Eli5: how does geologic time work if days and hours were different billions of years ago?

787 viewsOtherPlanetary Science

So, if we say something is 1 billion years old, is that (365 spins on earth’s axis x 1 billion)? Is it (1 trip around the sun x 1 billion), or a different measurement? The answers to those change depending on how it’s calculated.

In other words, if I say I lived one year, that means 24 hr/day for 365 days/year in todays terms. Over time the earth’s orbit of the sun becomes faster and slower changing the meaning of a year. Also, as the earth spins faster and slower on its axis, a day in terms of hours is different relative to today. It breaks my brain.

What about the needs for adjustments for leap years? How does this influence radiometric dating? If a molecule degrades by 1 measurement every 300,000 years, the first 150,000 years are going to be different than the last half. If you want to pinpoint the halfway mark, where is it?

In: Planetary Science

11 Answers

Anonymous 0 Comments

Think of year as more of a scientific measurement than an actual year. It measured time that is a certain number of seconds that is easily quantifiable and always the same. They are not measuring how many times the earth has been around the sun, they are calculating how many total seconds have passed that it has existed.

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