In the film “Interstellar” the hero named Cooper falls into a supermassive black hole. What do we think would really happen if someone were to make such a brazen move?
Let us call that someone Cooper and let us call an observer who stays behind to look after the spaceship Amelia. We are all going to be in for a surprise. The adventure starts when Cooper grabs a special kind of flashlight that flashes instead of producing a steady beam of light, and then suddenly jumps.
As Cooper plunges towards the surface of the black hole, or the event horizon, Amelia will see the shape of Cooper’s body contorting as if she was looking at him in a fun house circus mirror. Strangely, Amelia would also see Cooper slowing down as he fell towards the black hole which is not usually what happens to objects when they fall.
If she is lucky, at this point Cooper will remember to pull out his flashlight and signal to Amelia that he is alright. In this case Amelia will see the flash-flash-flash of the device get slower and slower until the flashes which were arriving to her at a rate of once per second would slow down to once per hour, and then once per day and then less.
When Cooper will finally reach the event horizon Amelia will see him stretched abnormally in shape as well as frozen in time, while his contorted body would then appear to be consumed by the high energy radiation typical near the event horizon. From Amelia’s perspective he would be officially pronounced dead, whereas it would probably be more accurate to say that he is ‘no longer with us.’
What is happening from Cooper's perspective? Cooper may experience a rather graceful entry into the black hole, at least as graceful as one can be in full astronaut gear.
There are two reasons why this may be the case: first, while we describe a ‘surface’ of a black hole, it is not anything like the hard surface of the Earth. Secondly, as he is in free fall, he does not feel any accelerations or decelerations.
Recall that the black hole under discussion is of the supermassive variety. For such objects which weigh in at millions of stars each, the gravity at the event horizon is remarkably weak even compared to the pull of gravity on Earth. He would simply ’float’ into the black hole.
With all this excitement of falling into a black hole now over, Cooper may have start to have second thoughts and decide to return back to the spaceship. Unfortunately for him, the effort of climbing out of the black hole will all be in vain.
In addition to the pull of gravity, time is also pulling on him. That’s right. Just as we cannot escape back to an earlier time in our lives to change history, Cooper also cannot go back in time and decide not to enter the black hole. It is time that is now relentlessly reeling him in towards the singularity.
Meanwhile, back at the spaceship, Amelia has managed to send robots close to (but not into) the event horizon to collect Cooper's ashes. This is a definitive proof that he is dead, right? Again, in the next installment we will see that this may actually only the definitive proof that Cooper is 'no longer with us.'