The Connection Between Color and the Existence of Life
mitchkirby.com
mitchkirby.com
Nowadays people seem to think that life must be common throughout the universe, given the number of stars and planets, and etc. It seems to me that the opposite could be the case, that life is extraordinarily rare.
As far as I know, we don't really know the likelihood of life emerging in our own planetary conditions: given a billion earth like planets with roughly equivalent atomic makeup, distance from sun, etc (assuming these are common, which fact we don't know either), how often will life emerge? We can guess and say "all the time!", but it could be an infinitesimal small amount.
Even moreso for different conditions than earth. Commonly people say "given a liquid like water, and certain other factors", but we don't know if life will emerge in any other conditions except our own. We have no proof whatsoever.
We also don't know how likely it is that life reaches our own point, of being capable of pondering life around other stars, or capable of imagining travel to them. There may be many, many extremely low probability events that must occur, in the billions of years between life's genesis and our own existence.
In fact, there's a good likelihood that our own dreams of interstellar travel will end in our extinction prior to our ever making the attempt. If that happens, it will prove my point.
To me this general optimism towards life on other planets is vaguely anthrocentric, like the belief that god is an old man, or that the universe revolves around the sun.
As such it results in a tendency to underestimate our own fragility, and to pay appropriate attention to the challenges of maintaining our own continued existence on earth.
Microbial life in no way entails higher life. It's only by the insanely chance event of the eurkaryotic cell emerging that sophisticated multicellular life became possible on earth. Even if life is common in the universe, sophisticated multicellular life is extremely rare.
The selective pressures on bacterial life favors small size and rapid reproduction, jettisoning any unnecessary genetic material.
Mitochondrial ancestors relieved those pressures in a couple ways. Once the eukaryotic cell developed, multicellularity has evolved several times. All the cool things (multicellularity, eyes, flight) have evolved independently a bunch of times, and the eukaryote has happened only fucking once. Here's a longer explanation:
http://ronbarak.tumblr.com/post/25996121029/life-is-it-inevi...
http://www.technologyreview.com/view/513781/moores-law-and-t...
For example, the assumption that we are the most intelligent creature to have yet emerged from the evolutionary process is most certainly a function of how one measures "intelligence". it might be the case that one can measure intelligence through the fossil record, but i would be interested to see a study of the selective pressure that produces advanced and intricate central nervous systems, and to understand how this could be said to increase in overall terms. i think it might not be the case, although it might, given certain selective conditions. i'm not sure we know what those are.
To me, the definition of intelligence is to produce the most appropriate response given the circumstances. So a plant that turns its leaves towards the sun is displaying intelligence. are plants more intelligent than we? by some measures yes - being able to respond to direct sunlight by producing energy is certainly appropriate in some circumstances - plants have solved a problem that we cannot, and therefore are more intelligent than we. (and i know folks will reject the idea that photosynthesis is a form of intelligence, but in my opinion that's anthro-centrism!)
is pondering the orbits of distant planets the most intelligent activity to have been performed by any organism ever? is building mega-cities and particle colliders? We don't know yet. it could be extremely inappropriate, because it could be next to impossible to travel between stars, given the reality of our existence. we could be leading ourselves to our own extinction, by dramatically altering our own planetary biosphere and chemistry, in pursuit of lofty visions such as interstellar travel. That's not so intelligent.
Another relevant point is that we don't have very much of the fossil record. i read somewhere that we had like 4% or so, although i am not exactly sure how one estimates that percentage. But assuming so, somewhere in that 96% there could be critters more freakishly intelligent that we.
suppose that in the 4-5 billion years of life on earth, of which our own record of relatively extreme intelligence is only 2,000 years old, there could in fact have been civilizations created by social creatures with as much or more intelligence than we. There could have been cities, perhaps in the millions and millions of years when dinosaurs were common. Granted this goes against commonly held assumptions, but it is certainly not impossible.
Keep in mind, a mere 150 years ago, we had a global civilization that could have vanished easily without a trace in 20,000 years, let alone 1 million. do we think of ourselves as incredibly more intelligent than our great grandparents, or theirs, or than people living 300 years ago? Better informed on certain topics for sure, but more intelligent? We are more like plants now, in that our intelligence is specialized to certain techno-powerful purposed, of which the intelligence relative to our external conditions is still yet to be decided. We might say that our ancestors were more intelligent for avoiding the kinds of environmental and social disasters that we have engendered.
Anyway, were we to go extinct now, we assume that future intelligent creatures would find remains of our great civilization. But we don't know how long these would last. There's some luck involved. it's possible that the hominid layer could degrade quickly!
