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(First time posting on worldbuilding, be gentle!)

For reasons currently unimportant, Earth has been encased in a solid shell which is for all intents and purposes completely invulnerable. The shell cannot be damaged by (for example) meteor strikes or large explosions, and does not allow radiation to pass through it in either direction. By this I mean electromagnetic radiation (including light), and heat. All such radiation is reflected by the inner surface of the shell. The shell appeared in a relatively short time, taking a matter of days or weeks to be placed around the planet.

Assume that through some means the shell remains steady about the Earth and there is no chance of it drifting and colliding with the planet. It is positioned high in the atmosphere, somewhere in the exosphere (roughly 600-700km up). If this conflicts with any existing satellites then they can be assumed to have been destroyed. Then my question is:

How would this affect the climate?

Specifically: without the sun, would there still be wind and other types of weather? How would the temperature be affected over time?

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    $\begingroup$ Congrats on killing all life on Earth with your first question! (Also, welcome to the site.) $\endgroup$ – Frostfyre Aug 23 '16 at 20:06
  • $\begingroup$ Good question for a first go. 2 things to expand....does this sphere simply instantaneously appear, or is there an associated construction time? and second...weather only, or do we care about impacts on life? $\endgroup$ – Twelfth Aug 23 '16 at 20:08
  • $\begingroup$ What, specifically, do you mean by radiation? For example, are you considering light radiation? When the sphere is struck by radiation, is it reflected, absorbed, or some portion of each? Bearing in mind where the "atmosphere" ends and "space" begins is a fairly gradual change, what is the distance of the shell from the Earth? $\endgroup$ – Azuaron Aug 23 '16 at 20:18
  • $\begingroup$ Edited to answer most of those questions: with regards to the impacts on life, I'd be interested to hear any input but I wasn't sure if that would be too broad a question. $\endgroup$ – Uzai Aug 23 '16 at 20:34
  • $\begingroup$ This would be interesting to view from the international space station in low orbit at ~400 km altitude $\endgroup$ – Josh King Aug 23 '16 at 20:42
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Without sunlight, all photosynthesizing plants would die. Then all animals would die a little while later. Most fungi are dependent on the presence of energy-rich (decaying) plant matter, so they may thrive for a long time and then die out after exhausting their food source. It's unlikely that anything other than bacteria can switch their energy source to new chemical sources, leaving only a bunch of bacteria and a few isolated cave-dwelling populations. The composition of the atmosphere will change due to the rotting of all that dead stuff and the bacteria thriving on it. However, due to the lack of sunlight, this will not affect things greatly anymore.

Without day and night, winds will mostly cease (no more thermals, only a slight breeze from oceans currents at most). The ice caps will slowly melt, equalizing the temperature across the globe, thus stopping most ocean currents. The planet will become very still and mostly covered by water. Over many thousands of years, the remaining bacteria will evolve to a new balance, resembling a ridiculously huge cave. If you're lucky, some of the cave-dwelling animals manage to survive on the surface and spread out a little, but most of the planet is likely too toxic for them, since they evolved in very fragile environments, and even those caves might have been dependent on oxygen-containing water coming from the surface.

A few thousands to millions of years more will see rising temperatures as the heat from the planet's core slowly spreads now that the planet is not able to radiate its heat anymore. This is estimated at 43-47 Terawatts over the whole planet, both from radioactive decay inside the planet and primordial heat left over from the planet's formation. It's a tiny amount compared to the energy the Earth used to receive from the Sun, but it builds up over time. In the end, you'll have a scorching hot cave with maybe a few extremophile strains of bacteria left.

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  • $\begingroup$ Since you mentioned the effects on plant life, would fungi also die out or would they be able to survive (at least initially)? $\endgroup$ – Uzai Aug 23 '16 at 20:38
  • $\begingroup$ Updated the answer to address both comments. $\endgroup$ – Cyrus Aug 23 '16 at 20:54
  • $\begingroup$ Forests have huge impact on climate. Cyanobacteria as well, or had. Humans have some, too. So them dying is climate related. $\endgroup$ – Mołot Aug 23 '16 at 20:56
  • $\begingroup$ comment removed as it's no longer valid and +1. The only addition I could make is the sphere would reflect the infrared coming off the planet...the ocean will absorb that a bit better than the land making a very mild heat difference and a very low wind. $\endgroup$ – Twelfth Aug 23 '16 at 20:58
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    $\begingroup$ @Molot: After writing the answer, I realized all those effects are due to the interaction with the Sunlight. Absorbing a tiny bit more or less of that 174 Petawatts coming in and you change the climate. Once the shell is in place, they mostly affect the smell of the planet, I guess. $\endgroup$ – Cyrus Aug 23 '16 at 21:02

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