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:
B. market
Explanation:
A market economy is an economic system in which the decisions regarding investment, production and distribution are guided by the price signals created by the forces of supply and demand. The major characteristic of a market economy is the existence of factor markets that play a dominant role in the allocation of capital and the factors of production.
Answer:
Air molecules scatter blue light more efficiently than other colors.
Explanation:
The sunlight has many colors and each of them has a different wavelenght. The color blue has shorter wavelengths and higher frequencies than the other colors. So, as sunlight goes through the air, the blue part causes charged particles to oscillate faster than the red part does and it is scattered more efficiently than the other colors and that's the reason for the sky to be blue.
Most fo the hurricanes that affect the east coast of the United States originally form over the warm waters of the Atlantic Ocean in Summer (1). The warm waters of the Gulf Stream run along the east coast of the United States. This provides an environment which is conducive to the development of hurricanes. The basics of the formation of a hurricane are as follows. Winds start blowing in a circular motion. This causes hot, moist air to rise. Clouds are formed and the winds start blowing faster and faster. This forms a low-pressure zone. The surrounding high-pressure zones pull the hurricane towards them. As the hurricane moves, it either picks up speed or decreases its speed and intensity.
Answer:
Proper cleanliness of water..
