# Can energy be converted back into mass

1. Oct 28, 2009

I have done some studying on the membrane theory or string theory. I understand why energy can have no mass, because energy is vibrations different from vibrations that define mass relative to us. The vibrations are on membranes that flow through 11 dimensions. However, it occurred to me that the probability value of vibrations, that define energy, coming together to form exact vibrations that we see as mass, is quite large. For energy vibrations to come together randomly in 10 dimensions with time to form a vibration on the string or membrane that defines mass to us seems very unlikely. Therefore, I am wondering if energy (light) has ever been converted back into mass. I see an easy explanation for mass being converted into zero mass energy, but I don't see a way to convert energy back into mass using the string theory to explain the universe. However, I do see an explanation for converting energy back into mass with an understanding of the vibrations that make mass. However, I don't think anyone is this far since the string theory is still theoretical. Anyway, I would really appreciate if someone could help me with the question. Can energy be converted back into mass? I know mass is a from of energy... If there are any experiments done with this, that would be very helpful if you could direct me... Thank-you so much.

2. Oct 28, 2009

I should add that I realize the rest mass becomes relativistic mass (which has zero mass). Can the relativistic mass become rest mass?

3. Oct 28, 2009

### MaxwellsDemon

On the contrary...energy has mass/inertia. The awesome, and seemingly counter intuitive, discovery in special relativity is that a hot cup of coffee weighs more than a cold cup of coffee.... its more difficult to increase the speed of a car thats already in motion than it is one at rest with respect to you. It just takes a LOT of energy to increase the mass of something by a little tiny bit...so you'll have to heat that cup of coffee on the stove to unbelievably high temperatures if you want the scale to go up by a gram.

4. Oct 30, 2009

### A/4

This is basically how a particle accelerator works (e.g. how the LHC will produce 100+ GeV particles out of the collision of two 1 GeV particles).

5. Oct 30, 2009

### Bob S

First, let's consider only stable (infinite lifetime) mass that does not decay. So we are limited to protons and electrons. But barion conservation and lepton conservation (with charge conservation) require that to create one of these, their antiparticles must also be created. Fermilab and CERN both create antiprotons, and Fermilab often has ~1012 circulating in its rings. So energy has been converted into barion mass + anti-barion mass. This extra mass (~1.877 GeV/c2) will exist until the antiprotons are used up or dumped into a beamstop.
Bob S

6. Oct 30, 2009

### LitleBang

IN 1999 an experiment was performed at the Stanford linear accelerator where a beam with a frequency of 10^25 Hertz was collided with the green laser of 10^14 Hertz and produced an electron and a positron.

7. Oct 30, 2009

### Bob S

That electron is probsbly still around somewhere, but how long did the positron last?
Bob S

8. Oct 30, 2009

### LitleBang

No it's not, the positron and electron annihilated each other right after their creation as gamma radiation.

Max could you point out where I could read up on this discovery you refer to?

9. Oct 31, 2009

### Bob S

Only virtual pairs annililate right after production. For real pairs like your example of photoproduction (pair production) off an electron using a gamma-boosted laser, the positrons can be separated out. SLAC has created a 1 milliamp beam of positrons using conventional pair production on high-Z atoms.
Bob S

10. Oct 31, 2009

### LitleBang

A virtual particle is something no one has ever seen. It is a theoretical particle. No matter how a particle and it's anti-particle are created, if left alone they will annihilate.

11. Nov 1, 2009

### atyy

Photosynthesis

12. Nov 1, 2009

### MaxwellsDemon

Photosynthesis wouldn't count as an energy to mass process. In photosynthesis the plant is using energy from the sun to grab matter from the environment and incorporate it into its structure via chemical reactions. There is VERY little energy to mass translation in chemical reactions...this is why chemists talk about conservation of matter/mass as a useful principle in their field. Nuclear reactions are where the action is.

13. Nov 1, 2009

### atyy

But it is greater than zero.

14. Nov 1, 2009

### Naty1

The above seems way off base, and unrelated to the rest of your post, so maybe I'm not interpreting what you mean correctly. Membranes are commonly two dimensional strings, right? like a plane. But they can also come in other dimensional sizes. And vibrating strings do have energy and hence momentum, like electromagnetic waves. String vibrations (energy) in general don't flow thru 11 dimensions; apparently only gravity can leak into the additional space dimensions; the other forces are generally constrained to our familair three space dimensions(ath least in the string theories I've looked at). Sorry, I have no idea what your last sentence means.

15. Nov 1, 2009

### arivero

Keep looking to the equation
$$m^2= E^2 - p^2$$
and redo your question based on it, so people will understand more clearly.

16. Nov 1, 2009

### Finbar

I don't think so. In photosynthesis the photon is absorbed it doesn't produce any electrons or positrons it only excites an electron in one of the molecules. So no energy to mass translation is needed for photosynthesis to occur.

17. Nov 1, 2009

### MaxwellsDemon

Exactly, the point I was attempting to get across to the other poster is that the plant doesn't grow by creating mass from the process of photosynthesis. It uses the light energy to pull in mass from the environment via chemical reactions. Imagine a plant isolated in a box with a certain amount of atmosphere, soil, and water sitting on a scale. If you weigh the system when the plant is young and again thirty years later when it is grown, the scale will still read the same weight. Conservation of mass is a principle chemists can rely on because any change in the overall energy of the systems they consider will be tiny. This is because the energy differences are tiny in comparison with the overall mass of the system and a tiny bit of energy has a VERY VERY tiny bit of inertia associated with it because of the c squared in Einstein's relation. Assume for a minute that the isolated system of our plant gets approximately 1500 W/square meter from the sun. Furthermore, assume that all this energy is completely absorbed by the plant/box with none lost due to thermal interactions/reflection/etc. If the box is 10 meters on a side then the total mass change as predicted by Einstein's relation of our ideal plant in a box over thirty years is: (10x10x1500x60x60x24x365x30)/(300000000x300000000) = approximately 2 grams....not negligable, but it is a completely unrealistic situation...and that change in mass is due not to the process of photosynthesis, but the total absorbtion of incoming solar energy over a period of thirty years... I wonder what the temperature and pressure inside that box would be like. Anyone care to calculate? Assume that the box was at 25 C and 1 atm of pressure to begin with. Up for the task? How long would our ideal plant survive? :D