Cosmology 101: The Big Bang Brouhaha


We’re only a few days into the Trump Administration and WC is already tired of the Liar-in-Chief’s antics. Wickersham’s Conscience will take a break from politics and presidential churlishness and revert to the magpie principle. At least until WC’s atrophied moral outrage recovers.

For a sense of perspective, lets talk about cosmology instead. Let’s focus on issues that are 13 billion years old instead of last night’s presidential tweets. As always, WC apologizes in advance to all the Real Physicists out there for the gross simplifications here.

It turns out there’s something called the Cosmic Microwave Background, the CMB. It was accidentally discovered in 1964 by American radio astronomers Arno Penzias and Robert Wilson. The discovery earned Penzias and Wilson the 1978 Nobel Prize in physics. At the risk of horrifying real physicists, think of the CMB this way: when a fireworks explodes, you can see the visible light for a second or two, and then it disappears. But if you were to look at the fireworks explosion by infrared light, you could see the heat signature where the explosion was long, long after the visible light had faded away.

The CMB is the left over light from the Big Bank, the explosion 13.7 billion years ago that created the universe. Over the life of the universe, the unimaginably hot violence of the Big Bang has cooled to about 2.72° Kelvin. The “light” has dimmed to a low frequency radio signal. But the thing is that the strength of the radio signal is very nearly, but not quite, the same no matter where you point a radio antenna. The CMB doesn’t have a point of origin in the modern universe; that point of origin was the whole universe, a much smaller universe than we live in today.

Cosmology is the science of looking at what’s around today and trying to figure out how it all happened. The focus is usually the first half-million years after the Big Bank, and especially the first tiny fractions of a second following the Big Bang.

Technically, astronomy can “see” back that far. Given the universal limitation of the speed of light, anything astronomers look at is in the past. The “seeing” isn’t very good past 10-11 billion years ago, and earlier than 380 thousand years after the Big Bank it was all a hot plasma fog; it took that long for things to cool off enough – for the Universe to grow large enough – for matter to precipitate out of the fog of high energy.

All that is background to what WC calls the Big Bang Brouhaha. The CMB has been mapped in high detail and, as science would predict, it isn’t perfectly uniform.

Nine Year Microwave Sky The detailed, all-sky picture of the infant universe created from nine years of WMAP data. The image reveals 13.77 billion year old temperature fluctuations (shown as color differences) that correspond to the seeds that grew to become the galaxies. The signal from our galaxy was subtracted using the multi-frequency data. This image shows a temperature range of ± 200 microKelvin. Credit: NASA / WMAP Science Team WMAP # 121238 Image Caption 9 year WMAP image of background cosmic radiation (2012)

Nine Year Microwave Sky The detailed, all-sky picture of the infant universe created from nine years of WMAP data. The image reveals 13.77 billion year old temperature fluctuations (shown as color differences) that correspond to the seeds that grew to become the galaxies. The signal from our galaxy was subtracted using the multi-frequency data. This image shows a temperature range of ± 200 microKelvin. Credit: NASA / WMAP Science Team WMAP # 121238 Image Caption 9 year WMAP image of background cosmic radiation (2012)

The “temperature” range in this map is very, very slight: 400 microKelvins Call it a one-third of a degree Farenheit difference between the red and the blue. A small difference, but measurable.

Now talking about the reasons for these variations gets pretty speculative. Deductions about the state of the proto-universe 13.7 billion years ago based on what you are seeing today is a lot like speculating about the structure of the first forms of life on earth, 3.5 billions years ago, based on a modern amoeba. Or speculating about planetary formation by studying a metamorphic rock. There are a lot of computer models, lots of theories and some very esoteric math.

Still, Big Bang theorists agree that the slight but measurable variance in CMB is a result of quantum effects in the very early universe, and that the Big Bang happened about 3.7 billion years ago. After that, cosmologists get testy. There are lots of problems.

First, the Universe is bigger than cosmology would predict. A lot bigger. Cosmologists have proposed a period of “rapid expansion,” referred to as “inflation.” But there is no agreed evidence of the “inflationary energy” to drive that accelerated expansion. If there was a kind of “second explosion” in the universe that caused that rapid inflation, there’s no sign of it today.

Second, that rapid inflation should have created gravity waves. Not the gravitational waves detected in 2015 that result from merging black holes. Those are current events. The cosmic background gravity waves are analogous to the CMB. They are the faint gravity effect echo of the earlier big gravitational splash. Except they aren’t there. Or at least some very sophisticated experiments haven’t been able to detect them yet.

Now it may be that physics were somehow fundamentally different in the unimaginably dense, violent and hot universe in those first microseconds. Cosmologists have a term for those instants, the Planck Density, and estimate it to be 10120 times denser than the modern universe. That’s a ten followed by 120 zeros denser. Maybe in ways physicists don’t yet understand the laws of physics are different in those conditions. Maybe, somewhat like the way Einsteinian physics supplant Newtonian physics, there’s another special set of rules that apply at matter densities of 10120 times denser than the modern universe.

Or maybe we really don’t understand the origins of the universe.

Or maybe we are on the edge of a paradigm shift, the late Thomas Kuhn’s term for a scientific revolution. Black matter, dark energy, accelerated inflation in the early universe; maybe a new, falsifiable theory will be developed, that’s consistent with the observed evidence and makes predictions that can be confirmed experimentally. Because right now, the Big Bang Theory, while accurate and predictive in general, is wrong in too many details.

Why should you care about this? WC will closed with a quote from Richard Feynman: “Physics is like sex: sure, it may give some practical results, but that’s not why we do it.”

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