Curvature of space/time question/problem

• curtmorehouse
In summary, the video explains space/time as a fabric with a ball on it, and demonstrates how one ball causes another to curve when rolled past it. It then discusses Arthur Eddington's experiment to test general relativity using a solar eclipse and photographing stars behind the sun. However, there is confusion about how light curves away from the sun before curving back towards it, and the video's animations may not accurately represent this concept. Overall, the video's explanations and analogies may be misleading and not entirely accurate. The concept of spacetime was first introduced in Minkowski's paper in 1909, not in Einstein's paper in 1905.
curtmorehouse
While watching a video on youtube about space/time, it explained space/time like a fabric with a ball on it. Rolling another ball past this first ball caused the second ball to curve. I get that part. then they said that Arthur Eddington went to test general relativity by photographing a solar eclipse and proved general relativity by photographing stars that were behind the sun.
this video is here

I understand the curving of light on it's way past an object (sun in this case) but how or why does the light headed straight for the object suddenly curve away from the object before it curves back towards the object to make Eddington's photos real?

In other words, if Gravity makes the object curve towards something as it passes it, why wouldn't the object (or light from it) crash right into the object if it was on a perpendicular path towards the object?

watch the video and tell me what I'm missing please.. the part I am talking about starts at about 3:15

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In the case of something like the sun or a star, to a very good approximation, the geometry of the space - time curvature is a 4 - dimensional sphere. The photons that make up the ray of light will move according to this geometry (so along the 4 - sphere in their path to put it loosely) so they will move in the fashion shown in the video until they are farther away from the sun where space - time is pretty much flat again.

I guess I don't understand what you are saying, because that doesn't explain why it moves AWAY from the sun before it curves back towards it. Also why doesn't a ball rolling towards (but not in a intersecting path) an object move away before it curves back towards it? Are the animations in the video not correct? OR just the one showing the photographing of starts behind the sun?

Yeah it moves along the geodesics of the 4 - sphere and speaking in terms of space alone, which is what the video shows, a sphere bulges out at the sides...so it goes out then in and keeps going off to infinity.

I see what you are saying curtmorehouse. It is a bad graphic, yes photons going straight into the star will just go straight in, it is the photons that are glancing the star that get bent. Don't forget that photons are going out spherically from the light source behind.

That video has some of the worst explanations of those analogies I've ever seen, analogies that are already sources of confusion for the unwary. Not surprised it's from the history channel.

BTW, the concept of spacetime comes from Minkowski's paper of 1909, and is not in Einstein's paper of 1905.

What is the curvature of space/time?

The curvature of space/time is a concept in physics that describes how the presence of massive objects can cause the fabric of space and time to bend. This is explained by Einstein's theory of general relativity, which states that mass and energy can warp the fabric of space and time, causing objects to move in curved paths.

How is the curvature of space/time measured?

The curvature of space/time is measured using mathematical equations, specifically the Riemann curvature tensor, which quantifies the curvature at each point in space and time. This measurement is also known as the curvature scalar or the Ricci scalar.

What are the implications of the curvature of space/time?

The curvature of space/time has many implications in the field of astrophysics and cosmology. It explains gravity and the movement of objects in the universe, including the formation of galaxies and the expansion of the universe. It also predicts the phenomena of black holes and gravitational lensing.

Can the curvature of space/time be observed?

Yes, the curvature of space/time can be observed indirectly through its effects on objects and light. For example, the bending of starlight around massive objects, such as galaxies, is evidence of the curvature of space/time. The gravitational lensing of distant objects is also a result of the curvature of space/time.

Is the curvature of space/time constant?

No, the curvature of space/time is not constant. It can vary depending on the distribution of mass and energy in the universe. The presence of massive objects and their movements can cause fluctuations in the curvature of space/time, as described by Einstein's field equations.

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