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  • Fusion of hydrogen or helium normally requires at least the conditions found in the the cores

  • of stars . High temperatures and densities allow hydrogen and helium nuclei to get close

  • enough to fuse together into bigger nuclei and release a TON of energy, powering even

  • more fusion while releasing enough extra to power the star, or if you set this situation

  • up on earth, you might have a hydrogen bomb.

  • But it's actually possible for fusion to occur at temperatures much, much lower than

  • the core of the sun - like, room temperature, for example.

  • Now, I'm not talking about the infamouscold fusionof the 1980s that hasn't

  • been shown to work or involve any, well, fusion - no, I'm talking about the room-temperature

  • fusion of the 1950s that actually does work: fusion with the help of muons!

  • Nuclear fusion, of course, happens when atomic nuclei, like hydrogen nuclei , come close

  • enough together that their strong nuclear attraction can overcome their electric

  • repulsion, and they fuse together into a single, bigger nucleus - like helium .

  • This typically happens in a plasma, that is, a super hot soup of electrons and atomic nuclei,

  • where if it's hot enough every once in a while two nuclei bump hard enough into each

  • other to fuse . But fusion can in principle happen in regular, non-plasma molecules, too

  • - like the hydrogen molecule, in which two hydrogen nuclei are kept relatively near to

  • each other by sharing electrons . The nuclei don't stay separated a rigid distance apart,

  • though - they vibrate and wiggle and every so often, they can, in principle, get close

  • enough to fuse together.

  • But with hydrogen - or nitrogen, or oxygen, or pretty much all other molecules - this

  • happens exceedingly rarely (which is why our atmosphere, which has a fair amount of molecules,

  • isn't a giant fusion bomb).

  • However, things are different if you replace the electrons with particles called muons,

  • which are basically exactly the same as electrons except 200 times heavier . Muons, being

  • essentially heavy electrons, form atoms and molecules in almost the exact same way as

  • electrons, but since they're heavier, their orbits are much closer to the nucleus than

  • an electron with the same energy and angular momentum would be . And this means that atoms

  • and molecules held together with muons instead of electrons are about 200 times smaller,

  • and their nuclei are correspondingly about 200 times closer together.

  • And being closer together makes nuclei many many many times more likely to fuse together,

  • so much so that hydrogen molecules made with muons can fuse together at temperatures much

  • lower than the core of the sun - even room temperature!!

  • Which was predicted in 1947 and experimentally achieved in 1956 . Physicists have even managed

  • to achieve muon-aided nuclear fusion at temperatures close to absolute zero.

  • So at this point, you're probably asking yourself: if room-temperature nuclear fusion

  • exists, why aren't we using it to power modern civilization?

  • Well, while muon-facilitated fusion is indeed fully legit nuclear fusion at non-crazy temperatures,

  • there are some major problems which prevent it from being used as a power source.

  • First, muons don't live very long . Unlike electrons which have an in principle infinite lifespan,

  • after about 2 microseconds muons spontaneously decay

  • into an electron and some neutrinos, so if you're going to do anything with muons,

  • you have to do it real quick!

  • This turns out not to matter much for the purposes of facilitating fusion, but because

  • of their short lifespan, there aren't a ton of muons around - so if you want a reliable

  • supply of muons, you pretty much have to make them with a high energy particle accelerator

  • , which takes a lot of energy per muon - at best about 5 giga electron volts , or about 50

  • times the E=mc^2 mass-energy of a muon itself.

  • Now, luckily you don't need a muon for every single pair of hydrogen nuclei you want to

  • fuse, because after a pair of nuclei fuses into helium the muon can go off and help more

  • nuclei fuseand then help moreand moreand more….

  • EXCEPT, every so often , the muon doesn't - it'll get stuck as part of the newly fused

  • helium atom , and can't facilitate any additional fusing.

  • This means that each muon only helps an average of 150- fusions of nuclei before it gets stuck

  • . And since each fusion of nuclei releases about 18 mega electron volts of energy , this

  • means that, after 150 fusions, each muon facilitates an average of 2700 mega electron volts, or

  • 2.7 giga electron volts, of energy generation.

  • Which means that, unfortunately, the numbers don't add up - Remember it currently takes around

  • 5 GeV of energy to produce a muon, but each muon only generates about two and a half GeV

  • of energy before getting stuck to a nucleus.

  • That is, muon-facilitated fusion is a net consumer of energy (rather than being a source

  • of energy).

  • This is the best case possible with current technology, and the numbers are still off

  • by a factor of 2 before even reaching any sort of break-even where muon-facilitated

  • fusion could generate as much energy as it consumes.

  • And we'd need to be much better than just breaking even, energy-wise, to make a viable

  • commercial power plant.

  • Pretty much the only hope for muon-facilitated-fusion is to figure out how to make muons for less

  • energy, or figure out how to have less of them stick to the helium nuclei, or how to

  • unstick them once they're stuck - which are all hard problems limited by the unchangeable

  • physical properties of muons and nuclei, and so we've made quite slow progress in over

  • 70 years of research.

  • The summary is that muon-induced fusion exists, it's fascinating science, but it's not

  • going to be powering the world any time soon.

  • To dive deeper into the energy sources that DO power the world, I highly recommend checking

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  • how much energy mammals need to survive.

  • There's even a section about the fusion reactions that happen in the sun!

  • And thephysics of the everydaycourse as a whole gives a great overview of the physics

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Fusion of hydrogen or helium normally requires at least the conditions found in the the cores

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B2 fusion muon hydrogen energy fuse electron

Legitimate Cold Fusion Exists | Muon-Catalyzed Fusion

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    Summer posted on 2020/09/08
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