Mercury's orbit proves Einstein's theory of Gravitational Relativity?

Welcome back to another edition of Ask ARSE. 
Where out dedicated followers prod ARSE and see what knowledge nuggets fall out. Today's episode comes from Jordan in A.S.S. - our exclusive Australian Space Society.

QUESTION: I am reading one of Stephen Hawking's books and, as a complete airhead when it comes to physics and science I am struggling with the concepts. I turned to a youtube video to try and figure out what gravitational relativity was. I think I grasp most of it from the explanation and diagrams, but the one thing I can't wrap my head around is the section on Mercury.

It is said that the precession of Mercury proved Einstein's curved space theory using the equation. Now, obviously, the equation is complete nonsense to me and so that could be why I can't see the connection, but if it's something physical ('the curvature does XYZ to Mercury which causes the precession!' etc) then please could someone explain?

Gravitational relativity is a theory proposed by Albert Einstein that explains how gravity works in a different way than what was previously believed. It suggests that gravity is not just a force pulling objects together but is also related to the curvature of space and time. This means that massive objects like the Sun can curve the fabric of space around them, influencing the motion of other objects nearby.

Now, let's talk about Mercury and its precession. Precession refers to the slight rotation of an object's orbit over time. In the case of Mercury, its orbit around the Sun is not a perfect circle but slightly elongated, like an oval. According to Newton's law of gravitation, this elliptical orbit should remain fixed and not change over time. However, astronomers noticed that Mercury's orbit was slowly rotating, meaning it was not returning to the same position after each orbit.

This observation puzzled scientists because it didn't match the predictions made using Newton's law. They expected a certain amount of precession based on the gravitational influence of other planets, but the actual measurement was slightly different.

Here's where Einstein's theory of gravitational relativity comes in. According to this theory, the presence of a massive object like the Sun can cause the fabric of space around it to curve. Think of it like a heavy ball placed on a stretched-out trampoline, causing a dip in the fabric.

This curvature of space affects the motion of objects that come close to it, such as Mercury. As Mercury moves through this curved space, its orbit experiences a small additional rotation or precession. The curvature of space caused by the Sun's mass contributes to this effect.

Scientists used equations from Einstein's theory to calculate the precise amount of precession that should occur due to this curved space. When they compared these calculations with the actual measurements of Mercury's precession, they found that Einstein's theory provided a very close match. This confirmed that the curvature of space, as described by gravitational relativity, was responsible for the observed precession of Mercury.

In simple terms, the curvature of space around the Sun causes Mercury's orbit to rotate slightly over time, leading to precession. By using Einstein's equations, scientists were able to explain this phenomenon more accurately than with Newton's law alone.

So, the equation you mentioned is a mathematical representation of the relationship between the curvature of space and the precession of Mercury's orbit. While the equation might seem complex, its purpose is to describe the physical connection between the two phenomena.

I hope this explanation helps you understand the connection between gravitational relativity, the curvature of space, and the precession of Mercury. Keep exploring and asking questions – science is all about uncovering the mysteries of the universe!

ARSE Jnr

The section where we explain the above to 5-year-olds (and Flat Earthers).

"Have you ever seen how a ball makes a dip in a trampoline when you put it on top? Imagine that the Sun is like a very heavy ball and space is like the trampoline. When the Sun is in space, it makes a dip or curve around it. This curved space affects how other things move near the Sun.

Mercury is a planet that goes around the Sun. Normally, it should go in a circle, but because of the curved space, its path is a little stretched, like an oval. Scientists noticed that Mercury's path was not staying in the same place. It was slowly turning or rotating a bit.

Before, people used a different idea to explain how things move, but it didn't quite match what they saw with Mercury. Then a very smart scientist named Albert Einstein came up with a new idea called gravitational relativity.

Einstein said that the curved space around the Sun makes Mercury's path rotate a little bit. It's like when you roll a toy car on a curved track, it starts to turn as it goes around. The curved space makes Mercury's path turn a little as it goes around the Sun.

Scientists used special equations, or math problems, to show how the curved space and Mercury's rotation are connected. They compared their math with what they saw in real life, and it matched very closely!

So, Einstein's idea helped explain why Mercury's path was turning. The equation is a way to show how the curved space and the rotation are linked together. It's like a special code that scientists use to understand how things work.

Isn't it amazing how we can learn about space and how things move? Scientists keep asking questions and figuring out new things, just like you do when you play and explore. Keep being curious and asking questions, and maybe one day you'll make exciting discoveries too!"

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