Advertisement
If you have a new account but are having problems posting or verifying your account, please email us on hello@boards.ie for help. Thanks :)
Hello all! Please ensure that you are posting a new thread or question in the appropriate forum. The Feedback forum is overwhelmed with questions that are having to be moved elsewhere. If you need help to verify your account contact hello@boards.ie

the speed of light question

Options
1234689

Comments

  • Options
    #152
    Mellor
    Registered Users Posts: 39,024 ✭✭✭✭Mellor


    Larbre34 wrote: »

    They then accelerated two cars on a collision course, both individually travelling at speed x. When they collided and the damage analysed, it was precisely consistent with one vehicle hitting the block at speed x, not at speed 2x.

    There's no expectation that it would cause the same damage as hitting a block wall as 2x the speed.

    In all example crashes, Cars went from top speed to zero. So force is the same in all examples. F=MA.
    Same impact. The greater energy in the two car crash is spread over two cars, so the total damage is 2x as much.

    If a car reared ended a car travelling at 0.1 mph. They would one car would slow down and one would speed up. In that case acceleration would be halved and damaged would be halved.

    Either you have the mistaken premise going in, or you are drawing a bad conclusion from their experiment. Happy to watch a video that counters the above if you link it.


  • Options
    #153
    standardg60
    Registered Users Posts: 4,258 ✭✭✭standardg60


    Speed of light is constant. We observe passage of time because things happen at different times.

    This is exactly the statement that i'm looking to answer. You're not explaining it, just making a statement. Why do things happen at different times?

    I'll try to explain my thinking again. Cut an elastic band and then hold the two ends together. You then pull one end away from the other at a theoretical speed of light. At the speed of light end there is no time (we know this), and at the stationary end there is no speed at all therefore there is no light/energy/time at all, just nothing.

    It is what's happening along the elastic expanding at various speeds between the two that gives rise to time. Each section takes a longer time to reach the point that the previous section passed, before they themselves eventually run out of energy and stop becoming dark.

    This is the universe to my mind. Everyone can wax lyrical about what they've been taught to be the accepted knowledge but as far as i know no one has discovered why we age. I'm happy with my own answer.


  • Options
    #154
    Nexytus
    Closed Accounts Posts: 154 ✭✭Nexytus


    standardg60 wrote: »
    Speed of light is constant. We observe passage of time because things happen at different times.

    This is exactly the statement that i'm looking to answer. You're not explaining it, just making a statement. Why do things happen at different times?

    I'll try to explain my thinking again. Cut an elastic band and then hold the two ends together. You then pull one end away from the other at a theoretical speed of light. At the speed of light end there is no time (we know this), and at the stationary end there is no speed at all therefore there is no light/energy/time at all, just nothing.

    It is what's happening along the elastic expanding at various speeds between the two that gives rise to time. Each section takes a longer time to reach the point that the previous section passed, before they themselves eventually run out of energy and stop becoming dark.

    This is the universe to my mind. Everyone can wax lyrical about what they've been taught to be the accepted knowledge but as far as i know no one has discovered why we age. I'm happy with my own answer.

    Does it need to be an elastic band? Or could it be a string?


  • Options
    #155
    standardg60
    Registered Users Posts: 4,258 ✭✭✭standardg60


    Nexytus wrote: »
    Does it need to be an elastic band? Or could it be a string?

    Laugh away.
    My theory is a plausible explanation as to why we are alone in the entire universe. Every other possible life-form exists at a different speed of light to ours, therefore connectivity between the two is not possible, or is it? Time will tell.
    As we already know there are particles which are visible at the speed of our light.
    Is it these particles which transfer our genes from one generation to the next?

    Eventually is it possible that beings will develop entirely made up of these time resistant particles who could theoretically make contact.

    Laugh again if you wish. At least i am trying to find an answer.


  • Options
    #156
    Nexytus
    Closed Accounts Posts: 154 ✭✭Nexytus


    standardg60 wrote: »
    at a different speed of light to ours,

    Maybe not different speeds of light but different particles and waves that do not interact with any of the particles that we are aware of and that make up our physical world. So there could be other worlds layered over ours but which we can never know of or interact with.


  • Advertisement
  • Options
    #157
    standardg60
    Registered Users Posts: 4,258 ✭✭✭standardg60


    Nexytus wrote: »
    Maybe not different speeds of light but different particles and waves that do not interact with any of the particles that we are aware of and that make up our physical world. So there could be other worlds layered over ours but which we can never know of or interact with.

