What condensed matter physics is not the same thing as solid state physics.
Solid state physics is the study of, say, electrons in metals like insulators, semiconductors,
super conductors and so on.
But what condensed matter physics is, is it goes beyond the behavior of individual components
to see how they self organize in some kind of collective state.
In other words, the behavior of the collective is much more important than the behavior of
the individual.
An example that everyone's familiar with is a flock of birds.
Every bird is flying around.
They, in principle, can fly in any direction.
But in a flock they all fly together in some cohesive way.
Another example in physics is just atoms.
If you push air or push water, your finger just goes straight through it.
But if I take this book and I push it, my finger doesn't go through it.
It just moves.
I can transmit a force.
That's because the atoms in it have self organized into some collective state.
Rather than just do their own thing, they all move together.
It's a kind of conspiracy of atoms, if you will.
Now, turning to biology — the big puzzle in early evolution is this: The planet started
about 4.6 billion years ago.
We know that the last universal common ancestor of all life was about 3.8 billion years ago.
That's the organism from which all life on Earth is descended, or maybe a community of
organisms.
Now, we know that because we can look at genes in modern cells, genes that code for the machinery
that makes proteins.
That machinery we can trace back by undoing the process of evolution, if you will, back
to about 3.8 billion years ago.
What that means is that the modern cell had already evolved, more or less, with it's current
complexity, 3.8 billion years ago.
The planet is 4.6 billion years.
So we went from nothing to the complexity of the modern cell in less than a billion
years.
And after that evolution didn't do that much.
So how is it possible that evolution started off so fast and then later on made many evolutionary
changes but nothing fundamental to the architecture of the cell?
Well the answer that we've proposed is that it was, in fact, collective effects.
Today, genes are transmitted from one person to the other, and that person has to be their
descendant.
Everyone is familiar with a family tree.
But what we discovered is that if we assumed that early on in life genes are transmitted
between individuals, even if they're not related — this is called horizontal gene transfer
— we get not a tree of life, but a network of life.
And the network grows exponentially fast.
Just like how the Internet grew very quickly in the mid-1990s, because you had a network
effect.
All the computers in the world could talk to one another.
The understanding of condensed matter physics enabled us to really understand how we could
model the collective behavior of organisms that could transfer genes.
What we able to show was that the properties of the genetic code that emerged from that
would agree with what we see today.
If we assumed just a regular tree of life behavior — no network effect — we couldn't
explain the speed of life, the speed at which evolution occurred.
We couldn't explain the fact that every organism has the same genetic code.
We couldn't explain the fact that the genetic code is remarkably robust to ours.
In short, then, condensed matter physics does have applications in biology because biology
is all about collective effects.
It's a wonderful testbed for understanding ideas of condensed matter physics, but in
a more broader sense, the idea of strongly interacting collective properties of matter.