Is it possible to equal the sand level in both bulbs of an hourglass without looking into it?

For example, if one bulb contains more sand than the other one, and more sand in would mean it flows faster, if the bulb is at top, we may just turn the hourglass over and over quite fast, until the both bulbs are balanced. But I guess that would not work, as some people mentioned the sand would run at quite equal speed independent of the amount of sand above it.

Another idea would be to knot a string to the hourglass center to check the balance and turn it by hand to adjust the sand levels. However, as the sand does not rest in defined position (as water would do), it seems impossible to check for equal sand amount by checking the horuglass balance.

Any further ideas?


1 Answer 1


Assuming a perfectly well made and symmetric hourglass, one could equalize the level of sand in both bulbs by placing it on its side and shaking it gently for a long while.

Alternatively, break the hourglass and dump out all the sand, but I suspect that's not the answer you seek!

  • $\begingroup$ The shaking idea sounds plausible. However, trying it on a real hourglass revealed that the sand is quite stable in a certain position, thus it moves in short intervals and calms down inbetween. Using a strong vibration or constant quite agressive knocking on the glass would give the desired result it seems... but this is not so practical as it takes a long time of aggressive movement. $\endgroup$
    – dronus
    Apr 1, 2014 at 11:25
  • $\begingroup$ Sadly, this even won't work at all. There is less sand as one full bulb in total in the glass, so the level would equalize just until it drops below the passage in both bulbs. $\endgroup$
    – dronus
    Apr 1, 2014 at 11:28

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