From my basic understanding of popular-level physics articles and books and such, the 4 forces (Electromagnetism, Gravity, Strong and Weak Force) used to be 1 force in the early universe, then split off into the 4 forces as the universe expanded and cooled down.  I'm wondering, if the universe is continuously expanding and cooling down, could the 4 forces split off or "decay" again in the far future? Has anyone theorized about this at all? Billions of trillions of years in the future, might magnets cease to induce electrical currents, or could electrical activity cease to carry a magnetic component, or could the Weak Force break up into its individual components?
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It is generally believed that $10^{-35}$ seconds after the Big Bang, the symmetry of a GUT was broken and after $10^{-12}$ seconds the electroweak force was broken:  \begin{equation} \mathrm{SU(2)} \times \mathrm{U(1)} \rightarrow \mathrm{U(1)} \end{equation}  This symmetry breaking is a result of the universe cooling down and undergoing a phase transition. I'm aware that the temperature of the universe it about $2.7$ Kelvin, so the temperature of the universe cannot decrease much more, but I was wondering if there is a chance that another phase transition might happen again in the future?
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We already discovered the cosmic background radiation what are the 'leftovers' of electromagnetic radiation of the big bang. Probably gravitational waves of the big bang (if they exists) would be to low to measure at the moment. But according to the unified theorie all forces existed already 'together' in the beginning. So the question is can the really exist today or are gravitational waves just created after a while and only because of matter what is coming together instead of a kind of an 'explosion' like the big bang?
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I heard that a magnetic field only creates a force on a moving charge, not a stationary one. However, what if the solenoid containing the magnetic field was moving through a stationary charge. Would that create a similar force? Thanks!
4154
After reading many questions, like   and , I wonder:   Is it possible to consider the other fundamental forces too, the electroweak interaction and the strong interaction or ultimately the unification of these, to be fictitious forces like gravity in the framework of general relativity?   If we want a final unification of all fundamental forces, hasn't this feature of gravity to become a feature of the other forces as well?
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Possible Duplicate:          I love to dabble with science, I'm by no means a scolar in this field. One thing that haven't seen proven yet (maybe I missed it) is that there was only 1 singular Big Bang where it all started.   As I understand, when Hubble discovered that the universe was expanding, the conclusion was also that it was much smaller in the past. That I follow, but the theories seem to automatically agree on there being 1 Big Bang where everything started.   Couldn't there have been multiple points where matter etc 'flipped' into existence roughly around the same place and time? Is there any evidence for that? Does all the red shift for instance point to 1 spot?   Thanks for your time and knowledge in advance,  Gert-Jan
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There are several conditions that must be met in order for a force to be . One of them is that the curl of that force must be equal to zero? What is the physical intuition behind this? If you can, please explain it to me via the magnetic force fields because i have read that time-varying magnetic fields are not conservative because they do not meet that condition.I do not understand this.
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I have studied some of Einstein's Theory of General Relativity, and I understand that it states that gravity isn't a force but rather the effects of objects curving space-time. If this is true, then why are we instructed in middle school that it is a force?
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Our galaxies are speeding apart from each other and that is because of dark energy, but we don't know where it comes from right? If I'm not mistaken could dark matter have dark energy? (If they are the same thing please correct me.) Matter has gravity so could  have , so sense there is more dark matter is that why our galaxies are being pushed apart?
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This question is a more concrete reincarnation of an .  Are there mechanisms to extract energy from the cosmic rate of expansion? putting some extremely long ropes across the universe and extract work from their increase of separation?  assuming this is possible ( i don't see why it would not ), what form would take the back-reaction force? in all physics, every time you extract work from some system by some force, this system will exert a force back. Can we slow down cosmic expansion by variations of these mechanisms?
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I recently became really interested in learning about physics and cosmology, but I still know very little. Hopefully someone with more knowledge will be able to shed some light on my questions.  Here are my presumptions (please correct me if I'm mistaken):   $t_{0}$: Big Bang. The Universe expands (and thus cools) sufficiently to allow the formation of atoms. The early Universe mostly consists of Hydrogen and is not uniform in its geometry. Gravity pushes lumps of matter together until their density (temperature) is so high that nuclear fusion kicks off. The first giant stars are born. Some heavy elements are created in these stars and when they explode, sufficient temperatures are reached to form heavier elements still. All of the successive stars and planets are the product of these original stars.   My questions:   If the amount of Hydrogen is finite in the Universe and each successive generation of stars use up most of their Hydrogen, what is the theoretical maximum number of generations of stars that our Universe can support? A ballpark figure in terms of years is fine too. ;) Are there some special physical processes that occur in the Universe on a large enough scale that are able to break up heavy elements (i.e., Helium) into lighter elements (i.e., Hydrogen)? Kind of like a cosmic recycling operation. If we discount the possibility of a Big Crunch, is the Universe pretty much headed into a time when there will be no more stars and only a bunch of black holes, planets, and other debris?
