How are they different? Both the article and the wikipedia link you gave mention they are similar experiments. It seems they are the same experiment to me.
The Queensland experiment was mentioned in the article. The GP is confusing because it insinuates that something wasn't mentioned which should have been.
Same experiment, but I for one was interested to know it was not the Queensland one, because that one has a great Radiolab episode about all the times they missed the drop (webcams failing, etc.). Their pitch is due to drop soon too, so it's sort of sad someone else beat them to finally filming it.
Sounds like the pitch may actually contain the Higgs Boson, and it is going back in time and creating events designed to make the monitoring fail. The failing webcam was the proverbial bird that dropped bread into the coolant pipe.
Dude, I'm finding this hilarious. 69 years to prove that something is a fluid? I picture two really old scientists watching the tape, only to have one of the old geezers turning to the other to spill the sacred words: "Told you so".
Science isn't about "told you so". It's about rigor, about completion. It may seem hilarious because of the length of time involved for the experiment to complete, but what if the results hadn't been what we assumed? Science is the only enlightenment we have, and to dismiss the outcome as obvious is to climb back into the dark ages.
Really? Scientists are people. Proving each other wrong is one of the biggest motivators to do years of painstaking, labour-intensive research. Of course, you can't prove someone wrong without being rigorous.
How long are you willing to run a scientific experiment? People dream of projects that run decades or centuries or even millennia (see the Clock Of The Long Now); few manage to.
Well really they could have figured it out as soon as it started moving, which would have been a few months. The first drop fell after a few years and they could have called it quits then, but they wanted a human to observe the pitch drop. That's the only reason it took so long.
Woah woah woah, not so fast, Doctorate McPhdsosoon. Science is repeatable. See you at lab meeting next Monday morning. Please come prepared with a roadmap for phase 2 trials. These grants don't write themselves, you know.
Really, it seems like a dream gig. Just being a student for years and years and continuing to get financial aid to continue your thesis work. I've often said if I could be a student for life I'd be happy. I was just picking the wrong field of study. Viscous fluids, here I come.
In Australia, they give you 3 years (plus an additional 1/2 year extension, which isn't always granted). After that, you're on your own, and many people get a full time job to support themselves.
I've seen quite a few people abandon their PhD because of the need to pay the bills once their funding runs out. It's quite sad.
'liberal arts' doesn't have a meaning in Australia, but I'm not aware of PhD applications being treated differently in different fields (or rather, the rules differing)
Of course, I understand that. But it lasted so long, through tenured generation after generation. Even though I'm aware it wasn't anyone's master work, it had to be quite frustrating to miss it decade after decade.
While I'm fond of this type of down-to-earth experiments, I'm curious about the scientific value of waiting for decades to observe the drop falling due to Earth's gravity, versus placing the apparatus in a centrifuge, which I imagine would dramatically accelerate the process. Maybe the higher forces would affect the way the drop is formed, in a way that was deemed undesirable?
Don't be so sanctimonious. Calling an experiment involving gravity "down to earth" is mildly amusing and is kind of a pun, albeit a feeble one. Much like your sense of humour it would appear.
I would argue that confirmation of the shape in 1G has some actual value.
Sometimes "silly" experiments can have value. I chatted with a physic prof once who said the very first experiment he did after gaining tenure was to investigate the isotropy of the universe in particle accelerator experiments -- in other words, do the laws of physic work the same way when the accelerator is pointed one direction, relative to distant stars, as any other.
Obviously, the likely result would be nada.
However, if he found something, it would be two possible things:
(1) He was going to earn an instant Noble prize, or
(2) There was a potential subtle systematic design error particle physicists had overlooked -- knowing how to look for this error and/or correct for it could have value.
Um, not to take away from the achievement of the result, but couldn't this result have been obtained in much less time with higher force than 1G in, say, a centrifuge?
That would be another variable to account for and isn't the a standard test for viscosity. Also with pitch being this viscous having a centrifuge capable of spinning fast enough and long enough would be troublesome.
I think (hope) it's worth noting the location of this experiment. Trinity College, and the Irish in general, tend to gravitate towards romanticised notions. Even our scientists.
It honestly wouldn't surprise me in the least if the experiment was initiated knowing full well it would take decades to complete but they went ahead anyway 'for the craic'.
