# Thread: Newton's gravity bends the path in the Space-time Graph

1. ## Newton's gravity bends the path in the Space-time Graph

NEWTON'S GRAVITY BENDS THE PATH IN THE SPACE-TIME GRAPH

Newton's theory of gravity:

1 - The propagation speed of gravity is infinite. (false)

2 - The Law of Universal Gravitation predicts that the force between two bodies and separated by a distance is proportional to the product of their masses and inversely proportional to the square of the distance. (right)

Theory of General Relativity:

1 - For General relativity space-time is a flat object present throughout the universe. (false according my point of view)

2 - The gravity is produced for the curvature of space-time generated by the mass of a star. (false according my point of view)

Newton's gravity acts on the bodies and particles making their path in the space-time graph is a curve. The space-time graph is a geometric representation (abstract) to describe all events.

Try to visualize that if you jump up your path in the space-time graph is a curve called parabola (see figure), assuming, of course, that there is a gravitational force that "pulls" you down.

2. All you've done YET AGAIN is display to the whole world that you understand NEITHER Newton or Relativity. Pity. Even a blind squirrel fins a nut *sometime*!

3. I before understood less, but now I understand a little more the Relativity, so I do the criticisms.

Even a blind squirrel fins a nut *sometime*!
You mean? Even a blind squirrel FINDS a nut *sometime*!

4. Originally Posted by Sibilia
1 - For General relativity space-time is a flat object present throughout the universe.
Not exactly. In general relativity spacetime is generally curved and is (or at least contains) the entire universe.

2 - The gravity is produced for the curvature of space-time generated by the mass of a star.
Not really. Gravity is synonymous with spacetime curvature in GR, and is generated by the stress-energy of all the matter and radiation in the universe.

(false according my point of view)
Why exactly should anyone be concerned with your point of view?

Newton's gravity acts on the bodies and particles making their path in the space-time graph is a curve.
That is not what is meant by curvature in GR. In GR, the whole point is that it is spacetime itself that is curved, and bodies actually follow geodesic trajectories (the closest equivalent to straight lines) which can converge or diverge in curved spacetimes in situations where they wouldn't (e.g. if they start off parallel) in a flat spacetime.

5. Originally Posted by Sibilia
I before understood less, but now I understand a little more the Relativity, so I do the criticisms.

You mean? Even a blind squirrel FINDS a nut *sometime*!
Oh course. It was just a simple typo, no big deal.

6. Przyk says:
Not really. Gravity is synonymous with spacetime curvature in GR, and is generated by the stress-energy of all the matter and radiation in the universe.
1- Can you explain "and is generated by the stress-energy of all the matter and radiation in the universe" please.

2- If "Gravity is synonymous with space-time curvature in GR", which generates which?

7. I think that SR was successful, but Einstein must reconciled SR with Newton's theory of Gravity.

8. Originally Posted by Sibilia
1- Can you explain "and is generated by the stress-energy of all the matter and radiation in the universe" please.
In general relativity, spacetime curvature is caused by energy and momentum. Because of that, even light or an electromagnetic field can affect gravitation locally, even though light has no mass. Mass also causes curvature because mass is a form of energy in relativistic physics.

2- If "Gravity is synonymous with space-time curvature in GR", which generates which?
They're the same thing. Or if you prefer, spacetime curvature is the true nature of gravity according to general relativity. It's a bit more complicated than that in reality because there are a few different but related quantities in GR that all get called the "gravitational field" in common parlance, but spacetime curvature is usually considered the true indicator of nonzero gravity.

9. Originally Posted by Sibilia
I think that SR was successful, but Einstein must reconciled SR with Newton's theory of Gravity.
They are impossible to reconcile. Newton's theory of gravity is not a relativistic theory, and as far as I know there is no simple way of modifying it to make it relativistic while keeping it recognisable as Newtonian gravity. You touched on one symptom of this in your opening post: in Newtonian gravity, gravitational interactions are instantaneous. You could imagine introducing a time delay and making gravitational influences propagate at the speed of light, but even that wouldn't simply make Newtonian gravity relativistic because many quantities such as force and acceleration, that are invariant in Newtonian physics, are frame-dependent in relativistic physics.

