PDA

View Full Version : Matter - Antimatter Imbalance and Questions About the Universe



mugaliens
2010-May-20, 06:38 PM
Some observations, followed by eight specific questions.

Source (http://news.yahoo.com/s/space/20100518/sc_space/whyweexistmatterwinsbattleoverantimatter)


The current theory, known as the Standard Model of particle physics, has predicted some violation of matter-antimatter symmetry, but not enough to explain how our universe arose consisting mostly of matter with barely a trace of antimatter.

But this latest experiment came up with an unbalanced ratio of matter to antimatter that goes beyond the imbalance predicted by the Standard Model. Specifically, physicists discovered a 1 percent difference between pairs of muons and antimuons that arise from the decay of particles known as B mesons.

The results, announced Tuesday, came from analyzing eight years worth of data from the Tevatron collider at the Department of Energy's Fermi National Accelerator Laboratory in Batavia, Ill.

Both matter and its energy-equivalence exert a gravitational attraction. Assuming that of the matter/antimatter generating during the Big Bang, 50.5% was matter and 49.5% was antimatter, and nearly all of the antimatter was annihilated by most of the matter, then just .505% of the original energy-mass in existence then exists today as matter, while of the rest, about half exists in the form of neutrinos and the other in the form of energy.

Furthermore, we know that some, if not much of the original universe lies beyond the comoving distance at which we appear to be at the center.

Summary: According to observations of structures larger than galaxies, as well as Big Bang cosmology, dark matter accounts for 23% of the mass-energy density of the observable universe, while the ordinary matter accounts for only 4.6% (the remainder is attributed to dark energy). - Hinshaw, Gary F. (January 29, 2010). "What is the universe made of (http://map.gsfc.nasa.gov/universe/uni_matter.html)?". Universe 101. NASA website

Question 1: Is it reasonable to conjectur that since the 4.6% of the observable universe (including all energies) is matter, while just 0.505% of the original mass-energy at the beginning was matter, that 910.89 times more mass-energy exists beyond the observable universe?

Question 2: Could this not then be used as a basis for estimating the size of the actual universe?

Question 3: Isn't the age of the universe based only on the size of the observable universe?

Question 4: Isn't that estimate based on several different approaches, all of which appear to reinforce one another?

Question 5: Since some of those incorporate the gravitational constant, and we know there's more out there beyond the comoving distance, doesn't that imply gravity from extremely distance objects which are receeding from us faster than c due to expansion no longer has an effect on those of us at the centerof the comoving distance (yet would still have an effect on those inside the objects' comoving distance)?

Question 6: As the universe continues to expand, wouldn't the mass-energy of the observable universe steadily decline?

Question 7: Wouldn't this mean that some of the constants aren't as constant as we believe?

Question 8: With such an estimate, would this then necessitate a revision in the age of the actual universe, that it's perhaps much older than appears from the observable universe itself?

Ken G
2010-May-20, 09:40 PM
Question 1: Is it reasonable to conjectur that since the 4.6% of the observable universe (including all energies) is matter, while just 0.505% of the original mass-energy at the beginning was matter, that 910.89 times more mass-energy exists beyond the observable universe?I don't think so-- the 0.505% number you quote (I can't corroborate it but I'll take your word for it) applies to what is within any particular volume, so if 23% of the rest mass is dark matter, and 4.6% is baryonic, what you can do with those numbers is take 4.6/.00505 = 911, and ratio that to 23, getting 911/23 = 40 or so. That means there was 40 times more rest-mass-energy in the annihilating matter/antimatter than was in the rest-mass-energy of the cold dark matter when the baryonic annihilation occurred. That's all you can get out of it-- it doesn't make any comparisons to any other volumes, this is true in any large volume.


Question 2: Could this not then be used as a basis for estimating the size of the actual universe?
No.


Question 3: Isn't the age of the universe based only on the size of the observable universe?Yes, and on all that is self-consistent with that.


Question 4: Isn't that estimate based on several different approaches, all of which appear to reinforce one another?
Yes.

Question 5: Since some of those incorporate the gravitational constant, and we know there's more out there beyond the comoving distance, doesn't that imply gravity from extremely distance objects which are receeding from us faster than c due to expansion no longer has an effect on those of us at the centerof the comoving distance (yet would still have an effect on those inside the objects' comoving distance)?
Yes.

