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.
Darwin is a great example. He created the theory of evolution, but because of the church ridiculing him, he couldn't come forth with his findings. Some parts of science may seem outlandish to society, and that can be very difficult to deal with.
Many observations provide a history that one may be able to surmise theories from.
Answer:
Astronomy is the study of everything in the universe beyond Earth's atmosphere. That includes objects we can see with our naked eyes, like the Sun , the Moon , the planets, and the stars . It also includes objects we can only see with telescopes or other instruments, like faraway galaxies and tiny particles.
Explanation:
Answer:
All of the following are correct except a) they feared taking their conquest overseas,and therefore never built a navy
Explanation:
Mongolian empire was the second largest empire by land area. Under their leader Genghis Khan , the mongols enjoyed great success and at its peak controlled an area equal to the size of Africa.
Under Genghis khan's rule , people were given the permission to practice any religion they want, so therefore we can say that option c) is definitely true.
Under Genghis Khan's rule trade was also encouraged among the people and also the first international post system was also made under his reign, so from this statement we can also conclude that option d) is also correct.
The yuan dynasty which was founded in 1271, by the descendant of Genghis khan whose name was Kublai khan, tried conquering Japan during the 13th century. He sent his navy twice towards the Korea strait to conquer Japan but both of the times his fleets were struck by powerful storms and got wrecked. So from the above statement we can definitely say that the statement a) is false and all other are correct.
