Summary of the Third Session (Fri,Sept. 29,1995)
Lecture by Eberhard Möbius on the early universe
Student questions and reactions to lecture Introduction to Fri, Oct. 13's session with comments on religion by professor Paul Brockelman
The Early Universe, Eberhard Möbius:
The background radiation comes from an age of the universe of 300,000 years. Is there any chance to go even further back in time? In order to get information about this early universe we have to resort to more detailed modeling. The clues we can tap here is the mixture of the elements in the universe, in particular, the very light ones H, He, Li, since they were formed in the beginning of the universe, when it was hot enough for nuclear reactions. We are talking about the cosmic cooking recipe.
Viewgraph: cooking recipe
We can extrapolate the density in the early universe at least to an accuracy of 1-2 orders of magnitude, and this determines the He/H ratio exactly to the amount observed today. Therefore, we have a 3rd independent support of the Big Bang model. [How do we know the connection of the recipe with the Big Bang? In the beginning it was so hot that nothing but protons and neutrons were buzzing around. After cooling slightly the environment became less favorable for neutrons, because they are slightly heavier than protons (or having more energy according to E = mc2). In the kinetic gas theory we can calculate the fraction of particles with a higher energy for a given temperature. Only as long as the neutrons found proton partners before they decayed on their journey, i.e. as long as the matter was dense enough, they could survive in deuterium. This happens to reflect the fraction of neutrons at a point when the density became so low that the average time between collisions with protons was now longer than the age of the universe. At this point the fraction of neutrons was "frozen" into the universe. In this way temperature, age and density of the universe are uniquely coupled, so that we get a defined solution for the problem. Finally, deuterium is almost entirely processed to helium. Thus it shows up as the helium abundance.] This result provides another interesting side benefit: The abundance of some minor isotopes, such as deuterium, 3He and Li, depends strongly on the density of the universe. So after all we seem get another handle on this parameter. We seem to be lower by E a factor of 10 than the critical mass density. Problem solved? Universe is open and expands forever? Recent observations of the motion of galaxies in galaxy clusters suggest a much larger mass contents in these entities than is observed in the form of stars. If these new masses are added up there seems to be a discrepancy even with the isotope abundances. There seems to be a missing mass problem!! This mass may not be present as the matter we all know. There may be a different (very strange) kind of matter which we don't even know yet of. Problems of the Standard Big Bang Model However, the missing mass is not the only problem which seems to plague the standard Big Bang model.
- Flatness problem
In the relativistic terms our universe is very close to being flat: one order of magnitude off in density means nothing. In order to get to this condition now (at an age of 10-20 Billion years) it had to start out incredibly accurate (accuracy of 10-15 at an age of 3 minutes). Consider the following: you want to aim the space probe exactly into the asymptotic escape corridor. --------
-Student Reaction: Sure it had to be very accurate in the beginning but the universe has had an infinite amount of time to expand and contract until it hit upon just the right conditions for our current one to occur. --------
- Horizon problem We see exactly the same parameters of the universe in all directions, when observing the background radiation. However, if we compute the distance of the 2 opposite regions of space from each other at an age of 300,000 years (the time when the background radiation started to run), there was no prior communication between these regions at speeds slower than the speed of light! I.e. there was no connection and it becomes strange that everything is so homogeneous. --------
What about nearest neighbor communication with the stars relaying information from one to the other all the way across the universe. Couldn't this be faster than the speed of light.
Reply: No, even this type of communication can't exceed the speed of light.
Second Student Reaction: If space is bent into higher dimensions then areas that in three dimension are very far away might be very close and communication between these parts would only have to occur over these lesser distances resulting in what would look like us in three dimension to faster than speed of light communication.
Reply: Yes, Possible. --------
Finally, there is 1 proton or neutron for every 109 photons in the universe. Originally everything was photons. If they react in a hot environment exactly as many protons as anti-protons would be produced, which finally would cancel each other in collisions. Why is there left over matter after all? A solution proposed in the 70's by Alan Guth and Andre Linde is the idea of an inflationary universe. Encouraged by the discovery of Salam and Weinberg that the electromagnetic and the weak nuclear force (2 of the total of 4 basic forces in the universe) can be combined to the higher symmetry of the electroweak force at higher energies, a combination even with the strong nuclear force into Grand Unified force is envisioned at even higher energies than we can produce in accelerators. However, this was available in the early universe.
