Answer: is constant
Explanation:
In order to analyze the velocity of the stars within a galaxy, the <u>galaxy rotation curves</u> (developed by the American astronomer Vera Rubin) are used. These graphs are elaborated as a scatter diagram in which the orbital velocity of the stars present in a galaxy is represented on the Y axis and the distance of these stars to the center of the galaxy on the X axis.
Thanks to this diagram, it has been possible to observe a characteristic behavior in the rotation speed of the stars (and gas) present in the galaxies, which differs from the rules of the orbital movement of the planetary systems postulated by Newton and Kepler.
This means that in these galaxy rotation curves it has been observed that the rotation speed of stars and gas is "constant", regardless of the distance to the center of the galaxy. This discrepancy and these results were then used to demonstrate the existence of dark matter in the universe.
Answer:
B. All of these are drivers
Explanation:
The populations of lot of amphibians, with rare exceptions, are constantly on the decline around the world. The main reason behind this is the human activity, as it has caused lot of changes, pollution, and dangers for the amphibian populations, which has led lot of amphibians to be on the verge of extinction.
The pollution, especially of the waters, has been a major factor for the decline of the amphibian population. Lot of very toxic chemicals have made the water unsuitable for living and poisonous, which systematically killed off the amphibian populations.
The habitat loss, as with any other group of animals, has left the amphibians without places to live. They have been left without their shelters, food sources, mating grounds, and they have started to die out.
The invasive species, especially the predatory ones, have also had big negative impact. The amphibians didn't had any defense mechanism against the introduced predators, so they were easy prey and their numbers rapidly went down.
Answer: The history of Ottoman Bulgaria spans nearly 500 years, from the conquest by the Ottoman Empire of the smaller kingdoms emerging from the disintegrating Second Bulgarian Empire in the late 14th century, to the Liberation of Bulgaria in 1878. ... Bulgaria declared independence in 1908.
So, therefore your answer will be The Ottomans ruled the balkans for nearly 500 years...
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I thought I knew it but I did not
Its lengthy borders touch Germany and Belgium in the north, the Atlantic Ocean in the west, and the Pyrenees mountains and Spain in the south. It also borders the Mediterranean sea in the southeast, and the Alps, Switzerland and Italy in the east.
