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
Lets use an example in our solar system – Mars.
Mars has a different day length and year length – a Mars day is 24 hours and 37 minutes and a Mars year is 668.6 Mars days.
However you can still measure an Earth year on Mars. It wouldn’t really mean much for someone on Mars, being 355.5 Mars days, but it’s still 1 Earth year.
No imagine instead of Mars you have Earth in the distant past. If you take a current Earth year and apply it to past Earth it won’t match up with 365 past Earth’s days or maybe even its year, but it’s still a period of time we can measure.
So basically we are taking the current day/year length, ignoring the fact these values have changed, and just using it as a fixed length of time.
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