Is our universe a closed system?

[Simonski]

how do scientists know that anti-mater exsists

I second that question! To wikipedia!

 

[c'mon sense]

Is energy really a "something" or is it merely a convenient conceptual construct that helps us model physical transformations - say, like money, which enables the transformation of a product into another?

The same would then apply to mass. I understand mass as a property of matter, but not as matter itself.

So, if I were to express it in terms of my money analogy, I would say that E=mc^2 simply says that the ratio of "money" to "value" is c^2 in this Universe.

Also, another question regarding entropy reducing mechanisms: isn't gravity such a mechanism? I'm thinking black holes.

 

[Jig]

Quantum fluctuations. There's a foam of particles popping in and out of the vacuum all the time.

Though such occurrences do not violate the Law of Conservation of Mass and Energy, Bell's theorem shows that these are impossible to predict. These particles may only seem to be popping in and out of existence.

 

[Dragar]

Though such occurrences do not violate the Law of Conservation of Mass and Energy

Yes, they do, for a small time (which must be small enough such that the uncertainty principle is not violated).

, Bell's theorem shows that these are impossible to predict.

No, it doesn't. Bell's theorem shows that no local hidden-variables theory can reproduce the predictions of quantum mechanics.

 

[Dragar]

Is energy really a "something" or is it merely a convenient conceptual construct that helps us model physical transformations - say, like money, which enables the transformation of a product into another?

Energy is a conserved number, due to the fact that the laws of physics aren't changing with time. That's it.

The same would then apply to mass. I understand mass as a property of matter, but not as matter itself.

It depends what you mean by 'matter itself'.

Mass is a measure of two things - how resistant an object is to changing its momentum (how hard you need to push it to move it), and how strongly it attracts other objects via gravitational attraction. It is not a coincidence that it measures both of these things.

Whether or not that's a 'something' - well, that depends what you think a 'something' is. I certainly don't think of energy as anything other than a conserved quantity due to time invariance though, or mass as anything more than the above definition.

Also, another question regarding entropy reducing mechanisms: isn't gravity such a mechanism? I'm thinking black holes.

I think, though could be mistaken on this point, that Hawking radiation provides the mechanism by which black holes increase the entropy of the universe.