It seems that no one can live forever.

Is there anything that can rightfully be called "immortality", which is both desirable and a genuine response to the problem of mortality?

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    I think the answer to the problem of mortality is that the problem of immortality would be much (much!) worse. Not that I wouldn't mind a couple thousand extra years. – Dan Bron Feb 25 '15 at 11:53
  • ok it's not a very good question anyway – user6917 Mar 1 '15 at 3:00

The challenge is defining "immortality."

One must be careful in defining it as "something which does not change." The only way to manage that is to (a) defeat thermodynamics and (b) remove onesself from everything governed by thermodynamics. This basically means you have to discover something we believe to be impossible, and remove yourself from everything that isn't you. That's a really high price to pay. You literally could not have any influence in the world, or you would be subject to thermodynamics yourself. Worse, if you judged wrong, and actually were still under the effects of thermodynamics, you would have removed yourself from anything else in the world that could potentially teach you how to truly overcome it!

If we shift viewpoints a bit, we could look at eigenvectors of the time function. Eigenvectors are a neat thing that show up in linear algebra. They are a value, call it X, which when thrown through a particular transformation, result in a value which is kX, where k is some real number. For values which are not eigenvectors, the result is never so easy. This provides an interesting potential definition of immortality, because the "flavor" of X remains, as long as k is nonzero.

If you could find the "time function" which governs the rules of the universe as time progresses, you could identify the eigenvectors of that transformation (assuming it is linear. QM assumes it is linear, and there are equivalents for eigenvectors in non-linear systems, they're simply harder to talk about). As long as you always ended up with a non-zero k constant, the "flavor" of your eigenvector could remain forever.

I wont go into the math, but if you make the huge assumption that the world is a linear system (which particle physics seems to suggest, but it's a big leap to go from particle physics to life philosophies), you find that these eigenvectors must actually reveal themselves as rotations. The only non-rotation term allowed by this linear system is a vector of magnitude 1. However, this acts more space-like, and less time like; less like "immortality" and more like "omnipresence."

Thus, if you see anything which holds fast, and tries not to rotate in any way, either it is not immortal, or the world is nonlinear.

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  • +1 for identifying the thermodynamic impossibility of true immortality. No such thing as a perpetual motion machine, even a bipedal one. – Dan Bron Feb 25 '15 at 16:49

The human body is a very complex machine. In principle, when it is damaged that damage can be undone provided that we know about the damage and it hasn't gone too far. At present, the technology required to do this doesn't exist. If it did, then your body could be kept alive indefinitely in a youthful state. That means there would no upper bound on how long you could live barring accidents and murder. I don't know whether you would want to call that immortality.

A researcher called Aubrey de Grey has come up with an idea about how to repair age related damage before it goes too far that he calls Strategies for Engineered Negligible Senescence (SENS):


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  • I think this answer ignores broader physical realities like , say, the inevitable heat death of the universe. Or the fact that the hypothetical machine which maintains and repairs the human body itself would have to be maintained and repaired (and the system which maintained and repaired that would, in turn, have to be maintained and repaired...). Or the implications of indefinitely extended the lifespan of a system which was designed (through evolution) to last less than a century (think: packing centuries of memories and thoughts into a mind with a capacity for decades). – Dan Bron Feb 25 '15 at 12:53
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    In other words, I don't think you've thought through what actual, literal, immortality means. – Dan Bron Feb 25 '15 at 12:55
  • Whether heat death will happen depends on details of cosmology that we don't currently, e.g. - we don't know what dark energy is. So the alleged heat death doesn't decide the issue one way or the other. There is also no particular reason to think that adding memory to your brain is impossible. And in substance we do this already with books and computers. – alanf Feb 25 '15 at 13:26
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    I think you're missing the broader point, but let me address the two specific rebuttals you've made first: no, we do not know what dark energy is, but we do know it exists, because we observe that space itself is expanding, and the rate of expansion is increasing. In other words: dark energy, whatever it is, is ensuring that all matter will eventually be so far separated that individual particles will be separated beyond their mutual light cones and therefore be utterly started for all time. In other words: eventually, structure, of any kind, will be impossible. – Dan Bron Feb 25 '15 at 13:29
  • Since we don't know what dark energy is, we don't know if it will make the expansion continue or not. For example, it is unclear whether or not the expansion will continue indefinitely in the timescape model: arxiv.org/abs/1311.3787. – alanf Feb 25 '15 at 13:33