Four fundamental forces of physics -- explanation for dummies please

[Fellatoor]

I am not sure if this is the correct place to post so I am very sorry if I am posting in the wrong place.

I am looking to have the four fundamental forces of physics explained as simply as possible, I have been doing some online research to try to understand it and I am having a hard time fully understanding the info I'm reading. I would love to understand each of the forces and how they interact with one another.

TIA
Jordan

 

[phinds]

Please explain the forces as you understand them and we can go from there

 

[Fellatoor]

Thank you!

Gravity; technically the weakest of forces but seems strongest because of the nature of mass and how the larger the mass is the stronger its gravitational pull is, it "likes" to clump together. It works on a macroscale.

Weak interaction "Force;" is radioactive decay, where unstable atoms shoot off particles to become a more stable element. This force is very strong on a subatomic level.

Electromagnetic Force; The interaction of negatively and positively charge particles. This force is the "glue" that keeps atoms together, and the reason magnets work.

Strong Interaction; The force that allows the formation of an atoms nuclei to form despite having protons and neutrons of the same charge next to each other. This is the strongest of the forces and also happens on the microscale.

This is my current basic understanding of these forces. I am needing to understand this information for a personal project I'm working on and I really appreciate the help.

Jordan

 

[phinds]

I'll comment on this one

Gravity; technically the weakest of forces but seems strongest because of the nature of mass and how the larger the mass is the stronger its gravitational pull is, it "likes" to clump together. It works on a macroscale.

(1) "seems" is subjective and relates only to how humans experience things. Of the four, we experience only gravity directly so we don't think of the others in terms of what "seems" to be the case.
(2) "force" is not really correct. In Newtonian gravity, yes, it is a force, but to be fully correct, Newtonian gravity does not describe the universe we live in, General Relativity does and in GR, gravity is the geometry of space-time, not a force.
(3) Gravity works on ALL scales, not just a macro scale. It is so much weaker than the other forces that at micro scales it doesn't contribute much but non-zero and zero are not even remotely the same thing.

 

[collinsmark]

Of the four, we experience only gravity directly so we don't think of the others in terms of what "seems" to be the case.

I would say that there are two of the forces that we, as humans, experience on a day to day basis (even people without a scientific background): Gravity and the electromagnetic force.

Gravity is obvious. But the electromagnetic force, together with the Pauli exclusion principle, affect our lives all the time.

First I should mention that the Pauli exclusion principle is not a force. It's a principle that states that no two Fermions can occupy the same quantum state at the same time. It's what keeps an atom's electrons in their orbital "shells" (so to speak; more on that maybe another time) rather than all collapse together into the lowest allowed energy level. It gives rise to atoms' valance states. It's not limited to electrons though, it also keeps particles that make up the atom's nucleus separated from each other.

Now, taking the Pauli exclusion principle as a given, the force that keeps you from falling through the ground to the center of the Earth is the electromagnetic force. Yes, that Normal force that counteracts the gravitational force, thus keeping you on your feet, is the electromagnetic force. It's the electromagnetic forces acting between the atoms on the ground and the atoms on the bottom of your shoes.

If you grab a wooden meter stick and try to pull it apart, you'll find it isn't easy. That force keeping it together is also the electromagnetic force. Pretty much the force that causes any solid object to keep its shape is the electromagnetic force.

Pretty much the whole of chemistry is all based on the electromagnetic force. (And by extension, biology.) At its fundamental level, how do you explain what happens when you combine an acid with a base? Yep, the electromagnetic force. How do atoms fit together into molecules. Yep, electromagnetic force.

It goes without saying that electric motors and generators, current flowing through wires, and the electronics you are using to read this sentence all involve the electromagnetic force.

Ever light a match? Electromagnetic force.

Digesting food? Electromagnetic force.

The strong and weak nuclear forces are much more nuanced (aka. complicated). Most people don't knowingly experience those in such a way as to see them in action. 'Not without fancy instrumentation anyway. [Edit: Smoke detectors exploit the weak nuclear force, as well as some other common items that I can't think of right now. They're not as everyday common as the electromagnetic force though.]

[Another edit: Oh, the Sun's core undergoes fusion, which involves the strong and weak nuclear forces. So there's that. But we don't see that directly. By the time the energy reaches the Sun's photosphere, all the energy is tied up in electromagnetic forces, which is what we see as sunlight (photons are carriers of the electromagnetic force).

The cores of nuclear power plants involve the nuclear forces, obviously. So those too.]

 

[DennisN]

I am looking to have the four fundamental forces of physics explained as simply as possible, I have been doing some online research to try to understand it and I am having a hard time fully understanding the info I'm reading. I would love to understand each of the forces and how they interact with one another.

In addition to the posts written above, here are two sites which may be interesting:

The Particle Adventure: The Four Interactions (with a number of subsections) (very basic)

HyperPhysics - Fundamental Forces: (with a bit more detail)

• Strong Force (also known as Strong Interaction)
• Electromagnetic Force (also known as Electromagnetic Interaction)
• Weak Force (also known as Weak Interaction)
• Gravity (a force in classical physics (Newton), not so in general relativity where it is due to spacetime curvature (Einstein))

 

[DennisN]

Gravity; technically the weakest of forces but seems strongest because of the nature of mass and how the larger the mass is the stronger its gravitational pull is, it "likes" to clump together

By the way, regarding the strength of gravity versus electromagnetism I'd like share a thought-provoking example, which I saw demonstrated in a public lecture I saw recently (regretfully I don't remember which lecture it was). It is about our experience of the forces on Earth:

Yes, gravity seems to be quite significant, since we are attracted* down to the ground by it, which of course is because we are so close to a massive object (the Earth).

But:

Now consider taking two tiny little magnets (e.g. fridge magnets) which electromagnetically attract (or repel) each other, and put them close together so that one is on top of the other, with the north pole of one of them facing the south pole of the other (so there is attraction between them).

Then just grab and lift the top magnet with your hand (and let's call the other magnet the bottom magnet).

They will still stay together. So, the magnetic attraction of these two tiny magnets is perfectly well capable of overcoming the gravitational attraction* between the bottom magnet and the entire Earth.

(* I'm using classical Newtonian gravity in the example above)