Physical Cosmology, Part I,
Lead: Eberhard Möbius
Summary by Kelly Cornish:
The second session of class was designed to give students an overview of physical cosmology. At the end of the session we would have a sense for the distances and size of the universe and with further thought, where "we" are in respect to what we've discovered around us. What is described to us in class is what we see, what is observable in the universe to modern science.
What we take as our model of the universe is described as what we all know as the Big Bang Theory. Prof. Moebius points out that it is not out of the question that we may be at the verge of a paradigm shift especially now that we are in another millennium. We looked at slides from various different mythologies and cultures to explore the differences in which science affects beliefs in religions. If we look into this closely, is there really this antagonism or will we see the universe as we know it? For example northeast India mythology tells us that everything sprung up into the universe and if there is unity one will eventually go into duality. One word does not mean anything without its opposite and we have this comparison only in the world of minds. Mythology from Guinea, labeled on the slide as Death the Creator, has a cyclical way to look at the world. There are many chasms between the religions and when we look at science we learn something completely different. To most people mythology is not the real sense of things and we need to look really at the factual world. The dominating belief today is that science will give us a picture of a world we can work with. This is a discussion we will explore after first getting a feeling of the space around us.
To help the students get a sense of size and space in the universe Prof. Moebius used a model to help us visualize the solar system. Due to my lack of memory I'll have to use another similar model you can find at, http://www.seds.org/billa/tnp/overview.html. Which offers us, "One way to help visualize the relative sizes in the solar system is to imagine a model in which it is reduced in size by a factor of a billion. Then the earth is about 1.3cm in diameter (the size of a grape). The moon orbits about a foot away. The sun is 1.5 meters in diameter (about the size of a man) and 150 meters (about a city block) from the earth. Jupiter is 15 cm in diameter (the size of a large grapefruit) and 5 blocks away from the sun. Saturn (the size of an orange) is 10 blocks away, Uranus and Neptune (lemons) are 20 and 30 blocks away. A human on this scale is the size of an atom, the nearest star would be over 40000 km away." There are points of the universe that light can not reach us yet, and it is these places that are unknown. Light can be looked at as a time machine when we map out that the light from the sun is 8 minutes old and from Saturn it is 80 minutes old! Light from Centauri was emitted at the turn of the decade! We are dealing with out-dated information as far back as when our grand ancestors started to walk upright!
The class had quite a discussion about light. Someone asked, "Does light travel in a straight line?" In principle light always wants to go where it takes the shortest time. Light will take the curve that will take the shortest time if it is met by matter for example. Light will also slow down when it travels through matter. Someone asked if gravity affected light. Einstein predicted its influence that light will be deflected like a spaceship does when passing within the earth's gravity field. In relativity, of light all one can understand is the speed of light to explain our place on Earth, in which we can see 15 billion light years and not beyond. Someone was wondering what happens to mass when it disappears. Mass is energy and energy can not be destroyed, only transformed. This must bring us to wonder about what happens to our mass when we die and who are we when we are alive. It seems to me in this theory that we are certainly a part of all this energy. An extremely small part in relation to what we are talking about in terms of the solar system.
We are questioning whether the universe is infinite. How can we know this? Olbers' Paradox was, "You can't see the forest for the trees." Prof. Moebius put a drawing with trees on the overhead to explains this theory. As he put layers and layers of trees over the next, one can see how eventually all will go black. If we were to do that with the stars, everything would be light. Something is wrong with the assumption that the universe is infinite in size. Now we know that the universe has a beginning and thus some light has not yet reached us, which explains the dark spaces in the sky.
A student was wondering about where time loses meaning when measured only in comparison. But scientifically it doesn't make sense to ask what happened before the big bang. There was nothing, not even time. The bounding to the unknown as we can see is always expanding with increasing questions. There is so much unknown and we will certainly be dealing with infinities where the questions remain. It is a "never ending story." Prof. Brockelman points out, "how do we know we will never know it all?" There are many theories with loads of knowledge but foundations that science can not explain. This is the type of logic these arguments are based on and the arguments we will be discussing in future sessions!
February 5, 2000