"Weakness of character is the only defect which cannot be amended." -Francois de La Rochefoucauld
So, you’d like to ruin the fabric of your space, would you? Similar to tying a knot in it, stitching it up with some poorly-run shenanigans, running a two-dimensional membrane through it (like a hole in a sponge), etc., it’s possible to put a topological defect in the fabric of space itself. This isn’t just a mathematical possibility, but a physical one: if you break a symmetry in just the right way, monopoles, strings, domain walls, or textures could be produced on a cosmic scale.
The differences between a Universe created according to standard cosmology (L) and one with a significant network of topological defects (R) give vastly different large-scale structures. We have good enough observations to rule out cosmic strings and domain walls as being a dominant component of the modern Universe. Image credit: Andrey Kravtsov (cosmological simulation, L); B. Allen & E.P. Shellard (simulation in a cosmic string Universe, R).
These could show up in a variety of ways, from abundant new, massive particles to a network of large-scale structure defects in space to a particular set of fluctuations in the cosmic microwave background. Yet when it comes time to put up or shut up, the Universe offers no positive evidence of any of these defects. Save for one, that is: back in 1982, there was an observation of one (and only one) event consistent with a magnetic monopole. 35 years later, we still don’t know what it was.
In 1982, an experiment running under the leadership of Blas Cabrera, one with eight turns of wire, detected a flux change of eight magnetons: indications of a magnetic monopole. Unfortunately, no one was present at the time of detection, and no one has ever reproduced this result or found a second monopole. Image credit: Cabrera B. (1982). First Results from a Superconductive Detector for Moving Magnetic Monopoles, Physical Review Letters, 48 (20) 1378–1381.
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Spacetime is a deductive consequence of Einstein's constant-speed-of-light postulate so any aspect of it, including defects, should be explicitly deducible from this postulate:
Quote: "Special relativity is based on the observation that the speed of light is always the same, independently of who measures it, or how fast the source of the light is moving with respect to the observer. Einstein demonstrated that as an immediate consequence, space and time can no longer be independent, but should rather be considered a new joint entity called "spacetime."
If an aspect of spacetime is not explicitly deducible from the postulate, that is, if it is just a pet idea of Ethan Siegel or some other Einsteinian, then the respective "theory" is not even wrong.
Ethan, I promised to leave the blog but did not keep my word, and you promised to ban me, so - go ahead :) .
If we have a star with only two planets in one orbital turning around that star with The same spead and in opposite direction with respct to eath other so that when one of them is in The right side of The star The another one is in The left side of The star and The distance of each of them is about 150 000 000 kilometer away from their star(equal to The distance between our earth to our sun),so The light of that star reaches after about 8 minutes +20 second to both of them at The same time(like The time that The light comes from our sun to our earth).but two photons of light in opposite direction after traveling each one 150 000 000 kilometer distance from that star to their opposite direction and reached to both planrts at The same time(each photon after 8 minutes +20 seconds) The question is that! Why are two photons after 8 minutes+20 second 300 000 000 kilimeters away from each other(twice The spead of light).The whole timepassing was 8 minutes 20 second in all three balls.
It may have something to do with the fact the photons were generated from the star. Neither photon generated the other, so relatively, they have nothing to do with each other. Their relative motion is only to the star, not each other. I'm sure others may be able to express this more eloquently.
:)
@ mehrdad
You and your friend get into cars and drive from the city in opposite directions, traveling 100km/h each. After one hour you are 200km away from your friend. Does that mean you were traveling 200km/h?
I mean.. this is basic elementary school math/physics. Speed and distance are not the same thing. Your whole photon/planets/sun setup is irrelevant and might be just adding to your confusion, if you're struggling with these basic concepts... which is odd that you are.
Nothing actually moves in a mathematical construct like space time, It can't even accommodate an impulse to motion, so the entire idea of it somehow affecting physical reality is quite pointless Platonistic hand waving. What Ethan is basically proposing is that if you write a fictional novel about something real, changing the novel alters the subject. Nope, only in the land of make believe fiction.
@Sinisa Lazarek,
If you really want to bake your noodle about light speed, try to make a gravitational effect like an orbit operate as observed with gravity propagating at c. It does not work. Newtonian mechanics treats the propagation of gravity as instantaneous (to agree with observed movement), and Einstein's solution side steps the issue altogether.
@CFT:
"Nothing actually moves in a mathematical construct like space time"
Some mathematical constructs are dynamic, like Cellular Automata, and allow motion, collisions etc. An example:
https://en.wikipedia.org/wiki/Puffer_train
@ CFT
bake my noodle about light speed?? rofl.. nah.. I'll leave that to you. Oh wait.. you don't have any actual science to offer. Ah, too bad. Anyhow, my comment was to a person poting nothing about speed of light or gravity or einstein.... so what's the point of your comment. Craving attention like MM is did couple of weeks back?
mehrdad,
The situation you described absolutely does not contradict relativity because there is no observer in that case who would measure the speed of either photon to be anything other than c. The observer at the source would measure a distance of 150,000,000 km with a travel time of 500 seconds, yielding the correct value for both photons. If we call photon A the one travelling to planet A, and likewise, photon B travelling to planet B, an observer on planet A would observe that photon A travelled 150,000,000 km in 500 seconds, and similarly for photon B. The observer on planet B would observe likewise.
