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the speed of light question

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    #92
    Capt'n Midnight
    Moderators, Recreation & Hobbies Moderators, Science, Health & Environment Moderators, Technology & Internet Moderators Posts: 90,700 Mod ✭✭✭✭Capt'n Midnight


    fillup wrote: »
    They had to cover rough terrain to measure the distance between their measuring apparatus- they couldn't run a 35km measuring tape between the two sites.
    But they could use a laser rangefinder.


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    #93
    standardg60
    Registered Users Posts: 4,242 ✭✭✭standardg60


    This is the most rational explanation of what is life that i can conjure up in my own head.
    The universe is an infinite number of carriages that leaves a train station at an infinite speed.
    Immediately one carriage is unhooked after another and is left to drift under it's own initial energy.
    Each carriage will eventually pass through a point in time occupied by the train, it is this interval that is existence, an experience or phenomenon that exists between two speeds of light.
    But no two carriages will ever meet again, each will stop at a particular point along the track, and when they stop existence will cease. It is only their movement relative to the train which creates time.
    Is there therefore something that transfers from the last carriage to the second last that leads to the progress of mankind?
    Is that what procreation is? A transfer of something which is resistant to time.


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    #94
    [Deleted User]
    Posts: 0 ✭ [Deleted User]


    standardg60 wrote: »
    This is the most rational explanation of what is life that i can conjure up in my own head.
    The universe is an infinite number of carriages that leaves a train station at an infinite speed.
    Immediately one carriage is unhooked after another and is left to drift under it's own initial energy.
    Each carriage will eventually pass through a point in time occupied by the train, it is this interval that is existence, an experience or phenomenon that exists between two speeds of light.
    But no two carriages will ever meet again, each will stop at a particular point along the track, and when they stop existence will cease. It is only their movement relative to the train which creates time.
    Is there therefore something that transfers from the last carriage to the second last that leads to the progress of mankind?
    Is that what procreation is? A transfer of something which is resistant to time.

    I can only respond to this using the language of astrophysics rather than in layman's terms, so I apologise if what I'm about to say sounds a bit confusing and complicated.

    Please put down the blunt.


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    #95
    standardg60
    Registered Users Posts: 4,242 ✭✭✭standardg60


    Deleted User wrote: »
    I think you are getting a bit confused between the speed of light and the speed of the expansion of the universe. They are not the same thing, but that does not suggest that the speed of light is not constant. The speed of the expansion of the universe is instead determined by the Hubble constant (~68km/s per megaparsec).

    As for your last sentence, the outer parts of the universe (beyond the Hubble radius) are actually receding at a speed greater than the speed of light. Therefore, any light emitted outside of this radius can never and will never be detected by us.

    If the universe is expanding at a speed greater than the speed of light is that not confirmation that it is not constant?


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    #96
    [Deleted User]
    Posts: 0 ✭ [Deleted User]


    Time.

    Spend an hour with the most attractive woman(man, depending) and speed 30 seconds with your hand over a hot flame. One will seem fleeting, the other will feel interminable.

    I think it was Joxer down the pub explained it to me last Christmas.


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    #97
    [Deleted User]
    Posts: 0 ✭ [Deleted User]


    standardg60 wrote: »
    If the universe is expanding at a speed greater than the speed of light is that not confirmation that it is not constant?

    No. If I am walking at a particular constant speed, it does not mean the car next to me is moving at a constant speed. They are not related to each other.

    The speed of the expansion of the universe is different at different distances from us, but that has nothing to do with the speed of light.


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    #98
    blinding
    Banned (with Prison Access) Posts: 7,466 ✭✭✭blinding


    Is the time in a Book / DVD real if nobody is reading / watching the Book / DVD ? ?


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    #99
    standardg60
    Registered Users Posts: 4,242 ✭✭✭standardg60


    Deleted User wrote: »
    No. If I am walking at a particular constant speed, it does not mean the car next to me is moving at a constant speed. They are not related to each other.

    The speed of the expansion of the universe is different at different distances from us, but that has nothing to do with the speed of light.

    How can it not?
    The universe is an expansion of light, and life is dependent on that very expansion.
    If the universe ceases to expand, then existence ceases.
    It is the difference between the rates of expansion from where we are to the edge which gives rise to time.


