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help I dont understand relativity

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    Quantum TigerQuantum Tiger Registered User regular
    edited July 2021
    Knob wrote: »
    Pinfeldorf wrote: »
    Okay since it's been brought up I'd like to ask a question.

    If E=MC², how can photons have energy if they do not have mass? Anything times 0 should remain 0, right? Also, if photons are massless, how does light have mass? Or maybe what I should be asking is, what is the difference between a photon and light?

    a photon has a rest mass of zero but is also has a rest mass of not zero and we kind of have to accept both of these as true because of they weren't it'd break a lot of other things we've measured

    To add to this the full equation is

    E² = m²c⁴ + p²c²

    Where p is momentum

    When there is no momentum the equation collapses to the familiar one, but when mass is zero it collapses to E = pc

    So because photons have momentum it still works (and they do otherwise things like solar sails wouldn't work)

    Another neat thing about the full equation is that it allows for negative energy which has interesting implications

    Quantum Tiger on
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    MadicanMadican No face Registered User regular
    Maybe if you crossed a black hole event horizon, which you would experience in real time while everyone outside it sees you frozen in position, but then the tricky part is leaving the event horizon.

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    PiptheFairPiptheFair Frequently not in boats. Registered User regular
    how fast do you have to be traveling for time dilation to be appreciable?

    like, I don't want to live through it, but I'm interested to see how the world ends up in a couple decades.

    could I conceivably get into some manner of satellite and orbit Earth fast enough that I can take a day long Klonopin nap and wake up 20 years later?

    that in fact happens to satellites, albeit in a very small way

    internal clocks are calibrated to adjust

    'appreciable' is very ambiguous, but like you are in fact experiencing time dilation and have for your entire life

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    Andy JoeAndy Joe We claim the land for the highlord! The AdirondacksRegistered User regular
    edited July 2021
    Another neat thing about the full equation is that it allows for negative mass which has interesting implications

    Like antigravity?

    Andy Joe on
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    3cl1ps33cl1ps3 I will build a labyrinth to house the cheese Registered User regular
    how fast do you have to be traveling for time dilation to be appreciable?

    like, I don't want to live through it, but I'm interested to see how the world ends up in a couple decades.

    could I conceivably get into some manner of satellite and orbit Earth fast enough that I can take a day long Klonopin nap and wake up 20 years later?

    You are technically always experiencing time dilation to some degree, it's just quite small and negligible for every day life. It is there, though. For instance, GPS satellites need to account for time dilation from both general relativity and special relativity in order to remain accurate.

    As for orbiting so quickly you experience that level of time dilation, in a thought experiment where earth has infinite mass, yes, in practice, no. The only objects massive enough and also small enough to keep objects moving a measurable percentage of c in orbit are black holes.

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    KetBraKetBra Dressed Ridiculously Registered User regular
    To peel this out of the tabletop thread: The speed of light is constant relative to reference points right? But what if a different reference point perceives the same object traveling at the speed of light, and that reference point is moving relative to the first one? My head hurts

    Your reference frame can't be exactly at the speed of light because you end up with your length scale contracting to zero, but if it's close, the light (which is the only thing that will be travelling at the speed of light) will be travelling at the speed of light

    KGMvDLc.jpg?1
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    BahamutZEROBahamutZERO Registered User, Moderator mod
    Pinfeldorf wrote: »
    PiptheFair wrote: »
    Duke 2.0 wrote: »
    Know that despite their best efforts, people who know the math cannot dumb it down enough. They will start using terms that mean specific things to those in the know like Reference Frames that you might have a sorta idea about until you ask a question and the person in the know gets irate because you just asked something stupid like what if red was green.

    https://www.youtube.com/watch?v=Q1lL-hXO27Q

    This video rules.

    get his ass feynman
    Pinfeldorf wrote: »
    Knob wrote: »
    Pinfeldorf wrote: »
    Okay since it's been brought up I'd like to ask a question.

    If E=MC², how can photons have energy if they do not have mass? Anything times 0 should remain 0, right? Also, if photons are massless, how does light have mass? Or maybe what I should be asking is, what is the difference between a photon and light?

    a photon has a rest mass of zero but is also has a rest mass of not zero and we kind of have to accept both of these as true because of they weren't it'd break a lot of other things we've measured

    Thanks. This doesn't really help me understand anything but I guess it's as as close to an answer I can understand as exists.

