# Spin and orbit velocity of electron slows down approaching c ?

1. Jan 5, 2012

### Professorv

Spin and orbit velocity of electron slows down approaching "c"?

If happen a atom to get very close the velocity "c" the time will almost
stop.
What will happen to the velocity of the orbit and spin of a electron? It
will slow down too?

2. Jan 5, 2012

### jetwaterluffy

Re: Spin and orbit velocity of electron slows down approaching "c"?

The velocity of the orbit will slow down, but the spin might not, as spin is a quantum property and is not literally the electron spinning.

3. Jan 5, 2012

### rorix_bw

Re: Spin and orbit velocity of electron slows down approaching "c"?

Will it keep the electron?

Last edited: Jan 5, 2012
4. Jan 5, 2012

### maverick_starstrider

Re: Spin and orbit velocity of electron slows down approaching "c"?

It all depends on who's asking, it is relativity after all. From the electron's reference frame everything is peachy. Objects being Lorentz contracted to one observer don't like "feel" lorentz contracted in their own frame. If you're going 0.5c and you double your kinetic energy you THINK you're going 1c but other observers won't agree with you. The electron doesn't know the different, however, from the lab frame the energy levels get shifted, this is the kind of thing which is exploited in laser cooling (doppler cooling

5. Jan 5, 2012

### jetwaterluffy

Re: Spin and orbit velocity of electron slows down approaching "c"?

Yes, why wouldn't it?

6. Jan 5, 2012

### maverick_starstrider

Re: Spin and orbit velocity of electron slows down approaching "c"?

Just to further clarify, if you have a spaceship with a gas pedal and you put the pedal to the metal and keep it there. You constantly accelerate, it's not like you keep accelerating until you hit "c" and then wham brick wall. You are completely oblivious to anything funny going on, you will feel a constant force consistent with your acceleration and it'd only be when you looked out the window at something like a passing planet or spaceship that you'd realize something funny was happening.

By way of example you might look into atmospheric muons, these were some of the first tests of relativity. If a muon is at rest it decays pretty reliable in a pretty short time, however, muons created in the atmosphere were making it much further into the earth's surface then they should have before decaying based on their lifetimes. But it you take relativity into account you see that their lifetimes are extended by their speed. In their frame they have the same old decay time, in our frame it gets extended much like the twins paradox.

Also, it's not strictly meaningful to talk about the "velocity" of electrons in an orbital. Electron orbitals have no time-dependence, it's a stationary state. They do have momentum though, ah quantum mechanics

7. Jan 5, 2012

### Drakkith

Staff Emeritus
Re: Spin and orbit velocity of electron slows down approaching "c"?

Neither the spin nor the electron in it's orbital has anything like what you would normally think of as "velocity". Quantum spin is NOT the particle actually rotating, it is simply a property of the particle, similar to how charge is just a property. Similarly, electrons occupy an "orbital" and aren't actually orbiting the nucleus like a planet orbits a star. For more info you would need to read up on quantum mechanics.

8. Jan 5, 2012

9. Jan 5, 2012

### Drakkith

Staff Emeritus
Re: Spin and orbit velocity of electron slows down approaching "c"?

From the article:

As it says, this experiment demostrates that the spin of electrons is quantized. It can ONLY be one of two values. This is because spin is a property of the electron, not a result of it actually spinning on it's axis.

10. Jan 5, 2012

### maverick_starstrider

Re: Spin and orbit velocity of electron slows down approaching "c"?

I don't understand why this suggests that spin is outward angular momentum to you. If anything this would suggest that you get a range of values when passing through an SG apparatus instead of just two discrete branches.

11. Jan 6, 2012

### Drakkith

Staff Emeritus
But you don't get a range of values, you only get two. Or did I misunderstand your post?

12. Jan 6, 2012

### maverick_starstrider

Re: Spin and orbit velocity of electron slows down approaching "c"?

