The Naked Scientists

The Naked Scientists Forum

Author Topic: Is negative energy real?  (Read 11945 times)

Offline jaiii

  • Sr. Member
  • ****
  • Posts: 114
    • View Profile
Is negative energy real?
« on: 01/03/2011 17:32:42 »
Hello.

In Casimir phenomenon between metal plates create a negative energy.
How can I manage this power.

Thank
« Last Edit: 24/03/2011 08:40:45 by chris »


 

Offline imatfaal

  • Neilep Level Member
  • ******
  • Posts: 2787
  • rouge moderator
    • View Profile
Re: Is negative energy real?
« Reply #1 on: 02/03/2011 12:06:25 »
Jaiii - do you mean casimir effect? 

If so it is only an heuristic interpretation that it produces negative energy.  The effect can be viewed through either the perspective of zero-point energy of the quantized field,  the interaction and annihilation of virtual particles, or even basis van de waal forces. 

The casimir effect is that two conducting metallic plates will experience a force when close enough together - I would have through the only way to get energy from such a system would be from the movement of these plates. However they are damn close to each other so any movement will either remove them from the proximity that allows the effect or make them touch.  It was only in 2001 that precision of instruments allowed the casimir force between plates to be actually measured in a lab - to actually harness this minuscule force to provide energy is not likely.
 

Offline graham.d

  • Neilep Level Member
  • ******
  • Posts: 2208
    • View Profile
Re: Is negative energy real?
« Reply #2 on: 02/03/2011 12:17:49 »
Matthew, even igoring the proximity of the plates, it is hard to see any mechanism for getting energy out. The best you could do is have the system act as a sort of mechanical battery where you expend energy pulling the plates apart and then get it back by allowing them to pull themselves together again.
 

Offline imatfaal

  • Neilep Level Member
  • ******
  • Posts: 2787
  • rouge moderator
    • View Profile
Re: Is negative energy real?
« Reply #3 on: 02/03/2011 13:02:13 »
Graham - exactly.  I should have put that as well.  You could extract a minuscule amount of energy from a system already set up by allowing the plates to move, but further than that you would only get out in the mechanical battery sense as you describe.
 

Offline jaiii

  • Sr. Member
  • ****
  • Posts: 114
    • View Profile
Re: Is negative energy real?
« Reply #4 on: 02/03/2011 15:28:13 »
I see.Thank for reply.

And if the boards were strongly attached to the frame and echoed by the EM field with small freqvenci.
« Last Edit: 02/03/2011 15:41:44 by jaiii »
 

Offline imatfaal

  • Neilep Level Member
  • ******
  • Posts: 2787
  • rouge moderator
    • View Profile
Re: Is negative energy real?
« Reply #5 on: 02/03/2011 17:47:49 »
Jaiii; force and energy are not the same thing.  If the plates don't move no energy.  The negative energy I think you are getting at is a mental trick to help explain why the force might arise
 

Offline jaiii

  • Sr. Member
  • ****
  • Posts: 114
    • View Profile
Re: Is negative energy real?
« Reply #6 on: 02/03/2011 19:10:47 »
I do not know whether I misunderstood the previous contributions but said that the board must move.
So that if they resonate in the EM field plate will move.
Can you explain to me Vcom, is the problem?

Thank you
 

Offline Jolly- Joliver

  • Hero Member
  • *****
  • Posts: 584
    • View Profile
Re: Is negative energy real?
« Reply #7 on: 02/03/2011 21:07:28 »
Hello.

In Casimir phenomenon between metal plates create a negative energy.
How can I manage this power.

Thank


Just as a question when it comes to Negative energy, are we talking about the opposite of positive energy? That would imply a positive, neutral and negative forms of energy. Yet energies appear to repel an electron and proton move away from each other.

Could there be four types positive + and - and a negative + and -? As both + and - are positive or negative, they repel, where as a negative + and positive + would attract or vice-versa the positive + and negative - attract or are actually the same thing with a different structure?

Just an idea, come on:- Feynman suggested there was just one electron in the whole universe.

