Here’s a shocker: there are two meanings for the word universe. One is “the set of all that exists” while the other is “the set of all locations”. The former has identity and is finite, while the latter has no identity and is infinite.
There is not necessarily anything in between air molecules and nothing composes deep space. Not energy and not waves and not ether.
If nothing is in deep space then how could any two things in deep space ever have distance between them? SOMETHING would have to seperate them (think about it: is this logical: “there is nothing in between these two things”?).
By universe I mean existence.
Energy is in deep space, how do you think photons get from Alpha Centauri to here?
Two points: see the thread in Science , and see the Michelson-Morley experiment (try Wikipedia).
woo.
New to the forum, but not to science.
To reiterate- A closed system is one in which nothing (not just energy) can enter or exit. It has a boundary, but either nothing can cross that boundary, or you luck out and nothing does for the period of time you care about- either way it’s closed.
This is a big deal cause newtonian physics seems not to be able to cope with new forces or energies entering the systems they’re looking at. Newtonian predictions only work in closed systems… kinda a big deal.
The idea that the universe is closed comes from the simple idea that… for something to enter or exit the system, there has to be somewhere else for it to enter from or exit to… and.. if the universe is by definition the whole of existence… where could it then go or come from?
This has come up in my classes recently cause of the debate of… well… if newtonian predictions work so well in a closed system, and the universe is one… by knowing everything that can be known in the universe- every particle and it’s current movement- couldn’t one predict everything that will ever happen in this great machine we call a universe, in which we merely happen to be cogs (who happen to mistakenly beleive we’re self-aware and in control of our own actions… if after all, we are just the sum of our parts- we’re made of the particles in question, and I can predict everything you ever do based on my knowledge of everything)
Problem is… physics has found that it does… kind of… happen anyway. It bothers us a lot. Literally everywhere throughout the known universe, every moment, matter seems to spontaneously pop up… a particle and antiparticle shoot out of nothingness, reducing the energy in the local area slightly, and (usually) recombining, exploding, dissappearing, and putting the energy back where it’s supposed to be. This on it’s own throws the closed system idea into question, and is the latest incarnation of zero-point energy… cause it all happens so quickly that the ‘law of conservation of matter and energy’ seem to go hang for a bit… it’s almost as if it happens so quickly that it’s over before the universe notices and gets a chance to stop it (thank you douglas adams).
As if that’s not enough, the (usually) is a problem too. It doesn’t always work that way. The black hole thing is what’s causing the problem… black holes are considered a kind of negative energy, if you will, and if you pour enough positive energy into them, they tend to explode (this also happens if they’re too small and you pour anything into them… even the big ones eventually go this way, it just takes a long time- however long until the matter going in outweighs the initial negative energy of the thing, which is based on it’s size) *NOTE- this is a simplification… I couldn’t explain it in under 50 pages otherwise- so don’t go quoting me to anyone who really knows their physics already*… when these particles pop up around a black hole, if one gets sucked in, but one gets away, then the one getting sucked in changes the black-hole’s mass and energy just like anything else going in.. it reduces the negative energy of the black hole like anything else… just the right amount of negative energy to level the universe off to where it was before it and it’s brother ever formed in the first place.
Problem is… it’s brother is still out there. And it’s new. And it came from… nowhere? The first complaint was something along the lines of the universe blinking and these things coming out to play while it’s eyes are closed… this… is soooo much worse… cause it’s still there when the the universe turns around to look-see.
not a closed system after all?
Oh, and on top of that, so much of physics now is probability- nothing can be absolutely known, so newtonian physics is out the door anyway, cause you have a problem measuring in the first place.
OH- and if it were a closed system… entropy would work differently. In an open system, the only way to reduce entropy is to expend energy specifically to do so, expend no energy towards this, and entropy gets worse. Entropy is the measuring stick for disorder in a system, and according to thermodynamics, entropy in a closed system is always constant (I’m talking about the total entropy of the system, not of a small chunk of it). So if the universe is a closed system, then the dirtier your room gets (clutter = more entropy), the cleaner someone else’s has to get somewhere else (on it’s own!)… hrm… could use to look into this…
The thermodynamics law is that the entropy of a closed system never decreaes. Rooms can certainly get dirtier on their own, but if you want to clean one room up, you need to move all the dirt into another room.
… by knowing everything that can be known in the universe- every particle and it’s current movement- couldn’t one predict everything that will ever happen in this great machine we call a universe, in which we merely happen to be cogs
The answer is, of course, that we are not cogs, but volitional beings. If we knew all of the initial conditions governing the physical determinstic behavior of non-volitional entities ( a somewhat daunting assumption), and if we knew all of the laws of physics governing that deterministic behavior, then indeed we could predict all, moment to moment, but only if volitional beings did not exist. A bit of a quandry there though, since the very act of such a prediction implies the existence of a volitional being, and the existence of a volitional being obliterates prediction for all actions and processes. We are not mere puppets being moved about on the stage of the universe, but rather we change the storyline, change the words which are uttered, and choose to direct the scene as we see fit (if you can withstand such a Hollywood metaphore!).
