The opinions and prejudice of an author in writing.
I believe that those two elements greatly affect bias in history because we can never be 100% sure of everything that (may have) happened in history (especially farther in the past), so opinion can affect a historian's writings. Also, everyone is prone to some sort of prejudice, so this can also affect history.
Answer: Tropic of Capricon
Explanation: the sun rays are directly overhead at the tropic of Capricorn on December 21 and it is called December Solstice
The answer is: convection of the core
