MatC

145932. Mon Feb 12, 2007 8:33 am 


A nice, big subject, I would have thought.
Just to get us started: “Government estimates are that the switch to digital, along with rising sales of home entertainment equipment, could boost consumer electronics’ electricity consumption by 60% by 2010.”
 Radio Times, 16 Dec 06.
That’s, um, rather a lot, isn't it? 




MatC

149370. Tue Feb 20, 2007 9:50 am 


Drivers who fly world cup flags from their cars pay “an extra pound per hour” for fuel, according to a researcher at the University of Manchester. Two flags flying from the windows of a mediumsized car causes enough drag to burn an extra litre of fuel per hour travelling at an average 30mph. He reckons that if, during the last football World Cup, half a million drivers flew flags, an extra 2.8 million kilos of carbon dioxide would enter the atmosphere.
S: Daily Mirror, 2 June 06 




dr.bob

149389. Tue Feb 20, 2007 10:12 am 


Energy is a fundamental concept in Physics. The SI unit of Energy is the Joule*. Any system requires work to change it's energy levels. Work is defined as the action of a force over a distance.
Energy is conserved. It can be neither created nor destroyed, but simply converted from one form to another. Einstein famously proved that Energy and Mass are two aspects of the same thing with his famous equation.
When newage (rhymes with sewage) practitioners talk about changing energy, or channelling energy, or removing bad energy, they are of course talking utter bollocks. By some wild outside chance there may be something tangible behind it all, but it sure ain't energy.
*James Prescott Joule (18181899) born in Sale to the family of a wealthy brewer was famous for his paddle wheel experiment where he proved that energy could be converted from one form to another. He came up with Joule's laws of energy in gases. He also famously took a thermometer on honeymoon so that when he and his new wife visited a waterfall, he was able to measure the temperature of the water at the top and at the bottom of the waterfall. The pronunciation of his surname was apparently the source of some confusion in his lifetime, which caused the brewery to come up with the following advertising slogan:
"Do you pronounce it Joule's to rhyme with schools,
Joule's to rhyme with Bowls,
or Joule's to rhyme with Scowls?
Whatever you call it, by Joule's
or Joule's
or Joule's, its GOOD!"
(http://www.ul.ie/~childsp/CinA/Issue50/misc.html) 




Gray

149445. Tue Feb 20, 2007 11:20 am 


What I find extraordinary is the amount of energy there is in matter.
If you could convert a 20g sugarlump into pure energy, for example, you'd end up with 0.02 * 3x10^8 * 3x10^8 joules. Call it 2 million billion joules.
That's enough energy to put the 2,000 tonne Space Shuttle into its usual 130km orbit.
700 times. 




dr.bob

149472. Tue Feb 20, 2007 11:51 am 


Yeah, the speed of light squared is quite a big number :) 




Flash

154961. Thu Mar 08, 2007 9:30 am 


Garrick sends this:
Quote:  E=mc^2
Q: Which scientist first proposed that the amount of energy contained in a lump of matter was equal to the lump's mass times the square of the speed of light?
FORFEIT: Albert Einstein.
A: Italian industrialist Orinto de Pretto, who published his findings in 1903. De Pretto had been speculating about Ether (the luminiferous kind, not the evaporating kind) rather than anything to do with relativity. There is some speculation that Einstein heard about De Pretto's paper (modestly entitled: "Hypothesis of the Essence of the Universe") and 'lifted' De Pretto's conclusion for his own work, published two years later in 1905, but it seems unlikely that it will ever be proven either way.
Before that, Henri Poincare had come close in 1900 when he noticed that objects emitting a 'burst' of radiation actually physically recoiled in the opposite direction to the burst. He remarked that the radiation behaved like a mass and described it: m=E/c^2 ... without ever making the vital connection.
S: The Guardian, 11 November 1999
There's also an overview of De Pretto's discovery at http://en.wikipedia.org/wiki/Olinto_De_Pretto
Notes on Poincare at: http://en.wikipedia.org/wiki/Henri_Poincar%C3%A9#Work_on_relativity 





dr.bob

155035. Thu Mar 08, 2007 11:36 am 


I'd be a bit careful about praising Olinto de Pretto. According to some of the links from the wiki article, it doesn't seem quite so convincing.
The theory was originally proposed by Umberto Bartocci in a book he published in 1998. However, according to some of the responses he gave to questions:
http://web.archive.org/web/20050222161516/http://www.dipmat.unipg.it/~bartocci/st/depretto.htm
As well as an Italian article calling into question Bartocci's ideas:
http://www.swif.uniba.it/lei/rassegna/020804a.htm
It looks as though the publication by de Pretto wasn't quite as impressive as it sounds. A lot of the stuff in the links above is in Italian, and I don't pretend to understand all of it, but it seems that de Pretto simply said that matter was made up of condensed aether (the luminiferous kind, not the evaporating kind, to coin a phrase) and that this contained a latent energy. He went on to say that this energy was:
Quote:  quantificabile con la formula mv² 
As far as I can tell, all de Pretto refers to is "the formula mv²", which the debunkers in the second url above claim is simply the classical formula for kinetic energy E = mv²/2. Bartocci himself says that:
Quote:  Which is difficult even for me to understand is why De Pretto used the formula for the socalled "forza viva" (from Leibniz), mv^2, instead of the kinetic energy, mv^2/2 ; this missing coefficient ½ gave to me a lot to think about, without arriving at any conclusion... 
If I'm reading this right, he seems to be basing his argument on de Pretto simply using mv² instead of mv²/2, which is a bit of a stretch.
On top of this, de Pretto's ideas aren't that convincing since they are based on an intuitive consideration of the problems, rather than a logically deduced mathematical treatment. For this reason, even if de Pretto did get the right equation, it may have been nothing more than a lucky guess.
Finally, on top of all that, the wiki article also links to an article by JeanPaul Auffray which points to the mathematical derivation of the equation by Henri Poincaré in 1900, predating both Einstein and de Pretto. The fact that Poincaré didn't come up with E=mc² seems to me, as a scientist, immaterial since he simply used different notation (e.g. he used "J" instead of "E" to represent the energy, and he didn't speak of the speed of light directly, but did use the dielectric constant in a vacuum, K0, which is equal to 1/c², so the speed of light was in there if you knew where to look).
So, all in all, a bit of a can of worms. 




Flash

155063. Thu Mar 08, 2007 12:24 pm 


Even Einstein first used the form m=L/c^2 (or something), the L standing for energy. 




Gray

155334. Fri Mar 09, 2007 10:21 am 


Quote:  quantificabile con la formula mv² 
I suspect that 'quantificabile' would mean something like 'is proportional to' in this context, in which case he almost certainly is talking about kinetic energy.
It's a bit of a way to substitute in the speed of light to get the total energy in the mass. That's not really how Bert got to it, at any rate... 



