Farsight

I'm afraid your hunch is wrong. There is no gravity in a homogeneous universe, but it still expands. Gravity didn't stop the early universe from expanding, it merely increases inhomogeneity within that expanding universe. Denser regions get denser, matter is attracted to matter, be it dust or galaxies. But the space between the matter continues to expand.

Radioactive decay rates aren't necessarily constant. I imagine they vary with gravitational time dilation, but that apart, see the wiki article for changing decay rates and have a browse on decay+neutrino+seasonal to look further than CMBR photons. Note that most of the "particle zoo" particles with unambiguous mass aren't stable. Only the electron, the proton, and their antiparticles are stable. A charged pion lasts about a nanosecond, a muon lasts about a microsecond, and a free neutron lasts about 15 minutes. As far as I know you don't need to add any energy for these decays to occur. The neutron is usually stable inside an atom, but not always. Some half-lifes are so very short that they surely have to be associated with nuclear structure rather than the addition of energy or disruption by ambient photons or neutrinos.

Huh. I know about this stuff, it’s no big deal, and no sparticles are necessary. See http://physicsworld.com/cws/article/news/43128 for another article. Protons don’t really have a size. Measuring their size is like measuring the diameter of a "whirlpool", with an arbitrary cutoff at some charge density. The Lamb shift is where another particle with spin angular momentum changes its path. Use one that’s more massive, and the path is different. All this everything is wrong business is just attention-seeking sensationalism.

See the stress and pressure page by Philip Candela. When we assign directionality to pressure we call it stress. Both stress and pressure are measured in Pascals. The difference between them is merely one of definition.

Antigravity. A gyroscope doesn't fall over, he was trying to make something that doesn't fall down.

Interesting, Abhilash. I'd say yes, there should be a PQRS potential. But note that whatever I expect, the experimental results are more important, and there are some issues with your opening well-established facts: 1) Current is the rate of flow of charge – any charge, not just the flow of electrons. Yes, a stream of copper ions carries a current, but don't forget displacement current. This is not a flow of charge. 2) This flow of charge produces a magnetic field around itself/conductor. Yes, we observe a magnetic field around the current in the wire, but this is merely one "aspect" of the electromagnetic field. It becomes observable in this situation, but it isn't actually created. In similar vein you will detect a magnetic field if you moved past an electron. Your motion altered your observation of the electromagnetic field, it didn't create a new field. 3) Classical physics is purely deterministic and that definite causes should have definite results. Agreed. But see Jefimenko's equations and note this: "There is a widespread interpretation of Maxwell's equations indicating that time variable electric and magnetic fields can cause each other. This is often used as part of an explanation of the formation of electromagnetic waves. However, Jefimenko's equations show otherwise. [3] Jefimenko says, "...neither Maxwell's equations nor their solutions indicate an existence of causal links between electric and magnetic fields. Therefore, we must conclude that an electromagnetic field is a dual entity always having an electric and a magnetic component simultaneously created by their common sources: time-variable electric charges and currents." You might be interested in Vector potential, electromagnetic induction and ‘physical meaning’ by G Giuliani where the abstract says this: "A forgotten experiment by Andre Blondel (1914) proves, as held on the basis of theoretical arguments in a previous paper, that the time variation of the magnetic flux is not the cause of the induced emf; the physical agent is instead the vector potential through the term −∂ A/∂t (when the induced circuit is at rest). The ‘good electromagnetic potentials’ are determined by the Lorenz condition and retarded formulae. Other pairs of potentials derived through appropriate gauge functions are only mathematical devices for calculating the fields; they are not physically related to the sources. The physical meaning of a theoretical term relies, primarily, on theoretical grounds; a theoretical term has a physical meaning if it cannot be withdrawn without reducing the predictive power of a theory or, in a weaker sense, if it cannot be withdrawn without reducing the descriptive proficiency of a theory." Another very interesting paper is The Refractive Index in Electron Optics and the Principles of Dynamics by Ehrenberg and Siday in 1948. This classical paper predicted what is now termed the Aharonov-Bohm effect.

MyUncle: relativity is actually pretty simple, but when people like me try to give you the simple explanation, the other guys don't like it. By the way, I'm something of an Einstein fan, but yes, I'd say he is somewhat "pumped up". thetree: Einstein didn't work on the Manhattan project. He sent a letter to the president, see http://hypertextbook.com/eworld/einstein.shtml. He wasn't quite trusted.

