Physics We Can All Understand - Part 6: The Four Forces of the Universe

Hi, I'm John Skieswanne, and this post is part 6 of a series on physics. In this series I will explain a few pillars of modern physics. I won't be using any complex maths. It is my hope that this series will introduce some of you brilliant, curious-minded laymen out there to the inner circles of Physics.
So, sit back and enjoy.


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The Four Forces of the Universe

The Strong Force:

Imagine you are in a forest and you find a 4-feet stick from a tree. I ask you to split the stick in two (with no tools). So you hold both ends of the stick with your hands, and with your knee you apply a force that eventually breaks the stick in its center. Now imagine that I ask you to break one of these new, 2-feet long halves of stick. You do the same but the stick is smaller, more leverage is needed, and it takes a bit more time. Then I tell you to the same with the new 1-foot long piece. Difficulty increases. When the stick reaches to a few inches, the task is almost impossible - the leverage is so bad, you'd need more energy than any humans have just to compensate. The more you break the stick into its parts, the more energy it takes to split the parts into even smaller parts, and the more energy-concentrating tools are needed.

Similarily, the strong force, responsible for the structural integrity of the atom's nucleus, is the strongest force in the known universe - a whopping 1000000000000000000000000000000000000000 times stronger than gravitation. In fact, the force has to be strong enough to hold protons together in a nucleus, despite the protons' mutually repulsive electric charges of +1.

But most of all, the strong force is responsible for binding quarks themselves (the very building blocks of protons and neutrons) together to form hadrons or mesons. The force (also called colour force) is being mediated by gluons, which were named this way for obvious reason. It is also the only force to actually strenghten with the distance (but then fall off after a certain point) - this is caused by a complex mechanism.



The Weak Force:

We all heard about radioactive substances, such as carbon-14. Some particles, such as neutrons, cannot survive long if not bonded properly. In atoms with more neutrinos than protons, such as carbon-14 (which has 8 neutrons and 6 protons - that is, it has an over of 2 neutrons), one of the extra neutrons will eventually decay. According to the Standard Model of Physics, neutrons decay as such: the neutron turns into a proton, emitting at the same time a W- boson (carrier of the Weak force), which in turn splits into an electron and an electron antineutrino. So, in a carbon-14 atom, one of the two extra neutrons will turn into a proton, emitting a W- boson which will provide a new electron (and antineutrino).



The atom now has 7 neutrons, 7 protons, and 7 electrons - this is why carbon-14 eventually turn into nitrogen, which happen to be made of 7 neutrons, 7 protons, and 7 electrons.

The Weak force is pretty much the "force of decay". Quite unusual for a force, it is carried by three particles instead of only one. The W- boson is but one of three particles that carry the force of decay; the two others being the W+ boson, and the Z boson. They all carry their own decay modes.

Another unusual thing for a force is the fact that the Weak interactions only affects left-handed particles, whereas all three other forces affect both left- and right-handed particles. Furthermore, all three weak bosons are heavily massive, whereas all other force bosons are massless. And, it is the only force that transforms a particle into another. All this coupled with the practical impossibility to actually observe W-, W+ and Z bosons (according to the Standard Model of Physics their half-life is around 0.0000000000000000000000003 second - their life is so short that they can be considered virtual particles) make the weak force the oddest of all four forces.



The Gravitational Force:

This is the force with the less strenght. Yet it is the most familiar of all four forces. Most (if not all) everyday objects are subject to Gravity. From planets to grains of sand.

Yes, it is true that two object with different weights will actually fall at the same speed to the ground. This is because objects have inertia. "Inertia" is resistance to acceleration - it is the reason why it takes far more energy to push a car than a shopping cart. Sure, the graviational force excerces a greater pull on the 10-pound weight than upon the 1-pound weight. But, the gravitational force also needs to accelerate 10 pounds of resistance to movement instead of only one pound.



So in the end, both objects really end up falling at the exact same rate.

Einstein suggested that gravity was the result of mass as it bends space-time, whereas quantum theorists theorize that gravitation is carried by a particle called the graviton.

Gravitation is posing a problem for the current Standard Model of Physics, for although quantum theorists can give an accurate model for gravitation on macroscopic scales, their model represents not reality at the Planck lenght scale. Furthermore, mass (which gravitation interacts with) is giving trouble to the Standard Model - the latter gives no mass for neutrinos, whereas in reality these particles are known to have (albeit a small) mass.

