Saturday, May 14, 2016

From Big Bang to Dark Energy

I finished a MOOC for the first time. I've started several but this was the first one I finished. It was a four weeker with Hatoshi Murayama through the University of Tokyo, called "From the Big Bang to Dark Energy." He is a phenomenal teacher.

1. There has been massive movement in the field of cosmology in the last twenty years. We've seen the rise of the concepts of "dark matter" and "dark energy." Something that correlates well with the Higgs boson has been discovered. Gravitational waves have been detected. There seem to be a number of projects in motion. Much seems in flux in the field.

[Now for the Christian disclaimer. Even physicists are in flux here--the room is hardly painted, let alone dry. Meanwhile, I have never seen anything contradictory between the idea that the universe began with a bang and the belief in creation. Indeed, there is much in the current scenario that would do well with a Designer. The theological issue with evolution primarily has to do with Adam, not the age of the universe. In short, I neither consider this course correct, nor do I find anything in it that contradicts the Bible or orthodox faith.]

2. The image above a standard picture of the big bang hypothesis. We can see everything since the "afterglow" of cosmic radiation release by pointing our telescopes out into the galaxy. The most natural explanation for what we see in the sky is the following:
  • Given the speed of light and various mathematical and scientific tricks, the most natural explanation is that, when we look up at the stars, we are looking into the distant past. If Andromeda is 2.5 million light years away (the next closest galaxy), then the universe must be at least 2.5 million years old in order for the light to reach us. 
  • Sure, God could have created the light in mid-stream. Sure, the stars could be an angel kindergarten project painted onto a wall just outside our solar system (with Voyager 1 soon to smash into the wall). But since there's no need for us to worry about taking the universe as it seems to be, we probably shouldn't worry about it.
  • In 1964, a couple of radio astronomers accidentally discovered cosmic background radiation (CMB). It is everywhere you point a radioscope into the universe. It is the "Afterglow Light Pattern" in the image above. Cosmologists currently date it to 380,000 years after the Big Bang.
  • Again, as a Christian I have found this gold and am puzzled by those who think the Big Bang is hostile to the Bible or Christian faith. CMB suggests that the universe had a beginning, which plays directly into the cosmological argument for the existence of God. If the universe began, we can plausibly ask, what caused it?
Fluctuations in CMB (blue wrinkles in the second image) have been part of the puzzle that cosmologists are trying to solve as they try to theorize back behind the 380,000 year mark.

2. CMB is said to reflect a point when the universe had cooled enough for electrons and protons to combine ("recombination") to form neutral hydrogen atoms. Before that point, photons of light were absorbed by a kind of hydrogen plasma with a temperature exceeding about 3000 degrees Kelvin. But when the universe had cooled down enough, these photons were "decoupled" and burst free all over the universe.

Since then, allegedly some 13.8 billion years ago, the photons have been spreading everywhere, but steadily diminishing in frequency because of the red shift of the Doppler effect. They are thus currently in the microwave range.

The fact that this radiation points to about the same temperature everywhere in the universe at about the same point in the past suggests that the vast expanse of the universe we now see, some 13.8 billion light years across, was originally all together. Einstein's relativity suggests that space would contract to a point in relation to an infinitely massive object.

Meanwhile, the fact that everything in the universe is red-shifted suggests that everything in the universe is moving away from everything else in the universe. Sure, there could be some other explanation. But right now, given the evidence, the most plausible suggestion is that the universe exploded from a point and space itself has been expanding ever since.

[Again, there were plenty of scientists in the 1950s that hated this big bang idea because it fit with the idea that the universe had a beginning, which is amenable to a God interpretation. The steady state theory was what was popular (constant generation of matter). And the Roman Catholic priest Georges L'Maitre who suggested a big bang was scorned by morons like Fred Hoyle.]

3. We then enter a dark period. Hydrogen clouds wander as space itself continues to expand. Over the next half billion years, gravity clumps them to form stars. Once stars begin to form, we can see again as we look out into space at the distant past.

In the dense centers of stars, hydrogen fuses into helium and some lithium. For the next 8 billion years or so, stars burn, burn out and explode, then collapse to form second and then third generation stars. Galaxies are formed around black holes, which are the remnants of particularly dense stars after they burn out. Galaxies cluster.

With each each generation of star, heavier and heavier elements are formed by fusion. About 4.5 billion years ago, our own sun--perhaps a third generation star--reformed with eight larger rocks and countless smaller ones in tow. Its third rock was in just the right place for life as we know it.

4. The most recent measurements suggest that the universe is not only expanding, but that its rate of expansion is increasing. If so, it is unlikely that the universe will ever collapse back into a ball (a "big crunch"), such as those who suggested an "oscillating big bang" used to suggest. [a theory that also potentially by-passed a creator, since then the universe might simply be an unending cycle of explosions]

The current thought is that instead the universe is heading for a "big rip," where its rate of expansion will eventually rip every atom of the universe apart. To try to explain why the universe is expanding, cosmologists have suggested an unknown energy, which is currently being called "dark energy" because no one has actually detected it. But it is thought to constitute about 73% of all the mass and energy of the universe, in order to make the math work. We'll see.
4. Theories that push back before CMB do so in part on the basis of our understanding of how nuclear particles work. Nuclear particle accelerators crash particles into each other in search of these sorts of relationships.

So from about 3 minutes after creation to the suggested creation of neutral atoms about 380,000 years later, you have hydrogen and helium nuclei in a soup of plasma. All light is absorbed. Some call this the "photon epoch."

5. At some point, I may review Stephen Weinberg's classic work, The First Three Minutes (2nd ed). The problem is that I'm sure it is hugely out of date. It was first written in 1979 and updated in 1993.

The epoch from about 10-10 seconds to three minutes after creation is a period sometimes called the "lepton epoch." During this period, with a temperature of about 1015 to 1012 degrees Kelvin, protons and neutrons are formed out of quarks. In Murayama's approach, dark matter is formed.

Dark matter is thought to make up about 25% of the universe. It is called dark matter because it is unknown matter that has not been observed but seems necessary to explain what we see. For example, the stars at the edge of galaxies swirl at the same speed as stars near the centers. If galaxies exist in the middle of spheres of some unknown matter, that would explain this motion. It might also explain why there is an unevenness to the distribution of stars and galaxies throughout the universe.

6. The period from about 10-34 to 10-10 is sometimes called the "quark epoch." At the end of this era,
the recently "discovered" Higgs boson gets frozen into the universe at about a trillionth of a second, and the electromagnetic force is now distinguished from the weak nuclear force. Supersymmetry is broken and now time has an arrow. Entropy now points irrevocably toward the future.

Somewhere in here, Murayama thinks there was a grand annihilation of matter and antimatter, but perhaps because neutrinos can switch back and forth between neutrino and anti-neutrino, we ended up with a 2 in a billion excess of matter over antimatter. Thus, after most of these particles had become photons, enough matter remained to form the stars that now remain.

7. The period from about 10-43 to 10-34 is sometimes called the "grand unification epoch." During this period, the universe undergoes an inflation that increases its size by 1026 times in less than a trillionth of a second. At the end of this brief period, the electroweak and strong nuclear forces differentiate.

A by-product of this inflation is thought to be gravitational ripples. They have been claimed to be detected in the last year or so.

8. Before 10-43 seconds, we have a breakdown of our understanding of space time.

9. "In the beginning, God created the heavens and the earth."

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