How many forces do we know off in physics?

[hallenrm]

This is on the lighter side, just to pinch our young colleagues! Come on count the number of forces you are aware of, look at the numbers posted by others and correct them if you can. :wave: :D

[Jay-qu]

In order of decreasing strength, Strong Nuclear, Electro-magnetism, Weak Nuclear and Gravity. If my math is right that makes 4 :D though I think some of the forces are linked and appear seperate, while they may actually be manifestations of the same force..

[ronthepon]

Let me take the juicy chance to point out that the strong nuclear force is a 'spill over' form of the quark-quark force.

[Little Bang]

Opinion #1244561

 

I think all the forces in the universe are a manifestation of the positive and negative charges of the quarks, and that includes gravity.

[Tormod]

Lemmesee...gravity, taxation, and death.

[arkain101]

I think there is another force??

 

The Casimir Effect Force:

 

-In physics, the Casimir effect is a physical force exerted between separate objects, which is due to neither charge, gravity, nor the exchange of particles, but instead is due to resonance of all-pervasive energy fields in the intervening space between the objects. This is sometimes described in terms of virtual particles interacting with the objects, due to the mathematical form of one possible way of calculating the strength of the effect. Since the strength of the force falls off rapidly with distance it is only measurable when the distance between the objects is extremely small. On a submicron scale, this force becomes so strong, that it becomes the dominant force between uncharged conductors.

[sebbysteiny]

Firstly, I know somebody was always going to say it, but gravity is not a force. It is just a natural product of 4 dimensional geometry of curved space time. But it does produce a 'phantom' force that does look like it is a force.

 

Also, what about the force of personality?

[IDMclean]

I count six. Casmir, Van der Waal, Elecrtomagnetism, Gravity, Strong, and Weak.

[BrainForce]

Mighty five -

Casimir,electromagnetic,weak,strong nuclear force.

Gravity we take it as a fundamental force, but a new discovery anytime can cause a turnaround.

[Tormod]

Firstly, I know somebody was always going to say it, but gravity is not a force. It is just a natural product of 4 dimensional geometry of curved space time.

 

Tell me - what causes 4D space to curve unless it is gravity?

 

Gravity is a natural product either which way you see it, why does that rule it out as a force? Are you perhaps implying that somehow the other forces are not natural...?

[ronthepon]

I count six. Casmir, Van der Waal, Elecrtomagnetism, Gravity, Strong, and Weak.

Van der Waal's force is a result (a.k.a. spill over effect) of the electrostatic forces of attraction and repulsion, arising from the fact that all positive charge is packed away into a much smaller volume than the negative.

[sebbysteiny]

Tell me - what causes 4D space to curve unless it is gravity?

 

Gravity is a natural product either which way you see it, why does that rule it out as a force? Are you perhaps implying that somehow the other forces are not natural...?

 

Gravity is a natural product of 4d curved geometry. The other forces are natural products of physical laws that create real forces. So the answer is no. To us, it looks like a force. I think the best way to describe it is a phantom force. From another observer, there is no force at all. It is similar to the centrifugal force that seems to be pulling us outwards when infact the force is pulling us inwards.

 

And to prove gravity is not a force, imagine floating in space under the gravitational pull of a few suns, stars and planets. The space ship will meander in and out of the stars. But we inside the space ship will not feel anything. There are two explanations. Either we experience the same force as the ship so it appears there is no force when there actually is. Or there really is no force and it appears to outside observers that there is. According to general relativity, it's the latter and the reason we appear to 'fall' is because we are following a geodesic in curved spacetime. The only reason why on Earth, we feel a constant force of gravity is because of the force on the floor constantly accelarating us upwards compared to the observer stationary in spacetime towards whome we accarate at 9.81ms-2.

 

What causes spacetime to curve?? Mass. Does that make gravity a force?? No. It's just geometry, like pythagorus' theorum. At least, that's the way I see it.

[Qfwfq]

Are the angels male, female, neither, or both? I think they're hermaphrodites.

 

If a spaceship, and each body inside it, all have the same charge/mass ratio then the same would apply. Have you observed the global topology of the universe? Tormod's point was just as good as asking what causes the EM field.

[Tormod]

And to prove gravity is not a force, imagine floating in space under the gravitational pull of a few suns, stars and planets. The space ship will meander in and out of the stars. But we inside the space ship will not feel anything.

 

This example is not very good as it is unverifiable. The sun's gravity well extends so far into space (well, to the next star if we were travelling towards one in particular), and there would not be a fixed area where the two suns' gravity would cancel each other out. the gravity would be far too weak to even measure.

 

No need to travel beyond the solar system for an example. Take the International Space Station as an example. It orbits the Earth, which means that it is in (virtually) free fall. Yet it is constantly being pulled towards the Earth. We need to lift it by tens of kilometers every now and then to avoid it from falling into the atmosphere.