    The only existing phenomenon that we are aware of is the affect of the speed of light on our perception of time. I don't know why we are striving to explain things that we don't understand on some other unknown concept.

    I am simply expanding on what we already know to be true and positing theories based on that.


  • Options
    #158
    Gregor Samsa
    Registered Users Posts: 8,908 ✭✭✭Gregor Samsa


    standardg60 wrote: »
    This is the universe to my mind. Everyone can wax lyrical about what they've been taught to be the accepted knowledge but as far as i know no one has discovered why we age. I'm happy with my own answer.

    It’s great to be curious and imaginative, and if you’re happy with your own answers, then that’s super - but there is actually an awful more than that at play with the theories and laws that physics comprises of. Things actually need to work in the real world. Things need to be experimental verified, not just once, but every time they’re tested. Things need to have a sound mathematical foundation and explanation. If you’re going to say that the speed of light is variable, then you need to have more proof and a better, more verifiable explanation for how the universe works than the folk that say it’s a constant. And there is a hell of a lot of evidence that it is a constant. Just saying “I don’t think it’s that way. I think it’s this way” really isn’t enough. If you’re going to dispense with c being a constant, you’re going to have to totally replace both Relativity and Quantum Mechanics with a whole new theory to explain everything that they currently do. That includes how computers work, how nuclear power works, how MRIs work, how the Large Hadron Collider operates, how to get a rocket off earth and to Mars. That’s quite a task.

    As for your comment on ageing, each time a cell replicates, tiny errors are introduced into the genes and proteins created in the new version of the cell. Over the course of many replications, these errors damage the efficiency of the cell, and it’s ability to replicate, resulting in the effects of ageing, and ultimately death. We age at the cellular level. But almost everything in the universe ages and decays. Stars run out of hydrogen and explode and eventually turn cool. Compounds breaks down into their constituent elements. Elements themselves decay into isotopes. Subatomic particles decay into more fundamental particles. Eventually, in about 10,​000,​000,​000,​000,​000,​000,​000,​000,​000,​000,​000,​000,​000,​000,​000,​000,​000,​000,​000,​000,​000,​000,​000,​000,​000,​000,​000,​000,​000,​000,​000,​000,​000 years time (that’s a Gogol years - 1 with a hundred zeros) all that will be left of the entire universe is photons, neutrinos, electrons, and positrons flying about a space so large that they very rarely even encounter each other.

    Entropy is one of the few qualities of the universe that is dependent on the arrow of time. Most other processes work just as well forwards as backwards. The universe (as a whole) moves from a state of low entropy to maximum entropy, and cannot move the other way. Say you make a cup. You put energy into a mass of potters clay to create it. It’s an structured object with low entropy. You then drop it on the floor. It smashes. It’s now a random pile of chips and flakes and dust. It’s disordered and now has higher entropy. The pieces of the cup can’t spontaneously jump back up to being an intact cup again. That’s the arrow of time - in an isolated system (which the universe is) entropy only goes one way, low to high, past to future.

    That end state of the universe - cold and dark with all those photons, neutrinos, electrons, and positrons flying about a space so large that they very rarely even encounter each other - that’s the state of maximum entropy everything in the universe is ultimately heading towards.


  • Options
    #159
    Gregor Samsa
    Registered Users Posts: 8,908 ✭✭✭Gregor Samsa


    Nexytus wrote: »
    Does it need to be an elastic band? Or could it be a string?
    standardg60 wrote: »
    Laugh away.

    Nexytus’ comment was actually quite smart, given the topic. Although you’d have to be aware of String Theory to get it.

    https://en.m.wikipedia.org/wiki/String_theory


  • Options
    #160
    y0ssar1an22
    Registered Users Posts: 16,028 ✭✭✭✭y0ssar1an22


    my understanding is pretty rudimentary, but based upon sound maths; f = ma and the like. so newton's laws' as mentioned previously.

    i suppose (i know) i dont have a clue.

    although, i think i have a good analogy: imagine running into the wind. walk into the wind, you feel it; its a resistance against you. Sprint into the same wind, and its alot harder. It seems the faster you go against it, the higher the resistance comes.

    but in that case, there is conservation.

    i dunno, this confuses me no end!

    great to see people debating physics though!

    i think the end result is that we think we know, but we don't really know. otherwise, why change rules at a certain speed?

    i can give you a formula for every prime number to 19. my formula breaks down at 23. :P

    the point is; i now think i know all the primes, whereas i dont at all.

    could it be, that we really dont have a clue?


