I saw an animation of how if sun were to disappear in an instant, it would take earth still 8 minutes to feel the gravitational pull end. Is this true?
I do understand that Gravitational waves have the limitation of travelling at speed of light (do they though?) but is there a law that binds the space-time fabric to “act” faster than speed of light? I mean isn’t the Einstein’s rule limited to matter and not space-time, a fabric of universe.
Also, at relatively small distances like 1AU, wouldn’t the delay in the gravity’s effect vanishing be instantaneous? The gravitational waves might be limited by the speed of light (again, would they though?) but wouldn’t the delay in action of gravity mean that a simulated mass exists in center of our solar system, leading to formation of … Anti-matter? Or negative energy density??
Hi @Shan909 . Thank you for the question.
As best we can tell, gravitational waves, light, and “gravity” all travel at the same speed. For gravitational waves, we were able to measure this pretty well for GW170817, because some light (a gamma ray burst) and gravitational waves from the neutron star merger left at about the same time. They traveled across space for a long time (40 Mpc, or 120 million light-years) and arrived at earth within a couple seconds of each other.
I don’t think there would be any “instant” effects from gravity at 1 AU. 1 AU is about 8 light minutes, and information about a change in the local gravitational field should also travel at the speed of light.
Thank you for this explanation. It is interesting to note that we would keep on rotating around nothing even if the space time fabric has smoothened over the well that was sun’s mass. I wonder if this causes any spooky physics to show up. The fact that spacetime has to be limited by speed of light still surprises me.
In the context of the GW170817 event, I’ve been wondering about the interaction between gravitational waves (GWs) and electromagnetic (EM) signals. Since both were detected from the same neutron star merger, is there a way to ensure that the EM signal wasn’t influenced or accelerated by the passing gravitational waves?
More specifically, if spacetime is being distorted by GWs—creating ripples and temporary curvature—could this change the effective distance that light has to travel? I know the speed of light is a universal limit, but if space itself is being stretched and compressed, could light traverse those regions in a way that slightly alters its arrival time?
In other words, could EM signals effectively “ride the crests” of the gravitational wave distortions, potentially affecting our multimessenger measurements? Is this a known factor in multimessenger astronomy, or is the effect negligible?