As far as I can tell, you do not even read your own posts. You keep calling extrapolations observations and you keep calling things that can't possibly happen things that happen.
The Speed of Light is Not Constant
- Thread starter Farsight
- Start date
PhysBang
I taught physics for over 30 years and not one thing I have posted is not in sync with what I taught, if I am speculating I always say I am speculating. I am not perfect, I do not know everything, but I do not know nothing about this particular subject. Now what do you have a problem with?
Grumpy
I taught physics for over 30 years and not one thing I have posted is not in sync with what I taught, if I am speculating I always say I am speculating. I am not perfect, I do not know everything, but I do not know nothing about this particular subject. Now what do you have a problem with?
Grumpy
paddoboy
http://hyperphysics.phy-astr.gsu.edu/hbase/relativ/muon.html
Excellent post, now that is what I was saying, exactly(with math!). And as Trippy posted, that is exactly what we were discussing. Despite what some think, we're not making this stuff up, that is what Relativity says is happening, where in Newton's world it was a complete mystery. I am as capable as anyone else of making mistakes or getting something wrong. I still have trouble accepting that two bodies near lightspeed approaching each other STILL see light coming from the other AT lightspeed, but I know it to be an observed fact. It's not intuitive.
A point that may help understand. A photon is not a particle like those of mass, it is really only a wriggle in the electromagnetic field that is a part of spacetime, and all such wriggles travel ONLY at c through spacetime. The more energy poured into their creation/emission the shorter the wavelength(more wriggles per unit length). A little snippet of phonograph grove fluctuation, frozen at the moment of it's emission and traveling in spacetime at c. That little snippet of fluctuation is turned back into the energy that created it by the mechanisms in the particle of matter that absorbs it. The energy does not exist in transit, so the photon has no mass or gravity, it travels at lightspeed so it experiences no time and both it's own length and the length of the dimension it is traversing are of zero length. To themselves they are a hole in spacetime that the two surfaces can transfer energy directly through(it could be said that they touch surfaces through that hole). In fact, they look a lot like the wormholes that physicists are always talking about. But this view of the photon is only true in the frame of the photon. To us in the non-relativistic Universe we see them as frozen packets of a certain wavelength traversing spacetime at c(a Universal speed limit). Photons do not accelerate, they do not decelerate, they carry no energy in themselves, but the energy required to make them is recreated in the particle that absorbs them. As weird as this all seems, it seems to be true to the limits of our ability to understand.
Grumpy
http://hyperphysics.phy-astr.gsu.edu/hbase/relativ/muon.html
Excellent post, now that is what I was saying, exactly(with math!). And as Trippy posted, that is exactly what we were discussing. Despite what some think, we're not making this stuff up, that is what Relativity says is happening, where in Newton's world it was a complete mystery. I am as capable as anyone else of making mistakes or getting something wrong. I still have trouble accepting that two bodies near lightspeed approaching each other STILL see light coming from the other AT lightspeed, but I know it to be an observed fact. It's not intuitive.
A point that may help understand. A photon is not a particle like those of mass, it is really only a wriggle in the electromagnetic field that is a part of spacetime, and all such wriggles travel ONLY at c through spacetime. The more energy poured into their creation/emission the shorter the wavelength(more wriggles per unit length). A little snippet of phonograph grove fluctuation, frozen at the moment of it's emission and traveling in spacetime at c. That little snippet of fluctuation is turned back into the energy that created it by the mechanisms in the particle of matter that absorbs it. The energy does not exist in transit, so the photon has no mass or gravity, it travels at lightspeed so it experiences no time and both it's own length and the length of the dimension it is traversing are of zero length. To themselves they are a hole in spacetime that the two surfaces can transfer energy directly through(it could be said that they touch surfaces through that hole). In fact, they look a lot like the wormholes that physicists are always talking about. But this view of the photon is only true in the frame of the photon. To us in the non-relativistic Universe we see them as frozen packets of a certain wavelength traversing spacetime at c(a Universal speed limit). Photons do not accelerate, they do not decelerate, they carry no energy in themselves, but the energy required to make them is recreated in the particle that absorbs them. As weird as this all seems, it seems to be true to the limits of our ability to understand.
