
As boring as watching...
Paint dry...
grass grow...
Jelly set...
... Have truly nothing on this!
Grab a coffee, fire up the browser, open the webcam, and wait: sometime soon – perhaps within days – a drop of pitch will fall, and for the first time, the event might actually have spectators. One of the world's longest continuous scientific experiments, at the University of Queensland , lives under a bell jar in a university …
Glass is NOT a liquid like pitch is. This has been proven false a number of times.
The old theory was that glass was thicker at the bottom because it was a semi-liquid, and gravity slowly pulled it down.
However: More often than not, the thick part of old glass is not at the bottom. In many cases, it is even at the top. The glass is not thicker in some places due to it flowing, but rather because it was not formed on a perfectly flat table.
Pretty much this. Instances of ancient glass windows having glass panes thicker at the bottom is just because medieval boffins clever enough to build cathedrals in the 11th century were also clever enough to understand that putting heavy end up is just plain silly. No flow of glass has ever been observed.
Simple as that. If the thick edge was consistently placed towards the top, in a leaded pane, mechanical forces would encorage to the pane to peel out of the opening if the fixings were compromised.
Less robust (even if only marginally) restraint is needed if the thick edges rests on thin, than with thin on thick.
A simple observation - if glass behaved as a viscous liquid then lenses that need to be shaped to 1/10th the wavelength of light would not last very long. I have some binoculars that are decades old and still work as well as when they were new so the glass cannot have flowed by any meaningful degree.
@mtp: To add onto this, we can just look at the OP.
In the pitch drop experiment, the pitch sits inside of a glass funnel, surrounded by a glass bell, and drops into a glass beaker. None of the glass has deformed, while the pitch has flowed enough to drop nearly 9 times now.
Next, we can also add egyptian glass beads that have been found. These beads still have the center hole, and maintain their round shape. So, we can now say that even on a scale of over 3,000 years, glass does not appear to move at all.
Decades old is not centuries old.
And you have not had them tested have you, and almost no body, no where, has the testing gear to test them, have they.
If Jesus can blast off into low earth orbit without rockets, then glass can be thicker at the bottom too.
Hope he has more than one camera pointing at it. I can see Murphy's law rubbing his dirty little hands in anticipation of fucking up the camera or connection in some way just before it drops
RTFA !!!
From the El Reg article:
"...professor John Mainstone, set up a Webcam to capture the last drop to fall in 2000, but it broke down....this time, professor Mainstone has more than one camera helping keep watch..."
That glass is a very slowly flowing liquid is a popular misconception, probably fueled by observations of centuries old windows. In those days, glass makers were not good at making panes of glass that were consistently thick. When installing the glass, it made sense to place the thicker part at the bottom - hence the impression that the glass must have flowed towards the bottom of the pane over the space of the centuries.
Many of them were very good at making glass.
It was the time, and the technology, and the methods used.
At the time, people were happy with it too...
But thanks to massive industrialisation, high speed glass plants, and production lines, more or less flawless float glass is coming off the liquid tin filled tanks - which incidentally, "on the float" the liquid glass has the same curvature, as the earth.
But glass does flow under gravity - based upon it's temperature.
In those days, glass makers were not good at making panes of glass that were consistently thick.
The standard way of making sheet glass (prior to the invention of modern float-glass plants) was to melt the stuff and pour it onto a flat surface. This gives a big, flattish puddle that is thicker in the middle. Glass taken from the edge was significantly more expensive that the thicker stuff in the middle, but all of it was tapered to some extent. The bit right in the centre with the "bullseye" in it from the pour was considered scrap and flogged off cheap to those who couldn't afford proper glass for their windows.
All the more amusing that a bullseye pane is now seen as quaint and olde worlde.......and costs more than a flat bit...
'bullseye' glass is actuall produced when glass panes are manufactured in a different manner, through glass blowing. A 'bulb' is blown and enlarged before the end is cut and the bubble spun to form a large disc on the end of a rod. It is the centre of this disc, where the rod is attached that makes the 'bullseye', which generally has the form of a bulge with concentric ripples and a cenral raised 'bullseye' where the glass rod has been snapped off.
Heating the glass enough to reduce the viscosity allow you to pour it onto a surface so that it would flatten before it cools would be prohibitively expensive, whereas spinning the cooler (albeit stil very hot) glass is a lot cheaper and easier.
Thanks for making me feel old, commenters!
The "glass: liquid or solid" brought back memories of my very first witnessed full-bore flame war. On Usenet's sci.physics. Late 80s, IIRC.
That was when even trolls could use multi-syllabic words, with proper sentence structure. Before the Darkness came, before AOL...
I was at UQ back when there was a "drop" in 1988. Unfortunately, this was due to the fact that Brisbane was hosting a World Expo at the time and the Power-That-Be(tm) decided it would be good to move the whole experiment from its resting place to display it at the Expo.
Needless to say, being moved like that cause it to drop "prematurely". And no, no-one was around at the time either.
<sigh>
"Since the funnel was opened in 1930, eight drops have formed and fallen – and in spite of the researchers' best hopes, the event has never happened when anyone was looking. The current custodian of the experiment since the 1960s, honorary professor John Mainstone, set up a Webcam to capture the last drop to fall in 2000, but it broke down."
Honorary professor John Mainstone professes patience most of all!
There are some field experiments at Rothamsted which go back to the 1840s.
And of course Britain's ongoing experiment of the American colonies seems to be going nicely after more than 250 years. There is even some evidence you will soon be able to get a decent cup of tea on the other side of the Atlantic.
OK probably going to get flamed here, but I don't think this is the worlds oldest experiment. I remember watching something on the History channel years ago where a scientist set up two large glass tubes filled with a liquid mixture in a church lobby and left them to see how long it would take for them to separate. I have had a quick google but can't find anything on it. Also the church thing may be a red herring but it was an old building and in the UK.
As far as I can remember it's still going.
Anyone know anything about this?
Let the debunking begin!
Damnit, I know i've seen a programme featuring the experiment you mention, but I *cannot* find a reference for it!
IIRC it's an experiment in the diffusion of liquids using two 10' long (or some such size) vertical tubes, I think the top one had copper sulphate in and the bottom one was water. The experiment is to see how long it will take before both tubes are an identlcal colour and it had been running since the 19th century.
My recollection was that it was in a chemistry lab at Oxford or Cambridge but my google-fu has let me down :-(
Anyone else remember this?
1. There was an experiment set up on the mezzanine floor of Cambridge University Engineering Department which had pitch flowing down an inclined channel (gradient of about 1 in 3?). I saw it in the early eighties, and it had flowed a few inches. Does anyone know when it started?
2. I heard reports that the Metallurgy Department at Cambridge had its entrance foyer redecorated, but the architect specified a lead mural, which began to flow. The dept. was quite annoyed to have this disaster attributed them. Or is this all just a myth?
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