I am in the process of compiling research for a Sci fi book I am working on. I wanted to explore the notion that for a planet to sustain life similar to Earths it must usually orbit and rotate at a certain frequency at a certain distance from it's star. To maintain water in liquid and steam state requires certain temperatures thus the distance form the star is very important. This of course is relatively easy to propose and is possibly even plausable however what I wanted to explore is what would happen if the Earth rotated once every 48 hours instead of 24 hours, and had only 180 odd days to a year? [ maintaining it's current distance from the sun] What would be the climatic conditions do you think? Would those condition sustain a similar bio diversity? Would we just see an extreme version of what we have, given approximately 24 hours of darkness and 24 hours light? Or would there be less symmetry than first thought due to differing radiation and absorbtion rates of temperature? Are there any other questions worth asking? Care to speculate?
Sure. In my sleep deprived state, I would say this. (Zzzzzzzz) The temperature difference between the sunlit and dark side would be much more extreme dur to the longer light/dark times. This would cause more rapid air exchange across the terminator and extreme weather patterns would result. I would expect average temperatures in the daylight portion to be 10 to 50 degrees warmer than they are now and be just as much lower on the night side. This would probably make for life adaptations quite different from what we see now.
do you think the wind velocities would be so severe that unprotected surface exposure would be impossible?
Do you think that it is just coincidence that the earth with all it's liquid water dependent life rotates once for every single degree of orbit around our sun? The question: Is life dependent on a rotation every degree of orbit? Are the rotation and orbit velocities, including distance from the sun essential to support life in any meaningful fashion [ beyond bacteria etc] Do you think that the relationship of a circle, pi, radius and rotation degrees of 360 are in any way [possibly] meaningful to this question about sustainable life?
if your thinking about alien life, try not to let your mind only imagine conditions necessary for life on earth.... there are chemical properties that we know of for sure, but there are extromphiles that live in conditions on earth once thought impossible to sustain any type of life. Later T
QQ, The earth turned much faster in the past. The current rate is a coincidence and will evaporate, just as is the fact that the moon subtends the same angle in the sky as the sun (allowing perfect solar eclipses). They are even sort of related. The earth rotated faster and the moon was much closer. Over time the tidal drag between the earth and moon causes the earth to slow, and the moon to slowly spiral away. 100,000 years from now, the moon will appear quite a bit smaller, and the earths day will have lengthened.
Thanks SL and others, Just to pursue the point a little further; 1] Could I propose the notion that Human life only existed or evolved on this planet during a period where the orbit of planet and moon where "similar" to what we have today? 2] It could be possibly true that the Earths life conditions will dramatically change as the planet changes it's orbit and rotation rates, but would it be sufficient to support human life assuming the same agricultural needs? 3] Do you believe it is non-critical to human terra existence that the planet maintain it's current or very similar orbital and rotational timinigs? 4] Thus would this extend to the feasability of life on other planets around other stars that share a similar orbit, rotational timing?
QQ, The orbit of the earth is stable. So that's not a problem. The exact planet-sun distance, rotation rate, and whether there's a large moon or not could all affect the style of life. (It was thought at one time that a large moon was required to help 'strip' away excess atmosphere otherwise we would have ended up like Venus. This is largely discredited now.) I think that the parameters we have had on earth may be very critical for the development of life beyond the single-cell level. Having said that, we have life here that thrives without oxygen, at temperatures from -90F to + 200F, and can live off of sulfur or other chemicals (photosynthesis is not the only way). The only real limit may be the temperature at which water and carbon molecules can function efficiently. And that brings up life based on other substances than carbon...
I suppose it all comes down to the impossible to answer question of how important is the constant liquid nature of water to the existence of complex forms of life such as sentient self articulated life [humaniod] In situations where water is not able to be sustained as a liquid would complex and diverse life forms be possible? I guess I am stuck on the question of how important liquid water and it's maintianing it's liquid state is to the diversity of life. If temperature ranges meant that waters liquid state could not be maintained I question whether complex humanoid life forms would evolve..... How important do you think keeping water at a temperature that maintains it's liquid state is? A 48 hour day would I think mean that water would be frozen through the night and steam during the day only allowing a liquid state of short duration.... and with out sophisticated tempterature conditioning would life survive through either fridgid or steam states....
Until we find a lifeform that uses liquid methane or something as it's solvent of choice, water is all there is. Ther is no reason to expect that life can form without it. It has properties unlike any other liquid molecule. Water is amazing. And liquid state water is essential otherwise the molecules of life cannot move (heck, NO molecules can move).
Maybe not. The thermal capacity of the atmosphere might dampen temperature fluctuations enough to maintain liquid water throughout the day/night cycle. (I think I guessed at a 10 to 50 degree peak difference. That's not too bad.)
I agree if the temp range was only as speculated liquid water would exist in various protected areas....Life may be severely limited in quantity but I can't see why it wouldn't succeed. An Idea I working on is an alien race that evolved in large networks of air filled caves under the surface close to thermal vents and liquid water...I'll post a layout soon....[the surface temps being say from -40c to +110c or something like that..due to slow rotations.]
