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Our moon has been slowly drifting away from Earth over the past 2.5B yrs
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Re: Our moon has been slowly drifting away from Earth over the past 2.5B yrs
#12> We found that the moon was around 60,000 kilometers closer to the Earth then [2.46 billion years ago] (that distance is about 1.5 times the circumference of Earth). This would make the length of a day much shorter than it is now, at roughly 17 hours rather than the current 24 hours. I wish they explained why the moon being that much closer would have such a dramatic effect on the day length. Can someone explain thi…
Sure. The earth is spinning faster than the the moon is going around the earth (earth rotates in one day, the moon goes around in about a month). When the tides transfer energy and momentum to the moon from the earth's spin, it slows down the earth's spin and gives the moon more energy. This moves the moon to a higher orbit, so it moves a bit farther away from us. The source of energy for the whole process is the ear…
If the moon wasn't drifting away and was in a static orbit, would the Earth's rotation slow and the moon's orbit speed up to the point where they're in sync?
Re: Our moon has been slowly drifting away from Earth over the past 2.5B yrs
#13> We found that the moon was around 60,000 kilometers closer to the Earth then [2.46 billion years ago] (that distance is about 1.5 times the circumference of Earth). This would make the length of a day much shorter than it is now, at roughly 17 hours rather than the current 24 hours. I wish they explained why the moon being that much closer would have such a dramatic effect on the day length. Can someone explain thi…
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Re: Our moon has been slowly drifting away from Earth over the past 2.5B yrs
#14A curious effect of this is that total solar eclipses past and future look different from total solar eclipses today. We live in a time when both the Sun and the Moon are roughly the same size (~32 arcminutes) when viewed from Earth. This coincidence results in the image we associate with total solar eclipses where the Sun’s corona is visible as a ring around the Moon.
Re: Our moon has been slowly drifting away from Earth over the past 2.5B yrs
#15> We found that the moon was around 60,000 kilometers closer to the Earth then [2.46 billion years ago] (that distance is about 1.5 times the circumference of Earth). This would make the length of a day much shorter than it is now, at roughly 17 hours rather than the current 24 hours. I wish they explained why the moon being that much closer would have such a dramatic effect on the day length. Can someone explain thi…
I was recently looking at some data about day lengths, and basically it all boils down to the fact that the earth doesn't orbit the sun in a perfect circle, which causes slight accelerations and decelerations; along with its wobble. That wobble as I understand is due to the effect of tidal forces due to the moons pull on our ocean.
Tropical/Solar days = 24 hours
But
Sidereal = 23 h 56 min 4.0905 seconds
Why the difference?
Because of those prior mentioned forces causing the location of the sun to be slightly out of alignment from where it started the day prior. Or something like that.
Tropic/Solar days are determined by the position of the sun, as per the name.
Sidereal are based upon the position of the stars. or so I understand.
To be clear. I am not an expert. I am just regurgitating what I read from NASA.
Re: Our moon has been slowly drifting away from Earth over the past 2.5B yrs
#16A curious effect of this is that total solar eclipses past and future look different from total solar eclipses today. We live in a time when both the Sun and the Moon are roughly the same size (~32 arcminutes) when viewed from Earth. This coincidence results in the image we associate with total solar eclipses where the Sun’s corona is visible as a ring around the Moon.
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Re: Our moon has been slowly drifting away from Earth over the past 2.5B yrs
#17A curious effect of this is that total solar eclipses past and future look different from total solar eclipses today. We live in a time when both the Sun and the Moon are roughly the same size (~32 arcminutes) when viewed from Earth. This coincidence results in the image we associate with total solar eclipses where the Sun’s corona is visible as a ring around the Moon.
In even 1000 years that would only be an offset 38 meters. That wouldn't meaningfully change the ratio.
Re: Our moon has been slowly drifting away from Earth over the past 2.5B yrs
#18A curious effect of this is that total solar eclipses past and future look different from total solar eclipses today. We live in a time when both the Sun and the Moon are roughly the same size (~32 arcminutes) when viewed from Earth. This coincidence results in the image we associate with total solar eclipses where the Sun’s corona is visible as a ring around the Moon.
Roughly the same size is understating it severely. They are uncannily similar in apparent size.
Re: Our moon has been slowly drifting away from Earth over the past 2.5B yrs
#19> We found that the moon was around 60,000 kilometers closer to the Earth then [2.46 billion years ago] (that distance is about 1.5 times the circumference of Earth). This would make the length of a day much shorter than it is now, at roughly 17 hours rather than the current 24 hours. I wish they explained why the moon being that much closer would have such a dramatic effect on the day length. Can someone explain thi…
Sure. The earth is spinning faster than the the moon is going around the earth (earth rotates in one day, the moon goes around in about a month). When the tides transfer energy and momentum to the moon from the earth's spin, it slows down the earth's spin and gives the moon more energy. This moves the moon to a higher orbit, so it moves a bit farther away from us. The source of energy for the whole process is the ear…
If the moon's orbit is increasing in radius, doesn't that mean its orbital velocity is decreasing? Which way is energy being transferred? This stuff confuses me.
Re: Our moon has been slowly drifting away from Earth over the past 2.5B yrs
#20Earlier quoted context omitted.
Sure. The earth is spinning faster than the the moon is going around the earth (earth rotates in one day, the moon goes around in about a month). When the tides transfer energy and momentum to the moon from the earth's spin, it slows down the earth's spin and gives the moon more energy. This moves the moon to a higher orbit, so it moves a bit farther away from us. The source of energy for the whole process is the ear…
If the moon wasn't drifting away and was in a static orbit, would the Earth's rotation slow and the moon's orbit speed up to the point where they're in sync?
Eventually, yeah; just as the Moon is tidally locked to Earth, Earth would be tidally locked to the Moon.
I don't know offhand whether that would happen before the Moon drifts too far away to remain in Earth's orbit, however.