E = MC2: PART 2: Converting Mass to Energy / Energy to Mass

Continued from Part 1 ....

It’s easy to get examples of mass being converted to energy. When you burn coal into ash, you are using up the binding force (which holds the ‘molecules’ of that substance together) to get energy. You are releasing the energy that is holding up atoms and molecules together. Molecules break down and atoms recombine to form new molecules of resulting byproducts. Weight of byproducts after burning process is lesser than that of original coal. This is nothing but mass converted to energy. The amount however is extremely minute with respect to original mass of coal. On the other hand when you trigger nuclear fission you are basically breaking down the atom (nucleus) of an element and converting some atomic (nuclear) mass into energy. The mass of the nucleus before fission is slightly more than the sum of the masses of the separated elements of the nucleus. The difference is what got converted to energy. In other words, this energy is dormantly trapped inside the nucleus, and as long as it stays trapped, it shows up as that 'differencial' mass.

Nuclear reactors and nuclear bombs work on this principal of 'nuclear fission'. However, for the same original mass, the percentage of mass converted to energy is much higher in case of nuclear fission than conventional ways like burning fuels. Hence fission process has much higher yields. The process of fusion is also associated with mass-to-energy conversion. When you fuse two atoms (protons) of hydrogen to form helium, the united protons together weigh less than the sum of individual protons. The difference is converted to energy. 'Hydrogen' (or thermo-nuclear) bomb works on the same principle and so does the Sun of our solar system.

But it’s hard to imagine processes where pure energy gets converted into mass or matter. What is Matter? Matter in its simplest form means - protons, neutrons (and electrons because they also have mass, although minuscule). Protons and neutrons form the nucleus and electrons are moving around the nucleus. These three act as building blocks in making up atoms, which in turn make up molecules that make up different elements and compounds. If you pull out a proton (or a neutron or an electron) from a nitrogen atom and replace it with a proton (or a neutron or an electron) from an oxygen atom or any other element’s atom - Nitrogen would still remain Nitrogen. Hence matter boils down to protons, neutrons and electrons.

When the big bang happened approximately 13.7 billion years ago, all you had was energy (thermal and electromagnetic. Remember, light is electromagnetic radiation). That energy spread over and in bits and pieces, started getting converted into 'Matter' or 'Mass'. First Hydrogen was formed since it is the easiest one to be created when it comes to creating matter from scratch. Why easiest? Construct a nucleus with only one proton and you have Hydrogen atom. (That’s also the reason why Hydrogen is most abundant in universe). Then gradually other elements were created and chunks of these elements started grouping together to form different compounds and celestial bodies mainly stars and planets. So there you go - energy got converted to matter.

But where did that initial energy that triggered the big bang come from? The accepted answer is 'God'. But assuming that God also is made up of matter, how did he get created? I don’t know :)

I don’t think human quest would reach that far. But the Particle Accelerator experiment at CERN, is attempting to get closer to the time just after the big-bang. It aims to create a miniature big bang which will lead to creation of 'matter’ from scratch. But wait a minute. How would you create the big-bang without having enough energy to cause that big bang in first place ? Of course, you can’t create energy but can covert it from some matter, cant you? The CERN equipment will try to do exactly that. It will try to energize protons (which is matter in its simplest form) to travel at speeds close to that of light. These protons would then have enourmously high amount of energy. These high energy protons would be banged into each other to create a mini big-bang. So here, matter (protons) is being converted into energy (big bang) and that energy is expected to be converted back into new matter (or ‘mass’).

But one important thing is that big-bang will produce two types of matter - 'normal' matter as well as 'anti-matter'. Normal matter is positively charged. Antimatter as a matter of fact, is still ‘matter’ and has the same 'mass' as its corresponding matter, but has 'negative' electric charge. Yes, it is matter with mass that has ‘negative electric charge’. (Note - its ‘negatively charged’ and not 'negative' mass, which supposedly does exists. But its a totally different theory and no need to worry about it here). How can that be? Does mass have a charge? Yes. It does and we don’t usually have to worry about it, because the positive charge of the mass will be detectable only if there is a negatively charged mass in its vicinity and we don’t have any negatively charged matter around us. An electron (with negative charge of 1 electron-volt) will not let us know that it has a negative ‘electric’ charge unless we let a positive charge venture into its vicinity. And what happens when positive and negative ‘electric’ charges combine? ‘Nothing’ - may be a spark. The charges neutralize.

So what would happen when matter and anti-matter come together? No, not ‘nothing’ this time. Remember, we are dealing with masses (positive scalar quantities) with 'opposite' charges. The charges will neutralize but mass quantities will add up and annihilate to create ‘Pure Energy’. Union of matter and anti-matter will create energy with 100 percent efficiency (meaning 100 percent of matter gets converted to energy)

Thinking of the reverse process, we know that matter got created during big-bang 13.7 billion years ago. But does it also mean that equivalent amount of anti-matter was also got created under the rules of E=MC²?. That’s what scientists at CERN are assuming. A section of the scientific community has always believed that antimatter was also created with matter when big-bang happed. They conclude that anti-matter is somewhere out there far away in the universe, dormant like a sleeping dog but when you get closer to it, it would growl and pounce on you to cause total annihilation and creation of 'pure' energy. The other section of scientists disapprove this theory (of equivalent amount of anti-matter being present somewhere in the universe)

So you get the idea - how mass and energy are inter-convertible and how they are two different forms of the same thing? Einstein proposed this theory in 1905, but rest of the world took decades to grasp this revolutionary concept.

If you come so far, I believe you will be interested in knowing more about what has ‘Speed of Light’ got to do with this Energy and Mass conversion? If you are, please visit the following link:

Part 3: How is 'Speed of light' involved in the conversion ?

Authored by: Mandar Garge