Overview on Physical Cosmology
Lead: Eberhard Möbius

2/8/2010

Summary by Kalika Bower

Everything Out of Nothing? - Sense of Place and Paradigm Shifts

The overarching theme of the first lecture, presented by Professor Moebius, dealt with fundamental issues we will continue to encounter throughout this exploration. On a general level we were exposed to and discussed subjectivity, relativism and hypotheses regarding the Big Bang, our current existence and how we understand our being here. Professor Moebius suggested at the beginning of his lecture that “the way we look at the world scientifically may not clash with the way we see it religiously”, which importantly emphasizes, I think, a certain amount of faith it takes to explore the world scientifically. As a person who is extremely interested in humanities and the arts, I have a particularly difficult time understanding the world and lived experiences through science, such as physics, though I don’t doubt that physics, or other scientific subjects, necessitates scientists and mathematicians to be imaginative and creative, while also urging them to find intrinsic value in their inquiry. I could be interpreting Moebius incorrectly; on a more basic level, he could have meant that science and religion need not eliminate the presence of the other.

Professor Moebius began the lecture by posing that we, as subjects, are bound to the world and thus the way we perceive the world is bound to us as subjects. He stated that when we perform scientific experiments and make scientific observations in our world, using a rigorous and objective scientific method, we must separate ourselves and our lived experiences from the object of our study, in order to be as objective as possible about the data gathered. A problem Moebius finds within the discipline of cosmology, however, is that we are unable to maintain the same dividing line between subject and object observed when studying the entire universe because we are included in the universe. It seems to me, however, that we are also part of the world, and are entangled in the objects that we observe scientifically and objectively (i.e. extricating ourselves from the study of an object through rigorous scientific method) so why can we make this divide when studying our earth and world but not make this separation when studying the universe? It seems to me both cases do not/should not tolerate the emancipation of the subject. The notion and importance of subjectivity seems to be so embedded in our current culture that it may be taken for granted. Moebius stated that there is no “Cartesian cut”, meaning there is no way to separate ourselves as conscious subjects from the natural world of objective matter we exist in. Although the theme of subjectivity will undoubtedly return for us, Professor Moebius moved on quickly saying “don’t involve yourself as the subject”. So, though we might never be able to evade subjective perspectives we should not immobilize our studies at that point.

After leaving subjectivity behind we were introduced to there being many planets, comets, stars, and galaxies, but only one universe (that we know of). If we think it safe to assume that there is only one universe, we can make hypotheses and produce tests about that object with hopes to clarify our understanding of the universe and our place in it. Professor Moebius then posed the question, “is the universe infinite?” that is “has it lasted for an infinitely long time without changing?” The question concerns not just infinity in time but also in space. This question was the major inquiry of the lesson.

We were introduced to Olbers’ Paradox as a further exploration into this question. Olbers’ Paradox represents the phenomenon that one cannot see the forest for the trees, by example, and which contradicts the notion of a static universe, a universe in which space is neither expanding nor contracting. Olbers’ Paradox contradicts the theory of a static universe that is infinite, because if the universe were infinite in both space and time we would see a glowing sky, rather than a dark sky with glowing stars amongst it. The idea contends that every direction in space would at some point contain a star and that because the speed of light remains the same in a static universe, because the universe is not expanding, we would see constant light. The paradox requires infinite time, because then light that might have to travel huge distances would have plenty of time to reach us.

I am not confident in my recapitulation of this, but what I took to be important is that we can’t work with infinity because infinity is blurry, in the same way the sky would be blurry, or deceitful, if all we saw was constant glowing. I found a correlation between having to move on from our subjectivity and having to move on from the question of infinity; I suppose instead of moving on from these two constituents we are suspending ourselves from them. It was also suggested that even if the universe were infinite spatially, if the universe is finite in relation to time we would not have the ability to explore it’s spatial abyss. The general conclusion from Olbers’ paradox is that the universe cannot be infinite in spatial extent and eternal together. If this was the case, the sky could not be dark at night.

