Last week I was asked by someone about weightlessness and it sparked a curious train of thought. A body travelling around the Earth will be in orbit if its velocity is given by v^2 = rg. What if this occurred not in space, but at sea level? A velocity of sqrt(6.4E6 *9.81) = 8km per sec (Mach 24) would be hard to achieve due to air resistance.
Today’s invention is therefore a pipeline joining cities which are far apart. This is in the shape of a perfectly circular arc bolted to the ground and made of sections of pipe which are sealed so that the whole pipeline can be evacuated.
Airlocks allow a capsule to be inserted and a series of external railguns accelerates this to huge velocity (and brakes it again at the far end).
During transit, the capsule will experience microgravity (possibly useful for in-transit materials processing). This arrangement would allow a small payload of cargo to get from New York to Melbourne in 35 minutes.
(Suddenly opening the downstream end would provide a way to inject satellites into a higher, conventional orbit).