Why we can never travel faster than the speed of light

[Neogaia777]

Based on General Relativity and actual evidence for "frame dragging" ("local space" or "space - time" moved or "dragged" by objects with mass) is well established:

frame-dragging « Einstein-Online

www.einstein-online.info

https://einstein.stanford.edu/content/education/lithos/litho-fd.pdf

Mass curves space time but most people don't know if the mass is moving, it drags space along with it as well. The effect is incredibly miniscule for with everyday objects we encounter. But for extremely dense and extremely massive objects like neutron stars, the effect will be significant and spectacularly noticeable.

Theory of General Relativity also accounts for "linear dragging" for objects moving in a straight line but gathering evidence for it is much harder compared to spinning examples.

It pulls/drags/tugs on the fabric of space a little bit for what's behind it as it travels, but as the mass gets farther and farther away, it will eventually return back to normal, but no where is it ever dragged or moving at the speed of light, and not even close to it, and those frames will eventually return back to normal once the mass has passed by/through far enough, and this is because of it's gravity well, or pull, that is shorter in front of it, but is longer behind it as it travels, but that space will eventually go back to normal, because it's effect is only temporary, and is only for when/while/as it is traveling, or is passing through, etc. IOW's the fabric of space (space-time) never really moved, or is moving, but is just only affected by some objects gravity wells temporarily as they are moving, etc. It will return back to much more normal once the object has passed, etc.

God Bless.

 

[Hans Blaster]

Momentum, for that object, is just speed though, correct? So why can not that object be pushed to or beyond c? (Theoretically, etc) (Because just exactly how we might do that right now may seem to be impossible to or for us right now currently, etc).

No. Momentum and speed (or rather velocity, motion without a direction is meaningless) are different concepts. In relativity, unlike Newtonian mechanics, you can't just get to momentum by multiplying velocity and mass. There is also that relativistic "gamma" factor that gets larger and larger as the velocity approaches the speed of light.

p = mv/√(1-v²/c²)

as v approaches, 1/√(1-v²/c²) goes toward infinity. Near the speed of light v ~= c and p ~= mc/√(1-v²/c²) and all increases in momentum (from applying a force) goes to making v ever so closer to c, but it can't cross c since that would require infinite momentum at v=c.

 

[SelfSim]

Oh boy .. this thread has gone haywire.

To understand what's going on in the near relativistic physics regime, one has to understand that space is not the same as spacetime.
We're not even there yet.
The even more basic concepts of potential energy, kinetic energy momentum, velocity, speed and inertia aren't properly 'embedded'.

Excluding @sjastro and @Hans Blaster's inputs, there just seems to be too much silly competition to one up each other in the sense of: 'Check out how I can out propeller-head you', and so little reluctance to ponder in and soak up the basics, I don't think its going to be possible to have a coherent explanatory conversation(?)

 

[sjastro]

Thank you very much @sjastro, I really do appreciate you, just so you know that, ok.

But what I'm right now not understanding is why it takes 4 times more work, or force, to only double an objects velocity?

But understanding why it always takes more and more work, or force, to the point of approaching infinity, and maybe why, could really, really help me in understanding this right now currently?

Much thanks.

Take Care/God Bless.

KE = (½)mv²

Doubling the velocity v;

KE = (½)m(2v)² = 4(½)mv² hence KE increases by a factor of 4.

 

[sjastro]

@sjastro

And we're doing this in space, right? Are you maybe suggesting that there is some kind of drag or resistance in space maybe?

Isn't it when we push an object in space, that it will just keep going if we stop pushing it? So, why then does it take more and more force/work/energy to accelerate it, to be being applied to the object constantly up to the point of infinity as it approaches c to continue to be accelerating it at a constant rate?

Thank you again. I know you are trying to be simple, and I really do appreciate it, ok.

Take Care/God Bless.

There is no friction involved.

At relativistic speeds inertia increases, not due to an increase in mass in keeping with the modern convention of invariant mass, but in the context of Newton's second law which in relativistic form is F = 1/√(1-v²/c²)ma + (1/√(1-v²/c²))³m(v.a)v/c².
This shows that as speed increases, more force is required to produce the same acceleration, reflecting an increase in inertia.

 

[sjastro]

I decided to try China's DeepSeek AI which by reports is superior to OpenAI o1 which in turn is far better than GPT-4o I have been using in this forum.