Given this, and the fact that general relativity is already a very natural way of obtaining a theory of gravity that is (locally) consistent with special relativity, there doesn't seem to be much point in this endeavour.

10. Thanks a lot przyk for your explanation, now I understand more the Relativity.

It isn't the Theory of Relavity exclusively optical: light, light speed, light curvature, light cone, etc?

Is it correct to explain all of physical phenomena with the light behavior?

What about the other phenomena? waves, atomic particles, forces ...

11. Originally Posted by Sibilia
It isn't the Theory of Relavity exclusively optical: light, light speed, light curvature, light cone, etc?
No. The theory of relativity incorporates all of classical physics, including mechanics, thermodynamics, electromagnetism etc.

12. LEVELS OF THE COSMOLOGICAL DUALITY

Random is chance, that doesn't follow the principle of causality. In B-R governs the uncertainty principle.

In B-T the random becomes ordination and applies the principle of causality.

In D-T the becoming is no longer relevant due to the vastness of the universe. Governed by the principle of light-year.

The distance is the length of the line segment between two points in space.

13. Originally Posted by Sibilia
It isn't the Theory of Relavity exclusively optical: light, light speed, light curvature, light cone, etc?

Is it correct to explain all of physical phenomena with the light behavior?

What about the other phenomena? waves, atomic particles, forces ...
General relativity is entirely consistent and combinable with classical electromagnetism. The classical unification of gravity and electromagnetism is about a century old. The quantum models of electromagnetism, weak and strong forces, collectively under the umbrella of quantum field theory, can be put into curved space-time, ie a GR context, provided the space-time curvature isn't too extreme. Doing quantum field theory in weak gravitational fields is difficult but not impossible. That leaves quantum phenomena in a strong gravitational field, ie those experienced at the Planck scale. Such a formalism isn't currently known but a number of attempts are being worked on.

You really should already know this if you're making statements about GR in the way you are. It suggests you haven't done sufficient background reading to really be in a position to evaluate something you know nothing about.

14. Alpha wrote:
You really should already know this if you're making statements about GR in the way you are. It suggests you haven't done sufficient background reading to really be in a position to evaluate something you know nothing about.
I haven't said that, and I don't feel capable of evaluating the Theory of relativity.

15. Sibilia wrote:
Random is chance, that doesn't follow the principle of causality. In B-R governs the uncertainty principle.
In B-T the random becomes ordination and applies the principle of causality.
Let's see, here's a semantic issue. The central concept is probability. In the microcosm the probability of repeating a sequence of events is very low. In the human scale and in the macrocosm this probability is higher.

16. By looking at the stars we see into the past, while the farther further back in time.

The star Alpha Centauri is to 4.37 light-year.

The Andromeda galaxy is to 2.5 million light-year.

17. Originally Posted by Sibilia
I haven't said that, and I don't feel capable of evaluating the Theory of relativity.
You're stating its supposed strengths and weaknesses, what you consider to be valid or not. That is evaluating it.

18. RELATIONS BETWEEN SPACE AND TIME INTERVALS

From relations between intervals emerge reference frames. An interval is the separation between two points in space or time. The interval of space has two applications: the distance and length (latitude, volume, bodies). The applications of the time interval (changes) are: the duration and "when". The duration is the interval between any two points of a phenomenon. The when is an interval between an effective moment and the start moment of a cycle (hour, date).

...... INTERVAL 1 ................. INTERVAL 2 .................. RESULT
1 - length ............................ latitude .................. position on a plane
2 - distance ......................... duration ................ speed
3 - volume (a and b) ............. duration ................ growth, expansion
4 - distance ......................... when .................... spacetime trajectory
5 - volume (a and b) ............. when .................... size

In case 4, if gravity acts on a moving body curve its spatiotemporal trajectory.

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