  • Options
    #161
    Gregor Samsa
    Registered Users Posts: 8,908 ✭✭✭Gregor Samsa


    y0ssar1an22 wrote: »
    i think the end result is that we think we know, but we don't really know. otherwise, why change rules at a certain speed?

    But we don't change the rules at a certain speed. The equations work equally well for any speed. It's just that there's a hard limit, and for very good reasons. To break that hard limit would require more than infinite energy, which can't exist. There's very sound theoretical, mathematical and practical reasons for it being both a constant and a limit.

    You can't say "we don't really know" if you don't actually know what we actually do know in the first place.

    Physics isn't like philosophy. In philosophy, you can come up with an idea and argue for it. Or against it. Whether it stands or not is based on some external assumptions and how internally consistent it is. In physics, when you come up with an idea, it actually has to work. It has to explain something about what we see and experience, and it has to be experimentally verifiable. Otherwise it's utterly pointless.

    Both Newton's theory of gravity and Einstein's general theory of relativity predict that light will bend around a massive object, a phenomenon known as gravitational lensing. Neither of them witnessed or experienced this, it was merely something that their equations say should happen. It wasn't until 1919 that it was first experimentally observed in real life. It's now used by astronomers in observing the distant universe. If it had been shown not to occur, then both Newton's theory of gravity and Einstein's general theory of relativity would have been shown to be fundamentally flawed, and they would have been relegated to the scrapheap of theories, like Aristotelian physics, the Copernican system the Steady State theory. But they weren't. This is just one of the many examples of experimental evidence upholding the theories. All it takes is one verified falsification to unseat a theory. (in fact, Newton's theory of gravity has been proven to to be wrong, but because it works well at approximate values at speed that aren't close to the speed of light, it's still useful in day-to-day calculations and explanations).

    That's not to say that all questions have been answered, or that the theories are perfect. They're not, and there are gaps, and people are constantly working on new theories to fill those. But we do know a lot, and any new theory that's going to replace and improve upon what we have now has to take into account what we already know and observe. Relativity and the various theories of quantum mechanics will be superseded by something someday - but that thing that superseded them not only has to work as well as them, but has to work better.

    It's not just a matter of thinking "oh, maybe it's this way, who really knows". We do know, and we know it actually has to work.


  • Advertisement
  • Options
    #162
    Mellor
    Registered Users Posts: 39,024 ✭✭✭✭Mellor


    standardg60 wrote: »
    This is exactly the statement that i'm looking to answer. You're not explaining it, just making a statement. Why do things happen at different times?
    That statement, as simplistic as it seams, is all that is needed to explain your query.

    You are reading this post now, and not the last time you were online because it didn't exist then. Nothing to do with a variable speed of light. If light was 10x faster or slower, it wouldn't have made a significant difference to when it got to you.
    I'll try to explain my thinking again. Cut an elastic band and then hold the two ends together. You then pull one end away from the other at a theoretical speed of light. At the speed of light end there is no time (we know this), and at the stationary end there is no speed at all therefore there is no light/energy/time at all, just nothing.
    It's the part at the end if bold that is where this goes wrong. And undermines everything afterthat.
    If something is stationary, that doesn't mean there is no light/energy/time. Not sure where you are getting that from. It that were the case as some as anything stopped moving it would ceases to exist.
    It is what's happening along the elastic expanding at various speeds between the two that gives rise to time.

    No it isn't.
    Each section takes a longer time to reach the point that the previous section passed, before they themselves eventually run out of energy and stop becoming dark.
    They take a longer time to reach the point because the are moving at a different speed, ie not at the speed of light. Taking longer to reach the point just means they take longer. Same way that a car driving slower takes longer to get from A to B. None of that.
    This is the universe to my mind. Everyone can wax lyrical about what they've been taught to be the accepted knowledge but as far as i know no one has discovered why we age. I'm happy with my own answer.

    We know why we age. And nothing in your theory would offer a and explanation for why we age and for time.
    standardg60 wrote: »
    Laugh away.
    My theory is a plausible explanation as to why we are alone in the entire universe. Every other possible life-form exists at a different speed of light to ours, therefore connectivity between the two is not possible, or is it?
    If another lifeform operated on a different speed of light. It wouldn't stop us seeing or interacting with them. We wouldn't even perceive a difference face to face.
    As we already know there are particles which are visible at the speed of our light.Is it these particles which transfer our genes from one generation to the next?
    No. Genes are transfer via reproductive cells not photons.


