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The Fermi paradox starts with discussions at the manhattan project. One day when extra-terrestrials came up, Fermi asked, “Where are they?”
Or, expanded, “The apparent size and age of the universe suggest that many technologically advanced extraterrestrial civilizations ought to exist. However, this hypothesis seems inconsistent with the lack of observational evidence to support it.” (The wiki on this looks like it might be interesting, so I’m dropping myself a note.)
How common is life in the universe? The Drake equation tries to calculate that, giving a back of the envelope calculation. But since the variables aren’t defined, what result you get is dependent on what assumptions you go in with.
First variable — N, the amount of life in the universe right now. Now, Kevin would argue that life in the universe isn’t meaningful because other galaxies are so very far away. But life in the galaxy could potentially be relevant.
Next variable N* – So, the # of stars in our galaxy is roughly 300,000,000,000 to 400,000,000,000. And our galaxy is big. It’s not a monster like M-87, but we could argue that the shape of our galaxy is conducive to life. Galaxies like spiral galaxies tend to compress matter in the disk.
Now our notion of our galaxy’s shape has changed in the past few years, so we think it’s a barred spiral rather than a spiral. (Where the bar emerges from natural patterns of dust movement.)
Third variable fs – We think the stars that could foster life are F, G, and K, roughly 30% of them.
Fourth variable Np – Then how many planets do those stars have? Our star has 8. Some people say 9, but if they say pluto is a planet, you have to add 4 more, including Eris and some others.
Fifth variable fe – how many planets can sustain life? Well, you could do 1/8, because ours does, or you could do 3/8 because Mars and Venus might be able to host life. If you warmed Mars with CO2, or blew off the outer layers of Venus’s atmosphere. Tweaking these planets would take them into the goldilocks zone.
We’re discussing binary star systems and habitable planets again. A quaternary system, Epsilon Lyrae comes up.
So if we’re looking for intelligent life, we want to be in the goldilocks zone (the temperature band most hospitable to life). However, if we’re just looking for life, then the possibilities expand. There are two moons of Saturn, for instance, that may have liquid oceans, and could host life. This allows us to “play fast and loose with our fe term”, although Ian laughs because it was never that well-defined anyway.
Variable fl — of planets that could have life, how many actually do? Now you’ll often hear planetary scientists on TV and on documentaries that we study other planets to learn about earth. Is that true or is that what we say when we want money? Well, actually it is true–we learned about the greenhouse effect by studying Venus. So now what we’re doing is taking what we know about earth and applying that externally. So, we constrain planets with possibilities of life to those with liquid water. But liquid water has lots of different potentials.
For instance, now we’re looking at an overhead view of a geyser with liquid striped in different colors, each band corresponding to a different organism. This geyser is about 300 Celcius, so we notice that life can exist outside our normal range of expectations. Similarly, we see birds pecking at glaciers, eating worms that we call ice worms… so anyway, we find that where we find life is expanding. Any time there is a niche with a possibility of having a source of energy, we find life there. We’ve found bacteria that eat basalt. (and of course there are iron-breathers, too, underwater.) So Kevin found a professor who studies extremophiles and he notes that if you haven’t studied biology in the past 15 years, you haven’t studied biology. We have life in the deepest of earth’s trenches, 7 miles below the surface, in vents where there’s super-hot water streaming out from the earth, there is life based on different chemistry than we are used to. If you turned off the sun, we’d all die, but things in the deep ocean that live off earth’s internal heat wouldn’t know anything happened.
So we don’t know if there’s intelligent life out there, but we’re relatively sure there will at least be bacterial life. We’ve seen amino acids at any rate. We may find that alien threats are microscopic.
Now, people are debating whether we should add additional terms to the Drake equation. Do planets need plate tectonics to have life? Some say yes. Is there a galactic habitable zone? Going back to looking at the stars around the galactic center, if you were to have life there, even with an atmosphere and a magnetic field, the radiation density would be so strong that it would probably eradicate life. Too far away from the galactic center, there may not be enough metallicity because the stars aren’t being born from clouds that had stars in them previously (since heavy elements come from massive stars).
Lc/Lg–all these assume the here and the now, but civilizations probably have lifetimes. If a civilization doesn’t get off its planet, it dies. Even if it does… it probably dies. So civilizations are time-dependent. So you have to think about the lifetime of the civilization as divided by the galaxy. There may have been civilizations before, and may be civilizations after, but we may miss each other in time.
Answers to the Fermi paradox–where are they?
*Maybe they don’t exist.
