Friday, July 24, 2015
Friday Science: Where are we in time?
As I look to a possible rhythm of posting for this fall, I'm thinking of looking at Fridays as a science/math type day. So today I thought I'd review the second chapter of Max Tegmark's, Our Mathematical Universe. Some thoughts on the first two chapters are here.
1. So if the previous chapter tried to locate us in space, the third chapter tries to locate us in time. I don't think there were many controversial matters in the previous chapter. But when you begin talking about the age of the universe, some do get nervous.
So before I dive in the chapter, it's worthwhile to do a little Christian processing first. My sense is that the real rub here has to do more with the question of evolution than it does the actual age of the earth. So even John Piper himself does not think the question of the earth's age is restricted by the Bible.
Here the "apparent age" theory, I think, opens the door to let science be science. It would be problematic to my faith if we had to "cook the books" when it came to science because of a supposed interpretation of the Bible, especially when 1) there are so many contradictory interpretations of the Bible and 2) as a Bible scholar, I know that those who care the most about these sorts of things are usually the most ill-equipped interpreters of all.
The apparent age theory is the idea that God created the universe to look like it was really old, even though it is actually very young. I am not endorsing this theory. I am simply saying that, if we allow for the possibility that God made the universe to look old--whether it is or isn't. Then we are free to let the chips lie where they fall as we look at the evidence. Faith isn't at stake so we can be honest with the evidence.
"Whew," so we don't have to be worried about how old the evidence seems to suggest the universe is.
2. It was an interesting thought Tegmark suggests at the beginning of the chapter that, for the Romans, the laws governing the skies appeared to be different than the laws governing the earth. For example, why doesn't the moon fall out of the sky to the ground the way things I throw up do? I didn't see a footnote here, so I'd like to hear it from the ancient horse's mouth.
But it does make a little sense. Many Jews at the time of Christ thought of the stars as angelic beings. (Which makes the star over Bethlehem potentially get very interesting) Some Greeks and Romans thought of stars as great heroes from the past. These ideas would at least fit with what Tegmark says because, in such cases, the things in the sky would be beings, not rocks. (although Anaxagoras did think the sun was a very hot rock centuries before Christ... he was kicked out of Athens)
By contrast, Newton assumed that the objects in the sky followed the same rules as things on earth. He calculated how fast something orbiting the earth would have to be moving to stay in orbit. His answer was 7.9 kilometers per second. Friction of tides and such is slowing the spinning of the earth, so things were spinning faster in the past than at present.
Apparently, if you extrapolate back, the earth can't be more than 4 or 5 billions years old, because it would have been spinning too fast then to stay together.
3. I suspect the current theory for how the solar system, the galaxies, and the universe formed fits with a host of data. It is not proven, mind you. It is just impressive in its ability to explain a great deal of evidence. If you have a cloud of hydrogen gas--the simplest of all elements, one proton and one electron--two forces will tug at each other.
The one is the force of gravity. It pulls the gas in on itself. The other is the heat of hydrogen running into itself. This heat pushes expansion.
So what happens in mathematical models of this sort of thing is that you eventually get a swirling pizza with a star at the center. The hydrogen in the middle gets so hot that it fuses to form helium, the second simplest element (two protons, two electrons, and two neutrons). The energy levels are also just right for these to fuse to form carbon and from there all the other elements as this plasma mix cools off.
It is a theory, of course. But it seems to make sense, and I can't think of anything in the Bible that would make it problematic.
4. So how old is the earth? Here we get to radioactive decay. The atomic bombs we dropped on Hiroshima and Nagasaki seemed to suggest that our notions of radioactive decay work pretty well with the evidence. What happens is that certain versions of uranium (we call them isotopes) are unstable and tend to disintegrate into lead. This is a process whose rate we have measured.
The "half life" of a radioactive element is how long it takes for half of that element to deteriorate into a simpler element, lower on the periodic table. So at present, it sure seems like we can date things by seeing, for example, how much lead and how much uranium are in a given rock sample. They have done such with certain rocks in Australia, as well as with meteorites and the result is the suggestion that the earth is about 4.4 billion years old, while the solar system is about 4.5 billion years old.
Now these conclusions are based on theories, but they seem to have consistently great explanatory power. Again, for those who think the Bible absolutely teaches a young earth, there is a release valve. If we allow for the possibility that God created rocks with some of the uranium already decomposed, we don't have to worry about this issue. We can take the science at its face value and say that the earth and solar system at least look to be billions of years old.
5. The universe is expanding. This was a hard won conclusion of twentieth century science. There were several people early on who suggested that this was a natural conclusion of Einstein's general relativity. But they were not popular voices. It is a great example of how peer pressure and popularity contests take place in science too.
So a guy named Fred Hoyle had a winning personality and he was saying what people wanted to hear--that the universe wasn't expanding but was pretty much just going along as usual. Meanwhile, Georges Lemaître, a Catholic priest, was ignored when he suggested that the universe was expanding.
And here let me pause to express my confusion as to why some Christians think the idea of a "big bang" at the beginning is problematic. What is a big bang but the indication that the universe had a beginning? It seems to fit very nicely with the cosmological argument for God's existence, that the bang needed someone to trigger it. All I can think of is that people associate a big bang with evolution or assume it means there is no one doing the banging.
On the contrary, you might paraphrase Genesis 1:1 to say, "In the beginning, God caused a big bang, and the heavens and earth were the result." Could it be that the reason so many rejected the expanding universe of Lemaître and Friedmann is precisely because of how well it fit with the idea of a creation?
But the discovery of the "blue shift" of all galaxies we can see (they are all "moving away" from us, like the Doppler effect when an ambulance passes you and the sound gets stretched out) suggests the universe is expanding. When you do the math, it suggests that the universe is about 14 billion years old.
6. So here's a question. If we can see stars that are more than 14 billion light years away (a light year is the distance light travels in a year, going 186,000 meters per second), then doesn't the universe have to be older than that for us to see them?
Here is a key insight from Einstein's general relativity. It's not really that the stars are moving away from us. It's that space--the emptiness itself--is expanding. The space between things is getting bigger everywhere. Fascinating!
Nothing can move faster than the speed of light through space. "But space itself is free to stretch however fast it wants to" (48).
7. Looking into space is like looking back in time. And our telescopes get better and better. Thank the Lord that NASA somehow got money out of Congress to send up telescopes and probes into space.
So the further you look out into space, the older the things you are seeing. We can now see galaxies forming, and what we see looks just like the theory of coagulating gases I mentioned above. The further out you go, you get to the plasma pool of hydrogen atoms. And finally you get background radiation, the afterglow of the beginning. You hear the echo of God's word, "Let there be light."
I'll leave the chapter at that. Tegmark does not believe it all goes back to a singularity, an infinite point. We'll see what he is thinking here in later chapters, I'm sure. But he thinks that the quantum mechanics breaks down about a second before "nucleosynthesis," the formation of nucleuses.
We'll see what that means. By "big bang," he means that "everything we can observe was once hotter than the core of the Sun, expanding so fast that it doubled its size in under a second" (65). Not my definition, but we'll see where he goes with it.