Long ago, humanity conquered the globe. Spreading from sea to sea, humans have traveled to the deepest recesses of the planet and harnessed the power of Earth’s natural forces. We have dominated the Earth and, in so doing, we forever altered the course of life on our world.

If that’s not enough, we have visited other worlds, traveled to the most distant edges of our solar system, and glimpsed the reverberations of the very fabric of the cosmos.

At least, that’s the basic story.

But in truth, while there is much that we know about our Pale Blue Dot and the cosmic abyss that exists just beyond our life giving atmosphere, there is a lot that we don’t know. But where does knowledge stop and uncertainty begin? How much do we really know, and what remains in question?

We asked for your most pressing questions, and they came pouring in: Could we ever travel to another star? Is warp drive really possible? How could we reverse the arrow of time? Here, Fraser Cain, the founder of Universe Today, dives into the answers—separating what we know from what we’ve yet to discover.