Chapter 2. Space & Time

Galileo rolled two different weight balls on a smooth surface to prove that bodies of different weight fall at different speed.

This means that effect of force is to change the speed and not just to set the body moving. This was Newton's first law which came in 1687.

In 1676, Christensen Roemer measured the speed of light by measuring the motion of Jupiter's moons. He calculated the speed as 140,000 miles per second. Actual speed is 186,000 miles per second.

James Clerk Maxwell's exeriments, in 1865, unified electricity and magnetism. According to him, light waves travel at fixed speed and they travel relative to 'ether'.

In 1887, Michelson and Morley compared light's speed in the direction of earth's motion with that at 90 degree to earth's motion. Result showed that 'c' was same. Michelson became the first American to get the Noble prize.

Between 1887-1905, Lorentz's experiments proved that objects contract and clocks slow down when they move through ether.

Then in 1905, Albert Einstein gave his theory of 'no absolute time' and so he said that idea of ether is unnecessary. According to his 'theory of realtivity', 'all laws of science are same for all freely moving observers, whatever be their speed'. Einstein also gave the world famous formula E=mc^2 which prove that nothing travels faster than light. Also, the energy which an objects has due to its motion, add to its mass. For example,
if v = 10% of c, then m = m + 0.5% of m, and
if v = 90% of c, then m = more than 2m.

Now let's see some point of differences between Newton's theory and the theory of relativity.
Newton's theory:
Suppose there are two points A and B. A light pulse starts from A for B. Different observers agree on the time that the journey of light pulse took, since time is absolute. But they'll not agree on how far light travelled, since space is not absolute. So different observers measure different speeds for light.
Einstein's theory:

Galileo

Chapter 1. Our Picture Of The Universe

It was in 340 BC when Aristotle first came with his idea that earth is actually spherical in shape. Before that people used to think that earth is plane and due to this they even scared to travel in seas so they don't fall out from the point where the plane ends.

In 2 AD Ptolemy proposed that earth is the centre point of the universe.

Copernicus gave another concept in 1514. He was the first to claim that not earth but the sun is the centre and the planets like earth revolve around it.

This Copernican theory was proved by Galileo in 1609.

During those years only, Kepler proposed that planets move in an elliptical path around the sun.

Then it was time for Newton who proved Kepler's elliptical orbit theory. He also gave his laws of motion and the law of universal gravitation. His theories were published in his book 'Philosophiae Naturalis Principia Mathematica' in 1687. In 1691 he also proved that there is no central point for the stars to fall.

One interesting point to note is that before 20th century, no one even thought on the fact whether our universe is expanding or contracting.

Immanuel Kant, in 1781, came with his 'Critique of Pure Reason' in which he gave his thesis as well as antithesis. The thesis claimed that there is no beginning and there is infinite time before any event. This actually was absurd. The antithesis claimed that if the universe had a beginning and infinite time before it, then why there is a particular time for beginning.

In 1823 a German scientist Heinrich Olbers gave his theory of an infinite static universe.

Then in 1929, Edwin Hubble proved that galaxies are moving away from each other, i.e., the universe is expanding. This made everyone think about the starting of the universe when it was infinitesimally small and infinitely dense. That was the Big Bang.

Presently, two basic partial theories exist:
(1) General theory of relativity, which deals with the force of gravity and the large-scale structure of universe.
(2) Quantum mechanics, which deals with the phenomena on small scales.
Both these theories, when combined, gives the 'Quantum Theory of Gravity'.

NOTICE:

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About S Theory

"Even if there is only one possible unified theory, it is just a set of rules and equations. What is it that breathes fire into the equations and makes a universe for them to describe?"
-Stephen Hawking

Hi everyone.
This site is for those who love physics.
S Theory is a quest for the theory of everything.
What this site has or will have is nothing but the simple knowledge of the law of universe.
Its a story starting from before the big-bang till now and also about the future of the universe.
Besides talking about the physical theories, this site also has some interesting and amazing facts which everyone must be knowing.
Readers are requested to post there comments about the topics presented here. Or if something what was not to be written got include here.
Before starting to post my topics I would like to present here some lines about the S-Theory.

Behind it all
Is surely an idea so simple,
So beautiful,
So compelling that when-
In a decade' a century,
Or a millenium-
We grasp it,
We will all say to each other,
How could it have been otherwise?
How could we have been so stupid
For so long?