 

Yet on board the station you will not experience any gravity. The force is so weak that it is negligible even at 400 kilometers (which is about where the ISS is). However, at the Earth's surface it is 1 G, which we easily feel. This gravity is not 100% equal around the earth, because it depends on the density of the Earth from the core and out to the point where you measure.

 

That is pretty much a proof that gravity and space-time curvature is one and the same.

 

The only reason why on Earth, we feel a constant force of gravity is because of the force on the floor constantly accelarating us upwards compared to the observer stationary in spacetime towards whome we accarate at 9.81ms-2.

 

So you're saying that gravity is not a force, but there is *another* force accelerating us upwards? Which force would this be? And which observer are you talking about?

 

What causes spacetime to curve?? Mass. Does that make gravity a force?? No. It's just geometry, like pythagorus' theorum. At least, that's the way I see it.

 

Well, this is exactly my point.

 

I would argue that the gravitational force is a property of mass. Without mass, no gravity. The carrier of gravity is as of yet unknown (it could be the graviton, the Higgs particle, or something else).

 

I would also argue that without gravity there would be no mass, because there would be no attraction between large bodies in space (only sub-atomic particles would attract). Thus there would be no stars, and no galaxies. Stars are fueled by extreme gravity pressure causing fusion to happen in their cores.

 

At the same time, we have no anti-gravity shields. It is impossible to shield anything against the force of gravity.

 

Since mass must have come before space-time curvature, at least on local levels (something caused the initial mass to cluster), mass is a result of gravity, and mass causes space-time curvature, which is the manifestation of the gravitational force.

 

My point being, of course, that there is no reason to disqualify gravity as a force simply because it can be called something else. Electromagnetism could also be ruled out as a force, then, because it needs carriers! Without these carriers the force could not interact with anything.

[sebbysteiny]

Yet on board the station you will not experience any gravity. The force is so weak that it is negligible even at 400 kilometers (which is about where the ISS is). However, at the Earth's surface it is 1 G, which we easily feel. This gravity is not 100% equal around the earth, because it depends on the density of the Earth from the core and out to the point where you measure.

 

That is pretty much a proof that gravity and space-time curvature is one and the same.

 

Yes, spacetime curvature and gravity are one of the same. But spacetime curviture is explained through geometry and gravity is explained through a force. The difference depends on the observer. The only scientific difference is that where the two conceptions create differing results (perihelian of Mercury for example), the geometry explanation is correct and the force explanation is wrong.

 

So the way I see it, gravity is just the name for the geometric consequences of living in a 4d universe curved by mass.

 

However, when mass does curve, the information of that curvature is carried allegidly by the graviton at light speed. But from my learning, the graviton is a carrier of spacetime geometric information rather than a carrier of force.

 

However, the same treatment of other fundamental forces like electromagnetic, weak and strong forces DO NOT give correct answers and cannot be explained by geometry. For a start, the concept of relativity does not hold. So they are forces as perceived by all observers.

 

The only reason why on Earth, we feel a constant force of gravity is because of the force on the floor constantly accelarating us upwards compared to the observer stationary in spacetime towards whome we accarate at 9.81ms-2.

 

 

So you're saying that gravity is not a force, but there is *another* force accelerating us upwards? Which force would this be? And which observer are you talking about?

 

There is *another* force accelarating us upwards. It's the tension force of the floor. That arises because the bonds in atoms are being stretched creating a force in the floor that accellarates us constantly against the geodesic of curved spacetime [ie freefall]. The force from those atomic bonds arise out of electromagnetic interactions so that accelaration is caused by the electromagnetic force.

[Tormod]

However, the same treatment of other fundamental forces like electromagnetic, weak and strong forces DO NOT give correct answers and cannot be explained by geometry. For a start, the concept of relativity does not hold. So they are forces as perceived by all observers.

 

What do you mean, the concept of relativity does not hold? AFAIK the only think violating, for example, relativity's predicted speed limit of c is entanglement, something which is not well understood.

 

Maybe you can elaborate on this point?

 

There is *another* force accelarating us upwards. It's the tension force of the floor. That arises because the bonds in atoms are being stretched creating a force in the floor that accellarates us constantly against the geodesic of curved spacetime [ie freefall]. The force from those atomic bonds arise out of electromagnetic interactions so that accelaration is caused by the electromagnetic force.

 

So what is holding us from falling up? Or are we in constant freefall? The above statement needs some backing up. I am not aware of such an effect as you describe.

[IDMclean]

That would be constant freefall towards the common center of mass. We can't fall "up". The electromagnetic repulsion of the ground prevents us from sinking into the ground and the space-time geodesic that we follow prevents us from being pushed out into space.

 

As I understand it attractive forces dominate at long range and repulsive dominate at short range.