I call shenanigans. In the time-lapse, the funnel "jumps" upward right when the drop falls (0:56). Unless the funnel's mounted on a spring (?), this is a clear indication that somebody interfered with the drip. I declare this video null and void!
...or maybe the video camera just got jostled when all scientists started dancing around in their glee =)
The first thought that popped into my punny little brain was: Why didn't they use a centrifuge to accelerate results?
The one variable that could be controlled is the gravitational force on the substance. If we were on the moon the experiment, as designed, would take far longer to produce a drop. By using a centrifuge they could have easily simulated significantly greater gravitational forces and arrived at a result much sooner.
EDIT:
The Queensland experiment data says that it takes about 13 years for a drop to form and fall [1]. You'd need less than 5,000 g's to make it happen within a day or about 160 g's to get results in 30 days.
How long would you have to run the centrifuge for? If it were 6-7 times faster, you would have to run a machine nonstop for 10 years. Seems like a tremendous waste of energy, heat from a motor which could affect the results, and a great likelihood of experimental equipment failure.
Now, there might be reasons why a million g's might be a bad idea. Maybe 100K g's is a better choice. Someone with more expertise in centrifuge application could chip in and clarify this.
I'm not sure it would be valid. At a million g's, I'm a liquid. But most people would broadly speaking classify me as a solid (albeit one containing a lot of liquid).
Not really. You'll disintegrate in strange ways based on the relative density of your constituent parts.
<edit>: Another thought is that if you laid on a bed for 13 years (the time it took for a drop of pitch to form) without moving --ignoring tissue decay and other factors-- you'd probably "flow" just as you might in a high gravity environment. Gravity, like rust, never sleeps. </edit>
Yet, unless a domain expert says otherwise, I think your point is absolutely valid. However, pitch might just be the kind of substance that would be fine at a million g's. I don't know.
That's the reason for my request for comment from someone with centrifuge experience. At a million g's a lot of seemingly strange things can happen. However, perhaps 100, 1000 or 10,000 g's is reasonable. I used the million g example as an illustration of the attainable extreme in response to a comment that spoke about 6 or 7 g's. Clearly we can do better, far better.
In consultation with a domain expert (Chemist?) I would design the experiment to give results in somewhere between a day and a month. Faster if possible. The criteria would be to choose an acceleration that does not fundamentally change the nature of the substance under test. All we want to do is promote faster flow.
I was admittedly being glib; obviously bone has different characteristics than fat. But characteristics can definitely unhappily change and I'd want an expert involved too.
Well, it looks like we have at least one Chemist pitching in (no pun intended). Time to learn a thing or two. Chemistry is one of those things I wish I had devote more time to in school. Lot's of physics and math but never dove deep into chemistry beyond what was absolutely required.
Indeed, it occurs to me that one reason to keep watching the experiment is to see whether heavy pitch migrated to the bottom. If so, the rate should speed up in a few hundred years, assuming the hermetic seal is good and nothing is volatilizing off the top.
This is unlikely, however. Many suspensions have a critical pressure below which they simply will not settle. Homogenized milk, for a familiar example.
> Chemist here. We use centrifuging to separate components of a suspension by weight. Pitch is a suspension.
The last bit is puzzling: Are all suspensions fluids? And all fluids are viscous (even non-newtonian)?
If so, why do we need an experiment to prove that pitch --a suspension-- is a fluid and is viscous?
On the point of using a centrifuge. Is there something particularly special about gravity on earth that does not affect pitch? In other words, if we exposed pitch to 0.1x, 1x, 10x, 100x and 1000x g, at what point would the fundamental characteristics of the material invalidate the experiment. Are fluids and their viscosity only defined on earth (ignoring thermal and other non-gravitational effects)? Perhaps pitch is a viscous fluid on earth but a solid on the moon, where gravity is 1/6 of ours?
Is this experiment only valid at 9.8 m/s^2 then? What's the tolerance based on the substance under test?
No, all suspensions are not fluids. Amorphous rocks, for an example, often contain microcrystals in suspension. They will not flow under any circumstances. Glass can have all sorts of powders suspended in it, and is not a fluid.
Pitch can be proven to be a suspension via distillation. To prove it's a fluid, it must be observed to flow, to form a droplet, and to detach that droplet in the manner of a fluid.