Newton gives a way to determine the graviational force (F) between two object (object A and object B) with mass A and mass B:

F = G*((massA*massB)/distance^2)

where G is equal to 0.00000000006674. In astronomy, the velocity (V) a body needs to achieve so to stay in orbit (with mass A) around another body (with mass B) is equal to:

V = sqrt((G*(massA+massB))/distance)

With Einstein's theory of General Relativity, though, a few adjustements are made - but Newton's orginal equation is still a rather precise approximation for most calculations.

The Electromagnetic Force:

If an electric current flows through a loop of wire, the curent will emit a magnetic field. This is how speakers work - when a current flows in the coil, the coil becomes an electromagnet, and pulls the diaphragm. Alternatively, if a magnetic field moves across a loop of wire, the magnetic field will induce an electrical current in the wire. This is how electricity generators work - some turbine turns magnets around a coil, and electricity is produced in the coil. Soon physicists realized that both were equivalent - there are two faces of the same force, called the Electromagnetic force.

Electromagnetic force is what governs electromagnets. But neon lighting is another example of electromagnetism working out. This force is conveyed by a massless particle called the photon. The photon is the particle of light. Light is an electromagnetic radiation - a periodic oscillation of an electric and magnetic field, and it carries energy in the from of its frequency. When a neon tube is activated, energy is given to atoms of neons - this forces the energized electrons to move into higher energy orbits. To come back to their original orbit, the electrons need to shed away some of their energy. So they emit a photon, which carries away the extra energy in the form of electromagnetic oscillation frequency (the higher the energy shed, the higher the frequency), and fall back to their original orbit. The runaway photon is the light which the neon tube emits.

It is also the force that governs the interactions of an atom with another. Chemical bonds are carried by valence electrons - their moving electric charges (and spins) generate electromagnetic fields which interacts with surrounding atoms. When you put your hand on something, the atom's electrons in your hand applies an electromagnetic force against the atom's electrons in the thing. Thus your hand's atoms do not merge through the thing's atoms.

The Sun's heat is transmitted to us through its electromagnetic radiation - it emits photons which gets absorbed by our atoms, giving them higher energy and rendering them "hot". And for this, electromagnetism is probably the most important force for life to develop. For without light the entire universe would be a cold, dark place. Photons can be directly converted to electricity using photovoltaic cells - and, in this sense, solar (and other sources of electromagnetic radiation) energy is the closest thing we currently have to free energy.

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So, basically, our universe is run by four forces, three of which are most needed for life:



Sometimes forces such as centrifugal force are confused for one of the four forces. This is a common misconception - actually, centrifugal force is a "fictitious" force, along with the Coriolis effect, caused by acceleration of an object alone and not by any actual common force carrier.


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I hope you enjoyed this read; Part 7 will be coming soon, and will deal about another popular aspect of modern physics.


Swan


Other parts of the series:

-Part 1: the Uncertainty Principle
-Part 2: the Special Theory of Relativity
-Part 3: Quantum Entanglement
-Part 4: The Standard Model
-Part 5: Zero-Point Energy

a reply to: swanne

Awesome, building an ATSintern physics library? Swanne!

a reply to: swanne

Minor nitpick. Try to be more rigorous with your use of the terms force and energy.

Inertia and Gravity look like to me two different forces moving against each other, and same observation I can make with magnetic opposite poles lines of force moving against each other. This observation makes me believe a correlation exists electro magnetic force and gravitation force and inertia and that these forces are all dependant on motion. The rate of motion defines the unit of time as the observer experiences it, and measures it against a point of reference. Possibly the basic unit of time is measured by the measuring the motion 1 revolution of a body around a reference focal point, which on a macro scale of the solar system we see the earth moving around the sun.

nice work thanks for not hoarding the information and making it available to people like me

a reply to: AthlonSavage

Inertia is not a force. It is in most general terms the resistance to change. Or to put it differently, the tendency of a system to mantain its state.

But you are right in saying that it is related to forces, as that is how one usually changes the state of something, by applying a force.

originally posted by: AthlonSavage
Inertia and Gravity look like to me two different forces moving against each other

Actually inertia is not a force, it's a resistance to acceleration. It is not "moving" per say at the opposite direction of gravity, it is actually a resistance to new motion towards gravity. In zero gravity, you still need more force to push (accelerate) a 10-pound weight than as 1-pound weight. Inertia is not an "antigravity", is simply a motion dampener.

A star nevertheless for the original thought!

There's many way to interprit this.

