains why they weigh less than specimens with much less latewood?


What facet of wood is affected to some degree by the place where the tree grows?

No satisfactory explanation can as yet be given for the exact mechanisms determining the formation of earlywood and latewood. Several factors may be involved. In conifers, at least, rate of growth alone does not determine the proportion of the two portions of the ring, for in some cases the wood of slow growth is very hard and heavy, while in others the opposite is true. The quality of the site where the tree grows undoubtedly affects the character of the wood formed, though it is not possible to formulate a rule governing it. In general, however, it may be said that where strength or ease of working is essential, woods of moderate to slow growth should be chosen.


If you want wood that's easy to work with, what kind of growth would you want the tree to have?


What species of tree can be said to growth ring proportions that aren't determined just by their rate of growth?


What counterpart of earlywood are scientists still trying to explain the formation of?


While there is some relationship between where and how a tree grows, what can't anyone formulate to govern it?


What kind of woods always have very clearly marked seasonal growth?

In ring-porous woods each season's growth is always well defined, because the large pores formed early in the season abut on the denser tissue of the year before.


What size pores form early in ring-porous woods' growing season?


When does the denser tissue the new pores abut come from?


Ring-porous hardwoods have a clear relationship between their properties and what other factor?

In the case of the ring-porous hardwoods there seems to exist a pretty definite relation between the rate of growth of timber and its properties. This may be briefly summed up in the general statement that the more rapid the growth or the wider the rings of growth, the heavier, harder, stronger, and stiffer the wood. This, it must be remembered, applies only to ring-porous woods such as oak, ash, hickory, and others of the same group, and is, of course, subject to some exceptions and limitations.


Is harder, heavier wood indicated by narrower or wider growth rings?


What kind of wood with a name that starts with "H" is a ring-porous hardwood?


If the growth rings are wider, was the growth of the tree slower or more rapid?


What is the only kind of wood that will definitely be harder and stronger when it grows faster?


Which specific type of wood within ring-porous woods have more fibers to make it strong?

In ring-porous woods of good growth it is usually the latewood in which the thick-walled, strength-giving fibers are most abundant. As the breadth of ring diminishes, this latewood is reduced so that very slow growth produces comparatively light, porous wood composed of thin-walled vessels and wood parenchyma. In good oak these large vessels of the earlywood occupy from 6 to 10 percent of the volume of the log, while in inferior material they may make up 25% or more. The latewood of good oak is dark colored and firm, and consists mostly of thick-walled fibers which form one-half or more of the wood. In inferior oak, this latewood is much reduced both in quantity and quality. Such variation is very largely the result of rate of growth.


When there is less latewood, what is diminishing?


Does slow or rapid growth make relatively porous, light wood?


What kind of oak has just 6-10% volume of large vessels in the log?


What kind of fibers are in the latewood of good oak, making it very firm?


What term is sometimes used for wood with wide rings?

Wide-ringed wood is often called "second-growth", because the growth of the young timber in open stands after the old trees have been removed is more rapid than in trees in a closed forest, and in the manufacture of articles where strength is an important consideration such "second-growth" hardwood material is preferred. This is particularly the case in the choice of hickory for handles and spokes. Here not only strength, but toughness and resilience are important. The results of a series of tests on hickory by the U.S. Forest Service show that:


Do young trees grow more quickly in open stands or in a closed forest?


What property is important to manufacturers who use "second-growth" hardwood?


What specific kind of "second-growth" hardwood is often used to make handles and spokes?


What organization tested hickory to find out about its properties?


What kind of wood often has ring divisions that can't even be seen by looking at it?

In the diffuse-porous woods, the demarcation between rings is not always so clear and in some cases is almost (if not entirely) invisible to the unaided eye. Conversely, when there is a clear demarcation there may not be a noticeable difference in structure within the growth ring.


In diffuse-porous woods, if the demarcation between rings is obvious, what type of difference within the ring might not be?


What adjective describes how our eyes function without a tool like a microscope to help?


What kind of wood has all similarly sized vessels?

