Answer:
The presence in the air of one or more contaminants in such a concentration and of such duration as to cause a nuisance or to be injurious to human life, animal life or vegetation.
The equator and the International Date Line cross in the area of Pacific Ocean. There is a tradition to celebrate the first sailor's crossing of the line.
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.
A. Spin because in a twirling motion tend to become a spinning type of motion. I think
The two minerals that are found in cement are : Silica and calcite.
<u>Explanation:</u>
Different minerals form the composition of cement but the minerals that are most commonly found in cement are calcite which is contained in the limestone.
The other mineral that is used in the production of cement is silica in the form of raw rock type used to make cement which is found in clay. So they form an important part of formation of cement.