Mathematician here. Yes, this is about to be a nitpick, and I apologize in advance.
However:
> No, all suspensions are not fluids.
I think what you mean is "No, not all suspensions are fluids."
Interpreting what you said literally would imply that anything that is a suspension is definitely not a fluid. And I know one can interpret what you said according to common sense to deduce that you didn't mean that, and that since some suspensions definitely are fluids, then you must have meant that there are suspensions that are not fluids.
But this is about science, and where possible, I believe we should be precise.
Linguist here.[0] Yes, this is a nitpick, but no apologies, because this is Hacker News. :)
Unfortunately, languages don't always work the way that logicians would like them to do. Yes, we can read that sentence as the English-language summary of a logical formula (something like ∀x [Sx -> ¬Fx]), but English (and many other languages) treat the scope of the "not" as ambiguous. It's not a matter of "interpreting what you said literally", because there are multiple correct literal interpretations of what he said---he is not using a metaphor or anything. There are many cases where "not" can scope out to an enclosing quantifier (one of the better-known is "All that glitters is not gold", famously by Tolkien), and this is not just because all these speakers are in error.
[0] Also computer scientist, but I'll wear my linguist hat for now.
For me, It violates the principle of least surprise to encounter a sentence like "all birds do not fly". I have to do a double take and reinterpret the sentence to realise its intended meaning.
IMO, if "all these speakers" collectively make the language ambiguous, then clearly someone is in error, because unambiguity[0] is essential to the primary purpose of language: communication. This has nothing to do with whether one is a logician or mathematician.
A sentence like "all X are not Y" naturally associates like "all X are (not Y)". Usually modifiers attach to the closest thing they can, as a matter of well-established convention. So if someone decides they want that to mean "not (all X are Y)" and expects me to understand it, I'm going to go ahead and say they're the one in error. Sorry, Tolkien.
[0] Is that a word? Chromium spell-check doesn't like it. I have lightened up on neologisms, as long as it's clear what they mean.
Despite the primary purpose of languages being communication, they occasionally fail at it. Does this surprise you? Have you never heard someone say something and completely misinterpreted them?
Ambiguity does exist in natural languages, and it is obviously no big problem.[1]
Unfortunately, technically inclined people like to apply their domain specific "knowledge" (compiler cosntruction?) to everything and come to incredibly bad conclusions. Ex falso quodlibet.
It gets especially bad when technical guys talk about law and juristic methodology. Demonstrated daily here on HN.
[1] BTW, linguistics is descriptive, not prescriptive. You immediately disqualify yourself from any linguistic discussion when you claim that native speakers are in error.
Is it? We function in the presence of ambiguity all the time. Sometimes, we let the ambiguity ride. Sometimes, we take a sentence that is (by itself) ambiguous and let the context disambiguate it. Sometimes, we use the ambiguity for some rhetorical purpose and then resolve it later. There are many sources of ambiguity in natural language---it's one of the things that makes NLP so damn hard---and you can't wave that away by saying that everybody is doing it wrong. (Not that generations of prescriptivist grammarians haven't tried.)
> Usually modifiers attach to the closest thing they can, as a matter of well-established convention.
First of all, attachment ambiguity is a difficult NLP problem specifically because modifiers don't always attach to "the closest thing they can". Second, to the extent that the statement is true (that low, i.e. "closer", attachment has a higher prior probability than high attachment), it is not a matter of "convention" but a fact about the grammar of a language. Third, "not" is special in all sorts of ways (as is negation in general, in many languages, not just English), and as I mentioned before, this specific kind of ambiguity is well-known, and interesting because it seems so strange, and once again you can't just wave the logic stick and declare that it ought not to be so.
The question asked if all X are Y. You want to assert that there are some X that are not Y. You can retain the original structure, and be correct according to the strict logic, by saying:
Not all X are Y.
or
Some X are not Y.
If someone came along with no knowledge of the field and read your statement: "all suspensions are not fluids." then it would be reasonable for them to deduce that for every suspension they looked at, it would not be a fluid. This is false.
To answer your second question, there is some critical number, which we do not know empirically, after which pressure will separate pitch.
We could apply some higher acceleration for a shorter time, but that acceleration would have to be highly consistent, and there is no way to shorten the experiment enough to keep that equipment from being unproductive to even contemplate.
