Tom Dempsey
Chadds Ford, Pennsylvania
This can be a implausible query, and the reply highlights a few of the most counterintuitive facets of the speculation of normal relativity. The brief reply isn’t any, however let’s delve deeper into just a few of the unusual issues that occur when objects strategy the pace of sunshine.
To an outdoor observer, as an object falls towards the event horizon (the purpose of no return the place not even gentle can escape the gravitational pull of a black hole), two results come into play. As gentle leaves the excessive gravitational discipline surrounding the black hole and reaches the observer — who’s in a decrease gravitational discipline — it loses power. So, as a result of gentle turns into extra purple at decrease energies, the thing appears to get redder and redder because it approaches the event horizon.
As well as, normal relativity predicts that when an observer in a low-gravity setting observes an object in a high-gravity one, the observer will see time go extra slowly for the thing. This slowing signifies that the sunshine emitted by the falling object shall be unfold out over a for much longer time. When you scale back the speed at which gentle is emitted, it can seem dimmer and dimmer. From the observer’s perspective, as the thing approaches the event horizon, time will gradual to the purpose the place it can take longer than the lifetime of the universe for the thing to emit particular person photons.
Thus, as an object falls towards the event horizon of a black hole, it can redden in look. It’ll additionally seem to emit gentle extra slowly, and thus will change into dimmer. The mixture of those two results are that an exterior observer will see the thing redden and fade out of sight, however they may by no means see it cross the event horizon.
Don Lincoln
Particle Physicist, Fermi Nationwide Accelerator Laboratory, Batavia, Illinois
