Last Word is New Scientist’s long-running series in which readers give scientific answers to each other’s questions, ranging from the minutiae of everyday life to absurd astronomical hypotheticals. To answer a question or ask a new one, email lastword@newscientist.com
If Earth turns at (say) 1000 kilometres per hour at London’s latitude, when wanting to travel, why not just go straight up and wait for your destination to rotate around until it is beneath you? (continued)
Eric Kvaalen
Les Essarts-le-Roi, France
All the answers published previously say this wouldn’t work, although Ron Dippold did say that you could end up 1.3 metres west of where you started. But the idea would work. If you have a rocket and launch yourself straight up with a speed of several kilometres per second, you will go into a highly eccentric, elliptical orbit.
You will go thousands of kilometres away from Earth, and then start coming back down. Though the horizontal component of your velocity starts at 1000 kilometres per hour, it goes down in proportion to how far you are from the centre of the planet. Where you come down, the solar time will be a bit later than it was when and where you blasted off, but Earth will have turned while you were in space, and you will come down at a longitude further to the west. As the eccentricity approaches its maximum value (which means you may go as far away as the moon, or further), the duration of your trip gets longer and longer, so it may be days before you come back down, and you will have effectively gone around the world several times.
This means blasting off with a speed of around 11 kilometres per second and coming back down with the same speed. If you start in the northern hemisphere, you will end up at a latitude a little bit south of where you started.
Of course, it isn’t the most energy efficient way to get to New York. And you wouldn’t survive the vertical re-entry into the atmosphere or the crash landing.
Better to go by blimp.
Martinus Roos
Elgin, Moray, UK
We have been tragically told on these pages that you can’t just hop into the air and expect Earth to spin underneath you to get to your destination – apparently, the atmosphere rudely insists on sticking with the planet. Well, not always.
The Scottish islands of Orkney, the land where the wind never takes a coffee break, offers a slightly breezier alternative: just hop in a balloon and let the wind do the driving. Stay aloft at the right latitude, and you will circumnavigate the globe in a year – no passport required (though maybe pack snacks).
I should know – my anemometer clocked an impressive 19,000 miles of wind over nine months before it was violently retired by one particularly determined gust. Earth’s circumference at that latitude is 20,000 miles.
So don’t delay – come to Orkney, launch a balloon and drift your way into an international adventure. Or at least to Shetland.
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