Thread: the rotation speed of the earth..

1. The Earth's rotation is slowing down because of the moon moving further away.
One hundred years from now, the day will be 0.0015 seconds (1.5 milliseconds) longer than it is now.
Meaning, One hundred years ago, the day was 0.0015 seconds shorter than it is now.

1 second every 666.66 years
1500 seconds every million years
85,500 seconds every 57 million years (23.75 hours)

So does this mean that 57 million years ago the earth day was nearly 24 hours faster than it is today? In other words, it took just 15 minutes to rotate?

2.

3. I haven't checked your figures yet, but they are incorrect somewhere. You are right that the Earth is slowing down, but not at the average rate you mention. At the time of its formation, around 4.5 billion years ago, it was turning once in between six and ten hours.
You can look at certain corals from the Carboniferous, which show distinctive daily growth patterns, which vary annually also. From this we get confirmation of the the greater number of day in a year, and hence of the shorter day.
A final point: the Earth is not slowing because the moon is moving away from us. The Earth is slowing and the moon is moving away from us because of the tidal interaction of the two bodies.

4. Originally Posted by Roger
So does this mean that 57 million years ago the earth day was nearly 24 hours faster than it is today? In other words, it took just 15 minutes to rotate?
I think there's a mistake... earth's deacceleration rate isn't linear.

5. when you say billion, that's the USA billion right? which is 100 million? not the rest of the world, where 1000 x 1 million = 1 billion?

6. The American billion is 1000 million. 1,000,000,000. It always has been. The British billion, perhaps used in Australia at one time, is one million million. 1,000,000,000,000. This is falling out of use. There is no commonly used term for 100 million.

7. Thanks guys.

Is there any definite proof of the age of the planet? you'd think there would be, if not the age, at least some evidence that it's not 6000 years old as is suggested by christians. I mean 6000 and 4.5 billion years is quite a difference. There must be proof of that kind of age somewhere

8. Originally Posted by Roger
Is there any definite proof of the age of the planet? you'd think there would be, if not the age, at least some evidence that it's not 6000 years old as is suggested by christians. I mean 6000 and 4.5 billion years is quite a difference. There must be proof of that kind of age somewhere

There are fossils and rocks older than 6,000 years; that's the proof. The age of fossils and rocks can be determined measuring the quantity of carbon-14 on them, which is a radioactive isotope that decays trough time.

If it has a lot of carbon-14 is a relatively "new" thing, and if it has a reduced quantity it must be an "old" thing. This technique is used to measure the age of fossils up to 60.000 years old. Other similar radiometric techniques are used to measure the age of some rocks... which has led us to know that earth is aproximately 4.5 billion years old.

9. The earth's rotation IS slowing down but not because the moon is moving farther away, but rather because the earth is trying to become tidally locked to the sun.

10. at the beginning of the earth it was rotating 4,000mph.

11. Originally Posted by lance
The earth's rotation IS slowing down but not because the moon is moving farther away, but rather because the earth is trying to become tidally locked to the sun.
What does it mean to be "tidally locked"? Is that similar to how the moon revolves and spins at the same rate so as only one side is ever visible from Earth?

Thanks,
Jon

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