Is there any hypothetical way an object can travel in all directions at the same time? — TiredThinker
If an object could actually reach the speed of light would the object become 2 dimensional from everyone else's perspective? — TiredThinker
My understanding is when an object approaches the speed of light from the point of view of an outside viewer the object contracts in the direction of the path?
If an object could actually reach the speed of light would the object become 2 dimensional from everyone else's perspective?
Is there any hypothetical way an object can travel in all directions at the same time? If that were so would it not be expanding? And if it were doing that at the speed of light would it not also be becoming 0 dimensional? — TiredThinker
For a photon, which has no mass and always travels at the speed of light, distance and time only exist from the perspective of the observer: to a photon there is no such thing as distance and time, once it's emitted, it reaches its destination instantly in zero time. — staticphoton
Speed is a relative thing, so a more correct way to say this is that anything (Earth say) contracts in the direction of motion relative to any reference frame in which Earth moves quickly.My understanding is when an object approaches the speed of light from the point of view of an outside viewer the object contracts in the direction of the path? — TiredThinker
This is meaningless. Light does not define a valid reference frame.If an object could actually reach the speed of light would the object become 2 dimensional from everyone else's perspective?
Linear velocity is a vector relative to some arbitrary reference. That vector can only point in one direction, so no, at least not relative to any specific reference.Is there any hypothetical way an object can travel in all directions at the same time?
Speed of light is a constant scalar, not a dimensional thing at all.And if it were doing that at the speed of light would it not also be becoming 0 dimensional?
Not disagreeing with any of this, but from the friend's perspective, he's not travelling at all and it is simply Alpha Centauri traveling to him in presumable some short time possibly less than 4 years.Say your friend is traveling to Alpha Centauri, about 4 light-years away.
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From your friend's perspective, you, the earth, and the distance to Alpha Centauri flattens as well.
He would arrive quickly (depending on how close to "c" he's traveling) because of this shortening of the distance, which also translates into the time shortening effect experienced by your friend in the fast moving rocket. — staticphoton
This cannot work. For one thing, as stated above, there is no valid 'perspective of the photon'. Secondly, if unobstructed, no photon reaches an edge of the universe. For instance, light currently emitted from a star 16 billion light years away will never reach here period after any amount of time as measured by anything. This of course cannot be true in Minkowskian flat spacetime, but spacetime isn't flat in reality.But from the perspective of the photon, there is no distance and no time. If unobstructed, it will reach the "edge of the universe" (if there was such a thing) in zero time — staticphoton
OK, I'll buy that. You inflate a balloon, and each part of the balloon moves at a different velocity relative to the center. But this isn't the velocity of the balloon, it is a bunch of separate velocities of a set of parts, each with different motion.Perhaps if an object expanding in all directions at the speed of light being made of many atoms at what point is a bunch of atoms an object and when is it just atoms traveling in exactly one direction each? — TiredThinker
He would arrive quickly (depending on how close to "c" he's traveling) because of this shortening of the distance, — staticphoton
This cannot work. For one thing, as stated above, there is no valid 'perspective of the photon'. Secondly, if unobstructed, no photon reaches an edge of the universe. For instance, light currently emitted from a star 16 billion light years away will never reach here period after any amount of time as measured by anything. This of course cannot be true in Minkowskian flat spacetime, but spacetime isn't flat in reality.
