The limitations of common sense

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If that were always true then panning for gold wouldn't work

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How does that affect gold panning? As far as my common sense tells me, that rule holds true always. The only reason two objects might fall at different speeds would be a difference in the surface area/weight ratio.

LOL.btw - I thought that was the topic?(Subtitle: "or why good thinking goes bad ..." )

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we are limited in our ability to understand
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RebelAAmerican.Zen[Deist
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Try it on a remote road. Take a cannonball - so it is heave and dense and does not have a lot of wind resistance. Use an assistant to drive, and another to film it.My prediction is that it will land even with the car, at which point the massive friction of hitting the earth will cause sever changes in speed, direction, spin, etc.Think of the cannonball being thrown horizontally at the speed of the car - it would have the same trajectory - we would not expect it to stop (or even slow appreciably) forward motion as soon as it leaves the hand.The problem is viewpoint - your frame of reference. To a person outside the car the cannonball will have the same horizontal speed as the car, but inside the car you don't see or feel that speed. Again, this is the frame of reference problem: to an observer in space in, say, a lagrange {point\orbit} (hence having a relatively 'fixed' location relative to the earth-moon (okay, closer) or earth-sun (better but further) system - so it doesn't have orbital velocity per se about the earth - the air mass will be seen to be moving in sinc (mostly) with the land masses, more so the lower the observable (clouded) air masses are. They have speed we don't see or feel because of our speed (that we don't see or feel).

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RebelAAmerican.Zen[Deist
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Panning for gold works because the density of gold is higher than the density of other gravel material. The {nuggets\grains\specks} of gold sink to the bottom of the pan as it is jiggled for the same reason that rocks sink in water. Thick water. So too is it used to help launch space craft (what percentage of satellites are in "retro-grade" orbits eh?)

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RebelAAmerican.Zen[Deist
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It does?

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RebelAAmerican.Zen[Deist
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Gallileo's calculations hold well in air especially if you take into account air resistance. Paning for Gold however probably has more to do with the Brazil Nut Effect than anything else and this is an area of physics that is still not well understood. The Brazil Nut Effect is a perfect example of counterintuitive physics and in fact is so good that nobody knows yet how or why it works in many cases. It is interestingly, also a good example of order from chaos.

Maybe you guys have never actually panned for gold?RAZD was closest that it has to do with density; gold ores are denser than stone and so have more inertia, so as you cast the pan from side to side, the gravel tends to shoot out the top while the intertia of the gold tends to keep it in place.To put it in perspective - most river-source gold ore was collected not by panning - which is really more of a survery technique - but by running riverwater through a flume, which is a watercourse where the water is made to change direction sharply through several narrow turns or baffles that force the water up.As the water hanges direction, the heavier gold's intertia carries it into catch traps while the lighter gravel is carried on out of the flume course with the water. This is similar to the way that sediments are deposited in natural river runs.Not exactly on topic, but it's physics, and I thought you all might appreciate a look at gold rush technologies. I think tin is still largely mined this way, with devastating environmental consequences, around most of the Pacific Rim.

Granular convection - WikipediaCute, but it's a boundary effect.Home – Physics World: Presumably at 4 times the mass and twice the diameter they stay mixed ... (this study only used two sizes of round particles){abe}Note, that twice the diameter means 8 times the volume, so the same density material would have 8 times the mass ... {/abe}The specific gravity of gold is ~19 and the specific gravity of average gravel is ~3, and that's about 6 to 1 just for fun, and with both particles the same size.Between the effect of size and the effect of density you can see how panning and similar techniques were effective in sorting gold from gravel with many different sized particles of each in the mix.And while we're on the subject of Gold and Common Cents ... (sorry)Do you think you could pick of one cubic foot of gold?Enjoy.This message has been edited by RAZD, 04*11*2006 01:01 AM

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RebelAAmerican.Zen[Deist
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And what if you change the parameters slightly to born within a day of the same day (ie +/- 1 day)?"Common" sense would say 1/3rd the size (~7) ... because one person now takes care of as many days as 3 people took for the same day calculation ...or maybe less, right?{clarified}This message has been edited by RAZD, 04*11*2006 12:55 AM

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RebelAAmerican.Zen[Deist
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You're describing orbital velocity, not escape velocity. Because the air's travelling along with the land. (just like the oceans do)

Ok, this is what we can call the error of assumption of linearity. There must be many examples of this in everyday life...The actual answer is between 14 and 16, depending on how many of the birthdays actually fall within two days of each other (as two birthdays a day apart only restricts 5 days from the calendar, not 6)

Dominion Seraph Thank you for the correction you are,of course, right. Did you know. though, that the use of the term velocity in escape velocity is not quite correct? Really? Would you care to tell us how that works?
Since the earth is a soid mass it is understandable that it wold move as a unit. However, air and water are both fluid, and thus would seem to not be likely to flow in the same way due to their "viscosity".
Why does the air and ocean travel as though,they too,were solid?

Discreet LabelSorry I took so long replying. Yes, this will do for the purpose of our discussion

cavediverI think this would make a fascinating topic on its own concerning the errors that science has uncovered through investigation. Can you put together a listing in columnists corner that we can use to refer to whenever we have the opportunity? It would be great if we could have examples and possibly some questions thrown in to have us dig through the list to see if we can identify errors properly.I really appreciate your input since this is probably the closest I will ever have to actually going and getting an education through regular schools.That means a lot to me.A question occurs to me also. When you were growing up and questions in physics and math were being presented to you in what way would you go about tackling new concepts?

RAZD But what is it that allows us to differentiate between this as a consequence of a planet rotating on its axis and one that is not? It would seem that the same situation is present in either scenario.
This also ties back into the OP since I was initially trying to validate the position of the assumption that the Earth spins on its axis?
I am also curious as to what other "common sense" discrepencies might occur to someone who does not quite understand the interrelationship of various lines of knowledge?