Unless light and matter consist of the same fundamental building blocks. During nuclear tests they've found that a tiny amount of matter actually disappears (which may SOUND like it violates the Law of Conservation of Matter), but it's actually believed that that tiny amount of matter was converted into an enormous amount of electromagnetic energy (hence e=mc^2) (i.e. light, for all intents and purposes).
If that's true, then this experiment is probably just reversing the process. The light is converted into a tiny amount of matter that's barely detectable (that 'fingerprint' - possibly just a tiny amount of matter that's slightly different from the matter around it), and can be converted back into energy easily.
Personally, my theory is that once we get down to more and more subatomic particles, we're going to start seeing that it has more and more properties in common with electromagnetic radiation. Electromagnetic radiation itself consists of a magnetic 'part' and an electro 'part', and if you coiled enough of it together millions and millions of times in a certain state, maybe you'd have an atomic particle that contained a phenomenal amount of energy, and a tiny amount of mass.
My physics is a little rusty, so please forgive me if I'm wrong. I think the law you're referring to is the Law of Conservation of Mass. As energy has mass and subatomic particles have mass, you can convert back and forth between them all day (good luck with that), and never violate it. In particular, Einstein's E=mc^2 is applicable here.
It was a surprise to me to find that the term 'matter' is actually poorly defined. At least according to Wikipedia.
Ah yes - I did mean conservation of mass, thank you.
I think most people use 'matter' to refer to the regular objects we interact with that are composed of atoms, and that's how I intended to use it in the above post. However, if I had my way, electromagnetic radiation would also be consider 'matter', because it's the same stuff, just a different form.
>> As energy has mass
Is that generally accepted, btw? Because I've always heard people talk about light as having no mass, and it never made sense, because that what I understood e=mc^2 to represent. I think it does have mass, it's just so minute (smaller than anything we know by such an order of magnitude that the speed of light squared is used to express it) that it doesn't seem like it.
I'm no expert, but my understanding is a little different. Its not that energy "has" mass but that energy and mass are two different forms of the same thing, i.e. they are equivalent. If some process is able to convert mass to energy then you could find out much mass you'd get but multiplying the energy by c^2 (hence E = mc^2).
Mass is simply a form of energy, converted as E=mc^2. Energy is what's conserved. The model breaks down dramatically once you're doing dramatic forms of mass-energy conversion, like with nuclear reactions.
EDIT: I appreciate the correction on my misinformation about other types of reactions, and will not continue to spread that untruth here. Thank you, Locke1689.
"Even simple exothermic chemical reactions convert mass to energy by the same ratio as nuclear reactions."
That's not exactly true. Most exothermic reactions are simply the restructuring of chemical bonds (molecular bonds) to lower energy states. Consider that every molecular bond stores a certain amount of chemical potential energy. By breaking that bond, the potential energy is released in the form of kinetic energy, or heat.
There is no fission or fusion in normal chemical exothermic reactions and no matter is created or destroyed. Instead, the process is more similar to the powering of a motor via electricity -- electric potential energy is converted into kinetic energy through the actions of electromagnetism.
If that's true, then this experiment is probably just reversing the process. The light is converted into a tiny amount of matter that's barely detectable (that 'fingerprint' - possibly just a tiny amount of matter that's slightly different from the matter around it), and can be converted back into energy easily.
Personally, my theory is that once we get down to more and more subatomic particles, we're going to start seeing that it has more and more properties in common with electromagnetic radiation. Electromagnetic radiation itself consists of a magnetic 'part' and an electro 'part', and if you coiled enough of it together millions and millions of times in a certain state, maybe you'd have an atomic particle that contained a phenomenal amount of energy, and a tiny amount of mass.