OK, had a break so I looked around a little to see what I could learn [1], [2], [3] and [4] are my launching points.
So I read that asphalt is actually a colloid and that pitch is not the same as asphalt. The Wikipedia page on pitch [3] says it is a "viscoelastic polymer".
So I have to ask. Can a polymer be a suspension or a colloid on its own or is pitch a polymer colloid in another "host" substance?
Pitch is also a colloidal suspension, or colloid. The various polymers that make it up are not of equal weight, and there are little bits of graphite in there too. The chemistry of pitch is by no means simple, destructive distillation can go in many directions.
Just letting a suspension sit on the laboratory bench does the same thing: gravity separates the components by density (not weight). That's why you stir paint before you use it: it has partially separated, and has done so without the without the use of a centrifuge.
It is in fact density, although in my defense I meant molecular weight. But was still wrong ;-)
However, there are many suspensions which will never settle under standard gravity, but which will rapidly settle in a centrifuge. We call these colloids.
Centrifuges don't provide a uniform field. The centrifugal pseudopotential is V(r) ~ Ω^2 / r^2; in effect this means that the pitch near the outside of the centrifuge experiences more "gravity". If you want to study pitch in a uniform gravitational field, you'd either need an absurdly large centrifuge -- the size of the Pentagon -- or a solar sail to Jupiter.
edit: also, the Earth's gravity might become a problem.
"Over the years, the identity of the scientist who began the experiment was forgotten, and the experiment lay unattended on a shelf where it continued to shed drops uninterrupted while gathering layers of dust. Physicists at Trinity College recently began to monitor the experiment again. Last April they set up a webcam so that anyone could watch and try to be the first person ever to witness the drop fall live." - http://www.nature.com/news/world-s-slowest-moving-drop-caugh...
"Over several decades a number of drips did form in the funnel and fall into the jar, giving credence to the hypothesis that pitch is indeed viscous."
It sounds like the experiment, as designed, reached a conclusion in far less time than 69 years. It just took 69 years for someone to think about video taping it.
Nope, assuming they designed it for scientific rigour. Without observation, it would be impossible to say, for instance, that some external force (vibration, wind, mischievous students) hadn't caused the drip to form or fall/break off. The experiment didn't reach a firm conclusion (to some level of certainty) without observation.
That's what the parent said: there were previous chances to definitively end the experiment by observing drips, but no-one thought to monitor it with a video camera until recently. There was no need to wait 69 years.
No, they said "It sounds like the experiment, as designed, reached a conclusion". As designed it didn't, as they didn't include camera-based observation in the design, the design called for someone to notice the drip to prove the viscosity of the substance, and that didn't happen until now.
Maybe it was a badly planned experiment (or more likely, the cost/availability of cameras in those days prohibited their inclusion in the plans). Nevertheless, no firm conclusion can be drawn that the experiment could have been ended early, those previous "drips" may not have happened without external forces applied and so even if cameras had been used it may not have ended until now. Its probably likely that it would have ended had cameras been available, but the scientific method generally calls for a greater degree of certainty than "probably likely" before calling an experiment a success.
And of course, it is called an "experiment", not a "certainty". Mistakes happen and they're not always optimal, that’s all part of the fun of science!
My favourite thing about this story is the various times that this and similar experiments around the world missed capturing the actual drip due to various glitches and snafus; imagine the howl of anguish of the researcher coming in one morning to find that yes something has finally happened after all these years, only to discover that some doofus had left the lens cap on ....
Have they analyzed the dripped substance? My first thought is that it could be from condensation formed on the pitch over a large amount of time due to temperature gradients.
118 comments
[ 2.8 ms ] story [ 189 ms ] threadThat was the most interesting thing I found in this experiment.
http://en.wikipedia.org/wiki/Pitch_drop_experiment
GP is pointing out that there are two experiments underway.
In Australia, they give you 3 years (plus an additional 1/2 year extension, which isn't always granted). After that, you're on your own, and many people get a full time job to support themselves.
I've seen quite a few people abandon their PhD because of the need to pay the bills once their funding runs out. It's quite sad.
'liberal arts' doesn't have a meaning in Australia, but I'm not aware of PhD applications being treated differently in different fields (or rather, the rules differing)
Bwahahahah!