    As I understand it, energy and mass are different forms of the same stuff, and can convert between the forms under the right circumstances.

    BahamutZERO.gif
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    BaidolBaidol I will hold him off Escape while you canRegistered User regular
    PiptheFair wrote: »
    Pinfeldorf wrote: »
    Okay since it's been brought up I'd like to ask a question.

    If E=MC², how can photons have energy if they do not have mass? Anything times 0 should remain 0, right? Also, if photons are massless, how does light have mass? Or maybe what I should be asking is, what is the difference between a photon and light?

    a photon carries a charge though

    Point of order: photons are chargeless.

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    KnobKnob TURN THE BEAT BACK InternetModerator Mod Emeritus
    Pinfeldorf wrote: »
    Knob wrote: »
    Pinfeldorf wrote: »
    Okay since it's been brought up I'd like to ask a question.

    If E=MC², how can photons have energy if they do not have mass? Anything times 0 should remain 0, right? Also, if photons are massless, how does light have mass? Or maybe what I should be asking is, what is the difference between a photon and light?

    a photon has a rest mass of zero but is also has a rest mass of not zero and we kind of have to accept both of these as true because of they weren't it'd break a lot of other things we've measured

    Thanks. This doesn't really help me understand anything but I guess it's as as close to an answer I can understand as exists.

    If it makes you feel better, it also doesn't help scientists understand anything. We don't actually have the ability to measure very much about photons at all, we have to extrapolate their qualities and behaviors from other measurable phenomena. And some things we can measure tell us one thing and some things tell us the opposite.

    When things go very fast, math gets weird. When things get very small, math gets weird. Photons are both the fastest and smallest things in the known universe, so there's a lot of weirdness.

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    GreenGreen Stick around. I'm full of bad ideas.Registered User regular
    Duke 2.0 wrote: »
    Know that despite their best efforts, people who know the math cannot dumb it down enough. They will start using terms that mean specific things to those in the know like Reference Frames that you might have a sorta idea about until you ask a question and the person in the know gets irate because you just asked something stupid like what if red was green.

    Okay but what if it was green though

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    Quantum TigerQuantum Tiger Registered User regular
    Andy Joe wrote: »
    Another neat thing about the full equation is that it allows for negative mass which has interesting implications

    Like antigravity?

    Oh yeah, it's been mentioned in theories of time travel, wormholes etc. Really out there stuff that I don't subscribe to but is neat to think about

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    BahamutZEROBahamutZERO Registered User, Moderator mod
    KetBra wrote: »
    To peel this out of the tabletop thread: The speed of light is constant relative to reference points right? But what if a different reference point perceives the same object traveling at the speed of light, and that reference point is moving relative to the first one? My head hurts

    Your reference frame can't be exactly at the speed of light because you end up with your length scale contracting to zero, but if it's close, the light (which is the only thing that will be travelling at the speed of light) will be travelling at the speed of light

    Imagine you accelerate to near the speed of light, and then the rest of the universe is deleted somehow. Are you still moving without any other reference points? if you add a reference point back in but it's stationary relative to you, without having changed your momentum from before the universe was deleted, can you now accelerate up to near the speed of light again as if you were at rest?

    BahamutZERO.gif
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    KetBraKetBra Dressed Ridiculously Registered User regular
    The whole E=mc^2 thing is just the rest mass energy, it's just one type of energy

    Things like electric and magnetic fields can also hold energy, but have no mass. Also, photons happen to be made of them.

    KGMvDLc.jpg?1
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    MadicanMadican No face Registered User regular
    Green wrote: »
    Duke 2.0 wrote: »
    Know that despite their best efforts, people who know the math cannot dumb it down enough. They will start using terms that mean specific things to those in the know like Reference Frames that you might have a sorta idea about until you ask a question and the person in the know gets irate because you just asked something stupid like what if red was green.

    Okay but what if it was green though

    Then it would be slower

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    3cl1ps33cl1ps3 I will build a labyrinth to house the cheese Registered User regular
    We're probably all just local disturbances in the quantum field of the universal wave function, anyway.

