General relativity / Elementary Tour: Conclusion

The aim of this chapter was to give the reader a basic idea of what general relativity is all about. Einstein's theory of gravity led physicists to a variety of new models and phenomena. The most important examples - gravitational waves, black holes, the ...

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Special relativity / Elementary Tour: Conclusion

As this brief tour of special relativity has shown, we have to re-think our notions of space and time in Einstein's world. Moving clocks tick at a slower rate, light speed is the same for all (inertial) observers, and lengths and distances depend on who ...

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Gravitational waves / Elementary tour part 2: Making waves

In our universe, gravitational waves are produced in many different ways. Almost every occasion in which masses are accelerated leads to the generation of travelling space distortions, be it two heavenly bodies orbiting one another or stellar matter ...

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General relativity / Elementary Tour part 4: The light side of gravity

For the propagation of light, Einstein's theory makes a clear prediction: Light is deflected by gravity. Just as test particles move on the straightest-possible lines in curved spacetime (i.e. on spacetime geodesics), so does light. The most basic example: ...

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General relativity / Elementary Tour part 3: A planet goes astray

The first test of general relativity concerned a situation in which Newton's and Einstein's theories give almost the same result - with a small but crucial difference. The scene: our cosmic backyard, the solar system. The protagonist: Mercury, the planet ...

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General relativity / Elementary Tour part 1: Einstein’s geometric gravity

The key idea of Einstein's theory of general relativity is that gravity is not an ordinary force, but rather a property of spacetime geometry. The following simplified analogy, which substitutes a two-dimensional surface for four-dimensional spacetime, serves ...

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Black holes & Co. / Elementary tour part 1: Neutron stars and pulsars

Stars that are between five and forty times as massive as our sun end their lives in a spectacular way - not with a whimper, but a bang! Once their nuclear fuel is exhausted, there is an gigantic explosion called a supernova, in which the outer layers of the ...

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Cosmology / Elementary Tour part 1: The expanding universe

Together, billions and billions of stars like our sun form gigantic star systems - galaxies like our own Milky Way galaxy, which probably doesn't look all that different from the galaxy NGC 4414 shown here: The cosmological models of general relativity ...

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