A Universe Full of Planets

http://www.nytimes.com/2013/07/26/opinion/global/a-universe-full-of-planets.html?hp&_r=0

by sew • 13 years ago

109 55 13 years ago

nytimes.com

Zikes• 13 years ago

I think this link will bypass the paywall: http://www.nytimes.com/2013/07/26/opinion/global/a-universe-...

baddox• 13 years ago

Still a paywall.

ludwig• 13 years ago

Use Chrome's incognito mode.

Wingman4l72• 13 years ago

Usually you're hitting the paywall if you see "&gwh=" in the URL and a huge string of characters after it that is presumably some sort of hash.

GuiA• 13 years ago

This is one of the topics that I find the most fascinating, and if I die before we learn more about life in the Universe other than on Earth, I will probably be very sad that my life span did not coincide with its discovery.

There's an entire body of knowledge that we cannot chart yet because we have no data to formulate it from. It seems likely and intuitive that if there are life forms on planets other than Earth, they are subject to evolution; but we cannot hypothesize much further than that.

Under what conditions does sentient meta-cognizant life evolve? How does it develop culture, religion, mathematics, art, philosophy, language? (has the Church-Turing thesis been formulated identically somewhere else than on Earth?) Which of those are constants amongst such species, and for the ones who aren't, what leads to their creation? How intertwined are they to biology? (e.g., death and religion) How frequently does the notion of "gender" happen in complex living structures? Do principles of cultural development such as the ones presented in "Guns, germs and steel" hold for non-Earth civilizations?

And if we find advanced sentient life that is much older than we are, that will be even more interesting. Are there events that this civilization went through/constructs that it built that are similar to ours? (various notions of democracy/freedom/government; mechanical transportation, "computers", electricity, digital communications, artificially expanding life (i.e. healthcare), etc.)

"Xenopology" is going to be one fascinating subject[1]. And on a related note, if any one is aware of serious academic work in that field (it seems pretty much impossible right now, because we just don't have the data; but you never know), I'd love to hear recommendations :)

[1] With fascinating consequences when it arises, too. We'll have to rewrite a lot of the more "meta" Wikipedia articles, for starters (Wikipedia is terribly anthropo-centered). And then, what will happen with our body of knowledge? We will merge human mathematics with xenomathematics? (if it's even possible) If they have a communications construct comparable to the internet, do we keep the two separate? Do we want them to be able to communicate at all on an individual level, much like any human on Earth can email any other human on Earth freely right now? Those are all of course very hypothetic considerations, but they're probable and fascinating to think about.

Wingman4l72• 13 years ago

Do principles of cultural development such as the ones presented in "Guns, germs and steel" hold for non-Earth civilizations?

I find this particularly fascinating, because it could lead to a corollary to the Drake equation. This equation would quantify the (possibly insurmountable) barriers that a species must overcome to become a space-faring civilization: strength of the planet's gravity well, ease of access to and total planetary quantity of rare elements required to build space hardware, etc.

Basically, Guns, Germs, and Steel -- but on a planetary scale.

TeMPOraL2• 13 years ago

The Great Filter - http://en.wikipedia.org/wiki/Great_Filter.

Note some "fun" consequences of this argument:

-- quote --

With no evidence of intelligent life other than ourselves, it appears that the process of starting with a star and ending with "advanced explosive lasting life" must be unlikely. This implies that at least one step in this process must be improbable. Hanson's list, while incomplete, describes the following nine steps in an "evolutionary path" that results in the colonization of the observable universe:

    1. The right star system (including organics and potentially habitable planets)
    2. Reproductive molecules (e.g., RNA)
    3. Simple (prokaryotic) single-cell life
    4. Complex (archaeatic and eukaryotic) single-cell life
    5. Sexual reproduction
    6. Multi-cell life
    7. Tool-using animals with big brains
    8. Where we are now
    9. Colonization explosion.

According to the Great Filter hypothesis at least one of these steps - if the list were complete - must be improbable. If it's not an early step (i.e. in our past), then the implication is that the improbable step lies in our future and our prospects of reaching step 9 (interstellar colonization) are still bleak. If the past steps are likely, then many civilizations would have developed to the current level of the human race. However, none appear to have made it to step 9, or the Milky Way would be full of colonies. So perhaps step 9 is the unlikely one, and the only thing that appears likely to keep us from step 9 is some sort of catastrophe or the resource exhaustion leading to impossibility to make the step due to consumption of the available resources (like for example highly constrained energy resources). So by this argument, finding multicellular life on Mars (provided it evolved independently) would be bad news, since it would imply steps 2–6 are easy, and hence only 1, 7, 8 or 9 (or some unknown step) could be the big problem.

