Tim Cook nous apporta ses lumieres en ce 2007/10/29 23:29:
> Darren New wrote:
>> Tim Cook wrote:
>>> Darren New wrote:
>>>> Name energy that isn't in the form of mass?
>>>> Then explain what E=mc^2 means.
>>>
>>> Light isn't in the form of mass.
>>
>> Yes it is. Photons have mass. Indeed, the reason they go the speed of 
>> light is (sloppily speaking) that they are *all* energy, so they 
>> *have* to go the speed of light just to have mass to hold the energy.
>>
>>> Sound isn't in the form of mass. 
>>
>> The atoms move to make sound. Sound is kinetic energy, which is mass 
>> due to relativistic movement.
>>
>>> Electricity isn't in the form of mass.  
>>
>> Electrons move, hence kinetic energy, hence mass.
>>
>>> Magnetism isn't in the form of mass.  
>>
>> Magnetism consists of photons. Photons have mass.
>>
>>> E=mc^2 means that the amount of energy stored in a given mass can be 
>>> determined by multiplying the mass by the speed of light squared. 
>>
>> Equally, it says that the amount of energy can be determined by 
>> multiplying the amount of mass by the speed of light squared. That's 
>> an equal sign there. That's how relativity works.
>>
>> Where does the kinetic energy in a moving asteroid go if I accelerate 
>> my spaceship up to the same speed? Does the stationary observer see 
>> more energy than the observer moving at the same speed? Wouldn't that 
>> mean that energy can be created and destroyed at will, just by moving 
>> the observer without changing the experiment? Do you understand why 
>> leaving a gravity well makes you heavier?
>>
>> I know what you're trying to say. You're trying to say that there is 
>> energy that's not the equivalent of mass, and that E=mc^2 only applies 
>> to mass, not energy.
> 
> No, I'm trying to say that...mass is a specific form of energy, as are 
> all those other forms of energy, but they aren't each other.  Sound is 
> not light, because it has defining properties that are different. 
> Otherwise we'd just call everything 'energy'.  It's like...number sets. 
>  Energy is the set of all numbers, mass is the set of all positive 
> integers, light is the set of all negative primes, and so forth.  You 
> can convert one to another with a bit of fiddling, but they aren't 
> congruent subsets.
> 
Energy IS mass! It's just that in everyday experiance, that mass is aparently to 
small to be perceived.
Take an electron, accelerate it suficiently, and you can make it's mass grow to 
rival that of a TRAIN or even a SUPER TANKER! Where does this mass increase 
comes from? Uniquely from the kynetic energy of that speeding electron.
Now, take that electron and make it collide with any other particle. You will 
get a HUGE gamma burst. Gamma radiation is light. The kynetic energy mass gets 
transformed into light. And remember: light can push objects. It's just that 
this push is normaly to small for you to notice, but it can easily be 
demonstrated with a very simple experiment.
Take an empty globe of glass, place a needle holding a light rotor made from a 
glass axis and holding 3 or 4 blades, white on one side, black on the other. 
Place the rotor on the needle. Remove all air from the globe. Have ANY light 
shining on that rotor, even a candle light, and the rotor will spinn. That 
experiment is over 100 years old!

-- 
Alain
-------------------------------------------------
An unbreakable toy is useful for breaking other toys.

Post a reply to this message