The Physics of Life (ft. It's Okay to be Smart & PBS Eons!)

SPEAKER_1 (0:00)

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Matt O'Dowd (0:33)

Our universe is prone to increasing disorder and chaos. So how did it generate the extreme complexity we see in life? Actually, the laws of physics themselves may demand it.

How did life begin? We can seek the answer in the chemistry of the early Earth or in the biology of the first cell. In fact, our friends at PBS Eons and It's OK to Be Smart will do just that in companion videos to this one.

But we all know that chemistry and biology are just applied physics. So can we approach the question of the origin and the very nature of life from the point of view of physics? We're sure going to try.

To understand life, we need to understand entropy. The universe tends toward disorder, decay and equilibrium. A hot cup of coffee will tend towards the same temperature as the room. And the hot, dense, early universe must expand. Stars always burn out, black holes evaporate. The particles that make up any system all have some degree of random motion. That random motion tends to drive the system towards the most common arrangement of particles. Such a random, disordered, unspecial arrangement is a high entropy state.

Interesting arrangements like thermal energy being concentrated in your cup of coffee or all the matter in the observable universe being crunched into an infinitely dense point are low entropy. They're highly specific configurations that almost never happen by chance. So entropy is sort of a measure of the boringness of a system, the commonness of the arrangement of particles. The second law of thermodynamics tells us that a closed system will only increase in entropy. The universe will only get more boring. But there's one type of system that seems to resist the second law of thermodynamics and maintain low entropy. That system is life. Life has very low internal entropy because its structure is extremely specific and non-random. The molecular machinery of even a single cell defies belief.

You know what? I'd prefer to let a real biologist convince you. Hey Joe, tell them how it is.

Joe (2:53)

Cells are complex. Okay, that's a massive understatement. Inside just a single one of your cells, you have 6 billion base pairs of DNA storing hundreds of megabytes of data. Intricate molecular machinery made of RNA and protein unpacks, transcribes, cuts and splices and processes that data to build and control an entire factory of protein molecular machines, which in turn power the entire biological process that is you.

Easy, right?

Matt O'Dowd (3:24)

Not only is life stunningly complex, but that complexity increases over extremely long time scales. In fact, over eons.

Right, Blake?

Blake (3:33)

When we look at the fossil record, we see the evidence of evolution carved in stone. When we trace the development of fossils over the nearly 4 billion years of life on Earth, we see clear as day the steady trend toward greater complexity. From the first single celled organisms to simple ocean invertebrates, to an explosion of complex animal life, and finally to us.

Matt O'Dowd (3:50)

Naively, this preservation and increase in order appears to contradict the second law of thermodynamics. Entropy appears to either stay constant or decrease. The Earth's biosphere, at least, becomes less boring over time.

But let me be clear. There is no violation of the second law.

The second law tells us that closed systems must increase in entropy, so systems are unable to exchange energy with the outside environment. But living organisms and indeed the Earth's biosphere are not closed. Both receive energy from outside. Ultimately, that source of energy is the sun. Its light warms the atmosphere in the oceans, and it powers photos.

SPEAKER_1 (4:30)

College football is back. Sir Hilton called on me, the superstition concierge, to make your fan rituals a reality. Need a room to match your lucky number? We got you. Want to make sure our team doesn't wash your lucky jersey? Oh, that smells lucky.

Hilton's unmatched hospitality can keep up with any superstition. Even a marching band wake up call at 555 in 55 seconds. Hit it!

When you need a team that will do whatever it takes on game day, it matters where you stay. Hilton, for the stay.