The Speed of Light, is it a relative thing?

[Delasaurus]

58 minutes ago, Spikey said:

This is an interesting thread and hopefully if we can keep it away from any further mention of politics and/or religion it will continue to be. A couple of posts over the last 24 hours or so are pushing it, so please if you are unfamiliar with the code of conduct  then it might be a good time to read it. No politics and no religion no matter how tenuous the link. Thanks

 

That's a great shame, because both have played a huge importance to the development of Science and Physics, however, your rules and since I suspect those rules have been directed in my direction, I will abide

[Alien 13]

Is the speed of light still constricted if its travelling in nothingness for example the free space in an atom or something similar..

Alan

[saac]

Alan I think it was James Clerk Maxwell who is credited with determining the speed limit of electromagnetic waves.  Maxwell determined that two properties of free space (vacuum) ,  permittivity or electric constant (Eo)   and the permeability or magnetic constant  (Uo) are responsible for limiting the propagation of  EM waves.  The relationship set by Maxwell is surprisingly simple where:

c = 1/ (Eo Uo)^1/2

As far as I understand, the space within an atom is no different from free space so I suspect the values of Eo and Uo are the same resulting in the familiar speed limit.  Not sure if the presence of the electric field from the electron/proton has an influence - maybe somebody could comment.

The wiki article is a good read on this, you'll find the respective values for the two constants. Scroll down to Propagation of Light  Speed of Light - Wikipedia

Edited - in other mediums the speed of light is of course different (slower). The oft quoted 300,000,000 m/s refers to the speed of light in a vacuum (free space).

Jim 

[saac]

Just to add a little bit on the above. Although not technically correct I use this analogy when thinking about the role of Eo and Uo with respect to the speed of light. Light together with all EM waves can be thought of as a ripple or disturbance in the electrical and magnetic field that permeates space.  Just like the viscosity of say a liquid would influence the speed of say your hand pushing through it, so the Eo and Uo limit how the magnetic and electric fields can change in space.  It's not entirely accurate but it gives me a familiar engineering analogy to hang my hat on  

Jim

[Delasaurus]

1 hour ago, saac said:

Light together with all EM waves can be thought of as a ripple or disturbance in the electrical and magnetic field that permeates space.  Just like the viscosity of say a liquid would influence the speed of say your hand pushing through it,   

Jim

Is that not the Higgs-Bosun analogy?

Whereby it smooths the way for particles to move through the atomic sludge?

[saac]

8 hours ago, Delasaurus said:

Is that not the Higgs-Bosun analogy?

Whereby it smooths the way for particles to move through the atomic sludge?

The popular analogy on the Higgs field is explained quite well here.  I would just say again that my analogy on the role of the Eo and Uo constants on the speed of light does not hold up to scrutiny so don't read too much into it. The science minister won't be sending me a bottle of champagne.

Jim

 

Higgs Field Analogy

[SilverAstro]

12 hours ago, Alien 13 said:

Is the speed of light still constricted if its travelling in nothingness for example the free space in an atom or something similar..

There is no 'nothingness'.
There is no 'free space' inside an atom.
The atom is full of electron fuzzyness (aka atomic orbitals ), if you subscribe to the quantum mechanical model which so perplexed Niels Bohr and needed Mr E. Schrödinger and his famous equation to sort out.
That is why the EM slows down as it encounters atoms, it gives up energy as it interacts with the electron clouds.
Photons and electrons are not point-like objects.

 

[Delasaurus]

39 minutes ago, SilverAstro said:

There is no 'nothingness'.
There is no 'free space' inside an atom.
The atom is full of electron fuzzyness (aka atomic orbitals ), if you subscribe to the quantum mechanical model which so perplexed Niels Bohr and needed Mr E. Schrödinger and his famous equation to sort out.
That is why the EM slows down as it encounters atoms, it gives up energy as it interacts with the electron clouds.
Photons and electrons are not point-like objects.

 

That was my understanding of it too. It (the electron) creates an electromagnetic field as it whizzes around the nucleus at various energy level states. There is no vacuum inside the atom as you say. If you excite the atom by putting more energy into it, the electron will vibrate at a higher level into the next energy level until eventually it flies out of the bond with the nucleus and hence emits a partical which could be a light photon, an x-ray, or a gamma ray say.

In the atomic bomb, for example, we use an unstable isotope because it requires much less energy to destabilise the atom and hence release the electron from its already high energy level shell. I believe a shotgun cartridge was used to detonate the first atomic tests, so that shows what little energy is required to destabilise Plutonium.

