Alien Scientist 49: Cosmic Crossroads and Carousels
Stephen Marshall, a former resident of Tsukuba, has been writing Alien Scientist articles for the Alien Times since 2001. Even though he no longer lives in Tsukuba, he is still a regular contributor to the magazine. Here is his latest intergalactic report.
Across far-flung corners of their Empire, the Romans built settlements with two perpendicular main streets, the cardo and the decumanus. Where these ran north-south and east-west, the local street plan could assume a cosmic significance, since latter street is aligned with the path of the sun across the sky, while the former is aligned with the axis round which the sun rotates. This implicitly assumes the Earth to be at the centre of the universe, although it does not imply that any particular provincial crossroads is.
The Romans, of course, placed Rome at the centre of the world – all roads led to Rome; and the nearby Mediterranean Sea was conceived as the ‘sea in the middle of the world’. Of course, it is natural to perceive one’s own centrality. European maps of the world typically show Europe in the middle, with the Atlantic to the left, and Pacific to the right. Meanwhile, American maps show America in the middle, with Pacific to left, and Atlantic to right. And in Japan, it is natural to place Japan at the centre. As such, an alien traveller who got lost on Earth could work out where they were in the world, just by looking at the way the world is shown on maps.
Still, all these maps tend to agree that north is at the top. This is partly because many of the first maps to have ‘global reach’ were developed in the northern hemisphere, and partly (it is supposed) because more of the land and human population is in the northern hemisphere. Of course, this is just a local cartographic convention: and an alien cartographer of Earth could easily put south at the top, and north at the base.
That said, the sense of ‘up’ and ‘down’ does have a significance beyond our own planet, since it can be related to the plane of the solar system. That is, the solar system is almost like a rotating disc, a flat plane within which the planets cycle round the Sun.
However, while all citizens of the solar system might agree to put the Sun at the centre, it still doesn’t tell us which way should be ‘up’. Perhaps if the majority of intelligent life in the solar system occupies planetary surfaces that face ‘south’, or if the first comprehensive maps of the solar system were developed not by Earthlings, but by citizens of south-facing planetary surfaces, then the cartographic convention for the whole solar system could reasonably adopt ‘south’ as the ‘top’.
(This of course also depends on whether alien civilisations accord ‘up’ the same significance as we do. Perhaps some downward-gazing or bottom-dwelling alien species might give greater prominence to the part of the map pointing ‘down’, and they might put ‘south’ at the bottom after all.)
In turn, this all assumes that ‘up’ and ‘down’ are meaningful labels for the opposing directions of this plane of reference in the first place. The plane of the solar system is usually depicted by Earthlings as being ‘horizontal’ – that is, as if the planets were rotating round a central axis, like a fairground carousel, where there is a definitely implied sense of ‘up’ and ‘down’.
But we could just as well imagine the plane of the solar system to be aligned ‘vertically’. Rather than a cosmic carousel, the solar system could be thought of as a cosmic Ferris Wheel, where the Sun is the central axle and the Earth and all the planets track vertically ‘upwards’ and round and back ‘below’ the sun again. Unlike on a Ferris Wheel, however, the ‘capsule’ that is Earth does not gradually rotate so as to keep facing one direction, but locally spins round, sometimes facing away from the solar hub of the system, and sometimes towards it. In this case, the cardo is aligned with the axle of the Ferris Wheel, while the decumanus corresponds with the track of the capsule round its circumference.
The disc-like solar system is itself, of course, embedded in a yet larger disc-like structure, the Galaxy that we call the Milky Way. This gives a further ‘plane’ by which we could orient ourselves. From this galactic perspective, the solar system is, after all, just a far-flung province. But, however widely we gaze into the night sky, we can still stand at our local crossroads, and imagine all the stars and galaxies are whirling round us.