Answer:
Here is some background information...
Explanation:
Leeuwenhoek (1633-1723) used melted glass balls to form lenses for apparently crude simple microscopes that nevertheless magnified up to 275 times! Modern tests have concluded that he could have achieved a resolution of two micrometres.
The two events that occur when gravity causes a nebula to collapse into itself are:
A. Nuclear fusion start.
B. A new star forms.
Explanation:
- Nebula are giant clouds of dust and gases.
- These clouds are considered as progenitors of stars and planets.
- The gravitational pull within these giant clouds result these large masses to collapse towards their centre.
- The gravitational collapse results in tremendous rise in temperature till a point where nuclear fusion begin .
- The stars are born out of such mechanism and act as a source of heat and light in universe.
The theory of evolution proposed that a series of catastrophes or mass extinctions followed by repopulation could explain why species change over time
Answer:
D
Explanation:
The Moon stays in orbit around the Earth because the Earth's gravity keeps the Moon orbiting us. The gravity makes the Moon accelerate all the time, even it's speed remains constant.
