Few Questions about Einstein's Theory of General Relativity?

Question

How can the gravity of massive objects like Earth,Mars,Black hole can cause space to bend according to Newton's general theory of relativity?....and how are space and time are linked?like Space time?what is it?thanks:)

Answer 1

The universe was considered a 4d plane, with 3 dimensions of space and one time.

By combining space and time, it can be considered a 3 dimensional plane.

Einstein imagined the universe as a giant rubber sheet stretched out across a hollow table top.

The rubber sheet was the space time. Now, if you place a heavy object on the rubber sheet, it will create a depression around it. Suppose you place a big ball on the sheet, it will create a depression around itself. if you place a smaller ball in the depression, the small ball will spiral towards the big ball.



So, the big ball can be imagined as the Earth and just as the big ball caused a depression in the sheet, Earth causes a depression in space time. The small ball can be viewed as the moon, it feels the gravitational effects of the Earth.

This image will help you understand it better: https://blogs.stsci.edu/livio/files/2012/06/spacetime.jpg

Hope this helps you.

Answer 2

"How can the gravity of massive objects like Earth,Mars,Black hole can cause space to bend according to Newton's general theory of relativity?"



Newton saw gravitation as force at a distance, with no known carrier. He was uncomfortable with this, according to his own writings.



Einstein (not Newton, in the General Theory of Relativity) essentially says spacetime is the product of mass, and curvature (bending as you say) is what spacetime does as it sweeps from a "Universal average" to "locally added / supplied".



"....and how are space and time are linked?like Space time?what is it?"



No one can know. I suspect that time evolves from the 2nd law of thermodynamics (net production of entropy, a one-way arrow). I suspect then that 3D space evolves from time and conservation of momentum in a multi-body Universe. It is clear spacetime is not stuff.



Consider that all inertial observers agree on the value of s:

s^2 = (x^2 + y^2 + z^2) - (ct)^2

space and time are closely related...

Answer 3

Gravity does not "cause space to bend" because space is never "straight." Just as the shape of the surface of the Earth has variations in height, so our three-dimensional space has variations in its shape. This is sometimes pictures as a bent surface (a rubber sheet), but that gives the wrong picture. Think instead of distances and directions within space being altered by the presence of massive objects. So far from masses, space has a characteristic "curvature", while near masses (like stars or planets), that curvature changes.



Space-time is shorthand for the recognition that the curvature of space affects the measurement of time, *and* that acceleration is measured the same whether caused by a local mass or by change in velocity. So clocks move differently (and light changes frequency) near a large mass or when emitted by a fast-moving or accelerating source.

Answer 4

The observed rate at which time passes for an object depends on the object's velocity relative to the observer and also on the strength of gravitational fields, which can slow the passage of time.http://en.wikipedia.org/wiki/Time_dilation

When dimensions are understood as mere components of the grid system, rather than physical attributes of space, it is easier to understand the alternate dimensional views as being simply the result of coordinate transformations.

Spacetimes are the arenas in which all physical events take place—an event is a point in spacetime specified by its time and place. For example, the motion of planets around the sun may be described in a particular type of spacetime, or the motion of light around a rotating star may be described in another type of spacetime. The basic elements of spacetime are events. In any given spacetime, an event is a unique position at a unique time. Because events are spacetime points, an example of an event in classical relativistic physics is (x,y,z,t), the location of an elementary (point-like) particle at a particular time. A spacetime itself can be viewed as the union of all events in the same way that a line is the union of all of its points, formally organized into a manifold, a space which can be described at small scales using coordinates systems.

In general relativity, Einstein said that Gravity is causing a "motion like" effect so there for we get credit for moving through the cosmos at ..1g.. because that is the gravitational force here at the surface of the Earth, If we where to go to the moon we would only get credit for moving through the cosmos at a speed relative to the Moons gravity.. this is how massive objects play a part in general relativity..because there gravity is causing space to act/think your moving through it even if we are standing still.

http://en.wikipedia.org/wiki/Spacetime

http://en.wikipedia.org/wiki/Special_relativity

Answer 5

Your asking about his Theory of Special Relativity.



Space time is part of the theory of special relativity not General Relativity, all these people didn't realize it is in fact a trick question.

Answer 6

It all started by the quest of, what is light? Already in the 17th century the Danish astronomer Roemer, discovered that the moons of Jupiter were moving at a different speed from summer to winter. He concluded that since the distance changes during the year, it must be the effect of the speed of light, which he calculated quite closely, considering the technology of the time.



Then the question was: What is light? Does it moves like a sound wave? If so, in what does it move? And we called it, the ether! Light moves like a wave in the ether. Then we tried to measure if the ether move itself. For example, if a bird flies in the wind, it will go faster with the wind than against it. So we tried to find the "speed of the ether" but ... we couldn't find anything!



Then Einstein said: "What if the speed of light is constant and there is not ether?" If so, time and space must be two sides of the same thing and he called it, spacetime!



When you see the sun, you see how it was 8 minutes ago, the closest star, Proxima Centauri, how it was 4.5 years ago and, distant galaxies, how they were billions of years ago.



Hence, when you see in space, you also see in time and the past is a sphere around us! Yes it is and that is why the Cosmic Microwave Background (CMB) that is the left-over of the Big Bang, comes from all directions in the sky!



The universe has no center as any observer will observe it as being at its center. The universe has no edge either since it does't matter how you are, you always observe it as being at the center, pretty much like the fish swimming in an ocean without continents is always in the middle of the ocean!



Since two different observers, each in their own frame of observation, can observe two different things, they are both right! And that is what Relativity is all about.



Say, I fly a spaceship near the speed of light. I switch on my headlights and I see it lightning an object ahead of my, at once. But you, from another place, sees the headlight moving slowly ahead of me because you see me moving at nearly the speed of light. We observe differently and that is because, for me, time runs differently than for you.



The funny thing about Einstein is that everybody remembers him as an old man with long hair and a white mustache. But in reality, Einstein found everything, before he was 30 years old!

Answer 7

First of all, Newton and Einstein don't agree precisely under

extreme conditions, (like Black Holes), or very close measurement.

'Time', (and its rate variations), must be factored in to explain the differences.

It was Einstein's explanation of anomalies in the Newtonian computations

of the orbit of Mercury that was one of the first validations of his Theory.

Answer 8

think of space and then time at the same time they are both bending