If standing just south of the equator, you are in the southern hemisphere. Certainly Sweden would be visible at sufficient altitude in this interpretation.

Obviously. The height would than be Earth radius 6378 km, if I am correct. But the question clearly states "from let's say South Africa":)

I was hinting at the fact that say Pretoria SA is at 25.75 S lattitude and will not be hidden from a sufficiently high Sweden, because it is closer to the equator than Sweden.

Your picture suggests you cannot see the ground a kilometer from you on a flatland. This is, of course, false.

@GaryWalker Which is confusing, because distance to the equator is irrelevant (unless you are looking from the equator). What matters is that the difference between Pretoria, South Africa and Flataklocken, Sweden is less than half pi radians (ninety degrees, a right angle). This is because the center of Sweden is at 62 degrees or so and Pretoria and Union's End are are about 25.75, giving 88 degrees. So your observation (that Sweden would be visible from some part of South Africa eventually) is correct but the reason that you gave is incorrect.

@Mołot Only because your eyes are close to two meters above ground. Dig a hole such that the tops of your pupils are level with the ground and you won't be able to see a kilometer away on flatland. For seeing the floating Sweden, the two meters won't matter much, particularly as you are unlikely to be on perfectly flat ground with no trees, grass, or other obstacles.

@Brythan OP asked about it being seen from South Africa. With no additional reservations we can safely assume normal observer, of average height. For seeing Sweden two meters matter a lot, see my answer for details. These 2 meters make it possible, not in atmo but possible.

Mołot: The average human height won't change anything, so I have neglected it.

others: yes, from the northern part of South Africa there is a height in which Sweden would be visible, but it still is way above atmosfere. I admit to just like the answer "no" better than searching a place to make it work. Btw. the calculator in the second answer does not work indefinitely, specifically not after ninety degrees (not enough reputation to comment there).

Corollary: if you’re in South Africa right now, Sweden may have already snuck away and you’d be none the wiser.

But the Earth turns...

@DJClayworth But floating Sweden is in a geosynchronous orbit.

Mafadi Peak in SA is about 3450m high.

to add to your very sophisticated visualization: the stars in the northern hemisphere are both larger than Sweden and rather far away; you still can't see one in the direction of the arrow when standing on South Africa. The distance doesn't really change anything. To be sure, I am sending this from Sweden, currently located in the stratosphere

This also gives part of the answer to the second part of the question: How 'long' floating New Sweden would have to be to be visible from SA. The length from Sweden to SA tangent line.

This answer does not take into account that the atmosphere is refractive: the path you can see actually curves down - for example, when you see the bottom of the Sun touch the horizon at sunset, the bottom of the Sun is actually about 8°-10° below the horizon. As such, taking the latitude of Stockholm (59.3°N) and Cape Town (33.9°S) and observing that the difference is merely 93° (i.e. less than 98°), we prove that by the time Sweden reaches 1AU, it will be well within viewing angle. This is also related to why the Sun seems to "widen" at sunset

never .. hand to forehead ..

@Chronocidal: Refractivity of the atmosphere is a great point which changes the answer substantially, and which no other answers currently address! Why not make it an answer?

While this answer is totally correct, there is a wildly simpler way to explain the issue. If you're on the other side of the Earth from Sweden you will (obviously, duh) never see it. This whole QA can be answered in a few words.

This is a great analysis for points that are around 90° apart or more, but the true numbers lead to the opposite answer. The southernmost point in Sweden is at 55° 20' N, and the northernmost point in South Africa is at 22° 7' S. The distance between them is 77° 27', so flying Sweden is visible from South Africa.