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Here's an interesting scientific problem.

Drop a small ice cube into a partially filled glass of water. Next, get a foot-long piece of thread or string. The puzzle is to remove the ice cube from the glass using only the string as a lifting device. You cannot tie a loop in the string, and you cannot touch the ice cube with your fingers.

Hint: You'll really be worth your salt if you can solve this mystery!

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    $\begingroup$ You might wanna take a look on the tags... Logical deduction isn't appropriate here. $\endgroup$
    – Lolgast
    Feb 2, 2018 at 14:17
  • $\begingroup$ I might make someone other answer tick if it's better than the current ticked answer $\endgroup$
    – A Cool Guy
    Feb 2, 2018 at 17:46
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    $\begingroup$ You say "using only the string as a lifting device" but the solution relies on something other than the only thing you said was allowed... $\endgroup$
    – maxathousand
    Feb 2, 2018 at 19:00
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    $\begingroup$ Is it fair on this site to post long-established puzzles? This one was published well over 50 years ago. $\endgroup$
    – Prune
    Feb 2, 2018 at 19:56
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    $\begingroup$ Travel to space. Then move the glass away from the ice. Wala! The ice is out of the glass (no strings required). $\endgroup$
    – n00b
    Feb 2, 2018 at 20:05

9 Answers 9

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I was wondering if this solution would be allowed, but then when I read the hint, it made it obvious that it was intended.

First, lay the string on the top of the ice cub. Next, sprinkle some salt over the string and ice. Wait a little bit. The salt will decrease the melting point of the ice, so some of it will melt. However, as the salt eventually gets dissolved in the rest of the water, it will freeze back up, entrapping the string in a thin layer of ice on the ice cube. Now, you can simply lift up the string and the ice cube will be removed from the glass of water.

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  • $\begingroup$ @dna got this answer first $\endgroup$
    – user
    Feb 2, 2018 at 23:48
  • $\begingroup$ To be honest I'm surprised they didn't get marked as the answer instead. Also, I didn't see their answer before posting mine (I assumed it wasn't posted yet since nothing was marked yet). $\endgroup$
    – Ben Richards
    Feb 3, 2018 at 0:07
  • $\begingroup$ lol good go lucky u @BenRichards $\endgroup$
    – A Cool Guy
    Feb 3, 2018 at 13:54
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Well, I doubt this is the intended answer, but...

Just use the string to tip over the glass. Surely the ice cube will come out then.

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  • $\begingroup$ how can u even tip a glass with a thin string? if u even fold it 100 times u wont be able to tip the full-of-water glass. Yea when u will reach to the 100th fold of the string, you will notice that the ice had already melted! $\endgroup$
    – A Cool Guy
    Feb 2, 2018 at 16:10
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    $\begingroup$ @acoolguy Just loop it around in a U, and pull both ends. $\endgroup$
    – internet_user
    Feb 2, 2018 at 16:12
  • $\begingroup$ lol ur not allowed to do that $\endgroup$
    – A Cool Guy
    Feb 2, 2018 at 17:44
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    $\begingroup$ @ACoolGuy , you have a slight problem with your question/puzzle then since you don't specify that you CANT do that. You are given a starting condition (ice cube floating in a glass of water), a tool (the string), and a goal (get the ice out of the glass), and a limitation (no touching, or loops). You didn't limit the how. In fact, the answer you are going for doesn't use any part listed in the question; so we have to assume you are purposefully allowing "out of the box" thinking. Knocking over the glass totally counts. $\endgroup$
    – Ruscal
    Feb 2, 2018 at 18:38
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    $\begingroup$ You don't even need a loop. One end in each hand and push/pull hard against one side, or wriggle the string under the glass and lift, to tip it over. +1 for not mucking about. $\endgroup$
    – Nij
    Feb 2, 2018 at 23:22
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My solution doesn't fit the hint, but nonetheless,

Wait for the ice to melt - Edit: This step isn't neccessary.

Then

Place one end of the string in the water, and the other end out of the glass

Then

Put the glass in the freezer (or just let it sit outside if it's a cold day)

After that, simply

Pull the ice out using the string

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  • $\begingroup$ u deserve a up vote! $\endgroup$
    – A Cool Guy
    Feb 2, 2018 at 17:56
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    $\begingroup$ This is a better as it only uses the items explicitly allowed. $\endgroup$
    – maxathousand
    Feb 2, 2018 at 19:02
  • $\begingroup$ I was going to say put the string in, then go outside in the freezing cold and wait. I like this solution better :D $\endgroup$
    – n00b
    Feb 2, 2018 at 19:53
  • $\begingroup$ @maxathousand Well, there is the freezer ... or the whole geography of the place for the cold day. :) $\endgroup$
    – Lawrence
    Feb 3, 2018 at 14:41
  • $\begingroup$ @Lawrence true.. I guess you’ve got to draw the line somewhere $\endgroup$
    – maxathousand
    Feb 3, 2018 at 18:33
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Using salt, you change the water/ice melting temperature.
This way you can make it so that the string goes inside (or at least adheres to) the ice cube.

It kinda break the challenge, especially considering the google search I used to get this video (lifting ice cube with string explanation).
I ask you to trust me when I say that I searched the video after answering the puzzle.
https://www.youtube.com/watch?v=m1TlnGhBIs8

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    $\begingroup$ Would you mind explaining exactly how this works? It's not quite clear to me. Also, though this might be more for the OP, but the question mentions "using only the string as a lifting device". I'd understand that as not being allowed to use anything else. (Note: Based on the hint this might be correct... But in that case the question needs work) $\endgroup$
    – Lolgast
    Feb 2, 2018 at 14:20
  • $\begingroup$ Here's an explanation: planet-science.com/categories/experiments/magic-tricks/2011/12/… . But I wonder whether it's valid when the problem as outlined above did not mention we could use other items (salt). $\endgroup$
    – Tom
    Feb 2, 2018 at 14:25
  • $\begingroup$ Ok. but ill give u a up vote good job. Keep answering as only one answer can be marked tick! $\endgroup$
    – A Cool Guy
    Feb 2, 2018 at 15:29
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I would say that there is a way to freeze the thread to the cube since the cube floats and is accessible from the surface. Wet the thread and place it on the ice itself, and within a short time the water on the thread will be frozen and stuck to the cube.

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  • $\begingroup$ good job but did u see the hint? $\endgroup$
    – A Cool Guy
    Feb 2, 2018 at 17:56
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I did it the stupid way. Dangle the string in the water and get it underneath the ice, then yank the string up quickly.

If you lift the string slowly, the ice cube will just slide off the string. But if you pull quickly enough, you can catapult the ice out of the glass. I got it on the fourth attempt, less than a minute's work.

Much quicker than messing about with salt and freezers :-)

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  • $\begingroup$ @not store bought dirt, you're asking me how wide is a piece of string? Thanks, you just made my day! $\endgroup$
    – Alexander Hanysz
    Feb 3, 2018 at 1:24
  • $\begingroup$ er yes, how thick? I tried this with thread and can't repeat it. $\endgroup$
    – user19641
    Feb 3, 2018 at 1:50
  • $\begingroup$ The piece of string was from a fairly ordinary ball of twine, one that looks like the photo at en.wikipedia.org/wiki/Twine , approx 2mm thick. $\endgroup$
    – Alexander Hanysz
    Feb 3, 2018 at 1:58
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Yarn is a type of string so you can;

Soak a peice of yarn in the glass of water. Mold it into the form of a spoon (note this does not require tying). Place it in the freezer, keeping that shape. Wait a few hours, then take it out, and use your frozen "spoon" to remove the ice cube.

Alternatively

Wait for the ice to melt. Then keep dipping the yarn in the water and squeezing it dry outside the glass. Repeat until the glass is empty.

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  • $\begingroup$ it would take hours but up vote! $\endgroup$
    – A Cool Guy
    Feb 3, 2018 at 13:55
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An alternatively is that you could:

Fill a sink with water and submerge the glass

This is valid because:

Taking advantage of buoyancy is not the same as lifting.

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  • $\begingroup$ What ‘‘sink’’ are you talking about? $\endgroup$
    – Peregrine Rook
    Feb 3, 2018 at 2:48
  • $\begingroup$ I'm going to remove the first line, since it isn't part of the answer so that this answer isn't deleted, and put the second line in a spoiler for you. $\endgroup$
    – boboquack
    Feb 3, 2018 at 3:15
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The currently most popular answer is legit, but this one addresses the complaints about the water:

Submerge the string in the water until it's soaked. Pull one end out of the water and dangle it outside the glass. The string will siphon the water out of the glass, leaving only the ice cube. THEN use the string to tip the glass over, away from the water puddle.

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  • $\begingroup$ ooo another intelligent idea over here guys! Up vote! $\endgroup$
    – A Cool Guy
    Feb 3, 2018 at 13:58

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