[thedoc (OP)]

Lionel marr  asked the Naked Scientists:
   
I understand there are two big probems: dark matter - what is it and where does it all come from? And anti-matter - what happened to it after the big bang?

As they both seem to make up large parts of the universe is there any way that darkmatter is what happened to anti-matter after the big bang?

Many thanks,
Lionel.


What do you think?

[syhprum]

I there was an abundance of antimatter in the universe there would be a great deal of gamma radiation at 511 kev due to its annihilation with matter of course this is not seen.
Antimatter reacts with electromagnetic radiation in the same way as normal matter hence it would not be dark !.

[acsinuk]

Most, most interesting syhprum.
What WMAP sees is what there is there. No dark matter because it is not there!  So why pretend the dark force has anything to do with matter?  It can be an electromagnetic or electrostatic force and have no mass at all??  All we need to do is admit there are massless non gravitational forces in space and forget about looking for physical material.
CliveS

[Pmb]

Lionel marr  asked the Naked Scientists:
   
I understand there are two big probems: dark matter - what is it and where does it all come from? And anti-matter - what happened to it after the big bang?

As they both seem to make up large parts of the universe is there any way that darkmatter is what happened to anti-matter after the big bang?

Many thanks,
Lionel.


What do you think?

Dark matter is simply matter which seems to only interact via the gravitational interaction. Antimatter, on the other hand, could have simply annihilated its matter counter part and leaving only matter behind. Mind you that there is no real way to say something like the proton is matter and the antiproton antimatter. It was simply because protons were discovered first. Particles which have the same mass, opposite charge and spin is called its anti-particle. That's about all there is to the difference between the two.

[acsinuk]

Most interesting
If the antiparticle has the opposite charge to the particle touch they will annihilate. But what if we magnetize[spin] them in opposite directions so their north poles face each other and push apart.   
As the electromagnetic force is 10^36G but the weak electrostatic force is only 10^25G this would stop them annihilating, not so?
CliveS

[webplodder]

Lionel marr  asked the Naked Scientists:
   
I understand there are two big probems: dark matter - what is it and where does it all come from? And anti-matter - what happened to it after the big bang?

As they both seem to make up large parts of the universe is there any way that darkmatter is what happened to anti-matter after the big bang?

Many thanks,
Lionel.




What do you think?

I suppose that as anti-matter originated from the same 'primordial egg' as ordinary matter the two might be just two different sides of the same coin. After all, we only have to look at the way life has evolved on earth over many millions of years to see that what was originally very similar has diversified into many forms. The same may be true of matter and anti-matter.

[Pmb]

Most interesting
If the antiparticle has the opposite charge to the particle touch they will annihilate. But what if we magnetize[spin] them in opposite directions so their north poles face each other and push apart.   
As the electromagnetic force is 10^36G but the weak electrostatic force is only 10^25G this would stop them annihilating, not so?
CliveS

Don't think of them as annihilating when they touch since that's not very meaningful in quantum speak. Think of it as them annihlating when their wave functions have significant over lap.

If they were to actually touch the interaction electric energy would be infinite. Bill wouldn't like that. Lol!

[evan_au]

Antimatter is easy to detect. Dark matter has (so far) eluded all attempts to detect it. So they are not the same thing.

There is a hypothesis mentioned by Nobel laureate Richard Feynman that a positron may be an electron going backwards in time. This seems to fit the mathematical equations, but of course, we can't reverse time at will, so we can't actually test this. The same theory applies to other antiparticles too.
Some have speculated that all the antimatter went back in time, but of course, we can't test this either...
See: http://physics.stackexchange.com/questions/391/is-anti-matter-matter-going-backwards-in-time

[jeffreyH]

Antimatter is easy to detect. Dark matter has (so far) eluded all attempts to detect it. So they are not the same thing.

There is a hypothesis mentioned by Nobel laureate Richard Feynman that a positron may be an electron going backwards in time. This seems to fit the mathematical equations, but of course, we can't reverse time at will, so we can't actually test this. The same theory applies to other antiparticles too.
Some have speculated that all the antimatter went back in time, but of course, we can't test this either...
See: http://physics.stackexchange.com/questions/391/is-anti-matter-matter-going-backwards-in-time

Anit-matter pseudo molecules have been created and they don't appear to go back in time. The creation process was a time positive event.