Question 6: As the universe continues to expand, wouldn't the mass-energy of the observable universe steadily decline?
It's hard to define what that energy is-- if you count gravitational potential energy, Hawking says it comes out zero anyway. If you don't, then the expansion itself causes the energy to drop. If you just count rest mass, and not gravitational potential energy, then I think you are right-- the acceleration of the expansion causes the rest mass within the observable universe to drop with time.


Question 7: Wouldn't this mean that some of the constants aren't as constant as we believe?
There shouldn't be any direct connection there, the constants don't need to depend on the rest mass within the observable universe. Indeed, I would be tempted to call it an axiom of physics that the constants must stay constant-- if they are allowed to change, it's not clear to me we are doing physics any more, but something a little different, like an evolved version.


Question 8: With such an estimate, would this then necessitate a revision in the age of the actual universe, that it's perhaps much older than appears from the observable universe itself?No, the age comes from applying general relativity to what we see, and everything you've mentioned is included in that process-- we just don't understand how that annihilation happened or how it left a bunch of matter behind.

mugaliens
2010-May-21, 05:06 AM
Thanks for the reply, Ken G.

Some more questions about your answers.

Q1. Why the ratio with 23? If just .505% of the original mass-energy resulted in matter, the remainder is a mix of neutrinos and energy. Since... Ok, I still don't get the 23, but I see my flaw - my approach appears to assume 100% of the matter that was created had remained inside the observable universe while the energy and neutrinos were uniformly distributed, which as we know is false given isotropy and homogeneity.

Q1 ancillary question: Why the discrepancy between the .505% matter resulting from the Big Bang annihilation and the current 4.6%? Could it be that most of the mass-energy has long since radiated beyond the comoving distance?

Q2: If we can obtain an estimate for the ratio of mass-energy inside the observable universe to that of the universe as a whole, could we not assume homogeneity and calculate at least a rough estimate for the size of the actual universe? If so, why not? Why would this ratio not be acceptible or applicable?

Q6:


It's hard to define what that energy is-- if you count gravitational potential energy, Hawking says it comes out zero anyway. If you don't, then the expansion itself causes the energy to drop. If you just count rest mass, and not gravitational potential energy, then I think you are right-- the acceleration of the expansion causes the rest mass within the observable universe to drop with time.

I'm not one to argue with Hawking. As for "mass-energy" I would count all mass and energy i.e. radiated energy in the form of electromagnetic energy, radiated gravitational energy, etc. In my mind, gravitational potential energy doesn't count, as it's simply the snapping back of a stretched rubber band - a zero-sum game, which is what I think Hawking was getting at given the theoretical singularity of the Big Bang.

Q7: Copy on the constants, as I'm familiar with their derivation and the implications of their nature as constants.

Q8:


No, the age comes from applying general relativity to what we see, and everything you've mentioned is included in that process-- we just don't understand how that annihilation happened or how it left a bunch of matter behind.

Are you saying:

A: The age of the observable universe is 13.7 billion years, and we cannot infer anything beyond the comoving distance because we have no infomation of anything beyond that.

or

B: The age of the actual universe is 13.7 billion years, and the most distant observable objects i.e. IAW the WMAP data were that far away when they radiated what we see now, but due to the expansion of the universe happening since then, they're now 46.5 billion light-years distant, and "as the crow flies" currently moving away from us faster than c (again because of the expansion of space, not minkowskian relative frame movement).

ETA: As far as how annihilation happened, if all energy-matter-time was tightly compressed (perhaps time compression allowed energy-matter compression well beyond current physics) then annihilation may have had ample opportunity to occur, with the resulting leftovers of the 0.505% ordinary matter, and about half 'n half neutrinos and radiated EM energy. Under current physics, neither the energy nor the matter could have existed in such densities as they did during the BB. It's a hurdle I keep coming up against time after time, and it's only the relationship between time and gravity which provides for a possible way out, in that either one or the other, possibly both must not have been then as we observe it to be today.

I'll not flesh it out here, as it may or may not be ATM (I just don't know). I will say this relationship was noticed more than 100 years ago. Indeed, it was recently incorporated in a work of fiction entitled The Climax of Disclosure, written in 2003 by Kaimir Malevich, but more importantly, Planck, Einstein, Dyson, and others all made mention of a relationship beyond the well-known time dilation associated with the simple immersion in a gravity field.

So, Ken G., Question 9:

Question 9a: Are you saying aside from relatavistic velocity effects, the aforementioned gravitational time dilation is the only time dilation known?

Question 9b: Or is it possible that gravitational time dilation may have additional factors beyond the traditional Schwartzschild metic which vastly supercede it under BB conditions but which we're still unable to detect being yet a few orders of magnitude shy of cracking the BB nut in our accelerator labs?