Grumpy
A) "Yet we have the observed fact that the more matter and energy in local spacetime the slower time goes(dilation), to the point that time stops at both the Event Horizon of a Black Hole"
No observation of the event horizon of a black hole. Time stopping at the horizon is an effect of coordinate choice, not physics.
B) "and at lightspeed"
No observation of anything reaching lightspeed and time stopping. Things that move at lightspeed to not stop time.
PhysBang
But we do have direct measurement of gravity time dilation across different levels of gravity. Yes, we have yet to observe time stopping due to gravitational acceleration, but that is the endpoint of the graph that results when you plug in the data we do have from direct observation.
But we do have direct observation of mass at above 99% of lightspeed and every level from there down. And their time does slow as they get closer to lightspeed. We fling lots of little bits of mass around and around at .99c+, collide them with each other, creating lots of little bitty clocks moving very near lightspeed and watch how far they move compared to how far those same particles could move in the known short lives they have at non-relativistic speed. And their time is dilated, a lot, they go many times the distance they should. Plot that on a graph and time stops at lightspeed. The fact that lightspeed is not possible for anything with mass does not make those measurements or observed effects invalid, it's also impossible to have completely empty space so there is no absolute time(where time would have zero dilation). Speed dilates time proportionally to speed. Speed shortens distance(as seen from inside the frame, it becomes zero at lightspeed). These are observed facts. That's why photons experience no time, have no length and transit through a dimension they see as having no length. As do all massless "particles". And what they see around them in their frame is every bit as real for them as what you see around you is real for you.
Grumpy
But we do have direct measurement of gravity time dilation across different levels of gravity. Yes, we have yet to observe time stopping due to gravitational acceleration, but that is the endpoint of the graph that results when you plug in the data we do have from direct observation.
But we do have direct observation of mass at above 99% of lightspeed and every level from there down. And their time does slow as they get closer to lightspeed. We fling lots of little bits of mass around and around at .99c+, collide them with each other, creating lots of little bitty clocks moving very near lightspeed and watch how far they move compared to how far those same particles could move in the known short lives they have at non-relativistic speed. And their time is dilated, a lot, they go many times the distance they should. Plot that on a graph and time stops at lightspeed. The fact that lightspeed is not possible for anything with mass does not make those measurements or observed effects invalid, it's also impossible to have completely empty space so there is no absolute time(where time would have zero dilation). Speed dilates time proportionally to speed. Speed shortens distance(as seen from inside the frame, it becomes zero at lightspeed). These are observed facts. That's why photons experience no time, have no length and transit through a dimension they see as having no length. As do all massless "particles". And what they see around them in their frame is every bit as real for them as what you see around you is real for you.
Grumpy
PhysBang
But we do have direct measurement of gravity time dilation across different levels of gravity. Yes, we have yet to observe time stopping due to gravitational acceleration, but that is the endpoint of the graph that results when you plug in the data we do have from direct observation.
But we do have direct observation of mass at above 99% of lightspeed and every level from there down. And their time does slow as they get closer to lightspeed. We fling lots of little bits of mass around and around at .99c+, collide them with each other, creating lots of little bitty clocks moving very near lightspeed and watch how far they move compared to how far those same particles could move in the known short lives they have at non-relativistic speed. And their time is dilated, a lot, they go many times the distance they should. Plot that on a graph and time stops at lightspeed. The fact that lightspeed is not possible for anything with mass does not make those measurements or observed effects invalid, it's also impossible to have completely empty space so there is no absolute time(where time would have zero dilation). Speed dilates time proportionally to speed. Speed shortens distance(as seen from inside the frame, it becomes zero at lightspeed). These are observed facts. That's why photons experience no time, have no length and transit through a dimension they see as having no length. As do all massless "particles". And what they see around them in their frame is every bit as real for them as what you see around you is real for you.
Grumpy
Grumpy, your post above is an example of what PhysBang was saying. Both of your examples of direct observation are true. We have observed, under limited conditions that gravitational time dilation and speed related time dilation does exist. But from there you plug the observed data into the underlying theory and present conclusions - that time stops at an event horizon and at the speed of light - as if they had been directly observed and confirmed... Both remain debatable extensions of theory. IOW theoretical conclusions, not observed facts.
