While most other branches of science tend to explain what you intuitively already know, cosmology has tested and proven track record of sending your “gut feeling” or intuition tipsy turvy.
Imagine an hypothetical case where two warring armies decide to sign the treaty of peace, only on the condition that both generals must sign the treaty exactly at the same instant in time, to ensure collateral commitment. Imagine that the instance in time needs to be so exact that the only thing they can rely is speed of light, which is a universal constant.
So, they both put a lamp in between and sit on two sides of the lamp and precisely same distance, so that when the lamp is lighted, the rays of light will reach the signing generals at the same instant and they can autograph the paper in front of them. All is good, right?
What if the generals are not on ground, but in a moving train, one facing the direction of motion of the train and the other in opposite direction. Now if the lamp is lighted, the people in train will still see the rays of the lamp reaching both the generals at the same time and they putting down their sign at the same time.
But the people on the ground will see something different. They will see that the rays of light reached the general, who was facing the direction of train, first and he signed first.
Why this confusion? Because speed of light relative to moving train is same as speed of light relative to stopped train. This phenomena is measured and recorded by physicists. Thus the light always travels at constant speed, no matter what is the relative speed between observer and the light source. So the light has to travel less distance to reach the general facing in the direction of the train, and will thus reach to him earlier.
So how to reconcile the two versions of the same events reported by observer on the train and observer on the ground?
You can’t reconcile them. That’s relativity. The world is highly relative experience and there is no way to reconcile the difference, neither is there anything called absolute world which is the true ground state. Every time, every place, it’s all just relative to one another.
If you are here this far with me, you will certainly like Brian Greene’s book “The Elegant Universe”. He won pulitzer prize for the book, which is kind of rare for a book on such a specialized subject. The language is truly simple and layman’s level. The examples and illustrations truly explanatory. Briane Greene’s area is string theory, which is an attempt to reconcile the differences between Theory of Relativity and Quantum theory.
If you ever dreamed of reading about Quantum Physics and Cosmology while drinking coffee and streatching on couch on a rainy day, this book is for you.
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