Thread: How old is the earth in days?

1. You might be tempted to say it's 365.25 * 4,500,000,000 = 1,643,000,000,000.
That answer is incorrect for this purpose, because I am not talking about a 24-hour day. I am talking about a rotation of the earth. Since the earth spun faster in the past, there were more days, and the answer is larger than that.
If the number of days in a year is f(x) at year x, then it's just the integral from 0 to 4,500,000,000 of f(x) dx. I've looked up the formula and did the math, but my calculations got lost and I'm not sure they were right anyway. I think I got an answer between 2 and 3 trillion.

2.

3. There is no formula that you can directly apply to the problem. The rate at which the Earth's spin slows has not been constant nor is the change in this rate. The positions of Earth's land masses have an strong effect on this. Because of continental drift, this changes, so with some continental arrangements you get a larger tidal drag and more slowing than with others.

4. It would depend on your definition of Earth.

At one point the Earth would have been a sub millimeter speck of dust which could have spun dozens of times per second. Could be as high as 10^19 if you go back that far.

Do you mean once Earth became a planet? (clearing it's orbit)

Or when it became a comparable mass to what it is now? (say >90% mass)

5. Interesting question.Too many unknown variables including those implied in posts above. Also, another is the unknown mass of the Earth and length of the day before the formation of the Earth/Moon pairing.

6. 4

7. why would you want to know how old the earth is in days, given that the age of 4.5billion is probably ±1% (i.e. 45 million years) ?
seems like spurious accuracy to me

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