Uhhh...errr...uuhh...Tod, old friend, old pal, er, uh, the speed of
sound goes down with decreasing air density (increasing altitude),
so the mach value in a vacuum would be more like
1 over "1 Gazil-ilbil-i-quilizillion" MPH!
Think more like Tim Conway's old man character.
Or the LSD scenes from bad movies :)
Or the speed of the SOB in front of you when you're late for work.
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On Wed, 19 May 2004 16:23:19 +0000 (UTC), "Doug Sams"
Doh! Yep, you're right, Doug! I was thinking backwards. Must be the
effects of this damn Van DeGraaff generator my daughter and I built.
I've zapped myself enough such that my right forearm was twitching
there for awhile...
I wonder how many static shocks a human can take before brain damage
Wow! What a ball to play with! We're pulling 5" sparks with 97%
humidity! Imagine what it would do on a cold winter day around these
On Wed, 19 May 2004 19:19:50 GMT, "Steven P. McNicoll"
The speed of sound in the atmosphere is proportional to the square
root of temperature. The universe background "temperature" is around
3 Deg. K. Interstellar gas density is on the order of one hydrogen
per cc. Such gas does not flow like an atmospheric gas, but you do
have Newtonian flow, which can still be a problem when you get your
starship up to speed. The Shuttle and space station do not have great
vacuum because of all the local outgassing. In an earth bound lab,
you can get a better vacuum by sweeping and trapping gas molecules.
Negative. the speed of sound is a function of DENSITY. NOTHING else.
Temperature effects density and that is the only way that temperature
effects the speed of sound.
sound will travel through a shaft of solid steel at 70' faster than it will
travel through the same physical space of AIR at 70' and 1 ATM.
Density decides what the speed of sound is.
On Thu, 20 May 2004 19:30:42 -0400, "Chris Taylor Jr"
Temperature has an affect on the speed of sound even though you said
density is the only function, and, um, temperature is related to
density, and um, temperature is, like density, a phyiscal property of
matter, and um, and nothing else? And, the speed of sound is a
function of density, and nothing else........
WHAT DO I WIN?! WHAT DO I WIN?!
Nice to have you back, Chris...
that is like saying that the jet engine is a function of the speed of sound
since it lets you GO the speed of sound and is foolish logic.
temperature is irrevant and here is how to prove it.
you can have two objects at the exact same temperature and yet the speed or
sound through them WILL be different.
since we have removed temperature from the equation and yet still have a
difference we know temperature is NOT directly a factor. only indirectly in
that is can alter density. density is what directly affects the speed of
if you can alter density via temp fine. but its secondary. indirect.
density is the key.
thanks. very very busy :-( new jobs working 7 days a week :-(
Chris, you're confusing two different issues... you're talking about
differences in the speed of sound through different _kinds of materials_
(comparing liquids to gases) but the question - for purposes of describing
a "mach number" in flight - was about how the speed changes in the SAME
KIND of material, at different pressures and temperatures. How does AIR
change its speed of sound at different pressures or at different temperatures?
That turns out to be a quite separate question from the difference between
different kinds of material, as in comparing air to liquids or solids!
Chris Taylor Jr wrote:
because it has a different DENSITY down here than it does up there.
in the SAME material pressure and temperature do not effect speed of sound.
it effects DENSITY which then effect speed of sound.
at least that is what I was taught :-)
No, you have it backwards.
At the same temperature, the speed of sound will be the same (in a
given medium such as air) at widely different densities. For example,
consider the following values from standard atmosphere data:
Altitude Density Temp SofS
(meters) (g/m^3) deg. C m/sec
-------- ------ ------ ----
5000 736 -17.5 320
15000 193 -56.5 295
41500 3.09 -17.9 320
The density is many times lower at 41500 meters, but the speed of sound is
about the same as at 5000 meters, because the temperature is the same.
At an intermediate value of density at 15000 meters, the speed of sound
and the temperature are both noticeably lower than at the higher or the
lower altitude. (Source of the data was the Standard Atmosphere Computations
web page at http://aero.stanford.edu/StdAtm.html - you can put in any altitude
in feet or meters and it will give you the density, temperature, and speed of
sound, among other characteristics of the air at that altitude).
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