All the good arguments have already been taken, so I'm left with a stupid one. Yes, life outside Earth exists because there are astronauts. Sorry...
But seriously, if life developed here, it should do so on other suitable planets as well. It took less than a billion years for life to form on Earth, and the universe is around for much longer. So the chances are high that extraterrestrial life exists.
We live in a universe with tons and tons of stars, and around those stars could be a lot of planets. I know my numbering terms aren't very good here, but the universe is huge and to me it would seem very unlikely that we are the only living thing in this entire universe.
On my biology classes in Portugal I learned a lot about this topic, the dimension of the universe is unknown but we do know that there are millions of galaxies fill with star planets and other cosmic material.
As I said before there are great odds of existing life outside Earth, like MattyB said, it is thought that life came on a meteor from space witch is a very plausible theory.
Actually scientists found a planet with similar properties to earth, it is called Kepler-22B and there is a chance of this planet to have life because it's similar to ours.
If we already found a planet like ours the odds of having a lot more is big because the universe is so vast.
Thanks, I hope scientists make some breakthrough in our era
1) Statistically, the chances of life existing are slim. However, life does exist. Which means there is a chance life exists, like it does on earth.
2) The size of the universe is unimaginable. In fact, we do not know the size of it, and probably never will. This shows that, if the universe is huge, which it is, there must be millions of planets out there, each with the possibility of life forming on it.
3) The requirements for life can vary a lot. What if an alien creature requires methane, rather than water, and breathes nitrogen? Could it live on a planet where the temperatures are right for both chemicals to exist in the correct states? Yes. On our planet, trees are capable of breathing both carbon dioxide and oxygen, and some bacteria live in volcanoes. How can we limit ourselves to planets like our own, if the possibility of life existing on planets unlike our own, is there?
4) If one theory is true, then surely there must be life out there. It is thought, by some scientists, that life was brought here aboard a meteor, perhaps in the form of amino acids or other required chemicals. This, surely, means that other planets and space objects will have life on them. Where did this meteor come from?
The fact that you could even consider that Earth is the only planet that has ever or will ever house life is ridiculous. The sheer fact that the Universe is incomprehensibly huge means that some form of life must exist or has existed elsewhere - whether Micro organisms or full Civilizations, it doesn't matter. It's ridiculous to believe that the whole Universe is for us, or that we're alone, considering how massive the Universe is.
When Mars rovers make analysis, one found a bacteria. Not a Martian, but a human Escherichia Coli (yes, some stupid didn't wash his hands after...) . So now, there is life form oustide Earth. Just hope that future Mars astronauts will have enough toilet paper...
In case of other solars systems, known primitives life forms need amine pre-acid that are contained in meteorites and comets iced core. When a meteor crash into a planet's ocean, molecules are released and a life form could appears, especially when mica matter and sunlight are available.
Either you believe in God or you accept that the universe is infinite, with an infinite amount of space and infinite number of planets making the probabilities certain that there is life elsewhere. I guess the question I'm less sure about is whether or not humans will meet life from outside the Earth.
There would be no life outside Earth. It makes sense that life would only exist on one special speck of the universe.
If there are copies of us on other parts of the universe, it would be hard to track them down, since they would have left at the same time you left.