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Evangelista Torricelli

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  Quote rider Quote  Post ReplyReply Direct Link To This Post Topic: Evangelista Torricelli
    Posted: 19-Feb-2006 at 12:40

Who knows this one?

My physics teacher told me about this one teaching us about air pressure. Well, i found the name interesting and found some cool things about him... (I haven't yet got the time to read it).

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  Quote Maju Quote  Post ReplyReply Direct Link To This Post Posted: 19-Feb-2006 at 22:49
I just know he invented the barometer that bears his name (aka mercury column). He did it by going to a mountain with the tube and marking the heigth of the mercury at the diferent altitudes - though this is surely oversimplistic.

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  Quote Leonardo Quote  Post ReplyReply Direct Link To This Post Posted: 20-Feb-2006 at 11:19

Originally posted by Maju

I just know he invented the barometer that bears his name (aka mercury column). He did it by going to a mountain with the tube and marking the heigth of the mercury at the diferent altitudes - though this is surely oversimplistic.

 

Probably you get confused the experiment of Torricelli and the Blaise Pascal's one



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  Quote rider Quote  Post ReplyReply Direct Link To This Post Posted: 20-Feb-2006 at 11:53
Yes, even though Torricelli discovered the pressure of air by putting a tube with Hydrogentum into a bowl with Hydrogentum until the Hydrogentum flowed till a border at 760 mm. (Or cm).
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  Quote Leonardo Quote  Post ReplyReply Direct Link To This Post Posted: 20-Feb-2006 at 12:32

Torricelli was the last pupil of the old Galileo

 

He is popularly famous for the invention of the barometer and the demonstration of the existence of air pressure:

The experiment described by Torricelli was really first performed by Vincenzo Viviani, another pupil of Galileo:

 

Sometimes Torricelli is considered the father of the science of phoronomy:

 

He is famous also as a mathematician and he is considered among the precursors of the invention of Calculus.

In fact in Italy the fundamental theorem of Calculus is named Torricelli (or Torricelli-Barrow) theorem



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  Quote Maju Quote  Post ReplyReply Direct Link To This Post Posted: 21-Feb-2006 at 00:10
So was I right or wrong? It seems he did invent the mercury column barometer.

Rider what the heck is hydrogentum? Mercury? Hg is Mercury...

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  Quote Leonardo Quote  Post ReplyReply Direct Link To This Post Posted: 21-Feb-2006 at 08:30
I guessed you confused the invention of the barometer by Torricelli and the experiment carried out by by Florin Prier, the brother-in-law of Blaise Pascal, consisting in carrying up the Puy de Dme two glass tubes containing mercury, inverted in a bath of mercury and noting the fall of the mercury columns with increased altitude.
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  Quote Leonardo Quote  Post ReplyReply Direct Link To This Post Posted: 21-Feb-2006 at 08:39
Hg for mercury is from the latin Hydrargyrum (from a greek word meaning "liquid silver").
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  Quote Maju Quote  Post ReplyReply Direct Link To This Post Posted: 21-Feb-2006 at 12:48
Originally posted by Leonardo

I guessed you confused the invention of the barometer by Torricelli and the experiment carried out by by Florin Prier, the brother-in-law of Blaise Pascal, consisting in carrying up the Puy de Dme two glass tubes containing mercury, inverted in a bath of mercury and noting the fall of the mercury columns with increased altitude.


I thought they were the same development (and obviously I attributed it to Torricelli). How could Torricelli determine that there is an atmospheric pressure without changing the altitude?

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  Quote Leonardo Quote  Post ReplyReply Direct Link To This Post Posted: 22-Feb-2006 at 02:13

Originally posted by Maju

Originally posted by Leonardo

I guessed you confused the invention of the barometer by Torricelli and the experiment carried out by by Florin Prier, the brother-in-law of Blaise Pascal, consisting in carrying up the Puy de Dme two glass tubes containing mercury, inverted in a bath of mercury and noting the fall of the mercury columns with increased altitude.


I thought they were the same development (and obviously I attributed it to Torricelli). How could Torricelli determine that there is an atmospheric pressure without changing the altitude?

 

One can reason this way: in the tube remains a column of mercury, why doesn't it descend completely? The mercury column has a weight, so there must be something that conter-balances it maintening it in equilibrium. This "something" must be the column of air impending on the free surface of the bath, so, contrary to Aristoteles and other ancient philosphers thinking, air must have a weight.

If this is right, then if you bring the tube on the top of a mountain the column of air above the bath must be lesser, and weighting lesser, and so also the column of mercury in the tube must be lesser to gain equilibrium ...

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  Quote Maju Quote  Post ReplyReply Direct Link To This Post Posted: 22-Feb-2006 at 16:35
How logical and simple! 

Thanks.

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  Quote rider Quote  Post ReplyReply Direct Link To This Post Posted: 23-Feb-2006 at 07:17
Well, for me, as I do not know the chemical elements' English names tried to use the original form, thinking that Hg would be Hydro + gentum 8from Argentum, Ag - Silver). It seems, I made a mistake in my logic.
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  Quote Leonardo Quote  Post ReplyReply Direct Link To This Post Posted: 23-Feb-2006 at 07:55

Originally posted by rider

Well, for me, as I do not know the chemical elements' English names tried to use the original form, thinking that Hg would be Hydro + gentum 8from Argentum, Ag - Silver). It seems, I made a mistake in my logic.

 

Your guess was not totally wrong  

Infact the latin word argentum is related to the greek word argyros (meaning "silver"), so Hydrargyrum is a greek word with a latin ending (-um).

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  Quote Serge L Quote  Post ReplyReply Direct Link To This Post Posted: 25-Feb-2006 at 09:24
I confirm what was previously stated. Just some precisations:

At the time of Torricelli, scientists knew that if you put some close tube in one liquid, f.i. water, and then raise it , the liquid would stay in the closed tube, even though that would seem to defy gravity laws.
The common explanation for this fact was that "nature had horror for vacuum" (horror vaqui in Latin, the universal scientific language of that time).
The intuition of Torricelli was that that phenomenon was not due to "horror of vacuum", but because the air pressure compensates the pressure due to the weight of the liquid, up to a certain point.
Torricelli demonstrated that over that certain point (760 mm for mercury) the closed pipe has vacuum in it (the so-called torricellian vacuum)
A good intuiton by Toricelli was to use mercury, i.e. one of the heaviest liquids he could easily find. If he had used water, he had to use a pipe higher than 10 m.

As to he ancient name of mercury, derived from the Greek "Hydrargyrion", as my compatriot Leonardo clearly stated, it came from the (false) idea that mercury was a liquid form of silver. There also is an English term for that, i.e. quicksilver.


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  Quote rider Quote  Post ReplyReply Direct Link To This Post Posted: 27-Feb-2006 at 11:53

Oh, thank yuo all for correcting me.

Interesting but I believe that it was 766 mm for mercury.

Well, all else I agree with.

I never realized that with water the pipe had been higher for the test...

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  Quote Serge L Quote  Post ReplyReply Direct Link To This Post Posted: 28-Feb-2006 at 18:23
Well conventionally, 1 atmosphere (unit of measure, approx. corresponding to the average pressure of earth's atmosphere at sea level) is considered equal to 760 mm Hg (or 760 Torr, just from the  name of Torricelli). However it's certainly possible hat, sometimes and somewhere actual pressure could be 766.

However, for more info you can have a look at Wikipedia:
http://en.wikipedia.org/wiki/Mm_Hg
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