my fish might be geniuses.
UFOs may exist since the universe is so huge. If they manage 2 reach earth then they r higly advncd dan us. Nw fr lightyear problm jst check out wormholes. Wormholes connect 2 points in space through the shortest distance in hyperspace. So 400 lightyears maybe travelld in much short time. Aliens may possess anti-matter technology whch works efficiently and cn hold wormholes open. Ths migt sound lyk sci fi bt fr al we knw they could be thousand yr ahead of us
They may not need food and conditions similar to us. For all we know they could alter their genetic composition for becoming somethng else frm carbon basd lyf forms lyk us. YIKES! Borg!
looks like someone has been reading too much star trek here.
1. wormholes have severe matter/energy flux. good luck trying to make it through in one piece.
2. wormholes can connect ANY 2 points. do you want to go into a wh and come out right next to a supernova or a black hole?
3. we too posess anti-matter tech, but i fail to see how that will keep a wh 'open'. even the bajoran wormhole does not require an anti-matter tech to keep open (is another matter that sisko has to sacrifice quark's monthly profit to appease the wormhole creatures)
4. they may or may not need similar life support. i strongly prefer the former. i think that 'life' has a basic template. carbon based organisms can only evolve in a few restricted directions. this is the reason why fish-aliens or bird-aliens cannot exist. they couldnt make and hold tools woth their appendages!!
same with quadrupeds, no hands to hold tools. so unless the aliens are psychic, we can safely assume that the aliens will have a pair of "arms", "legs", and at least something resembling a head.
5. i dont think anything can change their basic composition just like that.
do you know why is arsenic poisonous? it is very similar chemically to phosphorous, which is an essesntial compound in our DNA. it is so similar that it replaces phosphorous in all the essential sites. hence, the RNA and ribosomes cannot duplicate the pattern, and everything halts in the cell, and it dies. when enough cells die, the body dies too.
good luck changing the 'basic structure' of someone without incredibly advanced nano-bots, or genetically tailored viruses.