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the speed of light question
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No, time dilation occurs at all speeds, not just close to c.
Eh yeah i know it occurs at all speeds.
I know SR is a better description of nature than Newtonian mechanics with Newtonian Mechanics a limiting case where speeds are a fraction of c.
Where the v squared over c squared in gamma is so close to zero that gamma is practically one hence practically no time dilation or length contraction.
It feels like you're responding to another poster.
I'm not talking about or interested in SR. I gave a rough explanation of it in the thread already talking what you are talking about. I'm agreeing with you.
No. I am saying that if we assume that a universe does exist, then space and time must also exist.
Without being cheeky, the act of assumption is done by an observer.
Space and time to me only have meaning after measuring them.However, the concepts of temperature and colour do not have to exist.
Aren't these concepts inextricably linked to physical phenomena.
A universe without temperature. Is that even possible. A thermodynamics expert might clear that up. But i always thought temperature was inextricably linked to internal energy. So no temp would mean no internal energy. Is that possible for a universe with stuff in it.
Colour (a biological processing of EM frequency) etc etc.A universe can theoretically exist without particles or light and therefore without the concept of temperature or colour.
So you're saying light is needed for temperature. That sounds wrong to me tbh. I would have thought internal energy is needed for temperature.
But either way, a universe without light or energy?
But with space and time?
Never heard of something like this. Is this possible anyone know.
Either way it would never be measureable (without light etc) and arguably non-existent.
Why does there seem to be a presupposition that space and time are more important physical phenomena than all other physical phenomena. That a universe with just space and time can exist but not just temperature and say energy can exist.Yes. But that is not what we mean by a dimension in physics. Space and time are not defined as dimensions only because they can be measured, we're certain they exist etc.
Yeah i know this. The 4 dimensions of spacetime are conventional dimensions. But are they more certain than other perceived and measured phenomena? :pac:. By the quoted statement, "we know they exist", all the other things we mentioned (that "we know exist") are dimensions. But i'm not saying that really. You seem to be arguing more strongly for it here. Im only half messing about them being dimensions :pac:
Ah i'm again being a bit facetious in all this. You can put anything into the dimension of a space in Linear algebra :pac::p0 -
take everything wrote: »Eh yeah i know it occurs at all speeds.
I know SR is a better description of nature than Newtonian mechanics with Newtonian Mechanics a limiting case where speeds are a fraction of c.
Where the v squared over c squared in gamma is so close to zero that gamma is practically one hence practically no time dilation or length contraction.
It feels like you're responding to another poster.
No, I was responding to your statement of "relative motion at speeds close to c lead to time dilation".take everything wrote: »Without being cheeky, the act of assumption is done by an observer.
Space and time to me only have meaning after measuring them.
I was not referring to measuring or observing anything, I was referring to a thought experiment. We know that stars were born and have since died since before life existed on Earth, but according how you are thinking, they didn't because no one was around to observe or measure them?take everything wrote: »Aren't these concepts inextricably linked to physical phenomena.
Yes, which is one of the reasons they are not dimensions. We can say that an object (or system) has an energy of x, a length of x, a temperature of x etc., but it doesn't make sense to say it has a time of x or a space of x. Dimensions do not describe a quality of a particle (or system).take everything wrote: »A universe without temperature. Is that even possible. A thermodynamics expert might clear that up. But i always thought temperature was inextricably linked to internal energy. So no temp would mean no internal energy. Is that possible for a universe with stuff in it.
I am an astrophysicist, I am such an expert.
Ignoring quantum fluctuations (which we are not talking about), an empty universe would not only have no temperature or internal energy but there would no benefit in defining what something called temperature or energy is.take everything wrote: »So you're saying light is needed for temperature. That sounds wrong to me tbh. I would have thought internal energy is needed for temperature.
No, I did not say that. Have a re-read.take everything wrote: »There seems to be a presupposition that space and time are more important physical phenomena than all other physical phenomena. That a universe with just space and time can exist but not just temperature and say energy can exist.