E.g.,
So while I understand the reasoning behind this particular claim of time stopping at light speed, it seems to get in the way of explaining physical events that happen all the time (e.g., light reaching us from the sun after a delay) that do not seem to merely be illusions.
Even if we grant the above, the following is not an observation, it is an extrapolation.
But it's not even the case in GR. In GR, we can identify the worldline of a photon, or the point at which light is emitted and the point at which light is absorbed. Points on this worldline, or the latter points, have a length assigned to them by a spacetime metric (from a number of many nice, well-behaved metrics) of 0, but any attempt to identify a time coordinate for these events will have different time assignations.
So while I understand the reasoning behind this particular claim of time stopping at light speed, it seems to get in the way of explaining physical events that happen all the time (e.g., light reaching us from the sun after a delay) that do not seem to merely be illusions.
PhysBang
The worldline of a photon in our frame is not the worldline the photon sees. Each frame has it's own reality. In non-relative spacetime we see light transit spacetime at c. In the photon's view none of that spacetime in the direction of it's travel exists, it experiences no time and the moment of it's emission and the moment of it's absorption are the same moment. It carries no mass/energy, but it acts like a hole in spacetime that energy can pass through. All of that is true.
And far from getting in the way, these things make how the Universe is seen to behave comprehensible, allowing people like Einstein to describe it very well and work out the interconnectedness of all it's properties. The delay between the sun and us does not exist in the frame of the photon. And everything in our frame is some distance in our past. Lightspeed is a limit, nothing travels faster and time and space distort to make that always so. These are far from the weirdest ramifications of that one fact.
OnlyMe
You don't need theory to plug your data into a graph, that is actually something you do before you try to develop a theory. And just plotting your data gives you the same slope. Plus our observations of lightspeed dilation are only limited in that 1% of lightspeed that we have not directly measured, so we do have solid data for 99% of the range of speed from dead stop(relative)to 99% the speed of light, so no, you don't have a point. We know that nothing with mass can reach lightspeed so we have covered speed pretty exhaustively before we even apply theory to extrapolate that last little bit. Since in that top range the slope is exponential we just say it tends toward infinity. That's time dilation tending toward infinity(IE full stop)at lightspeed. That's relativistic mass tending toward infinity, that's length contraction tending toward infinity, that's energy requirements for further acceleration tending toward infinity. The fact we can never reach those infinities does not invalidate the data gathered at 99% of c. Theory is one thing, experimental confirmation that the theory accurately predicted your results another. You harp too much on the first and pay the second scant attention.
Grumpy
The worldline of a photon in our frame is not the worldline the photon sees. Each frame has it's own reality. In non-relative spacetime we see light transit spacetime at c. In the photon's view none of that spacetime in the direction of it's travel exists, it experiences no time and the moment of it's emission and the moment of it's absorption are the same moment. It carries no mass/energy, but it acts like a hole in spacetime that energy can pass through. All of that is true.
And far from getting in the way, these things make how the Universe is seen to behave comprehensible, allowing people like Einstein to describe it very well and work out the interconnectedness of all it's properties. The delay between the sun and us does not exist in the frame of the photon. And everything in our frame is some distance in our past. Lightspeed is a limit, nothing travels faster and time and space distort to make that always so. These are far from the weirdest ramifications of that one fact.
OnlyMe
You don't need theory to plug your data into a graph, that is actually something you do before you try to develop a theory. And just plotting your data gives you the same slope. Plus our observations of lightspeed dilation are only limited in that 1% of lightspeed that we have not directly measured, so we do have solid data for 99% of the range of speed from dead stop(relative)to 99% the speed of light, so no, you don't have a point. We know that nothing with mass can reach lightspeed so we have covered speed pretty exhaustively before we even apply theory to extrapolate that last little bit. Since in that top range the slope is exponential we just say it tends toward infinity. That's time dilation tending toward infinity(IE full stop)at lightspeed. That's relativistic mass tending toward infinity, that's length contraction tending toward infinity, that's energy requirements for further acceleration tending toward infinity. The fact we can never reach those infinities does not invalidate the data gathered at 99% of c. Theory is one thing, experimental confirmation that the theory accurately predicted your results another. You harp too much on the first and pay the second scant attention.