-- quote ends --

(emphasis mine)

In other words, finding life on Mars would suggest that the Great Filter event may be ahead of us, so we're probably screwed.

sampo6• 13 years ago

It took 3 billion years from then beginning of life to the appearance of first animals (with the inventions of eukaryotes and then multicellular life as important milestones along the way).

Then it took ca. 500 million years to Homo, and 5 million years for our species to develop technology.

So I'd say the road from microbial life to cavemen was 1000x larger barrier, then the road from cavemen to technology. Also the barrier from microbial life to first animals (let's assume some kind of worms) was 10x larger than the barrier from worms to technology.

In summary, getting early microbial life to get organized into some kind of macroscopic animals, this is the hard part. When that is done, vertebrates, dinosaurs, hominids and internet will follow at 5–10x faster pace.

http://en.wikipedia.org/wiki/Evolutionary_history_of_life

Steko• 13 years ago

It could well be that all advanced civilizations decide that it's easier to answer these questions with simulations than observation. More interestingly if that is true and you also believe the odds of a singularity in our future is high, then the odds of us being in a simulation now are quite high.

lukifer• 13 years ago

The simulation theory would also explain some weirdnesses about quantum mechanics; I remember reading a piece by a quantum computing researcher[1] saying that the universe can be modeled as the largest ever quantum computer; at some point, simulated universe and real quantum universe become a distinction without a difference.

[1] Pretty sure it was Seth Lloyd's "Programming the Universe": http://en.wikipedia.org/wiki/Programming_the_Universe

vidarh6• 13 years ago

It sounds like you've probably read The Simulation Argument, but for those who haven't: http://www.simulation-argument.com/

It is more specific than it needs to be - it uses the hypothesis that we will want to run simulations of our past history. But of course such simulations would not be constrained to that.

Philip K. Dick wrote a short story about this, where little spheres with artificial worlds becomes a massive fad, but then someone realises the people on those world might actually be alive and intelligent. I can't remember the title.

incompatible• 13 years ago

It is fascinating. Imagine if we did detect a radio signal from intelligent life elsewhere. What sort of reply would we send them? I imagine it would be every sort of reply imaginable, as everybody with access to a radio telescope gave it their best shot. I expect a lot of new radio telescopes would be constructed also.

If we don't receive any such signals, then finding life elsewhere is going to be a long, hard slog. It seems we don't yet have the energy/technology levels required to get a probe to another star within a reasonable amount of time (100 years travel time, would perhaps be reasonable? Could any of our equipment last that long?) Self-replicating space probes that could exponentially explore the entire galaxy seem to be right out of the question, at present.

murtza• 13 years ago

If you are interested in exploring this topic more, the fiction book Contact by Carl Sagan is based on the premise of detecting a radio signal from intelligent life. It is a great book that you will make you wonder what effects contact from intelligent life elsewhere would have on human behavior.

vidarh6• 13 years ago

Self replicating space probes that could exponentially explore the entire galaxy (or universe) is one of the things that might indicate a sparsely populated universe, or at least one where any other forms of life is quite young.

Assuming it is possible to make such probes for a relatively young civilisation, and most civilisations that reach that stage does send out even just one probe that starts relicating, if life is abundant around us we should expect to have swarms of them everywhere.

Of course it could be we just can't detect them yet, or that life is abundant but that life old enough to be advanced enough to do this is rare for some reason.

sampo6• 13 years ago

I've got the impression that spectroscopic methods that would be able to detect the major composition of the atmospheres of exoplanets at 10–100 light years away, are almost around a corner now. Maybe in 10 years?

Then if we find a planet with an atmosphere that is far from the thermodynamical equilibrium, like our 21% oxygen is because of photosynthesis, then that might be a planet with planetary scale life.

nikster• 13 years ago

It seems the most likely would be that most planets are inhabited by life forms that aren't intelligent. Out of 13Bn years, humans in any form have been around 1M years. Civilized societies only a few thousand. We'd find many more planets with Dinosaurs on them (they lasted 200M years)....

The thought that 1 out of 7 suns has earth-like planets is still amazing though. Wouldn't it be rather likely that an advanced intelligence is watching us at that point?

arrrg• 13 years ago

Though we currently do not know how long civilization will last - but I would have to agree that from right here it seems too fragile to endure 200 million years.

sampo6• 13 years ago

Or just microbial life, which lasted 3 billion years, which is 15x longer than the 200 million for dinosaurs.

