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# Misconceptions of E=MC^2

Author Topic:   Misconceptions of E=MC^2
Trixie
Member (Idle past 2126 days)
Posts: 1011
From: Edinburgh
Joined: 01-03-2004

 Message 132 of 243 (453029) 02-01-2008 8:59 AM Reply to: Message 131 by bluescat4802-01-2008 8:03 AM

Re: 0.6 grams of mass lost at Hiroshima
Just for the sake of clarity, can you post the equation then underneath post it again, but with the terms replaced with moose's numbers? This might help Heinrik.

Also, given what Fat Boy did, it might be useful to tranlate the 5.4x1013 Joules into what that would do. I know we saw what it does at Hiroshima but using that may be considered cicular, so do you have a wee table that could be posted here showing varying amounts and what they can do? I think his might help to illustrate the point.

For what it's worth I'm a molecular biologist so my understanding of anything to do with physics is abysmal. I always think of E=mc2 as

"I have a lump of uranium in my hand. I wonder what the maximum amount of energy that could be released from it is? Hmm.....the amount of energy that could be released depends on how much uranium I have in the first place (ie mass, represented in the equation by "m"). If I plug that mass into the equation where "m" lives, I'll get my answer"

I know this is simplistic in the extreme, but I wonder if this helps at all?

Edited by Trixie, : Fat Boy? Fat Boy? Fat fingers more like!!!LOL

 This message is a reply to: Message 131 by bluescat48, posted 02-01-2008 8:03 AM bluescat48 has responded

 Replies to this message: Message 134 by Coragyps, posted 02-01-2008 9:20 AM Trixie has responded Message 136 by Rahvin, posted 02-01-2008 9:49 AM Trixie has responded Message 143 by bluescat48, posted 02-01-2008 1:19 PM Trixie has not yet responded

Trixie
Member (Idle past 2126 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 Rahvin02-01-2008 9:49 AM

Re: 0.6 grams of mass lost at Hiroshima
 Or enough to completely destroy everything within a 1.6 km radius.

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.

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

 This message is a reply to: Message 136 by Rahvin, posted 02-01-2008 9:49 AM Rahvin has not yet responded

Trixie
Member (Idle past 2126 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 Coragyps02-01-2008 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.

 This message is a reply to: Message 134 by Coragyps, posted 02-01-2008 9:20 AM Coragyps has not yet responded

Trixie
Member (Idle past 2126 days)
Posts: 1011
From: Edinburgh
Joined: 01-03-2004

 Message 155 of 243 (453417) 02-02-2008 6:23 AM Reply to: Message 152 by pelican02-02-2008 2:37 AM

Re: It is all english
Heinrik, do my posts help any? You'll only have to check back a few posts. I'm a complete physics turniphead so I've tried to get explanations from the physicists that avoid the formulae and include real-life situations. If you start at;

and then follow on from there you'll see what I tried to do.

Having said that, it may be so much gobbldegook. I must admit, I keep having to reboot my brain to understand even my own posts on this subject :o

 This message is a reply to: Message 152 by pelican, posted 02-02-2008 2:37 AM pelican has responded

 Replies to this message: Message 157 by pelican, posted 02-02-2008 6:36 AM Trixie has not yet responded

Trixie
Member (Idle past 2126 days)
Posts: 1011
From: Edinburgh
Joined: 01-03-2004

 Message 167 of 243 (453493) 02-02-2008 12:25 PM Reply to: Message 162 by pelican02-02-2008 9:48 AM

Re: anyone else spot a misconception of their own?
Treat the equation as you would any algebraic equation. Remember, way back when Modulus plugged numbers into it

Imagine if e=2 x 32, then e=18
So,
18=2 x 32

It follows on that 2=18/32

and also 32= 18/2

it's just pure algebra, the way you learned that if you have

x + 2 = 9

you can transform the equation to read

x + 2 - 2 = 9 - 2

I just subtracted 2 from both sides,so I can have the unknown on one side of the equals and knowns on the other side.

Simplifying we get

x = 9-2
x=7

The reason I've picked such a simple one without squares, products etc is because you actually see it in action. You know the answer before you start, so each step of the process makes perfect sense and if you don't end up with the right answer, you know you've done something wrong.

