Four Forces of Nature



2) Electromagnetism. This keeps your magnets stuck to the fridge but also keeps the molecules in your body together to form you.

3) The strong nuclear force. The force that sticks atoms together.

4) The weak nuclear force. This is responsible for nuclear decay and radiation.

In a bit more detail Gravity is the most easily recognisable of the four forces as it is what keeps our feet on the ground. It range is infinite as can be seen by looking further out from Earth. The Sun’s gravity keeps Earth in orbit around it, the Gravity if the Milky Way keeps the Solar System in its spiral arm and rotating around it and the gravitational attraction between Andromeda and the Milky Way is what is pulling the two galaxies together. Despite its huge range Gravity is the weakest of the four forces and can easily be overcome (to some extent) by a magnet picking up a paperclip and you lifting your arm. Although lifting your arm requires energy input and cannot be held there indefinitely. The strength of Gravitational attraction is directly related to the mass of an object and every object that has mass exhibits gravitational attraction. The mass of the Earth (5.974×1024 kg) is required to generate the gravitational attraction needed to keep our feet on the ground and it is the Sun’s huge mass that keeps Earth in its orbit. So even you have a minute gravitational attraction to everything around you which you are easily able to overcome. Gravity really is the weakest force.

Electromagnetism is the second most recognisable force as it is what provides the electricity you are using to read this blog post on the internet as well as sticking your fridge magnets to the fridge door. Electromagnetism is a product of different two charges, positive and negative, within particles which then attract each other to give an overall neutral, or zero charge. Within an atom there are protons, neutrons and electrons. Protons have a positive charge, neutrons have no charge and electrons have a negative charge but the protons and electrons have charges that are of the same magnitude but exactly opposite. Therefore within an atom the should be an equal number of protons and electrons to make and electrically neutral atom. Despite working at the small-scale of an atom the electromagnetic force also has an infinite range but is also much stronger than gravity, in the order of 1039 times stronger. It is actually the electromagnetic force that is holding the atoms of your body together, not gravity. The electromagnetic force is also what gives us radio waves that  provide WiFi, mobile internet and microwave ovens to reheat last nights pizza. But, interestingly, the electromagnetic force is also what gives us light which is how we see the world around us. It is all the same force.

The strong nuclear force is exactly that but it is an extremely short-range force that holds the protons and neutrons together in the nucleus of atoms. It’s range is only about 10-15 metres, which is just about the size of a proton. However, it is able to overcome the repulsive electromagnetic force that arises when two protons are pushed close together. Have you ever tried to push the north poles of two magnets together? The repulsive force you feel, and are quite likely not able to overcome and make the poles touch, is the same effect seen when two protons are brought together but if they get close enough the strong force kicks in and ensures they stick together. but only when they are really close together. It requires the heat and pressure at the centre of the Sun to overcome the repulsion of the electromagnetic force and fuse protons together so it is not something you can achieve yourself no matter how hard you try to pouch those magnets together!

The weak nuclear force is also a short-range force, slightly shorter than the strong force at 10-16 metres and comes into play in radioactive decay. It is also involved in the interactions of neutrinos and impart of the reason that neutrinos don’t interact with other particles very often. It is the weak force that is responsible for the decay of a proton into a neutron in which an electron and antineutrino is released. It is also the force that is responsible for all the radioactive elements in the periodic table and governs the way atoms decay and emit the radiation.

There is much more to say about the forces and I will write more blog posts in the future looking in more depth at each force in more detail.

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