Is the Hollywood Theory of Black Holes Correct?
Last year, the astrophysicist community watched the movie Gravity; this year, there’s Interstellar, which is far more ambitious in the concepts it addresses, although it definitely leans heavily on the “fiction” aspect of the science-fiction genre.
While there are many false claims and depictions in the movie (for one, no one knows what is in or on the other side of a black hole), the movie did manage to portray one interesting part of astrophysics.
In the movie, the astronomers explore a distant galaxy with a giant black hole, named Gargantua. They go to explore one of the planets near the black hole, which has an unfortunate side effect: a 23 years slip in no time at all. The reason is that time is distorted as you approach a black hole in an effect known as gravitational time dilation.
So why does this time distort?
American physicist John Wheeler was the first person to recognize the importance of black holes, the problems they pose, and name them. The Milky Way has its own black hole, Sagittarius A, located in the center of the galaxy.
Black holes are expected to form when massive stars collapse, and they continue to grow by absorbing mass from their surroundings. The boundary of the black hole is not a visible, but is called the event horizon. Once the event horizon is passed, no escape is possible. Not even light can escape a black hole because, as Albert Einstein showed, gravity can influence light’s motion.
If we view spacetime as a fabric, the black hole’s massive gravity field stretches the fabric like a cannonball that has been dropped onto it. As a result, time is stretched, so to speak. For objects approaching and entering the black hole, time continues to tick away as usual. However, for observers viewing from a distance, anything approaching the black hole will appear to slow and hover just outside the black hole.
In the movie Interstellar, they determine that an hour on the planet close to the black hole is the equivalent to 7 years back on Earth.
The concept that the more massive and compact a star is, the more it will curve and distort the spacetime near it is called General Relativity, which was Einstein’s theory.