An infantry platoon marches across the barren landscape. Says the captain, "We will march 25 miles today, soldiers!" And indeed, by nightfall, they have marched 25 miles. But when they prepare to set up their sleeping quarters, they find that they are in exactly the same place they started! They marched in an exactly straight line, and no other transportation was used.


It is necessary for the soldiers to wear special clothing to survive here, and there is a specific place I am talking about

Another hint: (Don't read unless necessary)

The distance of 25mi matters

  • 1
    $\begingroup$ You're maybe giving hints a little too fast. Don't hesitate to wait a few hours (some will say a day) before giving an hint. $\endgroup$
    – Saeïdryl
    Apr 27, 2018 at 13:40
  • $\begingroup$ Maybe the soldiers should be following a tank whose treads both moved at exactly the same speed (and thus traveled the same distance) without slippage. If the tank were going around the pole of a planet that was much more than 25 miles in circumference, the distance traveled by the treads would differ by almost as much as if the tank made a much smaller circle. $\endgroup$
    – supercat
    Apr 27, 2018 at 20:17

5 Answers 5


We are in the future : the soldiers are marching on a 8 miles diameter asteroid and they need special clothing to be able to breathe

(EDIT) and to be more precise

we're on Ijiraq one of Saturn's moons (approx 8 miles diameter)


Deimos one of Mars' moon works too

  • $\begingroup$ Close, but I'm thinking of a specific place $\endgroup$ Apr 27, 2018 at 13:36
  • $\begingroup$ Please hide your answers with a spoiler tag (">!") $\endgroup$
    – Saeïdryl
    Apr 27, 2018 at 13:39
  • $\begingroup$ sry i forgot the spoiler $\endgroup$
    – Kant1
    Apr 27, 2018 at 13:40
  • $\begingroup$ Third idea is correct! $\endgroup$ Apr 27, 2018 at 13:59
  • 4
    $\begingroup$ I'm not sure such a place would have sufficient gravity to be able to "march". $\endgroup$ Apr 27, 2018 at 22:03

I think they are

Either in the North or the South pole, and they made a big circle. They need special clothing because it's quite cold

  • $\begingroup$ What about the straight line part? $\endgroup$ Apr 27, 2018 at 13:35
  • $\begingroup$ in a straight line $\endgroup$
    – TinyTRex72
    Apr 27, 2018 at 13:35
  • 5
    $\begingroup$ @Saeïdryl I think the point is that there is a point, somewhere just south of the North Pole (probably only a few miles), where walking due east (c.f. west) for 25 miles will return you to your starting point. The same will be true of the south pole. $\endgroup$
    – MD-Tech
    Apr 27, 2018 at 14:14
  • 1
    $\begingroup$ @user2357112 True, so the accepted answer is just as "curved" as this solution—it's just that the soldiers' bodies are oriented differently with respect to the curve in each scenario (walking around a sphere curves down, while this solution curves the same amount but just left or right) $\endgroup$ Apr 27, 2018 at 18:00
  • 3
    $\begingroup$ @maxathousand: Both answers are curved from the perspective of the ambient space, but the accepted answer is straight in the (generalized) sense of being a geodesic of the space formed by the surface of the celestial body the soldiers are marching on, which this answer isn't. $\endgroup$ Apr 27, 2018 at 18:11

Are they

walking/marching on a treadmill maybe?

  • 2
    $\begingroup$ You should spoiler your answer by starting the line with >! $\endgroup$
    – Laurel
    Apr 27, 2018 at 19:04
  • $\begingroup$ ohhh okay ... will do $\endgroup$
    – MrClan
    May 1, 2018 at 4:03
  • $\begingroup$ That's one big piece of exercise equipment $\endgroup$ May 9, 2018 at 12:17

My first thought was

they are future soldiers marching along the inside of a ringworld (or halo, or dyson sphere)


May be this:

They walked 25 miles from their camp A in a straight line and arrived in a camp B. The camp B is built exactly the same as camp A. The landscape is barren and so as a result, it is very difficult to tell that the location is different; only the camp can provide clues but here they are exactly the same.

  • 1
    $\begingroup$ Welcome to Puzzling! Unfortunately, since the question states that they ended "exactly where they started" (and not that it only looked like the place they started in), this does not seem like a valid answer to me. $\endgroup$
    – ffao
    Apr 27, 2018 at 20:06

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