Related topics: galaxies

How to think about a four-dimensional universe

In Einstein's famous theory of relativity the concepts of immutable space and time aren't just put aside, they're explicitly and emphatically rejected. Space and time are now woven into a coexisting fabric. That is to say, ...

How to make asteroid landings safer

Landing safely on an asteroid is no mean feat. Despite several recent successes, there have also been notable failures—most famously, the Philae lander to 67P/Churyumov-Gerasimenko. Admittedly, that was an attempt to land ...

Image: Hubble captures cosmic cluster

The massive cluster Abell 3322 is featured in this image from the NASA/ESA Hubble Space Telescope, in which the galaxy 2MASX J05101744-4519179 basks in the center. This distant galaxy cluster is a cosmic leviathan that is ...

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Gravitational field

A gravitational field is a model used within physics to explain how gravity exists in the universe. In its original concept, gravity was a force between point masses. Following Newton, Laplace attempted to model gravity as some kind of radiation field or fluid, and since the 19th century explanations for gravity have usually been sought in terms of a field model, rather than a point attraction.

In a field model, rather than two particles attracting each other, the particles distort spacetime via their mass, and this distortion is what is perceived subjectively as a "force". In fact there is no force in such a model, rather matter is simply responding to the curvature of spacetime itself.

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