General Relativity, first discovered by Albert Einstein and published in the nineteen teens explains how the force of gravity correlates with time and how the earth bends the fabric of space. Imagine that space is a giant stretched out fabric, as you place objects on the fabric they will leave imprints. The bigger the mass, the bigger the imprint. The size of the imprint changes the effects of gravity on the object. For example, the force of gravity on earth is greater than the force of gravity on the moon because the earth has more mass. Black holes have nearly "infinite density". They create giant dents in the fabric of space and their force of gravity is so large that not even light can escape.
The Four Fundamental Forces
Gravity: the first force that was discovered. discovered through an apple falling from a tree. Gravity is a weaker force that attracts over great distances. discovered by albert einstein.
Electromagnetism: it is what its name is, electricity and magnetism. expands through electromagnetic fields.
strong nuclear forces: they are very strong forces that are very strong. they help hold together sub-atomic particles. its the strongest nuclear force.
weak nuclear forces: very strong forces over very small distances. help with radioactive decay.