I'm not not a scientist just a thinker.
« Last Edit: 02/03/2011 21:09:42 by Wiybit »
 

Offline imatfaal

  • Neilep Level Member
  • ******
  • Posts: 2787
  • rouge moderator
    • View Profile
Re: Is negative energy real?
« Reply #8 on: 03/03/2011 11:14:54 »
Wiybit - negative energy is very hypothetical and definitely not accepted mainstream.  It would imply negative mass - and both negative energy and mass are not completely at home as energy conditions in GR solutions.

The Casimir effect can be viewed as creating a volume of space with a negative energy density in comparision to the vacuum energy of free space; this is really the by far the nearest to a real manifestation of negative energy (and it's not that close).   The fact that this negative energy is postulated because of an absence of theoretical item should definitely not be viewed as ruling it out.  In very different circumstances which has huge parallels - the positron was first theorised as the absence of a negative energy electron (the absence of a negatively charged negative energy particle being the same as the presence of a positively charged positive energy anti-particle).  I think that also engages with the second half of your question - we should be able to deal with negative amounts of negative energy as positive amounts of normal energy (and so on); but that makes the massive presumption that negative energy exists in a non-hypothetical manner.

Jaiii - can't understand your last
 

Offline jaiii

  • Sr. Member
  • ****
  • Posts: 114
    • View Profile
Re: Is negative energy real?
« Reply #9 on: 03/03/2011 12:01:49 »
OK. I will thought abou it and try Internet.

Thank
 

Offline Jolly- Joliver

  • Hero Member
  • *****
  • Posts: 584
    • View Profile
Re: Is negative energy real?
« Reply #10 on: 24/03/2011 06:18:56 »
Wiybit - negative energy is very hypothetical and definitely not accepted mainstream.

yeah I posed questions not statements.



It would imply negative mass - and both negative energy and mass are not completely at home as energy conditions in GR solutions.

A black hole is hardly a positive mass, but anyway.


The Casimir effect can be viewed as creating a volume of space with a negative energy density in comparision to the vacuum energy of free space; this is really the by far the nearest to a real manifestation of negative energy (and it's not that close).   The fact that this negative energy is postulated because of an absence of theoretical item should definitely not be viewed as ruling it out.  In very different circumstances which has huge parallels - the positron was first theorised as the absence of a negative energy electron (the absence of a negatively charged negative energy particle being the same as the presence of a positively charged positive energy anti-particle).  I think that also engages with the second half of your question - we should be able to deal with negative amounts of negative energy as positive amounts of normal energy (and so on); but that makes the massive presumption that negative energy exists in a non-hypothetical manner.

They were questions not statements, they leave open that possibility.


 

Offline JMLCarter

  • Sr. Member
  • ****
  • Posts: 143
    • View Profile
Is negative energy real?
« Reply #11 on: 24/03/2011 11:24:35 »
Evidence suggest energy cannot be created or destroyed, only transformed from one form into another.

The genuine existence of real negative energy would violate that observation. As in

 +1 + -1 = 0

(the energy has gone  :-(  )
 

Offline imatfaal

  • Neilep Level Member
  • ******
  • Posts: 2787
  • rouge moderator
    • View Profile
Is negative energy real?
« Reply #12 on: 24/03/2011 13:53:20 »

It would imply negative mass - and both negative energy and mass are not completely at home as energy conditions in GR solutions.
A black hole is hardly a positive mass, but anyway.
Of Course it is.  Whilst we have very little idea of the details of what lies within the event horizon, we are pretty certain the black hole has mass.

JMLC - yeah I like that approach.
 

Offline JP

  • Neilep Level Member
  • ******
  • Posts: 3366
  • Thanked: 2 times
    • View Profile
Is negative energy real?
« Reply #13 on: 25/03/2011 00:24:36 »
Evidence suggest energy cannot be created or destroyed, only transformed from one form into another.

