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Author Topic: Can a stable universe defined by only by Classical mechanics exist?  (Read 4517 times)

Offline joepierson

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Nice site! just found it, armchair scientist here, first post...

Suppose a universe existed that obeyed classical mechanics everywhere, at all extremes, micro and macro, at low and high speeds, is that theoretically possible?

Sometimes I wonder whether quantum and relativistic mechanics are a necessity, a bare minimum requirement for a stable universe, and not some strange quirk of our universe that seems to defy common sense.


 

Offline Pikaia

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Can you clarify what you mean by "classical"? Do you mean Newtonian as opposed to Relativistic? Or do you mean non-Relativisitic as opposed to Relativistic? (Relativity is sometimes described as a classical theory because it does not include quantum mechanics.)
 

Offline graham.d

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Welcome, Joe. I have a suspician that the answer is "no" and the complexity is actually a necessary part of the universe's existence. I wonder more, in the other extreme, whether we will ever get a complete understanding of everything. I have a suspician it is maybe rather like Feynman's "peeling the onion" analogy with each step revealing yet another level of complexity.
 

Offline imatfaal

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Joe - further to Pikaia and Graham -  bear in mind that it has been noted that Mercury's orbit can only properly calculated once GRelativity is taken into account -  So I think the answer is no. Our Universe does not (in the very-micro and the very-macro) follow classical Newtonian rules.  On the earth, in purely everyday situations then Newton is grand, but GPS navigation satellites need to be corrected for both time dilation due to velocity and gravitational potential; so we must acknowledge we do need non-Newtonian physics.

Could a universe exist on a purely newtonian and deterministic model? - perhaps yes: but it would be very boring.  Chemistry and physics are much more accessible and simpler when everything is straightforward and non-random - unfortunately everything about our world is stochastic and non-deterministic.  So whilst we may teach and learn about a straight-forward classical world - that is merely an approximation to the reality which is endlessly more complicated.
 

Offline Soul Surfer

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The answer is no. The reason for this is that the inverse square law of gravity prevents this. Two gravitating lumps can be in a stable orbit around each other in totally empty space.  It is possible for three bodies with different masses) to be in a stable orbit around each other provided they are  arranged in an equilateral triangle.  There are a few very special cases where more than three bodies OF EXACTLY EQUAL MASS gan be in a complex sort of orbit together (a relatively recent discovery) but apart from this there are no long term stable configurations of mass and all mass will eventually collapse into a black hole and vanish from the universe.  so if you count a single black hole as being a stable universe the answer is yes otherwise the answer is nothings must be expanding (because they have sufficient kinetic energy to avoid being gravitationally bound or collapsing.
 

Offline Geezer

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I think Joe is describing a different universe from our universe, and wondering it it could operate only on Newtonian Mechanics.

If I have that right, I suspect it is not possible to come up with a definitive answer.
 

Offline JP

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If your only requirement is that it operate on Newtonian mechanics than it can exist in your mind.  Of course, since it doesn't obey the same rules as our universe, I'm not sure what useful information you would get by thinking about it.
 

Offline Soul Surfer

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Please note that the bending of light rays and black holes exist in newtonian mechanics and do not require relativity.  Relativity introduces only a slight but significant change in the amount of bending to be expected.

The basic simple laws of classical physics imply that we must live in a dynamic and evolving universe it just cannot be static.  This was known and understood by the best scientists for many years before modern quantum and relativistic science and was a great source of worry for them.  The most fundamental physical law (the second law of thermodynamics) that entropy must continually increase assures this.
« Last Edit: 09/02/2011 09:14:46 by Soul Surfer »
 

Offline joepierson

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Welcome, Joe. I have a suspician that the answer is "no" and the complexity is actually a necessary part of the universe's existence. I wonder more, in the other extreme, whether we will ever get a complete understanding of everything. I have a suspician it is maybe rather like Feynman's "peeling the onion" analogy with each step revealing yet another level of complexity.

I guess I'm thinking the it may get rid of the infinities, therefore makes the universe realizable. That is, the non-classical mechanics seems to put stop signs everywhere, speed can't be infinite, you can't ground up a piece of copper infinitely into smaller and smaller copper particles, you have quanta of energy, quanta of photons, quanta of matter etc etc.
« Last Edit: 09/02/2011 23:03:48 by joepierson »
 

Offline joepierson

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If your only requirement is that it operate on Newtonian mechanics than it can exist in your mind.  Of course, since it doesn't obey the same rules as our universe, I'm not sure what useful information you would get by thinking about it.

In general, I find you may get great insight about any question by inverting the question. That is, if you want to figure out why something behaves in a certain manner, you may get the answer more easily by pondering the results of  the opposite behavior. For instance, if you want to be successful in life examine unsuccessful people and avoid all their behaviors.

 

Offline JP

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Other people share a lot of biology and psychology with you, though.  In this case, I think you're comparing apples to oranges.  If you remove quantum mechanics and general relativity, you've fundamentally changed the rules of the universe.  GR might be easier to theorize away, since it tends to be important on large scales, but everything is made up of quantum mechanical particles, so if you remove quantum mechanics, you need to suddenly explain all matter and forces in the universe in terms of something new.  One major problem would be that you'd need a new explanation of how matter is held together--in a purely classical universe there's no way to explain the fact that atoms are stable: the electrons would spiral in to the nucleus, and the nucleus wouldn't be stable, since there are no gluons to hold all the protons together.
 

Offline wolfekeeper

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Yes, the atoms in your body are held apart by quantum mechanics; you can show that atoms can't be held apart only by charged particles (Earnshaw's theorem). Therefore if an entirely classical universe can exist, it wouldn't have any solid objects in it!
 

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