Zigurd2• 13 years ago

Why haven't they called?

If planets are abundant, that puts the kibosh on the "rare Earth" theory, as shaky as that was to begin with. The other explanations are less optimistic: Maybe they all nuke themselves or turn to grey goo before they can muster the technology and energy to build a starship. Or they are roasted by random blasts of radiation before they become space-faring.

It's either something universal about civilizations, or something is wrong with the Drake equation or the underlying cosmology.

Renaud• 13 years ago

Or we've been going at this for way too short a time to be able to draw definite conclusions.

There are hundreds of plausible reasons why, if there is life outside, we haven't been contacted. Maybe they know about us but we're not interesting, maybe they don't know about us, maybe they tried to contact us but we haven't been able to detect them, maybe we just don't have the right technology, or we're not looking in the right place, maybe we're all limited by these pesky laws of physics and there is no chance that we could ever meet or even know about each other, maybe they are not looking in the right place and missed us, maybe they are not yet aware of our existence since we've been emitting radio for such a short time, etc

Zigurd2• 13 years ago

All those objections, have, I think, been factored in and yet the odds should be overwhelmingly in favor of life making itself known. For example "we've been going at this for way too short a time," but we know that millions to billions of stars are billions of years older than the Sun and that millions of those stars have planets.

The thing about the scale of the universe is that the odds are always cosmically against "That just hasn't happened yet" being the right answer.

InclinedPlane• 13 years ago

Space is big.

Let's say someone was beaming a very strong signal at us, would we have detected it by now with all our SETI programs? Nope, not very likely we would have. We've only scratched a tiny bit of the search space with SETI, spatially and in wavelength.

Similarly, what if an Earth-twin existed in a stellar system within 20 light-years of us, would we have detected it by now? Again, also no. It would take rather a lot of luck for us to have detected it by now, our methods of detecting planets are very limited. It will likely take many more decades before we can confidently have a nearly complete survey of exoplanets near Earth, let alone at greater distances.

As far as the Fermi paradox, I never bought it as a paradox. All it says is that we probably don't understand the nature of space-faring technological civilizations, which we clearly don't, nothing more.

btilly• 13 years ago

Don't talk about planets within 20 light years, we probably haven't even found all of the stars within 20 light years!

See http://science.psu.edu/news-and-events/2013-news/Luhman3-201... for proof that we found stars THIS YEAR within 6.5 light years of us. What else is out there? We don't know.

Balgair4• 13 years ago

There are many reasons: Here are a few:

A) The universe is very large. The nearest star is 4 and some change lightyears (ly) away. That means any message take over 8 years to get, process, and transmit to the nearest star. All other stars are further than that. Since we have been weakly radio broadcasting for about 100 years, the number of stars we have been able to speak with is at best 1600 (http://wiki.answers.com/Q/How_many_stars_within_50_light_yea...).

B)Messages get lost in noise. We assume that we are heard out in the universe. But it is very very difficult to hear a mosquito at a rock concert 100 miles from you. The reverse is true for us. Also, you have to know to look. The concert has been going on for 100 years but the venue, so to speak, is 4 billion years old. Also, you might be on the other side of the galaxy, or in another one entirely.

C)Messages aren't understood as such. Do you know the protocol for USB to serial conversion? (If so I have many questions for you) We may think an actual message is just noise. Or, that noise is a message. We cannot possibly tell. Yes hopefully the other side will start out easy on us but define 'easy' to an alien.

D)Lets assume that they have spotted us and are pre-sending signals. In what medium? We haven't even figured out the basic laws of the universe yet. Heck Dark matter is ~25% of the mass-energy of the universe. The other ~75% is some crazy stuff we just labeled Dark Energy. We have no clue what is going on there. They may already be blasting us with data, but we just haven't got the interstellar radio invented yet.

E) They simply don't give a shit. What do we have that they want? Lets assume they are about 10,000 years older in tech than we are. Geologically speaking, thats nada, thats the last ice age. People were around then. And look now we have radios and iPads and ISS's and stuff. 10,000 years is a lot of time to think and make stuff. What could we do in that much more time? Well, make a computer that'll calculate just about anything, probably. And if your civilization is all entertained, why bother looking at the stars? Why bother with a,likely, giant telescope array that beams out gibberish for a thousand years. What stuff on Earth over 1000 years old? Not all that much but piles of rocks and some windows. The engineering of a giant thingy is very hard. And all for what? Some algae that you hope turns into a little curious squid or something?

