Following Felix Baumgartner's free-fall native the leaf of space, a look in ~ the physics the the rate of sound.

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This seems to be the most common discussion regarding the recent Red Bull Stratos Jump. Uneven you have actually been life under a rock lately, you have actually probably seen the awesome jump from 128,000 feet. Here is a an excellent summary video clip to obtain you pumped up.

The official fastest totally free fall rate was reported together 373 m/s. AH HA! that is simply barely end the speed of sound in ~ 340 m/s. My physics textbook claims this is the speed of sound, therefore there. Well, not so fast. Sound is a pretty complex thing.

What Is a Sound Wave?

First, let me talk around just sound in air. Of food you can have sound waves underwater (hello submarines) and also even through solids. But think of air. At one level, wait is comprised of a whole bunch of tiny particles. Five sure, it is yes, really more complex than simply tiny waiting particles. The is greatly nitrogen gas (N2) through some oxygen. But in this model of sound waves, it is fine to think of lock all together just tiny particles.

What wake up if you take a totality bunch of these particles and also push them all at the same time? Well, the pushed particles will go a small ways, however they will certainly collide with various other air particles and push them. Those particles will certainly collide with much more and therefore on and so on. This is what we call a wave. The essential thing to realize is the the air isn't moving really far, but the compression is moving. Below is my attempt at a diagram reflecting this.


Another an excellent example the this is the tide in a soccer stadium. Right here is an example in situation you have actually no idea what i am talking about.


What goes around the stadium? The people? No, they simply move up and down. It is the disturbance that moves as the wave. The very same is true for sound waves in air. OK, but that is just a simple model that sound. How quick is the sound tide in air? although 340 m/s (760 mph) is a good very first answer, it isn't constantly true. Let's look earlier a the wave of human being in a football stadium. What would make this rate change? Two things could plainly make a difference. Suppose the stadion wasn't full but instead about every other seat to be occupied. This could readjust the speed of the sound wave. The isn't fairly clear if it would make it much faster or slower, but I would certainly guess faster because the human would be reaction to the previous person that was farther away. An additional effect might be from the alertness level of the crowd. If people weren't paying much attention, it could cause a longer reaction time and thus a lower wave speed.

Actually, now I to be curious. Ns wonder if stadium wave speeds room fairly constant for various stadiums and also crowds. My guess is that they would all have similar speed values. Perhaps this will certainly be a future blog post.

OK, ago to sound waves in air. What walk this speed rely on? You might guess a few things. Just like the football group wave, the thickness of particles must matter. And what around the press in the air? that should issue too, right? how amazing (at least for me), a an easy model because that the speed of sound only varies through air temperature. Why? Well, together you get higher in the altitude (up to a point), the temperature decreases. The pressure and also the density of air also decrease. The effects because of pressure and density essentially negate every other. Prefer I said, this end simplifies the whole issue. The Wikipedia web page on the speed of sound has a lot an ext detail if you are interested.

Speed of Sound vs. Altitude

If you put this together, friend can get a plot of the speed of sound together a duty of altitude. Oh sure, the will change with weather and also stuff, however still friend can get a pretty basic model. Below is a plot that the speed of sound at various heights over sea level.


At sea level, the value is right about the 340 m/s mark. If you relocate up to 120,000 feet, the rate will drop under to around 200 m/s. Just from this data, you deserve to see that Felix Baumgartner walk indeed fall faster 보다 the rate of sound. However, the inquiry doesn't really make sense. Walk he loss faster 보다 the rate of sound in ~ sea level? Yes. Was he also going much faster than the rate of sound for the altitude he was at? Well, it provides logical feeling that if the rate of sound is greatest at sea level and he went much faster than the rate of sound he would be going quicker than the locals speed of sound.

Speed vs. The local Speed the Sound

I don't recognize if "local rate of sound" is an main term, but I like it. I am making use of it to average the rate of sound in ~ the current altitude. Right here is a plot that the rate of Felix as he falls in addition to the plot of the neighborhood speed of sound at that very same time.


You will notice that from this number calculation, Felix to be going quicker than the local speed the sound for about 45 seconds. You should also an alert that this calculation has actually his maximum speed a small over the reported worth of 373 m/s - hopefully I have the right to fix this later on when i compare my design to the real data - yet it's not too much off.

Mach Number

I guess i was best (at least according come Wikipedia). It has actually the an interpretation of Mach number as the proportion of the rate of an item to the local speed of sound. Right here is a plot that the speed of Felix together a role of altitude in terms of the Mach number (again, this is based upon my not so perfect model).

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From this, he had actually a maximum speed of Mach 1.7 rather of the report Mach 1.24. Of food this is really dependent on the actual rate of sound at that altitude. If the version is turn off a tiny bit on the rate of Felix as well as the rate of sound at the altitude (both using basic models), that could explain the discrepancy.

Either way, there seems to be tiny doubt the went much faster than the rate of sound. However, that didn't break the rate of light. What? Yes. Below is an display shot from MSNBC. I have actually trouble believing this is real, yet I couldn't discover evidence the it to be fake. In instance you didn't click the image, it reflects Felix Baumgartner after that stabilized his fall. The subtitle reads (and I child you not):