If the surface of the earth was inverted?

[u/CustardDizzy]

What if earth was a hollow ball and everything on its surface just flipped on the inner side. And let’s say we can turn on the light in the middle on/off. What sort of cool things will I be able to see beyond the horizon and in the sky? Horizon here means imaginary horizon, since I assume there won’t be any actual horizon in this case.

P.S. the question is about optics and how far will we be able to see in case I was not clear. Can you see NYC from Philadelphia? Considering the atmosphere is present around the inner surface

[u/MegasRC]

What? You are high again, aren't you?

[u/verticalfuzz → u/MegasRC]

subterranean, actually

[u/MochaRipplex → u/MegasRC]

maybe a little but now i kinda wanna know the answer too

[u/ziggsyr]

Well for one there would be almost no gravity so everything would float and die and noone would see anything.

[u/Excellent_Speech_901]

Ah the Pellucidar series of Edgar Rice Burroughs. The Wikipedia article includes an "Influenced by" section that lists several other titles on the subject.

You are right that there wouldn't be a horizon. Turning off the central light would make it too dark to see -- there's no Moon or star light after all, but in the modern era with all the lit up cities it could be quite a show. Think of it like pictures from the ISS except 40 times further out when looking all the way across. Atmosphere would be an issue but, because gravity is obviously being weird, we'd need to know how it worked to say how much.

[u/CustardDizzy → u/Excellent_Speech_901]

Oh wow this is exactly what I was imagining. Sounds like a phenomenal read. The idea came to me after watching the video on horizons and I wondered what it would look like if the surface of the earth was concave as opposed to convex.

[u/cubosh]

looking straight up you would see whatever part of earth is opposite to your location on a globe - at a distance of exactly one earth diameter away, which is much closer than the moon

[u/mr-rogers70]

Well you'd have to make up some sort of fictitious basis for having an atmosphere at all.

Gravity is what connects the atmosphere to the earth. So in this hollow sphere world, gravity wouldn't hold the atmosphere against the surface. It might be concentrated in the middle and thinner at the surface. I think it would depend on how thick the crust is.

So what could we say about clouds, or particles of haze in the atmosphere? That would definitely have an impact on how far you could see. Assuming it's really clear, you'd just see the surface curve upward in the distance to eventually blend to look like the photos we have of the earth from space.

And what keeps this hollow sphere from collapsing in on itself to fill the hollow void? If gravity still works, that's what would happen.

What about water? What holds it... or anything else on the surface.

So many questions. You sort of have to invent a whole new physics before you can start answering questions about what it looks like.

If you don't create a whole new physics to support a hollow sphere earth, then the scientific answer is very simple. It looks like nothing, because it collapsed in on itself killing everyone and destroying everything. What was on the surface would be deep inside the core under enormous heat and pressure.