A roadhouse on the Stuart Highway in the middle of the Northern Territory — fuel, a campground and a pub — which has declared itself Australia's UFO capital. Reports have come from here since the 1940s, when an army camp stood nearby, and never stopped. The owners have taken an enterprising view: the walls are painted with green figures, models stand at the door, and the bar keeps a folder of cuttings and a book for visitors to write down what they saw. The honest part of the explanation is the sky. This is some of the darkest, clearest air on the planet, satellites and fireballs are visible to the naked eye, and the route to Pine Gap — the joint American-Australian facility, about whose work little is known — passes nearby.

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The Hudson Valley and the Silent Triangle

Between 1982 and 1986 the Hudson Valley north of New York City produced several thousand reports of the same thing: a very large triangular or boomerang-shaped object with lights along its edge, moving low, slowly and almost silently. The witnesses were suburban residents, police, and staff at the Indian Point nuclear station. Part of the wave is explained and undisputed: a group of amateur pilots from Stormville airfield flew in formation at night with their lights on as a prank, and never denied it. The argument is whether that covers all of it: several reports describe an object blocking hundreds of metres of sky, which is large for a formation of light aircraft.