I don't know if it's possible. But I was talking to a guy about something like this a couple of weeks ago. He was suggesting that some of the matter in the accretion disk is converted into space, which essentially "blows out" in a polar jet. He was offering this as an explanation of superluminal jets. In essence new space is being created, and whilst within that space motion is subluminal, the net effect is superluminal as per the expansion of the universe. I thought it was an interesting idea, and wondered how one might move from speculation to test.

One way is something like this: As you approach a black hole event horizon, you suffer more and more time dilation, which tends to infinity as far as outside observers are concerned. Events occuring in your "proper time" take forever to happen, and never actually happen. The boundary of the finite universe is a form of event horizon, in that there's no space beyond it for light/particles/etc to travel through. Hence there are no events. We can't actually reach this boundary because the universe is expanding faster than light. But imagine for a moment that the universe wasn't expanding, and you could approach the boundary. You might "bounce back" off it, or you might push it out like a thin skin of rubber, or indeed push it out with no resistance at all. But I favour never actually reaching it because every step closer takes a greater and greater duration. It would be like a black hole only inside out. Another way to conceptualize this is to imagine you're swimming through a ball of jelly that gets stiffer and stiffer as you approach the edge. And of course, you're made of jelly.

It's just how you "feel" an electromagnetic field when there's relative motion involved. Re the above reference to the near field, the reality underlying the virtual photons of QED is thought to be the evanescent wave. See http://en.wikipedia.org/wiki/Evanescent_wave. Think in terms of a pressure-gradient or "standing wave" for this, as opposed to "propagating waves" for real photons.

And you've been sitting at your desk all that time. All that happened is the world turned, and things moved. The little cogs inside your clock turned. And that little calender display on your clock turned too. It went click, and then it showed a 7 instead of a 6. May 7th was never literally "in" the future, and you didn't travel to it. I'm sorry Swanson, but the scientific evidence is on my side, not yours. Time travel really is science fiction. So in placing this thread in speculations, you're upholding speculative pseudoscience quackery, not rational scientific discussion.

No, there is no actual negative energy. One can entertain a relative negative, but not an absolute negative. For example a gravitational field is often mentioned when discussing negative energy, but if you could measure the energy density of any thing within a gravitational field, including the spatial vacuum energy at any point within a gravitational field, you'd find the energy density was positive at all locations. I'm afraid the tachyon is a mathematical speculation based upon a non-real solution with no foundation in fact, and totally devoid of supporting scientific evidence. To illustrate what I mean by this, consider a simpler example. Consider a square carpet with an area of sixteen square metres. It will measure 4 metres by 4 metres. However since there is another solution to √16, you might speculate the the carpet could measure -4 metres by -4 metres. This however is a non-real solution. There is no such thing as a negative length. IMHO the tachyon is in a similar class.

No. It's all pseudoscience hype. Sorry.

It's just publicity, guys, intended to attract your attention, with a little wormhole woo thrown in for good measure.

It's not a matter of belief, Swanson. It's a matter of scientific evidence, and this is a science forum. So show me the scientific evidence that supports your assertion that "we are already traveling into the future". If you cannot, and instead must rely upon "moderation" to defend your stance, then this discussion is not scientific, and instead is fruitless.

Mod note: This is in reply to post #1; these two posts were moved from another thread You're in good company. You'll be aware of Einstein's Leyden Address, which is entitled Ether and the theory of relativity. Apologies if this is teaching you to suck eggs, but space isn't nothing. It has its vacuum energy, and it sustains fields and waves. Vacuum impedance is a combination of permittivity and permeability: [math]Z_0 = \sqrt{\frac{\mu_0}{\varepsilon_0}}[/math] As is the speed of light: [math]c = \sqrt{\frac{1}{\varepsilon_0 \mu_0}}[/math] If you go back to Maxwell's On Physical Lines of Force, and in particular page 86, you can see his reference to a screw mechanism. A screw features a twist, which results in turn. One can view permittivity as "twistability" and permeability as a reciprocal of "turnability". They aren't the same as stiffness and density in mechanics, but you can see some similarity with the expression for shear-wave velocity: [math]v = \sqrt{\frac{G}{p}}[/math] In this interpretation vacuum impedance is essentially the strength of space. I don't know how else to describe it. Ordinary electrical impedance is resistance to alternating current, and it isn't much different to vacuum impedance, because alternating current is what a light wave is. The typical sinusoidal waveform shows a positive electromagnetic field variation followed by a negative electromagnetic field variation: There's no charged particle shuttling back and forth, so it isn't alternating current as people usually think of it. But the field varies, so there's current of some kind in there. It's an alternating displacement current, going this way ↑ then that way ↓ as the photon goes this way →. And it's a real displacement. For a photon we say E=hf where h is Planck's constant of action. Action has the dimensionality of energy multiplied by time, and also momentum multiplied by distance. Take a look at any picture of the electromagnetic spectrum and the depicted amplitude is always the same: IMHO what you're seeing in that common amplitude, is the common displacement that underlies Planck's constant. Electron models featuring a spin 1/2 double rotation suggest it's the electron Compton wavelength divided by 2π, or 3.86 x 10ˉ¹³ metres. I don't know why all photons share this feature, and indeed there are some issues with ultra-high-energy photons. But it's what Einstein got his Nobel prize for, see On a Heuristic Point of View Concerning the Production and Transformation of Light. And that was Einstein in on the ground floor of quantum mechanics. Merged post follows: Consecutive posts mergedSwanson, this is no idle speculation, and nor is it some new theory. Check out what Einstein said back in 1920:

Whoa, guys. Time travel is science fiction. It's pseudoscience. I'm afraid you can't even travel forwards in time. People say things like "we all travel forward in time at one second per second". But it's just a figure of speech. This travel is notional, it isn't travel in any real sense. There's no motion through time, none whatsoever. Because time is a cumulative measure of motion through space. Look inside a mechanical clock, and you don't see time flowing. You see cogs and sprockets whirring. Because clocks clock up motion. Every measure of time employs motion, be it the motion of the earth, the motion of a pendulum, the motion of a crystal, or the motion of light. It always comes back to motion, and that motion is motion through space. That's the only "travelling" that's taking place. We don't "travel" forward in time, and we'd need negative motion to "travel" backwards in time. And there is no such thing as negative motion. Motion is motion. Backwards motion is still motion. Ever heard of a stasis box? It's science-fiction too, but it's useful to demonstrate something: get in the box, and the "stasis field" prevents all motion, even at the atomic level. So you can't move, your heart doesn't beat, and you can't even think. When I open the box five hundred years later, to you it's like I opened the box as soon as you got in. You "travelled" to the future by not moving at all. Instead everything else did, and again, all that motion, be it the motion of planets or people or atoms or light, is through space.

Whoa, guys. Time travel is science fiction. It's pseudoscience. I'm afraid you can't even travel forwards in time. People say things like "we all travel forward in time at one second per second". But it's just a figure of speech. This travel is notional, it isn't travel in any real sense. There's no motion through time, none whatsoever. Because time is a cumulative measure of motion through space. Look inside a mechanical clock, and you don't see time flowing. You see cogs and sprockets whirring. Because clocks clock up motion. Every measure of time employs motion, be it the motion of the earth, the motion of a pendulum, the motion of a crystal, or the motion of light. It always comes back to motion, and that motion is motion through space. That's the only "travelling" that's taking place. We don't "travel" forward in time, and we'd need negative motion to "travel" backwards in time. And there is no such thing as negative motion. Motion is motion. Backwards motion is still motion. Ever heard of a stasis box? It's science-fiction too, but it's useful to demonstrate something: get in the box, and the "stasis field" prevents all motion, even at the atomic level. So you can't move, your heart doesn't beat, and you can't even think. When I open the box five hundred years later, to you it's like I opened the box as soon as you got in. You "travelled" to the future by not moving at all. Instead everything else did, and again, all that motion, be it the motion of planets or people or atoms or light, is through space.

Photons always travel at 299,792,458 m/s because we define the second and the metre using the local motion of light. See the NIST fountain clock for this, wherein we count 9,192,631,770 incoming microwave peaks and then say a second has elapsed. Hence the frequency is 9,192,631,770 Hertz by definition, regardless of time dilation. The metre doesn't change because the slower light and the larger second cancel each other out. This is why the locally measured speed of light is always the same. The difference is there's no action at a distance. The earth doesn't pull a photon towards it, it "conditions" the surrounding space so that it's inhomogeneous, and the photon then moves in a curvilinear fashion. Hence it veers. See Einstein's 1920 Leyden address re inhomogeneous space. No, the motion is curvilinear. It's curved, and we can see that it's curved. See the Foundation of the General Theory of Relativity for curvilinear motion. We call this curved spacetime, and we talk of geodesics, but those lines are curved, not straight. Those sentences are not wrong. You've got an inhomogeneous region of space, and a photon moving out away from it. There are no other particles. There is no mechanism by which the photon loses energy. The initial photon energy is the same as the final photon energy. The measured difference is due to the change in the environment. When you're time dilated along with your clocks, the photon frequency appears to be high. Move to a higher altitude where you're not, and the frequency looks lower. Newton mechanics has been superseded by general relativity. The climbing photon doesn't lose energy, and the descending photon doesn't gain energy. In similar fashion the gravitational potential energy of a body at altitude is in the body. As it falls, the body loses this potential energy and acquires kinetic energy instead. But the sum total of kinetic+potential energy of that body doesn't increase. If it did, the gravity of a collapsing spherical shell would increase, because energy causes gravity. It doesn't increase. There is no additional energy added. Conservation of energy applies. The "force" of gravity does not add energy to the falling body.

