If the earth was flat...?

Ah. So that Dyson Sphere in the now-classic Star Trek:TNG episode had artificial gravity on its interior surface?

Ah! Good to know. I’m not up on my Niven.

It had to. This is a big flaw with the so-called “Dyson Sphere”–without some kind of gravity drawing down (away from the star it contains) the atmosphere would just disperse, and in fact a failure of a gravity generator (assuming they are distributed across the surface of the shell) would result in atmosphere jetting out away from the surface. Let it be noted that Freeman Dyson’s original proposal had multitudes of individual habitats orbiting the star at a variety of orbits creating a virtual shell, rather than the less practical single monolithical construct that has come to be associated with the term. The point of either type is to create a surface that absorbs essentially all of the radiation from the star. It was Dyson’s proposition that an extremely advanced civilization would have to build such constructs in order to provide sufficient energy and would therefore be invisible to our astronomical efforts to locate extrasolar civilizations.

Of course, as we all know, the Ringworld is unstable! :smiley: A ringworld is not gravitationally centered on the star it ostensibly orbits; in fact, as a rigid structure, it isn’t in orbit at all, and any planar displacement relative to the star will cause it to fall inward with positive feedback. Any lateral movement (along the axis of its rotation) will result in oscollatory movement with the ring hoping from one side of the star to the other (from the star’s point of view), and attendant precessive and nutational modes also result in progressive imbalance. In short, a ringworld (about a star) is really not a good idea.

The ringworld concept has other problems as well, not the least of which is that the tensile strength of the material for a stellar-size ringworld is many orders of magnitude stronger than any concievable material. Niven circumvented the problem by creating scrith, a material that blocks 40% of neutrinos and has a tensile strength similar to that of the residual strong force but acting over atomic, rather than subnuclear, distances, which is a neat trick you can do if you happen to be a science fiction author who can make up physical laws as you go along.

Back to the flat Earth; you could actually make the material rather thin (conservatively, about .25μm) if you could make it out of neutronium…provided, of course, that you could find some way to make it stable, rather than have it explode via degeneracy pressure or collapse into a quark-gluon quagma. Og help you if you get a ripple, though.

Stranger

I once read that World War I was the first conflict which had to take account of the shape of the planet. Gunners early in the war found themselves overshooting their targets. What was happening was that the range of the guns had become long enough that the curvature of the Earth had become a factor that the gunners needed to compensate for.

How can YOU tell if the earth is round?

Say you’re in Germany at noon: call someone in the USA and they’ll tell you the sun is rising, call someone in Japan, and They’ll tell you the sun is setting.

Time Zones on a sphere…how can that be reconciled with a flat disc?

Since this thread is still open I’ll add a little to this. Actually we have no immediate visual signals that the earth is anything but flat. The items on the list above are clues that have to be interpreted in light of our knowledge of geometry and astronomy. The only immediate visual sign of a spherical earth is from space.

So I’ll take back about 30% of my hasty and craven admission of error but leave 70% of it intact.

Don’t bother me with facts. My mind is made up!

Since the subject of Ringworld and flat worlds has come up, I thought I’d mention the Alderson Disk.

Warships had to navigate properly in many conflict prior to WWI. To do so when out of sight of land, they often used celestial navigation which certainly takes account of the generally spherical shape of our planet.