What is life? It's a deceptively simple question. Philosophers and scientists have pondered it for millennia, and they have yet to settle on a satisfactory answer. And as we venture into a new era of scientific exploration, the inevitable question arises: will we recognize life if we find it elsewhere in the cosmos?
How would you define life? Would that definition hold up on a distant planet around a distant star? Learn more by watching the video above. And don't forget to reach out on Twitter, Facebook, or by leaving a comment below. Come on, talk nerdy to me!
CARA SANTA MARIA: Hi everyone. Cara Santa Maria here. Here’s a deceptively simple question: What is life? What does it mean for something to be--you know--alive? Throughout the ages, philosophers and scientists have posed this question, but the answer? Well, that's not so straightforward.
PAUL NURSE: Living things are entities. They're bounded objects separated from the environment, and they are built on particular chemistries. And there's one aspect of that chemistry which is very important, and that's carbon.
CSM: That's Nobel Prize winning geneticist Sir Paul Nurse, describing physicist and Nobel Laureate Erwin Schrodinger's 1944 book "What is Life?" So since biology is, literally, the study of life, I figured I would start looking there for answers. But when I checked the glossaries of five different college-level biology textbooks, the word life was actually missing! It seems as though scientists can't settle on a single definition, because there are almost always exceptions to the rule. There are some central features, of course, like the possession of genetic material and the ability to pass it along to offspring by reproduction, which means, in essence, that life is subject to Darwinian evolution. Living things are also highly organized, and they use energy to carry out their biological processes. But fundamentally, the answer seems to keep coming back to chemistry.
NEIL DEGRASSE TYSON: What are the ingredients of life? The number one atom in your body is hydrogen. The number two atom is oxygen. Together, they're making mostly water that's in you. Next is carbon (in this order), next is nitrogen, next is other stuff. My favorite element: other. Yeah.
CARL SAGAN: Life is just a kind of chemistry of sufficient complexity to permit reproduction and evolution. I wonder if we'll ever find a specimen of life based not on organic molecules, but on something else, something more exotic.
CSM: Ahhh, and here's the quandary. As Neil deGrasse Tyson and the late, great Carl Sagan point out, there are fundamental building blocks of life across all species on Earth. It's hard to put our finger on just what life is--I mean, it's sort of intuitive, we pretty much know it when we see it--but can we expect to use that same logic when seeking out life on other worlds? We've entered a new era where scientists called astrobiologists are actively searching for signs of life on other planets, near and far. And some cosmologists, like Charley Lineweaver, think the line between life and non-life may be fuzzier than previously thought.
CHARLEY LINEWEAVER: There is non-life, and it evolves somehow into life. And we're trying to understand that. That means that the idea that there's black and then white should be replaced by how alive is something.
CSM: A virus, for example, is sort of alive. It has its own genetic material, but it can't reproduce without the help of a host, and it's missing the other biochemical machinery usually found in living things. And what about an entire ecosystem? If a coral reef or a jungle can die, is it operationally alive? Geneticist Craig Venter made DNA from scratch and injected it into a hollowed out cell to create the first ever synthetic organism. Should we call that life? And scientists were stunned the first time they came across the bizarre creatures we now know thrive at deep-sea hydrothermal vents. They're obviously alive, but they were definitely unpredictable. Which leads me to what's perhaps the most pressing question as we're thrust into a new era of space exploration--will we recognize life if we find it elsewhere in the cosmos? What do you think? Reach out on Twitter, Facebook, or leave your comments right here on The Huffington Post. Come on, talk nerdy to me!