Posts Tagged galaxy
In the first two entries in this series of brief examinations of the difficulty of traveling in outer space to new planets and stars and worlds, I looked at how difficult it is for humans to travel in outer space (we’ve only just made it to the moon), and whether the knowledge of the ability to travel to other stars and their planets really exists at all. Is such knowledge universally available, or are we condemned to travel long distances in spacecraft at well below the speed of light?
In this post, I want to look at the development of life on a fledgling planet and ask the question, what does it take for intelligent life to develop? In fact, I want to go back not only to the development of life, but further, to the birth of the planet itself. What conditions are necessary for a planet to develop life? This will be a tricky question to ask properly because we have only one known example where such conditions have arisen, the Earth, and we can’t be sure that what happened on Earth is a reasonable example for life developing elsewhere. But what the hell, let’s take a look.
Others have tried to estimate the probability of life on other worlds, and the Drake equation is one such estimate. But the Drake equation is concerned with estimating what fraction of planets out there are broadcasting signals into space, a point in evolution we have already reached. As with any examination of the presence of life on other worlds, estimates have to be made when entering data into the Drake equation, and in reality, we have no idea how accurate those estimates are. I’m more interested in trying to find out what percentage of planets that eventually coalesce into a physical body from the dust surrounding a newly-ignited star will eventually go on to develop intelligent life that can leave the bonds of the planet and fly around. Let’s take a look at some of the factors that have to exist before this can happen.
Over the past several years I’ve jotted down a number of factors that have been proposed as essential for the development of intelligent life here on Earth, and, with a little bit of luck, might be necessary for life to develop on another heavenly body.
1. A stable sun: the star around which such a planet orbits can’t get too hot or too cold, or it could halt development of life altogether. (Earth’s sun has gone through cooling and heating phases, but never to a degree that baked or froze the planet, killing life completely.)
2. The planet has to develop at just the right distance from the star. The so-called “Goldilocks” zone.
3. There has to be water on the surface. Not just water, but liquid water, liquid because life can’t develop in steam or ice.
4. The planet has to have an oxygen/nitrogen atmosphere. Granted, life can develop in the absence of oxygen, and probably did on Earth, and those microscopic life forms did produce the oxygen in our atmosphere, but it most likely oxygen will be required for intelligent life to develop.
5. The presence of oxygen in the atmosphere implies ozone in the upper atmosphere to protect the life forms on the surface from too much ultraviolet radiation.
6. A magnetic field surrounding the planet. This implies a liquid iron core and traps cosmic rays and other injurious stuff from outer space.
7. Another planet in the same star system that is large enough to clear much of the excess debris around the star to prevent too much from bombarding the nascent planet.
8. Yet, some bombardment is essential to bring all the stuff (like water) to the new planet that life will require. Not too much, not too little.
9. A large moon that provides a gravitational tug on the planet, inducing tides in the large bodies of water, as well as on the land masses, pulling and pushing them around in just the right way.
10. The planet should be in a near circular orbit so that the radiation it receives from its sun is relatively constant. Not too hot, not too cold.
11. Other planets in the same system have to be in near circular orbits to prevent them from sending debris toward the newly-formed planet, and preventing their gravitational field from pushing the planet into an odd orbit, or even knocking it out of its solar system altogether.
12. Tectonic activity to keep the developing life in a constant state of evolution. Stagnation is the death-knell of advancing development.
13. Periodic extinctions, whether caused by an asteroid strike, volcanic activity, the cooling of the central star, or other factor, to, as in #12, keep the development of life going. Or, to put it more simply, everything has to be shaken up from time to time.
In so many of these factors, not only are they essential in an absolute or qualitative sense, but in a quantitative sense too. Not too much, not too little. Earth got just the right amount of some things—just the right amount of oxygen, a sun neither too hot or too cold, just the right size moon, and so forth. That’s just going to complicate the calculations.