[Pmb]

There is a hypothesis mentioned by Nobel laureate Richard Feynman that a positron may be an electron going backwards in time. This seems to fit the mathematical equations, but of course, we can't reverse time at will, so we can't actually test this. The same theory applies to other antiparticles too.

I fully agree, i.e. it's not meant to be taken literally. It is meant to be taken as something that has the same mathematical form and as evan said, since there is no way to verify that its true you have to take it with a grain of salt.

I did a bit of searching and came to find out that actually, the idea was John Wheeler's idea, but Feynman popularized it.  I'm told that he probably meant it as a cocktail party joke.  It is discussed (in that spirit) on page 65-66 of Introduction to Elementary Particles, 2nd Edition by David J. Griffiths.

[Pmb]

Anit-matter pseudo molecules have been created and they don't appear to go back in time. The creation process was a time positive event.

Why do you refer to them as "pseudo" molecules? I see no reason to refer to them as such, they're just "molecules," plain and simple. That concept can only be applied to sinlge particles, not systems of particles like atoms or molecules.

[jeffreyH]

Anit-matter pseudo molecules have been created and they don't appear to go back in time. The creation process was a time positive event.

Why do you refer to them as "pseudo" molecules? I see no reason to refer to them as such, they're just "molecules," plain and simple. That concept can only be applied to sinlge particles, not systems of particles like atoms or molecules.

They are not stable and exist in an artificially created environment. They also are not composed of the same arrangement of particles as matter. Since we are forcing them into existence I assume they would not arise naturally in physical terms.

[syhprum]

Although a very small quantity of anti Hydrogen atoms have been created I do not think that there has been any evidence of the more common form of molecular Hydrogen forming 

[acsinuk]

Pmb,  you speak of wave function. Have you ever thought of what shape the molecules that are interacting have? From electric point of view any charge with a sharp edge would invite interaction first which may be the reason that quantum are in set energy sizes. More to do with 3D of nucleus position within the shaped volume enclosure, rather than orbits?
Clive S

[Pmb]

Pmb,  you speak of wave function. Have you ever thought of what shape the molecules that are interacting have?

On that level (atomic, molecular, etc.) the only meaning that can be given to "shape" is the wave function. That means that the shape of the object is the shape of the probability distribution.

[acsinuk]

So why would you think that a molecule would be a sphere? It could be any shape and more importantly the electron shells that surround it need to fit together without gaps, particularly if it is a liquid.
CliveS

[jeffreyH]

So why would you think that a molecule would be a sphere? It could be any shape and more importantly the electron shells that surround it need to fit together without gaps, particularly if it is a liquid.
CliveS

A picture tells a thousand words.

http://www.newscientist.com/article/dn11272-microscope-discerns-atoms-of-different-elements.html#.UlPO_9K-pmM

[Pmb]

So why would you think that a molecule would be a sphere? It could be any shape and more importantly the electron shells that surround it need to fit together without gaps, particularly if it is a liquid.
CliveS

A picture tells a thousand words.

http://www.newscientist.com/article/dn11272-microscope-discerns-atoms-of-different-elements.html#.UlPO_9K-pmM

That is merely a repesentation of an atom, nothing more. And in physical reality they're not sphere's by any sense of the term.

That photo appears to be from a tunneling electron microscope which works on the principle of quantum tunneling. The representation is that of the tunnel current which reflects a probability distribution. What you're seeing is a spherical symmetric probability distribution.

[jeffreyH]

So why would you think that a molecule would be a sphere? It could be any shape and more importantly the electron shells that surround it need to fit together without gaps, particularly if it is a liquid.
CliveS

A picture tells a thousand words.

http://www.newscientist.com/article/dn11272-microscope-discerns-atoms-of-different-elements.html#.UlPO_9K-pmM

That is merely a repesentation of an atom, nothing more. And in physical reality they're not sphere's by any sense of the term.

That photo appears to be from a tunneling electron microscope which works on the principle of quantum tunneling. The representation is that of the tunnel current which reflects a probability distribution. What you're seeing is a spherical symmetric probability distribution.

There are other images showing the wave properties.

[Pmb]

There are other images showing the wave properties.

And would you care to share the location of those images with the rest of the class?