How to build a time machine
I’m slowly building up the courage to read Professor Stephen Hawking’s “A Brief History of Time”. When the time comes I think it’ll take me quite a while — my abiding memory of studying for my A levels was how hard Physics was. Some of it just didn’t make sense to me…which is bizarre really — you can imagine an art or creative science not making much sense. In many respects it just is — I can’t explain why you prefer the Mona Lisa over Van Gogh’s Sunflower. You just do. It’s an irrational emotional reaction.
But Physics — that’s science. Documentable. Explainable. Reproducible. Except to my brain.
But, I digress. I came across this article a few months back where Professor Hawking explains how to build a time machine:
To approach the speed of light means circling the Earth pretty fast. Seven times a second. But no matter how much power the train has, it can never quite reach the speed of light, since the laws of physics forbid it. Instead, let’s say it gets close, just shy of that ultimate speed. Now something extraordinary happens. Time starts flowing slowly on board relative to the rest of the world, just like near the black hole, only more so. Everything on the train is in slow motion.
This happens to protect the speed limit, and it’s not hard to see why. Imagine a child running forwards up the train. Her forward speed is added to the speed of the train, so couldn’t she break the speed limit simply by accident? The answer is no. The laws of nature prevent the possibility by slowing down time onboard.
The notion of things changing in the universe to ‘protect the speed limit’ is absolutely fascinating.
[UPDATE] Professor Hawking has just released a new book: The Grand Design. It explains why the cosmos doesn’t just have a single existence, “but rather that every possible history of the universe exists simultaneously”. Woah. (via Kottke)