Grumpy
OnlyMe
You don't need theory to plug your data into a graph, that is actually something you do before you try to develop a theory. And just plotting your data gives you the same slope. Plus our observations of lightspeed dilation are only limited in that 1% of lightspeed that we have not directly measured, so we do have solid data for 99% of the range of speed from dead stop(relative)to 99% the speed of light, so no, you don't have a point. We know that nothing with mass can reach lightspeed so we have covered speed pretty exhaustively before we even apply theory to extrapolate that last little bit. Since in that top range the slope is exponential we just say it tends toward infinity. That's time dilation tending toward infinity(IE full stop)at lightspeed. That's relativistic mass tending toward infinity, that's length contraction tending toward infinity, that's energy requirements for further acceleration tending toward infinity. The fact we can never reach those infinities does not invalidate the data gathered at 99% of c. Theory is one thing, experimental confirmation that the theory accurately predicted your results another. You harp too much on the first and pay the second scant attention.
Grumpy
The point is made in your own post, as emphasized in bold above. In many of your posts you commingle that last little bit.., that has been extrapolated, that last little bit that is a projection of other data, with what has actually been observed.
I don't have a problem with the theory. However, you don't seem to have any clear understanding of that fine line that separates what has been observed to be consistent with the underlying theory and that which is a projection of a relatively local observation, to circumstances and conditions sometimes far beyond any currently possible direct observation/experience.
It doesn't really matter to me personally, but I keep thinking about those few who may be reading these discussions in an attempt to gain some real understanding of both the theoretical aspect and the reality. And again, you don't seem to me to differentiate between the two.
You often come off as saying that if you don't believe in the theory of relativity, as not being a theory.., or as a true and accurate description of reality, even under condition and frames of reference we have no way of observing directly, you don't understand the theory!
You seem committed to a certain metaphysical picture of the world that I do not share. I see frames as different ways of description for events. However, this is probably a side-issue. More importantly, I'm not sure what it means to have a frame co-moving with a photon. I do not know that we can meaningfully describe a photon's view, regardless of whether or not what you say is "true".
Yet I believe that Einstein did quite well without reference frames co-moving with photons.
This seems clearly false, at least practically. Without theory, we do not know what to measure or what to plot against something else.
On the contrary, I feel that OnlyMe and I are paying close attention to what has been experimentally confirmed and what has not. You seem to fear that because we point out that some conclusions are extrapolations that we are undercutting all the support for these conclusions. This is not the case. At the same time, we should not accept things that are not really extrapolations.
Do we at least all agree that a photon, any photon must by necessity and definition, always travel at "c"....or that the speed of light is constant.
OnlyMe
You do have a problem of not understanding the huge range of available observations that have confirmed everything Relativity says about the Universe. Just how is it that having directly observed 99% of the speed range as "a relatively local observation"? And the Earth's gravitational field is far from our only observation of gravity wells. Flinging spacecraft around Jupiter is a bit further up that scale. As far as light goes, those observations are solid and exhaustive, the extrapolation not going far out on a limb at all. And once you have multiple neutron star systems to observe you're getting damn close to seeing Black Hole level gravity effects, don't you think? That scale is not as evidenced as the speed scale is, but it too is solid observational confirmation. So no, these are not "far beyond any currently possible direct observation/experience." Just beyond your knowledge of currently possible direct observational evidence. Like I said, you give scant credit for current evidence confirming these things. Scientists know that only one of the predictions of the ramifications of Relativity is left without direct confirmation, Gravity Waves. And we already have indirect evidence of those in the CMB. As well as a relatively nearby triple neutron star system with a double/single configuration and close orbits. (In Cosmology we have the neatest instruments, we don't even have to build them). This system seems designed to provide direct evidence of gravity waves, three extremely accurate clocks attached to huge masses in rapid close in orbits(all three would fit within the Earth's orbit with room to spare). Relativity is confirmed to the point that it is perverse to withhold provisional acceptance(Gould's definition of a fact). So I do not think your point is worth the emphasis you put on it. I am not extrapolating beyond reason. The things we are telling you are confirmed to the ability of man to confirm anything. And we are on the verge of confirming the last prediction of Relativity today.