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    #100
    PMBC
    Registered Users Posts: 1,102 ✭✭✭PMBC


    Gregor Samsa wrote: »
    There’s an interesting phenomenon called time dilation that happens the faster you travel. It’s not something you can notice at human speeds (unless you’re measuring with an incredibly accurate atomic clock), but the faster you go, the slower time goes relative to observers travelling slower than you. If you go at 90% of the speed of light, your perception and experience of time is half of a static observer. You’ll actually age half as slow as them. If you travel at the speed of light, for you, time stops, and you’re therefore bot able to observe anything in the universe. Basically at that speed, for you, nothing else exists except yourself, and time is infinite.

    If you have any mass, your mass will also become infinite at the speed of light. It would therefore take an infinite amount of energy to get you there. Your length also reduces in the axis you’re travelling the faster you go. And again, the effect is infinite at the SOL.

    So, if you were a solid object of any size, it would take infinite energy to get you to the speed of light, and once you got there, you’d have infinite mass, zero length, time would stop and to you the universe would cease to exist. This clearly means that it’s impossible for anything with mass to travel at the speed of light. It also shows that nothing can travel faster than light (it would take more than infinite energy to do it, which can’t exist, and you’d end up more than infinitely massive and less than zero in length - again, things that just can’t happen)

    Fortunately, photons and other particles that do travel at that speed don’t have any mass, so they don’t have to worry about the physical effects.

    What about tachyons?


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    #101
    Curious_Case
    Registered Users Posts: 1,525 ✭✭✭Curious_Case


    y0ssar1an22 wrote: »
    a question that has puzzled me for a while...

    1: car A and car B have a velocity towards each other of 100 kph. they are approaching each other is 200kph.

    2: if car A and car B are doing the same, but at the speed of light why are they not approaching each other at (2)(speed of light)?

    if the rules of physics hold for scenario 1, why not scarios 2?

    is there a simple explanation here?

    i dunno, maybe we just don't have an answer?

    Simples

    If, for instance, the 2 cars were in a dragster race and both hurtled down the track at C (velocity of light) then they would maintain position relative to each other and neither would be moving relative to the other. Therefore they are approaching/separating at ZERO velocity but nevertheless they are, absolutely, both travelling at C.

    Similarly, if they are approaching each other (both travelling on the same trajectory) then they are, absolutely, closing the distance at a velocity of TWICE C. Nevertheless, neither of them are travelling at anything other than C.

    Velocity is defined as speed in a straight line.
    As the cars velocities are steady @ C, acceleration is zero in both cases.


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    #102
    Capt'n Midnight
    Moderators, Recreation & Hobbies Moderators, Science, Health & Environment Moderators, Technology & Internet Moderators Posts: 90,700 Mod ✭✭✭✭Capt'n Midnight


    standardg60 wrote: »
    It has to be necessary. If we can see that the universe is expanding, then it must be expanding at a different speed to ours. If we were expanding at the same speed then we wouldn't see it.
    For the first 300,000 thousand years after the big bang the universe expanded faster than the speed of light through the high density of matter in the universe then.

    After that the density dropped and light was faster.

    So it's possible the universe is bigger than we can observe. In a few billion years we will know if we can see further, or not.


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    #103
    fillup
    Registered Users Posts: 560 ✭✭✭fillup


    Capt'n Midnight wrote: »
    But they could use a laser rangefinder.
    Not in 1927 unless they'd inadvertently discovered time travel whilst measuring the speed of light but that's a different thread entirely


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    #104
    [Deleted User]
    Posts: 0 ✭ [Deleted User]


    standardg60 wrote: »
    How can it not?
    The universe is an expansion of light, and life is dependent on that very expansion.
    If the universe ceases to expand, then existence ceases.
    It is the difference between the rates of expansion from where we are to the edge which gives rise to time.

    The universe is not an expansion of light. The universe is composed of various fundamental particles and forces, one of which is light.
    https://en.wikipedia.org/wiki/Standard_Model


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    #105
    [Deleted User]
    Posts: 0 ✭ [Deleted User]


    Curious_Case wrote: »
    Simples

    If, for instance, the 2 cars were in a dragster race and both hurtled down the track at C (velocity of light) then they would maintain position relative to each other and neither would be moving relative to the other. Therefore they are approaching/separating at ZERO velocity but nevertheless they are, absolutely, both travelling at C.

