I can my self move any megalithic stone on hundreds of tons with physics

[sethoflagos]

5 hours ago, swansont said:

"Add more mercury" is a new item The OP had a fixed amount. There is no more mercury to add.

I think I'm going to treat this as 'information only'. 

m1/a1 = m2/a2 is the relation to focus on. I refer and defer to @J.C.MacSwell 

[swansont]

13 minutes ago, jlivingstonsg said:

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Please learn some physics.

 

https://www.quora.com/Is-it-possible-to-float-a-100-ton-boat-in-just-1-ton-of-water/answer/Kim-Aaron?ch=10&oid=303591043&share=33e3ccd4&target_type=answer

 

Master of Science in Engineering Physics

The problem is that's not the situation you described. You need to have this container on all sides, so the water is not free to flow away from the object that is floating. You lose this once you "dig up in front of it"

 

(P.S. I fixed the link in your post. URL shorteners don't normally fly here.)

[TheVat]

39 minutes ago, exchemist said:

Oh, my commiserations. Hope it goes well and they get it all out.

I dimly remember a derivation of Archimedes' principle at school, based on calculating the upthrust, from pressure at a point at given depth, due to a column of liquid above, multiplied by the area in cross-section, parallel to the surface, of the object to be floated. This gives you a force equal to the weight of fluid occupied by the object.  So I think all you need is a column of fluid of sufficient depth to make a "hole" that it big enough. It's the hole that does it, rather than the fluid that would be in it.  

 

Thanks.  I think this makes sense.  When you have the 100 ton boat floated with one ton of water, in a tight rigid container, it helps to consider the container itself.  The boat does not "sense" any difference between the tight container and a vast pool of water of that depth.  The displacement matters, not where that displaced water is, so long as the column is deep enough.

And thanks for commiserations.  Much better to have a divot than a bump.  I'm going to fill it with water and see what I can float.

 

[exchemist]

59 minutes ago, jlivingstonsg said:

-------------------------

Please learn some physics.

 

https://www.quora.com/Is-it-possible-to-float-a-100-ton-boat-in-just-1-ton-of-water/answer/Kim-Aaron?ch=10&oid=303591043&share=33e3ccd4&target_type=answer

 

Master of Science in Engineering Physics

 

 

 

Quora is a lousy reference source to rely on, and adopting such a snooty tone won't win you any friends, but I now agree you were right about the principle of this - and I was was initially wrong. So I've learnt something. 

However the notion that neolithic people actually floated megaliths in mercury is still outlandish, for the reasons given in this thread.   

Edited July 1, 2022 by exchemist

[studiot]

1 hour ago, jlivingstonsg said:

Please learn some physics.

Really ?

And I object to someone claiming a Masters in Physics (note there are PhD's and above here) producing no Physics at all here.

Please read the rules about needing to go offsite.

 

In any case Seth has already pointed out the simple fact that Archimedes does not apply here.
Archimedes applies when the bouyant object is musch much smaller than the immersion medium.
So the state and geometry of the immersion medium (ocean. lake, atmousphere etc) is not changed by the immersion.

What does apply is used in foundation engineering where fluid pressure is an important consideration.

It is emminently possible that fluid pressure could be applied to reduce the burden of horizontal force required to drag the stones along. After all fluid pressure has tipped over our concrete dams and othere structures in the past.

 

Finally a question for you.

If you did manage to float a large heavy stone in an even larger and heavier tub of mercury; how would you move the whole sheebang, given that you are floating it in the mercury to get over its weight in the first place ?

Please provide a specific Physics answer not hand waving.

[J.C.MacSwell]

2 hours ago, swansont said:

The pressure in the fluid (above atmosphere) will be pgh, where p is the density and h is the depth of the fluid. 

In my example h is 10^-2 m.

The pressure will be about 100 Pa. But your area is 10^-4 m^2. How are you lifting 5 N with that?

