How has scientific understanding about the composition of the universe changed over time? Select the two correct answers.(1 point)
Responses
The percentage of dark matter has shrunk in scientists' estimates since the 1980s.
The percentage of dark matter has shrunk in scientists' estimates since the 1980s.
The percentage of ordinary matter has grown in scientists' estimates.
The percentage of ordinary matter has grown in scientists' estimates.
The percentage of dark energy has shrunk in scientists' estimates.
The percentage of dark energy has shrunk in scientists' estimates.
The percentage of unknown material has grown in scientists' estimates since the 1970s.
The percentage of dark matter has shrunk in scientists' estimates since the 1980s.
The percentage of dark energy has shrunk in scientists' estimates.
Which is evidence for the existence of dark energy?(1 point)
Responses
Black holes that are expanding at a constant rate.
Black holes that are expanding at a constant rate.
Galaxies that are rotating at a constant rate.
Galaxies that are rotating at a constant rate.
Supernovae that are moving away at an accelerating rate.
Supernovae that are moving away at an accelerating rate.
Pulsars that seem to be moving closer at an accelerating rate.
Supernovae that are moving away at an accelerating rate.
How did dark matter affect the development of structures in the early universe?(1 point)
Responses
It cooled pockets of gas to form nebulae.
It cooled pockets of gas to form nebulae.
It became part of black holes.
It became part of black holes.
It seeded the development of quasars.
It seeded the development of quasars.
It seeded the development of galaxies.
It seeded the development of galaxies.
The correct answers are:
1) The percentage of ordinary matter has grown in scientists' estimates.
2) The percentage of dark energy has shrunk in scientists' estimates.
Over time, scientific understanding about the composition of the universe has evolved. In the 1980s, scientists believed that dark matter made up a larger percentage of the universe. However, since then, the estimates of dark matter have decreased. On the other hand, the estimates of ordinary matter, which includes the familiar atoms and elements we are composed of, have grown in scientists' understanding.
Another significant change in scientific understanding is related to dark energy. Dark energy is a theoretical form of energy that is thought to contribute to the expansion of the universe. Initially, scientists did not have a clear idea about dark energy, but as research progressed, the estimates of dark energy in the universe have decreased.
Regarding the percentage of unknown material, it is not mentioned that its estimates have grown since the 1970s. Therefore, it is not one of the correct answers.