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2020-09-01: How Do We Know What Stars Are Made Of?

  • 03:56: One of the most severe is that the Sun is full of free electrons - electrons that were stripped from their atoms due to the intense heat.
  • 04:22: Once it gets close to the surface, material is much less dense, so there are fewer free electrons to do the scattering.
  • 04:49: And if free electrons are good at stopping photons in their tracks, these atoms are even better.

2020-01-06: How To Detect a Neutrino

  • 05:58: ... ♪ That draws these free electrons to the walls of the tank, which lets us trace out the path of the ...

2019-02-07: Sound Waves from the Beginning of Time

  • 02:06: but no photon is safe from a free electron.
  • 05:26: ... free electrons were able to interact with any frequency of light, electrons bound into ...

2016-03-30: Pulsar Starquakes Make Fast Radio Bursts? + Challenge Winners!

  • 03:18: At this time, the universe was full of plasma, atomic nuclei, and free electrons.
  • 03:27: You see, free electrons are really, really good at getting in the way of photons.

2016-03-09: Cosmic Microwave Background Challenge

  • 00:37: Free electrons were captured by protons to form the very first atoms.
  • 02:53: That plasma was effectively opaque because photons couldn't travel far without bouncing off all those free electrons.

2015-03-25: Cosmic Microwave Background Explained

  • 03:58: With no more free electrons to redirect the light, the universe became, for the very first time, transparent.
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