Dark Energy And Dark Matter
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Observations from the Hubble Space Telescope in 1998 showed that the universe was expanding more slowly in the past than it is today, contrary to expectations. This led scientists to propose either modifications to Einstein's theory of gravity, such as the introduction of dark energy, or the existence of an unknown type of matter, dubbed dark matter, that cannot be detected directly. Dark matter is inferred to make up about 27% of the universe based on its gravitational effects, but its exact nature remains unknown.
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Dark Energy And Dark Matter
- 2. In the 1998 and the Hubble Space Telescope (HST) observations of very distant supernovae that showed that, a long time ago, the universe was actually expanding more slowly than it is today The expansion of the universe has not been slowing due to gravity, as everyone thought, it has been accelerating
- 3. Scientists came up with three explanations It was a result of a long-discarded version of Einstein's theory of gravity, one that contained what was called a "cosmological constant." There is something wrong with Einstein's theory of gravity and a new theory could include some kind of field that creates this cosmic acceleration Still don't know what the correct explanation is, but gave it the name "dark energy“ Roughly 70% of the universe is dark energy
- 4. Its presence is indicated by unexplained gravitational effects on stars and galaxies Much more certain of what dark matter is not than what it is Doesn't emit, reflect, or absorb light. In fact, dark matter does not seem to be composed of the familiar electrons, neutrons, and protons Some of the dark matter is composed of black holes
- 5. Astronomers know dark matter is there by its gravitational effect on the matter that we see, and there are ideas about the kinds of particles it must be made of Dark matter does not reveal its presence by emitting any type of electromagnetic radiation. It emits no infrared radiation, nor does it give off radio waves, ultraviolet radiation, X-rays or gamma rays
- 6. The best estimates of the total mass of everything that we can see with out telescopes is roughly 0.01 M. The other 99% of the stuff in the universe is dark matter
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