# In a Bose-Einstein condensate, do the cooled particles lose weight? [closed]

If the elementary particles are cooled, they lose a weight?

• It is totally not clear what you are trying to ask. Perhaps, try to give a reference of what you are asking – Rishabh Jain Oct 4 '19 at 10:34
• Welcome New contributor user1785960! I've downvoted your question for the "it is not clear" reason. You might find the following link helpful: How do I ask a good question? – Alfred Centauri Oct 4 '19 at 10:36
• I tried to clarify the question. Sorry for problems with my English. – user1785960 Oct 4 '19 at 10:40
• As this question's answers explain gravity is working for BECs. – StephenG Oct 4 '19 at 11:09
• @StephenG: Is BEC have changed weight in relation to the weight before cooling? – user1785960 Oct 4 '19 at 13:27

Your question is basically in the comments whether BEC changes weight relative to before cooling.

A BEC is formed by cooling a gas of extremely low density to ultra low temperatures.

AS the gas cooles (by laser), the energies of the molecules change via rotational and vibrational transitions.

https://en.wikipedia.org/wiki/Emission_spectrum

The answer is yes, because during the cooling, particles, molecules constantly lose rotational and vibrational energies (due to the laser cooling), and thus because of the energy mass equivalence, the gas will lose mass.

When the gas forms a BEC, it will still have mass, and stress-energy thus it will still interact gravitationally.

• But this is not important. Typical experiments use alkali atoms that do not even have rotational degrees of freedom. Experimentally, the mass of the condensate will be indistinguishable from the sum of the atom masses. So the correct answer is: No, B-E condensation does not affect weight. – Pieter Oct 5 '19 at 9:56
• @Pieter are you suggesting that the laser cooling does not cause the atom/molecules to lose energy? – Árpád Szendrei Oct 5 '19 at 15:43
• Ice is lighter than water but is one mole of ice lighter than one mole of water? – Pieter Oct 5 '19 at 16:56
• @Pieter well I was talking about all of the atoms in the gas/BEC. Why the downvote? – Árpád Szendrei Oct 5 '19 at 16:57
• Because there is nothing special about the transition when it comes to weight. The molar weight is the same, at least it is not more different than how cooling something else affects its molar weight. Unmeasurable. – Pieter Oct 5 '19 at 17:03