How can scientists assume aliens breath air/oxygen?

Question

Yes, we do, but on our own planet their are animals that don't need it to survive.. So, why do we only looks for planets that have signs of earth like environment when looking for life? I'd have to laugh if we skipped all the planets with stuff on it because it wasn't like earth :)

Answer 1

Planetary searches are based on signatures such as energy gradients, complex chemistry, liquids that may act as solvents, the presence of planetary atmospheres, all things we can detect at a distance. They are based on geosignatures we have on Earth because we have parameters to base the search on. The more we look and understand the farther the range can be extended. It is difficult to explore without coming from a known position.
Compare this search to the early sailors. They traveled from their known coastal areas to less known following the shore but eventually the set off into the sea only knowing the planet was round and roughly how big. They couldn't start in the middle of the ocean because they had no means. The search goes from known to unknown.

However we also have radio telescopes looking for signals. SETI looks for regular and repeating patterns of electromanetic radiation from space.

Answer 2

"Why do scientist always assume..." They don't. I have many friends who study a lot of other possibilities. However, they know that the bigger atoms, for example (like Si) have weaker bonds: the atom is bigger (the outer electrons are further from the nucleus) so that the chemical bonds will have less energy. This means that the molecules formed by these atoms will be more quickly destroyed by heat, by UV light, and so on. Maybe they could exist at lower temperature, but that means that metabolic rates would be much lower (chemical reaction rates go down by half for every drop of 20 K in the average temperature). Also, Carbon-based life "as-we-know-it" does have one advantage: it breathes in oxygen (a gas) and breathes out CO2 (also a gas) so that lungs are perfect for the job. Si based life might exist on Oxygen, but it would breath out SiO2 (a solid = sand or glass). This would require a more complicated exchange system -- add that to the slower metabolism, and you have a problem. --- A solvent is for the transport of various materials (food, proteins, building blocks, etc.), and there must be a compatibility between the solvent and the material that make up the cells (or whatever is the unit of the other lifeforms). Water and carbon-chains work well. Methane and carbon does not. That is why if you are on a world with liquid methane as your solvent (e.g., Titan), then you need to imagine something other than carbon as you chain. Then you get into the problems of less stable chains, a lesser availability of valence bonds and a greater possibility of the bonds being disrupted. Sure, life other than carbon-based-with-water-solvent is possible. But it requires conditions that are far more disadvantageous.

Answer 3

Scientists do not make assumptions about aliens. Those are made by non-scientific people who don't understand how science works.

Astronomers do sometimes look for evidence of planets orbiting suns other than our own. The purpose at this point is to refine observational technique, rather than to look for extraterrestrial life. There is only a very slim chance that we would detect life on an extrasolar planet, and we know for sure we will never contact them, because we are too far apart to ever be able to travel.

Sorry.

Answer 4

Sorry to burst your bubble, but there aren't any scientist that "believe" or otherwise about extraterrestrials. It is mostly a topic for lay people to speculate about. I am sure some scientist are among the speculators. But, I can also assure you, that no scientist, anywhere, has data files full of info on life forms beyond Earth.

Here is reality. Earth, and it's life forms are the absolute only known existing life in the Universe. All the rest is speculation, fantasy and mostly a waste of time. You might as well believe in a god.

Answer 5

The thing is, oxygen is the easier thing to deal with when considering energy production of large animals. Yes, life can survive without oxygen (anerobic bacteria and some types of animals for short periods of time), but the energy costs of living without oxygen are large.

So for our current knowledge of energy gained from metabolism... oxygen is needed for the best, most efficient means of making energy. Without it, it's what causes the burning sensation in our muscles when we work out really hard. That's because our own cells do non-oxygen fermentation, but the byproducts are somewhat toxic in large quantities (lactic acid).
The more efficient means eventually can lead to something growing larger. Wheras finding live bacteria would be nice, finding something like a fish or reptile would be even better.

Now, another reason why we look for oxygen and water is because we might want to move someplace else someday. If humanity is only on Earth, and a giant asteroid destroys Earth, no more humanity. But, if humanity is on Earth, Mars, extrasolar colonies, etc., then humanity lives on.

Answer 6

Scientists don't assume anything.

Assumptions are not scientific.

However, there are some real bio-chemical reasons why the carbon/oxygen way of life might be the only way life can go.

Chemistry seems to be the same throughout the universe.

But scientists do NOT discount other systems of bio-chemistry.

It is you making assumptions.

Answer 7

Partly because when we investigate other planets, we're not just looking for extraterrestrial life. We're looking specifically for life that might be similar enough for us to be able to recognize it as life. We're also giving special interest to Earthlike planets because someday we will have the technology to travel to them, and for obvious reasons, we wouldn't want to go anywhere we can't survive.

Answer 8

they shouldnt assume that ...there could be intelignt life forms that breath something diffrent like some weird gas..or they dont have to breath at all...complety diffrent life form...idk maybe they are looking for humanoids or they or going on the basis of chemistry and they are studying all the planets they find, i dont think they are skipping any..

Answer 9

I know right? I think we are looking for life that is like our own that we can relate to...although a lifeform that could live in an enviroment of fire or something sounds pretty cool.

Answer 10

Great question. Shows the stupidity of SETI.