Simplified, Earth's systems can be broken up into four "spheres" that constantly exchange matter and energy with one another:

  • The atmosphere, which includes all gasses around the planet
  • The hydrosphere, which includes all of the planet's water and related systems
  • The geosphere, which includes the all the material within and below the crust
  • The biosphere, which is comprised of every living thing on Earth

We have , but why is it that the other 'spheres' do not have tags?
I suggest we make them, but some peer review would be nice.

"For questions about the gases which surround a planet or some other celestial body."
Current tag wiki. I think it's fine as-is.

"For questions about the liquids present on the surface of a planet and the associated systems."
Note that this is not synonymous with any other tag - in fact, very few tags cover this topic at all, yet multiple questions do (things like alien solvents and biochemistry, some weather patterns, erosion and landscape formation, chemical processes, and more). Examples include:

Can a water cycle exist on a planet without oceans?
Could water be extracted/harvested from clouds?
What's the quickest way to add oceans to a planet?
Could humans survive on a planet with only deuterium 'heavy water' made with hydrogen isotopes?
How rare is (clean, drinkable or useable) water in the solar system?
What would the conditions on a methane world look like?
An ammonia - not water - based alien race that breaths hydrogen
Could liquid silicon dioxide exist on the surface of Venus?
Eutectic Iron Life
Methanol/Ethanol (other alcohol) based life-form - aliens?
What conditions are necessary to support a vitriolic chlorine planet?

"For questions about the materials that compose a planet or other celestial body."
Related to and possibly synonymous; would be relevant to a plethora of existing questions that do not have the tag. Examples include:

What would the geology and climatology of an earth-like planet be if it's north pole is always facing it's star?
What geographic features occur at each type of tectonic plate boundary?
Can we breathe the moon's crust?
Alien exploration : drone digging earth crust
How much energy to destroy the crust of a planet?
How would the earth be different if the crust was at most 1km thick?
What happened when my scientist drilled a hole through Europa's “crust”?
What would perforating a continent do?
Will there be any effect on earth or an oceanic world if its crust and mantle lack radioactive elements?
Planet with dual core
Could We Restart Mars's Core With Antimatter?
Can an asteroid have a molten core?
Likelihood of a magnetosphere with a mercury core
What would happen at the core of a water world?

"For questions about the ecological dynamics of a whole planet or celestial body."
Broader than ; related to the seldom-used ; more specific than ; more specific than . Examples include:

If we built a large moon close to Mars, could we make Mars a living world?
Ecocide with a clear deliberate intent
Could a hollow rocky planet the size of Jupiter be artificially created, and how would that affect species growing on its surface
Finding signs of life from afar
Would you shoot out DNA onto baby planets if you planned to visit it someday?
Could exoplanet with Earth's magnetic field orbiting a binary star system harbour intelligent life?
Can there be life on a planet with water, but without an atmosphere?
Nanobots Ecosystem, is it possible?
What if an Earth-like planet had no axial tilt? (impact on ecosystem)
Ecosystem of bladetree
How could you keep a rogue planet warm(ish)?
Would animals from Earth be able to survive and reproduce on this planet?
What would happen if there was no wind?

So what do you think? Are these tags relevant and/or reasonable? What changes would you make to them?

  • $\begingroup$ Could you edit in links to some of the existing questions that you think should have these new tags? Thanks. $\endgroup$ Dec 1, 2016 at 1:14
  • $\begingroup$ Sounds like meta tags to me. $\endgroup$
    – Vincent
    Dec 1, 2016 at 1:25
  • $\begingroup$ @MonicaCellio Done, although more posts are probably applicable under each tag $\endgroup$
    – Zxyrra
    Dec 1, 2016 at 1:57
  • $\begingroup$ @Vincent Could you elaborate? (Potentially in an answer to this Q) $\endgroup$
    – Zxyrra
    Dec 1, 2016 at 1:57
  • $\begingroup$ @Zxyrra thanks. I wasn't asking for an exhaustive list; just some representative samples. (Also to make sure there are some for each, because you can't create tags in advance of having questions for them.) $\endgroup$ Dec 1, 2016 at 2:07
  • $\begingroup$ What I mean is that we already have tags for hydrosphere (on the top of my head) river, water-bodies, ocean, underwater...If we created the hydro tag it would serve only to encompass already existing tags because it is pretty broad to begin with. $\endgroup$
    – Vincent
    Dec 1, 2016 at 3:49
  • $\begingroup$ @Vincent Only "water-bodies" "underwater" and "ocean" exist; ocean has a single item. None of those encompass things like solvents, erosion, weather, chemical processes - for which "hydrosphere" would eliminate the need for multiple new tags. Additionally it's exactly as broad as atmosphere, which seems to work fine - "too broad" doesn't really apply to tags. $\endgroup$
    – Zxyrra
    Dec 1, 2016 at 4:06

1 Answer 1


Yes. That's what tags are for

There isn't anything wrong on creating a tag. Tags don't bite. Even the reputation needed is really low (200). Tagging something with isn't as good as , which are both sub-tags. This makes the question interface in the questions tab clearer.

For example, on Arqade (gamaing.SE), for example, the average tag has ~10 questions, with half of the tags having a single question. That's because 1 game = 1 topic. And the main thing is, it doesn't mind. It's better to have 10 (or 100) narrowly-scoped () tags rather than 1 big one .

So, community, if you have enough reputation, go out and create tags! And don't forget to re-tag where needed!

  • $\begingroup$ I agree that this is what tags are for but I'm most interested in making sure there's no problem with these particular tags - that they have an adequate scope, that they have good descriptions, etc. $\endgroup$
    – Zxyrra
    Dec 3, 2016 at 14:20
  • $\begingroup$ @Zxyrra The name of the tag is usually self-explanatory. If it doesn't have an adequate scope, it will get edited out of questions and/or won't be getting new questions, and will soon be removed. The description of the tag isn't a crucial feature, though. $\endgroup$
    – user22613
    Dec 3, 2016 at 15:15
  • 1
    $\begingroup$ Adding to this: When creating a tag, please take a moment to create a brief tag wiki excerpt that describes when to apply the tag. Tags with only a single or a few questions and no usage guidelines at all can be more confusing than helpful, and the person creating the tag is usually in a good position to at least propose a tag wiki at the same time. $\endgroup$
    – user
    Dec 16, 2016 at 20:59

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