Momentum, energy..the universe.

[tikiman420]

I hate to use this site as "homework help" and i dont have the intention of having you all do my homework for me, however, i am confused about this question we have in physics class. we are supposed to write an essay on the subject of momentum and energy. the question is

"How are energy and momentum properties of individual objects? How are they properties of the universe as a whole?"

For the first part, i plan on just giving examples of how all types of energy (mechanical, chemical, electomagnetic, thermal, and nuclear) relate to objects, and how momentum relates to objects. however, i'm a bit lost on the universe part.

i have kind of an idea for momentum, but overall i'm not really sure on both momentum and energy. if anyone can help me out it would be great.

[tikiman420]

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[MonkeyMensch]

As a sort of semi-bump and elaboration: I was thinking of posting a thread about this sort of question. What is the skinny on inertia and the structure of the universe? I think Mach had something to say regarding this. The thought experment I recall is an observer and a bucket of water in an otherwise empty universe. If the observer spins the bucket around the surface of the water becomes curved. But how is the observer to tell if he and the bucket are rotating at all?

Any help is appreciated in advance...

[Chronos]

For the Universe as a whole, try thinking about frames of reference. As an example: What's your momentum when you're walking down a hallway? What if the hallway is the aisle of a moving train?

And now, ask yourself this: What frame of reference should you use to describe the Universe?

By the way, you probably want to wait a little longer than two hours before bumping your threads. The mods don't mind one bump, but after two hours, it's still on the front page, so a bump isn't really necessary.

[NoCoolUserName]

The total momentum of the universe is always the same.
The total energy of the universe is always the same (but getting more dispersed).

Warning: depending on how you feel about black holes, both of these may be false.

Does that help? :)