  • Options
    #163
    Interested Observer
    Registered Users Posts: 13,004 ✭✭✭✭Interested Observer


    Gregor Samsa wrote: »
    Most particles do have mass, but photons and gluons don't. Gravitons, if they exist, wouldn't have mass either. Neutros have so little mass that it's currently experimentally impossible to differentiate between their speed and the speed of light, and since we don't know exactly what their mass is, we can't calculate their actual speed, but it's been shown that they must have some mass, so their speed must be less than c.

    This is fascinating. I am a complete layperson in all this but (I assume you mean neutrino) the neutrino was hypothesised initially because there was some element missing from some equation right, i.e. (I know this isn't it but a thought experiment) when you split an atom the mass of the two halves didn't add up to the mass of the original atom, so you had your original atom = two halves + energy + whatever else.

    So there's no zero sum out there, that says the neutrino, even though we can't detect it, HAS to be this certain portion of the mass/energy/whatever that comes from some reaction or process, because we've accounted for everything else?

    I don't know if any of that makes sense.


  • Options
    #164
    Gregor Samsa
    Registered Users Posts: 8,908 ✭✭✭Gregor Samsa


    standardg60 wrote: »
    Laugh away.
    My theory is a plausible explanation as to why we are alone in the entire universe. Every other possible life-form exists at a different speed of light to ours, therefore connectivity between the two is not possible, or is it? Time will tell.
    As we already know there are particles which are visible at the speed of our light.
    Is it these particles which transfer our genes from one generation to the next?

    Eventually is it possible that beings will develop entirely made up of these time resistant particles who could theoretically make contact.

    Laugh again if you wish. At least i am trying to find an answer.

    Again, there's not much actually true about the assumptions you're basing any of your thoughts on.

    We don't know that we're alone in the universe. That's an open question that currently doesn't have an answer. Whether we are or not has nothing to do with the speed of light, though.

    Saying "there are particles which are visible at the speed of our light." is a statement that makes absolutely no sense. Fundamental particles aren't "visible". They're not little balls, or dust, or anything like that. Light can't "bounce off" an electron and into your eye for you to see it.

    As explained already, genes are transferred from one generation to the next by cell division, which again is nothing to do with the speed of light, particles or particle physics. That is something that can be readily observed visually with a microscope. There's no mystery to it at all.

    Imagine two people had to fly to China to ask a person a question - to find an answer. One of them studied chinese language and customs. They didn't know everything, but they knew a lot, and had passed exams that independently verified their knowledge. Their plan was to meet the person, ask the question in Chinese, and thus receive the answer and understand it to the best of their abilities and knowledge.

    The other just decided that Chinese was random noises, because they claim who really can say that it's an actual language - it sounds like random gibberish to them. The night before their flight they watched a Japanese movie, and practiced making random noises that sounded vaguely to their ears like the dialogue in the movie. Their plan was to go to the Chinese person and make the random noises at them, and the person will make random noises back, they he'll be able to just figure out what the random noises mean, because that theory makes sense to them, and they're not going to just follow what other people have been taught to be the accepted knowledge of the Chinese language (even though it can be demonstrated to exist).

    Which of these two people would you say is actually trying to find the answer in any meaningful way?


  • Options
    #165
    Gregor Samsa
    Registered Users Posts: 8,908 ✭✭✭Gregor Samsa


    Interested Observer wrote: »
    This is fascinating. I am a complete layperson in all this but (I assume you mean neutrino) the neutrino was hypothesised initially because there was some element missing from some equation right, i.e. (I know this isn't it but a thought experiment) when you split an atom the mass of the two halves didn't add up to the mass of the original atom, so you had your original atom = two halves + energy + whatever else.

    So there's no zero sum out there, that says the neutrino, even though we can't detect it, HAS to be this certain portion of the mass/energy/whatever that comes from some reaction or process, because we've accounted for everything else?

    I don't know if any of that makes sense.

    Sorry, yeah, that was a typo, I did mean to type neutrino.

    There's a whole question of missing mass in the universe. We know from the way gravity works that what we observe happening in the motion or galaxies should not be happening given the amount of stars and gas we see in them. Either the theory is very wrong, or there's mass - a lot of mass - that we can't detect. Now, the theory can't be totally wrong because it works so well. And there's a lot of experimental and observational evidence that there is missing mass. It's an ongoing investigation, but there's various candidates for it that are theoretically possible - but they haven't been detected yet. There's experiments underway and proposed to determine if any of these candidates actually exist.

