understanding Space Time curvature

[acharyajit]

As I understand all the heavenly bodies rest on the space time fabric and the gravitational force is only the effect of the curvature.

I would like to understand two things. 

What is it that curves.. Is it space or time ? And since time is continuously moving, is the space time fabric also moving ?  if yes then why is it moving in one direction only ?.

And what exactly is the relationship between space and time

I would appreciate information

Regards

[studiot]

19 minutes ago, acharyajit said:

As I understand all the heavenly bodies rest on the space time fabric and the gravitational force is only the effect of the curvature.

I would like to understand two things. 

What is it that curves.. Is it space or time ? And since time is continuously moving, is the space time fabric also moving ?  if yes then why is it moving in one direction only ?.

And what exactly is the relationship between space and time

I would appreciate information

Regards

 

These are good, well posed questions that deserve well posed answers.

In order for us to pitch a reply at the appropriate level please answer the following question.

If we plot a circle on graph paper the relationship between the x axis and the y axis is given by the equation

x² + y² = r²,     where r is the (constant) radius of the circle.

Do you understand this statement?

[Strange]

29 minutes ago, acharyajit said:

What is it that curves.. Is it space or time ?

It is the "geometry" of space and time; i.e. our measurements. Space or time are not physical objects, so they cannot literally curve.

29 minutes ago, acharyajit said:

And since time is continuously moving, is the space time fabric also moving ?   if yes then why is it moving in one direction only ?.

In general relativity, time does not move. Space-time is a static entity that represents the relationship between things (events) in space and time. So where we perceived an object moving through space, that would represented as a stain line through space-time.

Why we perceive time as flowing from past to future is probably more of a philosophical/psychological question; although some branches of physics may help explain it (thermodynamics, for example, and various symmetries).

But as far as we know things can only evolve forwards in time so time machines are not possible!

33 minutes ago, acharyajit said:

And what exactly is the relationship between space and time

Studiot is right, a good answer to that needs to be pitched at the right level. 

[Mordred]

6 hours ago, acharyajit said:

As I understand all the heavenly bodies rest on the space time fabric and the gravitational force is only the effect of the curvature.

This statement needs addressing as it gives one of the most common misconceptions in GR.

The fabric is a term that was used merely as a descriptive for the average person to visualize curvature. It doesn't describe some hidden or mysterious matter like substance.

 When one describes spacetime curvature one is describing the geodesic path between two positions. The geodesic is affected by the mass term (resistance to acceleration) of all other matter and force fields in a given region. The coupling constants of each field contribute to mass. However a field is a geometric descriptive of values or other mathematical objects.

This is described via the Principle of least action (Langrangian).

So do not think of spacetime fabric as some medium. That would be incorrect.