    Similarly, if they are approaching each other (both travelling on the same trajectory) then they are, absolutely, closing the distance at a velocity of TWICE C. Nevertheless, neither of them are travelling at anything other than C.

    Velocity is defined as speed in a straight line.
    As the cars velocities are steady @ C, acceleration is zero in both cases.

    https://media.tenor.com/images/f0868be38014452f2dd71559bbecc402/tenor.gif


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    #106
    Curious_Case
    Registered Users Posts: 1,525 ✭✭✭Curious_Case


    standardg60 wrote: »
    It has to be necessary. If we can see that the universe is expanding, then it must be expanding at a different speed to ours. If we were expanding at the same speed then we wouldn't see it.

    I've always assumed that the distances between galaxies is known to be increasing in all directions and the expanding universe theory is a possible explanation.

    As far as I know, it's the amount of red shift that provides the means of determining that galaxies are moving away from each other, nothing to do with varying speeds of light.


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    #107
    Capt'n Midnight
    Moderators, Recreation & Hobbies Moderators, Science, Health & Environment Moderators, Technology & Internet Moderators Posts: 90,700 Mod ✭✭✭✭Capt'n Midnight


    fillup wrote: »
    Not in 1927 unless they'd inadvertently discovered time travel whilst measuring the speed of light but that's a different thread entirely
    When you are messing about with fundamental forces strange things can happen.


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    #108
    [Deleted User]
    Posts: 0 ✭ [Deleted User]


    PMBC wrote: »
    What about tachyons?

    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.


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    #109
    Curious_Case
    Registered Users Posts: 1,525 ✭✭✭Curious_Case


    [Deleted User] wrote: »
    https://media.tenor.com/images/f0868be38014452f2dd71559bbecc402/tenor.gif

    I'm not easily offended, I'd be happy to stand corrected : )

    Was I wrong to sidestep the relativity issue?

    The perspective of a stationary independent observer seems sufficient.


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    #110
    [Deleted User]
    Posts: 0 ✭ [Deleted User]


    Curious_Case wrote: »
    I've always assumed that the distances between galaxies is known to be increasing in all directions and the expanding universe theory is a possible explanation.

    As far as I know, it's the amount of red shift that provides the means of determining that galaxies are moving away from each other, nothing to do with varying speeds of light.

    Yes, you are referring to cosmological redshift.
    https://en.wikipedia.org/wiki/Hubble%27s_law#Combining_redshifts_with_distance_measurements


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    #111
    Gregor Samsa
    Registered Users Posts: 8,908 ✭✭✭Gregor Samsa


    standardg60 wrote: »
    How can it not?
    The universe is an expansion of light, and life is dependent on that very expansion.
    If the universe ceases to expand, then existence ceases.
    It is the difference between the rates of expansion from where we are to the edge which gives rise to time.

    None of these statements are true.

    Space itself is expanding. Light and matter merely moves within it. The expansion is not caused by light.

    The if there was enough matter in the universe, gravity would overcome expansion, and the universe would eventually contract. Existence would not cease because of the contraction, and time would still flow forward - but it would cease when the contraction stops in the form of a “Big Crunch” singularity. As it happens, there does not seem to be enough matter in the universe for this to occur, but this is not 100% verified.

    Time is part of the fabric of the universe (space time), it’s not caused by difference in the rate of expansion. The arrow of time is made evident by the fact that the universe - as an isolated system - must increase in entropy: going from an ordered state to a disordered state. It can’t go the other way, and this give us the past (low entropy) and the future (high entropy).


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    #112
    fillup
    Registered Users Posts: 560 ✭✭✭fillup


    Capt'n Midnight wrote: »
    When you are messing about with fundamental forces strange things can happen.
    When faced with such circumstances one should be guided by the What Would McFly Do principle


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    #113
    [Deleted User]
    Posts: 0 ✭ [Deleted User]


    Curious_Case wrote: »
    I'm not easily offended, I'd be happy to stand corrected : )

    Was I wrong to sidestep the relativity issue?

