Two parallel lines will intersect at infinity, and become a mirror image of each other. Some theorists have extrapolated this into saying that the universe reflects itself at infinite distance and time. Thus, the universe is its own antiparticle, which allows a universe to exist while preserving conservation of energy, since everything averages out to zero.
If you throw a bunch of energy into a black hole, it becomes impossible in principle to determine its state. This would be the same as reversing entropy, meaning black holes must radiate energy if the laws of thermodynamics are to be preserved.
The human shoulder has one of the widest ranges of motion of any joint in the animal kingdom. This flexibility allows humans to throw things with great accuracy, which was an essential skill many years ago.
The human body is able to survive on relatively little food given its mass, which probably was the deciding factor in why modern humans out competed other hominids.
While it is certain that humans developed in Africa, the actual origin of primates is inconclusive.
Some catfish have developed the ability to slither up on shore, eat land creatures, and slither back into the river. they do this in times of very scarce food, catching animals taking a drink.
Uranium deposits in west Africa were rich enough to undergo sustained fission, forming natural nuclear reactors.
The electromagnetic force has infinite range, but gets exponentially weaker with distance.
While we can use gravity to very accurately predict the motion of bodies, we are at a loss to explain what gravity actually is.
Some scientists have proposed that escaping tachyons caused an area of negative pressure around the early universe, which drew everything else outward, creating the big bang. This theory is probably untestable though.
" One day man will connect his apparatus to the very wheelwork of the universe, and the very forces that motivate the planets in their orbits and cause them to rotate will rotate his own machinery " -Nikola Tesla
If you could travel backwards in time, you could violate Heisenberg's uncertainty principle, making the operation likely impossible.