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:
A. South Africa
Explanation:
from 1948 and into the early 1990s
The sequence is in the following order;
- The sun radiated sunlight (visible) photons
- Photons from the sun strike the earth and become infrared photons
- Earth radiates infrared photons into the atmosphere
- CO2 in the atmosphere absorb infrared photons
- CO2 in the atmosphere emit infrared photons back towards earth
As tectonic plates move things like volcanoes and mountain ridges form. The plates converge causing new physical features to form. They can also move apart creating ridges.
