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- Author: Ta-Pei Cheng
- Title: Relativity, Gravity & Cosmology: A Basic Introduction
- Amazon Link: https://www.amazon.com/dp/0199573646/?tag=pfamazon01-20
(submitted by serllus reuel)
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The theory of relativity, developed by Albert Einstein in the early 20th century, is a set of two theories that describe the laws of physics in relation to objects moving at a constant speed. The theory of special relativity deals with objects moving at a constant speed in a straight line, while the theory of general relativity deals with objects in accelerated motion or affected by gravity.
According to Einstein's theory of general relativity, gravity is not a force between masses, but rather a curvature of space and time caused by the presence of massive objects. This curvature causes objects to follow a curved path and is what we experience as the force of gravity.
Newton's law of gravity is a classical theory that describes gravity as a force between two masses. It does not take into account the effects of acceleration or the curvature of space and time. In contrast, Einstein's theory of general relativity is a modern theory that describes gravity as a curvature of space and time caused by massive objects.
According to the theory of special relativity, time and space are not absolute, but rather relative to the observer's frame of reference. This means that time and space can appear to be different for two observers moving at different speeds. In addition, the theory of general relativity states that gravity can also affect the flow of time and the shape of space.
Cosmology is the study of the origin, evolution, and structure of the universe. It incorporates theories from various fields of physics, including relativity and gravity, to understand the nature of the universe on a large scale. Cosmologists study the history of the universe, the formation and distribution of galaxies, and the composition of the universe.