In diffuse-porous woods, as has been stated, the vessels or pores are even-sized, so that the water conducting capability is scattered throughout the ring instead of collected in the earlywood. The effect of rate of growth is, therefore, not the same as in the ring-porous woods, approaching more nearly the conditions in the conifers. In general it may be stated that such woods of medium growth afford stronger material than when very rapidly or very slowly grown. In many uses of wood, total strength is not the main consideration. If ease of working is prized, wood should be chosen with regard to its uniformity of texture and straightness of grain, which will in most cases occur when there is little contrast between the latewood of one season's growth and the earlywood of the next.


What rate of growth in a tree will make the wood from it stronger than trees that grow very slowly or very quickly?


The capability of diffuse-porous woods to carry what substance is spread out in the growth ring?


What division of trees are diffuse-porous woods more similar in growth rate to than ring-porous woods?


Does uniformity of the texture and grain of wood usually result from much or little contrast between earlywood and latewood?


What's another term used for "conifer" wood?

Structural material that resembles ordinary, "dicot" or conifer wood in its gross handling characteristics is produced by a number of monocot plants, and these also are colloquially called wood. Of these, bamboo, botanically a member of the grass family, has considerable economic importance, larger culms being widely used as a building and construction material in their own right and, these days, in the manufacture of engineered flooring, panels and veneer. Another major plant group that produce material that often is called wood are the palms. Of much less importance are plants such as Pandanus, Dracaena and Cordyline. With all this material, the structure and composition of the structural material is quite different from ordinary wood.


What type of plants produce material that is referred to as "wood" even though it is technically not?


What monocot plant produces "wood" by the same name that's often used for flooring and veneer?


While we call bamboo "wood," what botanical family does it belong to?


Along with bamboo, what's the other monocot that's a major source of so-called "wood"?


Which property of wood reveals the most about its quality?

The single most revealing property of wood as an indicator of wood quality is specific gravity (Timell 1986), as both pulp yield and lumber strength are determined by it. Specific gravity is the ratio of the mass of a substance to the mass of an equal volume of water; density is the ratio of a mass of a quantity of a substance to the volume of that quantity and is expressed in mass per unit substance, e.g., grams per millilitre (g/cm3 or g/ml). The terms are essentially equivalent as long as the metric system is used. Upon drying, wood shrinks and its density increases. Minimum values are associated with green (water-saturated) wood and are referred to as basic specific gravity (Timell 1986).


In addition to lumber strength, what important indicator of wood's quality can be determined using specific gravity?


What measurement is expressed in mass per unit substance?


When wood dries and shrinks, what happens to its density?


When wood is described as "green," what does "green" mean?


Along with growth, what kind of factors determine the density of wood?

Wood density is determined by multiple growth and physiological factors compounded into “one fairly easily measured wood characteristic” (Elliott 1970).


Into how many characteristics are the factors of wood combined?


What author called wood's density "fairly easily measured"?


What should be anticipated because of the many factors that influence wood's density?

Age, diameter, height, radial growth, geographical location, site and growing conditions, silvicultural treatment, and seed source, all to some degree influence wood density. Variation is to be expected. Within an individual tree, the variation in wood density is often as great as or even greater than that between different trees (Timell 1986). Variation of specific gravity within the bole of a tree can occur in either the horizontal or vertical direction. :)


What specific type of growth has an effect on the density of wood?


Which part of a tree can have vertical or horizontal variation in its specific gravity?


Variation in what measurement is sometimes greater within one tree than from one tree to another?


What tiny object's source plays a role in determining wood density?


What term do we use for the wood that comes from pine trees?

It is common to classify wood as either softwood or hardwood. The wood from conifers (e.g. pine) is called softwood, and the wood from dicotyledons (usually broad-leaved trees, e.g. oak) is called hardwood. These names are a bit misleading, as hardwoods are not necessarily hard, and softwoods are not necessarily soft. The well-known balsa (a hardwood) is actually softer than any commercial softwood. Conversely, some softwoods (e.g. yew) are harder than many hardwoods.


What kind of wood does an oak tree have?


What's an example of a softwood that isn't "soft," and is actually harder than a lot of hardwoods?


What's the scientific name for trees like the oak with broad leaves?


