Conservation of mass/energy.

[Agent Intellect]

Why is this true?

Why is this 'considered' true?

Can mass/energy be arbitrarily created or destroyed?

If so, how?

...or, perhaps, why? (more of a philosophical question, maybe).

Is it safe to base other theories/hypotheses of physics/chemistry on this "law"?

How is this law proven aside from empirical evidence that it hasn't happened so far?

(Sort of a broad intuitive leap that maybe only I am making here) how do we know that information isn't completely lost in a black hole (I can give a brief explanation of Leonard Susskind's answer if need be, but to me it seems unsatisfying)?

Inside of black holes, there is this idea that 'classical' physics breaks down. Could the conservation of mass/energy also break down inside a black hole?

If humans figured out how to actually destroy or create matter, how would this effect the science of physics?
How would it effect our everyday lives (eg positively or negatively)?

 

[Melllvar]

Why is this true?

Technically I think only conservation of energy really holds, which would seem to follow from the definition of a closed system. If everything in the system (matter, space, etc.) is a form of energy, then if the energy of the system is constant nothing can be created or destroyed, only changed in form.

Noether's theorem is probably a more technical answer:

Noether's (first) theorem states that any differentiable symmetry of the action of a physical system has a corresponding conservation law.

If a system has a continuous symmetry property, then there are corresponding quantities whose values are conserved in time.

For illustration, if a physical system behaves the same regardless of how it is oriented in space, its Lagrangian is rotationally symmetric; from this symmetry, Noether's theorem shows the angular momentum of the system must be conserved. The physical system itself need not be symmetric; a jagged asteroid tumbling in space conserves angular momentum despite its asymmetry – it is the laws of motion that are symmetric. As another example, if a physical experiment has the same outcome regardless of place or time (having the same outcome, say, somewhere in Asia on a Tuesday or in America on a Wednesday), then its Lagrangian is symmetric under continuous translations in space and time; by Noether's theorem, these symmetries account for the conservation laws of linear momentum and energy within this system, respectively.

Why is this 'considered' true?

Induction.

Can mass/energy be arbitrarily created or destroyed?

If so, how?

Vacuum excitations? Pair production?

...or, perhaps, why? (more of a philosophical question, maybe).

Is it safe to base other theories/hypotheses of physics/chemistry on this "law"?

How is this law proven aside from empirical evidence that it hasn't happened so far?

(Sort of a broad intuitive leap that maybe only I am making here) how do we know that information isn't completely lost in a black hole (I can give a brief explanation of Leonard Susskind's answer if need be, but to me it seems unsatisfying)?

Inside of black holes, there is this idea that 'classical' physics breaks down.

How so? The same rules seem to be obeyed inside a black hole as outside. It's already non-classical in that black holes are a GR phenomenon.

Could the conservation of mass/energy also break down inside a black hole?

Going by the above theorem, it would seem to require that the curvature of spacetime be capable of breaking the symmetry of various laws with respect to time. Considering that everything works the same inside a black hole as out, afaik, except in a highly curved spacetime, it seems unlikely. However, since other rather bizarre temporal predictions arrive from GR (e.g. CTCs), I suppose it's worth at least considering rather than ignoring. (I don't really have the skillset to properly 'consider' this though.)

If humans figured out how to actually destroy or create matter, how would this effect the science of physics?
How would it effect our everyday lives (eg positively or negatively)?

They do create and destroy matter, I believe a large portion of the rarer isotopes for nuclear medicine are man-made at reactors. Destroying matter being even more common in nuclear power. Creating or destroying energy would be more bizarre.

In a sense energy conservation violations occur all the time on a quantum level in tunneling effects and such. The uncertainty relation between energy and time allows a system to have an anomalous amount of energy for an effectively immeasurable amount of time (beyond the limits of the uncertainty principle), and if you can't measure it to prove that it shouldn't have happened, then the entire idea of a violation is kind of irrelevant.

 

[OrionzRevenge]

...

If humans figured out how to actually destroy or create matter, how would this effect the science of physics?
How would it effect our everyday lives (eg positively or negatively)?

You might be able to Break Einstein's Bamboozle Boomerang (Lorentz Term) and invent warp drive.

X&Y start at 0
X= % the speed of light ( c )
Y= goes to infinity where it finally intersects with one on the X scale.

For Einstein the observer IS always stationary and (Space - Time) & (Mass - Energy) are conserved in order that The speed of light is ALWAYS 186,000 miles per second for ALL observers. AND ONLY LIGHT CAN TRAVEL 186,000 miles per second

The classic example of an astronaut headed for the nearest star (4.2 L.Y. away) in a space ship going 90% LightSpeed (c) expects it to take about 5 years to reach.

But it only takes him about 1 year. He shits his pants thinking he has gone faster than c and rushes back to Earth in another year to announce his conquest.

Where he is greeted with: " You've been gone 10 years dumbass... but you've held up really nicely"

HE is not WRONG ...well, about how long it took.
THEY are not WRONG
and c is c is c is c as always 186,000 miles per second for ALL observers.

The solution: While in transit TIME dilated - stretched about 4x. (His clock ticked 1 second for every 4 seconds the clocks on Earth ticked)

AND

The distance (SPACE) to the nearest star shrank to 1/4 or about 1 L.Y.
In fact his entire universe shrank to 1/4 th. what we understand it to be here on Earth.

Same applies to Mass-Energy

As you get closer and closer to a speed of 186,000 miles per second, you get less and less an increase in speed from the energy being poured out of the rockets.

Solution: ONLY LIGHT CAN TRAVEL 186,000 miles per second, so @ 90% of c, the ship's mass is 4 times what it was on Earth as Energy is converted into Mass (and the ship becomes that much harder to accelerate.
===========================================
So then if you can Break Einstein's Bamboozle Boomerang as it relates to (MASS/ENERGY)
Then You'll also break it for (SPACE/TIME)

...and Boldly go where no one has gone before.

 

[Jordan~]

It always puzzles me that things in perception can happen instantaneously - i.e. where no information is transferred, like the appearance of a shadow or a laser point jumping from one surface to another. Where are those things happening? Can we do stuff there, too?

 

[smithcommajohn]

This thread has sparked an old question that has bounced around in my mind since childhood.

If we are on a spinning orb rotating around a star which itself is rotating in a galaxy which is presumably flying through space... How can we ever know our own velocity and direction and what impacts that might have on how the speed of light might have an effect on travel away from the Earth?

In other words, how do we know we are not already traveling near the speed of light? Is it all relative or is there an absolute speed we are traveling in space? With no point of known motionlessness, can we ever know? *brain explodes*

 

[Jordan~]

I'm pissed off that I don't go flying off into space every time I jump outside because I've forgotten why that doesn't happen. Stupid universe, you're a liar!