# Is mach 1 in space equal to C ?

Space is so much less dense that to cause a furl of space fabric to collapse around a moving body (mach 1) would have to be so much faster than in our atmosphere .

If you don't understand how the sonic boom occurs please don't answer unless you are a mathematician .

I read the whole article you referred to, and I am still a bit confused by your question. Let's review mach 1 or shock waves. Basically, as a plane travels through the atmosphere, sound is sent in all directions from the wing (and elsewhere.) If the plane travels close to the speed of sound, the wing almost catches each wave when the next one is emitted, so the wavelengths ahead of the wing are very short. The reverse happens behind the wing, so this is the Doppler Effect you are talking about.

At the speed of sound, the wing catches up with each wave as it is emitted, and the waves pile up in front of the plane. We can see a very similar effect with the V-shaped "bow wave" of a boat as it travels through water, since boats can easily travel faster than the speed of a water wave.

This is the chief reason many planes have wings that are swept back, so they can stay behind the V of the shock wave, and their control surfaces will not be shaken and made difficult to handle by the shock wave.

All of this requires a "medium", water for the boat, or air for the plane, for the waves to travel through. No medium means no waves. A comet or any other fast moving object is not traveling through a medium since space is an almost perfect vacuum. It does have on the order of 4 or 5 molecules per cubic meter (check me on that), but it's by far a better vacuum than we can produce on earth. So, there's no sound and no shock wave.

The glowing in the picture on Fox Noise (oops, News) is caused only because the comet is getting close to the sun. As the article says, the side near the sun is heated enough by the sun to boil away some of the frozen gases that make up the comet. After all, frozen hydrogen and other gases are at very low temperatures, so it doesn't take much heat to boil them away. This glow is NOT caused by friction with anything like an atmosphere.

I don't think there is any turbulance in the tail. The tail might not be uniform, but that is because the boiling isn't uniform, since the frozen gas ball comet isn't uniform. It's more like a dirty snowball, and there are parts of it where more gas boils off than others. Anyway, the tail always points away from the sun, so as it swings around the sun, the tail won't point to the back of its motion, if it were caused by turbulence, the tail can be even at right angles to the direction of travel of the comet when it's near the sun. The tail is pushed away from the comet by the pressure of sunlight.

So, some interesting thinking about comets. Continue to read up on them! However, they have nothing to do with Mach numbers or the speed of sound or light in space!

#1

If Mach 1 had any meaning in space, it could only be another name for 343 metres per second, which is the conventional figure for the speed of sound on earth.

Space is an almost perfect vacuum. Gravity made sure of that, long ago.

#2

Mach 1 is the speed of sound through air. C is the speed of light. There is as huge difference. There would be no sonic boom in space as sound requires the vibration of air and there is none in space.

#3

I understand how a sonic boom occurs, and this question is obviously to find an answer.

You need to be in a gas for a wave to propagate in all directions away from the craft (sound) and then to accelerate through it(or better to say overtake the sound that is trying to move away from you in the direction you are moving).

The thing is that while experiments like to show stretching of space like a cloth on TV to show things like black holes, there isn't actually any cloth. (Or said a better way) The cloth is only scrunched up or stretched by large masses, speed has nothing to do with it.

The only way to go "mach anything" in space would be if you were going through a large dust cloud, and then the speed would be dependent on the density of the cloud.

And even then the poof in the cloud would only be thought of as a boom if you were being really nice.

#4