The Naked Scientists

The Naked Scientists Forum

Author Topic: What Are Virtual Particles?  (Read 9858 times)

Offline boombox

  • First timers
  • *
  • Posts: 3
    • View Profile
What Are Virtual Particles?
« on: 28/09/2008 04:51:48 »
do they violate causality? can it's effect preced it's cause?


 

Offline niall

  • Jr. Member
  • **
  • Posts: 10
    • View Profile
What Are Virtual Particles?
« Reply #1 on: 01/10/2008 23:35:35 »
Its been a while, but here goes...
It all stems from the Hysenburg uncertainty principal. Basically this is a quantum physics law that deals with measuring stuff really really accurately. The form that's useful here says ΔEΔt ≥ plank's constant (i.e. the-uncertainty-of-our-energy-measurement times the-uncertainty-of-our-time-measurement is greater than a very small number). This means there is a limit to how accurately we can measure these two things together for a particle.
The point is there is room for a bit of energy (ΔE, i.e. a particle) to be created from nothing AS LONG as it goes back to being nothing before its time (Δt) is up - if its around too long then ΔEΔt ≥ plank's constant, we can measure it and its no longer a virtual particle but a real one!
This is the basis for loads of stuff - for instance electron of like charge that come too close together repel each other by the exchange of virtual photons.
I'm sure someone will smack me down for not getting it quite right but that's the basics i think
 

Offline socratus

  • Sr. Member
  • ****
  • Posts: 329
    • View Profile
What Are Virtual Particles?
« Reply #2 on: 05/10/2008 13:05:06 »
What are virtual particles?
==========
1.
Quantum theory says that “ virtual particles “ can exist in Vacuum.
QT says that from these “ virtual particles “ the real particles
can be born. It is very pity, but physicists don’t explain that
parameters these “virtual particles“ have and how they become real.

2.
“niall “ wrote:
This is the basis for loads of stuff - for instance electron of like charge
 that come too close together repel each other by the exchange
of virtual photons.

Nobody knows where the electron hides its “virtual photon”.
Nobody knows what “virtual photon” is.

3.
So:
Electron must have “friend- virtual photon”.
Electron must have “girl-friend  - positron”.
But when  electron interacts  with vacuum
he doesn’t have any friends.
All his  parameters become infinite.

It is strange Electron’s story.
Maybe therefore Robert Milliken, who measured a charge
 of electron, in his  Nobel speech ( 1923) told,  that he knew
 nothing about “last essence of electron”.
4.
In that case there is one old joke.
One professor asked a student:
“ What is an electron?”
“ Ah, God damn it! I have forgotten. And in fact even in the
 morning I knew it. ”- the student answered.
“ You should recollect it without fail, - professor said –
 because you were the unique person who knew, what
 electron was, and you had suddenly forgotten!”

This old joke does not grow old.
==============.
 

Offline boombox

  • First timers
  • *
  • Posts: 3
    • View Profile
What Are Virtual Particles?
« Reply #3 on: 06/10/2008 07:12:11 »
Its been a while, but here goes...
It all stems from the Hysenburg uncertainty principal. Basically this is a quantum physics law that deals with measuring stuff really really accurately. The form that's useful here says ΔEΔt ≥ plank's constant (i.e. the-uncertainty-of-our-energy-measurement times the-uncertainty-of-our-time-measurement is greater than a very small number). This means there is a limit to how accurately we can measure these two things together for a particle.
The point is there is room for a bit of energy (ΔE, i.e. a particle) to be created from nothing AS LONG as it goes back to being nothing before its time (Δt) is up - if its around too long then ΔEΔt ≥ plank's constant, we can measure it and its no longer a virtual particle but a real one!
This is the basis for loads of stuff - for instance electron of like charge that come too close together repel each other by the exchange of virtual photons.
I'm sure someone will smack me down for not getting it quite right but that's the basics i think
what do you mean "The point is there is room for a bit of energy (ΔE, i.e. a particle) to be created from nothing AS LONG as it goes back to being nothing before its time (Δt) is up"?
 

lyner

  • Guest
What Are Virtual Particles?
« Reply #4 on: 06/10/2008 10:21:52 »
I think it's important to avoid trying to be too literal in ones view of these things.
As I have frequently pointed out. There is no answer to the question "What is it really?"
The best we can do is to describe things in terms of their behaviour.
You can get somewhere if you say something behaves 'as if it were a particle'. You just can't say it IS a particle. That allows you to say that the same thing, at other times, can behave 'as if it were a wave' or 'as if it were a force'.
Unfortunately, such a liberal view takes the wind out of the sails of many contributors who want a definitive answer and who rant about things from a position of ignorance rather than getting better informed.
 

Offline socratus

  • Sr. Member
  • ****
  • Posts: 329
    • View Profile
What Are Virtual Particles?
« Reply #5 on: 09/10/2008 07:25:24 »
I think it's important to avoid trying to be too literal in ones view of these things.
As I have frequently pointed out. There is no answer to the question "What is it really?"
The best we can do is to describe things in terms of their behaviour.
You can get somewhere if you say something behaves 'as if it were a particle'. You just can't say it IS a particle. That allows you to say that the same thing, at other times, can behave 'as if it were a wave' or 'as if it were a force'.
Unfortunately, such a liberal view takes the wind out of the sails of many contributors who want a definitive answer and who rant about things from a position of ignorance rather than getting better informed.

It means that sophiecentaur wrote:
we cannot understand what particle (for example, electron ) is.


