About an Hour and 20 mins
Answer:
b. flat rotation curves in spiral galaxies
Explanation:
Dark matter accounts for majority of the matter in the universe (about 85%). It is considered to be composed of subatomic particles which are yet to be discovered. Dark matter cannot be observed because it does not emit light that can be detected. Only its gravitational effect is visible.
Astronomers when calculated the mass of the visible matter and tried to account for the observed speed of stars in the galaxy, there was a mismatch. To understand what caused this mismatch, astronomers gave name to the invisible matter as the Dark Matter.
The expected velocity of stars should decrease away from the near the center of the galaxy but a constant velocity of stars was observed that is a relatively flat rotation curve was obtained.
Thus, flat rotation curves in spiral galaxies in an evidence of Dark Matter.
Answer:
One way that glaciers change the landscape is by erosion. As they pass over the ground, the ice scrapes up soil and rock. A valley glacier will leave a valley much deeper, as it erodes the underlying surface with plucking and abrasion.
The age of the Earth is around 4.6 billion years old
If citizens didn’t meet their duties the economy and judicial system would change terribly
