Some deep physics questions.

[the_cobbinator]

I got to thinking while on a trip to a baseball tournament about physics (Yes, I am a nerd). Okay, here goes:

1) Since energy isn't created or destroyed; only transformed, wouldn't that mean there is a finite (albiet astronomical) amount of energy in the universe? If so, the universe would eventually "run out" of non-dissipated energy, and everything would grind to a halt, right?

2) If Fg = G * ((m1*m1) / r^2), wouldn't that mean you would experience weightlessness at the center of the earth? Or, rather, if you calculate it mathematically, 0^2 is 0, so your answer would be infinite.

I've got more, but I'm starting to get a headache. Just wondering what your input is.

 

[Mike Rotch]

1) Since energy isn't created or destroyed; only transformed, wouldn't that mean there is a finite (albiet astronomical) amount of energy in the universe? If so, the universe would eventually "run out" of non-dissipated energy, and everything would grind to a halt, right?

I think you asked and answered this one yourself. Energy cant be "destroyed" and therefore I guess there would be a "finite albeit astronomical" amount of energy in the universe. However it wouldnt "run-out" as it is recycled.

A loose example would be the energy created as a star burns. The star goes through various stages of maturity until its "combustible matter" is all used up. Then the core becomes "combustible matter" and the star becomes supernova before exploding. When it explodes, all the matter contained in the star is thrown outwards into space. After hundreds of thousands or millions of years it cools, forms clouds with other ejected matter, a new sun is borne and the process begins again.

A bit of a "nebulous" (ha! ) explanation, but I have forgotten the details of how a star functions...

 

[wellyrn]

if were fire-proof you would just float in the center of the earth i would assume as you can't fall "up".

 

[HareTurtle]

Hmmm. ..

To question 1)

That energy is neither created nor destroyed does not imply that the universe and it's energy content are finite. Assuming that the universe is finite, which I believe is currently the consensus view, the second law of thermodynamics would suggest that an eventual "heat death" of the universe is inevitable. However, a different school of thought suggests that as energy dissipates, the expanding universe may collapse. In either case, we'll be pretty well dissipated ourselves before either event occurs.

On question 2)

The equation you provide describes gravitational force as a scalar quantity. This is applicable for two objects separated by distance so that the force operates in a single direction. In the case of a body at the center of the Earth, a vector form of the equation would be applicable. You would be weightless at the center of the Earth because the gravitational force to which you are subjected would be equal in all directions. Of course you would be much too dense to appreciate it.

 

[the_cobbinator]

Hmmm. ..

To question 1)

That energy is neither created nor destroyed does not imply that the universe and it's energy content are finite. Assuming that the universe is finite, which I believe is currently the consensus view, the second law of thermodynamics would suggest that an eventual "heat death" of the universe is inevitable. However, a different school of thought suggests that as energy dissipates, the expanding universe may collapse. In either case, we'll be pretty well dissipated ourselves before either event occurs.

On question 2)

The equation you provide describes gravitational force as a scalar quantity. This is applicable for two objects separated by distance so that the force operates in a single direction. In the case of a body at the center of the Earth, a vector form of the equation would be applicable. You would be weightless at the center of the Earth because the gravitational force to which you are subjected would be equal in all directions. Of course you would be much too dense to appreciate it.

Wow, really educated answer! Thanks. I did some research on both the heat death theory and the universal collapse theory and as of now, am leaning more towards the inevitable heat death. The main reason being that, in an astronomical sense, the temperature extremes are not as low/high as they once were.

For your answer to question two, do you mean dense as in you'd be squashed (in lack of a better term)?

edit: here's a good link for the heat death theory: http://www.physlink.com/Education/AskExperts/ae181.cfm

 

[hanker]

Oh my, it's summer vacation, my mind cant think this deep right now.....I'll be leaving now

 

[Event]

A bit of a "nebulous" (ha! ) explanation, but I have forgotten the details of how a star functions...

ha, n00b.

Anyway, to number 2, Fg=g(m1m2/r^2), when r=0, there is no answer. You would have m1m2/0 and you can never devide by zero. To calculate Fg when r=0, you would need a much more complex equation, Fg=g(m1m2/r^2) is not the perfect equation. The ultimate goal of physicists is to find an equation that works in all situations, which is not going to ahppen any time soon.