Scientists have discovered an exoplanet that spins so fast its day is just eight hours long. Beta Pictoris b, which is 65 light-years from Earth, rotates on its axis at a whopping 62,000 miles per hour, about 50 times faster than Earth’s rotation rate (since the exoplanet is much bigger than the Earth, its day is a third as long). Scientists made this calculation using the same method meteorologists use to track earthly weather systems — the Doppler effect.
What is not generally known is that the Earth once had a much shorter day than it does now, due to its changing gravitational interaction with the Moon (and the Sun). Because of tidal friction — the loss of energy due to the gravitational tugging on Earth’s oceans — the Moon is gaining orbital energy at the cost of Earth’s rotational energy. As a result, the length of an Earth day increases. With the extra bit of orbital energy, the Moon’s orbit is increasing by about 4 cm each year and the length of a day increases by a couple of milliseconds per century. It doesn’t sound like much, but over millions and billions of years, it adds up. Computer simulations suggest that billions of years in the past, the Moon was so close to the Earth that an Earth day was a mere six hours long.
Intriguingly, an Earth-day that changes in duration is consistent with Gerald Schroeder’s reconciliation of a literal interpretation of Genesis 1 and an old Earth. Schroeder argues that the length of each Genesis day is 24 actual hours, but only measured from God’s perspective. From our earthly perspective, each of those days is a different length, ranging from billions to millions of years. It isn’t until humans appear on Day 6 that Genesis time comes to agree with Earth time. It would seem God chose a perspective for Genesis that was 24 hours, because that’s how long an Earth day would be once Adam appeared. For a detailed explanation of this reconciliation, see here.