The genuine existence of real negative energy would violate that observation. As in

 +1 + -1 = 0

(the energy has gone  :-(  )

Though 0 = 1 + -1 is exactly what led Dirac to postulate antimatter.  Negative energy is associated with antimatter in the Dirac equation.  It all gets a lot more complicated, but I believe that negative energy is still a useful concept for modeling antimatter.  (A negative energy electron is a positron, for example.)
 

Offline yor_on

  • Naked Science Forum GOD!
  • *******
  • Posts: 12001
  • Thanked: 4 times
  • (Ah, yes:) *a table is always good to hide under*
    • View Profile
Is negative energy real?
« Reply #14 on: 25/03/2011 00:44:38 »
And so it comes down to what 'energy' really, and I mean really, ah, is?
Myself I have this nagging suspicion, I think it is round? I base that on the idea of infinity and it's absolute partner and opposite, zero. And that's a very round number, isn't it?

I like Dirac :)
 

Offline Phractality

  • Hero Member
  • *****
  • Posts: 523
  • Thanked: 1 times
    • View Profile
Is negative energy real?
« Reply #15 on: 25/03/2011 07:12:33 »
I prefer to think of it as the positive potential required to separate the atoms from one another. When they are brought close enough they lose that potential. The force of attraction is the potential per unit of distance. Potential is a gauge phenomenon; the choice of zero potential is arbitrary. If you define zero potential as separated atoms, then joined atoms are at a negative potential. So they only go negative relative to your arbitrary ground state.   
 

Offline JMLCarter

  • Sr. Member
  • ****
  • Posts: 143
    • View Profile
Is negative energy real?
« Reply #16 on: 25/03/2011 09:51:21 »
Well the charge of a positron is positive, (opposite of the electron). However the mass is not negative mass.

Hence I am thinking the energy is not negative energy.

(assuming zero energy is chosen to match "no particle")

I'd be keen to know if Dirac has to say anything different? As I understand it his <a| and |b> wave functions must interact to form an observation of a particle; it's not that they are +ve and -ve, but that they are the sqrt of a probability distribution function. I won't pretend I fully get Dirac though.
 

Offline Madidus_Scientia

  • Neilep Level Member
  • ******
  • Posts: 1451
    • View Profile
Is negative energy real?
« Reply #17 on: 25/03/2011 13:27:33 »
Would you solve the Dirac Equation?
 

Offline JP

  • Neilep Level Member
  • ******
  • Posts: 3366
  • Thanked: 2 times
    • View Profile
Is negative energy real?
« Reply #18 on: 25/03/2011 15:45:40 »
Well the charge of a positron is positive, (opposite of the electron). However the mass is not negative mass.

Hence I am thinking the energy is not negative energy.

I'm not a dirac equation expert, though I've worked through it a bit in my school days.  You're right, I think.  I was throwing out antiparticles as a devil's advocate.  However, there is still something interesting to the idea.  At the level of quantum mechanics, a lot of what is "physical" depends on how you interpret the mathematics.  As far as I know, it's a valid interpretation to say that antiparticles can be particles with negative energy.  It's probably not the best interpretation, since it's much more intuitive to consider them as positive mass, opposite charge, etc., but it's still valid, I think.
 

Offline imatfaal

  • Neilep Level Member
  • ******
  • Posts: 2787
  • rouge moderator
    • View Profile
Is negative energy real?
« Reply #19 on: 25/03/2011 15:53:58 »
Hate to cast doubt on the fount of all knowledge - but are you sure JP?  Anti-particles can be seen as particles with opposite time line (ie in feynman diagrams)- but surely not as particles with negative mass / negative energy.  Dirac's initial conception of the positron was as a gap in the negative energy (and charge) sea - a gap in the negative energy sea is positive energy
 

Offline JP

  • Neilep Level Member
  • ******
  • Posts: 3366
  • Thanked: 2 times
    • View Profile
Is negative energy real?
« Reply #20 on: 25/03/2011 17:11:06 »
Hate to cast doubt on the fount of all knowledge - but are you sure JP? 
On this one, yes.  :)

Quote
Anti-particles can be seen as particles with opposite time line (ie in feynman diagrams)- but surely not as particles with negative mass / negative energy.  Dirac's initial conception of the positron was as a gap in the negative energy (and charge) sea - a gap in the negative energy sea is positive energy
It would seem that way, but I'm quite positive on the fact that the antiparticles are solutions to the Dirac equation with E<0.  This comes from the particles essentially satisfying E2=m2c4 in their rest frame.  If you take the square root on the left-hand side, you get both positive and negative-energy solutions.  The negative energy solutions are anti-electrons.

