Exploring Gravity: The Theory of General Relativity and Rocket Launches

[rudransh verma]

If a rocket takes off from upper part of Earth then it will have to pass the curvature(known as gravity) experiencing gravity which we also experience in reality.But if a rocket takes off from lower part (say antarctica) and moves straight downwards then it would not have to pass the curvature caused by Earth mass and so it should not experience gravity. But we know gravity is all around earth.
What will you say to save the THEORY!

 

[Nugatory]

Would you by any chance be thinking of one of those pictures that shows the Earth as a ball sitting in depression in a stretched sheet? If so, you should put that picture out of your mind, as it very misleading.

The curvature in general relativity is curvature of four-dimensional space-time, not three-dimensional space. We humans aren't very good at visualizing four-dimensional shapes :) so you won't find any good pictures. However, the thing you need to know is that the curvature is the same in all directions heading out from the Earth - the standard solution (google for "Schwarzschild metric") for the gravitational field of a massive sphere like a star or a planet is spherically symmetric, meaning thatthe curvature at any given point is a function of the distance from the center of the Earth but not the direction.

 

[Matterwave]

A quick way to refute your argument is to note that in space there is no "down" or "up". So Antarctica happens to be what we call "south", there is nothing in space to distinguish it as special. There's no "upper part" or "lower part", the Earth is just a sphere (to first approximation), and as far as gravity is concerned, the Earth is the same from any which way you look at it (again, to first approximation).

 

[Dale]

What will you say to save the THEORY!

The theory does not need saving. Misunderstandings about a theory do not constitute a challenge to the theory, merely an educational opportunity for the person with the misunderstanding.

 

[rudransh verma]

Would you by any chance be thinking of one of those pictures that shows the Earth as a ball sitting in depression in a stretched sheet? If so, you should put that picture out of your mind, as it very misleading.

The curvature in general relativity is curvature of four-dimensional space-time, not three-dimensional space. We humans aren't very good at visualizing four-dimensional shapes :) so you won't find any good pictures. However, the thing you need to know is that the curvature is the same in all directions heading out from the Earth - the standard solution (google for "Schwarzschild metric") for the gravitational field of a massive sphere like a star or a planet is spherically symmetric, meaning thatthe curvature at any given point is a function of the distance from the center of the Earth but not the direction.

actually yes pictures are very misleading.

 

[A.T.]

actually yes pictures are very misleading.

Try the videos in this post:
https://www.physicsforums.com/threads/spacetime-and-gravity.773923/#post-4869349

And note that "space" here is always the radial direction. So "upwards" is always away from the the center of Earth, no matter where on the Earth you are.

 

[rudransh verma]

theory of relativity can't be visualized actually but can be only understood in a very simple form..Its complicated version is very difficult to undestand.

 

[Nugatory]

theory of relativity can't be visualized actually but can be only understood in a very simple form..Its complicated version is very difficult to undestand.

Keep at it... The hard part isn't the theory, it's recognizing the unconscious classical assumptions that we make about how the world works so that we can retrain our intuition.

 

[A.T.]

theory of relativity can't be visualized actually but can be only understood in a very simple form..Its complicated version is very difficult to undestand.

Yes, some simple scenarios, which involve just 2 of the 4 space-time dimensions can be visualized in one diagram. Others require multiple diagrams.