If you look outside your window and see how amazingly fantastic nature and evolution is, it appears quite simple that the earth, and every living thing on it, would/will adapt to a change in rotation and the moon's distance (tides etc) within 100,000 years. And it is very, very, very chavinistic of life as we know it to suppose that the distance of the moon from the earth and all rotational and orbital periods associated thereof are absolutely necessary for humanoid life. Just remember how we keep on demoting ourselves from the poistion of centricity (earth was center of the universe, then the sun, then the galaxy, now we know there practically is no center). In other words, stop believing that the earth has JUST THE RIGHT conditions for life. It has just the right conditions for life as we know it, nothing else. Thats why science fiction is so alluring: As far as we can tell, despite laws of chemistry and physics that govern molecular reactions, anything is possible. And there are probably things we believe can't happpen and do.
Good point and I thoroughly agree with you....I personally don't believe that teh scope of our own experience should limit our imaginations or the possibility that reality exists out side even our imaginations. The policy being that we are always in some form of box that we place ourselves in ...always...no matter how imaginative we can be......
Anthropic Principle or goldielocks principle anyone? Please Register or Log in to view the hidden image! If you start thinking like this then any SF story that does not have a planet with the "just right" conditions is going to look like fantasy. I am sure that any good SF writer could come up with some scientific explanation for life developing on worlds with other parameters than Earth. I agree with Tristan that if life does appear on any planet it will adapt and evolve to whatever conditions are available to it. OK so there are probably some minimum requirements such as liquid water but life is tenacious. Further than that I would argue that once life gets a hold it will evolve along with the environment to provide a more stable system than you might expect from just looking at the distance from the sun and rotational speed etc. How about trying some calculations with the Earth's parameters, but without the Earth's current atmosphere and I am sure someone would come up with an argument against life on Earth. It is only because we have life on earth that the climate is sufficiently stable to support life - see Gaia theory (don't scoff, it is good science when not mixed with new age mysticism :m: Please Register or Log in to view the hidden image! ).
halucigenia, I agree 100% with your post. And I pick... goldielocks! (The Anthropic Principle never did much for me as an argument). Life began in a methane atmosphere and created oxygen as a waste gas. However, as oxygen reactions have a much higher energy, things adapted to use it and out-competed their lower energy couisins. Now, the biosphere is a largely self regulating system with a huge ability to damp out and compensate for external chaotic influences.
The length of Earth's day increases by one hour every onehundred and eighty million years, according to current measurements. This is caused by the tidal friction imposed by the sea and by the atmosphere. So to have the day 48 hours long, you'd be going 24 x 180m years into the future, or about 4000 million years from now. By this time the sun will be in its red giant stage, enormously expanded and will have absorbed Mercury and probably Venus as well. The Earth, Mars and the outer planets will have retreated from the Sun, because as the Sun's rotation-rate slows down, the planets withdraw as they speed up in their orbits (according to the law of the conservation of angular momentum). This says that as a central body slows down, its rotational energy is not lost but transferred to the bodies which are orbiting around it. So Earth should still be in existence 4000+ million years from now, but at roughly the distance of Mars or the asteroid belts (which should make life entertaining for the species which exist at that time). Please Register or Log in to view the hidden image! As for the conditions, given that the Earth is going to be a giant barbacue plate even at Mars-distance, I suggest that only thermophilic bacteria/plants/animals will be living there. Any civilisations will probably (for their own protection, obviously) be subterranean. Most species which have the ability to burrow underground will do so. I'd also say that the heat of the sun would have evaporated the oceans, so that Earth will be a supertropical fog-bound landscape, with jungles covering the continents and continental shelves, and salt-swamps in the former oceanic basins.
and what do you estimate would be the conditions of the Earths inner heating,,,core and mantle after 4000m years?
As you'll know, the Earth's own supply of heat is generated from the decay of radioactive elements in the mantle and in the region just below the crust, (known as the aesthenosphere). By a bout 1000 million years from now, these radioactive materials will have been all used up, i.e. there will be no more radioactive heat produced. As a result, almost all the tectonic activity (volcanism, earthquakes, continental drift) will come to a halt, and the Earth's crust will 'freeze' in the position it then occupies. The continents will begin to wear down, and this erosion will only cease when the oceans are evaporated when the sun begins to warm up. Because hydrogen is being converted into helium by the fusion-reaction of the sun (at the rate of 4m/tons/second, FYI) the Sun is gradually heating up, at the rate of 1% increase in heat per 10m years. So by 4000 million years (4320 million to be accurate) the Sun will be 432% hotter than it is presently. This extra heat will cause the evaporation of the seas, as I've said--the other factor is the tidal effect of the Moon, which will still be disrupting the crust of the Earth as it does now, and causing volcanism and earthquakes, though on a much lesser scale than presently.
so the ambient temperature of our subterranean caves is not going to be pleasant no matter what..... when the coldest part of the planet will be at it's core.....