The other reason I'm sure is that this is often the reason that quantum mechanics describes the time evolution of particles by a term that contains Et, the product of the energy times time.  If you reverse the energy, this term "runs backwards" in time, meaning that E=1, and t=1 looks the same as E=-1, t=-1.  This is the basic idea behind negative energy particles running backwards in time.

I think the term "hole" comes from the idea that if you think traditionally about energy and negative energies are allowed, an electron should keep emitting photons and dropping to the lowest possible value, which is unbounded in this case.  So Dirac had to propose that all the negative energies in the universe were usually filled up, so the electron couldn't drop below zero.  However, if there is a vacant spot in the negative energy sea, this acts as a positron with negative energy, but positive charge.  I never really learned much of the details of the Dirac sea because it has fallen out of favor (clearly thinking of space as filled with infinitely positrons has issues--namely with infinite energy at any point in space).  More modern interpretations still deal with negative energy, though, in the senses I mentioned above, and in particular with it inducing a "backwardsness" in time.  Again, I think most physicists don't consider negative energy to be physical, just a useful mathematical tool.  I believe that generally positrons are thought of as positively charged antiparticles rather than negative-energy electrons, but the mathematical trick is still interesting.

Here's a link I found to one of my graduate textbooks on the subject, which has parts available by Google books.  Check out pages 576-577, which describes it a bit (thankfully without relying on equations!):
http://books.google.com/books?id=2zypV5EbKuIC&pg=PA581&dq=shankar+principles+of+quantum+mechanics&source=gbs_toc_r&cad=3#v=onepage&q&f=false
 

Offline imatfaal

  • Neilep Level Member
  • ******
  • Posts: 2787
  • rouge moderator
    • View Profile
Is negative energy real?
« Reply #21 on: 25/03/2011 17:55:16 »
Damn - now I have started it, I will have to read up on it!  Well only thing I had to do this weekend was watch england-sri lanka... now I have some physics to curdle my brains with.

I knew I shouldn't have contradicted JP  [B)]
 

Offline yor_on

  • Naked Science Forum GOD!
  • *******
  • Posts: 12001
  • Thanked: 4 times
  • (Ah, yes:) *a table is always good to hide under*
    • View Profile
Is negative energy real?
« Reply #22 on: 25/03/2011 18:45:48 »
Sweet stuff JP.
 

Offline JP

  • Neilep Level Member
  • ******
  • Posts: 3366
  • Thanked: 2 times
    • View Profile
Is negative energy real?
« Reply #23 on: 26/03/2011 01:04:52 »
I knew I shouldn't have contradicted JP  [B)]

Of course!  I'm never wrong!

:p

Well, this one I'm pretty sure on because I actually studied it in pretty good detail.  I still agree with you and others that negative energy isn't really a physical thing, though mathematically it's a useful trick.  Of course, in QM, separating mathematics and "reality" is always a bit murky and multiple interpretations can be equally plausible.
 

Offline Geezer

  • Neilep Level Member
  • ******
  • Posts: 8328
  • "Vive la résistance!"
    • View Profile
Is negative energy real?
« Reply #24 on: 26/03/2011 01:55:23 »
I'm fairly sure JP won't be watching England v Sri Lanka, unless he acquired the cricket bug in Singapore.
 

The Naked Scientists Forum

Is negative energy real?
« Reply #24 on: 26/03/2011 01:55:23 »

 

SMF 2.0.10 | SMF © 2015, Simple Machines
SMFAds for Free Forums