SPACE-TIME: summary of "A brief history of Time"
SPACE AND TIME (before Einstein)
The idea of space and time comes
from the universe. Now some questions that we have to face, like, When the
Universe was created? What is Universe? And, before the universe created, was
there any concept of time?
·
According to Big Bang, in the very early stage,
there was no universe. Rather the universe was in a dense condition.
·
Big Bang was that time, when universe created.
The article about origin of universe is already given. According to Hubble,
universe is expanding from the time big bang. So one can say that from the big
bang time has started. It means Big Bang was the 0th time of
universe. After 1 second from big bang, the age of the universe was 1 second.
As we know that second is the smallest unit of time.
EXPANDING UNIVERSE MODELS: http://www.theincredibletruths.com/2018/08/expanding-universe-friedmanns.html
What is Time ?
There is no such exact definition of time. Just we can say
that time is something (or a quantity) that flows in a constant speed. We can’t change the rate
of the speed of time or time can’t be stopped.
A philosopher, Bishop Berkeley, believed that all material
objects and space and time are illusions.
Some Time related laws:
1.
Galileo’s Laws : Galileo’s measurements
indicated that each body increases its speed at the same rate, no matter what
it’s weight.
2.
Newton’s Laws of Motion :
First Law: Whenever a body is not acted on by any force, it
will keep on moving in a straight line at the same speed and the body at rest
stays at rest forever.
Second Law: The acceleration of an object is proportional to
the force acting upon it and inversely proportional to the mass of the object.
A = F/M
F = MA, where, F= the
force acting
M= mass of the object
A= acceleration
Third Law: For every action there is an opposite and equal
reaction.
3.
Newton’s Gravitational Law : Every object in
this universe attracting each other. The attraction force between two bodies is
proportional to the masses of the bodies and inversely proportional to the square
of the distance between them.
·
Both Aristotle and Newton believed in absolute
time.
What is Absolute Time ?
Absolute time means, time doesn’t depend on any other
parameter. They believed that one can unambiguously measure the interval of
time between two events. Time is completely separate from and independent of
space.
Discovery of light :
Light travels at a finite, but a very high speed, was first
discovered in 1676 by the astronomer Ole Christensen Roemer.
Speed of light >
Newton’s measurement : 140,000 miles/second = 2.25×10^8
meters/second
Roemer’s measurement or modern measurement : 186,000
miles/second = 3×10^8 meters/second (approx)
·
A proper theory of propagation of light came in
1865 by James Clerk Maxwell. Maxwell’s theory predicted that radio or light
waves should travel at a certain fixed speed.
·
After that it was observed that light wave can
travel through vacuum also, but how? It was therefore suggested that there is a
substance called the “ether” that is present everywhere, even in empty space or
vacuum.
·
In 1887, Albert Michelson and Edward Morley did
an experiment at the Case School of Applied Science in Cleveland. They compared
the speed of light in the direction of the earth’s motion with that at right
angles to the earth’s motion. They found they were exactly the same.
*Must Read the After Einstein Part: http://www.theincredibletruths.com/2018/08/space-time-summary-of-brief-history-of.html
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