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Author Topic:   Misconceptions of E=MC^2
Rahvin
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Posts: 4032
Joined: 07-01-2005
Member Rating: 9.2


Message 136 of 243 (453040)
02-01-2008 9:49 AM
Reply to: Message 132 by Trixie
02-01-2008 8:59 AM


Re: 0.6 grams of mass lost at Hiroshima
A conversion tool that will translate between megatons (1 megaton is the equivalent of 1 million tons of TNT exploding, for those unaware) and Joules (the standard unit of energy) can be found here.
It's really interesting to see how much energy is in even a small nuclear weapon. Little Boy, for instance, was only about 15 kilotons (0.15 megatons), making it pretty small compared to the large weapons currently existing.
To translate Joules into something more easily recognized by those who haven't taken physics in a while, 1 Joule is equal to 1 Watt of power for 1 second. So:
1 Watt = 1 Joule/1 second
and
1 Joule = 1 Watt * 1 second
Since people are more used to seeing kilowatt-hours (like on your power bill), here's a handy conversion:
(1 kilowatt*hour)*(1000 W/kW)*(3600 secs/hour) = 3,600,000 Watts*seconds = 3,600,000 J = 3.6 * 10^6 Joules (or 3.6 MJ)
So 1 megaton would be the equivalent of 1162222222.22 kilowatt-hours.
Little Boy would be 6.276 * 10^16 Joules, so 1.743 * 10^7 kilowatt-hours
Or enough to completely destroy everything within a 1.6 km radius.
And that was just over one half of one gram of matter being converted into energy.
For those who find themselves incredulous at the amount of energy the equation E=MC^2 says is released when matter is converted into energy...there's your proof, right there. It's why nuclear reactors like those used by the Navy let ships go for years without refueling except for ammunition, crew changes, and supplies for the crew.
Edited by Rahvin, : No reason given.

When you know you're going to wake up in three days, dying is not a sacrifice. It's a painful inconvenience.

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cavediver
Member (Idle past 3643 days)
Posts: 4129
From: UK
Joined: 06-16-2005


Message 137 of 243 (453051)
02-01-2008 10:14 AM
Reply to: Message 135 by Rahvin
02-01-2008 9:21 AM


Re: 0.6 grams of mass lost at Hiroshima
In both nuclear explosions and chemical explosuions, the energy released comes from the binding energy - binding energy of the nucleus and binding energy of the atoms/molecules.
This is different from antimatter/matter annihilation, however, where the particles are actually fully transformed into high-energy photons. Is that correct?
Yes, that is 'real' matter to non-matter. The rest mass of the electron and positron is released as energy which dictates the frequency of the two emitted photons.

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Trixie
Member (Idle past 3706 days)
Posts: 1011
From: Edinburgh
Joined: 01-03-2004


Message 138 of 243 (453052)
02-01-2008 10:14 AM
Reply to: Message 136 by Rahvin
02-01-2008 9:49 AM


Re: 0.6 grams of mass lost at Hiroshima
Or enough to completely destroy everything within a 1.6 km radius.
Perfect. The reason I've asked for this is cos Heinrik asked if E=mc2 had been tested.
So, if the application of the formula to the amount of material used up at Hiroshima results in the amount of energy which would be required to do exactly what was done at Hiroshima, (avoiding what was done at Hiroshima to determine what that amount of energy would do cos otherwise we get circular again)then we have an application of the formula where it has been tested in the real world and found to be accurate, something that Heinrik is asking for.
I'm just trying to get all of this into a format which Heinrik will understand.
Thanks for your patience guys.
Oh, and my explanation for "Fat Boy" is that I was listening to Fatboy Slim (Right Here, Right Now) while I was writing my post and my brain short-circuited LOL

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Trixie
Member (Idle past 3706 days)
Posts: 1011
From: Edinburgh
Joined: 01-03-2004


Message 139 of 243 (453053)
02-01-2008 10:17 AM
Reply to: Message 134 by Coragyps
02-01-2008 9:20 AM


Re: 0.6 grams of mass lost at Hiroshima
Sorry I missed this in my previous post. This is exactly the sort of thing I meant. It means we get "real world" equivalents that non-scientists can relate to.

