Chapter Content
Okay, so, let's talk about having faith in astronomy. Yeah, it sounds kind of weird, right? "Faith" and "astronomy" in the same sentence. But listen, as R. Buckminster Fuller said, "Everything you’ve learned in school as 'obvious' becomes less and less obvious as you begin to study the universe." And boy, is that the truth!
I remember growing up in East L.A., I mean, the night sky was just, like, a wash of light. You couldn't see anything. The first time I saw a truly dark sky? Man, it blew me away. It was when my high school buddies and I went camping in the Mojave Desert. Wow. Just wow!
The sky was pitch black, seriously, like someone had painted it. And the stars, they were like… flashing gemstones. So close, you felt like you could reach out and grab 'em. And the Milky Way? It looked like this… incandescent river, just flowing across the sky.
And it's more than just pretty, you know? A really clear night sky, it just… it bowls you over. It makes you wonder what else is out there. It stirs something really deep inside. And I think that's why astronomy is, arguably, the most emotional and, dare I say it, spiritual of all the sciences.
Plato, back in the day, he wrote in The Republic that astronomy, it "compels the soul to look upwards and leads us from this world to another." And, you know, he had a point.
It's a crazy ancient science, right? Like, Mesopotamia, 3500 BC, they were already doing astronomy… alongside astrology, its less reputable cousin. Ancient priests, they were the OG astronomers, always watching the heavens for signs, you know, for religious, agricultural, social stuff.
But astronomy is kind of a weird science, too. You could even argue it's not a "true" science at all. Unlike, say, physics or chemistry, or biology, astronomy is trying to understand things that are totally beyond our reach. You can't, like, make stars do your bidding. You can't really do controlled experiments, which is, like, the foundation of most sciences.
Most of the time, all you can do is analyze the light from these super far away objects and try to figure things out. As Sir William Bragg put it, "Light brings us the news of the Universe." It tells us about their existence, positions, movements, everything!
But even then, there's a limit to what you can learn from starlight. Especially when you consider that, like, 95 percent of the universe is invisible! Yeah, that's right. 95 percent! Dark matter, dark energy… stuff that doesn’t emit any detectable light. Invisible.
So, basically, astronomers are operating mostly in the dark. Literally. They have to rely on... faith. Ideally, a smart and enlightened kind of faith, to believe in their ideas about this mostly invisible cosmos.
Richard Massey, this astrophysicist, he said that dark matter isn't supernatural, but it's so mysterious, it kinda makes you think of supernatural stuff. Same with dark energy. We don't even know what it is! It's just our name for something that's making the universe expand faster and faster. Saul Perlmutter, another astrophysicist, he called it even more bizarre than dark matter!
So, what is dark matter? What is dark energy? And that's just the start. There are so many mysteries. I mean, how big is the universe? How old is it? How did it even begin?
And then there's the question of whether or not there's life out there, which falls under planetary astronomy.
The other big questions? Those are cosmology. And cosmology? That's the one I fell in love with in grad school. Cosmologists, we focus on the big picture, the whole universe.
And let me tell you, cosmology really pushes the scientific method, and the human mind, way beyond their limits. It's a realm far beyond controlled experiments, beyond what we can see, beyond logic. Accessible to our… well, our spiritual intelligence, if you will.
For me, it doesn’t get more exciting than that.
This physicist, Gregory Bothun, he said that even though cosmology uses particle theory, relativity, observations, there's still room for mysticism and imagination. The mysteries are so deep that there’s no clear model for the origin and evolution of the universe.
So, let's start with how big is the universe, okay?
Back in the day, cosmologists were arguing about this all the time. Some said it was infinitely big, others said it had limits.
Nowadays, we've got telescopes and methods that are clever enough to get a pretty good idea of its size. One of these methods is called the cosmic distance ladder. It uses some clever tricks to estimate distances, step by step, like going up a ladder.
It's a testament to the ingenuity of cosmologists, making the most of whatever little information we get from starlight.
But here's the thing: Each step on the ladder isn't perfect. Each measurement depends on the accuracy of all the measurements before it. So, if one technique messes up, it messes up everything that comes after it. The ladder is only as strong as its weakest rung.
And just to give you a sense of scale, one light-year is nearly six trillion miles. Trillion!
Based on the best estimates, we think the observable universe is about 92 billion light years across. The actual universe is way bigger than that, but the outer regions are moving away so fast that their light will never reach us. They'll always be hidden, like a cosmic Road Runner that Wile E. Coyote can never catch.
Because we can't see the outer regions, we can't use the ladder to figure out its total size. But we can make an educated guess based on the critical density of the observable universe.
If the universe is overweight, then it's finite. We call this a closed universe. One day, it'll collapse in on itself.
If the universe is at or under its target weight, then it's infinite. We call that flat or open, depending. In those cases, it just keeps expanding and diluting.
The crazy thing is, our universe seems to have precisely the target weight. Not too fat, not too skinny. It's just right.
