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So in my story, I'm trying to develop a plausible freeze ray. Now many people suggest liquid helium, but it seems to have a number of practical setbacks, such as being hard to obtain, needing vast quantities, and high pressure dispersion of it to actually freeze someone. Not to mention, a good portion of it would mostly likely evaporate into the air on impact. I suppose I could fall back on it if need be, but what about something more effective like Captain Cold's gun? The closest thing we have to that is laser cooling (https://youtu.be/SDqCx4FiJSo).

Laser cooling is the use of momentum from a photon from a laser to counteract on the movement of an atom, thus bringing it down to temperatures slightly above absolute zero. There are multiple methods of laser cooling, but the most common method is Doppler cooling, in which 2 lasers each on 3 axises are fired opposite each other (check the picture).

Laser cooling has been used to cool individual atoms, a gaseous cloud of atoms (https://arxiv.org/abs/1705.03421), and even a coin-sized object (https://news.mit.edu/2007/super-cool). The problem is that all these experiments were conducted in laboratories with controlled environments, namely that the atoms were in an optical cavity of sorts, heavy machinery, and still hasn't been tested on something around the size of a human. We're not trying to do a rigorous lab experiment here, we're trying to freeze a superhero (who's essentially a man-sized reptile) dead in their tracks at the pull of a trigger.

So with all this in mind, what's the best way to go about this?

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    $\begingroup$ Have you dismissed the obvious liquid nitrogen, why? $\endgroup$ – Rottweiler on market-day. Feb 5 at 1:31
  • $\begingroup$ You should be aware that the site likes one question at a time, you'll need to edit it down, and give us the specs of your super. $\endgroup$ – Rottweiler on market-day. Feb 5 at 1:40
  • $\begingroup$ @Tantalus' touch The problem with Liquid nitrogen is this: worldbuilding.stackexchange.com/questions/25541/… $\endgroup$ – Strivs Feb 5 at 1:46
  • $\begingroup$ Not to mention, freezing a whole person would use up a lot of it fast and require frequent refills. $\endgroup$ – Strivs Feb 5 at 1:47
  • $\begingroup$ Do you need to freeze them solid all the way through? What material are they made of.... basically are they human? If so, it'll take an awefull long time for the heat to be leached from them in any medium.. Tell us about your super (hero), that would help muchly. $\endgroup$ – Rottweiler on market-day. Feb 5 at 1:52
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I am afraid you can't laser cool a person.

As you point out, laser cooling works with individual atoms or small group of atoms in gaseous state, because they are easy to deal with on an individual basis and have a limited set of vibrational modes.

An individual is made by a lot more of atoms, and what's worse is that those atoms are not loose but bound in rather long chains. This means that the assembly has way more mode of vibration than the individual atom. It can happen that by stopping one atom in a chain you make the others shake more.

Maybe you can cool a person by using him/her as hot terminal of a thermoelectric junction (not directly has a junction because we are not metals)

The thermoelectric effect is the direct conversion of temperature differences to electric voltage and vice versa via a thermocouple. A thermoelectric device creates a voltage when there is a different temperature on each side. Conversely, when a voltage is applied to it, heat is transferred from one side to the other, creating a temperature difference. At the atomic scale, an applied temperature gradient causes charge carriers in the material to diffuse from the hot side to the cold side.

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  • $\begingroup$ There seems to be some optimism that this constraint might be released. Depending on the speculative nature of the fiction (superheroes?) it doesn't seem that excessive to suppose that one could go from triatomic molecules in gas phase to long -CH2- chains in a cell membrane. Still, laser cooling is much less efficient than laser heating, and visible light penetrates the body very poorly - this would be a ray to freeze someone's skin off, not cool down the quadriceps. $\endgroup$ – Mike Serfas Feb 5 at 14:12
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Neutrino pair production. This technology is normally used for the peaceful exploration of space, and I highly discourage this abuse of our interstellar space drives, but I understand exploration involves some exigencies. If you've ever taken a trip outside the Solar system, you've had time to study how the Gemino Drive works, but for the uninitiated: our technology catalyzes a simple reaction, photon = electron neutrino + electron antineutrino. Crucially, the catalyst provides the momentum to make this possible, which is also the propulsive force of the spacecraft. Because the electron neutrino's mass is so very small, it is possible to produce these pairs of particles from the energy of an ordinary thermal photon at warm temperatures. For cooler temperatures, the vibrational modes of the catalyst can be stimulated to provide additional energy for the reaction. Because the neutrino background is so cold, the reaction will proceed until the temperature of the cosmic neutrino background, 1.95 K, is reached. When the spacecraft is landed, this heat sink may provide sufficient energy to provide a backup source of electrical power using a simple heat engine, depending on external conditions.

Of course, no chemical catalyst will affect a neutrino reaction - we needed to develop megabarn halo nuclei with observable half-lives. Ordinarily, these are kept safely contained within our reaction chamber, produced from in vacuo interactions with the coherent neutron stream and immediately captured on the impeller plate. Nonetheless, our systems are designed to be vented to space for safety reasons. Opening these on a planetary surface would contaminate the chamber with atmospheric gasses and risk physical damage from compression, but in that time the catalyst nuclei could be accelerated into a beam and directed out the port. I shudder to speculate on the full range of effects if any personnel were struck, but they would include dramatic reduction in body temperature and unacceptably high radiation exposure as the catalyst decayed. It is unlikely that the directionality of the catalyst could be maintained after it left the chamber. Possibly, if a strong magnetic field were present at the target location, a beam of radio transmission could reestablish the nuclear magnetic resonance, causing the target to experience the same change of momentum as the impeller plate. Without this, there might still be some observable shock of impact before the catalyst nuclear spins become randomized.

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