Astrobiologist Michael Russell once said that
the purpose of life is to hydrogenate carbon dioxide.
Or as Nobel prize-winning physiologist AlbertSzent-Györgyi put it,
life is nothing but an electron
looking for a place to rest.
While these aphorisms might not capture the“meaning of life”
that most of us look for
their point is the living organisms ultimately depend on and facilitate
the universe’s tendency to increase entropy
That may seem counter-intuitive, since living beings are themselves highly organized,
while entropy is a measure of disorder.
But as we know, complexity is not the same thing as order.
Every organism, just by living and breathing,
acts to increase the entropy of the universe.
Think of a photon arriving from the Sun,
packed with useful energy.
It can be captured by a plant or microorganismthat uses photosynthesis
to store that energy in the form of sugar.
But the sugar doesn’t contain quite as much useful energy
as the original photon
some of the energy ends up heating the plant andits environment.
An animal like us eats the sugar, and uses its energy
to create molecules of ATP, adenosine triphosphate.
ATP is like a little power-pack of energy
that can be sent to a part of the body
where it might be helpful, but ATP doesn’t have
quiet as much useful energy as the sugar
that went into making in. some of useful energy got lost
pushing around all the cell machinery that makes the ATP.
The proteins in your muscles utilize the energy in ATP to contract,
so that you can lift a barbell or a slice of pizza.
But not all of the useful energy of the ATP
goes into lifting the pizza – as before,
some of it is degraded into noise and heat.
Not only that, ATP’s useful energy can also
be used to repair broken-down cells or organs,
again becoming less useful in the process.
The pattern here is obvious:
every step along the way, the energy in that original photon
is gradually degraded, entropy increases,
and at the end all that’s left is an organized
温度稍微上升的植物 细胞 肌肉
but slightly warmer plant and cell and muscle,
plus some high-entropy infrared light that
gets radiated out into the universe.
Energy transforms from useful to useless
in the cause of keeping organisms like us alive.
In fact, life itself might have arisen because of entropy.
The early Earth had pockets of low-entropy conditions
full of useful energy, like warm alkaline vents on the ocean floor.
But there may have been no simple chemical reaction
that could take advantage of that energy
use up its usefulness, and allow theentropy to increase.
There were, however, more complicated chainsof reactions
that could do the job.
In just the right circumstances,
an appropriate network of chemical reactions might find a
way to sustain itself
by tapping into the useful energy in its environment.
Some networks might have become embedded in
molecular membranes, the precursors of cell wall
and broken away from their point oforigin,
becoming the first “living” organisms.
Maybe that’s how life began:
a complex combination of chemical reactions that figured out how
how to tap into otherwise unavailable useful energy.
We can tell a similar story about why stars shine.
Hydrogen nuclei have a ton of useful, low-entropy nuclear energy to release
if you can get them to fuse together into helium.
But there’s a big barrier to getting that
to happen – fusion is hard!
And yet, the cores of stars do the job marvelously,
so stars, like life, also survive because of
the increase of entropy throughout theuniverse.
Our sun takes a low-entropy fuel source
hydrogen nuclei and converts it into higher entropy energy.
photon of visible light
Life takes that higher-entropy energy as a fuel source
and converts it into even higher-entropy
energy, photon of infrared light
In a very real sense, the purpose of lifeis
to continue the mission of the stars.
大家好 我是Henry 谢谢观看
Hey, Henry here, thanks for watching.
This is the fifth video in a series abouttime and entropy
made in collaboration with physicist Sean Carroll.
This final video is supported by Audible.com,
a leading provider of audiobooks including fiction, non-fiction and periodicals.
The videos in this series are based off of Sean’s book
The Big Picture: On the Origins of Life, Meaning, and the Universe Itself
which is available, read by him, on Audible.
You can listen to “The Big Picture” oranother book of your choice
but why wouldn’t you choose The Big Picture
for free,with a free 30-day trial at Audible.com/minutephysics.
Again, that’s audible.com/minutephysics.