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
Supernovae that are moving away at an accelerating rate
Supernovae that are moving away at an accelerating rate is evidence for the existence of dark energy.
The evidence for the existence of dark energy is supernovae that are moving away at an accelerating rate.
The evidence for the existence of dark energy comes from supernovae that are moving away at an accelerating rate. This is known as the observation of accelerating cosmic expansion.
To understand how this observation provides evidence for dark energy, we need to delve into the concept of the expanding universe. In the early 20th century, the Belgian astronomer Georges Lemaître and the American astronomer Edwin Hubble independently discovered that the universe is expanding. This expansion means that galaxies, on average, are moving away from each other.
In the late 1990s, a team of astronomers led by Saul Perlmutter, Brian Schmidt, and Adam Riess made a surprising discovery. They observed that the brightness of type Ia supernovae, which are a specific type of exploding star, was lower than expected. This suggested that these supernovae were farther away than previously thought.
Upon further analysis, the researchers found something even more intriguing. Not only were these supernovae farther away, but they were also moving away at an increasing rate. This observation contradicted the expectation that the expansion of the universe was slowing down due to the gravitational pull from all the matter in the universe.
The natural explanation for this accelerating cosmic expansion was the presence of a mysterious force called dark energy. Dark energy is a hypothetical form of energy that is thought to permeate all of space and drive the accelerating expansion of the universe. However, its nature and origin are still not fully understood.
So, among the given options, the evidence for the existence of dark energy comes from supernovae that are moving away at an accelerating rate. This observation suggests the presence of an unknown energy that is causing the expansion of the universe to accelerate.