Relative to a cosmological coordinate system (a coordinate system in which the size of the universe is not bounded), light fades to zero energy (proper distance method) or coasts to a halt (comoving distance method). Both of those are the same coordinate system with different methods of specifying distance between objects. — noAxioms
So that in conclusion, at the speed of light, all distances and all times are simultaneous. A singularity. Therefore matter cannot exist. Only pure "potential" energy. — Benj96
For a photon, which has no mass and always travels at the speed of light, distance and time only exist from the perspective of the observer: to a photon there is no such thing as distance and time, once it's emitted, it reaches its destination instantly in zero time. — staticphoton
Well, there seems to be a consensus among the posters regarding what happens to time at lightspeed and perhaps beyond via simple extrapolation. There are attempts to describe this state but I feel we could improve upon them if only those who have the relevant info tried ... a little harder. — Agent Smith
I could tell you there is a vein of gold 1 mile under your feet, but if you want to see that gold with your own eyes, you've got to dig. — staticphoton
Clearly a photon does not have a perspective, just trying to get the point across that to a photon there is no such thing as time. — staticphoton
In QFT, the universe contains 'interacting' fields. Every field permeates the entire universe, yes?
So does a 'photon'/field excitation really 'travel' at all?
Like a water wave or a mexican wave in a crowd of people. Each person just undulates in sequence order. Each person just stands up and sits down at the correct time. This gives the appearance of a moving wave. If a photon can appear at any point in space or time then perhaps it does not have to travel as it is already there and has been there since the big bang singularity. The speed of light would then be an observed constant of propagation through a universal field, but the 'photon' can arrive at any point in the universe instantly as a 'photon' has always existed at every point in the universe — universeness
...and which can explain the hypothesis of the big bang and the universe as we know it being a "bubble" in a pure energy field. Like, if infinite and there are infinite quantum possibilities that can occur in that infinite energy, it would eventually lead to the possibility of a bubble where energy fades out and then deflates back into pure energy. Since that pure energy "locally" fades and that energy is between singularities within its "bubble" (like black holes), it appears as matter, like gas crystalizing in the air. — Christoffer
I like this analogy a lot. Seems very intuitively logical and reasonable. My mind is chewing on it. Food for thought. — Benj96
In QFT, the universe contains 'interacting' fields. Every field permeates the entire universe, yes?
So does a 'photon'/field excitation really 'travel' at all?
Like a water wave or a mexican wave in a crowd of people. Each person just undulates in sequence order. Each person just stands up and sits down at the correct time. This gives the appearance of a moving wave. If a photon can appear at any point in space or time then perhaps it does not have to travel as it is already there and has been there since the big bang singularity. The speed of light would then be an observed constant of propagation through a universal field, but the 'photon' can arrive at any point in the universe instantly as a 'photon' has always existed at every point in the universe. — universeness
..and which can explain the hypothesis of the big bang and the universe as we know it being a "bubble" in a pure energy field. Like, if infinite and there are infinite quantum possibilities that can occur in that infinite energy, it would eventually lead to the possibility of a bubble where energy fades out and then deflates back into pure energy. Since that pure energy "locally" fades and that energy is between singularities within its "bubble" (like black holes), it appears as matter, like gas crystalizing in the air. — Christoffer
My understanding is when an object approaches the speed of light from the point of view of an outside viewer the object contracts in the direction of the path?
If an object could actually reach the speed of light would the object become 2 dimensional from everyone else's perspective?
Is there any hypothetical way an object can travel in all directions at the same time? If that were so would it not be expanding? And if it were doing that at the speed of light would it not also be becoming 0 dimensional? — TiredThinker
According to the theory of relativity, as an object approaches the speed of light, it will appear to contract in the direction of its motion. This is known as length contraction. However, the object itself does not actually shrink; it is only its appearance that changes from the perspective of an outside observer.
If an object were to reach the speed of light, it would not become two-dimensional from the perspective of outside observers. This is because the speed of light is a limiting speed; it is impossible for any object to actually reach the speed of light, so the question of what would happen if an object did is purely hypothetical.
It is also not possible for an object to travel in all directions at the same time, since this would violate the laws of physics. In order for an object to move, it must have a definite direction and speed. An object that is expanding, such as the universe, is not moving in any particular direction, but rather is increasing in size in all directions simultaneously.
