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B No sound in vacuum? So can I clap more?

  1. Jun 29, 2018 #1
    I was just wondering (Wondering!? Stop wasting our precious time!) about clapping my hands.
    It's sound energy. A little energy is released as heat.
    This means that I have used some energy from my body. In making those two energies.
    <<Mentor note: rant removed>>
    So, I am in a vacuum. And I clap. Wonderful. I hear no sound.
    But does this mean that the clap sound isn't being produced at all?
    That is, the energy which was being converted to heat and sound is now being converted to just heat ( I understand there will be friction. Else there won't be any clap.)
    So, the question is: Can I clap more times in a vacuum? As energy use is reduced?

    Thanks for reading. Keep physicking.
    Last edited by a moderator: Jun 29, 2018
  2. jcsd
  3. Jun 29, 2018 #2


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    There would still be sound waves in your body

    Your hands have no drag, so that makes it easier.
  4. Jun 29, 2018 #3


    Staff: Mentor

    In air, some of the energy is converted to sound (vibrations in the air) and carried away.

    In a vacuum, there is no air to vibrate. There might be vibrations in your flesh and blood. But less energy is carried away from your hands, so more heat will be generated.
  5. Jun 29, 2018 #4


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    I suspect it would feel noticeably different as they come together with no air in between them. Your mind would probably be on other things at the time but you could be applauding the skill of the airlock operator (ironically, perhaps).
  6. Jun 29, 2018 #5


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  7. Jun 30, 2018 #6
    I would think the proportion of energy that comes out as sound from a hand clap is minimal compared to the kinetic energy exchange that's happening when you accelerate your hand then collide it with the other hand. Just look at the mass difference, you are moving and stopping water filled meat ballons (~1kg/liter) to move air (1.2g/liter).
  8. Jul 3, 2018 #7


    Staff: Mentor

    You mean before you explode from being in a vacuum. You cant clap in a vacuum because you would not be alive. Suppose you are in a space suit and clap - sound will be produced inside the suit as per normal. The suit will of course also vibrate - but that vibration will not transfer energy to anything outside because there is nothing outside - but inside - it's as per normal.

    A much better question is all these movable parts they have on say the space-station etc exposed to space - what happens to the sound they would normally make when they move if it was here on earth.

    I will let you think about that one.

  9. Jul 3, 2018 #8


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    You don't explode in a vacuum. You'd die pretty quickly, but you could probably clap a few times before you went.
  10. Jul 3, 2018 #9
    Its not even that quick in the general scheme of things... Its actually horrifyingly slow, like minutes, mind you, you've lost consciousness before actual death, but you'd have 10's of seconds to contemplate your demise (and test how loud your clap is).

    Before morals were invented (pre 1967?) NASA did some tests on chimps' survival in near vacuum, and they were able to revive them after up to 3.5min of exposure.

    "For example, in 1965 a technician inside a vacuum chamber at Johnson Space Center in Houston accidentally depressurized his space suit by disrupting a hose. After 12 to 15 seconds he lost consciousness. He regained it at 27 seconds, after his suit was repressurized to about half that of sea level. The man reported that his last memory before blacking out was of the moisture on his tongue beginning to boil as well as a loss of taste sensation that lingered for four days following the accident, but he was otherwise unharmed."
  11. Jul 4, 2018 #10
    I totally agree with this horrifying information. It's just like at low pressures water boils quickly. *sigh*
  12. Jul 6, 2018 #11
    For who the marshmallow man? I suspect space would take your breath away, and make you burp and fart at the same time :)

    Oh and really hurt the ears; perhaps a little too quiet lol
  13. Jul 7, 2018 #12


    Staff: Mentor

    That you explode from the pressure difference is an old wife's tale that has been corrected by others. The point is you die - maybe you can get a few claps off before that - maybe.

    Last edited: Jul 7, 2018
  14. Jul 7, 2018 #13
    You're right, sorry for using the misunderstanding as a segway for an attempt at lame comedy. But at least I didn't insult old wives everywhere...or perhaps I'm misunderstanding the semantics ;)
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