The Four Fundamental Forces

0:00There are four fundamental forces, the basic pushes and pulls behind every other force. Which one is the strongest?

0:09Many people guess gravity, because it holds us on the ground.

0:13Gravity is the force that pulls all masses toward each other, and it reaches across whole galaxies.

0:20The weak nuclear force causes some radioactive decay, when an unstable nucleus gives off radiation, and it helps power the Sun.

0:30The electromagnetic force, which covers electricity and magnetism, holds atoms and molecules together and carries light.

0:39The strong nuclear force holds protons and neutrons together in the nucleus. It is the strongest force, but its range is very short.

0:49Is gravity really the strongest? Test it with a small magnet and a paper clip.

0:55The whole Earth pulls the clip down by gravity, and the magnet pulls it up by electromagnetism.

1:02The clip jumps up: a tiny magnet beats a whole planet. Gravity is the weakest force.

1:09Gravity feels strong because it always pulls, so all of Earth's huge mass adds up to a big pull.

1:17From strongest to weakest, the order is: strong nuclear, electromagnetic, weak nuclear, and gravity.

1:26Physicists think that in the first instant after the Big Bang, all four forces may have been one single force.

1:34This idea is still being tested, so it is not proven yet.

1:39So there are four fundamental forces, and gravity, which holds galaxies together, is actually the weakest.