As for the question of an object becoming zero-dimensional, this is also not possible according to the laws of physics. An object must have a non-zero size in order to exist, so it is not possible for it to become zero-dimensional. — ChatGPT
A photon is not an object in the traditional sense of the word. A photon is a type of elementary particle, which is a fundamental building block of matter. Unlike objects, which have a definite size and shape, photons do not have any physical form or structure. They are characterized by their energy and momentum, and they can travel through space at the speed of light. Because of their unique properties, photons are sometimes described as "particles of light." — ChatGPT
It is impossible for a photon, or any other form of matter or energy, to reach the edge of the universe. This is because the universe is expanding, and the space between galaxies is getting larger all the time. As a result, the distance to the edge of the universe is constantly increasing, so it is not possible for anything to reach it. Additionally, the concept of the "edge" of the universe is not well-defined, since the universe is thought to be infinite in size. — ChatGPT
In the reference frame of a photon, time does not pass, so the concept of the photon reaching the edge of the universe is not well-defined. In the reference frame of a photon, the universe appears to be a sphere with a radius of zero, and the photon is always at the center of the sphere. This is because the speed of light is constant in all reference frames, so from the perspective of the photon, it is always at the same point in space, no matter how far it has traveled. — ChatGPT
This is true only of an inertial frame of reference, and only in flat Minkowskian spacetime (with no gravity anywhere). It isn't true of any other kind of coordinate system.By the way, no photon will ever "coast to a halt". Any photon, regardless of energy or frame of reference will always travel exactly at the speed of light. — staticphoton
I agree with the answers, but I still have commentary.I put your question to OpenAI's ChatGPT. To the best of my knowledge, the responses are correct. — Andrew M
This can be interpreted in different ways, so to clarify, relative to some inertial frame in which some object is moving, that object will be measured to be contracted.According to the theory of relativity, as an object approaches the speed of light, it will appear to contract in the direction of its motion. This is known as length contraction. However, the object itself does not actually shrink; it is only its appearance that changes from the perspective of an outside observer. — ChatGPT
As for the question of an object becoming zero-dimensional, this is also not possible according to the laws of physics. An object must have a non-zero size in order to exist, so it is not possible for it to become zero-dimensional. — ChatGPT
Good question. All fundamental particles lack a meaningful size. Size is a classic concept and only applies to classic things. Size in this context means distance between different components of an object, and photons, electrons, etc do not have components, and thus have no meaningful size and cannot meaningfully contract relative to some frame.Isn't a photon an object? — Andrew M
Can a photon travel to the edge of the universe? — Andrew M
OK, this answer implies that there is a meaningful edge to the universe, which is not part of any accepted theory I've seen. No information emitted now can get beyond the current event horizon, per the top of this post. That distance is a lot closer than the nonexistent "edge of the universe". We can see stuff beyond that horizon, but only via light that was emitted back when the objects we see were much closer and the event horizon was further away ('further' depending heavily on how such distances are measured).It is impossible for a photon, or any other form of matter or energy, to reach the edge of the universe. This is because the universe is expanding, and the space between galaxies is getting larger all the time. As a result, the distance to the edge of the universe is constantly increasing, so it is not possible for anything to reach it. Additionally, the concept of the "edge" of the universe is not well-defined, since the universe is thought to be infinite in size. — ChatGPT
The field doesn't, but the excitation does. A field is something that is by definition 'everywhere' and so it isn't meaningful to speak of it travelling, which implies it gets to a location where it wasn't before.So does a 'photon'/field excitation really 'travel' at all? — universeness
Relative to Paris, it takes light less time to go to the moon and back than the distance involved. It's really close, but light travels faster than c relative to Paris, at least along this path. This is due to spacetime not being Minkowskian between here and the moon, and not so much due to the how Paris moves during that experiment.
