What does e = mc^2 actually mean?
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Energy and mass are the same thing. It’s like recognizing that light and radio are the same thing.
Einstein determined that matter can be converted to energy, which is what happens in a nuclear reaction. The products weigh a bit less than the reagents, and the missing mass is converted into energy according to that equation.
The E is for energy, m is for mass, and c is for the speed of light
I find it funny that robot chicken did a sketch on e=mc2. It’s very basic.
The equation is pointing to that the total energy any matter has. is directly related to its mass.
The C in the equation is speed of light in a vacuum. It’s so strange that the raw speed of light. is fundamental in so much of physics.
The robot chicken video.
The ELI5 is that for special relativity to work, things going faster have to be harder to accelerate. It’s a consequence of the two postulates of special relativity, physics are the same for everyone, and everyone in the same inertial reference frame (accelerating at the same rate) sees light moving at speed c.
As a result things moving faster must gain inertia and therefore mass. Therefore the mass/inertia -in general- should be the result of energy. Kinetic energy is one form of it. Nuclear binding energy is another. In fact 99 percent of mass a proton or neutron is a result of the binding energy of the quarks that make it up.
Individual particles like quarks and electrons do still have a rest mass, but even that is still considered equivalent to energy as when something like a particle and antiparticle collide all the stuff that must be conserved (called quantum numbers) add up to zero, the particles cancel each other out, and you are left with energy. Alternatively when you have a crapton of energy in one spot that energy can spontaneously form particles via pair production.
Basically this is what particle accelerators do. Speed up some particle so it has a crapton of energy, smash it into something, and watch all the stuff that gets spontaneously formed.
The full explaination involves math that’s a good deal beyond basic calculus :F
When an object is at rest (compared to the observer), then that object has energy equal to its mass times the square of the speed of light.
You can indeed release some of this energy, depends on what kind of object it is and what process you use, and afterward the mass of the object will be reduced.
Note that in the old days physicists used to interpret this equation as saying mass and energy is the same, but we no longer do that now, not in that simplistic manner. That interpretations have problems when the object is moving. So now mass is only directly correspond to energy when the object is at rest (compared to the observer). Unfortunately, the old interpretation still stick around in lower level textbook.
It means the energy of a particle is equal to it’s mass times the speed of light squared. Whenever energy is released in a chemical or nuclear reaction, a corresponding amount of mass is lost.
This is why nuclear reactions are so powerful. The atoms get split apart and that tiny amount of mass represents a huge amount of energy.
In special relativity, there is a formula for the kinetic energy of an object E_kinetic = m * c^2 * (ɣ – 1), where ɣ is a term that depends on your speed. Einstein found that, if an object with this kinetic energy emitted some light, the only way for energy and momentum to both be conserved was for the mass m of the object to be reduced by some amount Δm. He also found that the emitted radiation gained an amount of energy equal to Δm * c^(2) (in addition to the energy that came from the object slowing down). Putting it into a physical example, if you shine a flashlight that’s moving, some of the emitted light-energy comes from the kinetic energy of movement, and an additional Δm * c^(2) of it comes from a reduction in the mass of the flashlight.
This argument is very broad, since we don’t rely on the energy being stored in any particular place in the object. All mass is energy, and given an appropriate interaction, it can be converted to other forms of energy. Since Einstein’s day, we have more or less ‘found’ where all the mass-energy is in normal matter. Quantum fields can store some energy by having some value above what they have in the vacuum, far away from other particles. Some mass is stored in the electric fields surrounding charged particles, and we can liberate it by reducing the field strength (e.g. by bring an electron and proton close together). More mass is stored by the Higgs field, which gives electrons and quarks their ‘bare mass’ (mass without the contributions from the gluon and electric fields). Most mass is stored in the gluon field, which is the field responsible for binding quarks into protons and neutrons, and binding protons and neutrons together. In a nuclear explosion, we liberate a little bit of this energy (only the part associated with binding protons and neutrons together – we don’t have a good away of getting energy out of quark bonds).
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