Work and World

What Is The Purpose Of Life? (Big Picture Ep. 5/5)

Astrobiologist Michael Russell once said that
“the purpose of life is to hydrogenate carbon dioxide.” Or as Nobel prize-winning physiologist Albert
Szent-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 that 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 microorganism
that 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 and
its 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
quite as much useful energy as the sugar that went into making it – some of that 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 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 the
entropy to increase. There were, however, more complicated chains
of 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 walls, and broken away from their point of
origin, becoming the first “living” organisms. Maybe that’s how life began: a complex combination
of chemical reactions that figured out 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 the
universe. Our sun takes a low-entropy fuel source and
converts it into higher entropy energy. Life takes that higher-entropy energy as a
fuel source and converts it into even higher-entropy energy. In a very real sense, the purpose of life
is to continue the mission of the stars. Hey, Henry here, thanks for watching. This is the fifth video in a series about
time 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” or
another book of your choice – but really, check out “The Big Picture” – for free,
with a free 30-day trial at Audible.com/minutephysics. Again, that’s audible.com/minutephysics.
Video source: https://www.youtube.com/watch?v=HxTnqKuNygE

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