Physics Makes Aging Inevitable, Not Biology (2016) | Hacker News Reader

Physics Makes Aging Inevitable, Not Biology (2016)

nautil.us

29 pointsusgroup42 comments

The main argument made, concerning the second law of thermodynamics can explain why we age but I am not sure it proves that aging is incurable. The second law of thermodynamics says that entropy increases in closed systems. A human is not a closed system. The second law does not prevent a conceptual procedure where, through an operation/cure we decrease the entropy of a patient/human. Of necessity that procedure would produce a bigger increase of entropy in the environment with which the patient/human interacts, but that's not a problem.

As an example of the above imagine a fetus 2 weeks old and a fetus 20 weeks old. The is much more order in the 20 week fetus, therefore less entropy. It's also easy to realise that the fetus is not a closed system since it interacts heavily with it's mother.

Under the same argument made in the article, a room can never be tidied. It can only become messier and messier. And yet, somehow, my house is set right every other Friday after the cleaning people come through.

To me, it seems obvious that the second law is at most a contributory factor. The real reason we age is that indefinite longevity is energy-intensive and not favorable for the propagation of the information patterns in our genes. Our genes have optimized for propagation, because information patterns that didn't have died out or been dominated. Anything else, including whether you live a day beyond the minimum required to help your children propagate their genes, is ancillary.

Here's a thought experiment. Imagine you created a niche where the minimum reproductive age were gradually raised by artificial means. I suspect that in such a niche, you'd begin to see adaptations that would lead to longer lifespans. If you ran the experiment long enough on a large enough population, I'd bet natural selection would figure out how to get the average lifespan well above its current level. We could try it on some small animals [ed: not bacteria, since they do not reproduce sexually and it would be infeasible] to figure out if this is true, but it's hard for me to imagine it isn't. (How much human suffering would be involved, and whether we'd even recognize the result of this process as human, is also beside the point!)

A friend from the university used that line on his parents as an excuse for the state of his room. Luckily for him they didn't know enough physics to call him out on it because his room was not really a closed system.

Young Me: "Why clean it? It'll just get dirty again."

My Dad: "Why feed you? You'll just get hungry again."

Or spent long enough to think about why rooms can be cleaned each week?

You can trade entropy for order, but that doesn't necessarily mean you can trade any entropy for a particular set of order, like making a specific older person young again, or keep a person young forever.

I haven't read the full article yet but there's more to thermodynamics than just a see-saw of entropy and order; it is also a factor in chaotic systems and "time's arrow"--which is pretty deep mystery physics. Quantum mechanics works just as well in either direction, time-wise. Theoretically a photon doesn't experience time at all, and every electron is indistinguishable from another. But at our scale, many processes seem unpredictable and irreversible.

Even if you could catch all the smoke a candle puts out, and you add energy to make a candle out of it, it wouldn't be the same candle. We can take a broken egg, use it fertilize grain, feed the grain to a chicken, and make a new egg... but we can't just put the broken egg directly together again. And it might be impossible, no matter what the available energy, to keep someone from aging.

Beyond entropy and order, which are statistical concepts, aging is the matter of how the state of our body progresses. And managing state seems a lot harder than just measuring total aggregate order in a system.

You can only cheat the second law of thermodynamics by emitting your entropy on the rest of the universe, and assuming the universe is a closed system, then the heat death of the universe prophesied by the second law of thermodynamics still puts a hard upper limit on human lifespan.

Which is basically the crux of this whole disagreement--sure, it's scientifically possible to live orders of magnitude than we currently live, but even if you live for a million years, you're just punting on the question of mortality, you're not answering it.

This was a very well-written and interesting piece. I disagree with the general premise that this is generally related to thermodynamics, even at the nanoscale. Accumulated errors can be corrected with additional energy input---that's the premise of error-correcting codes used in DNA. Were it not for error-correction, DNA mutation rates would be much higher than we observe. In principle, couldn't living things develop similar machinery for correcting other accumulated errors (albeit at the expense of requiring additional energy).

Right. Years ago, there was this creationist/anti-evolution fallacy going around called the "thermodynamics of matter." The fallacious premise was that matter in a bounded system would always get more disorganized. Really, this was just a misappropriation of thermodynamics. You can disprove this with a simple thought experiment with an hourglass shaped glass vial containing salt in one section and water in another.

If you can get energy, you can reorganize matter.

This is a terrible argument. There are biological organisms that don't age. And we can design mechanical systems that can be made to run (essentially) eternally by swapping out parts. The human body is constantly turning over cells, so there's no intrinsic reason it couldn't have evolved to function this way.

Are there? I disagree with the article, but have we really conclusively found organisms that do not age?

Turritopsis dohrnii. Lobsters and some turtles as well, they grow in size, but remain youthful otherwise.

