Alex McColgan
speaker
29,301 appearances
104 recordings
1 series
first heard Nov 2024
last heard 2d ago
Alex McColgan’s voice in public audio — every appearance, attributed to the second.
Trend
recordings per month · last 12 monthsRecordings per month over the last 12 months — 68 in all, peaking in Aug 2026 with 11.
Appearances
allowing it to convert 600 million tonnes of hydrogen to 596 tonnes of helium every second.
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This sounds like a lot, but it's actually only a tiny fraction of the hydrogen available for fusion.
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Now, stopping for a moment to look at the big picture, this is very good news for us earthlings.
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It means, instead of annihilating itself in a giant thermonuclear explosion, the sun has been gently burning through its hydrogen stocks for around 4.6 billion years, and will continue to do so for at least a few billion more.
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It's only because protons are so slow at converting into deuterium that we are here at all.
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For fusion on Earth, on the other hand, it is bad news.
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It means the probability of proton-proton reactions happening, where we have much less plasma and much less time, is essentially zero.
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Indeed, the reaction has never been experimentally measured.
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In fact, looking at the problem in the most basic and fundamental way, it is statistically impossible to achieve proton-proton fusion on Earth in any meaningful way.
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So what are all these fusion researchers doing?
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Why do we even bother trying?
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Well, they are not attempting to fuse protons.
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Instead, they are trying to fuse alternative combinations of nuclei that are much more reactive.
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Back in the 1930s, Mark Oliphant, a student of Ernest Rutherford, conducted a series of experiments.
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He fired deuterium nuclei at one another, generating other exotic hydrogen and helium isotopes, and thus proving that heavy hydrogen nuclei could be made to react with one another.
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Today, fusion scientists favour a combination that was first put to use in the H-bomb.
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one that is 24 orders of magnitude more reactive than protons alone.
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It is deuterium, remember this is classic heavy hydrogen consisting of one proton and one neutron, and tritium, the even heavier isotope of hydrogen with one proton and two neutrons in its nucleus.
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The reason this combination is so much more reactive is that these extra neutrons lead to a greater strong force, and there is no need for one proton to undergo weak force mediated beta decay into a neutron.
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Now, deuterium and tritium aren't just more reactive than the protons that power the sun, they also give rise to different reaction products.
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Showing 1821–1840 of 29,301 · page 92 of 1466
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