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Comment by dgsm98 | Hacker News Reader

Could someone explain to me why this does/does not break the first law of thermodynamics? Is more energy being created from less?

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No, think of it like burning oil. Imagine it took >1 barrel of oil's worth of energy to burn a barrel of oil. That would be inefficient. So, we're trying to find solutions to trigger that burning with less input energy.

They're not creating energy, they're basically releasing energy stored over from the Big Bang. Triggering that release with less input energy than output energy is an engineering problem.

Oil is a pretty good example here, some oils do require a lot of energy to burn if they are just sitting there in a puddle. They don't become efficient to burn until you make a modification like aerosolizing the oil and mixing with air or introducing a wick.

E = mc^2

Consume a small amount of mass, release a very large amount of energy due to the huge conversion factor. The first law isn't violated because the energy being released is coming from the annihilation of matter.

Mass and energy can in principle be converted given the right process. LLNL consumed the mass that produced the energy.

Dumb question but why does the velocity of light come into it? I understand how mass stores energy but never got the velocity of light part.

If you imagine (rest) mass to be a special form of energy to begin with, you're already 99% there. The fact that the speed of light squared is used as a conversion factor is superficially due to the way our units system is constructed, and in a deeper way it is due to the fact that fundamental properties of the universe are reflected in all of its fundamental processes (so, in a way these are also conversion factors in the actual mechanics of the universe).

The short answer is that it's a unit conversion factor. Physicists often work in units where c = 1, and then the equation becomes E=m multiplied by a unit conversion term.

Releasing more energy than what's put in to run the facility is a necessary property of all power plants. It costs energy to mine and process fossil and fission fuels, it costs energy to produce and maintain solar farms. None of this breaks thermodynamics, because none of this is reversing the flow of entropy. Energy is released, it's not created out of nothing.

In this specific case, hydrogen atoms are fused together, which is a reaction that releases energy because the resulting combined atomic nucleus is at a lower energy state than the atoms that went in. This technically holds true for fusion up until you get iron nuclei, with heavier atoms than iron requiring energy to be put into the reaction when fusing. This is the other side of the equation, which we are already using for nuclear fission plants.

Bashing nuclei together hard enough to overcome their innate repulsion is where most of the input energy is going in fusion reactors. It is comparable to the concept of activation energy in chemical reactions.

Keep in mind that this announcement does not cover the total energy cost of running the reactor, "only" the theoretical amount of energy released into the chamber by the ignition laser. So we're a long, long way off from achieving what they call "unity" (an input/output ratio of 1:1) in practical terms. In theory, fusion reactions achieving practical unity can be self-sustaining. Although this specific way of triggering a fusion reaction is not continuous, it could theoretically be re-worked into a permanently running reactor that is pulse-driven in the same way an internal combustion engine is.

They're converting mass into energy, so it's conserved. The problem they're trying to overcome is that the energy it takes to convert the mass into energy is more than the energy they get out.

At this point it sounds like the actual energy they put in is less than they get out, but the energy it takes to put the energy in still makes it a loss overall.

To put it simply, a huge amount of energy is used to produce so much heat and pressure, that the following occurs:

For every 1 deuterium nucleus involved, it fuses with 1 tritium nucleus => producing 1 helium nucleus, 1 free neutron, and 17.6 MeV of energy.

The energy released then causes more deuterium and tritium to fuse, producing more energy, and so on, in a chain reaction.

The goal, in order for this to be used to produce electricity for consumption, is for us to be able to kick start this process by introducing less than 17.6 MeV of energy per deuterium-tritium pair, so that after you account for the energy spent to fuse those atoms, there's a net energy left over for us to use.

Put even more simply, we're throwing heat/pressure at atoms, to cause them to fuse, and in the process convert some of that mass to energy.

Because mass is being converted to energy.

Is it though?

Yes

Somewhat similar to internal combustion engine where a small energy of a spark causes a reaction which produces much more energy - which comes from fuel.

Energy is released in the fusion reaction just like in an H bomb. The "more energy out then in" thing is about the difficulty of creating a fusion reaction that's not a bomb. It takes a large amount of energy, typically more than you're able to release from the reaction.

Others will have better answers, but if you just think about it, exploding a nuclear device emits a lot more energy than it took to release it. It’s a conversion, you’re not violating anything.

Obviously causing a nuclear explosion is not a very good way to generate energy. :)

It converts something into energy. In this case fuel mass.

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