Is the glass always half full?

Time and again on blip I've heard this well-worn optimist's battle-cry. So I thought I'd do a little experiment:

Take one pint glass, and half-fill it with water. Place a cork-bottomed coaster over the top of it, and invert the glass into a goldfish bowl, also half-filled with water.* Remove the coaster and weight the bottom (now top) of the glass with something heavy. Retire to an appropriate distance, and blip. Invert and reverse resultant image.

Now, the water that was at the "bottom" of the glass is at the "top" (now bottom) of the glass, and the air that half-filled the glass only appears to occupy a much smaller proportion of its volume.

So, when immersed in water in this way - is the glass still half full or half empty, and if so, half full of water or half full of air?

Perception and relativity are strange things. To me, when the glass is in the water, the confined element is the air. If we were stuck underwater, the thing we'd be quite pleased to get some of is a gas we could breathe - the absence of water in the glass could help us ("Hooray, I've found an airlock", we would cry - "it's only half full of water" [Edit: you have to say this in an Alan Partridge voice]). When it's the right way up and in the air, the thing it's 'half-full' of is water - the air can come and go as it pleases. So the water is confined, trapped, by the glass.

So really the question is about whether what you are facing is what you desire, whether you perceive it as a scarce commodity or a boundless surfeit of something. Optimist or pessimist, life is not a still glass with 50% of its volume occupied by water - it's a volatile situation unfolding through time.

Assuming that the water represents a 'good thing' for a moment (being alive for example, could be seen as a good thing), what do you do? Down it in one? Sip carefully, savouring every mouthful? Try to make it last as long as possible? Tip it over your head?

To me, the bigger question is - why are we measuring water in a glass and calling it "half" of anything?

I sometimes think that if we were all issued with certificates when we were born that also told us the exact day we were going to die, how differently we might all behave. Our physical existence would be palpably, finitely bounded, book-ended by two moments in time.

I have no idea where any of that gets any of us, so that's enough metaphysical mumbo-jumbo for one blip. Here are some comments I found online:


The philosopher would say that, if the glass was in the forest and no one was there to see it, would it be half anything?

The psychiatrist would ask, "What did your mother say about the glass?"

The physicist would say that the volume of this cylinder is divided into two equal parts; one a colorless, odorless liquid, the other a colorless, odorless gas. Thus the cylinder is neither full nor empty. Rather, each half of the cylinder is full, one with a gas, one with a liquid.

The seasoned drinker would say that the glass doesn't have enough ice in it.

[Editor's note: [b]freshphoto[/b]'s father was for many years a physics teacher whose hobbies are photography and saving money. His mother was a librarian who played the piano and loves to read historical romance novels. As our American brethren like to say: "Go figure"]

What I loved about the effect the above playing-about had, was that the plain old water ended up looking like mercury. Water and air rawk!

*I should point out that to me, the idea of incarcerating a goldfish in a clear glass bubble surrounded on all sides by an alien gas and forcing it to endure plastic knick-knacks all day sounds like a major infringement of basic goldfish rights, so it's not something I would ever do. I just happen to have a large goldfish bowl for... photographic purposes.