Sentient, technological beings exist only on earth

What I do contend is that there has been more than sufficient time for someone else (carbon based or not) to do so, many times over on many different planets. Why haven’t they?There are millions of possibilities why. First of all, humans...From my contention it is clear I am not speaking of humans so I need not respond to my opponents rebuttal. I shall, however expand on my contention. Life has existed on the 4 billion year old earth for ca. 3 billion years. Planets capable of harbouring our form of life (including those circling the older stars in our own galaxy) have existed for ca. 10 billion years. From the human example, the time from first life to us was 3 billion years. So, for 6 billion years even before earth existed planets were capable of producing life. They may have done so, but none produced sentient life or we would know about it.Cost is not a valid argument. A $100, 000 colour TV camera of 1965 is $100 todayMy opponent is trying to draw parallels between space exploration and something as small as a TV. One of the major reasons NASA was shut down was because of the ridiculous cost of sending a man into space.First, the underlined quote is a simple restatement of my opponents earlier comments about cost and therefore not a rebuttal. Second, my point was to show that expensive technologies always become cheaper, simpler and better with time. Size doesn't matter, and besides, my second example of the human genome project was a huge, decade long undertaking.Travel time too, is inconsequential. Feasible plans for interstellar travel are already in existence. A solar sail capable at achieving a respectable percentage of lights speed is actually possible today.My opponent failed to provide a source for this information and has also lied to you.http://www.niac.usra.edu...;All of my opponents rebuttals to the solar sail example are answered in the above document.created and tested by NASA, which has been shut downhttp://www.nasa.gov...;For ongoing research AND implementation see above.We could travel to the nearest star in a decade.This lofty goal of a “decade” will be forever beyond our grasp.As can be seen in the above documents, current technologies allow for speeds of .1 times light speed. That's 40 years to Alpha Centauri. The goal of 10 years may be beyond our grasp now, but certainly not 'forever'.Jumping like this we could occupy the galaxy in less than a million years.We can’t jump like this as I have already shown.Yes we can, as I have shown. Again see above solar sail documentation.Why have your millions of alien species been unable to accomplish this?This is ridiculous... probably only be one per galaxyI asked a question. Grammatically, you can only rebut a statement. However I do understand your point up to the end of the underlined quote. I am happy to see you have scaled back your argument to one species per 100 billion solar systems. Now lets go the final step. You say 1 per galaxy because we see no evidence of any others in our galaxy. True. Solar system redesign cannot be detected in the milky way. But a species only a million or two years more advanced that us should be able to affect galactic redesign. There are 100 billion visible galaxies, half of which are old enough and within a sufficient light cone, to contain 'one at the most' species of this level of advancement. And yet we see no evidence of galactic scale engineering.My opponent is trying to make organisms spontaneously evolve in the span of a year.I don't claim this. I apologize if I implied it through my unintentional obfuscation or omission.Nothing I have surmised is beyond physical law.Yes, it is. No laws of physics were broken in any of my suppositions. “Yes it is” is not sufficient rebuttal. Your '25,000' statement that, I assume, refers to the number of light years to the near Magellanic Cloud, is correct. We shall almost certainly want to, and indeed strive to conquer the galaxy when and if we are able. It is possible that other species may exist but have chosen not to manipulate their galaxies. But exploration and 'tampering' are basic human nature. Either none of your allowed minimum of 50 billion capable species thinks this way OR they don't yet exist.I can’t see the laws of probability, but do the laws exist?? Of course they do!Specious.Our existence is astronomically unlikely to be repeated elsewhere or elsewhen.in our own galaxy there are potentially habitable planets OR one per galaxyYou can't have it both ways. My opponent appears to dispute her/his own arguments.1 chance in 100 that the right 2 chemicals combined. 1 in 100 that the right asteroid hit at the right time, killing the right species. That makes the odds of ME not at 200 to 1 but 10,000 to 1 (unitary odds against are multiplied and increase exponentially). These are only 2 of the many unlikely events that would have to occur to produce humans. Another couple of dozen such events would make the odds against us being here greater than the number of particles in the known universe. I realize that this makes US equally unlikely, but again, that's another debate.There are millions of galaxies just like ours, there just needs to be a single organism to have life. Heck, there might even be life on Mars as pointed out in R2!I agree... just not sentient, technological life.I gratefully acknowledge my opponents efforts, skills and persistence and invite her/him to another debate of their formulation.This is a difficult topic to argue in the pro. First, I am trying to prove a negative. I chose this unorthodox approach as I thought that it might encourage more lively discourse. I think that it did. Second, I am feeling like a reluctant devil's advocate. Most of my life I have hoped that aliens and their attendant paraphernalia were real. I still love science fiction too. But unfortunately, as SETI searches become increasingly sophisticated and efficient; more planet bearing stars are discovered (just last month astronomers announced that almost all stars -multiples included- probably have at least one earth like planet); and our technology and accumulated knowledge grow exponentially fast, I can no longer ignore the numbers. We are probably alone.I really hope I am wrong, but if not...Realize as you ponder this monumentally anthropocentric thought, that, as its sole sapient citizens, we may be the universe's only means of self actualization. Therefore it is absolutely imperative that we put aside our differences before we destroy ourselves.