space.com— Astronomers just got their most detailed look yet at supersonic ?bullets? of gas piercing through dense clouds of hydrogen gas in the Orion Nebula.
Mar 22, 2007View in Crawl 4
One question - why do they use the term, "supersonic" ?In space, sound does not propagate, correct? No air molecules to pass the sound vibration.So what would be the speed of sound? 0? Infinity?
In vacuum, sound does not propagate. Within the gas, it likely would, since it has to be fairly dense to maintain temperatures that would keep iron in a gaseous form. But the propagation would depend on that density (pressure). Here, it is most likely that a "science writer" referred the speed back to an understandable Earth-bound quantity for illustration's sake.The speed in vacuum would be 0 and nothing (real, that we know of) travels faster than ~3000000 meters per second.
You could consider it infinite, but we really don't know. The limits of our observation drop off around 15 billion lightyears, which is still really really big. Our solar system is ~80 AU in diameter. A single lightyear is over 63000 AU. Now, 15 billion of those is a lot. Really a lot.Here's a fun one. Within a factor of 10, the average galaxy is estimated to have around 10 billion stars. In the same ballpark, the number of galaxies is estimated around 100 billion. This gives us around 1,000,000,000,000,000,000,000 stars in the known universe, or a 1000 billion billion, or 1E21 (1 with 21 0's after it).Now, that's all well and good, big huge unimaginably large numbers, right?Get this though, a cubic centimeter (a cube that is 1cm on each side) of pure water contains around 33,000,000,000,000,000,000,000 (3.3E22) water molecules, or about 33 times as many molecules as there are stars in the universe.
Yes, "supersonic" is about the worst possible description. In large, disperse gas clouds the speed of sound is likely to be far, far less than the speed of sound through air on Earth - something travelling at about the speed of a top sprinter is likely to be supersonic in a medium that dense. 250 miles per second is around 900000 miles per hour - many orders of magnitude faster than the speed of sound through air on Earth. Describing these jets as "supersonic" may be true but it is almost irrelevant considering the actual speed of these supposed gas bullets.
keegsterMar 23, 2007
NRA:1 Universe: 0 :-/
ebob9Mar 23, 2007
One question - why do they use the term, "supersonic" ?In space, sound does not propagate, correct? No air molecules to pass the sound vibration.So what would be the speed of sound? 0? Infinity?
ketemphorMar 23, 2007
In vacuum, sound does not propagate. Within the gas, it likely would, since it has to be fairly dense to maintain temperatures that would keep iron in a gaseous form. But the propagation would depend on that density (pressure). Here, it is most likely that a "science writer" referred the speed back to an understandable Earth-bound quantity for illustration's sake.The speed in vacuum would be 0 and nothing (real, that we know of) travels faster than ~3000000 meters per second.
ketemphorMar 23, 2007
You could consider it infinite, but we really don't know. The limits of our observation drop off around 15 billion lightyears, which is still really really big. Our solar system is ~80 AU in diameter. A single lightyear is over 63000 AU. Now, 15 billion of those is a lot. Really a lot.Here's a fun one. Within a factor of 10, the average galaxy is estimated to have around 10 billion stars. In the same ballpark, the number of galaxies is estimated around 100 billion. This gives us around 1,000,000,000,000,000,000,000 stars in the known universe, or a 1000 billion billion, or 1E21 (1 with 21 0's after it).Now, that's all well and good, big huge unimaginably large numbers, right?Get this though, a cubic centimeter (a cube that is 1cm on each side) of pure water contains around 33,000,000,000,000,000,000,000 (3.3E22) water molecules, or about 33 times as many molecules as there are stars in the universe.
Closed AccountMar 23, 2007
supersonic at a thousand times the speed of sound? No that's ludicrous speed.
Closed AccountMar 23, 2007
@ ketemphorExcellent perspective. In other words, there is a buttload of matter in this world, and the universe is mostly empty.
thuktunMar 23, 2007
If those "torpedoes" are ten times the diameter of our solar system, those starships must be pretty damned big.
thepictMar 23, 2007
@dclowd9901Yes.Edit: Oh, s**t, I've been on this page for 4 hours?!?
cypherspaceMar 24, 2007
Yes, "supersonic" is about the worst possible description. In large, disperse gas clouds the speed of sound is likely to be far, far less than the speed of sound through air on Earth - something travelling at about the speed of a top sprinter is likely to be supersonic in a medium that dense. 250 miles per second is around 900000 miles per hour - many orders of magnitude faster than the speed of sound through air on Earth. Describing these jets as "supersonic" may be true but it is almost irrelevant considering the actual speed of these supposed gas bullets.