The evolution of the early universe is thought of as a series of symmetry breaking into more separate forces, like the isotropic symmetry of the liquid water is broken into the more constrained symmetry of the ice crystals during the phase transition from liquid to solid. During such phase transitions the latent (melting) energy is freed up and becomes useable. The equivalent of this energy was held responsible by Guth and Linde for the additional push in the original expansion, which they phrased as inflation of the universe. Like the surface of the wrinkled balloon is flattened, the geometry of the universe was made flat, i.e. almost exactly on the edge between open and closed. Everything in the universe was in contact with each other before inflation. We now can see only a tiny fraction of the entire universe (what we know as the observable universe). This of course has to have the same parameters everywhere, because it went through the same process. This solves the horizon problem. Finally, the symmetry breaking itself explains why there is an asymmetry between matter and anti-matter.
The beginning: In quantum mechanics there is no absolute zero. Therefore, there cannot be a time zero, size zero nor a completely empty universe. When talking about a size of 10-33 cm and an age of 10-42 sec the seed of the entire universe could have popped up as a simple fluctuation of the "nothing", a quantum mechanical fluctuation which obeys the Heisenberg Uncertainty Relation. With the start of inflation more and more energy/matter is being pulled out of the "nothing". This sounds almost like the story of Baron Mnchhausen, when he pulled himself and his horse out of the swamp.
This is the point where we stand like Goethe's Faust:
"Zwar wei' ich viel, doch mcht' ich alles wissen." "Though I know much, I should like to know it all."
However, let me close this lecture with a few different views on the universe by well-known physicists, which outline the diverse view of the two alternate Anthropic Principles:
Steven Hawking: "We still believe that the universe should be logical and beautiful; we have only dropped the word 'God'"
David Bohm: "I would phrase it in a different way: In the past people had insight into a kind of intelligent being (intelligence), which created (structured) the universe, and they have personalized it and named it 'God'"
Einstein: "God was a mathematician"
Student Reactions to Lecture:
The problems with the Big Bang theory could be rooted in disparities between our two main frameworks for understanding, namely quantum mechanics and general relativity.
It is not that odd that we don't have a grand unified theory yet and we shouldn't think yet that we aren't going to find one because in terms of the scale of the universe we have only been working on the problem for an infinitesimally short time.
The fact that we only have one universe to observe compounds our efforts to verify our theories.
I think there is a link between asking what there was even before my birth and what there was before the big bang. Humans come innate with these questions. Unfortunately, like trying to remember your early childhood, the further we look back into the early universe the fuzzier the picture becomes.
Can Science even address why there is something rather than nothing?
In quantum mechanics, because of the uncertainty principle, you can never have exactly nothing, and this leaves the door open for the possibility of something.
But how could there be fluctuations in time pre universe when there was not even any time to fluctuate in?
We must leave the possibility for things to have unfolded in ways that we don't even believe rational. We have the tendency to get so locked into our framework of thinking that it limits our theories.
At time zero were there even natural laws?
Personal Reaction, Mark Osgood:
The last question was my own, and one I find very interesting. There are two possibilities; One, that the physical laws as they are now are the product of how the universe unfolded. Or two, that the physical laws existed before the universe as framework for it to unfold according to. I have no problem seeing that such things as force laws and physical constants could be properties of our particular universe and had it followed a different path in its development that they could be different. Perhaps they are continuing to change as the universe expands even now but buy amounts so small as to only be noticeable over millions of years. What I do have a problem with is believing that principle such as energy/matter conservation and minimization theory are only products of this particular universe. (Energy and matter conservation states that matter or energy can neither be created or destroyed and so the total amount present in the universe remains constant. Minimization theory such as Hamilton's principle states that nature always acts in such a way as to minimize the quantities involved in a process, i.e., energy, time, distance.) I find it very hard to imagine that a universe could exist without these principles behind it. But, that "behind" leads to a problem. Behind what, or outside of what? Can these principles exist or even be talked about without a universe or framework for them to exist or make sense in. But, on the other hand, could a universe have unfolded without these principles to follow. It is questions like these that stretch the bounds of rational thought. I will lead my discussion topic with these such questions.
References for Eberhard Möbius's Lecture:
Wilford, J.N., New Data: Stars still seem too old, New York Times, Sept 12, 1995.
Eicher, D.J., Candles to the Night , Astronomy, p. 32, Sept. 1994.
Some thoughts on religion by Paul Brockelman to lead us into Fri, Oct. 13's session:
Religion has been distorted in the West, exceeded it bounds and supposes a God. In the East God is not an entity but rather simply the experience of wonder and gratitude at being alive. The creation myths of the West could be thought of as metaphor of this wonder. This type of thinking brings God into the universe and not external to it.
In the 17'th century they plugged in a god to throw the start switch for the universe. God became a super scientist, the answer to the unknown.
Mysticism is talking about things that are also beyond space-time. (Like the questions concerning physical law in pre-universe time)
Science is not omnipotent.
Mark Osgood (9/29/95)