It critiqued the first paragraph in the OP.

When the universe was created, it had warmth and cold, energy and non-energy, it``s the only universe we can have. All matter is energy in a cooler state, you can set anything on fire even rocks, so the basic form is energy. A space-ship, for example, will be all energy also in a cooler state, so there`s a limit on how fast it can travel like light otherwise. There`s no dark matter or energy invisible in space which slows things down, or matter if you travel far away enough from planets and rocks.

​

At least it was being diplomatic although I think there could have been some metaphorical content it didn't pick up on.
(If not the post is 100% nonsensical).

When I asked it why objects cannot travel at the speed of light there were no doubts about its answers although it used the old relativistic mass convention.

 

[timewerx]

It pulls/drags/tugs on the fabric of space a little bit for what's behind it as it travels, but as the mass gets farther and farther away, it will eventually return back to normal

Obviously, the effect is temporary and space returns to normal as soon as a passing mass has gained enough distance for its influence to blend in with background levels.

For practical interstellar travel, the effect must stay with the spacecraft at all times.

The key is to create that distortion to travel with the spacecraft. I may have a theoretical solution to this by creating an artificial "Event Horizon" that completely envelops the spacecraft to both accelerate the spacecraft and also allow it to reach faster-than-light speeds through "Frame dragging"

Not like in the movie "Event Horizon" where they used an artificial black hole to create it. In my concept, there is no artificial black hole involved. I have an idea to generate this Event Horizon but the technical details of "How?"

Hopefully soon, there will be a suitable AI I can work with. Obviously, you don't just ask it how you create an event horizon without a black hole or by generating "artificial mass". The AI will probably simply tell you "you can't". You have to strike it with questions you might already find in nature (some insight, hunches, and a bit of imaginative/creative thinking) because if it's really there, the AI will likely find or extrapolate it from the data. You still have to trick AI, else, it will just keep telling you that you can't beat the laws of physics. It will probably not readily acknowledge those extremely rare circumstances that certain laws doesn't seem to apply.

 

[Mark Quayle]

Sorry but I performed badly at mind reading 101 but despite this serious impediment I still answered your question.

The observer at C on the ground is measuring the approach speed of A relative to B and vice versa as 0.88c.
At relativistic speeds Galilean relativity does not hold and the approach speed is not the sum of A and B's speeds 0.6c + 0.6c =1.2c.
This is because observers cannot exceed the speed of light and all observers such as A, B and C in this case will measure the speed of light as being c in their respective frames of reference.

So, if I follow you, B is C and sees A as .88 the speed of light. So, there are no galaxies receding faster than their light approaching us.

That's what it sounds like you are saying.

I'm not understanding how none of them exceeding 'the speed of light' relative to some point in space, means that another moving the opposite direction cannot be exceeding the speed of light relative to the first. Whether someone is actually observing or not is irrelevant to how fast the light is approaching or departing

 

[Mark Quayle]

I decided to try China's DeepSeek AI which by reports is superior to OpenAI o1 which in turn is far better than GPT-4o I have been using in this forum.

It critiqued the first paragraph in the OP.

View attachment 360408
​

At least it was being diplomatic although I think there could have been some metaphorical content it didn't pick up on.
(If not the post is 100% nonsensical).

When I asked it why objects cannot travel at the speed of light there were no doubts about its answers although it used the old relativistic mass convention.

View attachment 360409​

This is frustrating to me. "The speed of light, relative to what???" I'm willing to admit that I just don't understand. I just wish someone could find a way to explain that I can understand.

The speed of light is not relative to static space, analogous to the way sound travels in gases, liquids and solids. Space is not a medium. As a car approaches, it does not mean its sound arrives faster from any one position than it would be arriving from that same position were the car unmoving. The doppler effect only means that the faster the light emitting object is approaching/receeding relative to any one point, the more/less waves-per-time (color).

 

[Neogaia777]

Oh boy .. this thread has gone haywire.

To understand what's going on in the near relativistic physics regime, one has to understand that space is not the same as spacetime.
We're not even there yet.
The even more basic concepts of potential energy, kinetic energy momentum, velocity, speed and inertia aren't properly 'embedded'.

Excluding @sjastro and @Hans Blaster's inputs, there just seems to be too much silly competition to one up each other in the sense of: 'Check out how I can out propeller-head you', and so little reluctance to ponder in and soak up the basics, I don't think its going to be possible to have a coherent explanatory conversation(?)

