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At the present time it looks as if there is no other life in the Universe other than here on Earth . If this is true then why didn't it occur anywhere else ? Is it possible for something to happen only once ? Hundreds of Billions of other Planets have formed so whatever happened here why wouldn't it have happened again elsewhere ? It is very , very strange indeed .

Peter U
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  • Although this is an interesting question, it has few problems with it. 1, I think it's off topic (too broad / unclear what you're asking - in biology topic), and suits astronomy better. 2, there's no proof that life does not exist in some other from somewhere else (as far as I know Mars has signs that it was habitable to some extent in the past - for microbes at least) . – Nandor Poka Apr 19 '15 at 21:04
  • @poka.nandor Most often I post my questions on astronomy but I thought this fitted biology more. I know that there is no proof either way but recently I read that Scientists were scanning millions of Galaxies and could see no indication of life anywhere else. We have to keep looking and to keep an open mind but until we find some evidence it will look like we are alone in the Universe. So what I am asking is how could it , life , occur only on one world out of trillions of worlds and how strange this is if this is actually the case ? – Peter U Apr 19 '15 at 21:27
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    I'M not even sure that with current technology we could tell if Earth has life, even within from our solar system. – Nandor Poka Apr 19 '15 at 21:52
  • @PeterU do you have a reliable (preferably peer-reviewed) reference to back up your statement that "Scientists were scanning millions of Galaxies and could see no indication of life anywhere else"? What were their readouts? $CO_2$? The color green? This completely contradicts the mounting evidence of large numbers of rocky, "Earth-like" planets withing a sun's habitable zone. – MattDMo Apr 19 '15 at 22:01
  • @poka.nandor yes, you can, with listening to radio waves, for one thing. See here for one description of how planets are evaluated for "life as we know it". – MattDMo Apr 19 '15 at 22:06
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    Emphasis on life as we know it... what about planets that dont have civ with radio tech...like earth did not have up until like a hundred years..i know that there are molecules you can look for that might indicate presence of life but detecting those fom millions of kms /light years... – Nandor Poka Apr 19 '15 at 22:27
  • This project tried to look for advanced alien civilizations by looking for their waste heat from other galaxies. The recent news is that they haven't found anything, but this project would probably only detect civilizations that had spread across entire galaxies and used a lot of energy. This doesn't say anything about the presence or absence of biological life on other planets. As far a good way to detect life, molecular Oxygen gas would probably be good. – user137 Apr 20 '15 at 14:38

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Issues with the post

I agree that the question is too broad. It is not the only issue, it is also primarily opinion-based (see below for explanations). The post is also somehow unclear (see below for explanations). But here is some kind of an answer that may help you.

If you google your question you will get tons and tons of hits. There is a whole lot of videos on youtube that address this question. You may want to have a look at those and come on StackExchange to ask a more accurate question because for the moment the question is too broad.

As a first short answer to the questions...

At the present time it looks as if there is no other life in the Universe other than here on Earth

It sounds wrong (as a consequence your question would be primarily opinion based). We haven't found life. This doesn't mean that life doesn't exist elsewhere. Actually most people think that life exist elsewhere. Part of the issue behind this question is the definition of life. Often, people refers to Drake equation (you might want to read about it) which gives you the number of planets where life should exist. However, Drake equation is a speculation that has no solid grounds. It is actually pretty complicated (or impossible because we need to assume things about what the original conditions are) to calculate a probability that life occurs on a given planet. While it sounds pretty intuitive to many people (me, including) that life should exist somewhere else, there is really not much certainty.

Is it possible for something to happen only once?

Well....yes, the death of Napoleon occurred only once.... I am not quite sure what you mean with this question, it is unclear.

Remi.b
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  • b What I meant with the question is, if it was possible for life to form on this Planet then how could it be that it did not happen again elsewhere ? Since life came about here that shows that it is not an impossible event and yet so far there is no evidence that it ever happened again. Is this not strange ? Maybe we might never be able to find the answer and also we don't know what could have happened in the past, or what will happen again in the future, with regards to life evolving on a Planet. – Peter U Apr 20 '15 at 04:50
  • Take some time to read stuff on the subject, I cannot make a whole overview of the field, your question is too broad. Your comment has been partially answered above but I can't make much more for you. Really, just take some time to read or watch videos on the subject, there are tons of ressources on the question. You should end up understanding the issues related 1) to the definition of life, 2) to the easiness of detecting life (we haven't sent robots all over the universe yet!) and 3) to how complicated (or impossible) it is to calculate any probability of such thing to occur. – Remi.b Apr 20 '15 at 05:09
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    No need to down vote this answer, as there is no other practical method to answer this type of question. Another option is to close the question immediately with out trying to answer it. +1 for the effort put towards answering it although its difficult to answer. – Jayachandran Apr 20 '15 at 06:05
  • @PeterU: May be there are millions of planets swirling with life or may be not. But so far we cant judge whether there is life exists outside Earth. May be life is not such a big deal as we think it is. Scientific and technological knowledge are developing quite faster and we can believe that this will one day guide us to some farther planet were life is going on or some body else will find us in this remote corner. All we have to do is to patiently wait for it. (cont...) – Jayachandran Apr 20 '15 at 06:24
  • Most of our intelligent ancestors were unaware of many scientific principles and yet now we idiots know much more than them. Many more years later may be our grand grand grand sons may worry that their grand fathers(us) were unaware of the fact that we are living in a Universe full of life. May be this comment doesn't satisfy your urge but all I can offer is this. :) – Jayachandran Apr 20 '15 at 06:24
  • @Jay , Yes, I understand what you are saying. At the present time there is no way of knowing but perhaps in the future we may know . I was just stating that it would seem to be more logical if life exists elsewhere as well as here. If it turned out that we are alone it would seem very strange somehow ? – Peter U Apr 20 '15 at 19:04
  • Yes, it would "somehow" seems strange indeed. But really, you will easily find all information you need if you just google your questions. You will have an idea of what are the difficulties in estimating the number of independent origin of life and on the likelihood of actually finding life given that it exists somewhere. – Remi.b Apr 20 '15 at 19:08
  • @PeterU: Considering the vastness of Universe, we will never find out we are alone even if we are. We will be in constant search for it. If we found out we are not alone our plans for future will still be to found out more. Life is just like that, It will never let us RIP. – Jayachandran Apr 22 '15 at 05:33