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Science is a bazaar, not a cathedral

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I don't know of any evidence that the original length of the Earth's year was any different than today's, but then, I wouldn't expect such evidence to be preserved after 3.9 billion years.

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Fossil record evidence (stromatolites etc.) indicates shorter day in the past, and that tidal influence has lengthened it. But that only goes back less than a billion years I think. (Strictly speaking I think it measured only the number of days per year, too.)

So the evidence we really want (year length, not merely days per year) isn't there.

However, as we can now measure orbital periods in other systems, a nice long term project would be to look for variations in known protoplanetary systems. If there are any such systems identified yet.

Unfortunately current postgrads working in this field might be leaving it to their grandchildren to actually publish the results...

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If Earth has migrated from a different orbit to its current distance from the Sun, then the Moon tagged along for the ride. One could approach the question from a standpoint of what one would expect to find at or near the lunar surface. For example, should older lunar impact craters exhibit certain characteristics if they were made by asteroids typically orbiting at different distances from the Sun?

Another approach could be to compare a model of Earth's structure--especially the core--with models of the solar nebula and the distribution of heavy elements during the time of planetary formation. If Earth had formed elsewhere, should its iron core be smaller or larger? Differently composed?

Finally, If the Earth were in a different orbit 1 to 2 billion years ago, shouldn't the geological record retain some evidence of climatic evolution tied to a move from the former to the current location? There are places on Earth where one can gain relatively easy access to rock layers that were formed 1 to 2 billion years ago. Let's have a look.

As to the question of whether or not Earth migrated to its current orbit from another, I look at the two options--formed here and survived because it's a stable orbit versus formed in an unstable orbit and was lucky enough to move to a stable orbit--and I lean in favor of the former. In the absence of persuasive evidence to the contrary, it seems more likely that a planet will remain in the stable orbit in which it formed versus moving from an unstable to a stable location.

Bill in Flag

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We have a very dynamic history to deal with, and much of its effects are un-postdictable.

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