What kind of relationship exists between a tree's properties and its wood's properties?

There is a strong relationship between the properties of wood and the properties of the particular tree that yielded it. The density of wood varies with species. The density of a wood correlates with its strength (mechanical properties). For example, mahogany is a medium-dense hardwood that is excellent for fine furniture crafting, whereas balsa is light, making it useful for model building. One of the densest woods is black ironwood.


What property of wood varies according to species?


What property of wood has a correlation to its density?


What hobby is balsa wood often used for?


What approximate percentage of carbon does wood have?

The chemical composition of wood varies from species to species, but is approximately 50% carbon, 42% oxygen, 6% hydrogen, 1% nitrogen, and 1% other elements (mainly calcium, potassium, sodium, magnesium, iron, and manganese) by weight. Wood also contains sulfur, chlorine, silicon, phosphorus, and other elements in small quantity.


What element makes up about 6% of the chemical composition of wood?


About what percentage of wood is composed of nitrogen?


Which element in wood composes about 42% of its weight?


What element joins potassium, calcium, manganese, iron, and sodium to make a combined 1% of the chemical composition of wood?


How many main components make up wood, not counting water?

Aside from water, wood has three main components. Cellulose, a crystalline polymer derived from glucose, constitutes about 41–43%. Next in abundance is hemicellulose, which is around 20% in deciduous trees but near 30% in conifers. It is mainly five-carbon sugars that are linked in an irregular manner, in contrast to the cellulose. Lignin is the third component at around 27% in coniferous wood vs. 23% in deciduous trees. Lignin confers the hydrophobic properties reflecting the fact that it is based on aromatic rings. These three components are interwoven, and direct covalent linkages exist between the lignin and the hemicellulose. A major focus of the paper industry is the separation of the lignin from the cellulose, from which paper is made.


What's the name for the crystalline polymer derived from glucose?


After cellulose, what component is most plentiful in wood?


What kind of trees have about 30% hemicellulose?


Which of the three main components of wood is used to manufacture paper?


What component of wood determines whether it is hardwood or softwood?

In chemical terms, the difference between hardwood and softwood is reflected in the composition of the constituent lignin. Hardwood lignin is primarily derived from sinapyl alcohol and coniferyl alcohol. Softwood lignin is mainly derived from coniferyl alcohol.


Which wood has lignin that comes primarily from one type of alcohol?


Which type of alcohol mainly becomes softwood lignin?


In addition to coniferyl alcohol, what other alcohol is in hardwood lignin?


Which kind of wood contains lignin derived from two main alcohol sources?


What's the name for the low molecular weight organic compounds in wood?

Aside from the lignocellulose, wood consists of a variety of low molecular weight organic compounds, called extractives. The wood extractives are fatty acids, resin acids, waxes and terpenes. For example, rosin is exuded by conifers as protection from insects. The extraction of these organic materials from wood provides tall oil, turpentine, and rosin.


Along with fatty acids, what kind of acids are in the extractives in wood?


Wood extractives include resin and fatty acids, terpenes, and what other component?


What do conifers use rosin to protect themselves from?


Along with tall oil and rosin, what commercial product do we get from wood's extractives?


Wood has a long history of being used as fuel, which continues to this day, mostly in rural areas of the world. Hardwood is preferred over softwood because it creates less smoke and burns longer. Adding a woodstove or fireplace to a home is often felt to add ambiance and warmth.


What type of wood burns quickly and makes more smoke than hardwood?


What type of areas use more wood for fuel?


What benefit besides the cozy atmosphere would a wood-burning fireplace add to a home?


Wood has been an important construction material since humans began building shelters, houses and boats. Nearly all boats were made out of wood until the late 19th century, and wood remains in common use today in boat construction. Elm in particular was used for this purpose as it resisted decay as long as it was kept wet (it also served for water pipe before the advent of more modern plumbing).


What plumbing component was once made out of elm?


Until the late 19th century, what vessels were almost always wooden?


What significant purpose has wood been used for as long as humans have built shelters?


Other than boats, what do people often build with wood?


What term is used in North America for wood used in construction?

