Saturday, August 7, 2010

Did You Feel That?

I was reading through the chapter readings this morning, and I got to the section talking about the motion of gas particles, specifically the part where it said that a gas particle will move at an average speed of 500m/s. Now, obviously this is an incredibly fast speed, especially for something that exists at such an incredibly small size. However, there was something that struck me after I read that, which is that constantly we're being hit by these particles, yet never feel them (a point I can quickly justify through the fact that a particle is nothing compared to a human, and that you couldn't even compare a particle hitting a human to a bug hitting the windscreen). The point I want to make from this, is that even though we know we're constantly being hit by these particles, and that it never feels like we're being hit, what happens if we stop being hit by these particles? What happens if we put ourselves in say a vaccuum, where we have no particles to hit us? Would it feel different?
The answer to this would obviously come down to how many particles are in fact hitting us at any given moment, or the average amount that we are always in contact with, but I thought that this would be a interesting thing to put out there.


  1. I also wonder what low pressure feels like. I only really know what about 101.3kPa feels like. I suspect low pressure would feel similar to atmospheric pressure, but if you waved your arms, you wouldn't feel wind rush past them.

  2. Compare the kinetic energy of one molecule of say, O2 using 1/2mv^2 and you get around ~5x10^-21 J to the kinetic energy of a car say 500 kg moving at 60 kmhr-1 which has a KE of around 64000 J. With the motion of the air being random and not in one set direction. This is why you don't feel the air too much.

  3. Further to my comment if you take the approximate energy of that one molecule and multiply by Avogadro's constant gives you roughly 3000 J. I'm sure you would be able to feel that sort of energy. How would you go about calculating the probability of ~6.02 x 10^23 molecules colliding with you with the same velocity direction and time?

  4. Anybody seen "Total Recall"? I often wonder how accurate the "extreme depressurization scenes" are.

    Probably it would feel like the worst-ever case of the bends (hopefully for not very long).