Sometimes "silly" experiments can have value. I chatted with a physic prof once who said the very first experiment he did after gaining tenure was to investigate the isotropy of the universe in particle accelerator experiments -- in other words, do the laws of physic work the same way when the accelerator is pointed one direction, relative to distant stars, as any other.
Obviously, the likely result would be nada.
However, if he found something, it would be two possible things: (1) He was going to earn an instant Noble prize, or (2) There was a potential subtle systematic design error particle physicists had overlooked -- knowing how to look for this error and/or correct for it could have value.
#2 was more likely. But why not?
It honestly wouldn't surprise me in the least if the experiment was initiated knowing full well it would take decades to complete but they went ahead anyway 'for the craic'.
...or maybe the video camera just got jostled when all scientists started dancing around in their glee =)
Or they got bored and cheated. 50/50 really.
The one variable that could be controlled is the gravitational force on the substance. If we were on the moon the experiment, as designed, would take far longer to produce a drop. By using a centrifuge they could have easily simulated significantly greater gravitational forces and arrived at a result much sooner.
EDIT:
The Queensland experiment data says that it takes about 13 years for a drop to form and fall [1]. You'd need less than 5,000 g's to make it happen within a day or about 160 g's to get results in 30 days.
[1] http://www.nature.com/news/world-s-slowest-moving-drop-caugh...
Here's an interesting resource:
http://www.endmemo.com/bio/grpm.php
Now, there might be reasons why a million g's might be a bad idea. Maybe 100K g's is a better choice. Someone with more expertise in centrifuge application could chip in and clarify this.
Not really. You'll disintegrate in strange ways based on the relative density of your constituent parts.
<edit>: Another thought is that if you laid on a bed for 13 years (the time it took for a drop of pitch to form) without moving --ignoring tissue decay and other factors-- you'd probably "flow" just as you might in a high gravity environment. Gravity, like rust, never sleeps. </edit>
Yet, unless a domain expert says otherwise, I think your point is absolutely valid. However, pitch might just be the kind of substance that would be fine at a million g's. I don't know.
That's the reason for my request for comment from someone with centrifuge experience. At a million g's a lot of seemingly strange things can happen. However, perhaps 100, 1000 or 10,000 g's is reasonable. I used the million g example as an illustration of the attainable extreme in response to a comment that spoke about 6 or 7 g's. Clearly we can do better, far better.
In consultation with a domain expert (Chemist?) I would design the experiment to give results in somewhere between a day and a month. Faster if possible. The criteria would be to choose an acceleration that does not fundamentally change the nature of the substance under test. All we want to do is promote faster flow.
Pitch is a suspension. The heavy stuff would drop to the outside, the viscosity would be affected, no experiment.
This is unlikely, however. Many suspensions have a critical pressure below which they simply will not settle. Homogenized milk, for a familiar example.
The last bit is puzzling: Are all suspensions fluids? And all fluids are viscous (even non-newtonian)?
If so, why do we need an experiment to prove that pitch --a suspension-- is a fluid and is viscous?
On the point of using a centrifuge. Is there something particularly special about gravity on earth that does not affect pitch? In other words, if we exposed pitch to 0.1x, 1x, 10x, 100x and 1000x g, at what point would the fundamental characteristics of the material invalidate the experiment. Are fluids and their viscosity only defined on earth (ignoring thermal and other non-gravitational effects)? Perhaps pitch is a viscous fluid on earth but a solid on the moon, where gravity is 1/6 of ours?
Is this experiment only valid at 9.8 m/s^2 then? What's the tolerance based on the substance under test?
Pitch can be proven to be a suspension via distillation. To prove it's a fluid, it must be observed to flow, to form a droplet, and to detach that droplet in the manner of a fluid.
However:
I think what you mean is "No, not all suspensions are fluids."Interpreting what you said literally would imply that anything that is a suspension is definitely not a fluid. And I know one can interpret what you said according to common sense to deduce that you didn't mean that, and that since some suspensions definitely are fluids, then you must have meant that there are suspensions that are not fluids.
But this is about science, and where possible, I believe we should be precise.
I believe it matters.
