Light bending, Dark Matter

[alpha2cen]

We've heard that the size amplification of the far away galaxys is the cause of the DM existence.

How to make this phenomena? Any good opinion?

[imatfaal]

Not sure if it is the cause - it is an effect. The dark matter has mass that contributes to the gravitational lensing effect.

 

Gravitational lensing means that light from a very distant object is 'lensed' ie bent by the mass of the intervening matter - this can be shown with our own sun and follows from general relativity. We can note from the amount of lensing, that the mass of galaxies is greater than we would expect if we used only the amount of luminous matter to calculate the mass of the intervening galaxy - if we include the dark matter postulated for the intervening galaxy then the lensing effect is correct.

 

Dark matter was originally posited to explain the fact that rotating galaxies and galaxies orbiting in clusters do not seem to have enough mass for their speed of rotation. The evidence for Dark Matter was boosted by the lensing effect above. More evidence was provided by the bullet cluster. The jury is still out; because we do not know what makes up the dark matter - but we are pretty sure it is there.

[alpha2cen]

Then, does the dark mass have aggregate property in itself?

And , does it have a mass, too?

[imatfaal]

Not sure what quite what you mean by aggregate property.

 

Dark Matter has mass - its existence was inferred by the gravitational effect it has. It is thought that the majority of dark matter is non-baryonic and does not interact with other matter except through gravity - all that we can be reasonably certain of is that it interacts gravitationally and thus we believe it has mass.

[alpha2cen]

Not sure what quite what you mean by aggregate property.

 

Dark Matter has mass - its existence was inferred by the gravitational effect it has. It is thought that the majority of dark matter is non-baryonic and does not interact with other matter except through gravity - all that we can be reasonably certain of is that it interacts gravitationally and thus we believe it has mass.

 

But to obtain mass, at least the particles(Dark Matter) are collected in the certain region.

The attraction between matter and Dark Matter is another problem.

[imatfaal]

But to obtain mass, at least the particles(Dark Matter) are collected in the certain region.

 

 

It is not the aggregation of dark matter particles that give them mass. They have mass individually as much as any particle - to go deeper you are talking about the interactions with the higgs field.

 

The gravitational attraction between dark matter and luminous matter is practically the only thing we know about dark matter.

 

 

 

 

 

[IM Egdall]

Recent Scientific American has good article on dark matter. Says it is most likely a new form of neutrinos.

Edited January 13, 2011 by I ME

[imatfaal]

Thanks - I will see if I can access to that.

[steevey]

We've heard that the size amplification of the far away galaxys is the cause of the DM existence.

How to make this phenomena? Any good opinion?

 

I can't find the specific link, but the reason there seems to be dark matter in the universe is because there isn't enough visible matter to account for whats happening, by today's calculations. In certain instances, there are large clusters of matter such as two galaxy clusters merging where the matter being observed in certain places isn't enough to bend light the way it's already being bent. So the only known explanation is that there are large quantities of matter which we can't see.

[alpha2cen]

I can't find the specific link, but the reason there seems to be dark matter in the universe is because there isn't enough visible matter to account for whats happening, by today's calculations. In certain instances, there are large clusters of matter such as two galaxy clusters merging where the matter being observed in certain places isn't enough to bend light the way it's already being bent. So the only known explanation is that there are large quantities of matter which we can't see.

 

Then we can absolutely define that phenomena like this.

"There are some places in the space where light is bent."

And our analysis about that phenomena from the present knowledge is like this.

*The only thing light bent is a matter or gravity.

*But at that place electromagnetic wave emission or electromagnetic wave absorption phenomena are not detected.

*So it is not matter. Till now unknown gravity effect has not been observed.

*Only we can state now is that it is unknown matter, i.e., Dark Matter.

Does this logic have any paradox? Our thinking, it is no problem.

[steevey]

Then we can absolutely define that phenomena like this.

"There are some places in the space where light is bent."

And our analysis about that phenomena from the present knowledge is like this.

*The only thing light bent is a matter or gravity.

*But at that place electromagnetic wave emission or electromagnetic wave absorption phenomena are not detected.

*So it is not matter. Till now unknown gravity effect has not been observed.

*Only we can state now is that it is unknown matter, i.e., Dark Matter.

Does this logic have any paradox? Our thinking, it is no problem.

 

I think what that translates to is that light is being bent out of our field of view, but its not just that. By current calculations, there isn't enough visible mass to hold galaxies together as tightly as they are being held now.

[amber r shaffer]

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Moderator Note

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