Results 1 to 14 of 14

Thread: temperature and speed of matter

  1. #1
    Join Date
    Jan 2010
    Location
    Wisconsin USA
    Posts
    2,698

    temperature and speed of matter

    If something is 6 trillion degrees centigrade, is this equivalent to a fraction of the speed of light. If so, what would the equation for calculating this speed?
    The moment an instant lasted forever, we were destined for the leading edge of eternity.

  2. #2
    Join Date
    Jul 2005
    Posts
    16,971
    In what way are you imagining equivalence? The mean speed of the particles?

    Grant Hutchison
    Blog

    Note:
    During life, we all develop attitudes and strategies to make our interactions with others more pleasant and useful. If I mention mine here, those comments can apply only to myself, my experiences and my situation. Such remarks cannot and should not be construed as dismissing, denigrating, devaluing or criticizing any different attitudes and strategies that other people have evolved as a result of their different situation and different experiences.

  3. #3
    Join Date
    Jul 2005
    Location
    Massachusetts, USA
    Posts
    21,800
    The Kinetic Energy of a gas particle is directly proportional to the Temperature of the gas or plasma made of those particles.
    Oxygen atoms at 273K (0C) travel about 460 meters per second on average. Hydrogen nuclei would be going 16 times as fast.
    Forming opinions as we speak

  4. #4
    Join Date
    Mar 2007
    Location
    Falls Church, VA (near Washington, DC)
    Posts
    8,304
    Quote Originally Posted by antoniseb View Post
    The Kinetic Energy of a gas particle is directly proportional to the Temperature of the gas or plasma made of those particles.
    Oxygen atoms at 273K (0C) travel about 460 meters per second on average. Hydrogen nuclei would be going 16 times as fast.
    Isn't that closer to 4 times as fast? Kinetic energy is proportional to velocity squared.

  5. #5
    Join Date
    Jan 2010
    Location
    Wisconsin USA
    Posts
    2,698
    Thanks all. That was enough info.
    The moment an instant lasted forever, we were destined for the leading edge of eternity.

  6. #6
    Join Date
    Jul 2005
    Location
    Massachusetts, USA
    Posts
    21,800
    Quote Originally Posted by Hornblower View Post
    Isn't that closer to 4 times as fast? Kinetic energy is proportional to velocity squared.
    Yes. In my quick response I saw it was linear with mass, but then I used the word fast instead of talking about energy.. Good catch, thanks.
    Forming opinions as we speak

  7. #7
    Join Date
    May 2003
    Posts
    5,947
    So, using antoniseb's figures, that means that yes, if you had hydrogen plasma a six trillion K, a naive calculation would have the protons moving at about 91% of the speed of light, and the electrons moving much faster than the speed of light. Obviously, under these conditions, you'd have to use the relativistic expression for kinetic energy to work out the actual mean velocity. We call this a relativistic plasma.
    Conserve energy. Commute with the Hamiltonian.

  8. #8
    Join Date
    Jan 2010
    Location
    Wisconsin USA
    Posts
    2,698
    Quote Originally Posted by Grey View Post
    So, using antoniseb's figures, that means that yes, if you had hydrogen plasma a six trillion K, a naive calculation would have the protons moving at about 91% of the speed of light, and the electrons moving much faster than the speed of light. Obviously, under these conditions, you'd have to use the relativistic expression for kinetic energy to work out the actual mean velocity. We call this a relativistic plasma.
    When a proton is moving at .9999999996 of the speed of light is this equivalent to a certain temperature or is a traveling object not the same as temperature? The hottest measured temperature is some number around 4 trillion degrees centigrade, but it seems to be that something moving at 0.9999999996 times the speed of light would be equivalent to something much hotter than the 4 trillion degrees. What am I missing?
    The moment an instant lasted forever, we were destined for the leading edge of eternity.

  9. #9
    Join Date
    Mar 2010
    Location
    United Kingdom
    Posts
    6,989
    Quote Originally Posted by Copernicus View Post
    When a proton is moving at .9999999996 of the speed of light is this equivalent to a certain temperature or is a traveling object not the same as temperature?
    Strictly the equivalence of average KE per particle and temperature is only true for systems in thermal equilibrium. It get hard to make it a meaningful concept for an isolated particle in motion. Plus it is usually measured in the COM frame of the system, since relativistic notions of temperature get complicated fast (see: https://www.nature.com/articles/s41598-017-17526-4, for example)

  10. #10
    Join Date
    Jan 2010
    Location
    Wisconsin USA
    Posts
    2,698
    Quote Originally Posted by Shaula View Post
    Strictly the equivalence of average KE per particle and temperature is only true for systems in thermal equilibrium. It get hard to make it a meaningful concept for an isolated particle in motion. Plus it is usually measured in the COM frame of the system, since relativistic notions of temperature get complicated fast (see: https://www.nature.com/articles/s41598-017-17526-4, for example)
    I had no idea!
    The moment an instant lasted forever, we were destined for the leading edge of eternity.

  11. #11
    Join Date
    Jan 2010
    Location
    Wisconsin USA
    Posts
    2,698
    Quote Originally Posted by Shaula View Post
    Strictly the equivalence of average KE per particle and temperature is only true for systems in thermal equilibrium. It get hard to make it a meaningful concept for an isolated particle in motion. Plus it is usually measured in the COM frame of the system, since relativistic notions of temperature get complicated fast (see: https://www.nature.com/articles/s41598-017-17526-4, for example)
    So is it not known whether something appears hotter, colder, or the same at rest or at relativistic speeds.
    The moment an instant lasted forever, we were destined for the leading edge of eternity.

  12. #12
    Join Date
    Mar 2007
    Location
    Falls Church, VA (near Washington, DC)
    Posts
    8,304
    Quote Originally Posted by Copernicus View Post
    So is it not known whether something appears hotter, colder, or the same at rest or at relativistic speeds.
    It is known. If that something is a body consisting of a vast number of particles which are jiggling with collective kinetic energy, it will be hotter with the jiggling at relativistic speeds than with them jiggling at very low speeds. If that something is a single particle in motion through space, once again temperature is not a meaningful concept.

  13. #13
    Join Date
    Jan 2010
    Location
    Wisconsin USA
    Posts
    2,698
    Quote Originally Posted by Hornblower View Post
    It is known. If that something is a body consisting of a vast number of particles which are jiggling with collective kinetic energy, it will be hotter with the jiggling at relativistic speeds than with them jiggling at very low speeds. If that something is a single particle in motion through space, once again temperature is not a meaningful concept.
    The article in nature seemed to imply that we really don't know this, but I am not sure that I am understanding this correctly. https://www.nature.com/articles/s41598-017-17526-4
    The moment an instant lasted forever, we were destined for the leading edge of eternity.

  14. #14
    Join Date
    Mar 2007
    Location
    Falls Church, VA (near Washington, DC)
    Posts
    8,304
    Okay, now I see your point, which involves a body for which temperature is a meaningful concept, and the question of whether or not extremely fast motion relative to that body changes an observer's perception of that temperature.

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •