How Does General Relativity Explain the Motion of Earth and Light?

[mxur]

http://en.wikipedia.org/wiki/General_relativity
if you go to this link, and find "Physical description of the theory" not far from the top. the 5th paragraph starts 'More specifically, let us ask how..'
i understand Earth moves in spiral, and light moves in spiral too but with lower angle against horizontal, is this because of time decreasing due to lorentz factor?
also it brings coordinates ct and says its increased by one light year. why introduce the light? also, it shows the angle Earth takes on the spiral is C divided by orbital velocity. why C?? and why 2 speeds show an angle?
sorry if it isn't explained very well.

 

[pervect]

If you want to compare time and space, it's very natural to use geometric units where c=1.

Measuring time in years and distance in light years is one choice of geometric units. These are geometric units because the speed of light is exactly

1 (light year) / year

Conveniently enough, 1 g is approximately (1 light year) / year^2 (it's not exact, but close).

 

[R0man]

First of all, it's great that you're taking the initiative to learn more about general relativity by reading the Wikipedia article! It's a complex and fascinating theory, so it's completely normal to have questions and want to understand it better.

To answer your first question, the spiral motion of Earth and light is not directly related to the Lorentz factor, but rather to the curvature of spacetime caused by massive objects like the Earth. In general relativity, gravity is described as the curvature of spacetime, and this curvature can affect the motion of objects and light. The Lorentz factor comes into play when considering the effects of time dilation and length contraction, which are consequences of the theory of special relativity.

As for the introduction of the speed of light (represented by "c"), it is a fundamental constant in the theory of relativity. It plays a crucial role in defining the geometry of spacetime and is also related to the maximum speed at which information can travel in the universe. The angle between the Earth's spiral motion and the light's spiral motion is related to the ratio of the Earth's orbital velocity and the speed of light. This is because the speed of light is a universal constant, and it is used to measure the velocity of other objects in relation to it.

I hope this helps clarify some of your questions. Keep exploring and learning about relativity, and don't hesitate to ask more questions if you come across something you don't understand. It's a fascinating and constantly evolving field of study!