F) They dont give a shit. Not because they are hedonistic but because they live under an ice-sheet the planet wide. Or they are at the bottom of a giant cloud where pressure is just right. Or they are frozen periodically in ammonia ice for 700 years. Or they have no idea of math and science because they don't have nerves that work like that. Or because they don't have cells at all. Or because they have no photoreceptors and can't even begin to imagine light. Or because they think that thing we call matter is just a rounding error. Or because they already migrated into dark energy beings and are just waiting to see us.

G) We are just plain jane alone.

drhodes• 13 years ago

Information theory can discriminate between noise and language, (http://www.peterrussell.com/Dolphin/DolphinLang.php), Zipf's law (http://en.wikipedia.org/wiki/Zipf's_law),

vidarh6• 13 years ago

Here's a few more that I find fascinating:

H) They do give a shit, but they are busy hiding. Consider this: If there's only one civilisation out there sufficiently advanced to be able to accelerate large, heavy objects towards others at sufficient speed, and who has decided that clobbering everyone else is their best bet at long term survival, everyone else better hide unless/until able to throw rocks first. A sufficiently large object constantly accelerated over a distance of light years would be near impossible to protect against.

The solution might very well be that anyone chatty gets hit by a planet.

I) Something natural periodically wipes life out. E.g. consider if gamma-ray bursts occurs frequently enough, and are powerful enough, to cut down everyone that don't reach an extremely high technological level in a very short timespan.

J) We're in a simulation and they're not interested in simulating life on other planets (or the purpose is to simulate a universe with life only on earth).

spc476• 13 years ago

I'd like to think they're encrypting their communications and thus, it is indistinguishable from random noise.

GrantS• 13 years ago

Are you talking about this rare earth hypothesis? http://en.wikipedia.org/wiki/Rare_Earth_hypothesis

It's been a decade since I read the book but IIRC very little of it had to do with whether lots of planets exist. In fact they assume microbial life is abundant but argue against complex multi-cellular life being very common.

It's a fascinating book ("Rare Earth") but even without their arguments, I'm curious: why would one assume that planets equal civilizations?

kamaal3• 13 years ago

>Why haven't they called?

They probably have, or are trying to. But even if they want to, a start system say 2000 light years away looking at us is seeing the world as it was during the time of Jesus. And we are looking at them when they were equally ancient.

And not to mention, if they tried to communicate with us we won't know until the next 2000 years. Basically you get the point. For a civilization to communicate to us, they should've started the process of sending signals out x years, based on for x light years far they are.

And that's just the first problem. The universe is so big, each galaxy has billions of stars and there are some billions of galaxies in the universe. Given the vastness and size of universe, its next to impossible to search such a large space with already existing limitations of distance and time.

Thirdly, we've hardly been listening for a few decades, we might have missed a signal if it was ever sent out or haven't received one.

jussij• 13 years ago

Why haven't they called?

Here's how far our out going call has gone:

http://zidbits.com/wp-content/uploads/2011/07/how-far-in-spa...

Sharlin2• 13 years ago

It seems many people here make the implicit assumption that once there's life, there will be a technological civilization.

We do know that microbial life did appear quite soon after the formation of the Earth, so we have some evidence that life can bootstrap itself readily given a favorable environment. However, we also know that life then spent the next three billion years quite content at being unicellular, until the Cambrian Explosion made lots of things happen very quickly (at least on the astronomical timescale). We don't really have much ideas about why the CE happened, and how inevitable it was to happen at some point at least by sheer probability. I believe the shift from unicellular to multicellular life was the most fine-toothed of the Great Filters we've already passed - let us hope there won't be even stricter ones in our future. Given the number of ways it appears a technological civilization could snuff itself out of existence in an eyeblink, I'm not very optimistic.

sampo6• 13 years ago

We don't really have much ideas about why the CE happened

Look at the graph here:

http://en.wikipedia.org/wiki/Oxygen_catastrophe

It took 1 Ga from the invention of photosynthesis to grow enough biomass so that photosynthesis started to be a notable process in geological scale.

Then it took 0.5 Ga of photosynthesis, when the produced oxygen would dissolve into the oceans, until the oceans were saturated. Atmospheric oxygen remained at 2–4%.

Then it tool 1.5 Ga of hard work, when the land surface minerals would be oxidized, until they were all oxidized and finally oxygen started to accumulate in the atmosphere.

Then around 600 Ma ago the atmosphere hit above 10% oxygen, and this pretty much coincides with the Cambrian evolutionary explosion.

TeMPOraL2• 13 years ago

Why haven't they called?

