[George Knight]

George Knight asked the Naked Scientists:

Recently I was listening and the comment was made that gravity acts much like light.  

I seem to recall that it was said that "if the sun was plucked from the solar system it would take 8 minutes before the earth would begin  a straight trajectory rather than orbital".  

This may not be true. Would you please clarify?

Thank you.

What do you think?

[lightarrow]

George Knight asked the Naked Scientists:

Recently I was listening and the comment was made that gravity acts much like light. 

I seem to recall that it was said that "if the sun was plucked from the solar system it would take 8 minutes before the earth would begin  a straight trajectory rather than orbital". 

This may not be true. Would you please clarify?

Thank you.

What do you think?

A gravitational perturbation (e.g. a grav. wave) propagates at light's speed.
149.5*10⁶ km/299,792.458 km/s = 8 minutes 18 seconds.

[graham.d]

Yes, gravitational waves propagate at light speed (it is generaly believed) though we have yet to physically detect Gravitational waves. The concept of plucking away the sun as a idea to explain that we would not notice for 8 minutes is OK to a certain level, but it can lead to false conclusions if expanded upon too far. The fact that you can't actually do this is actually part of the laws of physics. You can (in theory) tow the sun away; you cannot just destroy its mass, only move it.