That we are volitonal beings is not something to be questioned. You can take your own word on that.
Problem is… physics has found that it does… kind of… happen anyway. It bothers us a lot. Literally everywhere throughout the known universe, every moment, matter seems to spontaneously pop up
I do not know what level you are at in your studies, but I suspect you have not yet studied quantum field theory. Ask one of your professors to explain virtual particles in the context of quantum electrodynamics (QED). Virtual particles are mathematical abstractions, not physical existents in QED. They are a sheer artifice of perturbation theory. QED is an Abelian gauge theory; we start with the QED Lagrangian and we model, for instance, a massless vector particle as a gauge field. The whole artifice is built upon renormalizable quantum field theory with a boost from perturbation theory. Virtual particles are states, e.g., just an internal line on a Feynman diagram. They are, in effect, mathematical abstractions.
The black hole thing is what’s causing the problem… *NOTE- this is a simplification… I couldn’t explain it in under 50 pages otherwise- so don’t go quoting me to anyone who really knows their physics already.
Problem is, as Wolfgang Pauli liked to say, it’s not even wrong. Until you study quantum field theory and general relativity in depth, you will benefit from, and most likely enjoy, a wonderful little book by GR expert Robert M. Wald: “Quantum Field Theory in Curved Spacetime and Black Hole Thermodynamics,” _The University of Chicago Press_, 1994. Most good technical books on these subjects are written, at least, on an advanced graduate level. But the level of this book by Wald is such that a bright undegraduate can wade through it and get a really decent grasp of more esoteric areas as the Unruh effect and Hawking radiation. The author is the same Robert Wald whose “General Relativity” text is a staple nowadays in most advanced courses in general relativity. Wald is brilliant, and very clear writer.
Oh, and on top of that, so much of physics now is probability- nothing can be absolutely known, so newtonian physics is out the door anyway, cause you have a problem measuring in the first place.
You could benefit greatly by supplementing your physics studies with Objectivist epistemology. Probability is an epistemological concept, one which refers to our assessment of what we think we know. The physical world is deterministic, and any lack of knowledge on our part is not due to a supposed inherent randomness in Nature, but rather to the fact that we are not omniscient and, at any given time, there are conditions and processes about which we do not know or understand.
You seem like a bright young student of physics, and you seem to like the subject you are studying. Believe me, I can identify with that. I have a profound love for physics and its history, and I must say that a proper philosophical base has been a wonderful asset over the years in all of my studies. I would suggest concentrating on the technical aspects of physics in the courses you take, and learning a good philosophy like Objectivism to help you evaluate and separate out the good and the bad parts of whatever you learn. Just meant as a helpful suggestion.
This probably ought to be under a separate thread, but here I am so I’ll ask.
First, let me say that I am totally ignorant of physics. I do, however, find the subject – and most physicists – fascinating and make it a point to watch programs aimed at the interested layman. There are propositions made that bother me because I seem to have a different take on the meaning of certain terms used and I think that sometimes it is because these terms are used in a particular, scientific way that I don’t know.
For example, the term “infinity” has been used several times in this thread. I’ve heard physicists use this term as though it were something that actually existed in reality. I come to this term from philosophy, however. In arguing against Zeno’s paradoxes, for instance, Aristotle says that just because one can divide space or time in one’s mind doesn’t mean that there is actually anything infinity large or small, or infinitly long in duration, etc. This is the difference between treating something epistemologically and doing so metaphysically. So, my question: How, in physics, is the concept of infinity used? I understand how it is used mathematically, but do physicists use the term to refer to an actual infinity?
Next, I often wonder about statements about chaos, which seem to mean that we can never know about certain aspects of entities. If an entity has a nature and can only act within that nature, whence chaos? When I think of chaos, I think of unpredictability. It is easy to see this when one considers the actions of humans, which certainly can be unpredictable and, in turn, chaotic. When physicists speak of entities in general, with all of their properties and attributes, do they mean that the stuff of the universe behaves in unpredictable ways (assuming that we understand everything about the entity)? If so, how does this square with the law of identity and the law of cause and effect?
In this thread, arguments have been given for a closed universe – which arguments I understand to a point and agree with from a strictly philosophic point of view. There are those who talk about many universes, however. My question: If the term “universe” means everything that exists, and the universe is a closed system, how can there be more than one? Is this an instance of a term being used in a special way, or are there physicists out there who think that there can be more than one “everything that exists?”
I’ll stop here. I have dozens of such questions, but I’m never in a position to ask anyone who could tell me. Since the terms I’m asking about have been used in this thread, I’m hoping that those of you who are knowledgable will lend a hand (and forgive the imposition!).
Oh, and though I do understand words of more than one syllable, please remember that I AM ignorant of the subject!
From… happysteak?
