Ludwig,

You're the one who asked "what's the point of it".

(I think the point is that we're a curious species - and although we don't know much in the scheme of things, the things we have worked out have all been accomplished because we are curious and we do see a point to investigation. Our technogies are testimony to that)

Btw, Einstein and people like him can't just pose something and bingo! it's true. His theories have been tested and tested, both mathematically and physically - you're arguing against the scientific process.

What are "technogies"?

That should have been "technologies".

Arrrrgh!

: )

Technogies are economies based on technology.

Similar to how a knowledge economy is techknowledgey?

Dear George,

You still seem to have an issue with the words “ two … planets or stars moving at constant velocity with respect to each other” being applied to the Sun and Earth.

Perhaps it was me being a little less than judicious with the terminology by using the words 'with respect to the Sun' instead of 'each other'.

However using your strict definition then where in the universe would we ever find “two … planets or stars moving at constant velocity with respect to each other”? Perhaps at a pinch a binary star system might fit the definition but little else.

I suspect that if an observer on the Sun were to be able to view the imaginary velocity vector arrow emenating from the Earth in the direction of its orbit it would remain unchanged right through the varying parts of the ellipse.

The fact is without outside references it would be impossible to detect whether is was the Sun or the Earth was the body in motion.

It is all a little fringe but fun none the less. If you have the time this paper has a decent crack at exploring the other side of the argument.

http://www.metaresearch.org/cosmology/speed_of_gravity.asp

Be that as it may it has been a good reason for me to explore the topic again so thank you

csteele,

I'm getting a "skeptic" twitch from that site : )

This is the guy that set it up.

http://en.wikipedia.org/wiki/Tom_Van_Flandern

Check out section on Le Sage's theory of gravitation and the speed of gravity.

"These claims were dismissed by mainstream physicists."

Dear Poirot,

Your whiskers should indeed be twitching, but the best answer of others to explain black hole gravity would appear to be virtual gravitons.

And I do like the waterfall analogy;

“To retain causality, we must distinguish two distinct meanings of the term “static”. One meaning is unchanging in the sense of no moving parts. The other meaning is sameness from moment to moment by continual replacement of all moving parts. We can visualize this difference by thinking of a waterfall. A frozen waterfall is static in the first sense, and a flowing waterfall is static in the second sense. Both are essentially the same at every moment, yet the latter has moving parts capable of transferring momentum, and is made of entities that propagate.”

But there are other parts of the paper that are questionable.

The part about the differences between the absolute speed of gravity and the speed of propagation through a gravitational field is also interesting.

Ah physics, when you think you have answered one question another 10 pop up.

I suppose that for a layman like myself comprehensible explanations are often found in less than specialist sites.