Cosmology and our View of the World
Overview on Physical Cosmology
Lead: Eberhard Möbius
Summary by William Altenburg
Everything out of Nothing?
M. Gleiser “Tear at the Edge of Creation” Parts of Sections
11 - 25.
P. Davies, The Goldilocks Enigma Ch 1, 2;
"Curtains of the Universe", Astronomy, March 95; Lecture Notes (www); (On Blackboard)
He began with the idea of “Everything out of Nothing”. “We have not come to the answer to the question of where did everything come from”.
The class will focus on “Paradigm shifts” in perspective as we
get a new sense of place, or where and who we are in the universe.
He described his boyhood interest in science and how he maintains that sense of curiosity. For example, there is the question whether the universe is something that started and runs on its own or whether it needs maintenance? “Our perspective of the universe is shaped by the fact that we are inside it and at the same time part of it."?
. This view point gives us a “Weird” perspective. He showed slides with one Escher drawing to illustrate changing perspectives, because changing your point of view changes what you see. Möbius’s view includes us in the picture bringing us into the universe, ...” as a genuine part of the whole that we strive to understand."
. He presented this as a problem, “How can we be both in the universe
and think about it?”
Thus begins cosmology and makes it tough.
We have many examples of things in our universe, but only one universe. We need to study it scientifically running several different and independent tests. The universe ‘s nature should be constant and governed by laws.
As an example he asked about the problem of why the sky is not white since there are stars everywhere?
He cited “Olbers’ Paradox” as the problem of “You can’t see the forest for the trees.” Using a slide of trees scattered on a white background, he posed the question: Would the stars make the sky all white if we could resolve all the light coming to earth from all the stars? He asked the class to vote for A “the stars will make the whole sky shine” or B “the sky will be dark and only a few stars and galaxies”? The correct answer, he said, is Olbers’ Paradox that the stars would outshine the night and create a uniform sky that would let all the stars prevent us from seeing the Universe. It is the distances that make the stars vanish to our eyes.
“Honey, I shrunk the universe.” Prof Möbius brought out a small foam ball representing the Sun and used this to start explaining the size of the planets, the Sun, the solar system, and the distance to the nearest star, Alpha Centuri)(≈4.3) ly, the size of the Milky Way (x 20,000 the distance of Alpha Cen), the nearest galaxy, Andromeda (x10), the size of a galaxy cluster (x20), and the distance to the edge of the observable universe (x1500). To demonstrate the scale, Möbius introduced a 14 cm diameter ball for the Sun. At this scale Alpha Centuri would be in San Francisco and the planets scattered around the campus.
This brings Prof. Möbius to the core idea of our perspective on the universe. Using circles, he showed we are the center of the observable universe, but in the real universe we are not the center because we do not know its boundaries. We are not even centered in our own galaxy and our own galaxy is only somewhere in the universe.
This led to the idea of how we see the universe: the problem of the expansion of space between galaxies as shown by the red shift found by Edwin Hubble. Möbius explained three-dimensional expansion with an example from his Xmas bread with raisins rising in the dough. Hubble found the light shifted for elements (H and K line of Calcium) to the red, indicating the galaxies were expanding; they are receding from us at increasing speed with increasing distance.
This recession speed approaches the speed of light at the edge of the observable universe. This means we cannot see past the galaxies traveling at the speed of light, since the light will never get here. That last observable galaxy is the oldest thing we can see, as all others, if they exist, are past where their light can ever reach us. Their light would be older than the universe, if it could reach Earth. Thus we have a dark sky with a finite number objects, not Olbers’ possible sky of white.
This leads to the idea that the universe has expanded continuously from a highly compressed beginning. We have no special place in the universe and thus we have no special time in its history.
The compression leads to the theory of the Big Bang. Growing observational data is supporting the Big Bang. Möbius says the key is the detection of the background microwaves from the time some 380,000 years after the big bang when the temperature had dropped to 3000 K. This radio signal is uniform and is called the CMB or Cosmic Microwave Background radiation. This is the radiation from the Big Bang with its uniformity showing its universality.
Three key observations support the Big Bang Model
There are problems to be addressed.
The theory leads to three more problems: the inflation hypothesis solved them:
We expect the Mass of the Universe and therefore Gravity to slow the universe’s expansion, but we observe that the farthest galaxies are not slowing, but in fact accelerating. This requires a new kind of (non observable by current means) mass and energy to explain the missing forces needed to maintain the observed acceleration. This also, in a follow up question, can be seen in the problem of insufficient mass in observed galaxies to prevent the outer stars from being hurled away by centrifugal force.
The missing forces require that there be, in addition to the 3% of observed matter, 27 % dark matter and 70% dark energy, sufficient to make up the missing mass and force needed to explain the observed effects. Thus our explanations make our universe more complex the more sophisticated our observations become. But all this leads to an inflationary universe with a flat shape.
Möbius then explained the Anthropic Principle which holds that the universe
has the appropriate conditions so that life and we could evolve. By the “The
Goldilocks Principle”, the Earth is just right and so is the universe.
The strong form of the principle claims that the Universe is set up for life.
The weak form claims that our universe is one of many possible universes throughout
a larger multi-verse.
Möbius offered that the Anthropic Principle does not explain anything. It describes key conditions that must be met by our universe so that life and we could be possible. The principle does not say how the universe nor life came to be. He showed a slide to close. A cartoon by Sir John Archibald Wheeler of life contemplating the big bang as a means of showing we now are observing and commenting ourselves and our origin in the universe with its own beginning.
Many questions were asked to obtain clarification of the above points during the presentation. Most questions after the presentation sought explanation of the time of events after the big bang, especially the cooling process leading to planetary evolution. Möbius described the origin of atomic particles and of the heavy elements. The issue of the Dark Matter arose, and Möbius explained the discovery that the rotation of the arms of galaxies was faster than predicted, and Dark Matter was postulated to increase the rotational mass. Since it cannot be seen, it is called dark, and since it must have mass, it is called matter. Normal matter is only 3% of the universe, Dark Matter makes up 24% of the universe. The remaining 73% of the universe is Dark energy. Chris asked if that meant that Dark Matter and Energy is all around us in our galaxy? She was asking if 3% of the solar system mass is visible then the invisible 97% of the solar systems’ mass is all around us, which ended the class.