h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

Under certain conditions a person can perform a feat that is only usually achievable by supersonic planes.

What is the feat and what are the conditions?

Couple of s and plenty of scope for QIs and DGIs.

Supersonic planes are inanimate and thus can't achieve anything.

So, a corpse?

I had an explanation for this one half-worked-out in my head, and only then did I realise you said "supersonic planes", not "tectonic plates".

micro gravity / whieghtlessness


in side a lift in freefall the occupants are effectively whieghtless and can float around....untill the sudden stop at the bottom

from the title

is it the sun rising again

when a plane takes off after sundow and travells west it can catch up with and pass the terminator, line of shadow between day and night, effectively travelling back in time, as you reset your watch to the time zones you pass throught

how can people do it????

a tall building and a fast lift???? crossing from one time zone to another westward......

It is the sun rising in the west, for exactly the reason you've described Taff - crossing the terminator. +3 points

Now how can a person do it?

By climbing down a mountain - see it at the top - go down into the valley and watch it rise again.

<>

jet pack and a blatant disregard for personal safety

parachuting (freefall) ?

McKay, that'd cause the sun to rise again, but not in the west.

I'm specifically after how someone could make it appear the sun was rising in the west.

Looking in a mirror at sunrise

Supersonic planes can break the sound barrier (hence the name) - I know how using a household object a person can do the same.

If you have one - use a whip - alternatively you can use a tie, if it has begun to fray down to small strands.

Take the tie flick it forward with your wrist (if t helps pretend you are Indiana Jones)

Get it right and you'll here a 'CRACK' sound, just like a real whip.

It used to be thought that sound was the leather looping back and hitting the leather, turns out it's the tip of the frayed end (or the whip tip - hee hee whip tip! ) being accelerated to over the speed of sound - and the 'CRACK' is a miniature sonic boom.

And this is how you can break the sound barrier in your living room or the office or on the bus...

>>It is the sun rising in the west, for exactly the reason you've described Taff - crossing the terminator. +3 points<<


So presumably having crossed it once you've got to catch it up and cross it again?

Possibly an effect in the poles, the curvature making it easier to catch up with it travelling a relatively short distance.

OH!

Is it a sunrise during a solar eclipse?

The sun appears to rise, is obscured, and then appears from out behind the moon is a 2nd 'dawn'

Sorry Clive, a whip is a as anyone can do it at any time, no special circumstances needed.

However the poles is the right answer. The terminator circles the poles at less than 3mph - less than a brisk walking pace. +3

Last bit of the question - when can this happen?

Aww damnit. I was hoping that'd be a QI.

Cheers for the +3. Softens the agony.

Anything to do with something like the vernal equinox - I'm just thinking aloud - that during the winter the sun is perpetually below the horizon so no walking, no matter how brisk will catch the terminator, similarly, when in the summer the sun net sets no can it rise (it sot of wobbles) so it'd presumably have to be somewhere in the middle - perhaps the transition from summer to winter?

Equinox? I'm afraid...





Just kidding

At the poles it would be just before the equinoxes, just as the sun set for the last time in six months. Exact date varies because of the Earth's wobbles. At lower latitudes the date can be up to a fortnight before the equinoxes but you'd have to run to outpace the terminator.

+3 for Clive

If some at the pole allowed the terminator to pass over them, watched the sun set in the west and then started walking westwards around the pole, first they'd see sun rise again from the western horizon. If they carried on walking the sun would rise higher in the western sky before doing a sort of loop, setting again as you caught up with the back end of the terminator.

If you were sufficiently bored, you could do the whole thing a few times before the sun was too far below the horizon to come back.

Points when I get back from a wedding...

Is there an actual wedding planned somewhere, or do we have to wait for someone to propose before you'll do points?