    As you say, neutrinos were proposed as having to exist in 1930 to account for how beta decay in atoms works, before they were observed. There was a bit missing from the observations and calculations, and something had to fill it. Thus the neutrino was proposed (although confusingly, Pauli called it a "neutron". In 1932, Chadwick discovered a much more massive neutral nuclear particle inside atoms, and he decided to call it the "neutron". The diminutive term "neutrino" was then coined for the particle Pauli proposed, as it was expected to be much less massive (or have no mass).

    It wasn't until 1956 that neutrinos were actually detected in an experiment, and 1965 that they were detected in nature. They interact with matter so little that they're exceptionally difficult to detect, but they're everywhere. It's estimated that each second, 65 billion of them pass though every square centimeter of your body surface - and that's just the ones coming from the sun - they're also coming from objects in the rest of the universe and indeed the Big Bang itself.

    When it was discovered that neutrinos had some mass (albeit very, very, very little), then it was proposed that they were a candidate for some of this missing mass of the universe. It's since been shown that while they certainly do make up some of the missing mass, it's only a very small proportion. The rest of it - the vast bulk of it - is still subject to ongoing investigation.

    So like the way the neutrino was proposed as having to exist before it was actually discovered, other forms of matter (mass) and energy that we don't know about yet must also exist. But, they must exist within some very clearly defined parameters, so this isn't carte blanche for people to propose all kinds of fanciful notions. There's a very specific gap that they must fill in the theories and observations,.


  • Options
    #166
    standardg60
    Registered Users Posts: 4,258 ✭✭✭standardg60


    Gregor Samsa wrote: »
    Again, there's not much actually true about the assumptions you're basing any of your thoughts on.

    We don't know that we're alone in the universe. That's an open question that currently doesn't have an answer. Whether we are or not has nothing to do with the speed of light, though.

    Saying "there are particles which are visible at the speed of our light." is a statement that makes absolutely no sense. Fundamental particles aren't "visible". They're not little balls, or dust, or anything like that. Light can't "bounce off" an electron and into your eye for you to see it.

    As explained already, genes are transferred from one generation to the next by cell division, which again is nothing to do with the speed of light, particles or particle physics. That is something that can be readily observed visually with a microscope. There's no mystery to it at all.

    Imagine two people had to fly to China to ask a person a question - to find an answer. One of them studied chinese language and customs. They didn't know everything, but they knew a lot, and had passed exams that independently verified their knowledge. Their plan was to meet the person, ask the question in Chinese, and thus receive the answer and understand it to the best of their abilities and knowledge.

    The other just decided that Chinese was random noises, because they claim who really can say that it's an actual language - it sounds like random gibberish to them. The night before their flight they watched a Japanese movie, and practiced making random noises that sounded vaguely to their ears like the dialogue in the movie. Their plan was to go to the Chinese person and make the random noises at them, and the person will make random noises back, they he'll be able to just figure out what the random noises mean, because that theory makes sense to them, and they're not going to just follow what other people have been taught to be the accepted knowledge of the Chinese language (even though it can be demonstrated to exist).

    Which of these two people would you say is actually trying to find the answer in any meaningful way?

    If you wanted to call me an idiot then you should have just said so.
    It would have saved you having to type out your drawn out analogy and of me having to read it and then arriving at the same conclusion.


  • Options
    #167
    standardg60
    Registered Users Posts: 4,258 ✭✭✭standardg60


    Mellor wrote: »
    That statement, as simplistic as it seams, is all that is needed to explain your query.

    You are reading this post now, and not the last time you were online because it didn't exist then. Nothing to do with a variable speed of light. If light was 10x faster or slower, it wouldn't have made a significant difference to when it got to you.


    It's the part at the end if bold that is where this goes wrong. And undermines everything afterthat.
    If something is stationary, that doesn't mean there is no light/energy/time. Not sure where you are getting that from. It that were the case as some as anything stopped moving it would ceases to exist.



    No it isn't.


    They take a longer time to reach the point because the are moving at a different speed, ie not at the speed of light. Taking longer to reach the point just means they take longer. Same way that a car driving slower takes longer to get from A to B. None of that.



    We know why we age. And nothing in your theory would offer a and explanation for why we age and for time.


    If another lifeform operated on a different speed of light. It wouldn't stop us seeing or interacting with them. We wouldn't even perceive a difference face to face.


    No. Genes are transfer via reproductive cells not photons.

    Thanks for taking the 'time' to respond to each of my points in turn. I'll respond likewise.

