In the world of hard science, especially physics, there are four fundamental forces. We feel one of them every minute of every day — gravity. Things, such as the earth, pull on other things, such as you, and bring them together. Isaac Newton put together the original theory in 1665. (Albert Einstein modified the way we look at gravity when he wrote about relativity in 1915.) If it weren’t for gravity, everything would be floating free in space, and, for that matter, there probably wouldn’t even be anything you could call space anyway. Luckily for us there is gravity, so we have a world we can stand on, with air, to talk about it.
The other force that we experience every day is electromagnetic. It’s a very important force for us. Lights work because of electricity. So does your body and, most scientists say, every thought in your brain. Souls are involved in that, too. Electrical forces are responsible for powering automobiles and for allowing plants to grow and just about everything concerned with life on our planet. The first work on understanding this force was done in the 1750s. Benjamin Franklin was one of the most highly regarded scientists working on the problem.
The results of the third force, although not the third force itself, also are experienced every day. (Some would say not here in Seattle, but that’s a different discussion.) This force is the strong nuclear force. It’s what powers the sun (and atomic bombs and the few still-working nuclear power generators). The strong force was first proposed in 1935 by Hideki Yukawa. We don’t experience the sun’s strong nuclear force directly, though. It is converted into light (a kind of electromagnetic force) and comes to earth that way. This is an important point. One force may be converted into another force.
There is one more force, the weak nuclear force. Nuclear physicists noticed that some energy was always missing in beta decays. Most of you reading this could care less. In 1930 Wolfgang Pauli proposed the existence of the neutrino to explain the discrepancies. Enrico Fermi’s 1934 paper proposed a weak nuclear force to provide the first viable description of beta decay. This is important to you only because it shows that scientists are willing to create forces when it suits them and “all of science” is not destroyed when a new force is created.
And that is why I’m perfectly happy to add life force to the list.