And how much did the environment they live in change over ages?

But if you swap all parts is it still the same mechanical system?

https://en.wikipedia.org/wiki/Ship_of_Theseus

It's a good and interesting question, though probably irrelevant to the discussion at hand. Organ transplant recipients do tend to feel themselves to be the same person, empirically.

How many brains have we transplanted?

Never, to my knowledge. It has been done in animals though:

https://www.cnbc.com/2018/05/15/two-surgeons-in-china-develo...

And anyway, it's not really the point. There is no reason, in principle, that the brain cannot be repaired in place.

Same day on Nautilus:

Why Aging Isn’t Inevitable: The great variety of aging styles among plants and animals suggests it can be controlled.

http://nautil.us/issue/36/aging/why-aging-isnt-inevitable

The article makes a convincing argument, but there are some organisms that don’t appear to age. How does that fit?

Because living organisms are not closed systems and include mechanisms specifically "designed" to fix themselves. They consume energy from the outside to reverse entropy in them.

The argument made in the article isn’t the simple (and obviously fallacious) entropy argument.

The argument against this is simple. Rats and Humans are both mammals. Yet rats age an order of magnitude faster than humans, and they display precisely the same old age symptoms as they age. A rat is old at 2 or 3, and a human is old at 70 or 80. (Dogs and many other animals are in-between). This strongly indicates that aging is a biologically engineered process, optimized for each species.

That isn't to say there isn't some limit imposed by physics. Just that the limit doesn't appear relevant to what we call aging. The argument some have made below that physics imposes an age limit on a cell makes sense. Physics could impose limits on the lifespan of an organism’s replaceable parts — that could well be why organisms continually need to replace them.

This is a heavily flawed argument, as others have pointed out. Consider this: why does this argument apply to indavidual humans but not to the human race?

Ie. why are babies born young if they are created by old humans?

Biology seems to have found a way to beat physics: reproduction. Individuals do age, but life itself seems to be proceeding at a solid clip.

It all depends on having a source of low-entropy energy. For Earth that would be sunlight. Other ingredients are needed, naturally, namely: an environment full of the things that are needed to turn low-entropy sunlight into local low-entropy systems that externalize their entropy production (life). First we have photosynthetic, and then we have all the lifeforms that depend on them. (Yes, there's also chemosynthetic lifeforms that use other a different path to locally reducing entropy.)

Yeah. This argument seems valid for an individual cell. But not for new cells…

What is a "new" cell? Cells reproduce by division so when you go from one cell to two cells, there is typically not a clear cell that is the original one.

Counterpoint I posted in r/askscience last year:

https://old.reddit.com/r/askscience/comments/7kq5r4/what_det...

This would make sense if we weren't multicellular and didn't have the ability to repair damage and replace cells. Aging is preprogrammed to ensure population variance which is need for survivability in times of sudden environmental changes.

Looking into the author I found this lecture about his book Life’ Ratchet:

https://www.microsoft.com/en-us/research/video/lifes-ratchet...

>Peter M. Hoffmann is a professor of physics and materials science at Wayne State University in Michigan and the founder and director of the university's Biomedical Physics program.

This article is written as if Aubrey de Grey didn't exist!

In addition to the featured scrapyard cars one could peruse these vintage models:

https://www.classiccarpassion.com/media/101072/55.jpg

They still go because comprehensive maintenance and damage repair has been carried out -- repeatedly. The same approach is viable for the human body, argues de Grey.

A human body already has a lot of tools to fix almost whatever get broken in it given necessary materials, elements and motivation. I still can't recognize why aging can be considered inevitable in such a system that is very far from closed. All it takes to find a way to rejuvenate it effectively is to determine everything it needs and how to motivate it to activate the necessary repair mechanisms.

I don't buy the physics argument. It's not like egg and sperm-generating cells aren't subject to thermal aging, and yet zygotes are biologically new rather than 18-45 years old. Life should be getting progressively worse through time rather than effectively resetting every generation.

> Although the test tubes are not aging (old test tubes do not break easier than young ones)

This is untrue. Glass accumulates microscopic fractures as it is used, which increase the likelihood of breakage.

typo in title. should be "inevitable"

Why? That would not make sense with the rest of the sentence ("not biology" what?)

Click through the link. The correct title is there.

And fhood/MSM are correct. Adverb/noun fun.

because inevitably is an adverb, and ageing is a noun

The word is used in relation with "biology", not "ageing"

(Physics (makes ageing) (inevitably (not biology)))

My take: "Physics makes aging inevitable, not biology."

I think the word is used to describe that we simply can't fix this problem with biology because it inevitably is a problem at a lower level of matter

Arguably followed by a , or -.

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