Evangelista Torricelli was born on October 15th, 1608 – we could commemorate his birthday ten days ago – and died of typhoid fever contracted a few days earlier in Florence exactly 365 years ago, on October 25th, 1647.

This early physics worker is mainly remembered for the discovery of the barometer and for his simple law in hydrodynamics.

He was born in the Papal States, was left fatherless as a kid, and was brought up by his uncle. When Galileo was convicted in June 1633, he openly declared himself a member of the "Copernican sect". During the last 3 months of Galileo's life, Torricelli was employed as the master's personal secretary (writer). But what we remember him for is the barometer. An experiment by some random people whom we no longer remember was actually needed to invent the device.

## snail feedback (7) :

That's a nice and enjoyable reading, thanks Lumo.

One a different topic, couldn't we say that a superstring is a particle traveling in a second dimension (perhaps small) of time?

Sorry but no. A string means that the object itself has one additional dimension of space. The dimensions of space in which an object is moving is a totally independent thing, and string theory requires 9 (or, in the case of M-theory, 10) spatial and 1 time dimension for consistency.

One may also consider objects moving in spacetimes with 2 times but none of these theories is quite physical, as far as the known ones go. Two time dimensions mean that there are closed timelike curves in the 2-dimensional purely timelike plane and that's a problem, maybe even if one of the dimensions is small.

Nah, I thougth Cumrun Vafa and friends do quite welll ;-)

Dear Dilaton, the two extra toroidal dimensions in F-theory have "signature" (timelike vs spacelike) that isn't quite clearly determined.

If you want to derive the 9+1-dimensional spinors of type IIB string theory from 12 dimensions, you need the signature 10+2, indeed, suggesting 2 timelike dimensions.

However, there are also arguments that the two extra toroidal dimensions must have the same signature, i.e. the total is either 11+1 or 9+3. This follows from the form of the moduli space in type IIB string theory, SL(2, Z) \ SL(2,R) / SO(2,R). Here, SO(2,R) is only justified as a symmetry - one we divide by - if the two extra dimensions have the same signature, otherwise there would be SO(1,1,R).

There's no real contradiction here because the extra dimensions in F-theory are infinitesimally small ones so their proper length is really zero, so you can't say whether it's 0 real or 0 pure imaginary, whether it's timelike or spacelike.

Thank you Sir for an exposition of chronological events in science. Today I learned a lesson to not undervalue our failure. In corroboration to what you said I would like to add a quote on one of my professors webpage "If at first you don't succeed, try to act surprised........

Martin DeMello, B.Tech IIT-B Engg. Phy. '97" :)

:-D

Post a Comment