Now, with all these factors in mind (and there may be more we don’t know about), can we make any reasonable calculation as to what proportion of planets in our galaxy fit this profile? Are there other planets out there that could have developed life like ours? To make that calculation, we have to ask what proportion of planets meet each characteristic. That’s impossible to do right now, so we have to estimate. Such estimates may be way off, but let’s give it a try. Let’s assume the simplest situation (and probably an overestimate), that each planet has a 1 in 100 chance of having each characteristic. This works out to 1/100 to the 13th power, or 10 to the −26 power. That says that only one planet out of 10 to the 26th has all the characteristics needed for life to develop. It is estimated that around one hundred billion planets exist in the galaxy. That’s 10 to the 11th power. Okay, make it 10 to the 12th. Clearly, even if we use a serious overestimate to the chances of any characteristic happening on a developing planet, we’ve just eliminated not only the possibility of life developing on another planet, but on our own too. We shouldn’t even exist. Yet, there’s good evidence these characteristics are essential. We can’t just drop two or three. The numbers just don’t add up.
So, where are we? Those numbers do give one possible explanation to Enrico Fermi’s famous paradox, but they are such an overestimate it’s hard to know if that’s the right explanation or not. It is possible that life could develop on other planets in situations we’re not familiar with, after all, we’re using Earth as an example and that may not be the most judicious model. Are we freaks in one way or another? Are we alone? You be the judge.
In the previous entry in this series of blog posts about the possibility of alien life in our galaxy, and especially about such life visiting us here, I speculated about the wide disparity between the knowledge we’ve obtained about the universe—which is substantial—and our ability to move around in that universe—which is miniscule. We’ve only just gotten to the moon. Is that the reason we’ve never been visited by aliens from other star systems—that the distances are just too immense and space travel is not as easy as our science fiction stories make it out to be? Or is it that they are really nowhere to be found?
There’s certainly no shortage of stars in our galaxy around which planets could form that potentially could harbor life. But before any civilization can visit us here, a lot of things have to happen. It has taken us 2 billion years and several major extinctions for us to reach the sophisticated level we’re at right now. We can see galaxies that are billions of light years away, but we’re a long way in time from journeying there. We’re a long way from visiting even just the nearest star for crying out loud! Any other intelligent civilization almost certainly has to go through that same process of learning about the cosmos before they can make the leap from simply knowing about the presence of other suns out there, to actually visiting them. That’s a huuuuuge step.
So, I’m wondering, how many civilizations out there have actually made that step? Or is there a limit to what a civilization can do?
There’s a hypothesis about alien civilizations that postulates a “Great Filter” that has prevented most if not all civilizations from reaching the ability to travel the galaxy and visit us here on Earth. Somewhere, the Great Filter suggests, in the evolution of a civilization, the inhabitants of a planet reach a stage where their ability to continue is blocked. That’s a legitimate argument, especially as there are at least two processes that could possibly prevent us on Earth from moving on to visit other planets and star systems—annihilation either by nuclear war or by global warming. We haven’t done a particularly good job in reducing the risk from either one lately. But it’s one thing to postulate that, on the one hand, these processes are a risk for us on Earth, and, on the other, transferring those possibilities to other planets. In some respects, the Great Filter seems almost too anthropomorphic, that what happens on Earth must, of necessity, happen on other planets.
One thing we can be sure of, however: that an alien civilization must acquire knowledge about the universe and the galaxy in which we live in order to visit us here, and it must develop the means of transportation around it. But where does that knowledge lie that would allow them to close that gap? Does it exist? Don’t look to science fiction for the answer.
It’s entirely conceivable that a breakthrough will occur in the (near?) (far?) future that will allow us to travel to distant star systems. I’m not ruling that out. And it’s also possible that knowledge is available to any and all civilizations which can reach the highly sophisticated stage where they have access to it. It’s more a question of a civilization being able to make it to that stage. How many civilizations have reached that stage? None? Or does that knowledge even exist? At least that would answer the question: “Where are they?”
This is likely to be the first of three postings on a topic that has intrigued me for several years—the prospect of intelligent life on other planets. Enrico Fermi posed his famous paradox, basically “Where are they?” in 1950. He was referring to the question of why highly intelligent, highly sophisticated visitors from another planet haven’t visited us here on Earth. With the tremendous number of planets out there, say 50 to 100 billion in our galaxy alone, surely the chances must be around 100 percent that other life forms have developed, and a small population should have attained the ability to travel the galaxy in some form of advanced spaceship, perhaps with a drive system we can’t even conceive of. Many planets out there must be older than ours, giving their inhabitants sufficient time to develop space drives that can cut travel time from star to star down to a reasonable value. And that’s what I want to limit my comments to here in this post—the concept of actually travelling the galaxy. Keep in mind, I’m not trying to answer the question of “where are they,” just give some possible reasons why they aren’t.