That means it’s infinitely large and flat. Which means going out into space is like wandering in a wilderness with horizons you'll never reach. Ever.
But there's a twist! Recent data says that the universe is actually overweight, so it might be finite and closed. Which means going into space is like driving in circles. Eventually, you end up back where you started.
Okay, so next big question: How old is the universe?
For centuries, no one asked this. Everyone thought it was ageless and static. What we see now is what always has been and always will be.
This went on until the 20th century! Then, scientists made two huge discoveries.
In 1915, Einstein published his theory of general relativity, thinking it would support the ageless-static theory (AST). But it didn’t! It suggested the universe might be expanding.
He quickly added a fudge factor called lambda to his equation of gravity, to make it fit the AST.
But then, in 1929, Edwin Hubble showed that galaxies are moving away from each other. The farther away, the faster they're moving away.
Again, cosmology was thrown into chaos.
This time, cosmologists couldn't ignore it. The universe seemed to have exploded into being and was still expanding! Just like Einstein’s original equation said.
They ditched the AST and asked themselves: How old is the universe?
They realized that Hubble's constant gave them the answer. A fast expansion means the universe reached its current size quickly, so it's relatively young. A slow expansion means it took a long time to get here, so it's relatively old.
All they had to do was figure out the value of H.
But that was easier said than done.
H depends on estimates of cosmic distances, and those aren't precise. Also, H isn't constant. It changes with time. Which means we need to know what the universe looked like when it was a baby!
How can you get baby pictures of the universe? By looking far enough out into space.
Light from distant objects takes billions of years to reach us, so it shows us the infant cosmos.
In 2013, astronomers used their best data and concluded that H = 70, which means the universe is 13.8 billion years old.
But even now, people are questioning that number.
In 2019, a group published a paper claiming that H = 76, which would mean the universe is a little less than 13 billion years old. More recently, a group said H = 82.4, which means it's only 11.4 billion years old!
The debate isn't going to end anytime soon.
This Nobel Prize winning astronomer, Adam Riess, said that the disagreement suggests we're not understanding something about the cosmological model.
So, next up: How did the universe begin?
In the beginning, there was no beginning. At least, that’s what people thought because of the ageless-static theory. It wasn't until the 1930s that they accepted the idea of an expanding universe.
A few years before that, though, this Belgian cosmologist named Georges Lemaître jumped the gun and got ridiculed for it.
Lemaître was no dummy. He had two PhDs.
In 1927, he published a paper claiming that the universe hatched from a "cosmic egg" or "primeval atom." Sound familiar? This was the beginning of the big bang theory.
He told Einstein about his idea, but Einstein reportedly sneered, "Your calculations are correct, but your grasp of physics is abominable."
Ouch.
Even after Hubble's discovery, people still turned up their noses. Arthur Eddington said the notion of a beginning was repugnant to him.
In 1949, Fred Hoyle argued for the AST and called Lemaître's idea "the hypothesis that all the matter in the universe was created in one big bang."
Ironically, Hoyle's sarcastic term "big bang" stuck. Now it's sacred scientific dogma.
But even though we've come a long way, cosmology still has a long way to go. The standard model has serious problems, and cosmologists are still wondering how the universe began.
Okay, finally: Does extraterrestrial life exist?
So, you look up at the sky and think, "There's gotta be somebody out there!" But if that’s true… where is everyone?
Enrico Fermi famously asked, "Where are they?" Where are all the little green men?
Astronomers estimate there are billions of galaxies and billions of suns in our galaxy alone. So, it seems likely that there's a sun with a planet that has life on it.
But we haven't found one, and no little green person has knocked on our door. Why not? This is called the Fermi Paradox.
Astronomers have been searching for little green men since 1960, when Frank Drake listened for signals from them. He heard nothing.
For the past two decades, planetary astronomers have searched for exoplanets. They've found evidence for thousands of them.
Now, most exoplanets are too far away to see directly. We infer their presence by how they affect their stars.
From these inferences, astronomers estimate the planet's rotation, diameter, and distance from its star. Then, they can tell if it's in the Goldilocks zone, which is where it's "just right" to support life.
Of all the exoplanets, how many could have little green men? Zero.
That's according to NASA. They said they've found Earth-sized rocky exoplanets, some in habitable zones, but they haven't found a planet that can support life like Earth.
Think about that.
As far as we know, our solar system is unique. Earth is unique. You and I are unique—in the whole universe!
So, what are the odds that we'll find little green men one day?
I first got interested in exobiology when I was a grad student. I was taught by Carl Sagan and Frank Drake, the fathers of the search for extraterrestrial intelligence (SETI). In fact, Frank was on my thesis committee.
One of the things I learned is that it's almost impossible to answer whether little green men exist, for at least two reasons.
First, it's not easy to define "life."
Every living thing on Earth is made from carbon, hydrogen, nitrogen, oxygen, phosphorus, and sulfur (CHNOPS). But there are many other elements. Is it possible that life could be made from different elements?
We don't know.
