I'm not really a science whiz, but I know lasers generally use photons to increase the kinetic energy of atoms in their path, thus raising the temperature. Now I know electrons have negative energy, but this is only in relation to being less than infinity if I'm not mistaken (https://chemistry.mcmaster.ca/esam/Chapter_3/intro.html#:~:text=When%20a%20stable%20atom%20is,the%20energy%20will%20be%20negative.) So my question is could a laser with negative energy suck the kinetic energy from an atom, thus cooling it and transfer into the gun (in which a tremendous amount of waste heat would be released), thus slowing down the atom and cooling down the energy of its target massively? If not, what laws of physics would this violate and how?

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    $\begingroup$ Laser cooling. $\endgroup$
    – AlexP
    Apr 4, 2021 at 17:07
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    $\begingroup$ Yeah, see, I thought about that, but then you realize it requires lasers from 6 different directions and can only be done on a microscale, which isn't really practical for a freeze ray. $\endgroup$
    – Strivs
    Apr 4, 2021 at 17:13
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    $\begingroup$ Photons are their own anti-particle, so none of those things you list in the title exist. $\endgroup$ Apr 4, 2021 at 17:43
  • $\begingroup$ @GrumpyYoungMan Are they? That's wild. $\endgroup$
    – DKNguyen
    Apr 4, 2021 at 17:57
  • $\begingroup$ The major issue here is that there's no such thing as "negative kinetic energy". If you want to transfer thermal energy, you either need to constrain individual atoms (like laser cooling) or have energy pass from the hotter object to a cooler one. You could supercool bullets and then shoot them at a person, but photons have no thermal energy to remove, as they are massless. So, the laws violated are the First and Second laws of Thermodynamics. $\endgroup$
    – jdunlop
    Apr 4, 2021 at 18:36

1 Answer 1


I'm not really a science whiz [...] I know electrons have negative energy, but this is only in relation to being less than infinity

In my chemistry book in high school the concept of energy levels for electrons was explained with this metaphor: imagine having a ladder, where you don't know how high it is above the ground, but you can only measure the distance between the steps.

With the above metaphor, negative energy applies because we have set the 0 at infinity from a nucleus, thus whenever the electron gets closer and loses energy it goes negative. The same is applied to gravitational field, where a 2 body system with positive total energy is unbound, negative total energy is bound.

However this is just a convenient way to deal with the fact that we "don't know" where to put the absolute 0 for energy.

For dark energy/matter, it's called dark because whatever it produces it, it doesn't interact with photons, aka light, of any sort. It follows that a laser of dark energy is a nonsense.

Last but not least, antiparticles annihilates when combining with particles, producing a gamma photon: that goes in the opposite direction of cooling something down, if it wasn't that, as stated in the comments, a photon is its own antiparticle, thus no annihilation at all.


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