An accurate description of the physical characteristics of Poland is mainly flat landscape, fertile soil except in the east and northeast, many lakes, large deposits of coal, sulfur, and copper, a mountainous region in the south. <span>Coal is Poland's most important mineral resource.</span>
Amount of sunlight, distance from equator, and height above sea level
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.
their relative densities
Explanation:
The relative densities of the earth's materials can be inferred by the arrangement of the earth layers.
Compositionally, the earth is made up of three distinct layers; core, mantle and the crust.
- The crust is the thin outermost layer of the earth.
- The mantle straddles the zone between the core and crust.
- The core is the innermost layer of the earth.
During the formation of the earth, materials differentiated into different layers based on density.
The densest materials settled in the core and they are made up of iron and nickel metals.
The lightest materials of silicate affinity partitioned to the crust.
The mantle contained materials whose density straddles between the crust and core.
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Answer:
d
Explanation:
desertification is the cutting down of trees the best way to fight the cutting down of trees is to plant more in order for them to grow