Well, I'm not trying to one up anybody, as I certainly have a lot to learn, and there is still a lot I don't yet know about yet, etc. And like I said in another post, even if I have to go back to school, and take a few classes, then that's what I'm going to do if I have to to learn a lot of it, etc. I have a great thirst for knowledge, and I only wish there was enough time in this lifetime for me left to know everything I want to know or learn in this lifetime, etc.

And @sjastro and @Hans Blaster I thank you very, very much for your input, and for your time. I will probably need to study and learn some more before I can get back to you probably, but thank you guys for your time

Take Care/God Bless.

 

[Neogaia777]

Well, I'm not trying to one up anybody, as I certainly have a lot to learn, and there is still a lot I don't yet know about yet, etc. And like I said in another post, even if I have to go back to school, and take a few classes, then that's what I'm going to do if I have to to learn a lot of it, etc. I have a great thirst for knowledge, and I only wish there was enough time in this lifetime for me left to know everything I want to know or learn in this lifetime, etc.

And @sjastro and @Hans Blaster I thank you very, very much for your input, and for your time. I will probably need to study and learn some more before I can get back to you probably, but thank you guys for your time

Take Care/God Bless.

The Beginning of my my collection that I just got a few months ago, but haven't gotten into yet, but plan to soon.

It's just the beginning, as I have to start with it back this far, and with the basics, the higher math's books, and other books I will be getting/adding to his collection more later, and in time. Algebra 2, Calculus, Pre-Calculus, Probability and Statistics, Physics, and many others, still need to be added to what is just right now the very beginnings of this collection.

Don't underestimate the "for dummies" series of books, they are very good at teaching, as they often explain things in a very simple, easy to understand way.

God Bless.

 

[SelfSim]

View attachment 360430
The Beginning of my my collection that I just got a few months ago, but haven't gotten into yet, but plan to soon.

It's just the beginning, as I have to start with it back this far, and with the basics, the higher math's books, and other books I will be getting/adding to his collection more later, and in time. Algebra 2, Calculus, Pre-Calculus, Probability and Statistics, Physics, and many others, still need to be added to what is just right now the very beginnings of this collection.

Don't underestimate the "for dummies" series of books, they are very good at teaching, as they often explain things in a very simple, easy to understand way.

God Bless.

What sort of math/physics is in the 'Wilderness Long-Term Survival Guide'?
I don't that one fits into the Dummy Series!

 

[Neogaia777]

What sort of math/physics is in the 'Wilderness Long-Term Survival Guide'?
I don't that one fits into the Dummy Series!

That's another subject I'm into. I'm an outdoors type, and for about the last seven years or so, I've gotten into survivalism, and emergency preparedness, and prepping. People generally learn/know about what they spend their time knowing, or getting to learn, or know about, and not what they don't, and not one of us knows everything, or knows it all, etc. Which is why I said that I wish I had more time in this lifetime, because there is a lot I want to get to learn/know about, etc. I have a pretty good skill set about a lot of things now, but there is still so very, very much more I want to get to know about, etc, and there's just not enough time for it all, etc.

Take Care.

 

[Neogaia777]

@sjastro @Hans Blaster

Ok, well how about this then? If you took an object (with mass) in space, and constantly applied the exact same amount of thrust throughout to it, and didn't ever change it, to make that object accelerate and gain speed, are you saying that it would no longer ever gain any more speed at some point? Or just what exactly? Because that doesn't make very much practical or physical sense to me, etc? Yes? No?

Oh, and if so, then maybe also why please, etc?

Much thanks.

Take Care/God Bless.

 

[sjastro]

So, if I follow you, B is C and sees A as .88 the speed of light. So, there are no galaxies receding faster than their light approaching us.

That's what it sounds like you are saying.

I'm not understanding how none of them exceeding 'the speed of light' relative to some point in space, means that another moving the opposite direction cannot be exceeding the speed of light relative to the first. Whether someone is actually observing or not is irrelevant to how fast the light is approaching or departing

The issue involves objects travelling in space-time rather than being carried by space-time expansion such as the recession velocities of distant galaxies which can exceed the speed of light and their velocities depend on the distance from the observer.

