Can Life Really Be Explained By Physics? (featuring Prof. Brian Cox) (2)
you personally. Because what you're doing is you're making,
you're radiating disorder out into the universe in a cavalier fashion
in order that you can live and process information and maintain your structure. But you are actually
making the universe more disordered as a results, and it's getting disordered
faster than it would be if you didn't exist. So it's sort of your fault, the end of time.
So life doesn't just run on energy. It runs on order that we borrow and then pay back. But
how can you use order to actually do stuff? Like move or repair your cells or copy your
DNA. For a minute, let's leave thermodynamics behind and think about one of humanity's oldest
ways of harnessing energy to do work, the water wheel. If you put a water wheel in a still pond,
not much is gonna happen. There's no current moving the water in one direction. Or
more accurately on the molecular level, water is bouncing around in every direction.
That's disordered energy. You can't really do anything with it. But if
we have a situation where all the water is moving in one direction, then that's useful.
This moving water has more order. So we can stick a wheel in it and borrow energy to do work.
Believe it or not, this is essentially what living things do. They tap into sources of highly ordered
energy to power molecular machines. Only, instead of water, that highly ordered source of energy is
protons. The details are complex and definitely worth their own video. But basically when we burn
food using oxygen, we borrow some of its ordered energy to pile up protons inside mitochondria.
Or in a chloroplast, ordered energy from the Sun is used to pile up protons in one place.
And when we let these piled up protons flow out, that's useful energy, like water moving downhill.
[Brian] Then sticks this little thing in it called ATP synthase and that spins around and makes ATP,
and then you do all this stuff. It's literally a water wheel that sits in a waterfall of protons.
We're sort of glorified like mills on a pond, they're just
turning water wheels, they're just very small and perhaps much more complicated. Photosynthesis
is just a way to use the Sun to rip water apart and stack up protons. The mitochondria is the
same thing. It's a little bag that rips things apart and stacks protons up on one side so
that we can wash them through this water wheel and make fuel to continue doing other interesting
things in cells. Literally why the mitochondria is the powerhouse of the cell. Now, you know.
One of the great commonalities in all living things is the way that they manage energy. I'm
thinking in particular of the fact that all living things pump protons around across membranes. And
as far as I'm aware, that's common to everything. I don't think there's an exception to that.
Believe it or not, this universal trait can give us a huge clue as to how life might have started.
Or at least where it started. In the rocks of the deep sea hydrothermal vents, we find
pockets with lots of protons on one side and not many on the other. These proton
rivers are a natural energy source that many scientists believe billions of years ago,
powered the first transition from regular chemistry to living biochemistry.
I tend to think of it, initially, the origin of life is a transition from geochemistry to
biochemistry, which it must have been. You have to have a world, it's geologically active and somehow
chemistry gets sufficiently complex that it can store information and copy.
Information, this is the other key ingredient that seems to separate
living things from nonliving things. So what does that mean? In every living cell,
in addition to the energy or molecular machines that we discussed already, we can find one more
example of complexity and order hiding in this universe that's on the road to disorder.
DNA and the genetic code. One of the biggest discoveries in the history of
biology is that there is a physical molecule that carries the instructions for a living,
DNA. The information is in the structure. It's an arrangement of atoms into an ordered pattern
and that lets us extract some meaning from it and do the interesting things that life does.
Now, spoiler alert, eventually you and me and every living thing on Earth will die. But life
itself will go on, thanks to this information stored in ourselves. Because I share some of
that information with you. I share some with other apes, I even share some of the banana. The
instructions for living are a form of information that's bigger than any one living thing.
My picture is, that really the Earth is a giant genetic database. And it happens that that data
is stored in little local objects. So there are bits of it. So there's some in me and some
in blades of grass and so on. 'Cause what we're talking about here is that just the ever shifting
gradual change in where the information is stored in this great database of life.
But this brings up one more big problem. And it's one that we don't have an answer for. If
we could somehow go back through time, meeting every ancestor along the way from early animals
to single celled microbes, all the way back to something so simple, it can copy itself using
only chemical reactions. Well, at what point do you decide that's the first living thing?
It's a label, isn't it? It's semantics, I think.
It reminds me of the debate in astronomy about whether Pluto is a planet.
'Cause I first of all, don't care, but that's because I'm not a professional astronomer.
They spend ages having meetings, and defining what a planet is. Actually, it's an interesting world
that orbits around a star. It might not clear its own way, it might not be big enough to be a planet
and so on, but it's just an interesting world. So, I don't care what it is. I think we'll only
truly understand how life could begin, when we see a second genesis somewhere. Which that's why Mars
is so interesting and so important, because it's the most accessible, possible example.
It's interesting to note that if we're interested in questions about the origin of life, it might
be easier to see that on Mars than it is on Earth 'cause on Earth, the evidence has been wiped away.
The only evidence we have is in our genome. It's the living things today, which are separated
by 3.8 billion years or so from the first living things. But on Mars, it's been in deep freeze with
little geology and no weathering for well over three billion years. So if life began on Mars,
we may well have more pristine evidence of how it began on that planet, than we have on this planet.
Of course not everyone thinks that these are questions that science can answer. I
had a professor in college, a biochemistry professor, who once told us that finding a
useful definition for life well, science couldn't help you there. As he put it,
"It was a question for poets." And I asked Brian, if he agreed with that.
Our presence in the universe is probably the most,
well it's amongst the most interesting scientific questions. And arguably the
most important and interesting scientific question. How did we come to be here?
And that doesn't just mean, how did the universe begin? It means literally how did, on this planet,
how did atoms get complex enough to start exploring the universe? Living things are one of
the categories of objects that are created by the laws of nature, permitted to exist by the laws of
nature. Another one are stars. So we understand, we say, well, let's understand the origin of the
stars and we know what we're talking about. So I think in that sense, it's perfectly reasonable to
say, well, let's understand the origin of the living things. 'Cause the living things are
a structure in the way that stars are a structure. They're just a lot more complicated. It's the most
profound question, how did life emerge in this universe? In the live shows, I start with the
question, what does it mean to live a finite, fragile life in an infinite eternal universe?
Then I immediately say that I don't know because if I knew I'd charge more for tickets
At least you're honest.
Or actually,
When we look at everything that we know about being alive and we try to distill
it down to protons and the movement of heat and energy from here to there
or that the letters of the genetic code are just a repeating pattern of information,
that can be uncomfortable. I mean, being alive certainly feels like more than that.
Nature forces you into uncomfortable position sometimes.
Often, when you look at it. And that's good for you, It's good for you to be confused.
I hope that that idea applies to life. Because uncertainty can be excitement.
And it's what sets you at the edge of when you're standing at the cliff of, at the edge
of human knowledge. I mean stepping forward is exciting. You're skydiving into the unknown.
I think it's one of the great unanswered questions and that's what makes it interesting. And
that's what I'm interested in. I'm interested in questions that we've not yet answered,
but we have a chance of groping towards an answer.
Stay curious.
If you enjoyed this episode and you'd like to learn more
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Really? Really? Really? Really? How high can I get?
Erwin Schrodinger.
[Man] Schnell! Schnell!
If you must have the Erwin Schrodinger,
remain inquisitive.
[Man] Nailed it.