 

Here's my brief thought: Archimedes principle says that the buoyancy force is equal to the weight of the liquid displaced. If you have a smaller mass displaced, the weight will be greater than the buoyancy force, and the object will sink.

Now it's your turn: back up your claim. Where does the force come from to float the object?

That's the starting h. h raises until 1. the pole bottoms out, as you seem to realize....

OR 2.  if the container is barely larger than your pole h raises enough to provide adequate pressure to float the cylinder.

Not sure why you think that in 2.  it would always require a mass of fluid greater or equal to the mass of the cylinder to allow the pole to float.

Maybe if you used a less extreme example you could more readily see it

I tried that here:

13 hours ago, J.C.MacSwell said:

A 20 cm x 20 cm x 10 cm high  (approx 3.6 kg )block of ice will float in your bath tub..due to the pressure difference on the bottom from that of the top, which will be about 1 cm above the surface of the water.

Now make a smaller tank 21 cm x 21 cm x 11 cm high.  Add 1 litre of water (approx 1 kg). Water level approx 2.27 cm from bottom.

Now carefully place into it the above 3.6 kg block, into the tank with the 1 kg of water. Water level will rise.

The water level will be the same as for 4.6 litres of water, about 10.43 cm from the bottom, and the block will float about 1 cm above that, and with the top surface above the top of the tank. 

 

[swansont]

11 minutes ago, J.C.MacSwell said:

That's the starting h. h raises until 1. the pole bottoms out, as you seem to realize....

OR 2.  if the container is barely larger than your pole h raises enough to provide adequate pressure to float the cylinder.

Not sure why you think that in 2.  it would always require a mass of fluid greater or equal to the mass of the cylinder to allow the pole to float.

It's my example. And I was trying to point out that the object can bottom out. Naturally, I will use an example where that will happen. ("there needs to be enough of the fluid present for this to happen. Otherwise it will bottom out.")

Others are telling me that no it will not bottom out, and using their own examples. But that doesn't rebut my claim. All I need is one example where it bottoms out and my claim is true. And any claim that it won't bottom out are false.

All the rest is just moving the goalposts. You're rebutting something, but not my claim. I'm not addressing situation 2 (though there is still a minimum fluid amount required). I never was.

[J.C.MacSwell]

5 minutes ago, swansont said:

It's my example. And I was trying to point out that the object can bottom out. Naturally, I will use an example where that will happen. ("there needs to be enough of the fluid present for this to happen. Otherwise it will bottom out.")

Others are telling me that no it will not bottom out, and using their own examples. But that doesn't rebut my claim. All I need is one example where it bottoms out and my claim is true. And any claim that it won't bottom out are false.

All the rest is just moving the goalposts. You're rebutting something, but not my claim. I'm not addressing situation 2 (though there is still a minimum fluid amount required). I never was.

Here's the assertion we've taken issue with.

 

On 6/30/2022 at 8:03 AM, swansont said:

That violates Archimedes principle: an object will displace its own weight of the fluid. If it is less dense it will float, BUT there needs to be enough of the fluid present for this to happen. Otherwise it will bottom out. So 500 kg of mercury (a little less than 100L) will not float anything over 500 kg. exchemist notes this above.

Can you now understand why it does not follow that "500 kg of mercury (a little less than 100L) will not float anything over 500 kg"?

[sethoflagos]

2 hours ago, studiot said:

In any case Seth has already pointed out the simple fact that Archimedes does not apply here.

To be fair, I never actually mentioned Archimedes. Whether his principle 'applies' or not depends on how you visualise it, and it is clear from the posts here that there is quite a variety in these visualisations.

Rather, I simplified by picking a convenient horizontal reference plane (the base of the monolith is an obvious candidate) and checked for isostatic equilibrium. ie that any given area (A) on that plane supported a vertical column of mass m such that m/A was constant. (and where mg/A equals gauge pressure) 

Hence a small mass m1 acting on a small area A1  will be in isostatic equilibrium with (ie 'balances' or 'floats') a large mass m2 acting on an area A2 iff m1/A1 = m2/A2

This approach also immediately identifies @swansont's vertical wooden pole as a significant mass acting on a small area. Hence it requires a much larger liquid depth to establish isostatic equilibrium than a horizontal pole would.