No, not more important, just more fundamental.0 -
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standardg60 wrote: »I am fascinated by light because to me light (and the expansion of it) is to me the only reason for existence.
It isn't, I'd recommend reading about the Movile Cave for example.standardg60 wrote: »How can 'massless' particles travelling at the speed of light be observed if there's no light to observe them?
We don't use light to observe other massless particles, we use other means.standardg60 wrote: »There may well be a universe that 'exists' without light but because our existence depends on light how could we possibly observe it? That to me is the part of the universe which has ceased to exist.
Again, this concept of needing to observe things for them to exist is incredibly flawed. By that logic the universe also did not exist before life formed.standardg60 wrote: »The most important for me being the point that the universe exists only as far as our speed of light allows us to see.
It doesn't. What you're referring to is the observable universe. According to cosmic inflation theory for example, the universe's size is instead at least 3x10^23 times larger than the observable universe.standardg60 wrote: »My theory is that we cannot exist unless the universe is expanding further and faster than what we can see. If you believe the universe can exist without light then why not believe it can also exist at a way faster light?
We know what the expansion speed (or rather, the expansion speed per distance) is, and it's much slower than the speed of light as I stated before. So your theory (and by theory, I mean your shower thought) is incorrect.standardg60 wrote: »If you believe the universe can exist without light then why not believe it can also exist at a way faster light?
It can, but it doesn't, and we know this as a fact.In order for us to observe time at all there must be an infinite number of universes all expanding at varying speeds of light faster (the past) and slower (the future) than ours, and that we are just travelling along that track.
No there doesn't, and that doesn't even make sense.The speed of light (or what we measure it to be) is the difference between an infinite speed and the speed at which we are currently expanding.
That makes even less sense.If my belief is correct then that difference will expand, ie. the speed of light will slow, this should be calculable to appease the doubters.
It doesn't. As I mentioned before, data from the Oklo natural reactors for example demonstrate that the speed of light hasn't changed for more than 1.7 billion years.This makes sense if we consider Entropy, the formation of galaxies during a time of high transition of infinite speed to lower, ie. the initial releasing of the carriage from the train. As the carriage slows the rate of change of speed, the passage of time, becomes less and less pronounced, an initial period of chaos which naturally settles down into a period of calm.
Am i on my own here?
Yes. The reason being is because you are trying to understand an advanced physics topic without having a grasp of basic physics first. I'd recommend having a read of something like Fundamentals of Physics in your spare time. I assure you that if you can grasp the material in that book, you will cringe at your statements in this thread if you then read back over them. 0 -
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Yes!Deleted User wrote: »Tachyons are hypothetical particles with imaginary mass. They don't break relativity by travelling faster than light as they travel backwards in time in the process.Deleted User wrote: »There is a lot to entangle there (pun intended), but I'll focus on the "spooky" bit you mentioned and leave the rest to others.
The spooky thing you are referring to is what is known as "spooky action at distance", i.e. quantum entanglement. When two particles that are created are entangled, something known as their "spin" will have opposite values. What these spin values actually are is inherently probabilistic, but if you measure the spin of one of the particles, you then therefore "instantly" know the spin of the other (regardless of the distance between both particles) as they are opposites, which seems to contradict the main premise of relativity, namely that nothing (including information) can travel faster than the speed of light.
However, this does not violate relativity. You do indeed instantly know what the spin of the second particle is, but this not because information has been transmitted instantaneously. The inherent probability of what the spin of the first particle is "entangled" with the inherent probability of what the spin of the other particle will be. Once the spin of the first particle is measured, the spin of the second particle is then known based on this probability. Information is not transmitted and, most importantly, entanglement cannot be used to intentionally transmit information at a speed greater than the speed of light as it is an inherently probabilistic phenomenon.