*An inhospitable universe may destroy complex intelligent life, possibly before it even begins. There are many galactic threats, such as gamma bursters, asteroid and comet impacts, and ambient radiation. For instance, if a gamma burster occurred at any point in our galaxy and we were in the cross-hairs, life on earth would persist for about half an hour. We’ve had five major extinctions in the history of the planet, at least three of which were impact-related. Ambient radiation is the argument for why you might not get life in the center of the galaxy, since radiation tends to destroy molecules of life as we know it.
*It may be the nature of intelligent life to destroy itself… with things like nuclear weapons, antimatter weapons, or biological/chemical weapons. Or more subtly, probably, too, if you want to make some kind of cultural argument.
*It may be the nature of intelligent life to destroy others… Daleks, van neumen machines… although if this is the case, then why are we still here?
*It’s always possible that God created humans alone.
*They do exist, but communication is impossible due to problems of scale…
*Intelligent civilizations may simply be too far apart to communicate. Our radio sphere is about 90 light years. That’s not very far, considering our galaxy is 75-100,000 light years. That could explain why no one’s talking, or even why the Daleks haven’t shown up yet.
*We could also be too far apart in time to communicate.
*It may be too energy costly (or too expensive) to spread physically through the galaxy.
*It’s possible that humans haven’t been searching long enough.
*Maybe they just haven’t gotten to us yet, such as in the movie Contact. The incoming message could still be incoming.
(Side note: Zeta Reticuli)
*They do exist, but communication is impossible for technical reasons…
*We could not be listening properly. Maybe they don’t use radio.
*It’s possible that civilizations only use radio for a limited period of time. Maybe they switch to digital broadcast as we just did. That would make them harder to detect because you can’t come into the middle of a signal and decode it as easily.
*They could be too advanced because they’re through the technological singularity.
*They do exist, but they choose not to communicate
*The zoo hypothesis–they see us as beneath them, or they’re letting us grow up, or they’ve isolated us for any possible reason
*They could see us as vermin
*They could be uninterested in talking to us because they’re xenophobic, or conceited
*They could want to avoid us for religious reasons (which raises questions about how people on this planet will deal with alien life, whether it will upset our religious sensibilities)
*Could not believe in life elsewhere
*They could be unobserved
*Maybe they’re hiding
*Maybe we have evidence, but don’t know how to interpret it
So. A few years ago in Britain they tried to find the funniest joke they could. The funniest joke, they decided, was a restatement of the Drake equation.
Sherlock Holmes and Dr Watson went on a camping trip.
After a good meal and a bottle of wine they lay down for the night, and went to sleep.
Some hours later, Holmes awoke and nudged his faithful friend. “Watson, look up at the sky and tell me what you see.”
Watson replied, “I see millions and millions of stars.”
“What does that tell you?”
Watson pondered for a minute.
“Astronomically, it tells me that there are millions of galaxies and potentially billions of planets. Astrologically, I observe that Saturn is in Leo. Horologically, I deduce that the time is approximately a quarter past three. Theologically, I can see that God is all powerful and that we are small and insignificant. Meteorologically, I suspect that we will have a beautiful day tomorrow. What does it tell you?”
Holmes was silent for a minute, then spoke.
“Watson, you pillock. Somebody has stolen our tent.”
When they did the same thing in the US, all the jokes were dirty.
No, says Bud, the funniest joke is the hunting joke.
Two guys decide to go hunting one day. So they get all of their gear and equipment and their rifles and head out into the woods. After a bit of searching they find a group a deer. The two split up and find places to shoot. The first guy sees a shape moving not far in front of him. He lines up his target and takes the shot. But when he goes over to it he finds out it’s his buddy and he’s not moving So he quickly grabs his cell phone and calls 911:
911: Hello, 911 Emergency, How can I help you?
Hunter: (hysterical) I shot my friend! We were out hunting and I thought he was a deer. I think he’s dead. Oh, God.
911: Sir, I need you to calm down and do exactly as I say.
Hunter: O..Okay I…I’ll try…
911: Okay sir, the first thing I need you to do is make sure’s he’s dead.
Several shots can be heard.
Hunter: Okay, now what?
Ian: Was Drake British or American?
Kevin: He’s from UCSC (which, geez, I went to UCSC, I so would have gone.) Kevin then recommends SETIcon which takes place like 15 minutes from my parents’ house and OH YES I AM SO THERE.
