Are all great scientific thinkers atheist?

Sometimes religion and science don't always place nicely together, but what about religion and space? Is there room for spirituality on our future intergalactic journeys? Robert Lamb ponders in this video. See more spirituality videos.

Did Charles Darwin's theory of evolution put his world at odds with God? What about Richard Dawkins, evolutionary biologist and self-proclaimed atheist who openly speaks against religion?

If many scientific visionaries aren't religious, does that mean they're atheist?

Sure, many marquee scientists haven't counted themselves among the clergy, but hold on a second before hustling them all into the same group. It all boils down to definitions. Depending on your interpretation, atheism may equate to lacking a belief in God or a more firm belief that God doesn't exist [source: University of Cambridge].

Agnosticism muddies the (holy) waters even more. In general, agnosticism means a person neither believes in nor denies God's existence -- it insinuates not knowing for sure either way [source: Stanford Encyclopedia of Philosophy]. A lot of ridiculously bright folks, like Darwin, have been mislabeled atheist when in fact they're agnostic.

More than 45 years after Darwin journeyed to the Galapagos to peer at hummingbirds, the naturalist shed light on his religious beliefs in a private journal. He wrote about lacking knowledge to know for sure if there's a higher being: "The mystery of the beginning of all things is insoluble to us; and I for one must be content to remain an Agnostic" [source: PBS].

Other self-described agnostics such as physics and astronomy experts Stephen Hawking, Albert Einstein and Carl Sagan are sometimes mislabeled atheists. These minds have challenged traditional religions and God's role in everyday life, but may not have rejected God outright.

Here's Sagan: " ... A general problem with much of Western theology in my view is that the God portrayed is too small. It is a god of a tiny world and not a god of a galaxy, much less of a universe."