Alex McColgan
speaker
28,638 appearances
102 recordings
1 series
first heard Nov 2024
last heard 6d ago
Alex McColgan’s voice in public audio — every appearance, attributed to the second.
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recordings per month · last 12 monthsRecordings per month over the last 12 months — 66 in all, peaking in Aug 2026 with 11.
Appearances
Under these conditions, the trapped antihydrogen atoms almost never collide or annihilate with atoms of ordinary matter.
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Instead, they can more or less just float around the chamber for minutes or longer.
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But, as the magnetic fields used to vertically trap the antihydrogen atoms are weakened,
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This random floating eventually allows the anti-hydrogen atoms to escape through either the top or the bottom of the chamber, where they can collide with a wall of apparatus, annihilate with some ordinary atoms and release a small burst of light.
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In the Alpha experiment, this happens over the course of about 20 seconds.
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The theory behind the experiment is that if gravity really pulls antimatter downwards, more of the antihydrogen atoms escape through the bottom than the top.
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The stronger the gravitational force, the more atoms escape through the bottom.
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The simulations the Alpha team ran showed that under normal gravitational attraction, about 85% of the antihydrogen atoms should escape through the bottom, whereas only 20% of them would escape through the bottom if gravity pulled antimatter upwards.
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If there were no gravitational force at all, the simulation showed a more even distribution of 55% escape through the bottom, probably only differing from 50% due to asymmetries in the experimental apparatus itself.
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What did the actual experiment find?
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Well, roughly 75% of anti-hydrogen atoms escaped through the bottom of the chamber, showing a clear preference for downward pulling gravity.
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As any thorough scientist would, the Alpha team repeated this experiment to collect a variety of data points that could tell a more complete story.
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They redid the procedure under various levels of magnetic field bias, which applied external upward or downward magnetic forces on the anti-hydrogen atoms.
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On this graph, a bias of minus 1g means that enough magnetic force is applied to counteract normal gravity, while a bias of plus 1g means that an extra g of magnetic force is applied to push the anti-hydrogen atoms downward and so on.
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The team made predictions through simulations for each bias, and for various possible gravitational interactions, which produced the orange, green and purple curves shown here.
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As you can see, the experimental data points shown in blue best match the orange curve, which represents the normal simulation, where gravity pulls antimatter downwards.
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but because the data falls just a bit below this curve, the best fit gravitational acceleration was only 0.75g, three quarters of the strength of gravity acting on ordinary matter.
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Does this mean that gravity affects matter and antimatter particles differently after all?
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Not necessarily,
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Let's have a look at the error bars.
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Showing 1601–1620 of 28,638 · page 81 of 1432
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