Brahma's home

There is an interesting Hindu story about Brahma, the God who created the universe. A king named Kukudmi had a beautiful daughter named Revati who attracted many male suitors. Kukudmi wanted to make sure that his daughter would make the right choice in choosing a husband so he decided to consult Brahma. He went to Brahma's home together with his lovely daughter. Brahma was very busy with some God business and asked Kukudmi to wait a moment. A moment later, Brahma came out and asked the king the purpose of his visit. Kukudmi explained the situation, and asked Brahma for advice about selecting the right man from all those suitors. Brahma laughed and said, "All those suitors are dead and gone. Although you waited at my home for only a moment, during that period, thousands of years have passed on Earth". As you may well understand, the king was speechless. However, Brahma was able to at least solve one of Kukudmi's problems: "Go back to your kingdom", Brahma said, "and there you will find a suitable boy called Balarama for your daughter."

Presumably, Kukudmi and Revati returned to their kingdom thousands of years after their departure; they had travelled forward in time.



Time travel raises a number of strange issues and paradoxes. For example, somebody might travel into the past and murder his mother when she was an infant. If the infant dies, she can never become the mother of the time traveller. But that would mean that the time traveller was never born, so he could never go back to murder his mother.

Another oddity that can arise from time travel is illustrated by the following example: A man travels 1 year into the future and reads an article, in a scientific journal, about a revolutionary theory that unifies relativity and quantum theory. Our hero then returns to his own time and teaches the theory to his student, who then writes it up in a journal. The article written by the student is the very same one that the time traveller read. So where did the the revolutionary theory come from? Not from the student; the time traveller gave it to him. Nor did it come from the time traveller; he merely read it in a journal. The theory seemingly came from nowhere. How bizarre!

Of course this is science fiction. Although Einstein's equations do not disallow time travel into the past, there is as yet no physical evidence to show that it is possible. But time travel into the future is indeed possible and has been observed. Anybody who is even a little familiar with special relativity has heard about the "twin paradox". It goes like this: Betty and Bill are twins. Betty gets into a spaceship and travels at high speed to a nearby star and then turns back and returns home. On her return, she finds that 10 years have elapsed on Earth, but only 1 year had elapsed in Betty's spaceship during her journey. Bill (her twin brother) is now 9 years older than Betty, even though they were both born on the very same date. This is due to time dilation, which occurs when motion occurs at close to the speed of light. We never notice it because we move at much slower speeds, but the phenomenon of time dilation has been tested with atomic clocks which shows that time is really slowed by motion. It can also be seen with particles. A muon has a half-life of around 2 microseconds, but when sped up to close to the speed of light, the muon's half-life has been seen to increase dramatically. So time travel to the future is a proven fact!

Another way to travel forward in time is with gravity. Gravity slows down time; time on the ground floor of a skysscraper runs slower than on the 40th floor, but the effect is neglibile and unnoticeable. But on the surface of a neutron stat, the gravity is so strong that time slows significantly - by around 30-40 percent. To observers on Earth, the clocks on a neutron star will appear to go slower than those on Earth. Obviously there are no clocks on any neutron stars - this is just an analogy - but how do we know for sure? Well, instead of comparing clocks, we see changes in the frequencies of spectral lines, which reflect the changes in the atomic systems at the source. The frequency of light from the neutron star will appear reduced, and the increased wavelengths will shift toward the red end of the spectrum. This is the so-called gravitational red shift.

I won't say that Brahma lives on a neutron star - it's not massive enough to slow time down in the way suggested by the story - but maybe he has a holiday house not far from a black hole.

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