    I know i'm only reading it now, and i know it didn't exist yesterday. What i'm asking, thinking, is why we are on this trajectory of what we perceive to be time, what is causing it?

    What i mean is all light has left that point. My thinking is that nothing can exist without the movement of light because that is what creates existence. If there is no light moving there is no time, if there is no time there is no existence.

    What gives rise to time then if it's not the movement of light?

    Accepting that they just 'take longer' is exactly what i don't accept. If one car reaches B instantaneously, nothing has 'happened' to the occupants. Meanwhile the occupants of the slower car have aged, reproduced, died, and never arrived at all, but their descendants (genes, DNA) did.

    As far as i know we don't know why we age, just how we age. Yes cells reproduce and degrade over time but what causes them to reproduce at all? What external phenomenon are they responding to?

    If another life form where out there existing in a different speed of light to ours we would be invisible to each other unless one had developed the ability to exist within the other's light speed. That they were entirely made up of cells which didn't need to reproduce in response to the passing of time.

    Why do we reproduce at all? For me reproduction is life's/ Existence's naturally developed defence against the passing of time. Saying it's merely the reproduction of cells ( which again is saying how it happens rather than why) does not answer the question i ask.

    I'm possibly/ probably talking a load of nonsense here but i thought it was time to put my thoughts in writing!


  • Options
    #168
    y0ssar1an22
    Registered Users Posts: 16,028 ✭✭✭✭y0ssar1an22


    Gregor Samsa wrote: »
    But we don't change the rules at a certain speed. The equations work equally well for any speed. It's just that there's a hard limit, and for very good reasons. To break that hard limit would require more than infinite energy, which can't exist. There's very sound theoretical, mathematical and practical reasons for it being both a constant and a limit.

    You can't say "we don't really know" if you don't actually know what we actually do know in the first place.

    Physics isn't like philosophy. In philosophy, you can come up with an idea and argue for it. Or against it. Whether it stands or not is based on some external assumptions and how internally consistent it is. In physics, when you come up with an idea, it actually has to work. It has to explain something about what we see and experience, and it has to be experimentally verifiable. Otherwise it's utterly pointless.

    Both Newton's theory of gravity and Einstein's general theory of relativity predict that light will bend around a massive object, a phenomenon known as gravitational lensing. Neither of them witnessed or experienced this, it was merely something that their equations say should happen. It wasn't until 1919 that it was first experimentally observed in real life. It's now used by astronomers in observing the distant universe. If it had been shown not to occur, then both Newton's theory of gravity and Einstein's general theory of relativity would have been shown to be fundamentally flawed, and they would have been relegated to the scrapheap of theories, like Aristotelian physics, the Copernican system the Steady State theory. But they weren't. This is just one of the many examples of experimental evidence upholding the theories. All it takes is one verified falsification to unseat a theory. (in fact, Newton's theory of gravity has been proven to to be wrong, but because it works well at approximate values at speed that aren't close to the speed of light, it's still useful in day-to-day calculations and explanations).

    That's not to say that all questions have been answered, or that the theories are perfect. They're not, and there are gaps, and people are constantly working on new theories to fill those. But we do know a lot, and any new theory that's going to replace and improve upon what we have now has to take into account what we already know and observe. Relativity and the various theories of quantum mechanics will be superseded by something someday - but that thing that superseded them not only has to work as well as them, but has to work better.

    It's not just a matter of thinking "oh, maybe it's this way, who really knows". We do know, and we know it actually has to work.

    so this is where my confusion lies:

    A and B moving towards each other at a velocity of 10m/s. my understanding is this: the are approaching each other at (2)(10m/s) = 20m/s.

    I guess my question is: is that true?

    following on from that; if it is true, why not apply the same maths to light?


  • Options
    #169
    Capt'n Midnight
    Moderators, Recreation & Hobbies Moderators, Science, Health & Environment Moderators, Technology & Internet Moderators Posts: 90,711 Mod ✭✭✭✭Capt'n Midnight


    y0ssar1an22 wrote: »
    A and B moving towards each other at a velocity of 10m/s. my understanding is this: the are approaching each other at (2)(10m/s) = 20m/s.
    Assume A and B each weigh 1Kg. Kinetic energy is a half mass times velocity squared.

    So A and B have a half times 1kg times 10 squared (100/2) so 50 Joules each. 100 Joules total for the two of them

    Keeping A still and moving B twice as fast you get 0 joules for A because it isn't moving.
    And B is half 1kg times 20 squared so (400/2) is 200 Joules because energy is conserved :confused:

    hmm....