The only remaining possibility is that there is an observer travelling along with one of the photons, say photon A. First off, this is physically impossible, so it really need not even be considered. There is no such thing as a massless observer, so no physically possible observer can travel at light speed. Let's assume then an observer travelling only at approximately light speed, say 0.999c. This observer travels in the direction of photon A. The distance between the source and planet A according to an observer on A is 150,000,000 km, but according to our travelling observer, this distance is only 6,700,000 km. On planet A, we measure the time it takes for photon A to travel from the source as 500 seconds. The travelling observer, though, would measure the same time interval as 22.36 seconds. Dividing the observer's distance by the time gives 6,700,000/22.36 = 300,000 km/sec, in perfect accord with relativity. (This would also be true for photon B as well.)
Could The Fabric Of Spacetime (defined by Ethan as "nothingness itself") Be Defective?
The concept of "nothingness itself" being a defective fabric is a product of very confused thinking, Ethan.
What, no follow up on your invitation to relativity critics to state what it would take to convince us that Einstein was right about GR and/or SR? See my reply in week #168 comments.
Thanks for The answers
In my example i wanted to know that if we suppose each one of The two photons which travels in opposite direction with respct to each other be meanwhile as The observer for The another one(photon A becomes The observer of photon B and phiton B becomes The observer of photon A),here photon A (as an observer) doesn't observe that photon B is traveling and is going away faster than The speed of light per second.
@mehrdad;
I think I understand what you mean. Assume two spaceships start together as next to each other. Then they start moving in opposite directions faster and faster approaching speed of light (which they can never reach exactly). If they could keep observing each other what would they see?
I think Special Relativity answer is this:
They would see each other as experiencing time slowing down. (If they could see each other's wall clocks, those clocks would be changing slower and slower.) Also they would see each other experiencing length contraction. Light coming from each other would be more and more redshifted. And from what they see, whenever they measure each other's speed, those speeds would just approach speed of light closer and closer but never could reach exactly. (And if the two observers were photons only, then time would be stopped by them. So measuring someone else's speed is impossible.)
@Frank
Thank you
My pleasure..
@Frank #7,
I agree with you that there are systems where things move, change and interact. Space Time is not one of them however, it is often called a 'block universe' model, because nothing in it can interact and change.
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If the model you are using to describe something in our universe can not accommodate things that are obviously happening in our universe (like the standard model and gravity for example) then the model should be taken as just a play toy model, and not be taken seriously in how the universe works.
@Sinisa Lazarek #8,
You lack curiosity and you bore me. Science isn't an unquestionable holy writ, so please stop treating as such.
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NASA uses Newton's gravity equations to calculate orbits, not Einstein's, with good reason. If you know your principia, you know gravity is treated as propagating instantaneously in Newton's equations. Scientifically, we know this can't be true, but, to make the math work in agreement with observation, it is treated as such and then forgotten about when convenient so you can then can go back to mindlessly regurgitating GR.
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For an orbit to work mathematically, information about the mass AND position of the objects involved have to somehow be conveyed to one another very close to instantly (or many times c), and this is not understood how this would happen in reality. If you do some digging, you will find we do not even actually orbit what appears to be the sun in the sky, but something twenty arc seconds ahead of where the sun appears to actually be. In other words we orbit where the sun actually is, not where it appears by the relativistic time the light of the sun reaches the Earth, this would cast serious doubt on gravity being propagated at c.
@CFT,
Yes Relativity implies a static Block Universe, but Quantum Mechanics disagrees.
I think physicists are divided on which is the correct view of time. Is future predictable (Block Universe) or not (Quantum Mechanics)?
I think both views are correct but in different scales.
Future is unpredictable in micro (quantum) scale but it is predictable in macro (relativity) scale.
If you think, how that can be possible, just learn about cellular automata used for fluid simulation to see an example of the same situation.
But of course these are just my opinions and I am not a physicist.
@Frank #17,
The problem with quantum mechanics is that it isn't in any way causally mechanical, it is purely statistical in nature and produces purely statistical answers, even when those answers are clearly not correct. Just remember, reality isn't made of math, and calculations aren't physical causes. This really shouldn't come to anyone as a shock, as it is always the case that what you use to measure with determines the form of what your answer looks like. Looking through rose colored glasses tends to make things look rosey. If you measure in customary units, your answer will be in the same (hopefully). If you measure in metric units your answer will be in the same metric. The problem is when people confuse the means of measurement with what is being measured. This isn't a metaphysical or philosophical complaint, it is an actual problem of measurement and calculation in how it relates to what is being observed. If I do not fully understand what determines an outcome with precision, yes I can assign a probability to it. However, this in no way explains the outcome, or the actual method by which the outcome was achieved, and gives the strong misimpression that the cause was also 'statistical', when clearly, the statistical element was merely imposed by the methodology of statistical measurement and calculation, not the actual subject itself.
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If I don't know why you order a particular sandwich at the deli you go to each day, I can tally what you do order, and over some period of time do some statistical calculation that will fall into some degree of accuracy with what you will order. Problem is, this method explains nothing about what process is actually going on to make the selection, and is deeming that unknown process to be equivalent to the substituting statistical probabilities (mathematical seight of hand for 'I don't know why') for whatever that method actually is and then convincing those looking at such calculated probabilities with the common mathematical delusion they understand why certain things are happening. This is a huge problem in physics because so much has been so blindly stacked up for so many years in this manner.
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Presently, the LHC is knocking many of these statistical assumptions down one after another. Every supposed new discovery has been a desperate gasp of prolific frantic paper publishing and turns out to be nothing but a phantom of calculations. Soon, the very foundations that supported the Higgs particle itself is going to be falling under increasing scrutiny, kind of hard to say you found something when the theorized broken symmetry you claim is it's underpinning is found to be just another stacked statistical assumption.