Sunday, November 22, 2009

Black Holes


I have been thinking of black holes for the past few days. The more I thought of it, the more fascinating I found black holes to be.

Black holes are sometimes referred to as space-time singularities. This is because matter is concentrated into a small area (which could either be a single point, or a radius of a few kilometers) with infinite density that the space-time fabric around the black hole is so distorted that even light cannot escape it. In simpler terms, gravitational force is infinite, so dominant that even massless particles such as photons are unable to escape a black hole. This is ironic because among the 4 fundamental forces of nature, gravity is the weakest (coming after the strong force, the weak force and the electromagnetic force).

The space-time fabric inside a black hole is so distorted that if any matter were to fall inside a black hole, the gravitational tidal forces will crush it. Imagine a hypothetical scenario where a spaceship went past the event horizon of a black hole (and is thus unable to escape it) and falls into the black hole. As it descends, gravitational tidal forces will rip apart the spaceship and constituent molecules. As it descends further, even the atoms are ripped apart into protons, neutrons and electrons. Further down, even the protons and neutrons get torn apart into quarks.

Now I have a little speculation here. Quantum physicists (especially proponents of the Standard Model) have proposed that gravitational force is mediated by gauge bosons known as gravitons. In the standard model, every particle has an anti-particle version of itself. Thus, if the hypothetical spaceship were to issue a continuous stream of anti-gravitons against the direction of travel, it could be sufficient to counteract the effects of gravity, hence allowing the spaceship to escape from the event horizon and save the crew.

Anyway, back to reality. Black holes cannot be detected directly through conventional optical telescopes as they do not emit light. Thus they are detected indirectly using gravitational lensing or by detecting X-ray radiation emitted by objects when they fall into a black hole. Thus only advanced observatories will be able to detect black holes.

Dr. Stephen Hawking theorized that at the other end of a black hole is a white hole, where matter that is sucked into a black hole is spewed out (albeit in a different form) at the other end. This will then be used to form new universes at the other end. This is another instance of how black holes pose a paradox – an agent of destruction works simultaneously as an agent of creation. Isn’t our universe wonderful?