The Sun appears to move across the sky each day. What causes this?

The earth is turning.

Explanation:

when the earth turns it causes the sun to move from one part of the sky to the other. The earth revolves around the sun. So when it become night time for example, the sun is just on the other side of the earth.

the relative atomic mass of an element is the mass of one atom of that element, relative to 1/12th of the mass of a  1212c atom. to convert to an absolute mass in kg, it is necessary to multiply by  1.661×10−271.661×10−27.

the relative atomic mass is roughly equal to the number of neutrons, plus the number of protons, in the nucleus of the atom.

for elements with more than one stable isotope (different types of nucleus with different numbers of neutrons but the same number of protons), the quoted mass is usually the average mass, weighted by the relative abundance of the different isotopes.