The Universe, Simulated

A portion of the EAGLE simulation showing gas compressed into filaments in the early universe. Blue, gree, and red shows gas of increasing temperature.

A portion of the EAGLE simulation showing gas compressed into filaments in the early universe. Blue, green, and red shows gas of increasing temperature.

Some 380,000 years after the Big Bang, when light could finally travel freely through space, the early universe was as smooth and featureless as a bowl of consommé. So how did the universe progress from such a dull and unpromising state to its current lumpy configuration full of galaxies and stars and planets?

A recent supercomputer simulation project called EAGLE (Evolution and Assembly of GaLaxies and their Environments) confirms and shows in great detail what has long been suspected. The tiny fluctuations in density in the early universe were magnified by gravity, with dark matter slowly congealing into denser clumps and filaments which then drew in hydrogen and helium gas where it formed into the first stars and galaxies.

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The Elephant in the Universe: Dark Energy

accel_expansionIn our brief look at dark matter, you found more than 80% of the matter in the universe is a type of particle or particles that emit no light, interact very weakly with matter in our everyday world, yet exert profound gravitational influence on the rotation of galaxies and the movement of galaxy clusters. Although particle physicists have a few good ideas, no one knows for sure what this dark matter might be, which is a little unsettling. But it gets even stranger because astronomers have since discovered most of the universe is made not of matter but a strange and unidentified type of energy– “dark energy”– that accelerates the expansion of the universe and may one day carry distant galaxies forever out of view.

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The Lazy Person’s Guide to Dark Matter, Part 2

abell-383-galaxy-clusterIn the first part of this ‘lazy person’s guide to dark matter’, you learned of the unsettling conclusion that four-fifths of the matter in the universe is unidentified, revealing its presence not by emitting or absorbing light but by exerting through gravity an influence on the motion of galaxies and galaxy clusters. All attempts to explain this so-called “dark matter” in terms of known particles and objects– everyday atoms and molecules, dust, dark stars, and rogue planets– have so far failed, and astronomers and physicists have slowly turned to more exotic possibilities to account for dark matter. Although dark matter remains unexplained, observations and calculations of galaxy motion and the structure of the early universe have given astronomers a good idea of its key properties. Particles which are candidates for dark matter must be…

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The Lazy Person’s Guide to Dark Matter, Part 1

Let’s continue our occasional series on the basics of cosmology with a look at dark matter, an elusive substance which enabled the formation of the first galaxies, helps govern the large-scale structure of the universe, and which very likely is passing through your body right now completely unnoticed.  In this article, we look at what dark matter is not. In the next, we examine a few ideas about what dark matter might be.

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Gravity’s Lens

Einstein_Ring_from_HubbleIn 1919, the great British physicist Arthur Eddington led an expedition to the island of Principe off the west coast of Africa.  His mission?  To test an astonishing prediction made by the physicist Albert Einstein, a prediction that massive objects warped the very fabric of space through which they traveled.

Eddington measured the position of stars just adjacent to the Sun, a feat made possible by the solar eclipse expected in Principe on May 29, 1919.  If Einstein was correct, the measured position of the stars should deflect slightly from their expected position as starlight followed a path through the slightly curved space near the Sun.  Eddington made the measurements, and a year later, after careful consideration, declared the position of the stars shifted by exactly the amount predicted by Einstein’s theory.  The news spread quickly, and Albert Einstein became the most famous physicist in the world.

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