Right...this will probably get moved to general, but I'm putting it here for now to try and spark an intellectual conversation with no lolcats. Also bear in mind that I generally struggle with physics as my mind will pick up something, then go off into a tangent. So I picked up Muse : The Second Law on Saturday and after listening to it a few times, I attempted to start reading up on the laws of thermal dynamics and various related bits. In short, I've got a couple of questions that are nagging me: - If energy cannot be created or destroyed, where did it come from in the first place. - When we have the 'eventual' heat death of the universe (i.e. max entropy), won't gravity as a force still exist, attracting the smallest bodies to each other, eventually converting entropy back to higher energy over the course of trillions of years.
Where did the Big Bang come from? The universe is a closed system, therefore with a limited amount of energy, but outside of it, who knows? Heat death occurs when things are so cold that even gravity does not heat things up anymore and black holes are cold. When it's spent, it's really spent. I once read that the three laws of thermodynamics can be summed up thus: You can't win; You can't break even; You can't get out of the game.
I don't think you will get a answer to that one certainly is interesting, I think one of the problems we have with there just being "nothing" is its almost impossible to imagine.
It was all there when time started (hence big bang). Where from? Some say who knows. Some say God. Interestingly enough, some state gravity as the reason why a heat death cannot possibly happen: http://www.kk.org/thetechnium/archives/2011/03/there_aint_no_h_1.php
Surely it also depends on whether or not the universe continues to expand? If everything is widely spaced, gravity won't be able to attract bodies together to create higher energy states - or am I understanding that wrongly?
Aye, that's what I thought at first. But how would temperature affect the application of gravity to the remaining mass in the universe? (My understanding is that all mass can act as a source of gravity) True, but speculating about it could be quite interesting. Also, I might learn something from the multiple theories that get thrown around about it. Had a quick skim through that link - looks pretty interesting, although will have to wait till I'm home from work to have a proper read and be able to properly digest it Nope, that makes sense at least when assuming that the universe is expanding to infinity. Failing that, there's always the theory of the big crunch I guess. But then again, what are the odds of a near infinite amount of bodies all being far enough away to not be attracted to each other via gravity. As mass increases, so does gravitational pull - i:e two bodies will pull from further afield than one. At least that makes sense in my head. It's been at least nine years since I was last in a physics class, so feel free to prove what I just wrote as incorrect.
Escape velocity can be much lower than you'd expect. Say you had an Earth sized sphere. For it to have a escape velocity of 1m/s it would weigh about 50*10^15kg. Gravity is incredibly weak.
You've gone from simple 2nd law understanding way off into cosmology here Brooxy, and it all hinges on the theories about what the Universe will eventually do - keep expanding infinitely, or reach a crunch and collapse.
We're talking cosmological constants here. If gravity had the potential to reverse expansion it would have already done so...and relativistic mass doesn't account for observation. Personally I think when protons are so widely distributed that fundamental forces no longer act upon them at the edge of the universe they become 'confused' and teleport until they have a reference point. No big bang. No big crunch. No big freeze...Just an eternal 'waterfall' of particles from the centre to the edge. (Of course I have no proof of this and I am crazy)
Energy isn't a "thing" but we can understand it better if we think of it as a "thing". All energy is, is a state change, and it is as arbitrary as time. We try to quantify it in order to understand it. So in a sense it didn't come from anywhere as it is a human creation in order to understand mathematical problems.
The Doctor: People assume that time is a strict progression of cause to effect, but *actually* from a non-linear, non-subjective viewpoint - it's more like a big ball of wibbly wobbly... time-y wimey... stuff. --'Blink' Amy: Okay. Okay. Where are we? The Doctor: Outside the Universe. Where we've never ever been. Amy: Wait, so we're in a tiny bubble universe sticking to the side of the bigger bubble universe? The Doctor: Yeah. No! But if it help, yes. --'The Doctor's Wife'
Time (the expression of energy moving or changing state) started at the big bang, we see everything through the perspective of time. The universe/energy was there before time but we just can't see or pecive it. As time passes it gets larger as there is now more time. (Think of time as the expanding bubble). So time starts off very small and expands outwards taking the "universe" with it.(big bang). The more time, the more space between parts of the universe. Repeat until at full entropy. Time stops. Universe is still there, just again no time so we can't percive it.