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is based on the presumption that Force Lightning, like regular lightning, is composed of electricity.  I'm not sure about that.  Every written description I've seen of the phenomenon calls it &quot;dark side energy&quot; or something similar. What is Force lightning, exactly?  Is it electricity, or something else?
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When I'm rotating, I feel centrifugal force. But if I were the only one in the universe and rotating, wouldn't I just kinda be still (since I'm not rotating with respect to anything) or would there just be a force pulling me out? What if there were another person a billion miles away, this should not change anything, right?
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I have a bunch of magnets (one of those game-board thingies) given to me when I was a school-going lad over 20 years ago, and the magnets feel just as strong as it was the day it was given.   As a corollary to this question , is there a way to determine how long a permanent magnet will remain a magnet?   Addendum: Would two magnets remain a magnet for a shorter duration if they were glued in close proximity with like poles facing each other?
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Can anybody please tell me if magnetism is a conservative force or if there is a field associated with it? How to reason? One thing I know is that the work done by a magnetic force is equal to $0$.
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Ok so the universe is in constant expansion, that has been proven, right? And that means that it was smaller in the past.. But what's the smallest size we can be sure the universe has ever had?  I just want to know what's the oldest thing we are sure about.
2038
I have looked at other questions on this site (e.g. "why does space expansion affect matter") but can't find the answer I am looking for.  So here is my question: One often hears talk of space expanding when we talk about the speed of galaxies relative to ours. Why, if space is expanding, does matter not also expand? If a circle is drawn on balloon (2d plane), and the balloon expands, then the circle also expands. If matter is an object with 3 spatial dimensions, then when those 3 dimensions expand, so should the object.  If that was the case, we wouldn't see the universe as expanding at all, because we would be expanding (spatially) with it.  I have a few potential answers for this, which raise their own problems:   Fundamental particles are 'point sized' objects. They cannot expand because they do not have spatial dimension to begin with. The problem with this is that while the particles would not expand, the space between them would, leading to a point where the 3 non-gravity forces would no longer hold matter together due to distance Fundamental particles are curled up in additional dimensions a la string theory. These dimensions are not expanding. Same problems as 1, with the added problem of being a bit unsatisfying. The answer seems to be (from Marek in the previous question) that the gravitational force is so much weaker than the other forces that large (macro) objects move apart, but small (micro) objects stay together. However, this simple explanation seems to imply that expansion of space is a 'force' that can be overcome by a greater one. That doesn't sound right to me.
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This question is inspired by (or a follow-up to) the threads  and   The  (CνB) consists of the "primordial" neutrinos from the time when the universe had cooled/expanded enough for the neutrinos to "decouple" and become free. This of course is similar to the cosmic microwave background except that photons decoupled at a much later time (age $1.2\cdot 10^{13}$ s) than neutrinos (age $1$ s).  My question is, what would we expect the CνB to look like today, given that we know that neutrinos possess mass. According to the linked threads, the neutrinos would have become non-relativistic today because of the great expansion of space since the time when the universe was only one second old.  So will the relic neutrinos from CνB be captured gravitationally by galaxies and stars and similar objects, in a way that today these neutrinos are orbiting galaxy centers, stars etc.? I imagine this is like how most cold/slow hadronic matter (like dust or isolated hydrogen atoms or whatever) will be gravitationally bound to galaxies, stars etc.  Because if that is the case, this neutrino "background" will no longer be have a "background" appearance.  So what to expect: Is the neutrino background still quite isotropic and homogenous and "background-like", maybe even with a temperature associated to it? Or are those particles now captured by all sorts of objects, and no longer constituting a "background" of cold/slow particles?  If one assumes a particular rest mass for each neutrino, say $0.1$ eV, maybe it is even possible to answer this quantitatively?