Tag: General Relativity
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Shapiro Time Delay
Introduction The Shapiro time delay, also known as the fourth test of general relativity, describes the effect of time delay on light as it passes close to a massive object. Predicted by Irwin Shapiro in 1964, this effect is caused by the curvature of spacetime around the object, resulting in a longer path that the…
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Twin Paradox
Introduction The Twin Paradox is a famous thought experiment in special relativity. It involves a pair of identical twins: one stays on Earth, while the other departs on a high-speed journey into space and eventually returns. Upon reunion, the traveling twin is found to have aged less than the twin who remained on Earth. Though…
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Gravitational Force
Introduction The gravitational force is a natural phenomenon by which all things with mass or energy—including planets, stars, galaxies, and even light—are brought toward one another. It is one of the four fundamental forces known in nature. Newton’s Law of Universal Gravitation In the 17th century, Sir Isaac Newton proposed his Law of Universal Gravitation,…
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General Relativity
Introduction General Relativity is a theory of gravitation that was developed by Albert Einstein between 1907 and 1915. Based on his idea of what he called “The Equivalence Principle,” he proposed that gravity is not a force in the traditional sense, but a curvature in spacetime caused by mass and energy. The Field Equations The…
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Einstein Field Equations
Introduction The Einstein field equations (EFE) are the cornerstone of Einstein’s theory of general relativity. They describe the fundamental interaction of gravitation as a result of spacetime being curved by matter and energy. They were first published by Einstein in 1915. The Equation The Einstein field equations can be written as: Here is the Einstein…