Temperature and the kinetic energy of everything

Click For Summary

Discussion Overview

The discussion revolves around the relationship between temperature and kinetic energy, particularly in the context of motion relative to the Earth and the implications of kinetic energy on temperature in various scenarios. Participants explore concepts related to particle motion, temperature measurement, and specific examples like waterfalls and Bose-Einstein condensates.

Discussion Character

  • Exploratory
  • Debate/contested
  • Technical explanation

Main Points Raised

  • One participant suggests that the kinetic energy of particles is related to temperature, proposing that increasing particle movement raises temperature.
  • Another participant counters that only unordered kinetic energy is linked to temperature, and that a combined motion of an object does not affect its temperature.
  • A question is raised about whether a box of water would feel hot if touched while moving at a velocity of 0 relative to the Earth's rotation, with a response indicating that drag from the water would heat the contact area.
  • There is a discussion about the temperature difference in a waterfall, with one participant questioning if a gain in kinetic energy that is not random increases temperature.
  • One participant mentions that temperature is determined by the width of the velocity distribution of particles, not just their velocity, and relates this to the creation of Bose-Einstein condensates.
  • Another participant challenges this view by stating that in Bose-Einstein condensates, the actual velocity of atoms is extremely low, emphasizing that it is not solely about the width of the velocity distribution.
  • Experiments involving molecules cooled to low temperatures while still moving fast relative to the lab are mentioned, highlighting the complexity of the relationship between motion and temperature.

Areas of Agreement / Disagreement

Participants express differing views on the relationship between kinetic energy and temperature, with no consensus reached on several key points, including the effects of relative motion and the definitions of temperature in various contexts.

Contextual Notes

Some statements rely on specific definitions of temperature and kinetic energy, and the discussion includes unresolved questions about the implications of motion on temperature measurement.

DLeuPel
Messages
56
Reaction score
2
Earth rotates, it also orbits the Sun, the Sun orbits the galaxies and these have they’re own velocities as well. We know that the kinetic energy is measured by its velocity, and also that kinetic energy is related with temperature. By this I mean that the movement of particles are a measure of they’re temperature, meaning that if you were to make they’re movement faster, you would then increase they’re temperature. But these particles have already a velocity and a kinetic energy, even tho they look stationary to us.

It might be possible that that high amount of energy , we cannot notice it because we have are under the same effect as say a box of liquid water. Now my question comes here, if I where to have velocity 0 with respect to the rotation of Earth, would that box of water molecules be hot if I happen to touch it for an instance ( let’s say that the top part is open in a way that I can put my hand without effort since it is at an instant ). This can be achieved if I where to impulse myself in the contrary direction of the Earth’s rotation and having the exact same speed as the orbit but with contrary directions of the velocity. I guess it would also mean that air is hot as I touch it as well.
 
Science news on Phys.org
DLeuPel said:
and also that kinetic energy is related with temperature
Only unordered kinetic energy is linked to temperature. A combined motion of the whole object does not.
DLeuPel said:
meaning that if you were to make they’re movement faster, you would then increase they’re temperature
Not necessarily.
DLeuPel said:
if I where to have velocity 0 with respect to the rotation of Earth, would that box of water molecules be hot if I happen to touch it for an instance
No. If you move fast relative to the water your hand would experience a lot of drag from the water, however, and friction would heat up the contact area quickly.
DLeuPel said:
This can be achieved if I where to impulse myself in the contrary direction of the Earth’s rotation and having the exact same speed as the orbit but with contrary directions of the velocity.
I'm not sure what you mean here.
 
mfb said:
I'm not sure what you mean here.
Instead of orbit, I should have written rotation. By this I mean that you don't rotate with the Earth anymore.
Also, a waterfall has a lower temperature at its top than at its bottom. Shouldn’t this mean that a gain in kinetic energy that is not random kinetic energy increases temperature ?
 
The water gets warmer when it is stopped at the bottom and the kinetic energy from the falling water is converted to thermal energy. Directly before hitting the bottom it is not warmer (it actually tends to be a bit cooler from evaporation, but that is a different topic).
 
  • Like
Likes   Reactions: davenn, DrClaude and russ_watters
I once read that it is not the velocity of particles that determines temperature, but the width of the velocity distribution. Thus a bunch of atoms all moving as a cluster in perfect sync would have a temperature of 0K. I suspect this is how they use lasers to create Bose-Einstein condensates with temperatures close to absolute zero.

Interesting to speculate how this picture might change at relativistic velocities.
 
Rob Lewis said:
I once read that it is not the velocity of particles that determines temperature, but the width of the velocity distribution. Thus a bunch of atoms all moving as a cluster in perfect sync would have a temperature of 0K. I suspect this is how they use lasers to create Bose-Einstein condensates with temperatures close to absolute zero.
No. In BEC, the actual velocity of the atoms is extremely low. It is not just a question of the width of the velocity distribution.

There are experiments where molecules are cooled to very low temperatures in the sense of the width of the velocity distribution, but where they are trapped in a circular ring (a bit like in a particle accelerator) such that the molecules are still going fast with respect to the lab, but not with respect to each other.
 

Similar threads

  • · Replies 10 ·
Replies
10
Views
2K
  • · Replies 16 ·
Replies
16
Views
2K
  • · Replies 7 ·
Replies
7
Views
2K
  • · Replies 4 ·
Replies
4
Views
3K
  • · Replies 4 ·
Replies
4
Views
2K
  • · Replies 4 ·
Replies
4
Views
2K
  • · Replies 2 ·
Replies
2
Views
2K
  • · Replies 17 ·
Replies
17
Views
3K
  • · Replies 23 ·
Replies
23
Views
3K
  • · Replies 10 ·
Replies
10
Views
2K