In the frame of Paris (the coordinate system in which Paris stays stationary), eastbound light goes slower than westbound light, so signals sent via say 20 mirrors around the world will get back to Paris quicker in one direction than the other. This is the well known Sagnac effect. — noAxioms
In the frame of Paris, a light pulse in just the right place somewhere around the orbit of Neptune will coast to a halt, then reverse and go back the way it came — noAxioms
Oh yea: In cosmological coordinates with distance measured as comoving distance, light speed (comoving distance per second) in a vacuum slows over time, approaching but never reaching a halt. But there's a distance (about 16 BLY from where it gets emitted today) beyond which it will never reach even in infinite time, so if it doesn't slow to a halt, it will surpass this limit. That's the current comoving distance to the event horizon, and if light emitted now from there can never reach us, then light from here can't reach them either.
I have a graph of such coordinates if you don't know what I'm talking about. — noAxioms
OK, this answer implies that there is a meaningful edge to the universe, which is not part of any accepted theory I've seen. — noAxioms
Whenever you try to measure something infinite, the best you can do in practice is to say it’s larger than something finite that you have measured. But to show that it was really infinite you would have to show the result was larger than anything you could possibly have measured. And there’s no experiment that can show that. So, infinity is not real in the scientific sense.
Nevertheless, physicists use infinity all the time. Take for example the size of the universe. In most contemporary models, the universe is infinitely large. But this is a statement about a mathematical property of these models. The part of the universe that we can actually observe only has a finite size.
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But maybe using infinity and zero in physics brings in mistakes because these assumptions are not only not scientifically justified, they are not scientifically justifiable. And this may play a role in our understanding of the cosmos or quantum mechanics. This is why some physicists, like George Ellis, Tim Palmer, and Nicolas Gisin have argued that we should be formulating physics without using infinities or infinitely precise numbers. — Is Infinity Real? - Sabine Hossenfelder
Let’s face it: Despite their seductive allure, we have no direct observational evidence for either the infinitely big or the infinitely small.
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Our challenge as physicists is to discover this elegant way and the infinity-free equations describing it—the true laws of physics. To start this search in earnest, we need to question infinity. I’m betting that we also need to let go of it. — Infinity Is a Beautiful Concept — And It's Ruining Physics - Max Tegmark
The selected quotes from the above physicists concern infinity, which I did not mention in my comment. I did reference infinite time.OK, this answer implies that there is a meaningful edge to the universe, which is not part of any accepted theory I've seen.
— noAxioms
True, though neither is it ruled out. As physicists' Sabine Hossenfelder and Max Tegmark note: — Andrew M
You quoted two examples in that comment (M and S). Only S has to do with rotation, and if you read my comment carefully, I said S has nothing to do with the motion of anything, but rather with a rotating frame of reference. Motion, after all, is entirely frame dependent. In an inertial frame, light moves east and west at the same speed and the only reason one takes longer than the other is because the path taken is longer one way than the other.This is due to the rotary motion of the moon around the earth and has nothing to do with the speed of light changing. The Sagnac effect was conceptualized before the theory of General Relativity was created. — staticphoton
Careful about the use of the word 'obvious' since it almost always means one is relying on intuition instead of what the mathematics says, which is anything but intuitive.It is obvious that in a large enough expanding universe, to any observer there is a horizon beyond which the expansion happens faster than the speed of light, and that a photon emitted from his flashlight will never reach this horizon. — staticphoton
He would arrive quickly (depending on how close to "c" he's traveling) because of this shortening of the distance, — staticphoton
Well, that's a twist I was not aware of. :chin: — jgill
"A high speed traveler is never late. Nor is he early. He arrives precisely when he means to."If we measure interstellar distances in km and not light years, and our clock is ticking a bit slower as we advance to our destination explain how that actual distance may diminish from our perspective beyond that calculated by D=RT, thus having us arrive early? — jgill
I'm still curious about this. If we measure interstellar distances in km and not light years, and our clock is ticking a bit slower as we advance to our destination explain how that actual distance may diminish from our perspective beyond that calculated by D=RT, thus having us arrive early? Is my question even valid in the context of relativity? — jgill
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