As for the boson. Isn't it obvious that by accelerating mass in such an area such as Earth with the magnetic forces of the planet are strong. When the particles smash together, it is consuming as much energy as they are sending at each other.

By the time the mass has a chance to recombine, it's so energy depleted it bleeps out of existance.

It's pretty clear what the observations are showing.

I don't know how they could interprit it any other way. Obviously head on collisions by acceleration are not what create all the matter in the universe. It's going to be a bit more complicated than that.


And wouldn't gravity just be the collective magnetic force generated by all the matter on earth? A spec of dirt might not be very magnetic but it holds a charge. Miniscule but non the less. Increase the surface area *The whole planet* And you would have your explaination of Gravity. And why it so weak. Go somewhere where the magnetic forces are insain and i'm sure gravity won't even be noticable at all. Since your entire body would be drawn towards the planets surface, For obvious reasons.

awesome work! maybe we can get this archived, "intro to advanced physics for the novice conspiracy theorist" or something haha. good stuff.

originally posted by: swanne
The Electromagnetic Force:

Nice. The only thing I'd add is this diagram showing that the Weak and Electromagnetic interactions are two different manifestations of the "Electro-Weak" interaction:

www.physics.utah.edu...

In particle physics, the electroweak interaction is the unified description of two of the four known fundamental interactions of nature: electromagnetism and the weak interaction. Although these two forces appear very different at everyday low energies, the theory models them as two different aspects of the same force.

I remember, (many years past) attempting to test the "all objects fall at the same rate" experiment from my bedroom window using a ball of tissue and a tennis ball...obviously they didn't fall at the same rate.

I was missing a crucial piece of information, which also appears to be missing from your post (apologies if its there and I just can't see it), and caused no end of confusion until it was finally cleared up for me a short time later.

Three missing words that make all the difference...."in a vacuum".

Objects fall at the same rate regardless of mass...in a vacuum.

a reply to: moebius

Inertia is not a force. It is in most general terms the resistance to change. Or to put it differently, the tendency of a system to mantain its state.

The issue I have wit this statement is there is no way presently in science to test this statement with 100% surety. An observer could see it as your explained but another observer like myself will see it as a possibility. Its pointless to argue until science has irrefutably identified true nature of what gravity and magnetic forces are.

a reply to: Arbitrageur

Indeed, thank you for adding this information to the thread.

Though merging the weak force with electromagnetism is more of a theoretical model point than a physical point.

originally posted by: AthlonSavage
The issue I have wit this statement is there is no way presently in science to test this statement with 100% surety.

Actually there is. You can even carry out the experiment yourself.

Let us say Moebius and I are wrong, and inertia is actually a force working at the opposite direction from gravity.

Then it means that when an object falls at Earth, it is subjected to two forces - the gravitational force accelerating the object in the direction of the fall, and the inertial force which is pulling the object in the other direction (back at space), slowing the object's fall.

Then let us place a basketball ball in a tank filled with water. The ball is floating upon the water, and we thusly cancelled its gravitational acceleration. Yet the ball still has mass, and thus an associated inertia. If your theory is right, this inertia force should continue acting upon the object. Which means, the basketball (whose acceleration at Earth has been cancelled by its buoyancy) should start levitating back up at the sky, since the "force" of inertia would then exceed the earthbound acceleration of the ball (here zero).

If the ball does not levitate, then it means no "antigravity" force is at work, and, by extension that inertia is not a force opposed to gravity but really just a motion dampener.

originally posted by: AnuTyr
And wouldn't gravity just be the collective magnetic force generated by all the matter on earth?

Um, not all matter is magnetic, yet all matter is subjected to gravity.

Plus, your proposition implies that a strong magnetic would act like an artificial gravity, to which anything (not just metallic things) would be attracted. Magnetic compasses would not point at the magnetic pole, but at the center of the Earth instead.

originally posted by: idmonster
Objects fall at the same rate regardless of mass...in a vacuum.

Friction with air is not one of the four forces - therefore it is not mentioned in my OP.

But, of course, vaccum is indeed implied by "Objects fall at the same rate no matter their mass".

I did the experiment too when I was a youngling - using a feather and a marble. I realized that this principle was valid on places such as the Moon, but that atmosphere will indeed slow a lighter object's fall. Physics is full of twists like this.

Excellent thread, most informative and well presented, mind if i link it in my sig?

S+F

So, who's to say Bob Lazar wasn't right? When he said the strong force is actually gravity. As lately, I'm hearing that gluons make up both the strong force and gravity. Kind of interesting if you ask me.