Maybe for the same reason we're not "calling" that much anymore? For the last several decades we've been investing tons of money and engineer-hours to make radio waves stop going up, as we mostly need them on the ground, and we don't have cable or cellular subscribers in space.

cletus• 13 years ago

Like many here I find the subject of finding life on other planets fascinating and consider it inevitable. What's interesting is that the estimate of planet incidence is seemingly much higher than originally postulated by the Drake Equation [1].

A factor in the development of life, especially sentient life, is metallicity [2]. Almost all of the first 100 elements naturally occur on Earth. This is pretty amazing. Nuclear fusion in stars naturally produces elements up to iron [3]. S-capture is thought to produce elements up to Bismuth (atomic number 83). Elements higher than this are thought to be produced only in supernovae or other cataclysmic events.

It's amazing to think that enough time has gone by in the Universe to take the abundant hydrogen and helium, form stars, have those stars run out of fuel and enough of them explode to scatter their elements to form heavy planets around later stars.

While heavy elements may not be required for life it seems less likely that starfaring sentience can form without them. Semiconductors for example require an odd mix of heavy elements.

It seems amazing that even we exist given that you need metals, a long-lived and stable star, likely billions of years of evolution, a sufficiently stable (and probably geologically active) planet with an atmosphere that has water in liquid form (a pretty narrow temperature band even taking into account different atmospheric pressures) and no cataclysmic events to happen in all that time (it seems to have been ~65 million years since the last big one).

It may just be that sentient life is fleeting. We've had "civilization" for X0,000 years, which is the blink of an eye. It's entirely possible we'll wipe ourselves out due to war or simply lack of (sufficiently cheap) resources in another blink. The problem isn't lack of resources. They are plentiful in space. The problem is the cost of getting them if energy is anything other than free.

Additionally interstellar distances seem almost unconquerably large that one has to wonder if we'll ever meet another sentient life form face to face (assuming they have faces).

Even if we do, one wonder what evolved elsewhere for facilitate communication. Will they see? Will the wavelengths of light they see cross over ours at all? These are questions we can only really speculate about.

It's also been suggested (by Hawking among others) that we really don't want to meet a much more advanced species as it will probably be bad for us, perhaps even an Outside Context Problem [4] and it seems unlikely given the rate of change we're experiencing that another civilization will be at the same point as us.

We could of course be "first". I mean someone has to be right? It does seem unlikely however. But I suspect there were many "firsts" (in the sense that they evolved independently and without any contact or evidence of other species).

The seeming lack of self-replicating robots, something we'll almost certainly be able to build and start filling the galaxy with within a thousand years I'm sure, is also somewhat puzzling.

Personally I just hope we find evidence of extraterrestial life sometime soon as it will settle [5] a whole bunch of issues about us being "special" (in the typically religious sense).

[1] http://en.wikipedia.org/wiki/Drake_equation

[2] https://en.wikipedia.org/wiki/Metallicity

[3] http://hyperphysics.phy-astr.gsu.edu/hbase/astro/nucsyn.html...

[4] http://en.wikipedia.org/wiki/Excession#Outside_Context_Probl...

[5] http://xkcd.com/1235/

prawn• 13 years ago

"What's interesting is that the estimate of planet incidence is seemingly much higher than originally postulated by the Drake Equation."

I always assumed that the estimates there were purposefully low to show "Hey, even with all these low estimates, we should still find something, right?"

dkural• 13 years ago

The universe never does anything just once.. black holes, gamma ray bursts, supernovae, planets, and yes, life.

RickyShaww• 13 years ago

Don't we know this in high school. Of course the universe is full of planets.

grannyg00se• 13 years ago

Here's the new and surprising take-away:

"In other words, roughly 15 percent of all suns could, in principle, be hosting a place suitable for life as we know it. "

vidarh6• 13 years ago

Unless you left high school within the last few years, no we didn't. We might have assumed, but the evidence is quite new.

vidarh6• 13 years ago

It fascinates me to think about what this will mean to science fiction. There's obviously lots of sci fi that assumes lots of planets out there, but just like actually going to the moon means sci fi depictions of the moon "had to" align with what they actually found and it altered depictions of space ships and suits (and caused endless crappy attempts at trying to capture "low gravity"), it will increasingly "have" to deal with actual facts about what's out there.

marcosscriven• 13 years ago

One idea that fascinates me is the possibility of two planets in the same solar system evolving intelligent/technological life. How amazing would it have been to have been one of the first astronomers on such a planet, and see macro-structures like large cities on another planet.

wikiburner• 13 years ago

I often wonder how much more advanced our space program would have been by now had Mars or Venus been habitable.

A Universe Full of Planets

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