which is evidence for the existence of dark energy?
galaxies that are rotating at a constant rate
pulsars that seem to be moving closer at an accelerating rate
black holes that are expanding at a constant rate
supervovae that are moving away at an accelerating rate
supernovae that are moving away at an accelerating rate.
The evidence for the existence of dark energy is supernovae that are moving away at an accelerating rate. This observation was made by studying the light emitted by distant supernovae and comparing it to their expected brightness based on their distance from us. It was found that these supernovae were fainter than expected, indicating that the expansion of the universe is accelerating, and thus suggesting the presence of dark energy.
The evidence for the existence of dark energy is supernovae that are moving away at an accelerating rate.
To understand why this is evidence for dark energy, we need to delve into the concept of the expansion of the universe. Edwin Hubble's observations in the early 20th century showed that galaxies were moving away from us and from each other, suggesting that the universe is expanding. This discovery led to the formulation of the Big Bang theory.
Initially, it was believed that the expansion of the universe was slowing down due to the gravitational pull among galaxies. However, in 1998, astronomers made a surprising discovery based on their observations of distant supernovae. They found that not only were these supernovae moving away from us, but their rate of recession was also accelerating.
This observation was unexpected, as it suggested that some unknown force, which came to be known as dark energy, was pushing galaxies apart and driving the accelerated expansion of the universe.
The other options you mentioned, such as galaxies rotating at a constant rate, pulsars moving closer at an accelerating rate, and black holes expanding at a constant rate, are not specifically related to the evidence for dark energy. Instead, they are unrelated phenomena that do not provide evidence for or against the existence of dark energy.