Would it be physically possible to construct a lens that could see beyond the horizon?

Question

This may or may not be a completely absurd question, but I was just thinking about it.. Is it possible to construct some kind of lens whose design is set to "cancel out" the curvature of the earth?

A practical example: if I were lost at sea, and looked through a special pair of binoculars constructed with these lenses, I could see what the land will look like past the horizon, and therefore be able to spot land from further away.

Any ideas?

Answer 1

It is possible to see over the horizon. In fact if you consider the horizon to be defined by a straight line from your eye to the edge of the earth we can almost always see over the horizon.  This is because the atmosphere tends to be more dense near the surface of the earth than it is higher and light is refracted toward higher density air.  

The refraction in the troposphere is nearly independent of wavelength in the visible spectrum.  But imagine that there is some wavelength that the atmosphere diffracts much more strongly, or that the ionosphere reflects back toward the earth.  One could build a device that detected those wavelengths and thus see further over the horizon.  In fact, this is done with over the horizon radar, which frequently can "see" half way around the earth.  Ham radio operators are also able to "see" great distances around the earth.

So, in a general sense it is possible to do what you suggest.

Answer 2

If you want to cancel out the curve of the Earth (for example, you're in the US and want to see Europe) this would be impossible because light travels in straight lines. A lens can only bend light to focus on a certain point. Light from Europe cannot curve to reach America.

Answer 3

Yes.

Radio waves reflect off the cloud cover, also from an ionized layer of the atmosphere and could be used in a radio telescope arrangement.

Visible light does the same and sometimes causes a mirage of a city or other forms from beyond the hoizon.

I'm not sure how you could construct your viewer but it is possible.