Ken G
2010-May-22, 03:46 AM
Q1. Why the ratio with 23? If just .505% of the original mass-energy resulted in matter, the remainder is a mix of neutrinos and energy. That tells you how much energy was light in the very early times. But light loses its energy as the universe expands, and rest mass does not. So that number doesn't mean much today.

Since... Ok, I still don't get the 23, but I see my flaw - my approach appears to assume 100% of the matter that was created had remained inside the observable universe while the energy and neutrinos were uniformly distributed, which as we know is false given isotropy and homogeneity. Comparing to the 23% is just a way to make a comparison with the rest-mass of the dark matter, if one wanted to know what the energy comparison was when the annihilation happened. It's only if you want to know that specific thing.


Q1 ancillary question: Why the discrepancy between the .505% matter resulting from the Big Bang annihilation and the current 4.6%? Could it be that most of the mass-energy has long since radiated beyond the comoving distance?The losses aren't radiated beyond the comoving distance-- the energy density is homogeneous in the cosmological principle. So the same thing happens in every large volume, it makes no difference if the volume in question is smaller or larger than the comoving distance if all you are looking at is various fractional energies.


Q2: If we can obtain an estimate for the ratio of mass-energy inside the observable universe to that of the universe as a whole, could we not assume homogeneity and calculate at least a rough estimate for the size of the actual universe?There's no way to do that-- we have only lower limits on the "universe as a whole." We could get an upper bound on that ratio, and it would be very small, perhaps 1% or less. But I don't know how important that number would be, it doesn't change anything locally.



I'm not one to argue with Hawking. As for "mass-energy" I would count all mass and energy i.e. radiated energy in the form of electromagnetic energy, radiated gravitational energy, etc. In my mind, gravitational potential energy doesn't count, as it's simply the snapping back of a stretched rubber band - a zero-sum game, which is what I think Hawking was getting at given the theoretical singularity of the Big Bang.Yes, the only point of counting potential energy is if you want it all to add up to zero. If you want to track the energy that we observe, then you can count it like you are doing. But note that light (and neutrinos and other "hot" dark matter) loses energy rapidly as the universe expands.


Are you saying:

A: The age of the observable universe is 13.7 billion years, and we cannot infer anything beyond the comoving distance because we have no infomation of anything beyond that.

or

B: The age of the actual universe is 13.7 billion years, and the most distant observable objects i.e. IAW the WMAP data were that far away when they radiated what we see now, but due to the expansion of the universe happening since then, they're now 46.5 billion light-years distant, and "as the crow flies" currently moving away from us faster than c (again because of the expansion of space, not minkowskian relative frame movement).I'm saying B. General relativity will include the effects of all that matter on the expansion, not just the effects of the currently observable universe. Even as the universe accelerates, and less matter is in contact with the gravitational influences of other matter, that's all in the equations already. GR knows that gravity is a signal that propagates at c.



Question 9a: Are you saying aside from relatavistic velocity effects, the aforementioned gravitational time dilation is the only time dilation known? Time dilation is essentially a coordinate effect-- it never happens to the objects actually undergoing the physics in question. Local physics is local physics, and I don't know of any problems presented by the early times in the Big Bang when the annihilation occurred-- except that we are apparently missing the physics that allowed for a matter overabundance over antimatter. I don't think time dilation plays any role in that, time dilation is merely something that appears when we interpret past events in terms of our own clock times.


Question 9b: Or is it possible that gravitational time dilation may have additional factors beyond the traditional Schwartzschild metic which vastly supercede it under BB conditions but which we're still unable to detect being yet a few orders of magnitude shy of cracking the BB nut in our accelerator labs?When you go way past anything we've done in accelerators, you could have any kind of physics we don't know about yet. Cosmic rays give us some idea of what happens at higher energies than in our accelerators, but the event rate there is still pretty low, and they have their own puzzles, so I'd be surprised if there isn't physics that we don't know about yet on higher energy scales.

mugaliens
2010-May-22, 08:38 AM
Wow! Hmm... Great answers, Ken - thank you!

Lots of thinking to do, here. I'll revisit this thread when I'm able.

- Mugs

ETA:


When you go way past anything we've done in accelerators, you could have any kind of physics we don't know about yet. Cosmic rays give us some idea of what happens at higher energies than in our accelerators, but the event rate there is still pretty low, and they have their own puzzles, so I'd be surprised if there isn't physics that we don't know about yet on higher energy scales.

Gotcha. Thanks again for the concise answers!