Wood to be used for construction work is commonly known as lumber in North America. Elsewhere, lumber usually refers to felled trees, and the word for sawn planks ready for use is timber. In Medieval Europe oak was the wood of choice for all wood construction, including beams, walls, doors, and floors. Today a wider variety of woods is used: solid wood doors are often made from poplar, small-knotted pine, and Douglas fir.


Outside of North America, if someone said "lumber," to what would they be referring?


What do people outside of North America call the sawn boards used for building?


What was the preferred wood for construction in Medieval Europe?


For modern solid wood doors, what wood is often used in addition to small-knotted pine or poplar?


What type of construction is often used now to build homes in much of the world?

New domestic housing in many parts of the world today is commonly made from timber-framed construction. Engineered wood products are becoming a bigger part of the construction industry. They may be used in both residential and commercial buildings as structural and aesthetic materials.


In addition to residential applications, what type of buildings often have engineered wood components?


Along with decorative components, what type of building materials can be engineered from wood?


What industry benefits greatly from engineered wood products?


What might wood be used for in a building made from brick or other materials?

In buildings made of other materials, wood will still be found as a supporting material, especially in roof construction, in interior doors and their frames, and as exterior cladding.


What crucial part of a house is often constructed from wood?


Wood might be used to construct what exterior component of a building?


Inside a building, what wooden things might you open to enter or leave rooms?


What holds together an engineered wood product?

Engineered wood products, glued building products "engineered" for application-specific performance requirements, are often used in construction and industrial applications. Glued engineered wood products are manufactured by bonding together wood strands, veneers, lumber or other forms of wood fiber with glue to form a larger, more efficient composite structural unit.


Engineered wood products are often used in construction, but what other major type of applications do they have?


What requirements do engineered wood products meet?


What efficient type of unit does the process of "engineering" wood result in?


Wood fibers from wood strands, lumber, and what other source can be glued together to make larger units?


What category do composite panels, strand board, and plywood all fit into?

These products include glued laminated timber (glulam), wood structural panels (including plywood, oriented strand board and composite panels), laminated veneer lumber (LVL) and other structural composite lumber (SCL) products, parallel strand lumber, and I-joists. Approximately 100 million cubic meters of wood was consumed for this purpose in 1991. The trends suggest that particle board and fiber board will overtake plywood.


What's another word for glued laminated timber?


If current building trends continue, what material will be replaced by particle and fiber board?


About how many cubic meters of wood was used in 1991 to make products like glulam, LVL, and structural composite lumber?


What material results from chemically breaking down wood?

Wood unsuitable for construction in its native form may be broken down mechanically (into fibers or chips) or chemically (into cellulose) and used as a raw material for other building materials, such as engineered wood, as well as chipboard, hardboard, and medium-density fiberboard (MDF). Such wood derivatives are widely used: wood fibers are an important component of most paper, and cellulose is used as a component of some synthetic materials. Wood derivatives can also be used for kinds of flooring, for example laminate flooring.


What's the abbreviation for medium-density fiberboard?


How is wood broken down into chips and fibers?


What type of flooring can be made from wood derivatives?


What widely-used product is almost always made of wood fibers?


What category of products usually made from wood includes chairs?

Wood has always been used extensively for furniture, such as chairs and beds. It is also used for tool handles and cutlery, such as chopsticks, toothpicks, and other utensils, like the wooden spoon.


What wooden utensil could you stir a pot of soup with?


Which parts of tools are sometimes made out of wood?


What pieces of furniture that most people use every night can be made out of wood?


What special wooden utensils do many people use to eat Chinese takeout?


What could we monitor electronically that could help inform new methods of wood protection?

Further developments include new lignin glue applications, recyclable food packaging, rubber tire replacement applications, anti-bacterial medical agents, and high strength fabrics or composites. As scientists and engineers further learn and develop new techniques to extract various components from wood, or alternatively to modify wood, for example by adding components to wood, new more advanced products will appear on the marketplace. Moisture content electronic monitoring can also enhance next generation wood protection.


Development in the wood manufacturing industry include using lignin to make what substance?


Instead of rubber, what important part of a car might someday be replaced by components of wood?


What material might be developed from wood that could make clothes that resist wear and tear?


