Would life be able to exist or evolve without gravity? How likely would large multicellular forms of life be, on a planet with low gravity but otherwise similar conditions for evolution?
For an answer to that question, you only need to look beneath the waves of the sea - since essentially the flora and fauna there live in what could be easily described as near-zero gravity. Please Register or Log in to view the hidden image!
Ok, gravity is an evolutionary pressure, it directly influences natural selection. The out there part is that gravity is also a pressure, physically. I conjecture that life has found two ways to evolve in a gravitational environment; by staying small so gravity has less effect than other influences like surface tension, or by getting large, slowly. The second option is a lot more complicated than the first, which is why the first option has been around for a lot longer.
if gravity did not exist then there would be no suns or planets. without suns there would be no energy source in the universe. therefore no life.
Yes, but I'm assuming that there is a sun, and liquid water. The question is about how much gravity affects evolution. In the earth's gravitational field small organisms like bacteria are more or less immune to the effect of weight, they can form spores and be carried around by air currents for instance. I didn't really mean to consider if life can exist in empty space.
But the water is kept together how? Without gravity the whole universe would just be a cloud of mixed up matter, no stars or galaxies.
Oh man; water is kept together by gravity. This is already getting a bit silly. Nothing on this planet lives in zero gravity. But in water gravity has less effect--the smaller you are the less effect proportionally. We have to deal with breathing air that's compressed by gravity.
When people go into space, its common for them to feel ill for a few days because their organs are all weightless and end up floating or getting squashed in unusual ways.
Yes, drumbeat's response *was* rather silly - I don't think he understands much about gravity in general. Please Register or Log in to view the hidden image! Not only does gravity have little effect in water, it has *almost* nil effect. That's exactly why the largest creatures of this planet - whales - live in water. Their massive weight is buoyed by the water they live in.
If you have to ask. The title of the thread here is: "Life and gravity". The first assumes the presence of liquid water and the second assumes a large mass, maybe a planet, so it kind of starts with the right conditions, not empty space. Then I ask in the first post, what effect would low gravity have on the evolution of large multicellular forms of life. The "weightless" conditions in the oceans are an indirect function of gravity itself, for which animals and plants have evolved a compensating bouyancy function. Alrighty?
This: "But the water is kept together how?" Note that the OP didn't say NO gravity. So that's what made it look silly.Please Register or Log in to view the hidden image!
Sorry, I apologize - he DID say both!! I guess it's just because I went with the second since gravity IS needed in order to have any kind of sea life at all.
Hmm. I suppose I assumed a bridge too far. The phrase "without gravity" can mean being far away from any large mass (and probably any chance of life), so pedantically, I should have typed "not subject to free fall in a fluid medium, being suspended by molecular interactions and Brownian motion, and subject to bulk flow in the medium". Smoke particles come to mind. . .
Another stab: We know there are lifeforms that require only liquid water and a source of energy, and that they are found at ocean vents, inside rocks deep below the surface, and throughout the atmosphere. Microbes are the least affected directly by (the influence of) gravity. But they depend on the existence of a large enough planet around a star so that liquid water has an "environment"; otherwise I suppose you can entertain what life would be like inside drops of water orbiting a source of heat--supposedly a drop of water from the earth's ocean would sustain life for a while if it was orbiting the earth. But anyhoo, gravity was and is something that larger, heavier animals have had to deal with in order to get bigger than a microbe. So, if the earth were a smaller planet, would animals like whales be bigger or smaller? Would trees be able to grow higher, and so on? Why go to all the trouble of getting large, and so having to deal with "weight"? So you see, I'm considering that the much longer evolutionary history of microbes is because they are "willingly" constrained by gravity--one way to consider this is as a genetic constraint as well, bacteria haven't evolved the ability to get larger (except as large colonies) but retained the "successful" strategy of staying small enough to be beyond the direct effects of gravity.
No gravity would effect our body in ways that we are not equipped for. In addition, without gravity, we would not have an atmosphere, as there would be nothing holding where it is.
