Thread: Multi dimensions

We are told that a lot of scientist believe there are 10 multi dimensions, the reason for this, is that gravity should be 10 X greater than it is, why can this not be explained by dark matter / anti matter existing in the same place as matter, this would account for low gravity on earth and the expansion of the universe, if so could we not measure this, as the dark matter would have a force but less than that of gravity. Or do I just not understand things.

Originally Posted by Richard

We are told that a lot of scientist believe there are 10 multi dimensions, the reason for this, is that gravity should be 10 X greater than it is, why can this not be explained by dark matter / anti matter existing in the same place as matter, this would account for low gravity on earth and the expansion of the universe, if so could we not measure this, as the dark matter would have a force but less than that of gravity. Or do I just not understand things.

Your premise is wrong.

ok why?

Originally Posted by Richard

We are told that a lot of scientist believe there are 10 multi dimensions, the reason for this, is that gravity should be 10 X greater than it is, why can this not be explained by dark matter / anti matter existing in the same place as matter, this would account for low gravity on earth and the expansion of the universe, if so could we not measure this, as the dark matter would have a force but less than that of gravity. Or do I just not understand things.

I don't think you're using the words you want to use. As a dimension is something you can give a number to, like mass, length and time.

Sorry if I am not using the correct wording, I am trying to understand why gravity is 10x less than it should be, should I call them multi-universes, but would like to know why my premise is wrong. Is there a known reason why Space/dark matter/anti matter cannot be reducing the force of gravity?

I think the challenge was to your claim that "gravity is 10x less than it should be," and then further that this is the reason multiple dimensions are being actively proposed and considered.

Originally Posted by Richard

Sorry if I am not using the correct wording, I am trying to understand why gravity is 10x less than it should be, should I call them multi-universes, but would like to know why my premise is wrong. Is there a known reason why Space/dark matter/anti matter cannot be reducing the force of gravity?

There's a very good reason why dark matter and anti-matter cannot reduce the force of gravity. Simply, they both increase it. Both dark matter and anti-matter are composed of massive particles and are subject to gravity exactly like regular matter. The difference being that dark matter (seemingly) doesn't interact with photons and anti-matter anhilates when its regular matter counterpart.

Also, according to GR, space is gravity, so that question doesn't even make sense.

We are told that a lot of scientist believe there are 10 multi dimensions, the reason for this, is that gravity should be 10 X greater than it is, why can this not be explained by dark matter / anti matter existing in the same place as matter, this would account for low gravity on earth and the expansion of the universe, if so could we not measure this, as the dark matter would have a force but less than that of gravity. Or do I just not understand things.

I think you are mixing up two different ideas.

First, gravitational force on everyday scales obeys the inverse square law as it has to in a three spatial dimension universe. Some scientists postulate that at very small distances, smaller than we can yet perform experiments on gravity, there might be multiple dimensions. If gravity turns out to be obeying an inverse cube law or some other higher inverse power law at very small distances then this would support the idea of extra dimensions. This would also explain why gravity is so weak compared to the other forces, since the higher dimensions at small scales would reduce its strength rapidly, especially if there are a great many dimensions. It may be many times stronger at tiny distances than it is in the familiar world.

This doesn’t mean it is ten times weaker than it should be. It just means some scientists think it strange that gravity is much weaker than the other forces and this might be one reason for it. I have trouble with this idea for reasons I won’t go into here and I’m not supporting it, just hoping to describe it reasonably accurately for your consideration.

The second idea you seem to be conflating with the first is that dark matter seems to be necessary to prevent distant galaxies from flying apart, since calculations based on the gravitational attraction of normal matter don’t show enough gravitational attraction – more mass is required, hence dark matter.

These are separate but related aspects of the puzzle of gravity.

Many thanks i will have to look more into the aspects you have pointed me too.

Originally Posted by Richard

ok why?

Because it is not right. That ought to be clear.

Now go do some research for yourself.