If E=MC2, then how is energy converted into mass?

Question

Say someone has X amount of energy he/she wants to convert into mass, say, a group of atoms. How does one go about this conversion? Does simply compressing the energy do the job? Is mass simply more localized and compressed energy? i.e., "energy with structure"?

Also, since light is supposed to be massless yet contains energy, how can one change photons of light into energy?

Answer 1

You are correct when you say that mass in another form of energy and that energy is another form of mass. In other words, mass and energy are two sides of the same coin.

This also means that whatever you can say about energy you must also be able to say about mass. Now, one of the fundamental properties of mass is inertia. Does this mean that energy has inertia too? Yes! Whatever you can say about mass you must be able to say about energy.

It is possible, as you indicate in your question, to convert mass into energy. This happens all the time in the sun. In fact the source of the energy of the sun is the conversion of mass into energy. This happens then the intense gravity of the sun squeezes two protons together to make a helium nucleus. Some of the mass of the protons is converted into energy. But, only some of the mass.

The only way to convert 100% of mass to energy, so far as we know today, is to collide a particle with an anti-particle, like an electron with a positron.

Mass is also converted into energy when you strike a match. Some of the energy as light and heat given off by the match comes from a tiny, tiny bit of mass being converted into energy. “Tiny, tiny” is on the order of 10^-14kg of mass. This is really tiny.

You also indicate in your question that energy can also be turned into mass. This can be done but it is a lot harder! Just as a little bit of mass makes a LOT of energy, it takes a LOT of energy to get only a tiny bit of mass. But there are particle accelerators that can do this. Google “Triumf” for more on this.

Mass is also created in nature, well, in outer space, when high-energy gamma rays strike the heavy nucleus of an atom. Some of the kinetic energy created in converted into an electron-positron (conservation of electric charge here!) pair.

One more thing about this question. A lot of people think that the c^2 in the equation means the ‘speed’ of light squared. While it is true that ‘c’ is the speed of light, the speed of light squared is a meaningless quantity if it is expressed as m^2 / s^2.

Rather, the term ‘c^2’ should be written as J / kg (Joules, the unit of energy, per kilogram, the unit for mass). The reason why this is important is because the equation written a c^2 = E / m tells you that the energy to mass ratio for all energy and for all mass is 9.0x10^16 J/kg. Every kilogram of mass contains 90,000,000,000,000,000J of energy!

Finally, your question about light energy being converted into mass was addressed above where I mentioned the high-energy gamma rays converting energy into mass. The point is that photons of visible light do not have nearly enough energy to convert to mass. Only gamma ray photons have the required energy to make matter.

Answer 2

Converting Mass To Energy

Answer 3

Well, you have to be a bit more careful. First of all, the complete formula is
E^2=m^2 c^4 +p^2 c^2
where E is the energy of a particle, m is the rest mass, p is the momentum, and c is the speed of light. For an object that is at rest, p=0 and you get E=mc^2. But for photons, m=0 so E=pc is the correct formula. Both formulas are used in conjection with conservation laws to determine what happens in various reactions.

No. It not simply a matter of compressing 'energy' to get mass It strongly depends on what form the energy takes: is it kinetic energy, potential energy, etc. Is it in the form of photons or some other particle (probably a boson)?

As an example, if you take two protons which are moving very fast (almost the speed of light) towards each other, they have a large amount of kinetic energy. If they collide, some of that kinetic energy gets converted into a variety of particles, including possibly more protons. Exactly what reaction takes place depends on a large number of factors and cannot be exactly predicted. We do not know of any way to consistently transform energy into matter in a non-chaotic way.

As another example, if a high energy photon goes past a nucleus, it can convert into an electron and a positron (an anti-electron). But the photon itself has to have enough energy (via E=pc) to make both the electron and the positron.

