Speed of Gravity????

[turtl...@gmail.com]

Hello,

For years I've always wondered if it might be possible that the
universe could have a greater speed than that of light. And that
would be the speed of the propagation of gravity.

Here is the scenario which made me question which would be greater:

** If somehow, a star billions of times larger than our own sun, were
to magically appear one light year away, which would we experience
first here on earth? The light emanating from the star or its
gravitational effects? **

If you could provide an answer to this question I would greatly
appreciate it, as I'd finally be able to lay it to rest.

Thanks so much,
Denis Arsenault
Moncton, New-Brunswick, Canada

[Roberto Trotta]

Hi Denis

I'd think you'd see the light & feel the gravitational pull at the
same time - gravitational effects propagate at the speed of light
through spacetime, hence you'd experience them both simultaneously.

As an aside (which might not be related to your question), notice that
there are things out there that are moving away faster than the speed
of light (eg, all galaxies beyond redshift 1.6) and yet we can (and we
do) observe them. The trick is that they are not moving away in
spacetime, but rather they are being carried away from us by the
expansion of spacetime, hence this does not violate relativity.

Hope this helps!

Roberto