On the other hand, if common assumption is correct and we really are the only potentially starfaring organisms to have evolved yet, then that argues my original point that life, and life worth communicating with, could be exceedingly rare. in 4 billion years (about 1/4th to 1/3rd of the age of the universe) life sufficiently intelligent to travel the stars has only emerged once. Those odds seem low, but they might be freakishly, abysmally low as well. Had it emerged twice, and we had some evidnce, odds would be better, but once! That's hard to quantify, especially as the longer life persists, the more likely it is to be wiped out by some kind of extinction event.
One other example to support your point - Apparently life is protected on Earth by having a Jupiter around to suck up many of the asteroids.
http://www.space.com/17793-jupiter-giant-windy-gas-ball-prot...
This prevents extinction events from being much more common.
Who knows how else we're unique?
1) Life appeared on Earth early pretty much as soon as conditions arose that would support it (as soon as the planet cooled enough). So that would point to life being "easy" to form.
2) Biogenesis only happened once (as far as we can tell), so that would point to [a] life being hard to get started, or [b] life was seeded from space (panspermia).
3) It took a really long time for multi-cellular life to appear. So this step appears to be very hard / rare.
4) It took a really long time for nerves ("thinking" cells) to form (and likely only happened once).
5) So far, no sign of microbial life on other planets in the Solar system, so may rule out panspermia from point (1) above.
That's quite a stretch.
> Biogenesis only happened once (as far as we can tell), so that would point to [a] life being hard to get started, or [b] life was seeded from space (panspermia).
Neither one of those conclusions is justified; the first (as I've said elsewhere in the thread) is unjustified because the creation of life changed conditions on the planet -- and its quite possible that it changed them in a way which made it much less likely for biogenesis to occur again.
The second is just a completely unconnected conclusion to the premise that supposedly supports it.
> It took a really long time for multi-cellular life to appear. So this step appears to be very hard / unlikely.
Multicellular life appears to have emerged independently at least several dozen times, so it doesn't seem to be that hard/unlikely (and given the incomplete nature of the fossil record, its possible that it had brief emergences -- possibly early than the known ones -- that didn't last and haven't been seen.) And there has been lots of reversion from multicelluarity to unicellularity that we know of. So, maybe, multicellularity alone doesn't offer much clear a major benefit, so while its not that hard to emerge, there's no real pressure to keep it, until it coincides with the development of some other feature.
>That's quite a stretch.
What is a stretch? That life formed as soon as conditions supported it, or that it may indicate that life is easy to form? The earth formed 4.55 billion years ago, the moon formed 4.5 billion years ago, and 4 billion years ago was the end of the late heavy bombardment, and the first formation of life.
I do agree that changes in conditions could prevent a second biogenesis event, but there seems to be enough time with the initial conditions that it "should" have happened more than once. But that is just my initial impression from the simplified versions of geologic timescales that are presented in various pop sci media.
Biogenesis says that Life creates life or, (I'm paraphrasing) organic matter creates more organic matter.
The disproval of Vitalism shows that non-organic matter can create organic matter.
Therefore Biogenesis can occur from inorganic matter.
So a seed shouldn't be needed. Biogenesis could happen anytime there is organic matter in the right conditions, is that right?
If life could easily form, one would think it would do so many times here on earth.
Not really. It might just mean that the emergence of life itself created conditions no longer favorable for the emergence of life.
He may have just killed life on other planets. Or at least a fair proportion of it, if you have to have a star that outputs mainly in the water-transparent, ideal-for-photosynthesis spectrum.
Of course these evolutionary things seem to somehow fix themselves. Some other chemical might be a more suited to light from a different star, or something in the water may change its spectrum. Or simply a brighter/dimmer star might jiggle things.
Not so much. Here's a different article posted to HN recently: "Can life exist on a planet without a star?", http://aeon.co/magazine/science/can-life-exist-on-a-planet-w...
This is what makes me excited about Titan. If life exists there, then it will be based on processes and chemicals not on Earth.
If an alien planet with liquid water had a different class of star the light from it may not emit the same amount of the frequency of light to make through water compared to earth but to the life on that planet it would be normal.
I think water is the key not so much the sun since life would need liquid water to exist and the light needed whether abundant or not could only be in the frequency alien eyes could use the best which would be the same as life on earth.
The biggest factor in life being different on an alien plant I think would be due to gravity and atmosphere; pressure and oxygen level.
However, that visible spectrum of stars corresponds to a band where atoms can capture/emit photons does seem like a coincidence to me. That's a cosmogonical coincidence however.
That statement isn't just about the particular chlorophyll molecules that evolved on earth.
What do you guys think of this idea?
Edit: I meant to post this as a response to tehchromic's comment: https://news.ycombinator.com/item?id=9493736 (sorry)