Answer 4

Energy To Mass

Answer 5

Well, that is the $1 billion question. If anyone knew how to convert mass to energy easily, that would make that person famously rich.
So far, we know how to convert a small proportion of mass in uranium in energy; and it either requires a very costly nuclear reactor, or a bomb that will flatten everything for kilometers around.
We also know how to convert some mass of hydrogen to heavier nucleus (the helium 4 nucleus is not exactly 4 times as heavy as that of protium AKA hydrogen 1; the mass lost is energy). The sun and all the stars do it every day, but so far, we've only been able to do it in hydrogen bomb, and in experimental fusion reactors that do not yet produce enough power to be able to sustain their reaction, let alone be producing commercial level of energy.

Light is massless when the photons are at rest. Since anything traveling at the speed of light is supposed to get an infinite amount of mass as a result, you have the photon getting a mass that can be interpreted as zero times infinity, which can be anything. It turns out light has energy which is a function of the frequency of the photon.
Since photons IS pure energy, there is no conversion required.

Answer 6

Yes and converting energy into mass happens all the time, everyday, to you and to me and to everyone. Having more mass does not necessarily imply creating new atomic constituents (protons, neutrons, electrons). Existing matter can have more mass by simply accelerating it. When you get in your car and drive off down the road, you, your car and everything in it is slightly more massive than it was while you were sitting still. The effect is small until you get to relativistic speeds (approaching the speed of light) at that point masses increase rapidly toward infinite mass, but the energy imparted by your car's engine does produce a very small increase in mass.

Heating your frying pan and food makes it more massive, anything that increases applies energy to matter increases its mass.

On the other hand it takes a tremendous amount of energy to produce enough mass to make an electron, neutron or a proton. You need X-ray or gamma photons or very high energy collisions of matter traveling at close to the speed of light to do this. Still, it happens in high energy physics (colliders, X-ray lasers) and in celestial bodies where these types of energies are typically found.

Answer 7

This Site Might Help You.

RE:
If E=MC2, then how is energy converted into mass?
Say someone has X amount of energy he/she wants to convert into mass, say, a group of atoms. How does one go about this conversion? Does simply compressing the energy do the job? Is mass simply more localized and compressed energy? i.e., "energy with structure"?

Also, since light is...

Answer 8

100% conversion is currently not possible. No one knows how to do that.

An example of energy being converted to mass is this - a compressed spring weighs more than the natural one. Though that change in mass is extremely minuscule.

Answer 9

IF ANYONE KNEW THE ANSWER TO THAT QUESTION..... THEY WOULD BE REVERED AS GODS!!! (because it is impossible as the so-called "perpetual motion machine")

No, really! If you're talking about a 100% efficient way to convert between matter and energy... no one knows.....

Fossil fuels, nuclear fission, fusion reactions, chemical compounds, solar panels, wind power, hydro power, geothermal energy,...(the list goes on)

No know method in todays' world can convert mass purely and directly into useable energy, which is the reason for the world's energy crisis. (and a sense of impending doom)

What is a 100% efficient conversion? Say you wanted to put a couple of logs on the fire to keep you warm for a while. The logs make the fire plenty hot - too hot to touch of course, but; the wood is only converting about 20% of its mass into energy (heat)! The other 80% comes from the smoke produced by the wood, the ashes left over and the light from the fire as it is burning. If the wood allowed every bit of its mass to be turned into energy, no ashes leftover, no visible light and no smoke, etc.,
a single log would produce so much heat (in the form of radiation) that it would likely melt right through the cast iron grate - and the concrete beneath that until it eventually burned out...

http://en.wikipedia.org/wiki/E%3Dmc2

To understand WHY you can't convert mass directly into energy and vise versa - you'll need to learn more about atoms - chemical bonds, polarity and the strong and weak nuclear forces - among other things.

And about light - It is thought to be massless, BUT, it doesn't follow the rule for a massless particle - it IS affected by gravity (black holes for example) and light is supposed to be massless because nothing can travel faster than light itself. EVEN THEN, the speed of light can be manipulated - slowed and even stopped - so where do we stand?!
http://www.eurekalert.org/pub_releases/2005-08/epfd-ltt081905.php

Answer 10

As far as I know there's no known way to convert energy back into mass, although as E=mc^2 suggests, it's theoretically possible.

Light is a form of energy.