(It's obviously a bit more complicated than that, and I tried my best to not mention anything about a wave function collapsing, but hopefully that will do.) 0 -
Deleted User wrote: »It isn't, I'd recommend reading about the Movile Cave for example.
We don't use light to observe other massless particles, we use other means.
Again, this concept of needing to observe things for them to exist is incredibly flawed. By that logic the universe also did not exist before life formed.
It doesn't. What you're referring to is the observable universe. According to cosmic inflation theory for example, the universe's size is instead at least 3x10^23 times larger than the observable universe.
We know what the expansion speed (or rather, the expansion speed per distance) is, and it's much slower than the speed of light as I stated before. So your theory (and by theory, I mean your shower thought) is incorrect.
It can, but it doesn't, and we know this as a fact.
No there doesn't, and that doesn't even make sense.
That makes even less sense.
It doesn't. As I mentioned before, data from the Oklo natural reactors for example demonstrate that the speed of light hasn't changed for more than 1.7 billion years.
Yes. The reason being is because you are trying to understand an advanced physics topic without having a grasp of basic physics first. I'd recommend having a read of something like Fundamentals of Physics in your spare time. I assure you that if you can grasp the material in that book, you will cringe at your statements in this thread if you then read back over them.
Your reference to the Movile cave means you completely misunderstand my argument. Do you think i think that when i turn my house lights off and sit in the dark there is no time? That is ridiculous.
What i'm saying is that we would have no existence without a speed of light, that light which causes us to be able to observe anything. If it wasn't there neither would we.
No one is saying that the universe didn't exist before life formed, everything i have said already means that it must have. You are the one who is being contradictory, stating that the universe could in theory exist at a faster light speed, while stating it can't, but at the same time stating that the universe is far bigger than what can be observed?
If the universe consisted of a constant speed of light then it would surely be possible to observe it in it's entirety?
Cringing isn't in my dictionary, you may cringe for me if you like, i couldn't care less. But referring to life in a dark cave to rebut my argument would make me cringe more for you to be honest.0 -
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standardg60 wrote: »Your reference to the Movile cave means you completely misunderstand my argument. Do you think i think that when i turn my house lights off and sit in the dark there is no time? That is ridiculous.
No, I was replying to your statement that light is the only reason for existence.standardg60 wrote: »What i'm saying is that we would have no existence without a speed of light, that light which causes us to be able to observe anything. If it wasn't there neither would we.
If by we you mean humans then yes, we would not be here. If by we you mean the universe then no, the universe would still be here.standardg60 wrote: »You are the one who is being contradictory, stating that the universe could in theory exist at a faster light speed, while stating it can't, but at the same time stating that the universe is far bigger than what can be observed?
I stated that nothing within the universe can travel at a speed greater than the speed of light, but that the universe itself can expand at any speed and it has nothing to do with the speed of light nor does it even care that light exists. We know that this expansion rate is about 68km/s per megaparsec (H_0), i.e. that objects 1 megaparsec from us are receding from us at a rate of 68km/s, objects 2 megaparsec from us are receding from us at a rate of 136km/s etc., and objects a distance greater than c/H_0 from us are receding from us at a speed greater than the speed of light. Nothing about that is contradictory.standardg60 wrote: »If the universe consisted of a constant speed of light then it would surely be possible to observe it in it's entirety?
No, because as I explained above and many times already, the speed of light has nothing to do with how fast the universe is expanding.standardg60 wrote: »Cringing isn't in my dictionary, you may cringe for me if you like, i couldn't care less. But referring to life in a dark cave to rebut my argument would make me cringe more for you to be honest.
This is literally my area of expertise, I would highly recommend absorbing what I am saying if you are truly interested in understanding cosmology. When you make statements like "the speed of light (or what we measure it to be) is the difference between an infinite speed and the speed at which we are currently expanding" it demonstrates that you do not understand basic high school physics (or maths) and will therefore find it impossible to understand a more advanced topic. If you truly want to try to understand the universe and all its wonders, I would highly suggest starting from the bottom and working your way up. 0 -
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Deleted User wrote: »It isn't, I'd recommend reading about the Movile Cave for example.
