Cosmology and our View of the World
Overview on Physical Cosmology
Lead: Eberhard Möbius
Summary by Ann Steeves
Everything out of Nothing? - Sense of Place and Paradigm Shifts
Professor Möbius led our second lecture in INCO 796. He started by reviewing that the Universe is one of the three unicates (other two are life and mind). Professor Möbius explained that we as humans have two sides—one that uses the mind and physics to figure out the universe, and one is some sort of spirituality, all people love stories. Professor Möbius found himself at 12 years old wondering if the universe is infinite or finite. Pondering this question is like MC Escher’s artwork of a gallery that is never-ending and loops back on itself—like the universe, “we are in it and it is weird!”
Cosmology is the science of the universe, and may lead us to ask the question, “is the universe the only unicate that stays forever?” We know that there are three unicates: the universe, the mind, and life. There are many planets, comets, stars, galaxies, but there is only one single universe that we know of and only one “life as we know it”. Through genetics and evolution, we have discovered that all life originated from one form. Yet only “intelligent beings” are able to communicate and recognize consciousness. We set limits with our known intelligence and we are always developing and expanding our knowledge base. Professor Möbius gave the example that until about 15 years ago, our planets within the solar system’s Ecliptic was all that was known, and all models of planets were based off of this design. About 15 years ago, we had to change our model as we began to discover extrasolar planets. We began to be able to detect planets around other stars, which brought new knowledge of planetary systems, which we were unaware of previously. This forced us to change our models. This may happen as we discover new information about other unicates. As we continue exploring our universe, we may find other life forms, which will prove life to not be a unicate. The same may happen with minds. These are both real possibilities, but can we say that the universe will forever be a unicate? How will we be able to discover another universe? It is hard to fathom—so we may say that yes, the universe may be the only unicate that stays forever.
We then talked about Olbers’ Paradox and the observable universe. Olbers thought that the universe must be finite in size to account for darkness in the night’s sky. Professor Möbius explained the paradox with an analogy of trees within a dense forest— you keep going further into the forest to find more trees, but there will still be space between the trees, because the forest is finite. You will eventually reach the edge of the forest in this analogy. Like this example, you will eventually reach the edge of the universe, which we understand today to be the “observable universe”. However, Olbers’ Paradox exists if the universe is infinitely large and eternal (unchanging). In this case, the sky would not appear dark, but would shine bright. In this infinite model, a star would be everywhere you looked. Sure, many stars would be very far away, but all spaces in the sky would be illuminated by a distant star’s light. Since our sky has darkness, we can say that the universe is finite.
Someone commented that it might be dark at night to the human eye due to limited perceived wavelength. The human eye observes limited spectrum light. This argument does help only in connection with an expanding universe and of the wavelength to infinitely long waves. Someone also brought up the point that some objects in the universe take in light. Things that absorb starlight in the bright sky scenario would become as hot as stars and thus shine, as well. So this argument is not useful. We were reminded that distances in the universe are of astronomical sizes—it is very lonely in space with huge distances of nothing.
We must remember that we are not in the center of the universe, our solar system, or our galaxy. We are in the center of our observable universe, and anywhere throughout space an observer would be at the center of their observable universe. We cannot assume that all there is in the universe is within our observable universe. The concept of a possible paradigm shift was proposed: is this the only universe?
We discussed the fact that the universe is expanding and the classic raisin bread model was presented—in baking raisin bread, raisins move further and further away from each other as the bread cooks. This is not because the raisins are moving themselves, but the bread is expanding altogether, causing the raisins in the bread to subsequently spread out. We then reviewed the cosmological principle that the universe is the same everywhere—another paradigm shift that we are not special!! Galaxies move away from us as the universe expands. The farthest galaxies approach the speed of light, which makes us wonder if there are galaxies beyond them! The answer is that there must be, due to the cosmological principle! Light can never go slower or faster than the speed of light. If galaxies in the universe are expanding faster than the speed of light, they are not in our or each other’s view. Someone mentioned a similar example that if a fighter jet were flying away from us at supersonic speed, we would never hear the sonic boom.
Back to universe expansion and the speed of light, we acknowledged the fact that we can’t see galaxies whose light needs longer to reach us than the age of the universe. We are able to see only a section of the universe, but we do not know how small that fraction is. The idea was mentioned that if the universe keeps expanding and accelerating, then the distant future (billions of years) will be a time when everything in the universe is out of sight. We were reminded that our galaxy would stay the same size (like the raisins in the expanding cake). The concept of a 4th dimension was mentioned, where the universe would be unbounded but still finite.
The universe expands continuously, meaning that the early universe must have been very compressed. It was 3000K at an age of 300,000 years with the radiation like a red star. The universe has expanded 1000x since then, but what has happened to the radiation? The initial explosion generated a lot of heat as well as a lot of energy. We discussed the cosmic microwave background spectrum, which has been observed by satellites such as the Cosmic Background Explorer satellite (COBE). The “afterglow” or cooling of the universe’s initial Big Bang can still be observed in today’s universe. Three scientists predicted the expansion rate of the universe, which has proved to be a very good model. Hubble observed expansion throughout the universe, which lent itself well to the Big Bang model. Two other factoids were proved correct from this model:
If we map the universe, the galaxies are distributed in space like on the surface of soap bubbles. Despite the great success of the Big Bang model to explain a number of observations, there are still open questions to unexplained “problems”. There comes the flatness or “fine tuning problem”, which is that we are just now on edge to expand forever or collapse. But we are here now! There is also a “horizon problem” that the universe is the same in opposite directions but no communication is possible! There is also a “matter problem” that 2 lbs of “light” = 1 lb matter + 1 lb anti-matter. So why is mostly matter left? There is no contradiction to the Big Bang, but the model does not offer an explanation to answer these problems.
The classic ratio MC^2 shows that energy has mass. Can we predict the fate and structure of the universe? The accelerating and expanding universe is 13.7 Billion years old. We know that 3% is ordinary matter, but 27% is dark matter and 70% is dark energy. Yes, this means that we DO NOT KNOW 97% OF THINGS MAKING UP THE UNIVERSE!! We know that dark energy is expanding and accelerating the universe against the force of gravity, but we do not know much more about dark energy.
We had a quick discussion of mind and matter being two separate things but looping back onto each other—such as two sides of a paper in a twisted spiral. There are two sides of the paper, but they are twisted, so you keep going around and onto the other side. Mind and matter in the same loop? Throughout our whole discussion, we must remind ourselves that we can only create models or theories! What about reality? Models and theories help us understand what we know about reality, but new discoveries have the power to change such models at any time! Our knowledge is constantly changing and being improved—we still have a long way to go (infinitely long?)…