Answer:
Dark energy is a theoretical form of energy that is believed to exist in the universe, causing its expansion to accelerate. It is called "dark" because it is not visible and does not interact with light or other forms of electromagnetic radiation.
The evidence for the existence of dark energy comes from observations of distant supernovae. Astronomers found that the light from these supernovae was dimmer than expected, indicating that the universe is expanding at an accelerating rate. This acceleration suggests that there is some sort of energy in the universe that is pushing it apart.
Other evidence for dark energy comes from observations of the cosmic microwave background radiation (CMB), the leftover radiation from the Big Bang. These observations reveal slight temperature variations in the CMB, indicating that the universe is flat and contains a critical density of matter and energy. However, the observed density of matter is not enough to account for the observed acceleration of the universe, suggesting the existence of a mysterious form of energy such as dark energy.
In addition, the large-scale structure of the universe, such as the distribution of galaxies, also suggests the existence of dark energy. The observed structure is consistent with the idea that dark energy is causing the expansion of the universe to accelerate, pushing galaxies apart from each other.
Overall, the evidence for dark energy is indirect but comes from multiple independent observations that are consistent with the idea that the universe is accelerating in its expansion, which is best explained by the existence of dark energy.
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