You’d think we’d have a solid answer by now. After all, you are living it, and so am I. But if you walk into a room full of biologists and ask them "life what is it," you’re going to get a dozen different answers that somehow manage to contradict each other while all being technically right. It’s frustrating. It’s weird. Honestly, it’s a bit of a mess.
We know it when we see it. A blade of grass is alive; a pebble is not. A cat is alive; the scratching post is definitely just carpet and wood. But when you try to pin down the exact moment something transitions from "chemistry" to "biology," the lines start to blur in ways that make even the smartest people on the planet feel like beginners.
The Definition Dilemma
The most common way we try to define life is through a checklist. You probably remember this from high school. Metabolism, reproduction, response to stimuli, homeostasis—the usual suspects. But there’s a problem. Fire grows, uses energy, and responds to its environment. Is fire alive? Most people would say no. What about a mule? It can't reproduce, but it’s certainly breathing and walking around.
NASA uses a "working definition" that describes life as a self-sustaining chemical system capable of Darwinian evolution. It’s a clever way to phrase it. It moves away from just looking at what a creature does and focuses on what a creature is over long periods of time. Yet, even this doesn't satisfy everyone.
The Virus Problem
Viruses are the ultimate curveball in the "life what is it" debate. They don't have cells. They don't eat. They can't reproduce on their own. Outside of a host, they are basically just complicated crystals or "zombie" particles. But once they hijack a cell, they act with a purpose that looks suspiciously like life.
Virologists like Jean-Michel Claverie have argued that we’ve been looking at viruses all wrong. We look at the virion—the tiny particle—and say it’s dead. But Claverie suggests the "virocell" (the infected host cell) is the actual living organism. It’s a radical shift in perspective that shows how flimsy our definitions really are.
Entropy and the Energy of Being
One of the coolest ways to look at life comes from physics, specifically thermodynamics. In 1944, the physicist Erwin Schrödinger wrote a book titled What is Life? and he proposed something fascinating. He noted that the universe tends toward disorder, a concept known as entropy. Everything falls apart. Your car rusts, your house gets dusty, and stars eventually burn out.
Life does the opposite.
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Life is something that actively resists decaying into equilibrium. We take in energy—sunlight, sandwiches, whatever—and use it to keep ourselves organized. We are little pockets of order in a chaotic universe. As soon as you stop being able to resist entropy, you aren't alive anymore. Basically, being alive is the act of staying "not-dead" by constantly burning energy to keep your internal structure intact.
The Information Theory
There’s another camp that thinks life isn't about biology or physics at all. It’s about information.
Think about it. A DNA molecule is essentially a code. It’s a set of instructions. Sara Walker, a theoretical physicist and astrobiologist, argues that life is what happens when information takes control of matter. In this view, the "what is it" isn't the carbon or the water; it's the specific sequence of instructions that allows that matter to persist through time.
This gets weird when you start thinking about AI or digital life. If life is just a self-replicating information system, does a computer program that can evolve and adapt count? Most biologists say no because there’s no physical "metabolism," but the information theorists are keeping an open mind.
Life on the Edge: Extremophiles and Beyond
We used to think life was fragile. We thought it needed a very specific temperature, a specific amount of light, and a very specific atmosphere. Then we started finding things living in places that should be impossible.
- Tardigrades: These "water bears" can survive the vacuum of space, extreme radiation, and being frozen to near absolute zero.
- Hydrothermal Vent Communities: Deep in the ocean, where there is zero sunlight, entire ecosystems thrive on chemicals spewing out of the earth's crust.
- Desulforudis audaxviator: A bacterium found two miles underground in a South African gold mine. It lives in total isolation, drawing energy from radioactive uranium.
These discoveries have forced us to realize that life is much more robust than we gave it credit for. It doesn't just exist; it persists. It finds a way to squeeze into every available crack in the universe. This makes the search for extraterrestrial life both easier and harder. It could be anywhere, but it might look nothing like what we expect.