In addition to extracting components from wood, what might scientist do by adding components, for example, to make innovative products?


Along with sculptures, what type of art have people been making out of wood for centuries?

Wood has long been used as an artistic medium. It has been used to make sculptures and carvings for millennia. Examples include the totem poles carved by North American indigenous people from conifer trunks, often Western Red Cedar (Thuja plicata), and the Millennium clock tower, now housed in the National Museum of Scotland in Edinburgh. It is also used in woodcut printmaking, and for engraving.


What did indigenous people in North America make out of the trunks of conifers?


What type of tree was often used for totem poles?


What city in Scotland would you visit to see the Millennium clock tower?


What museum exhibits the Millennium clock tower?


What kind of wood are clarinet bodies made from?

Certain types of musical instruments, such as those of the violin family, the guitar, the clarinet and recorder, the xylophone, and the marimba, are traditionally made mostly or entirely of wood. The choice of wood may make a significant difference to the tone and resonant qualities of the instrument, and tonewoods have widely differing properties, ranging from the hard and dense african blackwood (used for the bodies of clarinets) to the light but resonant European spruce (Picea abies), which is traditionally used for the soundboards of violins. The most valuable tonewoods, such as the ripple sycamore (Acer pseudoplatanus), used for the backs of violins, combine acoustic properties with decorative color and grain which enhance the appearance of the finished instrument.


What expensive wood with a prized color is used to make the backs of violins?


What category of wood is often used for musical instruments?


Along with resonance, what property of an instrument will be affected by the wood used to make it?


What type of instruments with a misleading name aren't always made completely out of wood?

Despite their collective name, not all woodwind instruments are made entirely of wood. The reeds used to play them, however, are usually made from Arundo donax, a type of monocot cane plant.


What are woodwind instrument's reeds often made out of?


Is the Arundo donax a monocot or dicot cane plant?


What objects do musicians have to have in order to play woodwind instruments?


What wood is usually used for cricket bats?

Many types of sports equipment are made of wood, or were constructed of wood in the past. For example, cricket bats are typically made of white willow. The baseball bats which are legal for use in Major League Baseball are frequently made of ash wood or hickory, and in recent years have been constructed from maple even though that wood is somewhat more fragile. NBA courts have been traditionally made out of parquetry.


Ash and hickory are often used for baseball bats to comply with the rules of what organization?


What is commonly used for the basketball courts the NBA plays on?


What wood has recently started being used to make baseball bats in addition to hickory and ash?


Compared to hickory and ash, what adjective might be used for a maple baseball bat?


What pieces of equipment for shooting arrows used to be wooden?

Many other types of sports and recreation equipment, such as skis, ice hockey sticks, lacrosse sticks and archery bows, were commonly made of wood in the past, but have since been replaced with more modern materials such as aluminium, fiberglass, carbon fiber, titanium, and composite materials. One noteworthy example of this trend is the golf club commonly known as the wood, the head of which was traditionally made of persimmon wood in the early days of the game of golf, but is now generally made of synthetic materials.


Which pieces of ice hockey equipment were once made out of wood?


When the golf club called the "wood" was actually made out of it, what type of wood was used?


What is the golf club known as the "wood" usually made out of today?


What other modern material has joined composites, carbon fiber, titanium, and aluminum to replace wood in the manufacture of sporting equipment?


What component of wood is degraded by bacteria that scientists are still trying to learn about?

Little is known about the bacteria that degrade cellulose. Symbiotic bacteria in Xylophaga may play a role in the degradation of sunken wood; while bacteria such as Alphaproteobacteria, Flavobacteria, Actinobacteria, Clostridia, and Bacteroidetes have been detected in wood submerged over a year.


What type of bacteria are present in Xylophaga?


What type of wood is it possible the bacteria in Xylophaga help break down?


How long was the wood submerged in water in the study that discovered the types of bacteria in it?


What bacteria starting with the letter "F" were found in wood after it was underwater for more than a year?


What language family is Somali a part of?

