physics question

Luger187

Luger187

Well-Known Member
ok lets see if i can explain this. im high so it might not come out right lol

lets say the stars in the universe converted most of the hydrogen in space into heavier elements. the mass would no longer be a general 'web' of gravity as it was with all the gaseous hydrogen around. it would be more concentrated in planets and what not.

im wondering how gravity acts different when you have one large massive object, as opposed to trillions of tiny particles floating all around. im imagining a huge cloud of hydrogen as trillions of tiny particles, each pulling in their own direction. the planet would pull stronger in a single direction.

im thinking as the atoms get more concentrated(planets), yes they pull harder, but the planets are also larger distances apart. its sort of a trade off, right?

could the reason the universe is expanding be because the hydrogen is coming together to make heavier atoms, which are then contained in smaller, yet more massive, 'packets' that we call planets, and thus gravity loses its grip more and more as a whole.

idk its hard to put what im imagining into words
 
RyanTheRhino

RyanTheRhino

Well-Known Member


M1 = mass of object one
M2 = mass of object two
G= gravataional constant
r= distance between objects
f= the force of atraction.

In space who is to say that the planet isn't flying toward the lone hydrogen atom. Its all your point of perspective

What you have there is a superposition problem. This just mean you would have to plug each atom into the equation posted above and take the sum of the force.

a bunch of spread out light hydrogen atoms would just pull on each other and have an almost bet zero force
 
RyanTheRhino

RyanTheRhino

Well-Known Member
I think you would like this video. It may answer your question

[video=youtube;DECAorZYErk]http://www.youtube.com/watch?v=DECAorZYErk&feature=player_detailpage[/video]
 
theinhibitor

theinhibitor

Well-Known Member
The gravitational force between two bodies is not proportional to the density. It might be hard to imagine, but a gaseous could of mass M would pull you towards it with the same force as a planet with mass M. The only difference would be at the surface of the two. The planet would be smaller, and therefore you could get closer to the center, decreasing r, and exponentially increasing the force exerted by the planet on you. Basically, what im saying is that the planet has the potential to exert greater force on you, but at the same distance the force is the same.

The universe is expanding outwards but slowing down so gravity isn't changing and becoming weaker. Unless our current laws are disastrously wrong, matter can't be created so the net amount of gravitational energy in the universe doesn't change.

As for fusion, the net energy released by the hydrogen (which some say is the potential energy created at the point of the big bang) is netted by the absorption of this energy in surrounding matter. For example, lets say the a hydrogen atom undergoes fusion and releases radiation. This radiation may be absorbed by a water molecule on earth, which evaporates into the atmosphere, and as it rises, so does its potential. So the energy is balanced (in this example. of course the sun and earth isnt a closed system).

The wikipedia article on energy actually has some well written portions on the amount of energy in the universe and energy transformations at the big bang.
 
theinhibitor

theinhibitor

Well-Known Member
On a side note, gravity is a pretty neat force if you think about it. Very very weak compared to almost all the other forces (especially electric forces). But, it grows over time. Imagine you have a particle. The gravitational field exerted around that object is lets say G. Now lets say it pulls another particle. The gravitational field is DOUBLED to 2*G.

Conversely, with an electric force, lets say you take a positive charge. Well, it would exert a much stronger field. But this field would attract a negative particle, thus canceling the field.
 
Tenner

Tenner

Well-Known Member
I get what your thinking Luger you explained it well but sucked towards the end lol Nice idea you have though it didn`t occur to me before.

So your saying that we have a universe of X size big enough for all the dust particles around. The dust particles start attracting each other and shift places (ideally towards the center) leaving empty space all around them and if we were to think of this universe as a bubble or sphere, they are distancing themselves from the surface area. They would be losing their "grip" on this bubble due to the inverse square law of gravity and the sphere would keep expanding and expanding.

You would be assuming empty space has a mass for this theory but its a good idea it must have some effect over it.

Stephen hawking belives the answer for the question is it an expansion or contraction lies by dark matter but we can`t even define that stuff lol

How do we look at infinity though I`m wondering. I mean our bubble of a universe has walls that expand faster than the speed of light. It doesn`t look like infinity on the first sight, but technically this situation does yield infinity. I mean an infinate distance implies you can never reach the end right? :)

So we`re expanding into what? Whats that thing expanding into? If its all just expanding at the rate of 34000 km/h (was that the number?) then theres nothing to ponder, thats infinity!

Hmm hmm... I`m carrying off on some ramblinb thoughts here lol
 
RyanTheRhino

RyanTheRhino

Well-Known Member
Tenner said:
I get what your thinking Luger you explained it well but sucked towards the end lol Nice idea you have though it didn`t occur to me before.

So your saying that we have a universe of X size big enough for all the dust particles around. The dust particles start attracting each other and shift places (ideally towards the center) leaving empty space all around them and if we were to think of this universe as a bubble or sphere, they are distancing themselves from the surface area. They would be losing their "grip" on this bubble due to the inverse square law of gravity and the sphere would keep expanding and expanding.

