Time travel has been a favourite subject for writers ever since HG Wells wrote The Time Machine. However universally overlooked is the fact that the Earth is moving rapidly through space, which presents a would-be time traveller with an awkward problem.
Even while sitting idle contemplating how to make a time machine, you're on the surface of the Earth which spins on its axis once per day. At the beatitude of Canberra, you'd be travelling at 1450 km/h.
If you could jump just one second into the future, you'd reappear 40 metres west from where you began. The embarrassment of finding yourself in a neighbour's bathroom would be the least of your concerns.
If you were unlucky enough to arrive in the space occupied by a mountain, your satisfaction would be short lived as your body tries to share space with a hundred kilos of rock.
While the resulting near doubling of density in that space wouldn't be enough to convert you into a mini neutron star or probably not even a nuclear reaction, it would obviously be fatal.
It would, however, trigger an almighty explosion. Seismographs around the world would register an unusual signal, perhaps causing an astute geologist to observe "...another time traveller."
If, however, you did manage to arrive in clear air, that space is already occupied - by air - in which case you'd at least cause a very loud bang.
Or maybe you'd arrive in the vacuum of space, but that of course presents a few problems of its own.
If that sounds bad enough, the rotation of the Earth is only one vector of motion you'd need to consider because our planet is also orbiting the Sun (at 107,226km/h), which is in turn is orbiting the galactic centre (at 720,000km/h).
Then the galaxy itself is travelling at 40 kilometres per second toward the centre of a cluster of galaxies called the Local Group. Inside that we're heading towards the Virgo Cluster at 600 kilometres per second.
Even though it all adds up to a prodigious velocity, the numbers are fairly well known and therefore your planned landing spot could theoretically be calculated.
As a cunning reader, you ask whether the problem is solved if your departure velocity is the same as when you arrive - if you're moving at (say) 300,000km/h before, you're travelling at the same speed on the other side.
That would be like jumping off a moving truck onto another truck moving at the same speed.
Sadly, that won't help you because all of the above motions are curved, spirals within spirals.
Rather than a comfortable landing, you'd shoot off at a tangent, ending up - well, good luck with that.
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