by neufer » Wed Sep 22, 2010 3:27 pm
Chris Peterson wrote:drollere wrote:"much less dense than earth's atmosphere" ... at what altitude? sea level? 50 miles?
Either? I think the intent of the statement was simply to provide some sense of the actual densities involved, not really a quantitative value. Regions with dust clouds like those in this nebula essentially qualify as pretty good vacuums. Significant extinctions are probably not reached until light travels many astronomical units in such a cloud.
http://en.wikipedia.org/wiki/Bok_globule wrote:
<<Bok globules or Thackeray's Globules are dark clouds of dense dust and gas in which star formation sometimes takes place. Bok globules are found within H II regions, and typically have a mass of about 2 to 50 solar masses (i.e., up to 1×10
32 kg) contained within a region about a light year or so across (about 4.5 × 10
47 m³). They contain molecular hydrogen (H2), carbon oxides and helium, and around 1% (by mass) of silicate dust.>>
http://en.wikipedia.org/wiki/Vacuum wrote:
- Vacuum __________________ Pressure (Torr)
------------------------------------------------------------
Low vacuum _______________ 760 to 25
Medium vacuum ____________ 25 to 1×10−3
High vacuum _____________ 1×10−3 to 1×10−9
Ultra high vacuum _________ 1×10−9 to 1×10−12
Extremely high vacuum _______ <1×10−12
Bok globules _____________ 6×10−16 to 15×10−15 (at room temperature)
------------------------------------------------------------------------------------------------------------------------
# Low vacuum, also called rough vacuum or coarse vacuum, is vacuum that can be achieved or measured with rudimentary equipment such as a vacuum cleaner and a liquid column manometer.
# Medium vacuum is vacuum that can be achieved with a single pump, but the pressure is too low to measure with a liquid or mechanical manometer. It can be measured with a McLeod gauge, thermal gauge or a capacitive gauge.
# High vacuum is vacuum where the MFP of residual gases is longer than the size of the chamber or of the object under test. High vacuum usually requires multi-stage pumping and ion gauge measurement. Some texts differentiate between high vacuum and very high vacuum.
# Ultra high vacuum requires baking the chamber to remove trace gases, and other special procedures. British and German standards define ultra high vacuum as pressures below 10−6 Pa (~10−8 Torr).
http://en.wikipedia.org/wiki/Wake_Shield_Facility wrote:
<<Wake Shield Facility is an experimental science platform that was placed in low-earth orbit by the Space Shuttle. It is a 3.7 meter (12 ft) diameter, free-flying stainless steel disk. The WSF is deployed in the wake of the Space Shuttle at an orbital altitude of over 300 kilometers (186 mi), within the thermosphere, where the atmosphere is exceedingly tenuous. The forward edge of the WSF disk redirects atmospheric and other particles around the sides, leaving an "ultra-vacuum" in its wake. The resulting vacuum is used to study epitaxial film growth. Pre-flight calculations suggested that the pressure on the wake side could be decreased by some 6 orders of magnitude over
the ambient (10−8 Torr) pressure in low earth orbit. Analysis of the pressure and temperature data gathered from the two flights concluded that the decrease was some 2 orders of magnitude or 4 orders of magnitude less than expected (i.e.,
from 10−10 to 10−12 Torr).
The WSF has flown into space three times, on board shuttle flights STS-60, STS-69 and STS-80.
