Ultimate limit

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List of ultimate technological/physical limits

Limit to tensile strength (and to spinning stuff fast)

Tensile strength of material faces ultimate limits.
It is not possible and will never be possible to
go way above the tensile strength of diamond nanofibers and carbon nanotubes.
If something where to be stronger (beyond the bounds of currently known physics), then it would need to be something very different than our known chemistry with atoms of the periodic table.

A collary of the ultimate limit in tensile strength is the unsupported rotating ring speed limit which says that:
It is not possible and will never be possible to
rotate an usupported ring of matter (made from atoms) at speeds way above 3km/s without it rupturing from centrifugal forces.

Limit to energy density

Chemical energy density (energy per volume and energy per mass) faces ultimate limits.
It is not possible and will never be possible to
go way above the power densities of rocket fuels.
If something chemical where to be more energy dense dense (beyond the bounds of currently known physics), then it would need to be something very different than our known chemistry with atom of the periodic table.

Well we have that very different thing now. That is nuclear energy.
And it was quite surprising when discovered.
Unfortunately termonuclear energy conversion comes with quite some restrictions.

  • It is one way only. Storing excess energy in nuclear seems not possible.
  • It inherently needs macroscale conversion devices (and quite big at that)
  • Efficiency seems limited to Carnough cycle efficiency limit. There may be room for some improvement here ...
  • (The known risks and challenges of nuclear power are just that. They are not fundamental limits.)

Nuclear energy density faces ultimate limits too.
It is not possible and will never be possible to
go way above the power densities of hydrogen nuclei.
If something where to be more energy dense (beyond the bounds of currently known physics), then it would need to be something very different than our known nuclear physics.


Here's a paper by Robert A. Freitas Jr. on energy density in APM systems:

Limit to density of mass

Mass per volume density of materials faces ultimate limits.
It is not possible and will never be possible to
go way above density of say osmium metal.
If something where to to have more density of mass (beyond the bounds of currently known physics), then it would need to be something very different than our known chemistry with atom of the periodic table.

It would be rather surprising though:
Even for nature there seems to be a huge inaccessible gap in densities between atomic matter and neutron star matter. Nature can cross that density range only transiently in a non stable way during stellar collapses.

No! Nothing is absolutely impossible. Everyone wo says so is wrong.

In this regard there seems to exist an almost religious group mindset in society.

Yes, indeed, nothing is ever impossible with absolute certainty. BUT ...
Many things (lets call them X) are:

  • (1) either known to be astronomically unlikely
  • (2) or simply unknowable and not even yet intelectually approachable in any sensible way
  • Unknowable errors regarding X made in (1) (that is: errors that make X unexpectedly much more likely than expected) fall into (2).

Whisful thinking vs Exploratory engineering

The point is:
Speculating about these way different things that would be very surprising if discovered (but no discovery, no matter how surprising, can ever be excluded with absolute certainty) when there is still absolutely no clue yet where to even start looking is a very pointless and unproductive activity (except it's done for jelly soft SciFi entertainment purposes).

This "eveything is possibe" whisful thinking mindset
is in stark polar contrast to the stringent exploratory engineering methodology.
There one picks only problems where there are aspects that are exceptionally well amenable
to analysis via well established formal methods and models. And as a product one gains:

Some related philosophical ponderings

To prove the absolute impossibility of something one would need a complete and consistent formalized description of everything.
A complete and consistent formalized description of everything is absolutely impossible though.
At least we know from math (incompleteness theorem) and we use math do describe physics.

Now we have a paradox which illustrates the point of the pointlessness of trying to think about stuff X
that cannot yet be thought about because its completely beyond all our horizons.

So by pulling its own rug does the incompleteness proof disproof its own validity? Or rather does it make itself into an completely information devoid statement? Fundamentally unanswerabel questions I guess?
But if we'd assume that it does break itself then so may go all the other math we have out the window. And (suprise, suprise) we totally can't have that. Math is ways too useful for actual practical purposes. We can't scrap math (and physics) because we refuse to put faith upon its axiomatic fringes just in order in to indulge in pipe dreams of wishful thinking about X being maybe possible after all. That's only ok for soft fantasy SciFi for entertainment. Not for actual technology proposals.
Ignoring known math and physics in order to dream about X being possible is useless because
sensible development directions cannot be determined distilled and pursued.
Fantasy SciFi for the purpuse of stirring human emotions is a different story.

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