I think , if we understand the particle’s behaviour
( for example, electron) we will understand the real Nature.
===================================
 

Offline niall

  • Jr. Member
  • **
  • Posts: 10
    • View Profile
What Are Virtual Particles?
« Reply #6 on: 20/10/2008 13:06:56 »
Firstly I agree sophiecentaur - you can't ask "yeh but what is it really". The best thing to do when dealing with this kind of stuff is just except that its mind blowing and on such a different scale that you can't even begin to get your head round it "really". Better to try and imagine a model in you head of whats going on. I love listening to Richard Feynman - one of the all time great theoretical physicists and all round alternative thinkers - talking about visualising stuff like this as, say, a purple ball, then someone tells you somthing else about it and the balls grows hair, or changes colour or whatever. Here's Feynman talking about the "inconcievable nature aof nature" newbielink:http://uk.youtube.com/watch?v=AU8PId_6xec [nonactive].

Quote
what do you mean "The point is there is room for a bit of energy (ΔE, i.e. a particle) to be created from nothing AS LONG as it goes back to being nothing before its time (Δt) is up"?
So what I was trying to say was that, bottom line, that law cannot be broken. The reason these particles can be created "out of thin air" is that they cease to exist before we could possibly measure them at all, thus, in some sense not really ever existing at all so not breaking the law!
What I don't understand (which someonen else could explain?) is - if a virtual photon is exchanged between two charged things i.e. in the EM interaction, it affects the particles and is, therefore, measurered. So does it cease to be virtual.

So I wanted to talk about a couple of things socratus said:
Quote
1.
Quantum theory says that “ virtual particles “ can exist in Vacuum.
QT says that from these “ virtual particles “ the real particles
can be born. It is very pity, but physicists don’t explain that
parameters these “virtual particles“ have and how they become real.
There's so much more to virtual particles than that. Physicists do explain how they become "real" particles. It depends what your talking about when you say real particles for a start. "Pair production" is when two virtual photons collide and the energy is turned into a parrticle and an anti particle. This virtual -> real concersion is done by the most famous physics law of all time E = mc^2. This particle/antiparticle pair then have to anihilate before detection (into photons again) in order not to violate the hysenburg uncertanty pricipal. That does explain how it happens in a vacuum bacuse a vacuum can have energy (photons) in it that can momentarily create these particles.

Quote
Nobody knows where the electron hides its “virtual photon”.
Nobody knows what “virtual photon” is.
I'm not sure what you mean by "hide." It doesn't need to hide it, its energy. It just needs to have it! I totally disagree with this point. And I still think exchange of virtual photons is the basis of EM force

Phew that was a long one
 

Offline labview1958

  • Sr. Member
  • ****
  • Posts: 104
    • View Profile
What Are Virtual Particles?
« Reply #7 on: 20/11/2008 14:13:59 »
Does electrons move in orbits around a nucleus in an atom. My hunch electrons exist only outside an atom. Inside an atom they are just energy.
 

Offline yor_on

  • Naked Science Forum GOD!
  • *******
  • Posts: 12001
  • Thanked: 4 times
  • (Ah, yes:) *a table is always good to hide under*
    • View Profile
What Are Virtual Particles?
« Reply #8 on: 03/12/2008 10:15:58 »
Electrons are expressions of probability:)
But, yes they orbits the 'nucleus' of an atom.
they are treated as particles but due to Heisenberg uncertainty principle they are not to be pinpointed.
http://www.bbc.co.uk/dna/h2g2/A408638

Also they seem to 'jump' in discrete jumps out/in depending on their energy content.
There is no smooth descent or ascent to them moving around a atoms nucleus.
As for what is the in or outside of an atom?
I suppose the electron sort of define the radius of it but depending on energy-content it as stated 'jumps' between 'valence bands'.

The atom consists of somewhere around 99.999(?) 'empty space'
You can read more about it here
http://particleadventure.org/frameless/atom_fund.html

And here is a 'movie' of an electron.
http://legerdemain.wordpress.com/2008/02/23/electronthe-movie/

-------

Virtual particles seems to exist. The reason why we think so is that there are 'interactions' between them and the rest of our spacetimme.
http://en.wikipedia.org/wiki/Virtual_particles#Manifestations

Although
" Virtual particles are an artifact of perturbation theory that give an intuitive (but if taken too far, misleading) interpretation for Feynman diagrams. More precisely, a virtual photon, say, is an internal photon line in one of the Feynman diagrams.
But there is nothing real associated with it.

Detectable photons are always real, 'dressed' photons.
Virtual particles and the Feynman diagrams they appear in, are just a visual tool of keeping track of the different terms in a formal expansion of scattering amplitudes into multi-dimensional integrals involving multiple propagators - the momenta of the virtual particles represent the integration variables. They have no meaning at all outside these integrals. They get out of mathematical existence once one changes the formula for computing a scattering amplitude. "

As they are to fast to 'notice' except by their 'interactions' they are allowed 'magical' properties.
Like faster than light (as they might have an 'imaginary mass').
« Last Edit: 03/12/2008 11:03:54 by yor_on »
 

Offline labview1958

  • Sr. Member
  • ****
  • Posts: 104
    • View Profile
What Are Virtual Particles?
« Reply #9 on: 04/12/2008 14:34:48 »
My hunch is there are no electrons, protons etc. These particles only exists outside an atom. Inside atoms there is only space bundle together. Thus space converts into mass and energy outside an atom.
 

The Naked Scientists Forum

What Are Virtual Particles?
« Reply #9 on: 04/12/2008 14:34:48 »

 

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