Space-Time | Time and Space relation explained | 2018

Space-Time – The space-time is a peculiar combination of time and space. Time and space together makes a 4^th dimentional spacetime. Gravity and spacetime are linked to one another. Space time continuum explains this phenomenon defying the physics of space, time and gravity.

Space-Time peculiarity explained

Today we are going to talk about  Space-Time whether it is real or an illusion. So the question arises while understanding SpaceTime is that what is time? Is it related with space?

Before Einstein’s era, scientists believed that space and time are independent of each other. Neither of them are related in any manner. So any change in time doesnot effect space and also any change in space doesnot change time.

Know how gravity works

According to Newton, Time is absolute irrespective of any point in space. Which means if anyone spends one hour on earth that means everywhere in the universe one hour has passed whether anyone is on Mars, Jupiter or travelling with the speed of light or may be near a black hole.

Now lets understand Space and time separately. Space is everything we see around us. Each and every object is a part of space. To denote the position of an object in space, we use the 3-dimentional co-ordinate system.

Now time is something every one knows that it keeps moving forward. It is also called time dimension or the fourth dimension.  And mixing it with 3-dimentional space, it creates a 4-dimentional space-time.

But despite of different characteristics, Einstein believed that Space and time are relative i.e they are related to each other. He said that time is relative and not absolute, which means that time passes with different speed depending on the situation and condition. The speed of time for an object depends on the velocity of the object and also on the gravitational field of the object. The speed of time slows down with the increase of the velocity and gravity for the object.

See working of gravity here

Lets understand this with two examples.

Let us take two planets, our earth and Jupiter. As Jupiter is much larger than our Earth and also have a larger mass than earth, so the gravity on Jupiter will be more than that of our earth. So the speed of time on Jupiter will be slower than on earth. Hence, if a person travels to Jupiter and lives there then he will live longer than those people on earth as time will slow down for him.

Again time also depends on speed of the object, so let’s take two twin brothers. Now if one brother stays on earth and the other goes in a space mission travelling with high speed with almost the speed of light. Then what happens, the time for the brother travelling with the speed of light gets slower. Now when the brother returns back to earth after a couple of years, he will see that his brother on earth has grown old while his age has just been increased by two years.

This phenomenon states that time and space are related with each other. And here the concept of Time dilation and length contraction comes into play. Now according to Einstein, for every inertial frame of reference, speed of light is constant. As we reach nearer to the speed of light, time slows down. If our speed is as fast as that of light then for us time would seem to stop and also space would seem to adjust itself to time. To explain this phenomenon a mathematical model was made which is called The Space-Time Continuum.

Physics doesnot see the world as we see. For us every event in the universe is like a film which keeps moving forward but physics sees this film in frame by frame reference.

Defying Gravity | Gravitational force explained | 2018

Let’s understand this with the help of an example.

If we throw a pebble in a pond then it creates ripples on water, for us the event goes simply as a stone is thrown in a pond and because of which ripples are created. But according to physics, it looks somewhat like a graph where initially no change occurred then after one sec, one ripple had been created, after two sec two ripples had been created and so on. So this graph makes a cone and now if we want to know the future event of ripples then we would just have to extend the cone.

This cone is the locus of light through space-time. Now if we reverse this cone then we get the past events of the cone. This cone is called Future light cone.

This cone helps us to understand our universe. A great example of this is the Big Bang theory. As we can understand how the past of any planet or event was and also we can know what the future of the planet or event will be by just calculating its position in the spacetime graph. And due to this Space-Time concept we can understand gravitation clearly.

Know the effect of gravity on our universe

Watch a video related to this topic here- http://dai.ly/x6p9axp

The Mystery of spacetime and gravity defined

Gravity force | Gravitational Force explained | 2018

Gravity force - While defining gravity force, the question arises that What gravity actually is? Why is gravitational force an unsolved and exciting question? Why do we still do not understand the reason why the gravity force is so different among all the four fundamental forces of nature? Why this topic is so important? And why Sir Issac Newton and Albert Einstein became so famous for this?

Gravitational Force explained in detail

To know and understand this phemomenon, let’s go back in time. It all started way back in the 17^th century on the year 1661 when Newton was at the age of 18. He left his home at this age and took admission in The Cambridge University. Later in the year 1665 there was an epidemic of Plague over London which had a very drastic effect on London and along with this The Cambridge University was also shut down and hence Newton had to return home. And because of this, Newton now had all the time in the world to carry on his research.

Know about spacetime and its peculiarity

Near his house there was a garden full of apple trees where he used to spend some time sitting under a tree and tried to understand the secrets of the universe.

Then one day that famous incident occurred which gave birth to modern day physics. An apple fell near him. Looking at the apple Newton thought why did the apple fall down and why not anywhere else. So he started his research and finally said that the force which makes the apple fall on the ground is gravity and also he said that gravity doesnot only work on earth but also in the whole universe. Then he explained this in a peculiar way.

He assumed that we put a canon ball machine on top of a hill. Now if we fire the canon ball then according to Newton’s First law of motion the ball must travel in a straight line forever untill and unless an external force is applied to it. But due to gravity, the canon ball falls back on the earth. Now if we increase the speed of the canon ball then the ball travels a bit more further distance but still falls back on earth. Now if we keep increasing the speed of the ball then a time would occur when the ball would go into an orbit and revolve around the earth. Now using this theory, he explained the revolution of moon around the earth and also with this theory, he explained the revolution of other planets in the universe.

For this theory he gave an equation which is the gravitational force is directly proportional to the product of the masses of the bodies which is divided by the square of the distance between them.In simple language, this means that any two bodies however small or however large they be or whatever their masses be but they attract each other. But this force is very small, hence to solve this Newton added an universal constant whose value is also very small. He couldn’t calculate the value so he gave it a name as ‘G’. So his equation now looked like- ‘F=GMm/R2’.

Later a scientist, Henry Cavendish experimentally evaluated the value of G.

After this Newton tried to understand Kepler’s law finding gravitational acceleration of any planet etc.

Mathematically it is shown that According to Newton’s Second Law of motion, F = ma which means the net force equals the mass of the object multiplied by the amount of acceleration. Also we know, a = GM/R2.

Now in gravitational field, the acceleration is equal to the gravitational acceleration ‘g’.

So we get, g = GM/R2.

These equations are so accurate that NASA and ISRO still uses these equations for any space mission.

Now when Newton observed the falling of apple more distinctly, he found something more strange. Before that Aristotle gave a theory that if we through two bodies of different masses from a certain height then the one with the more mass will fall fast but it was proven wrong by Galileo with his experiments. He said that even if there is a vast difference between the two masses but still theyt will fall with the same velocity as the gravitational acceleration of any planet is same for all objects.

So if we want to measure the average speed of any object, say an apple then we would simply have to divide the distance travelled to the time required. But Newton wanted to find the speed of an apple at any instant time which was not possible but the total average velocity. So for this he needed to find the average velocity for a very small time interval which will tend to zero but not equal to zero. Hence for this reason Newton found out a new branch of mathematics called Calculus and this Calculus is now the backbone of Modern science.

Using this Calculus he proved the inverse square law of Gravity. Now according to this law, if the apple is twice as far from the centre of the earth then the force due to gravity will be four times less.

But when Newton Published his paper then questions arised from everywhere that How does Gravity act on everything but he literally didnot had any answer for this. He said that it is a mysterious force of nature which acts by itself. But Gravity is more mysterious then Sir Isaac Newton could think about.

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All about Gravity Explained