We don't use light to observe other massless particles, we use other means.
Again, this concept of needing to observe things for them to exist is incredibly flawed. By that logic the universe also did not exist before life formed.
It doesn't. What you're referring to is the observable universe. According to cosmic inflation theory for example, the universe's size is instead at least 3x10^23 times larger than the observable universe.
We know what the expansion speed (or rather, the expansion speed per distance) is, and it's much slower than the speed of light as I stated before. So your theory (and by theory, I mean your shower thought) is incorrect.
It can, but it doesn't, and we know this as a fact.
No there doesn't, and that doesn't even make sense.
That makes even less sense.
It doesn't. As I mentioned before, data from the Oklo natural reactors for example demonstrate that the speed of light hasn't changed for more than 1.7 billion years.
Yes. The reason being is because you are trying to understand an advanced physics topic without having a grasp of basic physics first. I'd recommend having a read of something like Fundamentals of Physics in your spare time. I assure you that if you can grasp the material in that book, you will cringe at your statements in this thread if you then read back over them.Deleted User wrote: »No, I was replying to your statement that light is the only reason for existence.
If by we you mean humans then yes, we would not be here. If by we you mean the universe then no, the universe would still be here.
I stated that nothing within the universe can travel at a speed greater than the speed of light, but that the universe itself can expand at any speed and it has nothing to do with the speed of light nor does it even care that light exists. We know that this expansion rate is about 68km/s per megaparsec (H_0), i.e. that objects 1 megaparsec from us are receding from us at a rate of 68km/s, objects 2 megaparsec from us are receding from us at a rate of 136km/s etc., and objects a distance greater than c/H_0 from us are receding from us at a speed greater than the speed of light. Nothing about that is contradictory.
No, because as I explained above and many times already, the speed of light has nothing to do with how fast the universe is expanding.
This is literally my area of expertise, I would highly recommend absorbing what I am saying if you are truly interested in understanding cosmology. When you make statements like "the speed of light (or what we measure it to be) is the difference between an infinite speed and the speed at which we are currently expanding" it demonstrates that you do not understand basic high school physics (or maths) and will therefore find it impossible to understand a more advanced topic. If you truly want to try to understand the universe and all its wonders, I would highly suggest starting from the bottom and working your way up.
Thank you for being respectful with your reply, and i apologise if i seem disrespectful of your expertise.
I am just trying to answer questions that bother me. I asked a question earlier in the thread as to why we age, and was answered with an explanation as to how we age instead. I know that. It doesn't answer my question.
May i ask you, what is causing the universe to expand at a speed greater than the speed of light? Why isn't it a greater speed of light? What other force is causing it?
The concept of greater speeds of light explains why we age. If two cars set off for the same destination at different speeds, not only will the occupants of the slower car have aged more than the first, but what they observe to be reality out of the window will also be different. This is just an expansion of relativity.
E=mc to the power of two. How can it be squared if c is a constant, if it is a speed above which we cannot exist? This equation makes no allowance for time, it is a calculation which exists statically. As does the second theory, two people passing on trains through a station in opposite directions will observe each other differently depending on their speeds. But both will observe say a different length of grass a mile each side of the station.
Do you understand where i'm coming from?0 -
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Capt'n Midnight wrote: »
This thread.
I like that.
Now all you have to do is imagine being the needle. If you then run around the record at the same speed as it's turning you won't hear any music ie. you've reached the speed of light.
But what you can't perceive, and playing a record is a great analogy as you don't really notice it, is at the same time the needle is moving from the outer edge inwards.
That is time, that is what makes yesterday yesterday and today today. It is the needle moving inwards that actually plays the song. If it wasn't you would just hear the same line over and over, sure if you run faster and faster the line would play slower and slower, but it's still the same line!0 -
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