Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

This is probably going to sound retarded, but

  1. Dec 5, 2004 #1
    Is there a limit to how high you can heat something?
    If not (or if only limited by the amount matter - energy in the universe), then why is there are limit on cooling?

    In our daily frames of reference the rest of the universe is moving (planets orbiting, galaxies spinning etc...). If we are to accelerate towards the speed of light for a certain time and then drop out of it, all the frames of reference 'slower' than ours would seem to have 'aged' more.
    Is there a way to go slower, or even to the point of stopping so that the rest of the universe doesn't age but we do?. Would this be if we accelerated everything but us to the speed of light?

    Sorry for the dumb questions, I'm just sitting in this internet place in Madrid waiting to catch my flight home in a few hours and I'm bored.
  2. jcsd
  3. Dec 5, 2004 #2
    The only conceivable upper limit to temperature is an initial temperature of the Universe during the big bang.

    As for your second question... I don't understand "stopping".
  4. Dec 5, 2004 #3
    About the first question- there is no limit as to how much you can heat something.
    The limit as to how much you can cool it, simply comes from the fact there is no such thing as "cold". There is only heat, wich is a form of energy.
    Long story short, when you've taken all the heat from a body, well there is nothing left, and you can therefore not cool it(= take more heat out) anymore.
    However, there is no problem in heating a body more and more. You're just adding more and more energy.

    About the second question- I guess it has to do with General Relativity, and I don't know too much in that. However, I can't see anything wrong in your conclusion. Of course, that means you'd have to accelerate the entire universe... good luck with that.

    Oh, and there's no such thing as a dumb question. There's only a stupid answer.
  5. Dec 7, 2004 #4
    Thank you two.
  6. Dec 8, 2004 #5
    "Of course, that means you'd have to accelerate the entire universe... good luck with that."

    That's not what he's saying.

    We are currently moving very very fast. If we was to slow down, we would age slower.
  7. Dec 8, 2004 #6
    The slower you go, the more you would appear (to others moving faster) to be aging FASTER. Think of the twins paradox where one twin is flying through space at a high speed, and upon returning is younger than the twin that stayed on earth. (therefore the non moving twin ages faster)

    The faster you go, the slower time appears to pass to others looking on at you from stationary(or slow moving) positions.

    So if you were going at speeds approaching c, then everything around you appears to be going slower.
    What I think blip was asking is that if everything around you was going at speeds approaching c (as in all of the planets, stars etc) and you were stationary, then from your point of view, the universe seems to be aging very slowly, compared to you. I guess the problem is 1) how would you accelerate the whole universe and 2) find a place to be stationary!

    Also, nothing can go *at* the speed of c, in theory we can get to .99999*c but no further.

  8. Dec 8, 2004 #7
    If you are "stopping", and the rest of the universe is accelerating, that would be the same as you accelerating in the opposite direction.

    Take note that the theory of special relativity (and I'm pretty sure general as well) does not include any statements on the direction of speed or acceleration when talking about time and length dilatations. Otherwize, you could construct a "preferred" frame, which should be impossible.

  9. Dec 8, 2004 #8
    Hmm, maybe I'm a little confused, but there is no limit on cooling or heating. You can continue to take away heat or keep adding heat infinitely, but you can not decrease or increase temperature infinitely. There is a limit.
  10. Dec 11, 2004 #9
    Um, yes, there is a limit to how much you can cool something. Heat is defined as the kinetic energy of the molecules that comprise a substance. When every single one of the atoms is completely motionless, the temperature of that substance will be 0ºK, and would define a complete lack of kinetic energy. There is no way to further lower the temperature.

    As for an upper limit, theoretically there is none. However, when you consider that suns are the hottest things in our universe right now, we could define the hottest sun as being the uppermost heat limit, since we currently have no means of getting anything to be nearly as hot.
  11. Dec 11, 2004 #10


    User Avatar
    Science Advisor
    Gold Member

    There is a theoretical upper limit, it is called the Planck temperature. It is really hot.
  12. Dec 11, 2004 #11
    The upper limit to heat may be just before an atom gets to the speed of light, that is, at whatever such temperature that causes the atom to move so fast that it becomes light there you would theoretically have your limit, I don't know know if anyone posted that already I'm tired of reading so much, that's an awesome question by the way, never thought about it.
  13. Dec 11, 2004 #12
    The OP asked if there are limits on cooling and heating...the answer to that is no. However, like Chronos and others mentioned, there are upper and lower limits on temperature.
  14. Dec 11, 2004 #13
    I was debating this the other day myself and my friend and I came to a conclusion.
    There is a limit of how "cold" something can get since as an atom becomes "colder" the electrons "slow" down. Absolute Zero is the min temp. that electrons will move at. We also came to the conclusion that it would be impossible to "see" or know when the atom was at absolute zero since we would have to use some sort of indirect energy to mesure the elctrons wavelenghts, this would cause the electron to leave its ground state again and would no longer be in absolute Zero.
  15. Dec 12, 2004 #14


    User Avatar
    Gold Member

    There is no limit to how many layers of paint you can coat a chair with, but there sure is a limit on how many you can remove.

    Palindrom has wrapped the answer up in a neat package.

    In reality, there is no such thing as "cooling"; there is only the removal of heat. Your air conditioner does not "cool" - it moves heat from the inside of your home to the outside.

    If this seems to be bifurcating bunnies, consider the effect: your air conditioner will stop being effective if the temperature outside is as hot as the heat coming out of the A/C. If the coils cannot dump their heat to the outside air, the A/C will not deliver cool air inside. The flow of meaningful energy exchange is only one direction, and that's inside to outside.
    Last edited: Dec 12, 2004
  16. Dec 12, 2004 #15


    User Avatar
    Gold Member

    1.4 * 10^32 Kelvin
  17. Dec 13, 2004 #16
    I'm fairly sure of it now, more heat makes things move faster, but things can't move faster than light according with what we know so there ought to be a point at which more heat doesn't add to more heat but adds to more light given off from a super hot region, such as with the sun. Is that really it cronxeh?
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook