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# Half full or half empty indicator.

 (+13, -1) [vote for, against]

The "glass half full or glass half empty" paradox is one which has beset mankind ever since he invented glasses and started to take his drinking seriously.

Fortunately, those awfully nice chaps at MaxCo. have found a solution.

Let us assume that you encounter a glass of beverage in which the liquid level is at the 50% mark. The unknown factor is whether that level has been reached:

(a) by adding liquid to an initially empty glass (in which case the glass is clearly half full) or

(b) by removing 50% of the contents from an initially full glass (in which case the glass is clearly half empty).

Throughout history, and even before, there has been no reliable way of determining whether a given 50%- full/empty glass has arrived at that state by process (a) or (b).

The MaxCo. Half-Full Or Half-Empty Indicator consists of two parts. One is a pair of beads, joined by a 1" length of string. The other is a single bead.

Of the pair of conjoined beads, one is made of steel and the other is made of wood. The solo bead is simply a small spherical magnet.

The pair of beads is dropped into the glass (regardless of its current state). The magnetic solo bead is then placed on the outside of the glass, such that it holds the steel internal bead through the glass wall of the, ah, glass.

Now, if the glass was initially full, and is drained to the half-way mark, the wooden internal bead will fall (with the level of the liquid, on which it floats). Its weight will drag the steel bead (to which it is tethered) downward. Therefore, a half-empty glass will have the wooden bead at the level of the liquid, and the steel bead (and magnet) 1" above it.

If, on the other brachial extremity, the glass was initially empty and is filled to the half-way mark, the wooden bead will float (with the rising liquid). It's floatation will drag the steel bead upward. Therefore, a half-full glass will have the wooden bead at the level of the liquid, and the steel bead (and magnet) 1" below it.

Thus, at a glance you will know, without doubt or uncertainty, whether the glass is half full, or half empty. Gadulka!

 — MaxwellBuchanan, Oct 06 2015

 It seems you are trying to build a kind of hydraulic schmitt trigger.

If you accepted that to be half full, liquid has only been poured in, and to be half empty, liquid has been poured out, you could have tubes connected at a few points around the halfheight perimeter joining to a second reservoir, perhaps a double-walled vessel. The second reservoir would be filled if the glass has been at a pouring angle.
 — mitxela, Oct 06 2015

Ah, but cleaning such a glass would be a bit of a bugger.
 — MaxwellBuchanan, Oct 06 2015

 This is that level of amazing brilliance/uselessness that I come to the Halfbakery for.

That and the flame wars.
 — doctorremulac3, Oct 06 2015

Yay, now solve chicken vs egg debate.
 — blissmiss, Oct 06 2015

That one is easy. Dinosaurs lay eggs. Fish lay eggs. Dinosaurs and fish predate chickens. Therefore, egg.
 — MechE, Oct 06 2015

 //fish predate chickens//

 Now that's just plain silly. Although many fish are predatory, they hardly ever encounter chickens, unless there happens to be a flood near a chicken farm.

You may be thinking of ducks. (In any case, you are now.)
 — MaxwellBuchanan, Oct 06 2015

 When you drop the conjoined bead pair into the glass the flotation bead (let's call it so since not all woods float) marks the level of the liquid while the sink bead rests 1" beneath the surface, and this is where you place the magnet. You still have no idea whether liquid is being added or removed until the level has changed, by which time you know by simple observation, so the beads have not helped.

BTW - any glass containing 50% of its capacity is neither half full nor half empty, it's just the wrong size.
 — Tulaine, Oct 06 2015

 //You still have no idea whether liquid is being added or removed until the level has changed, by which time you know by simple observation, so the beads have not helped.//

Ah, but no. The beads are intended to address the situation where you happen upon a 50% full/empty glass without having been aware of its prior state.
 — MaxwellBuchanan, Oct 06 2015

Clearly the glass simply has a factor of safety of two.
 — RayfordSteele, Oct 06 2015

 What if the contents of the glass were always there, and had neither decreased or increased since the beginning of time?

 Alternatively, due to evaporation, it can never be accurate to say that it is half full or empty, because while you were saying it some evaporated and consequently it is below 50% and on the way down.

Alternatively, due to the phenomena whereby the earth is picking up particles from space all the time, the quantity in the glass has risen from 50% to a smidgen higher, while you were in the speech act of saying it was half full or half empty.
 — Ian Tindale, Oct 07 2015

Also this device wouldn't work for half full/empty glasses of liquid in zero gravity.
 — hippo, Oct 07 2015

 //Yay, now solve chicken vs egg debate.//

 Egg. The first chicken came from an egg that was laid by the last predecessor to the chicken. Although the differences between the two may have been incremental over time and very subtle, at some point the line has to be drawn between primitive cave chicken and modern chicken. That line would have mother on one side and chick on the other, the modern chicken coming from a modern chicken egg laid by a non-chicken, so: egg first, then chicken.

 And really? Only 4 buns for this? And a bone to boot?

 Thought this one would be big. Shows what I know.

 I thought of another way to do this. You have one of those heat sensitive glasses where the art on the outside changes color. So if the top of a glass with half its contents in it is the same color as the bottom, it's half empty. If it's not, it's half full owing to the fact that no liquid has touched the top of the glass.

Might work as a bar bet. Tell somebody you can tell if a glass is half empty or half full just by looking at it from across the room. Then whip out your heat sensitive glass.
 — doctorremulac3, Oct 07 2015

//Only 4 buns for this?// I think that's about right, myself...
 — MaxwellBuchanan, Oct 07 2015

Oh good lord - people are overdoing it now.
 — MaxwellBuchanan, Oct 07 2015

I would have thought the implied titular question could be answered by close inspection of the miniscus.
 — csea, Oct 08 2015

Because this idea is so long-winded and I didn't read it thoroughly, I shouldn't be making any comments on it. But as I have dyed my hair blonde, being an automatic free-pass to act stupid and say stupid things, I will say that "What if someone laid a straw down the side / inside of the glass and poured liquid through said straw, so as not to disturb the beads, and then it was filled again?"
 — xandram, Oct 08 2015

//What if someone...// Is that likely to happen?
 — MaxwellBuchanan, Oct 08 2015

Well, yes...I would do it!
 — xandram, Oct 08 2015

Well then, clearly we would not sell you one of our indicators.
 — MaxwellBuchanan, Oct 08 2015

Brief ones, in my experience.
 — MaxwellBuchanan, Oct 08 2015

You mean to try to fecking SELL these things? I think they don't work and can be sabotaged by any blonde female.
 — xandram, Oct 08 2015

Sales are doing very nicely, thankyouverymuch.
 — MaxwellBuchanan, Oct 08 2015

Anything that attacks out of fear can be classed as a 'chicken' which, back in the day, was a fair few organisms. This may indicate that chickens are first.
 — wjt, Oct 09 2015

Fiddly beads on a vessel meant to be used in a sozzled state, hmm... I recommend that a sippy cup lid be amended to the invention to prevent accidental ingestion of measurement devices.
 — Sgt Teacup, Oct 13 2015

 Au contraire, [Sgt]. Accidental bead ingestion is perfectly safe. Continued use of the device can be insured in either of two ways:

 (a) By purchasing a new one or

(b) By other means.
 — MaxwellBuchanan, Oct 13 2015

Can the magnetic bead come as a ring , to be worn on your drinking hand? Every time I pick up the glass with string attached, I'll be able check my changing fluid state.
 — wjt, Oct 14 2015

 //(b) By other means.//

 Well now [MB], that gives me an ancillary idea for materials reclamation, perhaps involving a sieve-like structure of environmentally-friendly coprophagic organisms living in a commode.

Unless you meant 'theft', as the second choice.
 — Sgt Teacup, Oct 14 2015

Just tip the glass diagonally. If the answer to the "glass half empty or half full question" (which is a yes-or-no question) is yes, then there's an angle at which the top surface of the liquid touches both the rim of the glass and the edge of the bottom of the glass.
 — LoriZ, Oct 19 2015

...assuming a rotationally symmetrical glass, and a non-pedantic interlocutor, yes.
 — pocmloc, Oct 20 2015

 Well, this idea seemed much more exciting when the dyslexic part of my brain held strongly to the idea of a floating pair of beards plus solo magnetic beard being used in all beverages across the world!

The sudden swap from beards to beads has emptied 50% of the joy.
 — strayllama, Oct 29 2016

This is a high-tech answer to the question. My wife would tell you. She knows everything. She will explain to you that 'There is hardly any wine in the f***ing glass'.
 — bhumphrys, Oct 29 2016

Philosophical point notwithstanding, I object to the glass's current half-status being dependent on its prior status. It ought not matter the previous state, or the intentions of the actor who/what caused the current state. Consider the glass's role, perhaps it is too big, else the glass would be full given the same amount of liquid, it might be necessary to remove some in order to fill the glass under abstract circumstances such as a glass 150% full. I consider that half-full and half-empty are functionally identical terms and equal values, and that the distinction is unnecessary, and seeks to divert attention from the fact that the glass contains urine.
 — tatterdemalion, Oct 29 2016

 I have to disagree, [tatter]. The terms "empty" and "full" are used as nöeözegeumas (or, if you prefer, nöeözegeumatically). Thusfore, "half full" implies (ad ipso per ipsos) that the process of filling has been interrupted, and left half complete. Conversely, "half empty" implies (again, ad ipso per ipsos) that the process of emptying has been interrupted, and left half complete.

Consider the analogous situation. You are in a train that runs between Bastardo, in Umbria, and Gubbio, also in Umbria. If you find yourself half way from Bastardo to Gubbio, this implies that in due course you will find yourself in Gubbio. If, conversely, you find yourself at the exact same spot, but half way from Gubbio to Bastardo, then it is likely that you will ultimately arrive in Bastardo. Same instantaneous situation, but different outcome.
 — MaxwellBuchanan, Oct 29 2016

 The photograph taken midway between the two locations needs no further description. It exists at midpoint without qualification, the direction of travel is an entirely other question. Observing the glass of liquid does not presuppose the outcome. It is not a rate of change indication, indeed the glass may contain precisely the correct amount.

I should disclose there is less whisky in the glass to my left than there was earlier, so my judgment may have been influenced.
 — tatterdemalion, Oct 29 2016

At the midpoint of the journey you are "halfway" regardless of direction. I think there is no English language equivalent for glass liquid level, and assume this is something to do with the the intoxication of the drinkers.
 — Ling, Oct 29 2016