From the May 2012 issue

If the Sun suddenly disappeared, it would take about eight minutes for Earth to become dark (due to the speed of light). How long would it take to feel the absence of the Sun’s gravity?

John Boliek, Hockessin, Delaware
By | Published: May 29, 2012 | Last updated on May 18, 2023
If the Sun were to disappear, we would feel the absence of its gravity in the same amount of time it takes to see the lack of sunlight — about 8 minutes. Credit: Astronomy: Roen Kelly
According to Albert Einstein’s general theory of relativity, if the Sun were to suddenly disappear, Earth would feel the absence of the Sun’s gravity in the same time it would take for it to “feel” the absence of the Sun’s light. So, about eight minutes. That’s because removing the Sun would launch a set of gravitational waves from its location that would carry the information about the Sun’s absence to Earth; according to our current understanding, gravitational waves travel at the speed of light. The reason for this coincidence is that, as far as we know, both electromagnetism (i.e. light) and gravity have what’s called “unlimited range” — that is, the strength of either force declines by the distance to the source squared. — Marc Kuchner, NASA’s Goddard Space Flight Center, Greenbelt, Maryland