Newtonian mechanics also went beyond what Newton could calculate or prove. He himself derived Kepler's laws from his differential equations. Only later workers like Laplace and Lagrange realized that one can describe the influences of different planets on each other and hence the Solar system as a whole based on Newtonian mechanics and perturbation theory (and hence work out predictions like the position of yet unknown planets such as Uranus, Le Verrier) - this is something Newton himself apparently did not dare to tackle

To me there is a chain of deeper and deeper descriptions from Kepler -> Newton -> Einstein.

Kepler has static laws, Newton has nonlocal differential equations, Einstein has local field equations.

Aractus,

I don't see how it can be said that the way Newtonian mechanics arises from Quantum mechanics is any less revolutionary conceptually than the way Newtonian physics arises from general relativity. QM is more than taking ordinary mechanics and adding a bit of fuzzy. The newtonian particle paths arise in QM as a limiting case from a much deeper principle.

Alex, in classical mechanics time is linear, gravity is a force (that moves at infinite speed), and the laws of motion work equally in both directions (forward and backward in time). But, time is unidirectional and relative, and gravity is not a force.

Take what happens at a black hole. As you approach the event horizon your time slows down compared to an outside observer. In fact, if I were watching you fly towards the event horizon of a black hole, time would slow so much that I would never see you reach it - you would essentially appear frozen as you approach it. But as far as you're concerned, time is flowing normally, and it's everything away from the event horizon that's now moving at crazy-fast speeds.

5 Billion years from now the universe will have expanded to the point that all matter will be the same temperature: just a fraction above absolute zero. The universe will essentially be dead. It'll still be here, but there'll be no one to observe it. It will just continue to expand, and eventually even protons and electrons will be torn apart. No one actually knows what will happen at that point, it's entirely possible that a new set of chemical physics will take over, but more than likely it'll just be that instead of frozen atoms scattered about space there'll be frozen quarks leptons and bosons scattered about space with no heat to do anything interesting.

This is the first time I'm hearing this. So in 5 billion years the universe won't be able to sustain life anymore?

(February 9, 2016 at 3:13 pm)Alex K Wrote: Brace yourselves for gravitational waves

I did. It didn't do any good. I still wiggled like jelly when it hit.

(February 13, 2016 at 8:24 am)Aractus Wrote: Alex, in classical mechanics time is linear, gravity is a force (that moves at infinite speed), and the laws of motion work equally in both directions (forward and backward in time). But, time is unidirectional and relative, and gravity is not a force.

Take what happens at a black hole. As you approach the event horizon your time slows down compared to an outside observer. In fact, if I were watching you fly towards the event horizon of a black hole, time would slow so much that I would never see you reach it - you would essentially appear frozen as you approach it. But as far as you're concerned, time is flowing normally, and it's everything away from the event horizon that's now moving at crazy-fast speeds.

5 Billion years from now the universe will have expanded to the point that all matter will be the same temperature: just a fraction above absolute zero. The universe will essentially be dead. It'll still be here, but there'll be no one to observe it. It will just continue to expand, and eventually even protons and electrons will be torn apart. No one actually knows what will happen at that point, it's entirely possible that a new set of chemical physics will take over, but more than likely it'll just be that instead of frozen atoms scattered about space there'll be frozen quarks leptons and bosons scattered about space with no heat to do anything interesting.

I can't speak about QM that far in the future, but in laypersons terms, I would guess "all this" is no different than the cycle of a the seasons changing over and over. 

You can correct me if I am wrong, but currently QM hasn't said either way finite vs infinite. Is that right as far as we know now? What we do know is that a cognition is not required either way.

If there was something prior, it would stand to reason, once all this breaks down, you'd have another quantum twitch leading to another big bang. 

I think the simplistic idea of on an off forever don't suffer the problem of infinite regress, because you aren't attempting to fill the starting point with something more complex. If my layperson's understanding is correct, this is simply going from off to on back to off. 

How far off am I?

QM doesn't know about the universe expanding and having an expiration date.

Aractus, I don't disagree in principle, except for three things, 5 billion years seems like a hopeless underestimation for the situation you describe since there will still be stars and star formation going on for much much longer (more like 10^100 years); the directionality of time already arises in Newtonian physics as a statistical phenomenon if you have an extremely low entropy state at one point. There is currently no evidence that cosmic expansion will rip apart things at short length scales such as atoms. A constantly accelerated expansion as it is caused by constant dark energy/cosmological constant does not do that

(February 13, 2016 at 9:14 am)Aractus Wrote: QM doesn't know about the universe expanding and having an expiration date.

Huh? The universe will suffer heat death. So it most certainly has an expiration date. The way we see it now will simply look different, so in that context yes, that period of our current look will have an end. The only thing QM has not figured out yet is infinite or finite cycle. It may be both overlapping infinitely. But again, that type of infinity doesn't suffer infinite regress like a god claim does, because off isn't forever, and on isnt forever, but going from one to the other could go on forever.

No different than drawing a line on a piece of paper, the line is finite, but the points between the ends can be an infinite number of decimal places. 

My layperson's brain sees this giant weather pattern we call the universe being no different than seasons changing. The sun having a lifespan, the planet having a life span, and even life itself having a life span. Everything breaks down, but what rot is left over, ends up moving on to something else, just like a tree dies and becomes nutrients for soil. Just like the atoms in our bodies as individual atoms were around before us and constantly get recycled. 

I would have no problem viewing the QM twitch after our heat death, being the rot that is like that dead tree leading to become nutrients for another singularity and then onto another big bang. 

What is not require for "all this" infinite or finite, is a magic man with super powers. Just like we know Thor isn't   the cause of lightening, and Poseidon isn't the cause of hurricanes.

Here is an article from the experts.

http://phys.org/news/2015-03-universe-fi...inite.html

My laypersons guess would not be either or, but both. I think off is finite, and on is finite, but going from one to the other could be infinite at the QM level. But sure, at this point we don't know.

I think aractus' 5 billion years was probably taken from the estimate of when Milky Way would exhaust its available hydrogen gas, and stop forming new stars.  

However, existing stars will continue to shine, the longest lived stars already born will go on shinning with thermal nuclear energy for 3 orders of magnitude longer than that.

So the era in the history of the universe when carbon and water based life can conceivable exist somewhat as we know it, residing on a planet and powered largely by a steady sun in the sky, has not run even 1/10 of 1% of its expected duration.

Heat death of universe will take 80 orders of magnitude longer than the life time of the longest lived stars to achieve.