The Earth rotates completely once every 24 hours, but it’s getting slower and slower as the Moon moves further away. However, when the planet was only around 2-and-a-half billion years old that wasn’t the case and a day here was only 19.5 hours.
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00:00The Earth rotates completely once every 24 hours, but it's getting slower and slower
00:08as the Moon moves further away.
00:10However, when the planet was only around 2.5 billion years old, that wasn't the case,
00:14and a day here was only 19.5 hours.
00:17Experts say that was a constant for around 1.6 billion years, and now they might finally
00:22know why.
00:23Despite being nearly 240,000 miles away, the force the Moon exerts on our planet is substantial.
00:29After all, it's responsible for tidal effects that we can witness every day.
00:32But experts say that its pull on Earth is also counteracted by atmospheric forces exerted
00:36on us by the Sun.
00:38In fact, the Sun's force is so powerful, University of Toronto researchers say a day
00:42on our planet would be 60 hours at this point if only the Moon was affecting our spin.
00:46So how is Earth held in a constant 19.5 hour day for so long?
00:50Well, the researchers say that our former atmosphere played a big role.
00:53A warmer atmosphere means it was larger, and larger things tend to spin slower.
00:57However, experts say that resonance, or when waves move through the warmer and larger atmosphere
01:02at a particular altitude and velocity, synchronize.
01:05And via computer simulations, they were able to visualize that synchronicity with the waves
01:09traveling around the planet at a speed perfectly divisible by the just under 20 hour day length.