Moving on from Olbers’ Paradox, we were then exposed to information about distances in the universe. Parallax is a method astronomers use to measure the distance between astronomical phenomena. It is a geometric method of gauging distances by recording the disparate angles from two points of view a known distance. Importantly, parallax is not the only method.

Scientists have developed and refined the skills needed to map out the distances amongst planets in relation to the sun causing a paradigm shift in relation to our understanding of our physical placement on the map of the universe. It has been determined that the earth is not in the center of the universe and the earth is revolving around the sun. We are in the center of our observable universe; similarly, we are at the center of our own personal, subject lives, but that does not affirm solipsism. The planet earth is arbitrarily placed with consideration to our observable universe, which we have previously assumed we are limited to.

To exemplify our arbitrary placement in the universe, Professor Moebius brought up Alpha Centauri, the third brightest star to our naked eye, which is approximately twenty thousand times the distance from the sun to Saturn. That is about from here to California, in a model, for which we shrunk the Sun and the planets all by 1:10,000,0000,0000. The diameter of out Milky Way galaxy is about 20,000 times the distance of Alpha. Twenty times that distance is approximately the distance between our galaxy, the Milky Way, and our neighboring galaxy Andromeda (two million light years), and ten times that distance is the diameter of the “Local Group” of galaxies. Moreover, if this distance is multiplied by one thousand five hundred the diameter of the known universe is determined. It is important to note that we are in the center of the observable universe, but that does not imply that our planet or even our solar system is at the actual center of the universe. Being at the center of the observable universe merely means that due to the speed of light, there is finite and definite limitation to our capacity to observe the universe. Hence every observing point of reference is at the center of the observable universe relative to itself.

The lecture continued on with Professor Moebius reporting about Light as a Time Machine: light from the sun is 8 Minutes old, while light from Saturn is 80 minutes old. The light from Alpha Centauri takes approximately 4.3 years to reach our vision on earth. The time at which light travels in a year is labeled one light year. We can infer that the light left the Andromeda Galaxy about 2 million years ago.

The Redshift Effect is the distortion of light across space. It occurs when a source of light is receding relative to the observation point. The analogy of a horn honking was given to elucidate the Doppler Shift (Redshift when the object moves away): the horn sounds deeper when it is moving away from and higher pitched when it moves toward the subject perceiving it.

Edwin Hubble discovered that the farther away a galaxy is, the stronger is the Redshift of its spectral lines. This means that Galaxies move away from us and the universe is expanding, and so it would seem we are in the center. This leads to the cosmological principle, which states that the universe is the same everywhere. But if the universe is the same everywhere then it would be safe to assert that there are then galaxies beyond the farthest galaxies we know of.

The problem of time over space resurfaces. We can’t have empirical experience about galaxies whose light needs more time to reach us than the age of the universe. I was having a difficult time fathoming an infinitely expanding universe, because I was grounded in the need for a space for something to expand into—there needs to be something available to be formed or created. Professor deVries then posed the possibility that if space were creating itself then it wouldn’t need space to move into. Would it be probable to assume, then, that if time creates itself there need not be time beyond this time? Professor Moebius retracted his use of “infinite” and our pursuit into an infinite universe and decided “unbounded” would be a more appropriate adjective.

So, because we have learned that the universe is continuously expanding, there is the logical consequence that the early universe was very compressed. As a consequence it was very hot, and the radiation from this primeval fireball is still around as a cosmic background radiation.

Professor Moebius continued by stating that scientists, astronomers, physicists, etc. can only make models and test their accuracy. Although several of the big bang model predictions were verified, there are problems with it, such as the flatness (fine-tuning) problem, which suggests we are just on the edge of expansion or of collapsing. Another problem, the horizon problem, states that the universe is the same in opposite directions but there is no communication possible between the different objective points because two points in opposite directions at the edge of our observable universe will be too far apart to communicate with each other, because light has a limited speed. Thirdly, there is the matter problem, i.e. why there is just matter and not the same amount of anti-matter. The inflation model and the anthropic principle encompass ideas such as to how the universe started with the correct conditions in order to infinitely expand, and that the universe and planet earth must be significant because if it were any other way we would not exist.