During STS-60, some hardware issues were experienced and as a result the WSF was only deployed at the end of the shuttle's robotic arm. During the later missions the WSF was deployed as a free-flying platform in the wake of the shuttle. These flights proved the vacuum wake concept, and realized the space epitaxy concept by growing the first-ever crystalline semiconductor thin films in the vacuum of space. These included gallium arsenide (GaAs) and aluminum gallium arsenide (AlGaAs) depositions. These experiments have been used to develop better photocells and thin films. Among the potential resulting applications are artificial retinas made from tiny ceramic detectors.>>
http://en.wikipedia.org/wiki/Tor_Johnson wrote:
Tor Johnson (19 October 1903 – 12 May 1971) was a
Swedish professional wrestler (billed as
The Super Swedish Angel) and actor. He is perhaps best remembered for his roles in a number of B-movies, including police inspector turned zombie Daniel Clay in
Plan 9 from Outer Space. Tor Johansson was born in Sweden, the son of Karl J. Johansson and Lovisa Petersson. He was a large man, weighing 400 pounds at his biggest. He had a full head of blond hair, but he shaved it to maintain an imposing, villainous appearance in wrestling and acting appearances. He began getting bit parts in movies upon his move to California - usually as the strongman or weightlifter - as early as 1934. His film career ended in the early 1960s after appearing in a string of poorly-rated movies. However, he continued to make appearances on television and made a number of commercials. Due to his work in early B-horror movies, Tor developed a small but enthusiastic cult following after his death in 1971. A number of Johnson's peers had commented that he was a very friendly man and easy to work with on movie sets. Valda Hansen, who worked with Johnson in the 1959 movie Night of the Ghouls said that "Tor was like a big sugar bun." Johnson befriended Bela Lugosi during the time both worked with director Edward D. Wood, Jr.
[quote="Chris Peterson"][quote="drollere"]"much less dense than earth's atmosphere" ... at what altitude? sea level? 50 miles?[/quote]
Either? I think the intent of the statement was simply to provide some sense of the actual densities involved, not really a quantitative value. Regions with dust clouds like those in this nebula essentially qualify as pretty good vacuums. Significant extinctions are probably not reached until light travels many astronomical units in such a cloud.[/quote]
[quote=" http://en.wikipedia.org/wiki/Bok_globule"]
<<Bok globules or Thackeray's Globules are dark clouds of dense dust and gas in which star formation sometimes takes place. Bok globules are found within H II regions, and typically have a mass of about 2 to 50 solar masses (i.e., up to 1×10[sup]32[/sup] kg) contained within a region about a light year or so across (about 4.5 × 10[sup]47[/sup] m³). They contain molecular hydrogen (H2), carbon oxides and helium, and around 1% (by mass) of silicate dust.>>[/quote]
[quote=" http://en.wikipedia.org/wiki/Vacuum"]
[list]Vacuum __________________ Pressure ([b][color=#FF0000]Torr[/color][/b])
------------------------------------------------------------
Low vacuum _______________ 760 to 25
Medium vacuum ____________ 25 to 1×10[sup]−3[/sup]
High vacuum _____________ 1×10[sup]−3[/sup] to 1×10[sup]−9[/sup]
[color=#FF00FF]Ultra high vacuum _________ 1×10[sup]−9[/sup] to 1×10[sup]−12[/sup][/color]
Extremely high vacuum _______ <1×10[sup]−12[/sup]
Bok globules _____________ 6×10[sup]−16[/sup] to 15×10[sup]−15[/sup] (at room temperature)[/list]------------------------------------------------------------------------------------------------------------------------
# Low vacuum, also called rough vacuum or coarse vacuum, is vacuum that can be achieved or measured with rudimentary equipment such as a vacuum cleaner and a liquid column manometer.
# Medium vacuum is vacuum that can be achieved with a single pump, but the pressure is too low to measure with a liquid or mechanical manometer. It can be measured with a McLeod gauge, thermal gauge or a capacitive gauge.
# High vacuum is vacuum where the MFP of residual gases is longer than the size of the chamber or of the object under test. High vacuum usually requires multi-stage pumping and ion gauge measurement. Some texts differentiate between high vacuum and very high vacuum.
[color=#FF00FF]# Ultra high vacuum requires baking the chamber to remove trace gases, and other special procedures. British and German standards define ultra high vacuum as pressures below 10[sup]−6[/sup] Pa (~10[sup]−8[/sup] Torr).[/color][/quote]
[quote=" http://en.wikipedia.org/wiki/Wake_Shield_Facility"]
[float=right][img3="Deployment of the WSF using the Space Shuttle robotic arm.