So, yeah, the lecture is over, but we’re in questions. We’re talking about meteors. I missed the initial question. So people are searching for meteorites. Every year, they send people to the Antarctic to collect meteorites. The first sample found was the size of a potato which was sealed up and packed on a museum shelf for 9 years. On examination, it was found to be a Mars rock. We know it’s from Mars because in 1976, the US landed twice successfully on Mars (the two Viking spacecraft), measured the rocks and the atmosphere and the soil and so on. So when we found this rock on Earth they drilled into the rock and extracted the gases and found basically Mars’s atmosphere. They looked at the time since it had been molten, and it was 1.3-2.6 bil years old, well after the formation of the solar system. So everyone agrees that this came from Mars. They drill in and find something that looks like bacteria, and this is in a carbonite rock, similar to limestone. So is this a Martian fossil? We’re not sure. There was a press conference in 1993 which announced this as an open question, and the doubter at the time pointed out that the size of these objects is too small to be bacterial. These are 1/100th the size of the smallest life we’ve found on earth. So he thinks this was too small to be life. However, there are some markers that suggest lifeyness, and recent re-examinations seem to have bolstered the fossil claim. The newer spacecraft that have landed on Mars have found that Mars used to be warmer and wetter, with liquid oceans, which suggests there could have been life. But we don’t know.
Basically, if there was life in the soil, we should be able to find it with the 2009 Mars science laboratory.
With Viking, those experiments were messed up. We had biases. We didn’t know.
Carrie, “So we get a better idea of what w’re looking for as time passes?”
Kevin, “Yeah, science happens iteratively.”
We had looked at Mars with Viking,and since we didn’t find life, people got bored quickly. So over time, the 1982 Viking ended, and people got excited about stuff happening further in the solar system. So in late 80s, early 90s, someone noted we don’t know the weather on Mars, so why don’t we take a typical earth weather satellite and send it to Mars and call it Mars Observer. So we start Mars Observer and scientists and engineers added and tweaked things, taking a simple idea and making it a $1 billion mission. So we built Mars O and sent it to Mars, and it… blew up.
Mars Global Surveyor shows images of rock shaped by standing water. So where did the water go?
So Odyssey goes and it could peer into the upper meter of martian soil and figure out whether there was water there, and it was there. The water sank into the ground, froze, and became permafrost.
Pathfinder — Mars has dust storms every two years. Dust coats everything. You can nuzzle up to a rock, and it’s coated in dust. They got some good compositional measurements, but there was dust on everything. So they have to drill into the rock and measure that.
Mars Reconnaissance Orbiter, then Mars Science Laboratory
Previous spacecraft raise questions that the new ones can answer.
What does Kevin think about panspermia? Kevin: that just pushes back the question a level. I don’t buy we didn’t form here. We do find complex molecules in meteorites, amino acids and such, and on Titan, we know these things form in space. The Miller-Urey experiment in 1953 at UCSD (possibly) took a flask they had water with lots of various elements they expected to exist in early earth, and they heated it, and then they sparked it as if with lightning. they did this over and over for a week, and did eventually get amino acids, so that’s a simple model of the early earth. people have redone this, altering the composition as we know better what was at early earth, and they find the same thing.
so what causes life to form from the amino acids? we don’t know, though the atmosphere was different then than it is now, and it’s possible life would not have formed with our current atmosphere.
Kevin: Single-planet species don’t survive. Ask the dinosaurs. I think we need to get off this rock as soon as possible.
Contrary to popular belief, spacecraft designers dislike high tech. You’d think to explore the stars, you’d want high tech–but no, high tech is untested and prone to fail. That’s why Pathfinder was a technology prover, with any science being a benefit. Same for Deep Space One. They want to test the technology so they can get it onto new spacecraft.
We do better when we have a focus and can name a goal.
Kelly: So what was the goal with Constellation?
Kevin: Return humans to the moon and get them safely home. Eventually set up outposts and permanent stations. Learn techniques that might benefit going to Mars. Landing is not one–landing will be easier on Mars–but living in a radiation strewn environment with emergency help 3 days away instead of 3 months away… we’ve also considered going to a meteor, which wouldn’t give us that benefit. Although it might give us a chance to experiment with nudging one out of our way.
The traditional notions of asteroid, etc, are blurring. Those that would threaten earth are traditionally metal and rock. If you hit one with a nuke as they did in a movie, the asteroid would shrug. And if it breaks, it could do worse, because the impact saturates.
Hit a comet with a nuke and you’d probably save yourself.
With an asteroid, we’re realizing slap an ion engine on it and slowwwwly nudge it away.
Ian: You have to catch it in time.
Cecilia points out that while this all seems very prohibitive to humans, there have been plenty of things we thought humans couldn’t do–even climb Mount Everest–that people do frequently now.