No. It slows down when it approaches the black hole. Of course, you can't measure this locally, but the coordinate speed as measured by a distant observer reduces. Gravity isn't actually a "pull". Yes, the path of a photon is affected by the gravity of a black hole, and a photon can spiral in, but it's better to think of it as a "veer". The black hole alters the space around it so that the photon doesn't travel straight any more. It isn't a constant medium. If it was, a passing photon would go straight as a die and would shoot right on past the black hole. Merged post follows: Consecutive posts merged A photon escaping a black hole doesn't actually lose any energy. Conservation of energy applies. The frequency doesn't actually change. Imagine you've got some emitter, and you can measure frequency down near a black hole, and then again way up in space. You'd measure the frequency to be different, but it wasn't the photons that changed. It was you and your measuring devices. You were time dilated down near the black hole, so you measured the frequency as high. Up in space you aren't, so you measure the frequency as lower. So the light looks like it's been redshifted and has lost energy climbing out of the gravitational field, but it hasn't.

It's a hypothesis, and there's no evidence for it. Don't "believe" in things for which there's no evidence. It's like anything can happen. It's not scientific. It's speculation riding a hypothesis on top of a wild idea. It just isn't science. The eleventh dimension is another unsupported hypothesis. No. Sorry. You can't travel through time because time is a measure of motion. Clocks clock up motion, the second is defined by the motion of light. We've got freedom of motion through space, but not time.

Sorry not to have responded sooner. This gets quite interesting. An electron's electric field comprises energy, so there's a mass equivalence, so there's "stuff" in the surrounding space. When you look at the Aharanov-Bohm experiment, there's no detectable electromagnetic field outside the solenoid, but there's electromagnetic potential there such that the interference pattern is deflected when you turn the solenoid on. So there's something there. But it's just empty space. Then when you look at real "empty space", it has vacuum energy. Take a block of space and call it a system, and the energy content implies a mass equivalence, so we're back to "stuff" again, even though there's no "stuff" there. I think I do. If you take a region of empty space, there's a uniform energy density. If you stick a planet in the middle then mask it off and just look at the space, the energy density isn't uniform any more. The energy density is higher near the planet, and reduces with distance. You've added energy to the space, and this is the energy of the gravitational field. A non-uniform energy density causes gravity, so this causes gravity too. Sounds good to me. After all, electromagnetic radiation involves a non-uniform energy density moving from a to b. Noted. I was rather suggesting it isn't. Again sounds good. For an analogy, imagine a cube of jelly marked out with lattice lines. Insert a hypodermic needle into the middle, and inject more jelly. The lattice lines around this area are now curved. However this represents curved space, not curved spacetime, and this is a snapshot of a photon. No problem with that. This I can't see. Einstein talks about curvilinear motion being the result of inhomogeneous space. That curvilinear motion marks out curved spacetime, so I just can't see how we can have curvature and homogeneity. Merged post follows: Consecutive posts merged It's generally not done to plug your own work, and people can be hostile on forums like this, but yes, there is a final version. I'll PM you. And yes, I do think it's correct. There's a couple of little things I could have said better, like I talk about gravity as a "negative tension gradient" rather than a "pressure gradient" or a "stress-energy density gradient", and there's a typo that messes up the distinction between a tidal gradient and the gμv gradient. But it's been a year now, and it still holds up. Indeed, like I said, it seems to be getting verified, and I like to think that more professionals are thinking along these lines. Having said that, I imagine there will turn out to be something wrong in there, because nothing is ever perfect. And it is only an outline sketch, so it definitely isn't perfect.

Thanks Andrew. I'm pushed for time now and tomorrow, but will get back to you. I finished it last year, yourdadonapogostick. This is just another piece of verification.

The simple way out of this is to remember E=mc² and think of "rest mass" as "rest energy". How much of the photon energy is at rest? None of it. And you can't make a photon go slower or faster like a canonball, so mass doesn't apply. Note though that this rest energy doesn't have to be actually at rest, just not moving in aggregate with respect to you. For example it can be a photon bouncing back and forth inside a mirrored box. The photon is still moving at c, and whilst it isn't at rest, in aggregate it isn't going anywhere. Hence it increases the mass of the box+photon system.