I want to start by looking at the development of life on Earth and see if we can extrapolate into the future. The Earth is, of course, the only planet we are aware of on which intelligent life has developed, and that could mean it isn’t the best model on which to build an example, but it’s the only one we’ve got so I’m going to use it. Life began on Earth around 2 billion years ago. (There’s some evidence life may have evolved earlier than that, but I’m going to use 2 billion as a nice round number.) In those 2 billion years, life has not once died out completely. There have been extinctions, sure, and large numbers of species have been eliminated, but life has managed to remain continuous in one form or another since then. Even the grand extinction which resulted in the eradication of the dinosaurs around 65 million years ago didn’t completely eliminate all life. Small mammals survived the asteroid impact, and even the dinosaurs themselves were not totally eliminated—they survived into today as birds. Up to that time, reptiles were the dominant animal life form. They were the ultimate, the top level, the upper crust. They basically formed an endpoint, as far as evolution was concerned at that time, and it took an outside event to force a change. Now, I suppose, mammals are the top animal life form. We dominate the planet, and have made changes no other animal could ever conceive of making.
Over the last few thousand years, we humans have learned a lot about the universe in which we exist. We’ve built telescopes which can probe well beyond our own galaxy and see millions of others. We’ve learned what goes on in the interior of a star, in its core, in the atomic and subatomic interactions which produce the light and heat and all the other emissions that the star puts out. We can even detect the faint, wispy neutrinos the star emits. We know there seems to be unseen forces and masses in the galaxy which make up the majority of all mass and energy in it. We’ve seen stars and planets and asteroids, and even planets that just haven’t had quite enough mass to start the fusion reactions that make a star what it is. Behind this has been the development of elaborate mathematics that has made it possible. There’s so much knowledge we’ve accumulated over those several thousand years. All in all, we’re pretty damn astute about our knowledge of the universe and our place in it. We can be proud of that.
Yet, for all our sophistication and knowledge, we’ve never sent humans out into the void of space any farther than the moon. We’ve sent a couple of spacecraft to the edge of our solar system, but those are piddly jumps compared to the size of the universe or even the galaxy. Traveling the galaxy is a hell of a lot harder than looking at it. That’s why science fiction writers have to develop complex, intricate, and ultimately a little naïve spaceships to get their characters around, because there’s no real way to do it. Light travels at the speed of light; we travel at the speed of rocket ships. And the difference is telling.
All this suggests that if there are highly intelligent and sophisticated life forms out there capable of traveling the galaxy, or even from one galaxy to another(!), they would have to have knowledge and space drives so far beyond us they would be impossible for us to conceive. Perhaps harnessing a force we can only guess at. (Read more science fiction for a few good guesses.) Pardon the pun, but even in our sophistication, we’ve got a long way to go.
The title of this post isn’t meant to ask where you are in a spatial location, but in terms of time. Where are you—where are we all, for that matter—in the life of this universe? I’ve been thinking about this for a long time. We all live on a rather attractive blue, white, green and brown planet circling a rather ordinary yellow-white star in a rather ordinary galaxy somewhere in the middle of billions of other galaxies which together constitute what we affectionately refer to as the “universe.” This universe arose from a massive expansion of all matter and energy some thirteen billion years ago, and is rapidly expanding and expanding, apparently to go on forever, driven apart by wild forces within itself. It will go on for time immemorial, never to return to its original state. That’s, at least, the current thinking.
Here we are, sophisticated, sentient human beings, watching this all unfold, trying to make sense of it. I’ve wondered, ever since I heard of the “big bang” hypothesis, which is the current favorite explanation of how we got here, if there isn’t an alternative explanation, that the universe will eventually run out of steam and collapse back onto itself in a sort of “big crunch,” or “big splat,” from which it would rebound into another expansion and another universe, and so on, ad infinitum. That seems to me to be a more logical way for the universe to run than just one “bang” which blows up like a balloon and dissipates out in the nether regions, never to be seen again. The “single bang” theory doesn’t explain what came before the expansion, nor what will come after it. But that may be the way it really is. Dark energy seems to be pushing the galaxies apart faster than dark matter can keep them together.
