Space and time

[Kenil Rajyaguru]

I don't understand the concept of when we move in light speed we age less than in earth. Why?

Is it coz of the gravity. Internet says that when gravity increase, the time becomes slows. So in the space one must age faster than the earth. But it isn't like that.

One more thing when we move with light speed, gravity will be generated inside the space shuttle, but it won't be more than the earth. Again they say when gravity increase, time slows..so moving with light year we should age more 🤔

If going through my theory, earth may had less gravity in past time and eventually increased with the time, due to that reason life span of human decreased with time and also the height.

 

[joigus]

No. The whole point of relativity, both special and general, is that you can't tell whether you're moving or standing still (special relativity), and whether you're in free space or falling in a gravitational field (general relativity, except tidal forces). So you can never tell by looking at things in terms of your own references. It's other observers (moving differently --SR-- or with different values of the gravitational field --GR--) that see those funny slowing downs, contractions, and the like.

In common scientific parlance, those effects are observer-dependent.

[Kenil Rajyaguru]

So how the time travel (dilate or one can say time difference or relative works) ?

[Strange]

There are two different things that can cause time dilation. One is relative speed and the other is gravity.

6 hours ago, Kenil Rajyaguru said:

I don't understand the concept of when we move in light speed we age less than in earth. Why?

First, not that you cannot move at light speed.

However, if you are moving relative to someone, then you will see their clock run slower (and their length shortened).

So, for example, if you are moving past the Earth in a spaceship, people on Earth will see your clock running slower than theirs (and so you will be also aging more slowly). 

BUT (and here's the tricky bit) you will also see the clocks on Earth run more slowly than yours. This is because it is all about relative measurements.

The reason this happens is because the speed of light is the same for everyone, independent of your speed. If you work out what that means, it turns out that an observer sees other people's clocks run slow and their rulers shorten. 

That has nothing to do with gravity. But gravity does also affect how we see other people's time. If your spaceship was stationary above the Earth, then you would see clocks on Earth running slower because of gravitational time dilation. Now, this may be confusing, but the people on Earth would see your clock run faster (not slower, as in the case of relative velocity). This is all caused by the curvature of spacetime (which also causes gravity).

6 hours ago, Kenil Rajyaguru said:

One more thing when we move with light speed, gravity will be generated inside the space shuttle, but it won't be more than the earth.

Acceleration causes "artificial gravity" (like when you are pushed back into the seat of your car, when you accelerate). But moving at any constant speed does not.

6 hours ago, Kenil Rajyaguru said:

If going through my theory, earth may had less gravity in past time and eventually increased with the time, due to that reason life span of human decreased with time and also the height.

There is no evidence that Earth had less gravity un the past. There is no evidence that human lifespan or height has decreased significantly over time.