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Tanypteryx
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Posts: 4344
From: Oregon, USA
Joined: 08-27-2006
Member Rating: 5.9


Message 140 of 243 (453057)
02-01-2008 10:36 AM
Reply to: Message 137 by cavediver
02-01-2008 10:14 AM


Re: 0.6 grams of mass lost at Hiroshima
This is a little off topic, but I know the emitted photons will be at 511 KeV, but what is their frequency?

What if Eleanor Roosevelt had wings? -- Monty Python
You can't build a Time Machine without Weird Optics -- S. Valley

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cavediver
Member (Idle past 3643 days)
Posts: 4129
From: UK
Joined: 06-16-2005


Message 141 of 243 (453059)
02-01-2008 10:42 AM
Reply to: Message 140 by Tanypteryx
02-01-2008 10:36 AM


Re: 0.6 grams of mass lost at Hiroshima
I know the emitted photons will be at 511 KeV, but what is their frequency?
If there's only two photons, and the the electron/positron were low energy (i.e low Kinetic Energy) then the photons will be 511KeV. E = h x v, where h is Plancks Constant and v is frequency (Greek nu actually), so a quick calc and you find that they are Gamma Ray photns with a freq of....

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Tanypteryx
Member
Posts: 4344
From: Oregon, USA
Joined: 08-27-2006
Member Rating: 5.9


Message 142 of 243 (453119)
02-01-2008 12:52 PM
Reply to: Message 141 by cavediver
02-01-2008 10:42 AM


Re: 0.6 grams of mass lost at Hiroshima
v=7.711838623^35
is this cycles per second? In a former life (many years ago) I used to do gamma spectrometry using a Canberra ultrapure germanium detector....I have forgotten a lot since I got a real life.
Edited by Tanypteryx, : No reason given.

What if Eleanor Roosevelt had wings? -- Monty Python
You can't build a Time Machine without Weird Optics -- S. Valley

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bluescat48
Member (Idle past 4189 days)
Posts: 2347
From: United States
Joined: 10-06-2007


Message 143 of 243 (453125)
02-01-2008 1:19 PM
Reply to: Message 132 by Trixie
02-01-2008 8:59 AM


Re: 0.6 grams of mass lost at Hiroshima
Trixie
Also, given what Fat Boy did, it might be useful to tranlate the 5.4x1013 Joules into what that would do.
try the amount of energy required to move 54 million kilograms 1 kilometer
Edited by bluescat48, : No reason given.

There is no better love between 2 people than mutual respect for each other

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cavediver
Member (Idle past 3643 days)
Posts: 4129
From: UK
Joined: 06-16-2005


Message 144 of 243 (453127)
02-01-2008 1:32 PM
Reply to: Message 142 by Tanypteryx
02-01-2008 12:52 PM


Re: 0.6 grams of mass lost at Hiroshima
v=7.711838623^35
I think you've got your enegy units mixed up h is usually in Joule seconds.
1 eV = 1.610^’19 J.

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Tanypteryx
Member
Posts: 4344
From: Oregon, USA
Joined: 08-27-2006
Member Rating: 5.9


Message 145 of 243 (453150)
02-01-2008 2:31 PM
Reply to: Message 144 by cavediver
02-01-2008 1:32 PM


Re: 0.6 grams of mass lost at Hiroshima
OK, thanks I think I've got it now....maybe
1 eV = 1.610^’19 J.
511 KeV = 8.2x10^-14 J
511 KeV photons have a frequency of 7.7^38

What if Eleanor Roosevelt had wings? -- Monty Python
You can't build a Time Machine without Weird Optics -- S. Valley