Beats worrying about individual buoyancy forces anyway. 

 

 

[mistermack]

On the practicalities of using this method, it's probably not as work intensive as I first thought. 

If you are excavating a new gap in front each time, and filling in behind, then you can end up with a trench ready made for the next rock. All you need to do is to use one or two ready cut rocks to fill in at the rear, and keep re-using the same ones as you go along, so you are leaving behind a cut trench to use again. And if you had a good supply of mercury, then you could move forward in reasonable sized steps, rather than inching forwards. Once your trench was cut, you could keep re-using blocking stones at the front, same as at the rear. 

Not that I'm any closer to thinking that this is what they did. 

Going uphill would have to be very gradual, you would have to treat it like a system of canal locks. 

And you would probably have found evidence of mercury production by now, although it would be hard to tell whether it was cinnebar that they were producing, or mercury metal. I believe that mercury evaporates at room temperature so it would be unlikely to find any left over from 5,000 years ago. 

https://www.livescience.com/earliest-evidence-mercury-poisoning  

[jlivingstonsg]

https://googlethatforyou.com?q=ancient liquid mercury

[Ken Fabian]

So many issues, fun in a thought experiment kind of way but for actually moving big blocks of stone... no. 

If I am getting this right there is a trench that is mercury tight that can be opened up ahead and filled in behind and sealed to be fully mercury tight at every stage, with that excavation/reconstruction being done whilst full (or else mercury ladled out each time - no suction can lift mercury higher than about 760mm). Enough mercury to float the block forward a small way (that still leaves room for the excavation/reconstruction ahead and behind), ladle out the mercury, fill in behind, open up in front, refill, repeat. Wider trench and more mercury for any bends. Fully recover the mercury for re-use without losing significant amounts ...

This is supposed to be an easier way to move big blocks of stone?

[sethoflagos]

1 hour ago, Ken Fabian said:

This is supposed to be an easier way to move big blocks of stone?

The OP has clearly gone for an extreme scenario to gain attention.

He could just as easily have loaded his megalith onto an adequately large barge and pulled it along a conventional canal or pre-existing waterway. This technology was not beyond our forebears and the underlying physics is moreorless identical. It's just a little less clickbaity. 

 

[jlivingstonsg]

I just see this event in front of me.

Hundreds of years ago people found mercury and they could see that the most heavy stones floated in mercury.

So they started floating bigger and bigger stones just by curiosity.

Then some king said he wanted a house of large stones. 

And it ended with stones in balbeck.

 

Regards from Sweden

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[exchemist]

30 minutes ago, jlivingstonsg said:

I just see this event in front of me.

Hundreds of years ago people found mercury and they could see that the most heavy stones floated in mercury.

So they started floating bigger and bigger stones just by curiosity.

Then some king said he wanted a house of large stones. 

And it ended with stones in balbeck.

 

Regards from Sweden

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That is mere speculation on your part, with no evidence to support it, and it is impractical for several reasons, as this thread has pointed out.  

[mistermack]

Since the majority of stones used in the pyramids were rough cut, uneven in shape, it doesn't seem likely that this method WAS used, otherwise they would have been more carefully trimmed to a standard size fit a trench. Also, having a quick read, the vast majority of the stones were about 2.25 tons in weight. This suggests that they found this size fairly easy to transport, otherwise they would have used smaller ones. Lifting them up each level wouldn't have been too hard, using ramps and levers. Basically, you would just need a lot of manpower. 

The moving of blocks up to 60 tons would have been a different story, but again, ramps and levers can work wonders, if you have hundreds or even thousands of experienced hands available. 

[studiot]

16 hours ago, mistermack said:

Going uphill would have to be very gradual, you would have to treat it like a system of canal locks. 

