If there is no god, man has no special place or significance in creation. The universe was not "created" for us. We are simply here. we may be the result of underlying physical processes, but it does not carry any moral significance. I realise bringing this up in the context of atheism will necessarily be controversial because the term has such varied definitions but I wanted to discuss how people respond to the realisation that life has no purpose, meaning or significance beyond the fact we simply are here and have our own experience of pleasure and pain. that is our measure of right or wrong, but there is nothing really "objective" about it. its just how we evolved to sense of surroundings and what is in the interests of our survival as living organisms. our intellect is only one step away from that.
I think anyone here- regardless of their beliefs- may understand what I mean if you think about Outer-space. You can look up in the sky and the "universe" is out there, billions of light years in any direction. And here we are on this one tiny piece of rock hurtling round a giant ball of molten gas, and as tiny particles of organic matter with an infinitesimally small lifespan by comparison, we try to comprehend our significance amidst it all. why is the universe so peaceful when mankind is so violent? Is that a consequence of our egotism or do natures conflicts simply work on different timescales?
Maybe in thousands of years we will have spread out across other planets or stars, and found the secret to faster than light speed travel. It is possible, we may not make it that far, as we have no natural right to take our existence on his planet for granted. life is not a right. life just is. each of us can lose it, but the species may survive. And perhaps we can be convinced that it must be so. These are questions that those future generations will have to ponder as they go out into the vast open emptiness of outer space, and perhaps overcome the egotism of the adolescence of human history as we advance to become a global and then a planetary civilisation. what will our descendants say of us in a thousand or even million years time? Who will be there to greet us, if anyone at all?
I leave you with Carl Sagan's speech on the Pale Blue Dot. I don't have the answer, but it is none the less an interesting question of how we see ourselves in the context of a (practically) infinite universe and whether that it something frightening or liberating.