# Don't the magnetic poles affect radioactive decay?

1. Aug 26, 2015

### Tzimtzum

Also, How do we know the radioactive decay is constant? I know that carbon dating cannot be 100% accurate because the rate of production fluctuates based on cosmic rays hitting our upper atmosphere. Why isn't this true with earth metal isotopes?

Is time truly constant? It seems like a lot of variables could make it fluctuate.

2. Aug 26, 2015

### Bystander

Assuming your post is focused entirely on carbon-14 age dating, you've asked several questions; for starters, all radioactive decay processes other than electron capture have fixed rates.
Does that clear up that first question?
Paraphrasing, you mean to ask, "Is a measured carbon-14 age invariant?"
No.
You have noted that the production rate varies, depending on cosmic rays, shielding by the magnetic poles, and other things.
Wiki isn't too bad a start for some of the mistakes that have been made in applying the technique https://en.wikipedia.org/wiki/Radiocarbon_dating

3. Aug 26, 2015

### Staff: Mentor

We have lots and lots and lots of evidence suggesting that most types of decay are constant and very little/no evidence suggesting otherwise. There are a few elements that can have slight variability in their decay, but these are known and accounted for. More info here: http://math.ucr.edu/home/baez/physics/ParticleAndNuclear/decay_rates.html

It's not 100% accurate because 100% accuracy is impossible. The fact that carbon-14 is produced by cosmic rays is what allows us to do carbon dating in the first place. Fluctuations in the rate of cosmic rays striking the atmosphere probably averages itself out in the long term, which is what matters. The amount of carbon-14 in the atmosphere changes very little on a shot term basis.

Time is relative and can be different for different observers, though each observer sees themselves as passing through time at a rate of one second per second. However there are actually very, very few variables and time doesn't fluctuate the way you're most likely imagining it can. Look into Special and General Relativity for more info.

4. Aug 27, 2015

### Tzimtzum

Oh wow, I was really was tired when I wrote this. I meant to say atomic decay not radioactive decay. Though the fluctuation of radioactive decay is what original made me wonder about this.

https://en.wikipedia.org/wiki/Caesium_standard
"By definition, radiation produced by the transition between the two hyperfine ground states of caesium (in the absence of external influences such as the Earth's magnetic field) has a frequency of exactly 9,192,631,770 Hz."

Does this mean the Caesium standard is influenced by the magnetic field? The poles are shifting more and more each year. I think it's at 40 miles per year now. Would this affect the atomic decay?

5. Aug 27, 2015

### Staff: Mentor

Even using the term "atomic decay" is reminiscent of radioactivity.

The energy levels of all atoms are affected by external magnetic fields. Some levels will shift to higher energies in the presence of the field, other will shift down in energy. Except for very strong magnetic fields (and the Earth's magnetic field is very weak), this shift in energy is minuscule. Nevertheless, when building a very-high-precision atomic clock, tiny shifts can introduce significant errors.

One way to maintain a high precision is built in the standard itself: only one substate of each of these two hyperfine ground states of caesium is considered, $M_F = 0$, because these states are not affected by a magnetic field, to first order. But higher-order terms are still relevant to achieve high precision. So additional measures are taken, such as magnetic shielding or using external magnetic fields to counteract the Earth's magnetic field.

The shift in the Earth's magnetic field is not very important. What is important is the local value of the field where the clock is.