5 ms·

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

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. [1] http://www.nature.com/news/world-s-slowest-moving-drop-caught-on-camera-at-last-1.13418 http://www.nature.com/news/world-s-slowest-moving-drop-caugh...

darkchasma 13y ago
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.
- robomartin 13y ago
  No, you could go a million times faster. A million! Here's an interesting resource: http://www.endmemo.com/bio/grpm.php 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.
  - jerf 13y ago
    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).
    - robomartin 13y ago
      > At a million g's, I'm a 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.
      - jerf 13y ago
        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.
        robomartin 13y ago
        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.
samatman 13y ago
Chemist here. We use centrifuging to separate components of a suspension by weight. Pitch is a suspension. The heavy stuff would drop to the outside, the viscosity would be affected, no experiment.
- samatman 13y ago
  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.
- robomartin 13y ago
  > 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?
  - samatman 13y ago
    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.
qwerta 13y ago
This is Ireland 1949, they probably did not had money for centrifuge.
scythe 13y ago
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.

darkchasma 13y ago

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.

robomartin 13y ago
No, you could go a million times faster. A million! Here's an interesting resource: http://www.endmemo.com/bio/grpm.php 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.
- jerf 13y ago
  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).
  - robomartin 13y ago
    > At a million g's, I'm a 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.
    - jerf 13y ago
      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.
      - robomartin 13y ago
        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.

samatman 13y ago

Chemist here. We use centrifuging to separate components of a suspension by weight. Pitch is a suspension. The heavy stuff would drop to the outside, the viscosity would be affected, no experiment.

samatman 13y ago
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.
robomartin 13y ago
> 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?
- samatman 13y ago
  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.

qwerta 13y ago

This is Ireland 1949, they probably did not had money for centrifuge.

scythe 13y ago

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.