You would be assuming empty space has a mass for this theory but its a good idea it must have some effect over it.

Stephen hawking belives the answer for the question is it an expansion or contraction lies by dark matter but we can`t even define that stuff lol

How do we look at infinity though I`m wondering. I mean our bubble of a universe has walls that expand faster than the speed of light. It doesn`t look like infinity on the first sight, but technically this situation does yield infinity. I mean an infinate distance implies you can never reach the end right? :)

So we`re expanding into what? Whats that thing expanding into? If its all just expanding at the rate of 34000 km/h (was that the number?) then theres nothing to ponder, thats infinity!

Hmm hmm... I`m carrying off on some ramblinb thoughts here lol
Click to expand...
From what we know the only way for the gravitational force to = 0 is if the distance is infinity. We can never reach infinity ( yes i know they say space is infinitely large) but that is not the same for the math.

There will always be a force by gravity. Granted it may be very tiny and appear as zero. eventually when the objects loose momentum they will all start coming back together via a black-hole. This would take a number of years not even imaginable because it would be way to large.

Once all the super-massive black-holes collide we will be back to the start of the universe
 
Prefontaine

Prefontaine

Well-Known Member
theinhibitor said:
On a side note, gravity is a pretty neat force if you think about it. Very very weak compared to almost all the other forces (especially electric forces). But, it grows over time. Imagine you have a particle. The gravitational field exerted around that object is lets say G. Now lets say it pulls another particle. The gravitational field is DOUBLED to 2*G.

Conversely, with an electric force, lets say you take a positive charge. Well, it would exert a much stronger field. But this field would attract a negative particle, thus canceling the field.
Click to expand...
the thing your not taking into acount is that when you stand on the earths surface particles on the opposing side of the earth have little to no affect on you, at least in comparison to the particles your stand on, like if you have a certain amount of mass with almost no density each particl has to pull from farther away, but if you have that same mass with extreme density, ie a black hole your gonna be sucked apart and compacted,
 
Tenner

Tenner

Well-Known Member
RyanTheRhino said:
From what we know the only way for the gravitational force to = 0 is if the distance is infinity. We can never reach infinity ( yes i know they say space is infinitely large) but that is not the same for the math.

There will always be a force by gravity. Granted it may be very tiny and appear as zero. eventually when the objects loose momentum they will all start coming back together via a black-hole. This would take a number of years not even imaginable because it would be way to large.

Once all the super-massive black-holes collide we will be back to the start of the universe
Click to expand...
It sounds right to me but it would take a loooong long time :)

So I could say your implying that the universe isn`t on its first round with this cycle.

Then these "walls" that are expanding, are they really expanding? Do they contract too?

To say they aren`t expanding well apparently scientists have confirmed they are.

Then they must contract too or they would be far too wid to measure (on the assumption that the universe was always just here doing this).

But if they contract that means they are somewhat attracted to gravity too which is interesting to concider :)
 
theinhibitor

theinhibitor

Well-Known Member
Identical only in the fact that the force is proportional to the inverse square. My point was that it is a much larger force than gravity and that electric forces tend toward equilibrium but gravity does not. Gravity will pull and pull and get bigger with each pull while electric forces will balance because the net charge will attract the same magnitude of the opposite charge, canceling each other out.
 
RyanTheRhino

RyanTheRhino

Well-Known Member
I dint say any of that. the equations are identical the only difference is constant multiple.

gravity i G

Electro is K
 
Prefontaine

Prefontaine

Well-Known Member
Tenner said:
It sounds right to me but it would take a loooong long time :)

So I could say your implying that the universe isn`t on its first round with this cycle.

Then these "walls" that are expanding, are they really expanding? Do they contract too?

To say they aren`t expanding well apparently scientists have confirmed they are.

Then they must contract too or they would be far too wid to measure (on the assumption that the universe was always just here doing this).

But if they contract that means they are somewhat attracted to gravity too which is interesting to concider :)
Click to expand...
my understanding is that the universe started as a single point, which was energized and expanded as as that energy dissipates in our world, our universe will once again return to that single point.
 
Tenner

Tenner

Well-Known Member
Prefontaine said:
my understanding is that the universe started as a single point, which was energized and expanded as as that energy dissipates in our world, our universe will once again return to that single point.
Click to expand...
I don`t think the word "started" is an appropriate term. I also think the word "nothing" is only a theoretical concept and can never be applied in the phsyical world. Physics is always showing there is something even in vaccuum so the word nothing has never actually been used succesfully (in terms of indicating a space and making a claim that there is nothing there) so I don`t get why creationists can so comfortably sit back and start going on about how there was nothing and Mr. God came along and created everything lol

So I`m going to say no beginnings and no creation. Everything is just is and always will be in the most solid "AS IS" sense :)

But hey, thats just rambling on.

For the subject I agree with your understanding. I`m trying to establish that in order to claim the universe contracts one must accept that gravity attracts the blankest, emptiest space or it would just be matter coming back and blowing up while the rest of the universe just keeps on expanding to infinity.
 
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