Question

in 1998, scientists discovered that the expansion of the universe has been accelerating. what force is causing this phenomena? dark energy hubbles law the doppler effect background radiation

Explanation:

• Dark energy: It is a theoretical form of energy that is proposed to explain the observed acceleration of the expansion of the universe. It acts as a sort of "antigravity" and is thought to permeate all of space.
• Hubble's law: This is a statement about the relationship between the distance of a galaxy from us and its recessional velocity (how fast it is moving away from us). It describes the expansion of the universe but does not explain the acceleration of that expansion.
• The Doppler effect: This is a phenomenon related to the change in frequency of a wave (such as light or sound) due to the relative motion between the source of the wave and the observer. It is used in astronomy to measure the velocities of objects like stars and galaxies, but it is not the force causing the universe's accelerated expansion.
• Background radiation: Cosmic microwave background radiation is the afterglow of the Big Bang. It provides evidence for the Big Bang theory but has no direct role in causing the accelerated expansion of the universe.

Answer:

dark energy