Suppose you are on a train moving at a constant velocity, there is no such thing as an absolute frame of reference, the train could be moving in a forward direction at a velocity v or the train is stationary and the countryside is moving backwards at a velocity of -v.
There is no preferred frame of reference and there is no physics experiment that can differentiate between the two for the observer on the train.
An observer on the ground however is stationary and the train is moving forward at a velocity v in his frame of reference.

This gets back to the original example of observers A, B, and C.
In observer A’s frame of reference, he may for all intents and purposes be stationary and the approach velocity is observer B approaching and similarly in observer B’s frame of reference he may be stationary and it is observer A that is approaching.
There is no preferred frame of reference and A and B’s frames of references are equally valid.
In observer C’s frame of reference known as the ground or laboratory frame, the symmetry of the velocities is observed as A and B are travelling towards each other at a speed of 0.6c but the approach speed is 0.88c not 1.2c as nothing can exceed the speed of light c for objects moving through space-time.

 

[sjastro]

This is frustrating to me. "The speed of light, relative to what???" I'm willing to admit that I just don't understand. I just wish someone could find a way to explain that I can understand.

The speed of light is not relative to static space, analogous to the way sound travels in gases, liquids and solids. Space is not a medium. As a car approaches, it does not mean its sound arrives faster from any one position than it would be arriving from that same position were the car unmoving. The doppler effect only means that the faster the light emitting object is approaching/receeding relative to any one point, the more/less waves-per-time (color).

It is the speed of light relative to the observer’s frame of reference given it is the observer who is measuring the speed of light.

The Doppler effect is a good example of the speed of light being the same in all observer’s frames of references whether they be stationary, moving towards the light source or away from it, as well as the direction of motion of the light source.
The speed doesn’t change only the wavelength which can be blue or redshifted depending on the direction of motion of the observers and light sources.

 

[Neogaia777]

It is the speed of light relative to the observer’s frame of reference given it is the observer who is measuring the speed of light.

The Doppler effect is a good example of the speed of light being the same in all observer’s frames of references whether they be stationary, moving towards the light source or away from it, as well as the direction of motion of the light source.
The speed doesn’t change only the wavelength which can be blue or redshifted depending on the direction of motion of the observers and light sources.

Yeah, but, if you're say, headed towards Mars, but away from Earth at half c, (or any speed really) and in a straight line between the two, then wouldn't the light coming from/off of Mars towards you be coming at you faster, and the light coming from/off of Earth behind you as you were traveling be coming at you slower, as you went? But then go back to normal once you stopped moving?

 

[sjastro]

Yeah, but, if you're say, headed towards Mars, but away from Earth at half c, (or any speed really) and in a straight line between the two, then wouldn't the light coming from/off of Mars towards you be coming at you faster, and the light coming from/off of Earth behind you as you were traveling be coming at you slower, as you went? But then go back to normal once you stopped moving?

As has been mentioned many times in this thread the speed of light is the same in all frames of references.
The speed will be be same if the light source is moving towards or away from the observer or the observer is moving towards or away from the source.

 

[Neogaia777]

As has been mentioned many times in this thread the speed of light is the same in all frames of references.
The speed will be be same if the light source is moving towards or away from the observer or the observer is moving towards or away from the source.

Well, I will agree with you that the speed of light doesn't actually change, but I don't see why or how if you are moving straight away from one light source, and straight to or towards another, why what you would be seeing from either one those light sources wouldn't change, or be either slower or faster as you went respectively, etc? Care to explain how or why that isn't, or wouldn't be true maybe?

 

[Mark Quayle]

It is the speed of light relative to the observer’s frame of reference given it is the observer who is measuring the speed of light.

The Doppler effect is a good example of the speed of light being the same in all observer’s frames of references whether they be stationary, moving towards the light source or away from it, as well as the direction of motion of the light source.
The speed doesn’t change only the wavelength which can be blue or redshifted depending on the direction of motion of the observers and light sources.

Yes, so, if I am hurtling through space at, say .6c away from the center of the galaxy, and a star is receding from the center of the galaxy in a trajectory opposite mine at .6c, we will not be able to see each other, because the light never arrives from the star to me, center of the galaxy irrelevant, except for the purposes of describing the situation.

This is why, as described by some authorities on the subject, there are, theoretically, distant galaxies we never see, not because they are too far and too faint, but because they are receding relative to us, too fast for the light from them to ever reach us.

Likewise, then, (but for the general expansion of the universe) we could theoretically be on a collision course with a celestial body moving towards us so fast that we will never see it until the collision?