Some people have imagined life-forms made of silicon, boron, or even germanium. Some imagine them based on ammonia, not water. Others speculate about nonbiological life-forms made of metal, plasma, or consciousness.
Because we don't know, the speculations are wild.
Second, we don't even know how life on Earth began. Evolutionary theory only explains what happens after life begins, not how it actually begins.
Evolutionary biologists think it began on its own, which is called abiogenesis. They have two broad ideas, and they both sound like science fiction.
The first idea: It Came from Outer Space.
In this scenario, the ingredients of life rained down on Earth from something like a meteorite, comet, or space alien. Richard Dawkins said that a civilization evolved elsewhere and seeded life onto this planet.
This idea is supported by the fact that comets and meteorites contain organic molecules, even amino acids.
For example, a meteorite that fell in Sudan contained nineteen different amino acids. And a comet contained many organic molecules and glycine, the simplest amino acid.
The second idea: It Came from the Black Lagoon.
In this scenario, the ingredients of life were put together by a chemical process right here on Earth. Darwin liked this idea.
He thought that Earth's first proteins might have been cooked up by accident in a warm little pond with all sorts of stuff.
In 1953, chemists tested Darwin's idea. They zapped a mixture of gases with electrical sparks and produced amino acids.
The results were questioned for technical reasons.
One problem is that Earth's early atmosphere was probably mostly carbon dioxide, nitrogen, and water vapor, not the gases they used. One of the chemists' students later corrected the gas mixture, but the results are still debated.
Another problem is that amino acids come in two forms: right-handed and left-handed. Life on Earth uses only left-handed ones. So, if an experiment wants to show it simulated the process that made life on Earth, it has to produce only left-handed amino acids.
The experiment didn't do this. It produced both kinds equally, so it didn't simulate the process that made life on Earth.
Scientists recently made a more advanced version of the experiment, which they call a planet simulator. They can change the conditions inside to simulate early Earth or other planets. But it remains to be seen whether it will produce any good information about the Black Lagoon scenario.
Even if we do find the right amino acids, we'll still be a long way from finding or creating life.
Yes, amino acids are the "building blocks" of life. But it takes a lot of them hooking up just right. And they have to fold themselves into the right shape to create a healthy protein.
It's like origami. Just one wrong fold, and it won't work.
For example, a hemoglobin protein is made of 574 amino acids that have to be put together in the right way. One mistake, and you get a bad protein, like in people with sickle-cell anemia.
A living thing relies on hundreds of these proteins to work right. Even Mycoplasma genitalium, a tiny pathogen, relies on hundreds of different proteins. You and I need thousands or billions of them!
But even then, proteins aren't life-forms. They can't replicate themselves.
For that, you need something like RNA, which needs nucleotides, which are even more complex than proteins. And we haven't found nucleotides in space, or made them in the lab in a way that simulates early Earth.
Even if we did find or make nucleotides, we'd still be a long way from finding or creating life. We also need information.
We need a recipe and a chef to mix the ingredients. Without information, it's not likely that Earth's 4.5 billion years would be enough time for CHNOPS to make themselves into amino acids, proteins, and nucleotides, and then for those to accidentally bake themselves into you and me.
This atheist astronomer, Fred Hoyle, said that the chance of life forming through random shuffling is so small that it's basically zero. He said that life needed explicit instructions to be assembled.
Another scientist, Ilya Prigogine, agreed that the idea of life spontaneously forming is highly improbable, even over billions of years.
So, what are the odds that little green men exist?
Well, there’s the Drake Equation. It gives a rough estimate of how many intelligent civilizations are likely to exist in the Milky Way.
It takes into account factors like:
How frequently suns are born that could sustain life?
What fraction of those stars have planets?
How many of those planets have environments suitable for life?
What fraction of those planets actually host life?
What fraction of those life-bearing planets have intelligent life?
What fraction of those civilizations broadcast signals into space?
How long do those civilizations broadcast signals into space?
Drake and his colleagues figured that our galaxy alone should have a ton of intelligent civilizations.
That means a crazy number of intelligent civilizations should exist in the whole universe. A veritable explosion of advanced little green men.
And yet, even with all the excitement about life on Mars and exoplanets, we're still living with Fermi's Paradox. When we look into space with our best instruments, we find no hard evidence for little green men and hear only crickets.
Why?
According to a team at Oxford, it's because we've been too optimistic about the Drake Equation. We want there to be little green men so badly that we've overestimated the number of civilizations that might exist.
When the Oxford folks used realistic values, the Drake Equation predicts far fewer civilizations. The number is so low it’s practically zero.
They concluded that there's a good chance that we're alone in our galaxy, and maybe even in our observable universe. If any little green men do exist, they're probably too far away to ever reach.
Interestingly enough, the Bible agrees. Sentient beings do exist beyond our horizon.
One of them even came to Earth a while back, and that visit is documented in the most widely read book in history, and that book answers the question: “Are we alone?” and it gives us a definitive answer: No, we are not.