Earth’s day was half hour shorter 70 million years agoUsing data from an ancient fossil shell, scientists have determined that 70 million years ago the Earth’s day was about 30 minutes shorter, and that a year comprised 372 days.
This result is not a surprise, as scientists have known for a long time that the day has been growing longer as the Moon’s gravity, producing tides, wears away at the Earth’s rotation. This data however is the most precise yet, and will allow scientists to better constrain not only the Earth’s changing rotation over time but the Moon’s orbit. As it slows the Earth’s rotation its own orbit around the Earth gets longer, pushing it farther away.
On Christmas Eve 1968 three Americans became the first humans to visit another world. What they did to celebrate was unexpected and profound, and will be remembered throughout all human history. Genesis: the Story of Apollo 8, Robert Zimmerman's classic history of humanity's first journey to another world, tells that story, and it is now available as both an ebook and an audiobook, both with a foreword by Valerie Anders and a new introduction by Robert Zimmerman.
The print edition can be purchased at Amazon. from any other book seller, or direct from my ebook publisher, ebookit.
The ebook is available everywhere for $5.99 (before discount) at amazon, or direct from my ebook publisher, ebookit. If you buy it from ebookit you don't support the big tech companies and the author gets a bigger cut much sooner.
The audiobook is also available at all these vendors, and is also free with a 30-day trial membership to Audible.
"Not simply about one mission, [Genesis] is also the history of America's quest for the moon... Zimmerman has done a masterful job of tying disparate events together into a solid account of one of America's greatest human triumphs."--San Antonio Express-News
Using data from an ancient fossil shell, scientists have determined that 70 million years ago the Earth’s day was about 30 minutes shorter, and that a year comprised 372 days.
This result is not a surprise, as scientists have known for a long time that the day has been growing longer as the Moon’s gravity, producing tides, wears away at the Earth’s rotation. This data however is the most precise yet, and will allow scientists to better constrain not only the Earth’s changing rotation over time but the Moon’s orbit. As it slows the Earth’s rotation its own orbit around the Earth gets longer, pushing it farther away.
On Christmas Eve 1968 three Americans became the first humans to visit another world. What they did to celebrate was unexpected and profound, and will be remembered throughout all human history. Genesis: the Story of Apollo 8, Robert Zimmerman's classic history of humanity's first journey to another world, tells that story, and it is now available as both an ebook and an audiobook, both with a foreword by Valerie Anders and a new introduction by Robert Zimmerman.
The print edition can be purchased at Amazon. from any other book seller, or direct from my ebook publisher, ebookit. The ebook is available everywhere for $5.99 (before discount) at amazon, or direct from my ebook publisher, ebookit. If you buy it from ebookit you don't support the big tech companies and the author gets a bigger cut much sooner.
The audiobook is also available at all these vendors, and is also free with a 30-day trial membership to Audible.
"Not simply about one mission, [Genesis] is also the history of America's quest for the moon... Zimmerman has done a masterful job of tying disparate events together into a solid account of one of America's greatest human triumphs."--San Antonio Express-News
A friend of mine, who studied under van Allen, once told me the tale of one of his exam questions. He was supposed to calculate the rate at which the Earth’s rotation is slowing. (Or was it the rate at which the Moon is getting farther from the Earth? Well, the rest of the story is more memorable, to me.) He chose to use conservation of energy between the Earth’s rotation and the Moon’s orbit.
The proper method turned out to be conservation of angular momentum. The problem was that the tides take up some energy as well as the magma, which is heated as the Earth is warped by the tidal action, so energy is not conserved with the changes in the two motions. Tidal heating is why there are volcanoes on Io.
The “war stories” that we get from scientists are a bit different than those from soldiers.
“Why did the chicken cross the Mobius Strip?”
(Big Bang Theory
https://youtu.be/j9u42WSaF04
0:07
So, that is why my nap times seem to be getting longer.
whew. I was worried that it was me.