  • Options
    #170
    [Deleted User]
    Posts: 0 ✭ [Deleted User]


    y0ssar1an22 wrote: »
    so this is where my confusion lies:

    A and B moving towards each other at a velocity of 10m/s. my understanding is this: the are approaching each other at (2)(10m/s) = 20m/s.

    I guess my question is: is that true?

    following on from that; if it is true, why not apply the same maths to light?

    Nope, I have it answered that here. :)


  • Options
    #171
    [Deleted User]
    Posts: 0 ✭ [Deleted User]


    standardg60 wrote: »
    What i mean is all light has left that point. My thinking is that nothing can exist without the movement of light because that is what creates existence. If there is no light moving there is no time, if there is no time there is no existence.

    Light does not create existence. The universe would also exist if light did not exist.

    I think you are getting confused by the misnomer "the speed of light". We call it as such because light was the first known particle to travel at that speed. However, all massless particles travel at the speed (including, for example, gravitons) and light is not special in that sense. Why are you so fascinated by light and not gravitons?


  • Advertisement
  • Options
    #172
    y0ssar1an22
    Registered Users Posts: 16,028 ✭✭✭✭y0ssar1an22


    Deleted User wrote: »
    Nope, they aren't. They are approaching each other at 199.999999999998285... km/h according to relativistic velocity addition.
    https://en.wikipedia.org/wiki/Velocity-addition_formula

    I think you are confusing the idea that relativistic equations only apply when things are moving fast. In fact, they always apply, and Newtonian mechanics is simply a good approximation at low speeds.

    Here is a graph of the above equation of your scenario of the speed of both cars being the same (u=v). Red is Newtonian and blue is Einstein. The x-axis is the speed of each car relative to a stationary observer (in units of speed of light) and the y-axis is the speed of each car according to each other (also in units of speed of light).

    As each car approaches the speed of light relative to the observer, the speed of one car relative to the other incorrectly approaches twice the speed of light according to Newton (2 on the y-axis) and correctly approaches the speed of light according to Einstein (1 on the y-axis). Also, note that both agree well at low speeds and it's not that the relativistic equations "kick in" at some arbitrary high speed.

    4IRzD.jpg

    so therefore, newtons equations dont hold true?

    lets reduce it to the most basic...a binary choice.....if one holds true, surely the other cant?


  • Options
    #173
    [Deleted User]
    Posts: 0 ✭ [Deleted User]


    y0ssar1an22 wrote: »
    so therefore, newtons equations dont hold true?

    lets reduce it to the most basic...a binary choice.....if one holds true, surely the other cant?

    Yes, what you are referring to as Newton's equations are not true, they are just very good approximations at our everyday, low speeds. :)


  • Options
    #174
    Gregor Samsa
    Registered Users Posts: 8,908 ✭✭✭Gregor Samsa


    y0ssar1an22 wrote: »
    so this is where my confusion lies:

    A and B moving towards each other at a velocity of 10m/s. my understanding is this: the are approaching each other at (2)(10m/s) = 20m/s.

    I guess my question is: is that true?

    following on from that; if it is true, why not apply the same maths to light?

    See, that’s a Newtonian equation. And while it works well as an approximation at relatively low speeds (the result of the example you gave us correct) it doesn’t work as you approach the speed of light. That’s the problem with Newtonian mechanics - it’s not actually universally right. It breaks down at high speeds (and in other ways too). Relativity supersedes it because it works correctly at all speeds and conditions up to and including the speed of light.

    Here’s the explanation with the correct Relativity equation that works at any speed, that shows you don’t (can’t) end up with 2c.

    https://www.physicscentral.com/experiment/askaphysicist/physics-answer.cfm?uid=20130130105151

    Newtonian mechanics is wrong because it doesn’t take into account the actual physical effects and conditions that travelling near the speed of light produce or require. But it happens work at lower speeds because those effects aren’t detectable there.


  • Options
    #175
    blinding
    Banned (with Prison Access) Posts: 7,466 ✭✭✭blinding


    Is there a speed of Dark ?

    How long does it take the Darkside to get you ?


  • Options
    #176
    Quantum Erasure
    Registered Users Posts: 8,166 ✭✭✭Quantum Erasure


    blinding wrote: »
    Is there a speed of Dark ?

