# E=mc^2 verified - again!

1. Dec 29, 2005

### ZapperZ

Staff Emeritus
2. Dec 29, 2005

### marlon

Actually, i don't quite get how the experiment tested E=mc². I am not at work this week so i cannot consult the Nature article, which i will be certainly doing next week.

Here is what i got out of the link:

When a neutron is captured by an atom, the total mass of the atom with one extra neutron is

$$m_{total} = m_{atom} + m_{neutron} - \frac{E_{binding}}{c^2}$$

From experiment (with the magnetic traps, measuring the revolutions about the B field lines) they acquired the total mass (silicon ion with neutron) and the mass of a Silicon ion.

The $$E_{binding}$$ consists out of emitted gamma rays and a recoil energy of the nucleus. This is all straighforeward. They measured the gamma ray energy.

So from experiment we have both the gamma energy, the ionic mass and the mass of the ion WITH the neutron. In order to verify if E=mc², we need to have the $$E_{binding}$$, right ? Well, the one thing they are missing is the nuclear recoil. How did they deal with that ? Probably it was much smaller than their error margin ?

regards
marlon

Last edited: Dec 29, 2005
3. Dec 30, 2005

### marlon

Am i the only guy that does not get the point of this article ?

marlon

4. Dec 30, 2005

### tribdog

the first experiment needed to know the recoil energy, I thought the second one didn't. I know nothing about this, and this is just a layman's guess.

5. Dec 31, 2005

### marlon

Well, i am thinking nearly the same thing. It must be that the recoil energy is smaller than the actual accuracy level (smaller spread in error) of the outcome of the experiment. Somehow, they must have proven that. If so, you do not need to know the actual value for this recoil energy.

Since nobody else is answering this, it seems i will have to wait until i obtain the Nature article on monday. This is very interesting though

regards
marlon

6. Dec 31, 2005

### LeonhardEuler

If the nuetron causes the nucleus to recoil wouldn't that heat the sample? Then, by knowiing the heat capacity, couldn't you measure the temperature to find out how much energy went into this process?