Grumpy
You do have a problem of not understanding the huge range of available observations that have confirmed everything Relativity says about the Universe. Just how is it that having directly observed 99% of the speed range as "a relatively local observation"? And the Earth's gravitational field is far from our only observation of gravity wells. Flinging spacecraft around Jupiter is a bit further up that scale. As far as light goes, those observations are solid and exhaustive, the extrapolation not going far out on a limb at all. And once you have multiple neutron star systems to observe you're getting damn close to seeing Black Hole level gravity effects, don't you think? That scale is not as evidenced as the speed scale is, but it too is solid observational confirmation. So no, these are not "far beyond any currently possible direct observation/experience." Just beyond your knowledge of currently possible direct observational evidence. Like I said, you give scant credit for current evidence confirming these things. Scientists know that only one of the predictions of the ramifications of Relativity is left without direct confirmation, Gravity Waves. And we already have indirect evidence of those in the CMB. As well as a relatively nearby triple neutron star system with a double/single configuration and close orbits. (In Cosmology we have the neatest instruments, we don't even have to build them). This system seems designed to provide direct evidence of gravity waves, three extremely accurate clocks attached to huge masses in rapid close in orbits(all three would fit within the Earth's orbit with room to spare). Relativity is confirmed to the point that it is perverse to withhold provisional acceptance(Gould's definition of a fact). So I do not think your point is worth the emphasis you put on it. I am not extrapolating beyond reason. The things we are telling you are confirmed to the ability of man to confirm anything. And we are on the verge of confirming the last prediction of Relativity today.
Grumpy
Within your local frame the speed of light is c. This holds for within the infaller’s local frame, as he sails across the event horizon ( ignoring tides).
Do we at least all agree that a photon, any photon must by necessity and definition, always travel at "c"....or that the speed of light is constant.
Sean Carroll
As you may already know, here r =2GM is the event horizon, and r = 0 is a true singularity at the black holes center.
My bold.
Sorry if I’ve confused you . Mas/energy alter spacetime, how different frames experience that altered spacetime depends on their relative motion / position to that spacetime. The distant observer says time stops at the horizon. To the infaller alls normal (ignoring tides).
nimbus
Good points. Every observer always sees his own frame as normal, no matter what. It is only the outside observer who sees the time dilation and length shortening. But the comoving observer sees the dimension he is traveling through as getting shorter.
Grumpy
Good points. Every observer always sees his own frame as normal, no matter what. It is only the outside observer who sees the time dilation and length shortening. But the comoving observer sees the dimension he is traveling through as getting shorter.
Grumpy
OnlyMe
You do have a problem of not understanding the huge range of available observations that have confirmed everything Relativity says about the Universe. Just how is it that having directly observed 99% of the speed range as "a relatively local observation"? And the Earth's gravitational field is far from our only observation of gravity wells. Flinging spacecraft around Jupiter is a bit further up that scale. As far as light goes, those observations are solid and exhaustive, the extrapolation not going far out on a limb at all. And once you have multiple neutron star systems to observe you're getting damn close to seeing Black Hole level gravity effects, don't you think? That scale is not as evidenced as the speed scale is, but it too is solid observational confirmation. So no, these are not "far beyond any currently possible direct observation/experience." Just beyond your knowledge of currently possible direct observational evidence. Like I said, you give scant credit for current evidence confirming these things. Scientists know that only one of the predictions of the ramifications of Relativity is left without direct confirmation, Gravity Waves. And we already have indirect evidence of those in the CMB. As well as a relatively nearby triple neutron star system with a double/single configuration and close orbits. (In Cosmology we have the neatest instruments, we don't even have to build them). This system seems designed to provide direct evidence of gravity waves, three extremely accurate clocks attached to huge masses in rapid close in orbits(all three would fit within the Earth's orbit with room to spare). Relativity is confirmed to the point that it is perverse to withhold provisional acceptance(Gould's definition of a fact). So I do not think your point is worth the emphasis you put on it. I am not extrapolating beyond reason. The things we are telling you are confirmed to the ability of man to confirm anything. And we are on the verge of confirming the last prediction of Relativity today.