The Subjective Experience
We can talk about chemicals and Darwinian evolution all day, but that’s not really how we experience life, is it? To us, life is consciousness. It’s the feeling of the sun on your skin or the weird knot in your stomach when you’re nervous.
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Biologists usually ignore this part because it’s "unobservable." But philosophers like David Chalmers point out the "hard problem" of consciousness. We can map every neuron in a brain, but we still don't know why those neurons firing creates a subjective feeling.
Is consciousness a requirement for life? Probably not. A tree is alive but (probably) doesn't have "feelings" in the way we do. However, for us humans, the definition of life is inextricably linked to our awareness of it. We are the universe trying to figure itself out.
Why "Life What Is It" Matters Right Now
This isn't just an academic exercise. Understanding the boundaries of life has massive implications for medicine, ethics, and space exploration.
If we can define the exact chemical "spark" of life, we might be able to create it from scratch in a lab (synthetic biology). If we understand how life resists aging and entropy, we might be able to extend human lifespans significantly. And if we head to Mars or Europa, we need to know exactly what we’re looking for so we don't accidentally step on a Martian microbe just because it didn't look like a "living" thing to our limited human eyes.
Common Misconceptions About Life
A lot of people think life requires oxygen. It doesn't. Many organisms (anaerobes) find oxygen toxic.
Others think life must be based on carbon. While everything on Earth is carbon-based, some scientists speculate about silicon-based life. Silicon is right below carbon on the periodic table and shares some of its bonding properties, though it’s much more rigid and less "flexible" in a biological sense.
There's also the idea that life is "purposeful." Evolution doesn't have a goal. It doesn't try to make things "better" or more complex. It just filters out what doesn't work. Life is the result of billions of years of trial and error, not a planned ascent toward perfection.
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Moving Forward: How to Think About Life
So, where does that leave us? Honestly, we may never have a single, perfect sentence that explains "life what is it." And maybe that’s okay. Life seems to be a process rather than a thing. It’s a verb, not a noun.
If you want to wrap your head around this concept in a practical way, stop looking for a definition and start looking for patterns. Look for systems that are complex, self-organizing, and capable of changing over time.
Actionable Perspectives on Life
- Broaden your scope: Don't limit your idea of life to things with faces or even cells. Look at the "system" level.
- Follow the energy: If you want to find where life is happening, look for where energy is being used to create order.
- Respect the gray areas: Accept that things like viruses or future AI might sit right on the fence. Categorization is a human tool, not a universal law.
- Value the persistence: Recognize that the most defining trait of life is its refusal to stop. It adapts. It changes. It continues.
The next time you look at a plant or even a moldy piece of bread in the back of your fridge, remember that you’re looking at a miracle of physics. You're looking at matter that has somehow learned how to keep itself together against all odds. That is the essence of what life is. It's the stubborn insistence of "being" in a universe that is slowly fading away.
Understand that life isn't just a biological category. It's a way for the universe to organize itself and, eventually, to look back at itself and wonder what it is. That wonder is arguably the most "alive" part of the whole equation.
Step-by-Step for Exploring the Topic Further:
- Read Schrödinger’s "What is Life?": It’s short, and even though it was written in the 40s, it’s still the foundation for how we think about the physics of biology.
- Look into Astrobiology: Check out NASA’s Astrobiology Institute website. They have amazing resources on how they are currently looking for life on other moons and planets.
- Explore Synthetic Biology: Look up the work of Craig Venter, who created the first "synthetic" cell. It’s the closest we’ve come to "making" life from non-living parts.
- Observe your environment: Take ten minutes to sit outside and identify five things that are clearly alive and five that are not. Then, try to find one thing that is somewhere in the middle. It’s harder than it sounds.
Ultimately, "life what is it" is a question that invites more questions. That’s not a failure of science; it’s a testament to how incredible the phenomenon actually is. We are part of the mystery we are trying to solve. Every breath you take is a data point in the greatest experiment in the cosmos.