Re: Two questions

Peter Webb wrote:
"Jonathan Silverlight" <jsilverlight@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx> wrote in message news:U3MFe0953OfCFwLo@xxxxxxxxxxxxxxxxxxxxxx


[snip]


There's no way of knowing, but some theories say not. Look at <http://www.space.com/scienceastronomy/mystery_monday_031201.html>, for instance.
It's known that there were more days in an Earth year several hundred million years ago, but that's usually ascribed to the tidal action of the Moon slowing the Earth. If the Earth had actually moved away from the Sun (due to mass loss from the sun, for instance) I can't think of any way to find out.


There are ways of finding out ... the sun's radiation goes as the square of the distance, and if we had been much closer it would have been much hotter.

But you also have to take into account that the sun became hotter with time. It did not emit that much radiation as today when it was younger.


Its hard to see how dinosaurs could have flourished if the earth had been (say) reaching 100 degrees C in the tropics, and indeed the fossil record appears to show a climate similar to now in broad terms - certainly the earth wasn't 10% closer or further away from the Sun 100 million years ago than it is today.

I would agree that 10% is probably too much. But I don't think we can rule out changes on the order of 1% or smaller.


Bye,
Bjoern
.

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