Last time I made a forum it was closed because I didn't site the information. 1. http://en.wikipedia.org/wiki/Fine-tuned_Universe 2. http://www.pbs.org/wgbh/nova/physics/blog/2012/03/is-the-universe-fine-tuned-for-life/ There's my 2 sources. 1. *In the 1st source I find this "The fine-tuned Universe is the proposition that the conditions that allow life in the Universe can only occur when certain universal fundamental physical constants lie within a very narrow range, so that if any of several fundamental constants were only slightly different, the Universe would be unlikely to be conducive to the establishment and development of matter, astronomical structures, elemental diversity, or life as it is presently understood." 2. *In the 2nd source I find this "Another interesting example of a finely-tuned initial condition is the critical density of the universe. In order to evolve in a life-sustaining manner, the universe must have maintained an extremely precise overall density. The precision of density must have been so great that a change of one part in 10^15 (i.e. 0.0000000000001%) would have resulted in a collapse, or big crunch, occurring far too early for life to have developed, or there would have been an expansion so rapid that no stars, galaxies or life could have formed. This degree of precision would be like a blindfolded man choosing a single lucky penny in a pile large enough to pay off the United States’ national debt." [My question is simple. How do they know if the critical density of the universe was off by 1 in 10^15 (that's 1 in 10000000000000000) the universe would have collapsed or expanded to rapid for stars/galaxies to form?] I've been asking this question around school (I'm a teen so I still go to highschool) I asked a few of my teachers that told me they don't know, then I asked one of my teachers that I thought would have no clue on the issue, and I was right she didn't, but she told me that she knew a retired math/physics teacher that would probably know. We ended up calling him the next day and he did know alot about it. He said it would be hard to explain the math over the phone but on Tuesday he would come over after school and explain how they know if certain constants were off just slightly life would be impossible. I'm going to come up with a list of questions to ask him. My first question with be the same question I'm asking you guys right now. 1. How do they determine if *insert constant* varies *insert amount* life would be impossible. Any other questions you want me to ask I will write down and on Tuesday after are meeting I will respond on this form. So ask away, he seems like a very intelligent person.