What does it mean to be alive, biologically speaking? It's a surprisingly complex issue.
Philosophers constantly debate the meaning of life, and centuries of deliberation haven't brought us any closer to answering that question. In fact, many would argue the debate itself is most important, and arriving at a conclusion is besides the point. But you'd think that defining life squarely in terms of biology and physics would be a straightforward matter, right?
It turns out, scientists aren't too sure either. There are a lot of arguments and theories over where we should draw the line between living and non-living things, especially as we close in on tinier and more fundamental units of matter. In the past, biologists agreed that the cell is the smallest fundamental unit of life. But now that we know more about the particles that assemble into cells, how can we be sure that the life-like activities we observe in cells aren't just the result of a complex mass of particles responding to the laws of physics? By that rule, how can we argue that a single atom isn't alive, if it's also governed by the same laws?
This video clearly and beautifully explains some of the quandaries faced by scientists and philosophers alike, as our increasing knowledge of the universe challenges our previous assumptions about life, death, and matter.