    The perspective of a stationary independent observer seems sufficient.

    You described what relative motion is according to Newton, not Einstein.


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    #114
    Curious_Case
    Registered Users Posts: 1,525 ✭✭✭Curious_Case


    [Deleted User] wrote: »
    You described what relative motion is according to Newton, not Einstein.

    Yes, but simply addressing the opening posters query.

    The cars are indeed approaching each other @ 2C yet neither is exceeding C


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    #115
    [Deleted User]
    Posts: 0 ✭ [Deleted User]


    Curious_Case wrote: »
    Yes, but simply addressing the opening posters query.

    The cars are indeed approaching each other @ 2C yet neither is exceeding C

    They are not approaching at 2C, not according to each other nor a stationary observer, as my graph earlier showed.


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    #116
    Curious_Case
    Registered Users Posts: 1,525 ✭✭✭Curious_Case


    [Deleted User] wrote: »
    They are not approaching at 2C, not according to each other nor a stationary observer, as my graph earlier showed.

    Ok, but would it be correct to say that the distance between them is reducing @ 2C

    I will take a peek at your graph but I'm not optimistic that I'll understand it : (


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    #117
    Capt'n Midnight
    Moderators, Recreation & Hobbies Moderators, Science, Health & Environment Moderators, Technology & Internet Moderators Posts: 90,700 Mod ✭✭✭✭Capt'n Midnight


    Curious_Case wrote: »
    Ok, but would it be correct to say that the distance between them is reducing @ 2C

    I will take a peek at your graph but I'm not optimistic that I'll understand it : (
    It's nearly but not quite 2C and only from the point of view of a third party standing at ground zero.

    Anything travelling at 3Km a second has the same energy as the same mass of TNT. Ignoring relativity a 1 tonne craft (small car) might as well be a fully weaponised Tsar bomba rather than the semi-inert lead filled (peaked at 1% solar output) one tested. Not ignoring relativity would be orders of magnitude worse.

    Like a fluorine-metal fire it's something best watched from a safe distance.


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    #118
    Mr. CooL ICE
    Registered Users Posts: 17,497 ✭✭✭✭Mr. CooL ICE


    I'm up feeding a newborn and reading this thread has melted my sleep deprived mind.

    Imma put on a Michael Bay film for balance.


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    #119
    [Deleted User]
    Posts: 0 ✭ [Deleted User]


    Capt'n Midnight wrote: »

    Anything travelling at 3Km a second has the same energy as the same mass of TNT. Ignoring relativity a 1 tonne craft (small car) might as well be a fully weaponised Tsar bomba rather than the semi-inert lead filled (peaked at 1% solar output) one tested. Not ignoring relativity would be orders of magnitude worse.

    Like a fluorine-metal fire it's something best watched from a safe distance.


    Thats the famous. E=MC²


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    #120
    skallywag
    Registered Users Posts: 2,987 ✭✭✭skallywag


    Gregor Samsa wrote: »
    Space itself is expanding. Light and matter merely moves within it. The expansion is not caused by light.

    I think getting ones head around this is key to understanding what is happening, i.e. it is the space in between galaxies which is expanding, and not the galaxies themselves.

    I find the balloon analogy very useful ...

    https://www.youtube.com/watch?v=_PVitVku_C0

    https://www.youtube.com/watch?v=hDTPvIKw9z8


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    #121
    [Deleted User]
    Posts: 0 ✭ [Deleted User]


    skallywag wrote: »
    I think getting ones head around this is key to understanding what is happening, i.e. it is the space in between galaxies which is expanding, and not the galaxies themselves.

    I find the balloon analogy very useful ...

    https://www.youtube.com/watch?v=_PVitVku_C0

    https://www.youtube.com/watch?v=hDTPvIKw9z8

    The balloon analogy only allows you to understand why expansion causes objects to get further apart without moving, but besides that it's a pretty bad analogy. The surface of an expanding balloon is two dimensional which is itself enclosing a three dimensional object, but the universe isn't embedded within a higher dimension and it also isn't expanding into anything. Also, the expansion of space has no centre like an expanding balloon does.


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