 

 

 

[Macavity]

I think one has to be "a bit careful" re. size of things? 

There are things like a "Classical radius of an Electron".
But it is just that... "Classical"? There is also smearing
of the quantum mechanical wave functions in atoms.
The polarisability of the vacuum where an electron is
surrounded by a cloud of virtual e+/e- pairs etc. etc.

There is a characteristic length (cross section etc.) for
the "electromagnetic interaction" at High Energies. But
electrons (and photons) are held to be "structureless"
down to the smallest measurable dimensions AFAIK?   

But the above might contain any number of incorrect
statements... Plus I forget so much stuff these days! 

[andrew s]

13 minutes ago, Delasaurus said:

That was my understanding of it too. It (the electron) creates an electromagnetic field as it whizzes around the nucleus at various energy level states.

It was the fact that a electron did not radiate em and hence decay into the nucleus as it would do classically that led Bohr to his first quantum theory of the atom. 

Somewhat perversely for the lowest energy 1s orbital the most probable place for the electron to be is the center of the atom! 

In modern terminology the vacuum is the lowest energy state of the quantum fields and thus it contains no particles which are excitation in the quantum fields. 

Regards Andrew

[Delasaurus]

8 minutes ago, Macavity said:

I think one has to be "a bit careful" re. size of things? 

There are things like a "Classical radius of an Electron".
But it is just that... "Classical"? There is also smearing
of the quantum mechanical wave functions in atoms.
The polarisability of the vacuum where an electron is
surrounded by a cloud of virtual e+/e- pairs etc. etc.

There is a characteristic length (cross section etc.) for
the "electromagnetic interaction" at High Energies. But
electrons (and photons) are held to be "structureless"
down to the smallest measurable dimensions AFAIK?   

But the above might contain any number of incorrect
statements... Plus I forget so much stuff these days! 

That's the frustration of age isn't it? It's all in there somewhere, if only we could recall it. Hence senile old git syndrome which I think has probably overtaken common sense, certainly in me at times

Maybe we should have a code of WARNING to others that GREYS really do exist here on Earth. Because not only is Physics sometimes hard to grasp at the best of times, but I pity those new comers trying to grasp the concepts of contributors such as myself at times!

 

[Delasaurus]

22 minutes ago, Macavity said:

There is also smearing of the quantum mechanical wave functions in atoms.
 

Could you explain that a bit more for me please.

[andrew s]

2 minutes ago, Delasaurus said:

That's the frustration of age isn't it? It's all in there somewhere, if only we could recall it. Hence senile old git syndrome which I think has probably overtaken common sense, certainly in me at times

Well I shall be 66 on boxing day. I find that the development of the internet has more than compensated for my declining memory. The availability of high quality forums and arXiv.org papers knock my very gray cells into shape. 

Regards Andrew

[andrew s]

1 minute ago, Delasaurus said:

Could you explain that a bit more for me please.

To prove my last point have a look at this https://en.wikipedia.org/wiki/Atomic_orbital

Regards Andrew

[Delasaurus]

2 minutes ago, andrew s said:

Well I shall be 66 on boxing day. I find that the development of the internet has more than compensated for my declining memory. The availability of high quality forums and arXiv.org papers knock my very gray cells into shape. 

Regards Andrew

Yeah know what you mean, I've just ordered the complete set of OU Science from e-Bay as a refresher, because I'm beginning to question if I ever studied and passed any of it having realised that it was nearly 40yrs ago...and merely a figment of my imagination now.

[andrew s]

6 minutes ago, Delasaurus said:

Yeah know what you mean, I've just ordered the complete set of OU Science from e-Bay as a refresher, because I'm beginning to question if I ever studied and passed any of it having realised that it was nearly 40yrs ago...and merely a figment of my imagination now.

The problem is the subject has moved on considerably from when I did my physics degrees. I have spent considerable amounts of my time trying to keep up, more so now I am retired. 

As I have the right background I can often follow review papers and the like even if I can't follow all the mathematics. The advantage of peer reviewed papers is that the referees have done the checking for me.

Regards Andrew

[SilverAstro]

15 minutes ago, Delasaurus said:

Could you explain that a bit more for me please.