Yes, you get two, but if your intuition was that spin was simply angular momentum (i.e. the orbital angular momentum) you'd expect a spectrum (if angular momentum is classical) or at least a range (potentially infinite) of discrete values.

13. Jan 6, 2012

### rorix_bw

Re: Spin and orbit velocity of electron slows down approaching "c"?

Mistake on my part. I was thinking: if the electron slowed significantly then its orbit would be affected, but I now I realise how stupid I am.

14. Jan 6, 2012

### Drakkith

Staff Emeritus
Re: Spin and orbit velocity of electron slows down approaching "c"?

Of course, which is what the experiment demonstrates, that our intuition is wrong.

15. Jan 11, 2012

### vlassius

Re: Spin and orbit velocity of electron slows down approaching "c"?

Hi, interesting question. I think that the electron will get still if the atom get c.
This has nothing to do with velocity but time.
I think when approaches the c velocity, the velocity in orbit will be the same, just the time will be dilated so, the orbit would not be affected. If we take from another frame of reference (not the atom itself) moving in a low velocity comparing with c, the electron would still running normally in orbit.
But i think that it will really get still when the atom gets the c velocity, really stopped still in orbit like a snapshot.
This gets more interesting if we think that it is related with the conduction of electricity. The electron needs to change from atom to atom to get a current. If the electron is still in orbit, the material that has this atoms, could not be conduct electricity.
We are talking about transistors, or semi-conductors, metals, etc... If it gets c velocity, the materials that we knows would stop to conduct electricity

16. Jan 11, 2012

### Rob D

Re: Spin and orbit velocity of electron slows down approaching "c"?

Please correct me if I am wrong but since "spin" is a quantum characteristic and in actual fact the electron, particularly when it is captured in an atom, exhibits its wave function and cannot spin like an object. Therefore, would not the electron, and the atom for that matter, be c impervious? Unless the energy surge of the singularity itself splits the atom, our electron or electrons will continue to do their job of surrounding the nucleus with a nice layered skin of charges. Since the quantum state of the electron on a atom does not make it behave as a particle, why would a charged wave react to the changes in space-time approaching c? As far as I know, there is no spin to change.

We've already stated that the angular momentum is merely a quantum value needed to make the theory work. Why then would the electron react to changes in either time or space unless they are accompanied by sufficient energy to fundamental change the atom the electron is paired with?

Or am I wrong,
Rob

17. Jan 11, 2012

### Drakkith

Staff Emeritus
Re: Spin and orbit velocity of electron slows down approaching "c"?

No atom can ever reach c, nor does the electron work the way you are thinking.

As above, it would never reach c.

Spin is needed to make the theory work just as much as every other property of anything is needed to make any theory work. Everything reacts to changes in spacetime, even atoms and subatomic particles. Muons created from cosmic rays have a very short lifetime and would not be able to be detected here on Earth if it wasn't for the fact that they exhibit time dilation and live long enough in our frame to be detected.

18. Jan 12, 2012

### vlassius

Re: Spin and orbit velocity of electron slows down approaching "c"?

19. Jan 12, 2012

### Drakkith

Staff Emeritus
Re: Spin and orbit velocity of electron slows down approaching "c"?

You can, but it's pointless since it isn't possible. You'd have no way to know if it was correct or not.

Electrons are not little balls orbiting the nucleus like a planet orbits a star. The details would require an understanding of Quantum Mechanics, so I recommend picking up a book on it instead.

20. Jan 12, 2012

### vlassius

Re: Spin and orbit velocity of electron slows down approaching "c"?

The physics of today seems a "Frankstein" to me.
Relativity theory gave us really very important informations but it stops before get c velocity.
We have math problems, we really can not know a lot of things.
We can not even calculate the time component when v=c. The equations that we have do not go there.
I hope see something happening in my lifetime, something to turn this "Frankstein" in a beautiful lady.
Besides, we have a very interesting particle that is at c velocity and we know almost nothing about it too (photon).
What is or is not possible, generally only depends of our knowledge (as human race)