    About a foot per nanosecond in the opposite direction


  • Options
    #177
    Mellor
    Registered Users Posts: 39,024 ✭✭✭✭Mellor


    standardg60 wrote: »
    I know i'm only reading it now, and i know it didn't exist yesterday. What i'm asking, thinking, is why we are on this trajectory of what we perceive to be time, what is causing it?
    It’s caused, precisely by the passage of time.
    What i mean is all light has left that point. My thinking is that nothing can exist without the movement of light because that is what creates existence. If there is no light moving there is no time, if there is no time there is no existence.
    Light doesn’t create existence or time.
    What gives rise to time then if it's not the movement of light?
    It’s simply something that happens. Regardless of light. If you entered a room in total darkness with zero light. Time would still pass.
    Accepting that they just 'take longer' is exactly what i don't accept. If one car reaches B instantaneously, nothing has 'happened' to the occupants. Meanwhile the occupants of the slower car have aged, reproduced, died, and never arrived at all, but their descendants (genes, DNA) did.
    If they are travelling at different speeds the cars aren’t connected. There is nothing different about your example as a car at 20km/h and another at 80km/h.

    As far as i know we don't know why we age, just how we age. Yes cells reproduce and degrade over time but what causes them to reproduce at all? What external phenomenon are they responding to?
    No phenomenon. External or internal required.
    This is basic biology, not physics btw.
    If another life form where out there existing in a different speed of light to ours we would be invisible to each other unless one had developed the ability to exist within the other's light speed.
    No we wouldn’t.
    If you emitted lighted light twice as slow, I would see you just fine.
    You seem to misunderstand what “the speed of light” actually means.


    That they were entirely made up of cells which didn't need to reproduce in response to the passing of time.

    Why do we reproduce at all? For me reproduction is life's/ Existence's naturally developed defence against the passing of time. Saying it's merely the reproduction of cells ( which again is saying how it happens rather than why) does not answer the question i ask.
    Reproduction doesn’t defend time. No more than condone allow you to time travel.


  • Options
    #178
    Panrich
    Registered Users Posts: 3,763 ✭✭✭Panrich


    standardg60 wrote: »
    as far as i know no one has discovered why we age. I'm happy with my own answer.

    Without wanting to take the thread off topic, we age because our raison d’etre is to reproduce and pass on our genes. Younger fitter specimens pass on better less compromised copies. We age and die much like the flowers that wither in the autumn once their reproductive season is over.


  • Options
    #179
    Gregor Samsa
    Registered Users Posts: 8,908 ✭✭✭Gregor Samsa


    standardg60 wrote: »
    What gives rise to time then if it's not the movement of light?

    Time was created in the Big Bang, along with space. It’s an inherent property of the universe. Even if there was no light, no matter, no observers, there would still be time in this universe. The notion of “before” the Big Bang makes no sense, because that’s when time itself started.

    The perception of the passage of time is relative, and is influenced by the relative speed of the observers, but time itself is an actual inherent property of the universe.

    Here’s a good explanation of the whats and the whys: https://phys.org/news/2016-02-what-is-time-and-why.html

    Now the question “why is time one of the dimensions of this universe?” Is a good one. It’s possible that the very early universe had more dimensions than the 4 we currently observe. Many forms of String Theory propose that there’s multiple other dimensions in this universe, but they’re wrapped up at a very small scale. Why time was one of the ones that remained at the macro level is an area of continuing investigation.

    (Just remember what a “dimension” is. It’s not an “alternate universe” or existence. The idea of “travelling to another dimension” makes no sense.the first 3 Dimensions are exactly what they are when someone describes the dimensions of a book case, or coordinates on a map: length/breadth/height or longitude/latitude/altitude, or position on the x,y,z axis. Time is the 4th dimension in space time. Say you want to meet someone at any location in the universe. You need to know the “where” (x,y,z coordinates) but also the “when” (time). Various versions forms of Sting Theory propose that there’s more types of coordinates (dimensions) at very small scales.)


  • Options
    #180
    Panthro
    Registered Users Posts: 14,684 ✭✭✭✭Panthro


    bluewolf wrote: »
    There's a different formula for relativistic objects
    Newton is out the window

    Wasn't wearing a seat belt I take it.


  • Advertisement
  • Options
    #181
    Junkyard Tom
    Registered Users Posts: 10,117 ✭✭✭✭Junkyard Tom


    y0ssar1an22 wrote: »
    1: car A and car B have a velocity towards each other of 100 kph.

    Okay...
    they are approaching each other is 200kph.

    They are not. They're both approaching a collision point in at 100kph.


Advertisement