Here’s something fun we came up for the questions: “What’s in between air molecules and what composes deep space?”: energy, that’s right, waves! (NOT ether, for Allah’s sake)
The question is - waves of what?
A wave is not an entity, but a kind of movement OF an entity. See: air waves, sea waves, sound waves (different kind of air waves).
As I read in a book of Acoustics, there are two kinds of waves: waves who move across a still medium (like at sea), and waves that move with a moving medium (like sound waves).
A wave cannot be a primary - only a property of an entity.
If an entity has a nature and can only act within that nature, whence chaos?
I’m not sure, but I think chaotic means that a slight difference in cause has a very large difference in effect. If you know, based on an entity’s current properties, how it will act, in most cases you will be able to approximate how the entity acts given a slight change in its properties. With chaotic systems, however, that kind of approximation breaks down quickly. It’s not that the effects are unpredictable, but that they are very difficult to approximate.
“oldsalt” asks a number of physics-related questions. (Best to be moved to the Science section?)
There is one issue common to all of the questions, a basis which should be understood before dealing with each. It is important to discern (at least) three different categories:
Popularizations of physics – These tend to be a more fantastical perspective on physics, focusing on what seems strange, bizarre, counterintuitive, or contradictory to what the average reader might expect.
Theorists – A relatively small group of theoretical physicists who, for the most part, lack a good epistemological grounding and generally have an alice-in-wonderland sense of metaphysics. These are the few who typically fuel the popularizers mentioned above.
Actual physicists – These people represent the overwhelming majority of real physicists. In their work these are profoundly rational people who focus on facts, physicists whose work of necessity demands a proper epistemology and contact with reality. If you push these guys on the weekend to talk about broader-ranging theoretical principles of physics, many will repeat some of the verbiage which was invented by the theorists in category 2. However, most leave such notions at the doorstep when they enter their lab.
So, unless you work in the field and have regular contact with the actual people doing physics – if you get your view of physics from various interpreters – you might think that modern physicists all revel in singularities and trade infinities the way kids trade baseball cards. Not so.
As to infinity: Mathematics is a fundamental tool of physics, and in some regard it is a language in which physics can be expressed. Most physicists are well-grounded in mathematics, even though not as concerned with foundational issues as are many mathematicians. Infinity as a concept of method is used throughout mathematical physics, and is routinely accepted as such. Amongst popularizers and theorists you will often hear of infinities as if they had a metaphysical existence, mostly mathematical singularities (places in the mathematics where operations become undefined or properties are unconstrained) which are then given some sense of physical existence. But, those who are actually doing the physics do not spend their time looking for places where reality is undefined or where properties of entities increase or decrease without bound. It is typically categories 1 and 2 who are guilty of such nonsense, not the real physicsts in category 3.
As to chaos: This concept is often conflated with the notion of metaphysical randomness by the popularizers of physics. The root of chaos theory lies in the fact that, in some cases, extremely small changes in the starting conditions for some physical process can lead to extremely large differences in the result. It is not that there exists some metaphysical randomness in some physical process, but rather that the dynamics are such that our inability to specify the initial conditions with infinite precision leads to difficulty in predicting the outcome of what is, nonetheless, a physically determinstic process. Atmospheric disturbances, turbulent flow in liquids, and some aspects of orbital dynamics are areas where this sort of problem is studied.
As to the universe: This term is bandied about by popularizers and theorists, sometimes so much that it is difficult to nail down a precise meaning in every case. Generally speaking, in cosmology the Big Bang theory literally means that the space of the universe is being created as there is expansion. But there are other cosmologies in which there are multiple universes, with a single universe being that which we are capable of knowing. The term universe is used in so many different ways, is stretched and pulled so far and in so many directions, that, in my view, it is best to just try to understand the notion the theorist is advocating, and do not attempt to connect to a concept of universe at all. With that said, most actual phsyicsts think of the universe as all of that which exists, just as we Objectivists use the term.
May I suggest that any further questions be put in a separate thread in the Science section, mainly so that those interested in the subject will stand a better chance of seeing it there.
Shattered Rose:
The next time you encounter this statement:
Oh, and on top of that, so much of physics now is probability- nothing can be absolutely known_,_ so newtonian physics is out the door anyway, cause you have a problem measuring in the first place.
Ask the speaker if they know this absolutely. It is not likely to change the speaker’s mind, but it may encourage others not to swallow this stuff without question.
Good luck with your studies!
Dear Mr. Speicher:
Thank you for answering my questions. I do know that popularizers of physics don’t always get it right, which is why I used to attend lectures given to the general public by actual, practicing physicists, from whom I’ve learned a lot about certain basic theories. The biggest problem comes from science documentaries, where some theorists seem to go off the deep end.
I’ll direct any further questions to the Science thread. My excitment over finding someone on this forum who is knowledgable about this subject was the cause of my interruption of the discussion. Mia culpa and apologies to the others.
Janet