We don't really know where the energy came from in the first place but there are some theories. For instance the branes hypothesis is that there are many universes that are called branes that exist outside our universe at the moment of the big bang two of these branes collided and bounced off providing the energy for the big bang. Then there is the cyclic universe that expands and collapses forever, but that doesn't explain where it came from originally. The biggest problem with finding out where the energy came from is that we can't see back before the big bang. The only clues that we really have for what happened before is the differences in the cosmic microwave background radiation. These differences may be able to give us some clue as to what, if anything, happened before the big bang. Gravity would still affect everything in the universe but everything would be travelling faster than escape velocity so that no matter how long you wait gravity will never pull you back. In fact if the universe continues to expand at an ever faster rate then eventually everything would be moving away from everything else faster than the speed of light. So no matter what nothing would be able to come together again. This may actually stop things from being affected by gravity as gravity is supposed to propagate at the speed of light. (The faster than light aspect is due to the space between two objects getting bigger rather than the speeds of the particles themselves.) TL : DR: We don't know and yes it will but it wont bring things back together.
Gravity cannot pull things back together. In fact they are speeding apart at an ever faster rate. We're trying to explain this via Dark Energy. Theoretically, this is the force which is constantly trying to rip everything apart. It works at every level. It tries to push galaxies away from each other. It tries to rip galaxies, celestial bodies, molecules, atoms, even Protons and neutrons apart. Then there's dark matter, which is the stuff that aids the formation of galaxies. Both of these are extremely difficult, indeed nearly impossible the detect. As for the big bang there are several theories. One is the brane theory, as stated above. Then there are others, like the cyclic theory. As for the "original" one must remember that, outside of time+space, The laws of time and space do not apply. The same is true for the "inside" of a black hole. Therefore, Our very understanding of it crumbles. It's a paradox. There is one theory, String theory(Correct me if I am wrong), that I personally believe in. It has ALOT to do with black holes. It theorizes that every black hole's singularity pierces a hole in the fabric of time and space. It states that once outside time and space, This singularity destabilizes, and instantly expands into a big bang. This relies upon the similarities to make sense: The universe started out as an infinitely small point of energy. A black holes' singularity is the exact same thing. Due to the laws of space/time not applying, any given singularity can create any given universe. Even one from our universe could create the universe. Paradoxical, I know, but it helps to Ignore the laws, if just for a second.
All the energy/matter that exist in the universe today was there at the instant of the Big Bang, and at that instant time started. Before the Big Bang time did not exist, and thus there was nothing to cause the Big Bang to happen because what we perceive as the "normal" sequence of events in any cause-effect relationship is dependent on time. However, when we rewind the universe to the point where all matter/energy is squeezed together into the singularity that birthed the universe other principles take effect; namely quantum mechanics. Quantum mechanics is weird and severely counter-intuitive, but we are starting to understand more about how the universe works at the smallest of scales. What's really interesting about the quantum level of reality is that at that scale you do not need a cause in order to have an effect, or vise versa. Things just happen. Particles pop into existence only to pop out of existence a fraction of a second later, and this lends credence to the idea that the universe could simply have popped into existence without a preceeding cause.
That's really ****ed up -_- Any good sources where I can read about this more from a scientific and philosophical perspective?
I'm sorry I haven't been back here to check for replies for a while, but yes; there are books you can read about this subject. Personally I would recommend Stephen Hawking's books "The Grand Design" and "A Brief History of Time".
edit: sorry, I could not resist. edit2: I still have to read all of the posts, but IMHO when one of the electrons of an atom in your body has a probability of being on the other side of the universe, when 2 electrons can be quantum linked and when virtual particles appear and disappear in a vacuum then nothing is to weird for the universe. If the universe is infinite then there is the probability of an infinite number or arrangements that somehow are exactly the same as the one we are experiencing now, what i mean is that if the universe is infinite there are an inifinite number of earths that are exactly similar to our earth, even the inhabitants and what they are doing, there are an infinite number of DXR_13KEs editing their posts on a tech forum.
Speaking of which, I never really got up to speed on quantum entanglement. Is it an on-paper theory, or has it actually been demonstrated? Also want to throw in a good word for Please Explain by Isaac Asimov. Science non-fiction by a great sci-fi writer with a knack for making huge, bizarre concepts seem matter-of-fact and reasonable. Best small book I've read on the subject(s).