Philosophically, this is mind boggling. We are the only species on this planet that really understands, to any degree whatsoever, the goings-on out there in space. We’ve been watching the skies for thousands of years. We’ve sent satellites into orbit to observe it. We’ve sent men to the moon. Do you think that cat or dog or goldfish or parakeet in your house cares much about the big bang? Do the deer and the wolves in the forest understand that the little red dot in the sky is a cold, solid planet rather than a blazingly hot star? Or even what a star is in the first place? No, just us. Yet we humans make up such a miniscule percentage of the universe, it’s difficult to estimate how many zeros I’d have to put down to the right of a decimal point to give that percentage. We humans are what I might call “universe sentient.” We know where we are, though we can’t travel very far in it. We’ve seen the stars, the Milky Way, and some of the other galaxies that make up our universe. We have a lot to learn, granted. But we are capable of learning it. We have the mathematical skills and computer skills to master the intricacies of the universe. No dog or cat, or even chimpanzee, has that. Most likely, other civilizations exist in our galaxy with similar skills, perhaps even more advanced. (Maybe they can tell us if dark matter and dark energy really exist.) But philosophically we are alone, and, I suspect, will remain alone for the foreseeable future.
Could life ever arise on the planet Venus? That is, Venus as it exists today. Venus is a hellish place, with temperatures of around 462°C at the surface, rain composed of sulfuric acid, lava-flows over much of the surface, and an atmospheric pressure around 90 times that of Earth at sea level. It’s not a pleasant place, and a manned spacecraft would find it difficult to land there, and it might be even more difficult for humans to get out and walk around. In fact, I think we can dispense with the possibility of humans walking on Venus’s surface for the foreseeable future.
Many billions of years ago, some scientists speculate, Venus may have had a climate similar to Earth. Water may have been present in abundance, enough to fill relatively shallow oceans. An atmosphere of oxygen may have existed that could have been conducive to life. But if it did, under the influence of the heat from the sun (Venus gets about twice as much sunlight as Earth) the oceans boiled away, the water was split by ultraviolet light into hydrogen and oxygen, the hydrogen escaped into space, and the oxygen combined with carbon on the surface to form carbon dioxide, and the greenhouse effect took over. That pushed the temperature into the stratosphere. So to speak. And here we stand today.
But the presence of water making life possible on Venus in the distant past isn’t what I want to hypothesize in this post. I’m thinking about the possibility of life on Venus as it exists now. Yes, in the presence of all that heat, lava, pressure, and sulfuric acid. Earlier, on March 13, 2011, in a blog post entitled “Life–A New Definition,” I suggested that life on any arbitrary planet should be defined as “that which arises . . . under the influence of the energy from its sun over and above any other milieu . . . .” That’s without regard as to what the life forms look like, or what they’re composed of, or how they replicate, or any other limiting factor we may require to define life on Earth. We can’t think of life on other planets within the limited range we find here on Earth.
So, what would life on Venus look like now? Under the influence of that tremendous heat and pressure, chemical reactions are running wild, at least in comparison with Earth. That might be a good thing. It might be the very factor that makes “life” viable on the surface. Lava may stay liquid all the time on Venus. Possibly a life form could arise composed of lava globules that slowly creep across the surface, consuming other bits of the ground, extracting necessary elements, metabolizing them by sulfuric acid digestion, and eventually dividing into smaller globules that continue the process. And that’s just one scenario. I’m sure others could be visualized by those who are better at chemistry than I, so there’s no sense in me speculating much further here.
I certainly realize that the chance of “life” actually existing on the surface of Venus is probably very low, and that speculating about what it looks like could be a somewhat unscientific pursuit. But the real reason for looking at Venus this way (sorry about that) is that it gives us a different way of looking at life in general all across the galaxy. (Think what it would mean if we did find some sort of life on Venus.) Life certainly exists on (a few? many?) other planets somewhere in our galaxy because there are so many of them, and we should always be aware that it won’t necessarily look like us. It may be so vastly different that we may not recognize it at first, and we have to remain open to any possible physical form, and any possible metabolic form. Temperature and pressure won’t necessarily be a limiting factor.
Last week I posted a segment on the lack of imagination in science fiction today, with a view toward how so many sci-fi characters are humanoid in appearance. Now I want to take a short look at what I’m talking about when I say “humanoid.”