Grumpy
Grumpy, most of what you offer above is not observed directly.
Take particles moving at 0.99% c. Not once is a single particle's speed measured start to finish.., and even when a group average is calculated it is not measured directly.
Space craft orbiting and or using a slig-shot maneuver around another planet, or even the earth, again is not direct observation of the gravitational field of the involved planet. The gravitational field, is predicted by both Newton's and Einstein's field equations.., and is indirectly confirmed by watching the affect on the space craft as it orbits or passed by...
There is a similar situation involved in both the neutron star case and gravity waves, they are both indirect observations. We don't watch neutron stars orbit each other in real time, we observe EM spectrum data associated with the system and interpret it based on theoretical assumptions...
This goes on and on...
Is how we interpret what we know of these things consistent with GR..? Yes!
Is it proof that any one conceptualization of GR's theoretical model, is the one and only reality? No!
Yes, GR is a successful theoretical model. Personally I don't believe it will ever be discarded, though it may at some point become a part of some greater understanding, just as Newtonian dynamics, became a weak field approximation of GR.
The issue is not whether GR is valid or even accurate, it is about how the theoretical basis of GR is conceptually applied as a description of reality. Again, it is my position that GR accurately describes the dynamics associated with gravitation, but it does not describe the mechanism.
OnlyMe
I did not say a single particle was traced, I said that the range of speeds up to lightspeed(almost)has been observed. What has been tracked is the trajectory of the products of collisions, very accurately tracked. And when a certain particle with a known lifetime travels many times the distance it's lifetime allows at the speed observed you have directly observed time dilation in relativistic clocks. In addition the pattern of spraying products repeated many times gives you a density profile of the colliding particles. Given a few million and a good computer you get a picture of those particles, just like Crick, et al got a picture of the DNA molecule using Xray crystallography. And rather that the ovoids protons are at non-relativistic speeds, they are thin lines perpendicular to the direction of travel. These Relativistic effects are as confirmed as an observation can be, your skepticism notwithstanding. You just don't know much about why these multi-billion dollar machines continue to be built, do you?
Neutron stars are clocks orders of magnitude more accurate than any clock on Earth. Observing their behavior is like an experiment a physicist would design to test the gravitational effects of Relativity. Just observing those clocks is direct evidence, the theory will fall out of it if you don't already have it beforehand, Relativity is based on a single fact, that lightspeed is constant in and between all frames. If you deny this I have to ask if you think your eyes and ears are lying to you, they are equally valid, equally indirect, equally open to questioning their veracity. Healthy skepticism is good, cynicism and ignoring the work being done, not so much.
Grumpy
I did not say a single particle was traced, I said that the range of speeds up to lightspeed(almost)has been observed. What has been tracked is the trajectory of the products of collisions, very accurately tracked. And when a certain particle with a known lifetime travels many times the distance it's lifetime allows at the speed observed you have directly observed time dilation in relativistic clocks. In addition the pattern of spraying products repeated many times gives you a density profile of the colliding particles. Given a few million and a good computer you get a picture of those particles, just like Crick, et al got a picture of the DNA molecule using Xray crystallography. And rather that the ovoids protons are at non-relativistic speeds, they are thin lines perpendicular to the direction of travel. These Relativistic effects are as confirmed as an observation can be, your skepticism notwithstanding. You just don't know much about why these multi-billion dollar machines continue to be built, do you?
Neutron stars are clocks orders of magnitude more accurate than any clock on Earth. Observing their behavior is like an experiment a physicist would design to test the gravitational effects of Relativity. Just observing those clocks is direct evidence, the theory will fall out of it if you don't already have it beforehand, Relativity is based on a single fact, that lightspeed is constant in and between all frames. If you deny this I have to ask if you think your eyes and ears are lying to you, they are equally valid, equally indirect, equally open to questioning their veracity. Healthy skepticism is good, cynicism and ignoring the work being done, not so much.
Grumpy
To be clear, you are continuing to make a claim about a scenario that is physically impossible. It doesn't help that you continue to confuse observations made with the help of extrapolations and conclusions made with the help of extrapolation about scenarios never observed in any way.