Somalis (Somali: Soomaali, Arabic: صومال) are an ethnic group inhabiting the Horn of Africa (Somali Peninsula). The overwhelming majority of Somalis speak the Somali language, which is part of the Cushitic branch of the Afro-Asiatic family. They are predominantly Sunni Muslim. Ethnic Somalis number around 16-20 million and are principally concentrated in Somalia (around 12.3 million), Ethiopia (4.6 million), Kenya (2.4 million), and Djibouti (464,600), with many also residing in parts of the Middle East, North America and Europe.


What part of the Afro-Asiatic language family is Somali a part of?


What is the majority religion of Somalis?


How many people of Somali ethnicity live in Somalia?


What country has the second largest Somali population?


From whom are several Somali clans descended?

Irir Samaale, the oldest common ancestor of several Somali clans, is generally regarded as the source of the ethnonym Somali. The name "Somali" is, in turn, held to be derived from the words soo and maal, which together mean "go and milk" — a reference to the ubiquitous pastoralism of the Somali people. Another plausible etymology proposes that the term Somali is derived from the Arabic for "wealthy" (dhawamaal), again referring to Somali riches in livestock.


From what words is the term 'Somali' generally regarded as being derived?


What does 'soo and maal' mean in English?


What word in Arabic means 'wealthy' in English?


What resource traditionally comprised Somali wealth?


What did the Arabs call the northern Somali coast in the 9th century?

An Ancient Chinese document from the 9th century referred to the northern Somali coast — which was then called "Berbera" by Arab geographers in reference to the region's "Berber" (Cushitic) inhabitants — as Po-pa-li. The first clear written reference of the sobriquet Somali, however, dates back to the 15th century. During the wars between the Sultanate of Ifat based at Zeila and the Solomonic Dynasty, the Abyssinian Emperor had one of his court officials compose a hymn celebrating a military victory over the Sultan of Ifat's eponymous troops.


What did the Chinese call the northern Somali coast in the 9th century?


In what century was the term 'Somali' first used?


Who ordered that a hymn be composed that first mentioned the Somalis?


Where was the Sultanate of Ifat located?


How long ago were rock paintings found in Somalia created?

Ancient rock paintings in Somalia which date back to 5000 years have been found in the northern part of the country, depicting early life in the territory. The most famous of these is the Laas Geel complex, which contains some of the earliest known rock art on the African continent and features many elaborate pastoralist sketches of animal and human figures. In other places, such as the northern Dhambalin region, a depiction of a man on a horse is postulated as being one of the earliest known examples of a mounted huntsman.


Where are the most notable rock paintings located?


Along with animals, what is depicted on the rock paintings of Laas Geel?


Where does a notable rock painting of a man on horseback exist?


In what geographic part of Somalia are these rock paintings commonly found?


Along with the Hargesian culture, what culture was present in Somalia in the Stone age?

Inscriptions have been found beneath many of the rock paintings, but archaeologists have so far been unable to decipher this form of ancient writing. During the Stone age, the Doian culture and the Hargeisan culture flourished here with their respective industries and factories.


What undeciphered writings were found alongside the rock paintings?


During what period did the Doian culture thrive?


In what country is the oldest evidence of ceremonial burial in the Horn of Africa located?

The oldest evidence of burial customs in the Horn of Africa comes from cemeteries in Somalia dating back to 4th millennium BC. The stone implements from the Jalelo site in northern Somalia are said to be the most important link in evidence of the universality in palaeolithic times between the East and the West.


From what millennium do the oldest cemeteries in the Horn of Africa date?


At what site were important paleolithic stone tools found?


In what geographic part of Somalia were important paleolithic stone tools found?


What economic activity in the Horn of Africa did the ancient Somalis connect to the rest of the world?

In antiquity, the ancestors of the Somali people were an important link in the Horn of Africa connecting the region's commerce with the rest of the ancient world. Somali sailors and merchants were the main suppliers of frankincense, myrrh and spices, items which were considered valuable luxuries by the Ancient Egyptians, Phoenicians, Mycenaeans and Babylonians.


Along with myrrh and spices, what important luxury did ancient Somali merchants provide?


Along with the ancient Phoenicians, Egyptians and Babylonians, what ancient people regarded myrrh as a luxury?