It doesn't matter how comlex an equation is or the complexity of the theory it's describing, the basic rules of algeba apply

 This message is a reply to: Message 162 by pelican, posted 02-02-2008 9:48 AM pelican has responded

 Replies to this message: Message 170 by pelican, posted 02-03-2008 1:28 AM Trixie has responded

Trixie
Member (Idle past 2126 days)
Posts: 1011
From: Edinburgh
Joined: 01-03-2004

 Message 174 of 243 (453579) 02-03-2008 9:52 AM Reply to: Message 170 by pelican02-03-2008 1:28 AM

Re: E=mc^2 = cycle of life?
All the equation does is provide a means by which you can work out the theoretical amount of energy that can be released for a given mass of a substance. While we can't measure energy directly, e can measure mass, so if we plug a value for mass into the equation at m we can then calculate the emount of energy since c is constant.

So, the only variables in the equation are mass and energy. The amount of energy is dependent on the amount of mass, similarly, if you know the amount of energy, you can calculate back to the amount of mass it came from.

So if you have a mass of 3g you will get a different answer than if you have a mass of 6g.

That's why the equation doesn't have a specific number for m or E. They are the "variables" so you can work out the energy for any given mass.

Using m=E/c2

means yu can work out the mass for any given value of E

I don't want to get into the complication of the various units that are used.

At the risk of oversimplifying (and please don't be offended, this is how I have to think all the time, especially when I'm doing calculations for dilution factors for various chemical solutions)

The number of oranges in my shopping bag is equal to the number of oranges I buy minus the number of oranges my son ate on the way home from the shops. Since I only allow him 2 oranges (because of the dreadful effects oranges have on his innards, but I better not go into that :laugh: ), then the number of oranges I manage to get home with will be the number I bought minus 2, and 2 will always be constant (given his infamous innards)

So if F is the number that finally make it into the fruitbowl, and b is the number I buy I can express it as an equation;

F=b-2

If b=6 then F=4
If b=10 then F=8
If b=4 then F=2

The reason b is used and not a number is that you can then plug any number in and the value of F depends on the value of b which is variable (depending on how much money I have on give day).

Edited by Trixie, : You don't want to know, believe me

 This message is a reply to: Message 170 by pelican, posted 02-03-2008 1:28 AM pelican has not yet responded

Trixie
Member (Idle past 2126 days)
Posts: 1011
From: Edinburgh
Joined: 01-03-2004

 Message 199 of 243 (453732) 02-03-2008 9:56 PM Reply to: Message 197 by pelican02-03-2008 9:02 PM

Heinrik, the post linked to below may help you to understand where Parasomnium is coming from (and molbiogirl)

It's a PNT and the entire text reads

 Fact: Laws are considered more reliable than theoriesFact: Evolution, specifically abiogenesis, contradicts the Second Law of ThermodynamicsFact: Usually, theories which contradict laws are discardedTherefore: Evolution as a theory should be discarded until a more suitable theory of the origins of life is proposed

That post on 29.1.08 is the latest in a long line of posts like this. This sort of thing comes up again and again and does become tedious. For this reason, if even a hint is present that a poster might think in this way, it's corrected ASAP because it really is a huge barrier to understanding science.

I also think there has been a misunderstanding by many since the beginning of this thread and I can include myself in that. I really thouht that the topic was to discuss the misconceptions that scientists have with E=mc2. It became apparent as the discussion progressed that you wanted to discuss your misconceptions.

Don't take this the wrong way, I am not trying to criticise you, I'm only trying to offer an explanation. It's not on topic either, but I'm hoping that it can pour oil on troubled waters and let you continue getting info from Modulus.

 This message is a reply to: Message 197 by pelican, posted 02-03-2008 9:02 PM pelican has responded

 Replies to this message: Message 200 by pelican, posted 02-03-2008 10:32 PM Trixie has not yet responded Message 201 by pelican, posted 02-03-2008 10:37 PM Trixie has responded

Trixie
Member (Idle past 2126 days)
Posts: 1011
From: Edinburgh
Joined: 01-03-2004

 Message 202 of 243 (453744) 02-03-2008 10:46 PM Reply to: Message 201 by pelican02-03-2008 10:37 PM

Yes, I think you have the right to do that. This thread has been a terrific one and I hope it continues - you do know that you got a nomination for post of the month and it was seconded by Quetzal? Sadly, you don't get any sweeties or anything for it (I asked, but none were forthcoming), just the knowledge that a post of yours has contributed in a big way to this forum.

Admin - I promise this is the very, very last off topic post. It's here because it does flow nicely through the thread and the thread demonstrates so well where ALL of us can improve our communication.

Edited by Trixie, : My little spiel to Admin is so obviously off the mark that I felt I should point it out as being a total load of bullshit, with the exception of it being the last off-topic post from me.

 This message is a reply to: Message 201 by pelican, posted 02-03-2008 10:37 PM pelican has responded

 Replies to this message: Message 206 by pelican, posted 02-04-2008 3:43 AM Trixie has not yet responded

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