Wednesday, January 2, 2013

Orion in the Past

Orion by Johannes Hevelius, In public domain.
My neighbour had a request for me yesterday. He said he always wanted to know the names of the three stars that were lined up in the East sky, with two stars on either side. To be honest, I didn't know their names right away, although I did know that he was referring to Orion's Belt. So instead of heading on over to Wikipedia, I took a small detour and installed Stellarium from the Ubuntu repositories. I adjusted the co-ordinates to match our current location and then located Orion's belt. I took the laptop over to my neighbour and showed him the program's simulation of the night sky. I told him that the names of the stars were Alnitak, Alnilam and Mintaka. Furthermore the reddish star on the left was Betelgeuse and the white one on the right was Rigel. We then had a discussion about the distances that separated these balls of flame from our own little globe of blue and green. He had a difficult time grasping the concept of a light year because he could not believe that light had a speed, much less the distance travelled by light in a year. He probably posited that as an absurdity; like the speed of smell. He was absolutely blown away by the idea that we were now viewing Mintaka as it was 916 years ago; 916 years in the past!

So I gave him a little thought exercise. I asked him what the time was. He angled his hand into the path of the fluorescent tube-light and reported that it was ten past ten. So I explained that the light had travelled to his eye from his source- the watch- and that his brain had interpreted the information as the current time. However the distance between his eyes and the watch is so small and the speed of light so great that the time delay is negligible; almost instantaneous. However once you understand that light carries visual data and given great distances (that takes light itself, years!) between heavenly bodies, it becomes apparent that instantaneous is now replaced by a time lag: the line between the past, present and future becomes stark and no longer blurry. Now add to the fact that gravity travels at the speed of light, it would technically mean that we wouldn't be tossed out of our orbit if the Sun were to blink out. It would take 8 minutes I reckon!

Later, I was mulling over Arthur Clarke's brilliant short story, The Nine Billion Names of God. The monks in Tibet hire three computer scientists to assemble a machine in their monastery that would list out the names of God using the letters of the alphabet. The true names of God aren't Allah or Jesus but rather the lengthy permutations and combinations of special alphabets limited to listing names of ten characters in length.

“Well, they believe that when they have listed all His names — and they reckon that there are about nine billion of them — God’s purpose will be achieved. The human race will have finished what it was created to do, and there won’t be any point in carrying on. Indeed, the very idea is something like blasphemy.”

And once the list of nine billion names are completed, the purpose of the human race is completed and God himself steps in and destroys the Universe. The scientists themselves realize that nothing would happen but they don't want to be beaten black and blue by the monks when nothing does happen. These monks were the exception to the rule of the typical austere ascetics; they enjoyed the pleasures of life (“they might be crazy, but they weren’t bluenoses. Those frequent trips they took down to the village, for instance...”). So the scientists make their way to their plane as the last pages containing the names of the Creator are printed out. And here's the best line:

“Look,” whispered Chuck, and George lifted his eyes to heaven. (There is always a last time for everything.)

Overhead, without any fuss, the stars were going out.

Each of the stars would have been at differing light years from the Earth. So in order for the stars to go out “without any fuss”, they should have gone out hundreds or even thousands of years ago, so that their “death” could have been witnessed as simultaneous by the scientists! This leads us to the conclusion that the stars knew the exact time that the (less than austere) monks were going to complete their epic task! Finally, the monks declare that the machine would take 100 days to print out the 9 billion names of God. This story was written in the fictional time-line of the 1950s. One might wonder how little time that computation would take on a modern supercomputer that is capable of 10 quadrillion floating-point operations per second. Of course, no amount of scientific analysis would detract from the feeling of sheer awe and fear that those lines deliver, but it is fun to muck about with the maths.

1 comment:

Vyaas said...

"He probably posited that as an absurdity; like the speed of smell."

Far from an absurdity: first the diffusion speed of the "smelly" molecules, then the electrical "walkie-talkie" exchange between the brain and the nose.

(If you carry forth this simple observation of the impossibility of the instantaneous, you can convince yourself of the impossibility of the simultaneous as well!)

And as for Arthur Clarke, I think you're being generous to his capacity for detail. Those last lines however do make the heart palpitate with profundity.

Check out http://www.pitt.edu/~jdnorton/teaching/HPS_0410/chapters/index.html