Unfortunately, languages don't always work the way that logicians would like them to do. Yes, we can read that sentence as the English-language summary of a logical formula (something like ∀x [Sx -> ¬Fx]), but English (and many other languages) treat the scope of the "not" as ambiguous. It's not a matter of "interpreting what you said literally", because there are multiple correct literal interpretations of what he said---he is not using a metaphor or anything. There are many cases where "not" can scope out to an enclosing quantifier (one of the better-known is "All that glitters is not gold", famously by Tolkien), and this is not just because all these speakers are in error.
[0] Also computer scientist, but I'll wear my linguist hat for now.
A sentence like "all X are not Y" naturally associates like "all X are (not Y)". Usually modifiers attach to the closest thing they can, as a matter of well-established convention. So if someone decides they want that to mean "not (all X are Y)" and expects me to understand it, I'm going to go ahead and say they're the one in error. Sorry, Tolkien.
[0] Is that a word? Chromium spell-check doesn't like it. I have lightened up on neologisms, as long as it's clear what they mean.
Unfortunately, technically inclined people like to apply their domain specific "knowledge" (compiler cosntruction?) to everything and come to incredibly bad conclusions. Ex falso quodlibet.
It gets especially bad when technical guys talk about law and juristic methodology. Demonstrated daily here on HN.
[1] BTW, linguistics is descriptive, not prescriptive. You immediately disqualify yourself from any linguistic discussion when you claim that native speakers are in error.
Note: science is not about your opinion.
> unambiguity is essential
Is it? We function in the presence of ambiguity all the time. Sometimes, we let the ambiguity ride. Sometimes, we take a sentence that is (by itself) ambiguous and let the context disambiguate it. Sometimes, we use the ambiguity for some rhetorical purpose and then resolve it later. There are many sources of ambiguity in natural language---it's one of the things that makes NLP so damn hard---and you can't wave that away by saying that everybody is doing it wrong. (Not that generations of prescriptivist grammarians haven't tried.)
> Usually modifiers attach to the closest thing they can, as a matter of well-established convention.
First of all, attachment ambiguity is a difficult NLP problem specifically because modifiers don't always attach to "the closest thing they can". Second, to the extent that the statement is true (that low, i.e. "closer", attachment has a higher prior probability than high attachment), it is not a matter of "convention" but a fact about the grammar of a language. Third, "not" is special in all sorts of ways (as is negation in general, in many languages, not just English), and as I mentioned before, this specific kind of ambiguity is well-known, and interesting because it seems so strange, and once again you can't just wave the logic stick and declare that it ought not to be so.
My answer was "No, all suspensions are not fluids". The structure depended from the phrasing of the question.
We could apply some higher acceleration for a shorter time, but that acceleration would have to be highly consistent, and there is no way to shorten the experiment enough to keep that equipment from being unproductive to even contemplate.
Sometimes patience really is the best answer.
So I read that asphalt is actually a colloid and that pitch is not the same as asphalt. The Wikipedia page on pitch [3] says it is a "viscoelastic polymer".
So I have to ask. Can a polymer be a suspension or a colloid on its own or is pitch a polymer colloid in another "host" substance?
[1] http://en.wikipedia.org/wiki/Suspension_(chemistry)
[2] http://en.wikipedia.org/wiki/Asphalt
[3] http://en.wikipedia.org/wiki/Pitch_(resin)
[4] http://en.wikipedia.org/wiki/Colloids
However, there are many suspensions which will never settle under standard gravity, but which will rapidly settle in a centrifuge. We call these colloids.
edit: also, the Earth's gravity might become a problem.
Am I the only one who finds this insulting? They could at least name the guy!!!
I'm sure the issue, if indeed there is one, is with the reporting not the scientists though.
http://joshuafoer.com/radiolab-the-pitch-drop-experiment/
It sounds like the experiment, as designed, reached a conclusion in far less time than 69 years. It just took 69 years for someone to think about video taping it.
Maybe it was a badly planned experiment (or more likely, the cost/availability of cameras in those days prohibited their inclusion in the plans). Nevertheless, no firm conclusion can be drawn that the experiment could have been ended early, those previous "drips" may not have happened without external forces applied and so even if cameras had been used it may not have ended until now. Its probably likely that it would have ended had cameras been available, but the scientific method generally calls for a greater degree of certainty than "probably likely" before calling an experiment a success.
And of course, it is called an "experiment", not a "certainty". Mistakes happen and they're not always optimal, that’s all part of the fun of science!