The universe is full of stars. We are not so sure about habitable planets though. The habitable zone is defined as the distance from the parent star where water flows freely as a liquid. Saying that, over 300 planets have been found so far. Unfortunately from earth we just can’t pick up habitable planets but only the larger ones.
The Kepler telescope has been launched and will be able to pick up earth like planets. It is just picking up data but it
will take years to observe and confirm the observations. One observation of a habitable planet would be excellent as this would mean that there are roughly one habitable zone planets every 10 stars. But 50 planets are possible meaning there would be one planet per star.
But what if the habitable planets are just a luxury and are not the only ones needed for alien life? Perhaps one day we will be able to genetically alter our bodies to live in much harsher environments and therefore open up a whole new load of planets and options.
If we look at what could be out there then should we be just looking at habitable zone planets? Well, Kepler is doing a good job but it can’t scan every single star so looking for habitable zone planets is a good start. But what could be living on all those other planets, not to mention the ones in our solar system? Do we have some sort of life on our doorstep?
What is life? Well, it’s not that guy down the pub on his 20th beer throwing up all over the floor. It is something like the following-
- Organized -Life is made of atoms and molecules that are organized into cells. The cells in an organism can be either uniform or specialized for various functions. The cells can be further organized into tissues, organs and systems.
- Homeostatic – Living things carry out functions that keep them in a constant, relatively unchanging state called homeostasis. For example, your body has systems that keep your body temperature constant — you shiver if you’re cold, sweat if you’re hot.
- Reproduces – Living things make copies of themselves, either exact copies (clones) by asexual reproduction or similar copies by sexual reproduction.
- Grows/develops – Living things grow and develop from smaller and/or simpler forms. For example, a human begins life as a fertilized egg, developing into an embryo, fetus and then a baby. The baby subsequently grows into a toddler, adolescent and adult.
- Takes in energy from the environment – Staying in a relatively constant, organized state violates the second law of thermodynamics, which states that the degree of disorder (entropy) of all objects increases. For a living organism to maintain organization, it must take in, process and expend energy. The way humans and other animals do this is by eating food and extracting energy from it.
- Responds to stimuli – Living things respond to changes in their environment. For example, if a stimulus causes you pain, you respond by moving away from that object. If you place a plant near a well-lit window, the branches or shoots grow toward the light (phototropism). For protection, some animals change color to blend in with their surroundings (camouflage).
- Adapted to its environment – The characteristics of a living thing tend to be suited for its environment. For example, the fins of a dolphin are flat and adapted for swimming. The wing of a bat has the same basic structure as the bones in a dolphin’s fin, but has a thin membrane that enables flight.
These definitions of life are just really a shot in the dark. Life could be so weird and incomprehensible that trying to find a definition sends us in the wrong direction. Perhaps we should just look at life with our eyes, ears and whatever else we can find wide open and also most importantly an open mind.
So would intelligent extraterrestrial life look anything like us? Probably it wouldn’t, although there’s a mechanism known to biologists as convergent evolution that argues for at least a bit of a resemblance. Convergent evolution is the idea that as nature works its way down a Darwinian path, selection favors good designs that enhance survivability.
Convergent evolution favours science fiction programmes as they feature human like aliens for convenience. There are other aliens other than humanlike but they don’t seem to be main characters. I suppose putting the make up on a pink and red jellyfish isn’t that easy compared to a biped.
But it’s a bit extreme to maintain that we are the best design, and therefore convergent evolution will ensure that an intelligent alien looks like your mother-in-law. After all, an extra set of arms might be useful, as would an eye in the back of our heads (for the children) A double spine might allow faster and easier walking, and a few extra digits on each hand could make for better tool use or piano playing. The bottom line is that any biological creature we find that’s at least as clever as we are, might have some features in common with us (two eyes, instead of one, for instance). But there’s little reason to think our own design is so wonderfully optimal that all thinking beings will have converged on it.
Starting at the very small, viruses may or may not be classed as life but if found on a different planet would be a start. Of course if it extended a hand and shook yours then that might be a clue. Slime and microbes would also be a worthy find as it would give us hope for more life elsewhere.
As life evolves up the evolutionary chain in my opinion it could divert anywhere along the chain. If fish had had a great time in the sea they may have never bothered coming out onto the land and developed intelligence in the sea. Imagine spacecraft that had to be full of water to support them instead of oxygen.
The obvious one is the dinosaurs. If they had not become extinct we would not be here now. Had the dinosaurs survived and become intelligent they would eventually have needed to stand upright to balance their heavy head. A shoulder structure would have evolved to allow the “dinosauroid” to throw objects It would have evolved into a large-brained, reptilian biped with enormous eyes, three-fingered hands, an absence of external genitalia (typical of reptiles), and a navel (since a placenta is found in some modern reptiles and may have been needed to enable the birth of young with big brain cases). If dinosaurs had prevailed on a distant planet and visited us how would we react?
So what form could life take on distant planets? What would form on planets other than planets in the habitable zone?
Life could be evolved out of silicon, boron, Carbon dioxide, phosphorus or plasma or another chemical foundation other than carbon.
Water could be replaced as a solvent by liquid ammonia.This could mean that life could evolve on gas giants and some of their Moons. Creatures like giant gas-bags that could move by pumping out helium and could be up to a kilometre long could exist.
Spores could survive in space and be spread from one planetary system to another by means of radiation pressure.This would mean that life would form on certain planets but the spore would have to had grown initially on a friendly planet and then spread.
An announcement was made in September 2003 that physicists had succeeded in creating blobs of plasma that could grow, replicate, and communicate, therefore having most of the properties of cells. Lacking inherited material they cannot be described as alive, but the researchers believe these curious spheres may offer a radical new explanation for how life began.
The possibility that low-mass brown dwarfs might contain liquid water suggests that they might also be capable of supporting some kind of life. Organisms might evolve to be able to exploit the deep infrared radiation given off both for photosynthesis and perception, perception through eyes equipped for infrared vision or thermal sensors like those of snakes. One problem would be the high gravity – 100 times stronger than on Earth. However, considering the ability of ants, for example, to lift around 50 times their own body weight, it is not out of the question that life could evolve under gravitationally extreme conditions. Other obstacles to life on brown dwarfs would include the lack of available surfaces for chemical reactions, suitable temperatures, and the lack of heavy elements such as potassium, calcium, and iron, which are necessary for living processes with which we are familiar.
life might exist on a neutron star’s solid surface. The creatures could be made out of submicroscopic particles and made of tightly packed nuclei, rather than ordinary atoms, bound together as “nuclear molecules”. Whether such bizarre molecules could exist and combine in ways complex enough to give rise to life is not known. However, if neutron star creatures did exist they would live very rapidly.
I have mostly avoided the traditional speculations on life to hopefully show that life has the possibility of evolving almost anywhere. I could write forever on the possibilities of alien life and I believe that is how much alien life there actually is- totally infinite. Finding it is a different matter though.