say i (not necessarily human) am in a big-ass earth-sized intra-universal vehicle.
suppose:
-said vehicle is covered (in a high orbit) in a shell or membrane which is strong, internally supported, and which almost ideally reflects internal radiation (like supar kevlar mylar)
-said vehicle uses nuclear or matter-antimatter reactions as an energy source (for internal uses, not for like propulsion or anything (see following))
-said vehicle has been travelling at a high velocity for a loooong time (with a high initial velocity, and no internal acceleration) (and, miraculously, has had no collisions (not even with a nanospeck of hydrogen))
so, all that said, will my vehicle have an acceleration (to an outside observer)? if my vehicle has transformed a significant portion of its mass into energy (but, internal energy), would i notice a change in velocity? would an outside observer?
You don’t convert mass to energy. Mass is energy, and energy is mass. So if you don’t dump excess heat to the outside, the heat - and thus mass - is stored somewhere within your vehicle. The total mass remains constant.
Actually, even if you dump heat/mass outside, you don’t accelerate. (Unless you dump heat in a particular direction). If the coupling in the middle of a train breaks, the whole thing doesn’t suddenly accelerate or deccelerate - it keeps going at the same speed.
Does that answer the question? (I’m not sure if I understood the point of the OP.)
look, i’m not saying this to be a dick, but one does convert mass to energy. at least in terms of this discussion. there’s a big difference between simply dropping Fat Man on a city, and dropping a primed and ready-to-explode Fat Man on a city. mass and energy (according to einstein) are equivalent, but they are not the same. otherwise we would no have different words for them.
If you ship is at rest and we set off a mergatroid bomb, the ship will still be at rest. Now, let’s take the ship moving at a constant velocity. If the ship is moving at a constant velocity, it will be at rest with respect to an inertial frame moving at that velocity. So, the answer is no, the ship will not accelerate. Energy and mass have the same graviataional and inertial effects.
I see it the way scr4 says it. Mass and energy are just aspects of mass-energy.
You can look at it another way. Every action has an equal and opposite reaction. Anything that happens within a closed system won’t affect the acceleration of that closed system. So it doens’t matter if you’re jumping up and down on one side, fighting an internal war, or setting off huge bombs. System is closed, so ther e is no change.
No, “convert” implies that one disappears and the other appears. That is not the case here. Say you are in a sealed box which is sitting on top of a scale. You have in the box one milligram of antimatter, and an enormous battery. You annihilate the antimatter and use the energy to charge the battery. What happens to the reading on the scale? If you can convert mass to energy, you’d expect that the whole box will suddenly weigh 2mg less. But that doesn’t happen, because the charged battery now weighs 2mg than it did before. As I said, energy is mass and mass is energy. Different sides of the same coin.
jb, I think scr4 is correct: mass is energy. Just like heat is energy and gravitational potential is energy and chemical bonds are energy. We have different names for them because they are in somewhat different recognisable forms, but they are all still energy. Just like water, ice, and steam are all H2O. If you had your ship on a big-ass scale, it would weigh the same whether the interior was filled with matter, or if that matter was all converted to energy. The mass of the system would be the same. At least, I think that’s right. The terms “matter” and “mass” get a little slippery in these situations. One of the local physics geniuses will be along to correct me if I’ve flubbed it, I’m sure.
You can’t say that mass equals energy, but you can say that mass equals the energy that cannot be transformed away. Mass is the time component of the energy-momentum four vector and momentum is the space component.
m[sup]2[/sup] = E[sup]2[/sup] - p[sup]2[/sup]
c = 1
m = mass
E = energy
P = momentum
So, as long as the momentum is less than the energy you have mass.
Also, mass cannot be converted to energy, the energy from a nuclear explosion derives from the increase in binding energy, and the decrease in potential energy. The local mass defect is the result of the decrease in energy not the cause, and the system mass remains the same.