Night period STS-60 photo"]http://upload.wikimedia.org/wikipedia/commons/thumb/c/c1/Wake_shield_facility.jpg/543px-Wake_shield_facility.jpg[/img3][/float]<<Wake Shield Facility is an experimental science platform that was placed in low-earth orbit by the Space Shuttle. It is a 3.7 meter (12 ft) diameter, free-flying stainless steel disk. The WSF is deployed in the wake of the Space Shuttle at an orbital altitude of over 300 kilometers (186 mi), within the thermosphere, where the atmosphere is exceedingly tenuous. The forward edge of the WSF disk redirects atmospheric and other particles around the sides, leaving an "ultra-vacuum" in its wake. The resulting vacuum is used to study epitaxial film growth. Pre-flight calculations suggested that the pressure on the wake side could be decreased by some 6 orders of magnitude over [b][color=#0000FF]the ambient (10[sup]−8[/sup] Torr) pressure in low earth orbit[/color][/b]. Analysis of the pressure and temperature data gathered from the two flights concluded that the decrease was some 2 orders of magnitude or 4 orders of magnitude less than expected (i.e., [b][color=#FF00FF]from 10[sup]−10[/sup] to 10[sup]−12[/sup] Torr[/color][/b]).
The WSF has flown into space three times, on board shuttle flights STS-60, STS-69 and STS-80. [b][color=#0000FF]During STS-60, some hardware issues were experienced and as a result the WSF was only deployed at the end of the shuttle's robotic arm. During the later missions the WSF was deployed as a free-flying platform in the wake of the shuttle.[/color][/b] These flights proved the vacuum wake concept, and realized the space epitaxy concept by growing the first-ever crystalline semiconductor thin films in the vacuum of space. These included gallium arsenide (GaAs) and aluminum gallium arsenide (AlGaAs) depositions. These experiments have been used to develop better photocells and thin films. Among the potential resulting applications are artificial retinas made from tiny ceramic detectors.>>[/quote][quote=" http://en.wikipedia.org/wiki/Tor_Johnson"]
[float=right][img3="Deployment of the Mona McKinnon using [b][color=#FF0000]Tor Johnson[/color][/b]'s arms.
Night period Plan 9 from Outer Space [b][url=http://en.wikipedia.org/wiki/History_of_World_Wrestling_Entertainment]WWF[/url][/b] photo"]http://upload.wikimedia.org/wikipedia/commons/8/8c/Tor_Johnson.jpg[/img3][/float]
[b][color=#FF0000]Tor Johnson[/color][/b] (19 October 1903 – 12 May 1971) was a [b][color=#FF0000]Swedish[/color][/b] professional wrestler (billed as [b][color=#FF0000]The Super Swedish Angel[/color][/b]) and actor. He is perhaps best remembered for his roles in a number of B-movies, including police inspector turned zombie Daniel Clay in [b][color=#0000FF]Plan 9 from Outer Space[/color][/b]. Tor Johansson was born in Sweden, the son of Karl J. Johansson and Lovisa Petersson. He was a large man, weighing 400 pounds at his biggest. He had a full head of blond hair, but he shaved it to maintain an imposing, villainous appearance in wrestling and acting appearances. He began getting bit parts in movies upon his move to California - usually as the strongman or weightlifter - as early as 1934. His film career ended in the early 1960s after appearing in a string of poorly-rated movies. However, he continued to make appearances on television and made a number of commercials. Due to his work in early B-horror movies, Tor developed a small but enthusiastic cult following after his death in 1971. A number of Johnson's peers had commented that he was a very friendly man and easy to work with on movie sets. Valda Hansen, who worked with Johnson in the 1959 movie Night of the Ghouls said that "Tor was like a big sugar bun." Johnson befriended Bela Lugosi during the time both worked with director Edward D. Wood, Jr.[/quote]