[mamelukesabre]

The speed of sound is not constant. It is faster in denser air and slower in less dense air. Basically, that 690MPH figure is only at low elevations...much slower than that at very high altitudes.

Havn’t you ever noticed at high elevations, like on a mountain, you see things before you hear the sound they make? Like someone dribbling a basket ball say 35 yards away at elevations over 5000feet. You hear the ball hit the pavement about the same time you see the ball half way between the person’s hand and the pavement.

[jaydubya2]

They are claiming that 680 MPH IS the speed of sound at 120k ft. I’m not sure if that is correct or not. I know that the speed of sound is about 760 mph at sea level.

[thackney]

Havn’t you ever noticed at high elevations, like on a mountain, you see things before you hear the sound they make?

That is always the case, noticeable at significant distances.

The speed of light is always going to be far greater than the speed of sound, at any elevation.

[TalonDJ]

Havn’t you ever noticed at high elevations, like on a mountain, you see things before you hear the sound they make?

That happens at sealevel... or anywhere. The speed of light is vastly higher than the speed of sound ANYWHERE.