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johnfolton 
Suspended Member (Idle past 5591 days)
Posts: 2024
Joined: 12-04-2005


Message 146 of 243 (453260)
02-01-2008 6:37 PM


mass * the speed of light squared = energy ?
Like when .6 grams explode are little prisons of excessive energy being released from say those .6 grams not just from the present but from the past, and future?
It just seems that energy has been trapped within little prisons thru time in the atom. That the energy of the atom is not trapped just in the present but flows from the past thru the present into the future.
Is this a part of the theory of relativity in respect to mass * the speed of light squared = energy?

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molbiogirl
Member (Idle past 2641 days)
Posts: 1909
From: MO
Joined: 06-06-2007


Message 147 of 243 (453273)
02-01-2008 6:54 PM
Reply to: Message 146 by johnfolton
02-01-2008 6:37 PM


Re: mass * the speed of light squared = energy ?
Like when .6 grams explode are little prisons of excessive energy being released from say those .6 grams not just from the present but from the past, and future?
What on god's green earth does time have to do with E=mc2? Do you see a "t" in there? I don't see a "t" in there.

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johnfolton 
Suspended Member (Idle past 5591 days)
Posts: 2024
Joined: 12-04-2005


Message 148 of 243 (453295)
02-01-2008 7:23 PM
Reply to: Message 147 by molbiogirl
02-01-2008 6:54 PM


Re: mass * the speed of light squared = energy ?
What on god's green earth does time have to do with E=mc2? Do you see a "t" in there? I don't see a "t" in there.
The formula was based on an object at rest once mass exceeds this it involves time thus relativity, etc...
---------------------------------------------------------------
This mass is the ratio of momentum to velocity, and it is also the relativistic energy divided by c2. So the equation E = mrelc2 holds for moving objects. When the velocity is small, the relativistic mass and the rest mass are almost exactly the same.
E = mc2 either means E = m0c2 for an object at rest, or E = mrelc2 when the object is moving.
Mass—energy equivalence - Wikipedia

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molbiogirl
Member (Idle past 2641 days)
Posts: 1909
From: MO
Joined: 06-06-2007


Message 149 of 243 (453299)
02-01-2008 7:30 PM
Reply to: Message 148 by johnfolton
02-01-2008 7:23 PM


Re: mass * the speed of light squared = energy ?
The formula was based on an object at rest once mass exceeds this it involves time thus relativity, etc...
Wrong.
This mass is the ratio of momentum to velocity, and it is also the relativistic energy divided by c2. So the equation E = mrelc2 holds for moving objects. When the velocity is small, the relativistic mass and the rest mass are almost exactly the same.
E = mc2 either means E = m0c2 for an object at rest, or E = mrelc2 when the object is moving.
Mass—energy equivalence - Wikipedia
Einstein is rolling over in his grave.
E= mc2. Period. If time were a factor, it would have been included in the equation.

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johnfolton 
Suspended Member (Idle past 5591 days)
Posts: 2024
Joined: 12-04-2005


Message 150 of 243 (453309)
02-01-2008 7:51 PM
Reply to: Message 149 by molbiogirl
02-01-2008 7:30 PM


Re: mass * the speed of light squared = energy ?
Your formula is only based on time in mass not in motion however when you explode an atomic bomb the mass goes into motion. Thus E = mrelc2 is more relative to an atomic bomb explosion as compared to E=mOc2, etc....
----------------------------------------------------------
In particle accelerators, particles are moving very close to the speed of light where the length and time effects are large. This has allowed us to clearly verify that length contraction and time dilation do occur.
Observations particles with a variety of velocities have shown that time dilation is a real effect. In fact the only reason cosmic ray muons ever reach the surface of the earth before decaying is the time dilation effect.
Research | SLAC National Accelerator Laboratory
Edited by johnfolton, : No reason given.
Edited by johnfolton, : No reason given.

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