What comes to your mind when you think about physics or someone asks you about the definition of physics? For me, its nature. What is Physics? Physics is just trying to understand and discover about the laws of nature. The laws of nature govern literally everything in this universe. The laws of nature or the laws of physics, whatever you say it’s correct. Classical Physics is the study of laws of nature at a large scale, where if you say a particle, it is not a particle but a body with smaller mass than the other (reasonably smaller mass). Quantum Physics is the study of laws of physics at a subatomic level (level of atoms where the laws of classical physics don’t apply). The laws of nature or physics don’t apply to the quantum world, but can’t keep the natural forces of nature apart, can you? The forces of nature do apply to the quantum world. Well when we study about the forces of nature, we study about them at both the subatomic and classical scales. So, we don’t categorize them as forces at different scales, we consider them as 1 force per se acting on both the scales with the same behaviour (might be different behaviour). The Nature is such a beautiful thing in this world and physics is all about exploring it and that is why I like physics so much. Talking about Forces, let’s dive deep inside the topic and learn something new about the nature today.
There are 4 recognized forces of nature:-
- Gravitational Force
- Electromagnetic Force
- Nuclear Force
- Weak Force
Gravitational Force
The Gravitational Force is weakest of them all. The strong nuclear force is 10³⁸ times stronger than the gravitational force, moreover the electromagnetic force is
10³⁶ times more powerful and the weak nuclear force being 10²⁹ times more powerful. Yeah that’s how weak gravity is. The force found in black holes which suck in everything, the force found in the Earth, the sun and many more celestial bodies. It is so crazy to think that the force which can bend light, more shockingly bend the literal fabric of spacetime and requires a velocity higher than the highest velocity in the universe (the speed of light) to escape is the weakest force. When 2 bodies of masses attract each other, it is because of gravity. When an apple falls down on Newton’s head, it is because of gravity. Everything which has mass, including you reading this blog by a smart kid has gravitational force! Crazy to think about, right? Then you would ask me “why can’t I pull?” uh that I can’t answer, maybe you are too small! The bigger the mass, the stronger the gravitational pull (or just pull). Even my cat has gravitational pull in this modern era, just that it’s too small. Basically, everyone has pulling ability. I have talked about gravity a lot in my previous blogs, so I don’t think we need to talk about it too much. Let’s cut this in short: When 2 bodies of mass, pull each other (classical physics scale, not human scale), it happens through gravity. The effect of Gravitational force is negligible at the quantum scale.
Electromagnetic Force
Particles may exert upon them, electromagnetic force which you may know as Electricity. Maxwell’s equations are all you have to study to know about Electromagnetism but I don’t want to go down that road, let’s take the easy road. All righty, electrons orbit the nucleus in their shell, this happens because of the electromagnetic force. Atoms combine to form molecules due to electromagnetic force. When you put a book on a table, the table exerts an upward force to hold it, this force comes from the electromagnetic forces acting between the atoms and molecules of the book and the table. I talked about both the classical physics and quantum physics scale and you didn’t even notice.
Nuclear Forces
When you hear the name Nuclear Force, you think about nuclear fission or fusion and you are not wrong, all of this happens because of nuclear forces (isn’t that why it's name is "nuclear" force?). Imagine if both the electrons are removed from the nucleus of a helium atom. The protons will start repelling against each other because both of their charge is positive (Remember? Different-attract and Same-Repulse) and this will happen due to the coulomb force (this force describes the electromagnetic force so you can take it as electromagnetic force) and the protons will try to break the nucleus while the neutrons would be just chilling there because they don’t have any charge so they don’t have a role, you don’t matter! The question here is why does the electromagnetic force fail to break the nucleus? Because of Nuclear Force! These forces are short ranged. They are the most powerful forces. These are the forces responsible for holding the nucleus together, otherwise they would repel away from each other due to electromagnetic force. These forces are much weaker than the electromagnetic force if the distance between the particles is more than
10-¹⁴ m³.
Weak Forces
These forces are also known as weak nuclear forces. They are the forces responsible for radioactive decay. Example- A neutron can change into a proton and emit an electron and an antineutrino. This process is known as ß– decay. Even a proton can change itself into a neutron and emit a positron and a neutrino. This process is known as ßplus decay. Weak Forces are responsible for these changes. The range of weak forces is very small, smaller than the size of a proton and a neutron. That is why they take place only in these particles. So we can say that the forces responsible for reactions related to protons and neutrons are known as Nuclear Forces (both weak and strong).
Time for a fact. The most shocking fact I know about physics is that the nucleus occupies a volume of about 10-⁴⁴ m³. The atom itself has a volume of about 10-²³ m³. The nucleus only occupies only 1/10²¹ of the volume of the atom, yet it contains about 99.98% of the mass of the atom. For your reference, the volume means how much space an object takes up and mass means how much matter an object contains.
And that is it for today. Nice little trip to explore the forces of nature, huh. Remember, weak force is too short ranged for classical physics. Gravitational force on the other hand is negligible in the quantum world. The nature is just beautiful. Physics is all about discovering the nature and that is why I like it.
BY,
Deeparsh Bhanot
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