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[Cryxis, Prince of Doom]

Oh I thought you meant the random particles just appeared while testing for different things (I've made the connection of particle accelerators only being used for throwing things together to see what they are made of, probably a bad assumption) and with photosynthesis it's only slightly more and the purpose is the convert water and carbon into sugar using sunlight as a power source.

Ya nevermind, thanks guys for answering

[Il Palazzo]

Less obviously, it occurs in chemical reactions, such as photosynthesis - the mass of the products is very very slightly greater than the reactants ( due to binding energies IIRC) and the energy from sunlight makes up the difference.

Even less obviously it occurs when stretching a spring, or lifting a ball in a gravitational field.

[Putnam]

You can't really create matter if you don't have matter in the first place, though; lepton number and baryon numberare conserved quantities, which means that if you want to make, say, a pair of electrons out of a particularly energetic photon, you'll have to make an electron and a positron instead, which will probably annihilate right back into a photon. It's a tough problem.

Oh I thought you meant the random particles just appeared while testing for different things (I've made the connection of particle accelerators only being used for throwing things together to see what they are made of, probably a bad assumption) and with photosynthesis it's only slightly more and the purpose is the convert water and carbon into sugar using sunlight as a power source.

Ya nevermind, thanks guys for answering

Yeah, we know exactly what those things are made of. Protons are two up quarks and one down quark. Quarks are almost surely elementary, so nothing makes them up (they're one of the most basic building blocks of matter). Electrons are similarly elementary.

Less obviously, it occurs in chemical reactions, such as photosynthesis - the mass of the products is very very slightly greater than the reactants ( due to binding energies IIRC) and the energy from sunlight makes up the difference.

Even less obviously it occurs when stretching a spring, or lifting a ball in a gravitational field.

No, not at all. That's energy. Energy and mass are the same thing, yes, but they're not the same thing if you catch my drift. Mass is a particular form of energy. Gravitational potential energy is not mass. This paragraph gives me a funny feeling in my stomach that tells me that I'm not sure, though.

E=mc² is something of a lie-to-children. The proper equation is E²=(pc)²+(mc²)²

[MonkeyHead]

Oh, another notable example would be "heavier than Iron" element fusion during the death of high mass stars.

[Cryxis, Prince of Doom]

Ya I know what they are made of... That's why I have the connection welded into my head because any time I hear people talk about LHC for example I can only think of throwing things together for that purpose even though particle accelerators have some different use maybe, I really don't know .-.

[Putnam]

Yeah, they have different uses. Hell, we made a couple new baryons there within the last few months, made of one down, one strange and one bottom quark.

[Il Palazzo]

Less obviously, it occurs in chemical reactions, such as photosynthesis - the mass of the products is very very slightly greater than the reactants ( due to binding energies IIRC) and the energy from sunlight makes up the difference.

Even less obviously it occurs when stretching a spring, or lifting a ball in a gravitational field.

No, not at all. That's energy. Energy and mass are the same thing, yes, but they're not the same thing if you catch my drift. Mass is a particular form of energy. Gravitational potential energy is not mass. This paragraph gives me a funny feeling in my stomach that tells me that I'm not sure, though.

E=mc² is something of a lie-to-children. The proper equation is E²=(pc)²+(mc²)²

What do you mean? Energy and mass are the same thing in GR. Rest mass is a particular form of energy.
In all cases involving binding energy, be it chemical, gravitational or nuclear, the change in 'mass' can be reduced to the change in potential energy.

What for bringing up the extended equation? In the centre of mass frame it reduces to the familiar one anyway.

[Tylui]

Less obviously, it occurs in chemical reactions, such as photosynthesis - the mass of the products is very very slightly greater than the reactants ( due to binding energies IIRC) and the energy from sunlight makes up the difference.

Even less obviously it occurs when stretching a spring, or lifting a ball in a gravitational field.

No, not at all. That's energy. Energy and mass are the same thing, yes, but they're not the same thing if you catch my drift. Mass is a particular form of energy. Gravitational potential energy is not mass. This paragraph gives me a funny feeling in my stomach that tells me that I'm not sure, though.

E=mc² is something of a lie-to-children. The proper equation is E²=(pc)²+(mc²)²

What do you mean? Energy and mass are the same thing in GR. Rest mass is a particular form of energy.
In all cases involving binding energy, be it chemical, gravitational or nuclear, the change in 'mass' can be reduced to the change in potential energy.

What for bringing up the extended equation? In the centre of mass frame it reduces to the familiar one anyway.

In the center of mass frame for the ball, changing the gravitational field around it doesn't change its mass...

[Il Palazzo]

Of the whole system. Not the ball.

[Tylui]

That's silly too? The Earth doesn't become more massive because of a ball in its gravitational field.

Try this: Take a spring and weigh it. Now stretch the spring and weigh it again. Has its mass changed? Of course not.

[Il Palazzo]

Try this: Take a spring and weigh it. Now stretch the spring and weigh it again. Has its mass changed? Of course not.

Of course yes. You added energy to the system from outside. The total energy of the system is now higher. It has thus both higher inertia and is curving the space time more - the two qualities that are thought of when somebody brings up mass without any qualifiers.
Does the rest mass of whatever particles make the spring increase? No. But it is now heavier.

[Putnam]

"Mass" usually refers specifically to rest mass; relativistic mass is a concept that mostly just confuses people, which is why I brought up the full equation (relativistic mass is just referred to as total energy or summat now, for the most part).

[Il Palazzo]

"Mass" usually refers specifically to rest mass; relativistic mass is a concept that mostly just confuses people, which is why I brought up the full equation (relativistic mass is just referred to as total energy or summat now, for the most part).

I'm not sure why you brought this up.
You're using the term incorrectly. Relativistic mass is a SR term. It makes no sense using it when talking about gravity, which we are. You can't talk about weighing the relativistic mass because that requires the presence of a gravitational field.
Furthermore, the relativistic mass is an observer-specific effect. In the rest frame of the system's centre of mass it reduces to rest mass as the gamma factor goes to 1.

With E=m you have the sum of all energy components on the left and the resultant rest mass of the system on the right. If you increase the energy of the system in any way, it'll weigh more.

Yes, that's the same as the rest mass of the system increasing - and as long as it is clear that it's the rest mass of the whole system I have no qualms with it.

But it can be misleading, at least in the way you used it, as it suggests some elementary particles need to pop up, whereas the rest mass of the system is a conglomerate of the rest mass of the elementary particles contained therein, and all other forms of energy including potential energy.

[Gentlefish]

A stretched spring doesn't have more energy, though - I'm assuming you're speaking of a spring stretched to the point of distortion - because once you stop stretching it there's no energy there. And potential energy doesn't increase mass. If I put two similarly massive balls on shelves of different heights, the ball on the higher shelf isn't going to weigh more. And, actually, it's not going to weigh more as it's falling - there hasn't been any energy added to the system of the ball itself. It's simply attracted to the earth.

[lemon10]

I'm going to poke in with a completely irrelevant point: The ball on the shelf does indeed weigh less then the ball on the floor, as its closer to the center of the earth. Its a trivial amount, but the distance from the source of gravity does indeed affect the weight. Similarly, the falling ball will weight more with every second it falls, even though the amount is extremely tiny.