13 minutes ago, andrew s said:

To prove my last point have a look at this https://en.wikipedia.org/wiki/Atomic_orbital

And that is why I wrote   "  electron fuzzyness (aka atomic orbitals )"  instead of just "electron fuzzyness", in the hope that those interested would have a hook upon which to google

[SilverAstro]

52 minutes ago, Delasaurus said:

In the atomic bomb, for example, we use an unstable isotope because it requires much less energy to destabilise the atom and hence release the electron from its already high energy level shell. I believe a shotgun cartridge was used to detonate the first atomic tests, so that shows what little energy is required to destabilise Plutonium.

Ho! that requires a whole other thread !

It has a lot more to do with how many neutrons can be released upon 'destabilisation' and how best they can be used. There was only one 'first' atomic test(s), (unless you include those over Japan ) which was a focused charge  implosion of a sub-critical lump of plutonium which then when compressed became dense enough to become critical very quickly. ( Ive left out some small tricky details )

The shotgun cartridge you are thinking of relates to the Uranium weapons where ( in the early ones) two sub-critical bits are shot one at (or into) the other becoming a super critical lump. (Hiroshima) this requires much less effort than the Plutonium type (Nagasaki and the first test at Almagordo)

If you dont put the two bits together very very quickly they just bounce and sit side-by-side fizzling a bit and melting and making a bit of a mess on your table-top. (Twisting (or tweaking) the tail of the dragon)

[SilverAstro]

39 minutes ago, SilverAstro said:

(Twisting (or tweaking) the tail of the dragon)

Oh ! and upon googling that which was a distant (age related!) memory, about the dragon words by Oppenheimer et al I see there is lots of recent "The Bomb" TV and other stuff about it.

I was referring to the original tweaking games they played and one very nasty accident where the pack of cards fell over and (insert forgotten name*, I'll have to do a memory back-up google ) bravely stuck his arm out from behind the shield to nudge the bits apart to prevent it all getting very much worse, sadly he died from the dose not long after

EDIT * (isnt google a wonderful aide memoir) found him :) Louis Slotin  "Pajarito accident"

"When the screwdriver accidentally slipped, the [Beryllium] cups closed completely around the plutonium, sending the assembly supercritical. Slotin quickly disassembled the device"

[Delasaurus]

10 minutes ago, SilverAstro said:

Oh ! and upon googling that which was a distant (age related!) memory, about the dragon words by Oppenheimer et al I see there is lots of recent "The Bomb" TV and other stuff about it.

I was referring to the original tweaking games they played and one very nasty accident where the pack of cards fell over and (insert forgotten name, I'll have to do a memory back-up google ) bravely stuck his arm out from behind the shield to nudge the bits apart to prevent it all getting very much worse, sadly he died from the dose not long after

Have you ever seen the Parthenon type buildings near the East Coast around Woodbridge area? They were designed that in the event of a catastrophe in doing 'experiments of a classfied nature' that the concrete pillars were exploded and a very very large concrete slab fell down to cover the experimental pit.

I would guess that no philosophy about if the 'cat' was dead or not under that slab was pondered about, they just ran for hellfire!

[SilverAstro]

5 minutes ago, Delasaurus said:

they just ran

No not come across that, more googling required !

Found my forgotten unfortunate man, Louis Slotin, have amended previous post. Screwdriver indeed ! one would laugh except it didnt end well  

[Delasaurus]

11 minutes ago, SilverAstro said:

No not come across that, more googling required !

Found my forgotten unfortunate man, Louis Slotin, have amended previous post. Screwdriver indeed ! one would laugh except it didnt end well  

Save your poor fingers my goodman..

(explosive charges surrounded the pillars)

[SilverAstro]

18 minutes ago, Delasaurus said:

Save your poor fingers my goodman..

(explosive charges surrounded the pillars)

Thank you, so kind of you    Eeeek !

Dangerous stuff, but a good peacemaker, two Asian countries have not gone to war after completing their experiments.  Thinks : wasnt the top of the Chernobyl reactor built something like that !!

I think it is time, without further hesitation, deviation etc. we got back to topic

[SilverAstro]

I do like the subtle, understated touch of the Danger sign. Or was someone avin a'larf ?

[Delasaurus]

24 minutes ago, SilverAstro said:

I do like the subtle, understated touch of the Danger sign. Or was someone avin a'larf ?

Ah..nuclear, love it!

I worked for a firm that had a bit of kit returned to it for refurb work from a nuke plant, some time later after the guy had dropped it off from the back of his lorry, the men in white suits and helmets turned up to decontam it!

Been sitting on the factory floor and most likely used as a coffee table for the past couple of weeks...

And so the speed of light does vary Silver, according to how fast you can run to the shower.