How much has Earth drifted (inwards or outwards) from its orbit about the sun? Or has Earth has not moved at all, compared to, say, 1000 years ago? 10,000 years ago?
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1$\begingroup$ Are you referring to its eccentricity? Or do you mean how has its orbit changed since it was first created? ... $\endgroup$– lemonMay 18, 2015 at 18:23
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3$\begingroup$ The earth's orbit is the earth's orbit. How can it deviate from itself? Please explain your question in much more detail. $\endgroup$– WhatRoughBeastMay 18, 2015 at 18:26
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$\begingroup$ arxiv.org/abs/1209.5996 $\endgroup$– Count IblisMay 18, 2015 at 18:42
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1$\begingroup$ Related: physics.stackexchange.com/q/47805 and physics.stackexchange.com/q/74569 (the latter being more closely aligned with the intent of this question). $\endgroup$– Kyle KanosMay 20, 2015 at 13:51
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2$\begingroup$ See How fast is the earth-sun distance changing - the answer seems to be "1.2 +- 3.2 cm / year" - in other words, within the measurement error, it is not changing. Other sources (see same link) claim Earth moves away by up to 15 cm/year. $\endgroup$– FlorisMay 21, 2015 at 20:36
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1 Answer
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The mean radius of the earth's orbit has not changed perceptably in the last 1000 years, or even in the last 10,000 years. In the long run, though...
The dominant mechanism in the long run is the solar wind, which is estimated to cause a mass loss of 7-9 x 10^-14 per year. As solar mass is lost, conservation of angular momentum causes the earth's orbit to expand. Obviously this doesn't affect things much in the short run. In the long run, the earth will spiral gradually away from the sun as the sun's mass decreases. About 7 - 8 billion years from now the sun will have lost nearly half its mass, and the earth's orbit will have expanded to roughly 1.5 times its current value.
According to https://arxiv.org/abs/0801.4031, for several billion of those years the sun itself will have begun expanding at an accelerated rate as it enters its red giant phase. As it expands, it begins to exert increasing tidal forces to retard the earth's orbital velocity (slowing its orbital expansion and allowing the expansion of the sun to catch up), and at about 7.59 billion years the expansion will engulf the earth, which will then enter a decaying orbit and plunge to its Wagnerian doom.
answered May 20, 2015 at 17:54
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