I am looking for the ways to allow humans with technology that allowed them to colonise the entire galaxy (150 thousand light years wide) to avoid the negative side-effects of tanning (premature aging and skin cancer) while also being able to darken their skin by sun-bathing with aid of technological and/or biological means in a real-world accurate manner.

The setting:

  • Faster-than-light travelling and communication.
  • Medicine that can cure virtually any modern disease.
  • Powerful yet controlled general artificial intelligence.
  • (Available but expensive) Extensive nanotechnology.
  • (Available only for the wealthy and regulated by law) Well-studied and safe genetic engineering.

My solutions so far

I do not think genetic engineering fits me because while it certainly looks like the obvious solution, its use is heavily restricted by the law and it's so expensive that only the upper class can afford it, meanwhile I am looking for a generic solution for the problem that would work for anybody out of the box. Hence these are a few ideas I had so far:

Ultra-violet lenses

The concept is to create an equivalent of Dyson sphere around a planet that will host a large mirror. When the starlight will pass through it, it would be shifted in a way that would still raise the reaction of skin darkening but would not deal damage to cells. In the interstellar economics, this will be possible to do, although only well-recognised tourist planets could afford building it and use safe tanning as a market advantage.

  • Is this biologically realistic?
  • If yes, is it feasible to create glass that could shift light in this way from the materials found in Andromeda-sized galaxy?

Tanning cream

This will be special cream that people would be supposed to cover their skin in before sunbathing in a similar fashion we do in reality. The cream in question would block the effects of ultraviolet on the skin completely and while receiving sunlight, it would undergo chemical reaction that would make it sink in human skin and change its colour. On the surface it sounds like a more probable, effective and cheaper solution that could be more commonplace unless it would raise allergetic reaction to one of its components.

  • $\begingroup$ Question: If you have Medicine that can cure any modern disease - why would you worry about the Cancer Risk? Such advanced Medicine would include a cure for Cancer - so why worry? $\endgroup$ Commented Jan 28, 2023 at 21:13
  • $\begingroup$ It's prevention reasoning. You could cure skin cancer, but you still get and it may be painful or have grater long-term consequences, which will make it easier to avoid it in the first place. $\endgroup$ Commented Jan 28, 2023 at 21:26
  • $\begingroup$ How tanned is tanned, what do you mean by healthy, etc .. what is "healthy" with regards to sunlight is far too often a matter of degree, opinion, fashion, personal taste and even (for baseline melanin levels) your ethnicity, given too little sunlight and you'll have a vitamin deficiency and 'too much' while not unhealthy in and of itself risks skin cancer .. any answers are more likely than not going to rest on opinion, character decisions and story. $\endgroup$
    – Pelinore
    Commented Jan 28, 2023 at 21:53
  • 1
    $\begingroup$ I'm a little confused by the economics of a question where genetic engineering is too expensive and heavily restricted, but a gigantic glass dome over your planet isn't. $\endgroup$
    – Cadence
    Commented Jan 28, 2023 at 23:49
  • $\begingroup$ @Cadence You might as well compare what the janitor at a company can afford and what the company he works for can .. the personal finances of most normal individuals has absolutely nothing to do with what a society can afford, I can't afford a packet of crisps some days yet, somehow, amazingly, my country has nuclear subs .. so, do you see? no connection. $\endgroup$
    – Pelinore
    Commented Jan 29, 2023 at 0:15

1 Answer 1


Intradermal nanites.

nanopartcles in skin

Human Dermis as a Target of Nanoparticles for Treating Skin Conditions

Your future people have nanobots in their skin. These nanobots can do several things and one of them is change color, which then changes skin color. A wide palette is possible by having adjacent nanobots in the skin be different colors, much as pixels on a screen combine their colors to produce the desired end color. Reflective metallic skin is also possible. The nanobots can be programmed to cycle through changes so a person's skin changes with time over days, hours or seconds.

From my answer to this question: What colors could a pool of nanorobots be?

nanoparticle silver

Nanosilver rainbow: a rapid and facile method to tune different colours of nanosilver through the controlled synthesis of stable spherical silver nanoparticles†

The same particle can be lots of different colors by changing its size. Your dermal nanites can change their size according to signals they get or a previously downloaded program they follow.


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