Impossible
Nothing is absolutely impossible. Well yes, but that is not practically relevant.
What is practically relevant is that many things are for all practical purposes (FAPP) impossible.
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Impossibility in the context of technologies
The first of Clarke's three laws:
"When a distinguished but elderly scientist states that something is possible, he is almost certainly right.
When he states that something is impossible, he is very probably wrong." (he or she or they to be modern and inclusive).
This is just an informal law though and one not to take too seriously.
Differentiating between types of impossibility claims
There is something beyond Clark's first law.
While statements about absolute impossibility will always remain impossible.
One can distinguish between
- impossibilities that will require very very surprising fundamentally new discoveries to eventually become possible and
- impossibilities that are just assumed by people because all obvious trivial self suggesting solutions to getting there lead into dead ends.
In case of the latter it may be that certain critical aspects of the target technology
can be quite reliably reliably predicted despite that these aspects are not yet directly experimentally testable yet.
E.g. A (warmed up) tennis-ball shooting machine will with FAPP absolute certainty work very much as expected on Pluto
despite not at all being scientifically testable there at the eventual intended target operating destination.
Note that this is not dismissing the scientific method (and entering crackpot territory).
The relevant tests just have already been done in a similar enough context.
Exploratory engineering exclusively uses solidly established textbook physics.
And that with large safety margins.
People nonetheless tend to dismiss technologies as nonsense despite them being clearly amenable to
feasibility analysis via exploratory engineering. Which can be detrimental funding and research.
Impossibility wrongly assumed due to naive approaches leading to dead ends and other reasons
Advanced atomically precise manufacturing. Specifically:
- Claims of macroscale style machinery at the nanoscale (in gemstone metamaterial technology) being impossible
and claims that this idea is showing lack of understanding about physics - Claims of piezomechanosynthesis of diamondoid crystolecules being impossible
Examples of impossibilities that would need very very surprising discoveries to be proven false
- Stable matter that is much more dense than osmium (the densest chemical element) but less dense than a neutron star
- Femtotechnology building femto-robotics out of nucleons is for all we know impossible
- Star Treck like beaming of human meatbag bodies. Several impossibilities with that.
- Nanoscale, microscale, or mesoscale very very small nuclear reactors (nucleo-XYZ energy conversion) … most likely impossible … would be nice if not
Impossibility in the context of likelihood
A good example are the molecules in the air in a human scale room.
There is a finite chance (not too difficult to calculate) that all molecules just by mere chance gather in one half of the room
leaving the other half completely empty as a vacuum. Practically this will never happen in the time the Earth exists or even the universe does.
Different story for very very small rooms.
Heat always equilibriates and chaos always increases (rising entropy). Second law of thermodynamics.
This is only true for large scale systems though. For rooms small enough this can and will be violated.
Still perpetuum mobile of second kind remain fundamentally impossible possible.
You can't detect a nanoscale Poincaret recurrence and then extract the energy.
You will expend equal or more energy doing the detecting that what you gain harvesting the recurrence.
Read up on related topics of Feynman ratchet and Maxwell demon if you're new to these concepts.
Related: Poincaret recurrence
Sometimes assumed impossibilities regarding probabilities that do not actually hold
- PPV piratically perfect vacuum in macroscale volumes.
Albeit with today's technology completely impossible, with future atomically precise technology this should be rather easy to achieve. - A for practical relevant scales false claim:
The tendency towards equilibrium in thermodynamics makes it impossible to have every atom in a product at exactly the desired location.
Yes, Macroscale products will receive and accumulate damage from cosmic radiation. But for smaller structures where this is relevant the claim is false.
Related
External links
Wikipedia:
