[peterhousehold (OP)]

I’ve often heard it said that gravity is a very
weak force, and that this weakness is a
puzzle requiring an explanation.  The fridge magnet is a favourite
example used to demonstrate how much stronger
the force of magnetism is than gravity.
Yet the fridge magnet example says to me how very local the force of
magnetism is, whereas by contrast gravity’s
influence stretches over colossal distances.
Why then I wonder is the force of
gravity widely regarded as puzzlingly weak?
 

[thebrain13]

the magnets force spreads over a distance as well, they both lose strength at the same rate f=1/d^2 the inverse square law. The puzzle is how is gravity and electromagnetism unified under one theory, when they are so colossally different in strength. How can a force which is billions of times weaker than another possibly be related to another.

Before maxwell there were two seperate theories to explain magnetism and electric force, maxwell unified the two under one theory electromagnetism, and later einstein explained how magnetism was caused by electric force and motion. Magnetism and electric force are much more comparable in strength, thats how they were able to unify them under one theory and mathematics. For example at the relative speed of light, the strength of electric charge and magnetism are exactly equal. Gravity and electromagnetism, they are nowhere near equal, the entire gravitational strength of the entire earth, isnt as strong as the electric force from the surface of the chair to my behind. The mystery is explaining how two radically different forces are related.

[lightarrow]

I’ve often heard it said that gravity is a very weak force, and that this weakness is a puzzle requiring an explanation.  The fridge magnet is a favourite example used to demonstrate how much stronger the force of magnetism is than gravity.
Yet the fridge magnet example says to me how very local the force of magnetism is, whereas by contrast gravity’s influence stretches over colossal distances.
Why then I wonder is the force of gravity widely regarded as puzzlingly weak?

Gravity influence stretches over colossal distances just because there are colossal masses involved. Electromagnetic forces too would have influence on colossal distances, provided that great amounts of electric charge (coulombian force) or electric currents (magnetostatic force) were available, and in that case, EM forces would be enormously bigger.

To make a real comparison, we can evaluate the gravitational and the electrical force among, say, 2 electrons separated by a distance of 1 metre:
gravitational force:         ≈    7*10^-71 N
coulombian force:          ≈ 2.5*10^-28 N

So, coulombian force is ≈ 3.6*10⁴² times the gravitational force.
That is: 1 million of trillions of trillions of trillions times.

Why this huge difference in strenght? This is the mistery.

In some theories, someone proposed this explanation: gravity, differently from other forces, actually acts on more than 3 dimensions; what we observe would be the effect on our 3 dimensions only and so only a part of it.

[lyner]

Electric charge has two signs - positive and negative. It is very hard to get more than a fraction of a coulomb ON ITS OWN in any one region. Opposite charges rush in due to the enormous fields set up. The presence of these opposite charges neutralises the effect - cancelling it out, largely. We would only be aware of the 'unbalanced' charge on a distant charged object.

As we don't have a lot of (or even any?)  antimatter between us and all the stars, planets etc. we get the full whack of their gravitational effect, even though it is 'small'.

Magnetic fields  are formed from so called magnetic dipoles or loops of current. The fields follow endless loops  and, unlike masses and charges, their effect doesn't drop off as an inverse square because the field doesn't radiate outward with spherical symmetry.  You can't get an isolated pole. The effect at a distance drops off faster for this reason and, also,  dipoles can, again, cancel out their effect. The Earth's field is quite significant at huge distances - which save us from a lot of trouble from cosmic rays.

[syhprum]

Sophiecentaur

Anti matter differs basicly in the eletrical charge of its components, as far as gavity is concerned it behaves in the same way as matter.

[lyner]

oops!

[DoctorBeaver]

I recently read a book that tried to explain gravity in terms of particles stuck on a brane. If gravity were the result of 1 such particle and the brane it is on is separated from the brane on which our observable 3 dimensions, along with the particles that carry the other forces, reside it's effect would be weakened by the inverse square law before it reached us. I couldn't follow the maths involved as I only have a little beaver brain which begins to melt at the thought of anything more complex than 2+2, but the book stated that if these branes were warped in certain ways then the theoretical power of gravity which the maths give would equal that which we observe.

[Soul Surfer]

If gravity was not so weak in relation to the other forces the universe could not be as large long lasting and complex as it is and almost certainly could not contain complex beings like us that can observe and comment on it.  Several other physical laws are finely balanced to allow complex physics chemistry and life.

In some way this is a bit like an extension of the complex ecology on our planet that allows us to live and I propose that the process has evolved to create longevity and complexity.  This is of course not for our benefit but because that is the fundamental way that our universe (or any other universe) would work.

Let me explain.

We can see that, in the past, things were very hot and dense this is sometimes called the big bang.  We know that from the uncertainty principle physical laws get more and more blurred as energies get higher and so physical laws become more flexible.

The interactions between subatomic particles that create atoms take place incredibly quickly so there can be absolutely enormous numbers of them if the universe is hot and dense.  Any interaction that in some way extend this time would be favoured because as time went on these sorts of interactions would be around for longer.  at least two sorts of interactions can do this firstly those that recycle things to do something because they can keep on happening even if they last a short time and secondly those that extend the interaction time like particles linking together into stable forms like protons and eventually atoms.  angular momentum has a lot to do with this.

I suggest strongly that this will be the eventual reason why it is that we find our universe so finely balanced it evolved that way just like any other universe starting in the same way would.

This is an idea that is gradually growing in the scientific community but is not embraced by all at the moment

[DoctorBeaver]

That's a nice theory. However, wouldn't there would have to be specific starting conditions for it to happen? For instance, if the initial boost (or Big Bang) was not particularly energetic, the baby universe could collapse before anything significant happened.

Surely, for the interactions that you describe to take place the initial conditions must be very similar, if not identical, to our own universe.

Please correct me if my assumption is incorrect.

[jolly]

deleted as inapproprate

[Soul Surfer]

I am not suggesting that the results would be exactly the same every time,  If you re ran evolution on the earth the results would not be the same.  What I am saying is that its not all that supprising that the results are finely balanced and depend on processes that recycle things or favour processes that extend the effective interaction time of the basic elements.

quarks interact to create hadrons
protons neutrons and electrons interact and recycle to create atoms
Stars use weak gravity to recycle to create more complex atoms
Atoms interact to create chemistry etc

The fundamental process seems to be the recycling of universes them selves via black holes
see Lee Smolin  "life in the universe"

[lightarrow]

I am not suggesting that the results would be exactly the same every time,  If you re ran evolution on the earth the results would not be the same.  What I am saying is that its not all that supprising that the results are finely balanced and depend on processes that recycle things or favour processes that extend the effective interaction time of the basic elements.
quarks interact to create hadrons
protons neutrons and electrons interact and recycle to create atoms
Stars use weak gravity to recycle to create more complex atoms
Atoms interact to create chemistry etc

The fundamental process seems to be the recycling of universes them selves via black holes
see Lee Smolin  "life in the universe"

According to Christopher J. Conselice: The Universe's Invisible Hand - Scientific American_February 2007,
it could be the opposite, black holes actions are becoming less important, matter is been diluting more and more by Dark Energy's relentless action on expanding the universe.