The Fundamental Four

All of the forces and interactions in our universe (based on our current understanding) can be broken down into only four fundamental forces. Even though you may not be aware of them, they are acting on all of us all the time. These forces are responsible for everything, from keeping atoms together to keeping our feet on the ground. A weird concept to grasp, perhaps, is that these forces are actually due to the transferring of certain fundamental particles.

  1. Strong Nuclear (Mr. Fantastic)

The strong nuclear force is responsible for holding together the protons and neutrons inside an atom, which would otherwise be repelled due to the positive charge of the protons, much like Mr. Fantastic binding his team together with his wise words. It is the strongest out of the four forces and acts at an extremely short range, normally between nucleons of an atom. This force is transferred between nucleons through the transferring of a particle known as the gluon which ‘glues’ the nucleons together. This force exhibits a strange yet extremely convenient characteristic. When the nucleons are between 0.5 and 3-4 fm (10-15 m) apart it is attractive which, as I have said, binds together the nucleus which is constantly being pulled apart by electromagnetic forces. However, below 0.5 fm, which is close to the radius of a nucleon, the force is repulsive. If this were not the case, the nucleons would implode inside each other and create black holes, destabilising the entire universe and everything inside so that nothing at all could exist. I suppose we’re pretty lucky, huh?

2. Gravitational (Invisible Woman)

We feel the effect of gravitational force at all times. It is the fundamental force that drives the macroscopic behaviour of the universe as it acts over infinite distances and it acts between all masses. This means that right now, you are being attracted by another galaxy at the other end of the universe. The reason you can’t feel it is because the force is so incredibly weak that it can be considered negligible. In fact, you are currently being attracted, and you yourself are attracting, all the objects in your room (or vehicle or outdoors area) with gravitational forces. Even the Earth, which is quite big I’d say, doesn’t exert a very strong gravitational force. We are easily able to overcome its attraction by jumping or lifting an object upwards. Try it now – get a pen or something and hold it aloft in the air. Feel proud of the fact that you are now overpowering the Earth.

The proposed name of the exchange particle is the graviton but, on the quantum scale, the graviton would be almost impossible to observe due to the extremely small magnitude of the force of interaction. A detector would have to be made the size of an entire planet to be able to detect the extremely rare effects of graviton interactions. However, scientists are making progress and we recently managed to observe gravitational waves from the collision of two black holes (which is also our first observation of a black hole), which you can read about here in our previous posts: Surfing Gravity’s Waves and A Window to the Universe

Ah yes, I almost forgot. The gravitational force is akin to the Invisible Woman because it is so hard to detect. Ahhh? I was quite pleased with myself for that one.

3. Electromagnetic (Human Torch)

The electromagnetic force is another one which we see the effects of in everyday life. Not only do we see and feel the effects of static charge, but the electromagnetic force it the source of the contact forces between objects. In fact, the forces of electric attraction and repulsion of electric charges are so dominant over the other three fundamental forces that they can be considered to be negligible as determiners of atomic and molecular structure. The exchange particle of the EM interaction is the photon, which also acts over infinite distances. However, the strength of the force decreases with an inverse-square relationship to distance, which means that if the distance between the particles is doubled then the force reduces by a factor of four.

I assigned this force as the Human Torch because it was the last one left basically. Also fire light photons sort of? Yeah I’ll go with that.

4. Weak Nuclear (The Thing)

I’ve gotta admit this force is kinda boring (like the Thing) because it doesn’t really have a direct impact on our lives as much as the others do. The weak nuclear force is responsible for certain forms of radioactive decay and is important for nuclear fission which allows the Sun to continue burning, so it’s sort of important in that respect I guess… There are three exchange particles involved with the weak force – the W+ boson, the W- boson and the Z. The weak force is about a million times weaker than the strong force (hence the name) and acts over a very short range ,which is normally within a nucleon, of about 10-18 m. The masses of these particles are much greater than the other fundamental particles, which is another reason why it is like The Thing. I’m so glad that one works too.

These four fundamental forces and their corresponding particles are what make up everything we see and do. Or do they? Recently we have been finding more and more smaller constituent parts, from quarks to the Higgs boson. Scientists are ever delving deeper into the fabric of the universe to uncover what truly holds it together. Will we ever meet an end? Will we find a theory of everything?

Stay tuned,



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