I just have visions of megalithic mercury man scratching his head when he came to this signpost.

Today, of course, he would just use a Falkirk Wheel.

🙂

Edited July 2, 2022 by studiot

[jlivingstonsg]

1 hour ago, mistermack said:

Since the majority of stones used in the pyramids were rough cut, uneven in shape, it doesn't seem likely that this method WAS used, otherwise they would have been more carefully trimmed to a standard size fit a trench. Also, having a quick read, the vast majority of the stones were about 2.25 tons in weight. This suggests that they found this size fairly easy to transport, otherwise they would have used smaller ones. Lifting them up each level wouldn't have been too hard, using ramps and levers. Basically, you would just need a lot of manpower. 

The moving of blocks up to 60 tons would have been a different story, but again, ramps and levers can work wonders, if you have hundreds or even thousands of experienced hands available. 

I am just talking about the largest megalithic stones on 500 to 1000 tons.

The smaller ones was probably moved under boats in water,

in a constructed water channel system.

 

Regards from Sweden

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[Bufofrog]

1 hour ago, jlivingstonsg said:

I am just talking about the largest megalithic stones on 500 to 1000 tons.

And the members have pointed out your idea wouldn't work, so the size of the stones is irrelevant.

[TheVat]

20 minutes ago, Bufofrog said:

And the members have pointed out your idea wouldn't work, so the size of the stones is irrelevant.

Except insofar as sizes of 500 to 1000 tons underscore the utter preposterousness of using an impromptu Panama Canal of mercury locks in an era when extracting a few ounces of mercury would have been an extraordinary feat of metallurgy.  This is all a gedankenexperiment and quite a silly one.  

 

[jlivingstonsg]

5 minutes ago, TheVat said:

Except insofar as sizes of 500 to 1000 tons underscore the utter preposterousness of using an impromptu Panama Canal of mercury locks in an era when extracting a few ounces of mercury would have been an extraordinary feat of metallurgy.  This is all a gedankenexperiment and quite a silly one.  

 

I am just talking abouty moving megalithic rocks a meter at a time in a hole in the ground.

Here is some information on mercury in ancient times.

https://mysteriousunexplainedhistory.com/what-are-liquid-mercury-pools-doing-underneath-ancient-pyramids/

 

MagI

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[Bufofrog]

31 minutes ago, jlivingstonsg said:

Here is some information on mercury in ancient times.

Gee, what a great source!  They have a lot of great information on aliens, the pharaohs flying in planes and bigfoot.

[Externet]

7 hours ago, jlivingstonsg said:

So they started floating bigger and bigger stones just by curiosity.

Now we are into larger and larger stones.  Perhaps the answer is :

[mistermack]

4 hours ago, jlivingstonsg said:

I am just talking about the largest megalithic stones on 500 to 1000 tons.

Have you got a link for that, or did you dream it?

I've just done some looking up, lacking a link, and the biggest megaliths seem to have been the obelisks, and they did run to hundreds of tons. The Romans moved several of them to Rome on specially made ships. There is no mention of mercury so the good old sleds and winches and levers seem to have done the job. It must have been a phenomenal undertaking to see. 

such a shame all that work was done for no useful purpose.

 

https://en.wikipedia.org/wiki/Obelisk  

[sethoflagos]

4 hours ago, jlivingstonsg said:

I am just talking about the largest megalithic stones on 500 to 1000 tons.

The smaller ones was probably moved under boats in water,

in a constructed water channel system.

 

Regards from Sweden

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The Baalbek quarry is close by and a little higher than the site where the trilithons were placed. No need to lift.

Other than people power, placement would appear to need little more than a well-levelled road, rollers, rope and capstans, all of which the Romans could manage quite routinely, yes?

Not saying that it was an easy job, they seem to have given up after installing three (up to 800 tonnes each), leaving at least three more unfinished back in the quarry. 

However, with a simple solution staring us in the face, why go looking for a more far-fetched explanation?