In the evolution of animals over the past two billion years or so, there’s been a tendency for the sensory organs to become concentrated in the head. This is true for all the higher animals—and by that I mean basically those with a backbone and a large nerve cord running down the back—but it’s also true for some lower animals, such as insects and other arthropods. This is called cephalization, and it’s what is so often copied by us sci-fi writers when we devise characters to populate planets far, far away. This process has put four of the five traditional senses in the head: sight, hearing, smell, and taste. (The sense of feel, of course, is present throughout the body, we don’t have just one organ for that.) Why this should have happened evolutionarily, I’m not sure, but it may have to do with keeping the nerve fibers that run from the sense organs to the brain as short as possible. That may, in turn, have been to allow the information collected by those organs to be processed as rapidly as possible. If our eyes were in our kneecaps, for example, the nerve fibers would have to run all the way up the body to the head. Might be some loss of information in that long a trip. Secondarily, in a long, slender animal, such as a fish or a cougar, having the sensory organs up front could allow the animal to detect things ahead—food, danger, a mate, whatever—as immediately as possible, and shorten the reaction time to whatever’s out there. Always a good idea.
But for whatever reason, this is how humans are constructed. And so are many of the characters in science fiction. The Roswell “little green men” are shown this way, and this is the most likely reason they’re not real. Any time I see a purported visitor from outer space that looks like it’s been based on humanoid features, including most prominently the cephalization of sensory organs, but also including two arms and two legs and a large brain case, I know it’s almost certainly a fake. There’s no reason I can think of to believe that life—and I’m including intelligent life here—on other planets or worlds will be based on that principle.
Having said that, of course, I can’t rule it out either. Of all the trillions and even quadrillions of planets that must exist in all the galaxies in our universe, could there be a planet or two where evolution has taken the road to cephalization? To put it more simply, are there beings that actually look like us? Definitely possible. But considering the variations of conditions that exist on the planets we’ve detected so far in our galaxy, (and that’s an extremely tiny proportion of the total) it’s much more likely that life will be quite a bit different in appearance than anything on Earth. We may not even recognize it.
Enrico Fermi is credited with asking the question that forms the basis for “Fermi’s Paradox.” That is, where are all the aliens? Why haven’t we been visited here by aliens from another planet? There are so many stars in our galaxy, and many of those stars, even perhaps all of them, have planets orbiting around them. Surely some of those planets must have life existing on them that has developed the capability of traveling the galaxy and visiting other stars and planets. With hundreds of billions of stars and maybe ten times that in planets, where are they? Why haven’t we seen them? Why hasn’t someone landed and said, “Take me to your leader?”
I’ve seen articles recently that attempt to answer the question by postulating several hypotheses. One of the most common is, “It’s too far—they can’t get here.” That hypothesis usually falls to the argument that a sufficiently advanced civilization should be able to build and send out a ship large enough to allow space explorers to live out their lifespans and spawn ancestors as the ship sails through space. A sort of “Genesis Ship.” Any visitors to our planet could be descendants of the original spacefarers. That would take an immensely large ship, but who’s to say it couldn’t be done?
That hypothesis also falls to the argument that perhaps an advanced civilization has learned how to open a wormhole, or failing that, to use an already existing one, and travel from one section of the galaxy to another with just a short hop. Who’s to say that couldn’t be done?
Generally, we tend to argue ourselves out of almost any supposed block to long distance space travel. It can be done, we confidently assert. And, we continue, here’s how. And we launch into detailed explanations of how they could get here. So, where are they?
Let me throw out a different possibility: perhaps we have been visited here. Maybe they’ve come in droves, and they’re all around us. Maybe they came many thousands of years ago and left, muttering something to themselves about nothing here worth visiting. Perhaps they set out space buoys to warn other travelers away. “Don’t go to that blue planet. It’s worthless.” After all, we still do see UFO’s in the sky. Not all UFO’s have been identified. Some are balloons, some are government projects, some are airplanes, some are blimps, and so on, but what about the ones we can’t identify? It seems logical to me that if aliens were to visit us here, they’d want to keep their presence quiet. For whatever reason. How can you read the mind of an alien if you don’t even know whether it exists in the first place?
Any alien capable of traveling the galaxy, or through a wormhole, might also have developed the capability of masking his presence to the point that we don’t even know he’s here. In that sense, the Romulan cloaking device of Star Trek might not be so farfetched.
Here’s looking at you.