Alex McColgan
speaker
29,301 appearances
104 recordings
1 series
first heard Nov 2024
last heard 6d 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
The first surprise was that ordinary particles could only feel the weak force if they were left-handed, and antiparticles could only feel it if they were right-handed.
voice-verified
The concept of handedness, or chirality, is subtle and difficult to conceptualise for particles with mass,
voice-verified
But a loose analogy can be drawn with a particle's helicity, which describes whether a particle is spin up or spin down along its direction of motion.
voice-verified
In this analogy, a spin up particle is called right-handed, while a spin down particle is called left-handed.
voice-verified
The second, and even crazier surprise, was that right-handed antiparticles experienced a different strength of the weak force as compared to left-handed ordinary particles.
voice-verified
In practice, this means that the quantum probabilities for radioactive decay in ordinary nuclei are somewhat different from the probabilities of the analogous decay processes in antinuclei.
voice-verified
This fundamental asymmetry between particles and antiparticles was first observed in a 1963 experiment run by James Cronin and Val Fitch of Princeton University, who would be awarded yet another Nobel Prize for their discovery.
voice-verified
When this asymmetry was discovered, there was some hope that it would explain the baryonic asymmetry of the universe.
voice-verified
Perhaps these differences in the weak force were responsible for the abundance of matter and utter lack of antimatter around us.
voice-verified
But the maths didn't quite work out.
voice-verified
There simply wasn't enough of a difference between the strength of the weak force acting on particles versus antiparticles.
voice-verified
That was when physicists began to turn their attention to the strong nuclear force.
voice-verified
Theoretical models predicted that, just like in the weak interaction, there should be some differences in how left-handed particles and right-handed particles feel the strong force.
voice-verified
But antimatter just keeps surprising us.
voice-verified
Every experiment to date suggests that the strong force treats particles and antiparticles just the same.
voice-verified
This brings us to the last of the four fundamental forces and the subject of today's ongoing experiments at CERN, gravity.
voice-verified
To be honest, suggesting that gravity might treat matter and antimatter differently is kind of a long shot.
voice-verified
Think back to the popular legend of Galileo tossing stones of different sizes and materials from the Tower of Pisa.
voice-verified
They all fell at the same rate because the gravitational acceleration on Earth is 9.8 m per second squared, regardless of which object is falling.
voice-verified
Of course, the experiment works even better in a vacuum chamber.
voice-verified
Showing 2221–2240 of 29,301 · page 112 of 1466
← Previous
Next →