General Relativity Part 4: Gravity, The Einstein Way
Apologies for the silcence lately people. Went for a short vacation and needed some time to find my train of thought.
Previously, we’ve seen why gravity is not a force per se and the acceleration we feel is actually the manifestation of gravity itself.
So now we shall simply get to the barebones version of Einstein’s general theory of relativity and be done with it.
Basically, his idea is that mass and energy warps spacetime. To get a clearer picture of how this works, let’s use a light beam passing near the Sun as an example. Of course, the beam gets deflected as it travels in the vicinity of the Sun.
Newtonian physics would explain that phenomena occured as the Sun’s gravitational forces deflect the photons (the fundamental units of light which are not massless) towards the Sun as it travels. Einstein, however explains that the geometry of spacetime itself is warped, hence the light beam’s path is bent by the warping.
To get an even clearer idea on how it looks like, we’ll use the rubber sheet analogy. Here, a two dimensional rubber mat is substituting for the four dimensional spacetime and the red line is the light beam deflected after passing close to the Sun.
Photoshopped image from www.zarm.uni-bremen.de
That’s the crux of general relativity (without the accompanying equations).
Although both universal gravitation and general relativity predicts a deflection, general relativity predicts a deflection angle twice that of what was predicted by universal gravitation. To settle the dispute, a British expedition consisting of two teams went to Brazil and Principe Island off the coast of Africa to observe the deflection of starlight caused by the Sun during a solar eclipse in 1919. After careful analysis, Einstein’s theory was validated. The spectacular fashion in how it was proved subsequently made Einstein immortal. The London Times announced the news with the headline "Revolution in Science…Newtonian Ideas Overthrown" and another "Light Caught Bending". Little wonder why he became so famous right?
P.S. : If you wonder why we’re still being taught Newton’s theories although they’re outdated and surpassed by Einstein’s theories of relativity, it is because Newton’s formulas are simpler yet sufficiently accurate for everyday use. Only in the regions of extreme gravitation (eg around black holes) and relativistic speeds would general relativity and special relativity be important.
