Friday is here, and the 'A Taste of Science for the Weekend' corner is back — number 97.
This time: the strange physics of nuclear fusion, quantum tunneling, and billions of dollars in investment.
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Unlike the familiar, long-established process of nuclear fission — in which atomic nuclei split apart in a chain reaction and release energy — nuclear fusion works in the opposite direction: atomic nuclei merge together and release energy.
But this seemingly minor difference is enormously significant. Nuclear fusion releases 9 times more energy than fission, and 6 million times more than oil, which is why it is considered the holy grail that could solve the global energy crisis.
Commercial nuclear fusion would provide unlimited energy that could be used for virtually anything — from cleaning the oceans and the atmosphere to synthesizing rare elements in the laboratory.
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The nuclear fusion process is fascinating, and it is made possible by some of the strangest principles in quantum mechanics.
Atomic nuclei repel each other as a result of Coulomb's law, which states that particles carrying the same electric charge repel one another like magnets.
Yet the protons that make up an atomic nucleus cling tightly to one another despite carrying identical electric charges — because at the vanishingly small distances between them, the strong nuclear force comes into play, binding them together with a force far greater than the electromagnetic repulsion.
To cause atomic nuclei to fuse, they must be brought to that vanishingly small distance from each other — but achieving such proximity seems impossible due to electromagnetic repulsion.
To overcome this repulsion, pressure and temperature must be raised to millions of degrees, causing atoms to break apart into plasma and driving nuclei to move at tremendous speeds and collide with one another repeatedly.
But even these collisions are not enough — and that is where a strange phenomenon called quantum tunneling enters the picture.
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According to quantum theory, a particle's position in space is not absolute; rather, it is determined by a probability wave describing its path of motion. A peak in the wave represents a high probability of finding the particle there if we look, while a trough represents a low probability.
If a particle is very close to a barrier, its position probability wave may pass directly through the barrier — and there is a tiny chance that the particle will suddenly appear on the other side!
In the context of fusion, this means that the more collisions we drive between nuclei, the more nuclei will appear on the far side of the repulsion barrier, where the strong nuclear force takes over and fuses them together. When such a merger occurs, a tiny fraction of the matter itself vanishes and is converted into pure energy.
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The turning point in nuclear fusion is that in recent years, private capital worth billions of dollars has been flowing into the field — driven by commercial potential, not just government funding for research projects.
The current approaches include magnetic confinement in a vacuum, in which a magnetic ring cooled to near absolute zero uses magnetic repulsion to compress the hot plasma that floats in a vacuum at its center.
In the video you can see part of the assembly process for the vacuum vessel of the ITER fusion reactor, currently under construction in southern France through the collaboration of teams from 35 countries.
Another approach is inertial confinement, in which many high-powered laser beams are focused for a fraction of a second onto a tiny grain of material floating in a vacuum.
In both methods, the temperature must reach an almost unimaginable 150–300 million degrees — far above the temperature at the Sun's core, which stands at 15 million degrees.
The reason is that laboratories on Earth lack the immense pressure that exists naturally at the Sun's core due to its enormous mass.
Although nuclear fusion is already an established reality, the race now is to achieve fusion that produces more energy than the entire facility consumes — not merely more energy than was invested directly in the fusion process itself.
Shabbat Shalom 😊
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Video credit: ITER
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