Well, of course there are experiments which showed that space-time is
not flat - otherwise noone would have accepted this crazy theory :-]
There are no proofs, though - these _never_ exist for any physics
theory; you can only disprove theories (that's why being an
experimentalist is a very destructive job :-) I'll give you some
experiments which disproved that space-time is flat:
* planets rotate around the sun on an elliptical orbit. This orbit is
stable - say Kepler and Newton. But Mercury's orbit was found to
rotate (yes, not only Mercury, but also its orbit):
http://math.ucr.edu/home/baez/physics/Relativity/GR/mercury_orbit.html.
This is prediced by general relativity (the theory that is visualized
by masses - the sun in this case - "curving space time").
* the original experiment, conducted to check the predictions of Mr
Einstein: if masses bend space, so should the sun. If the space is
curved, light is curved. Imagine a star to the left of the sun.
There's a photon ("light particle") starting off the star. After a
(human) while, it gets closer to the sun. The sun sits in a dip of
space; you probably remember how that looks in 3D visualizations of 2D
space. Travelling with the photon (very unhealthy), it is bent to the
left - and flys in to your eye - and your brain tells you (assuming
that light travels straight - our mind does that) that the star is
farther away from the sun (in left-right-top-down, not light years)
than it actually is - the star seems to have shifted (see
http://www.firstscience.com/site/articles/coles.asp). The problem was
that you can't see stars next to the sun - if there's no solar
eclipse. So people waited for a while, then there was the first world
war, then waited again, then traveled to Brazil and Africa (see
http://www.firstscience.com/site/articles/coles.asp for what still
went wrong) to see one, and sent a telegram back: it works! (see
http://www.phy.syr.edu/courses/modules/LIGHTCONE/pics/einstein-eclipse.gif)
The latter has real consequences; it's called "gravitational lensing"
and used regularely in astrophysics nowadays. It's nicely described
here: http://www.astronomynotes.com/relativity/s4.htm (I had to search
for a while to find this nice page).
Finally, here's a summary of the most simple experiments on "mass
bends space": http://archive.ncsa.uiuc.edu/Cyberia/NumRel/EinsteinTest.html.
Enjoy! |
