The Observant Astronomer

The passing scene as observed by an observant Jew, who daylights as an astronomer.

Thursday, September 15, 2005

General Relativity in Real Life

Some people seem to think that you need to be near a black hole to experience the General Theory of Relativity. This is to misunderstand Einstein's fundamental chidush (novelty). In the Special Theory the fundamental point was that the speed of light, c, is a constant. In the General Theory the point is that gravity is just another kind of acceleration. So, if you want to feel the effect of gravity as geometry, take a bus. Any local transit bus will serve, but you want one that makes lots of stops. Preferable with a driver who likes to drive fast in between and brake hard. And for this experiment, take one that isn't too crowded. Don't sit down though.

Now, when the bus is travelling at an even pace, walk down the aisle. Just like the sidewalk, no?

Wait until the driver starts braking for a stop, and start walking towards the front of the bus. Now you should feel like you're walking up down a hill. A steep one if the driver is braking hard. Why? Einstein told you: Acceleration = Gravity.


Blogger kurkevan said...

Am I missing something here? It seems to me that this would be a case of deceleration... unless, of course, I was walking towards the back of the bus.

4:01 p.m., September 18, 2005  
Blogger The Observer said...

Indeed. Sign error, since corrected. Thanks.

2:08 p.m., September 22, 2005  

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