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    GarthorGarthor Registered User regular
    edited July 2021
    Pinfeldorf wrote: »
    Knob wrote: »
    Pinfeldorf wrote: »
    Okay since it's been brought up I'd like to ask a question.

    If E=MC², how can photons have energy if they do not have mass? Anything times 0 should remain 0, right? Also, if photons are massless, how does light have mass? Or maybe what I should be asking is, what is the difference between a photon and light?

    a photon has a rest mass of zero but is also has a rest mass of not zero and we kind of have to accept both of these as true because of they weren't it'd break a lot of other things we've measured

    Thanks. This doesn't really help me understand anything but I guess it's as as close to an answer I can understand as exists.

    E=mc² excludes momentum. The more complete equation is E² = (pc)² + (m₀c²)² where p is momentum. So in the case of photons, E = pc, which is nonzero.

    [edit]Oh there was another page.

    Garthor on
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    BahamutZEROBahamutZERO Registered User, Moderator mod
    3cl1ps3 wrote: »
    We're probably all just local disturbances in the quantum field of the universal wave function, anyway.

    as opposed to what

    BahamutZERO.gif
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    Munkus BeaverMunkus Beaver You don't have to attend every argument you are invited to. Philosophy: Stoicism. Politics: Democratic SocialistRegistered User, ClubPA regular
    KetBra wrote: »
    The whole E=mc^2 thing is just the rest mass energy, it's just one type of energy

    Things like electric and magnetic fields can also hold energy, but have no mass. Also, photons happen to be made of them.

    675yrw6zbf56.png

    Humor can be dissected as a frog can, but dies in the process.
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    3cl1ps33cl1ps3 I will build a labyrinth to house the cheese Registered User regular
    3cl1ps3 wrote: »
    We're probably all just local disturbances in the quantum field of the universal wave function, anyway.

    as opposed to what

    There are still people who think quantum field theory is bullshit!

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    BahamutZEROBahamutZERO Registered User, Moderator mod
    3cl1ps3 wrote: »
    3cl1ps3 wrote: »
    We're probably all just local disturbances in the quantum field of the universal wave function, anyway.

    as opposed to what

    There are still people who think quantum field theory is bullshit!

    that was a serious question, what alternative ideas are there for what "things existing" means

    BahamutZERO.gif
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    KetBraKetBra Dressed Ridiculously Registered User regular
    KetBra wrote: »
    To peel this out of the tabletop thread: The speed of light is constant relative to reference points right? But what if a different reference point perceives the same object traveling at the speed of light, and that reference point is moving relative to the first one? My head hurts

    Your reference frame can't be exactly at the speed of light because you end up with your length scale contracting to zero, but if it's close, the light (which is the only thing that will be travelling at the speed of light) will be travelling at the speed of light

    Imagine you accelerate to near the speed of light, and then the rest of the universe is deleted somehow. Are you still moving without any other reference points? if you add a reference point back in but it's stationary relative to you, without having changed your momentum from before the universe was deleted, can you now accelerate up to near the speed of light again as if you were at rest?

    The physics (ie. energy required to have the same relative speed from two hypothetical reference frames at different speeds) should be the same, since in both cases the reference frames are not accelerating

    KGMvDLc.jpg?1
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    3cl1ps33cl1ps3 I will build a labyrinth to house the cheese Registered User regular
    3cl1ps3 wrote: »
    3cl1ps3 wrote: »
    We're probably all just local disturbances in the quantum field of the universal wave function, anyway.

    as opposed to what

    There are still people who think quantum field theory is bullshit!

    that was a serious question, what alternative ideas are there for what "things existing" means

    Oh, that classical physics is still correct and we're all discrete masses and photons are just Weird Quantum Shit and observing a system really has an effect on it (instead of just snapshotting a localized amplitude in our worldline) that one day we'll figure out how to marry with Newtonian physics.

    I'm not saying it's rigorous :rotate:

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    BahamutZEROBahamutZERO Registered User, Moderator mod
    KetBra wrote: »
    KetBra wrote: »
    To peel this out of the tabletop thread: The speed of light is constant relative to reference points right? But what if a different reference point perceives the same object traveling at the speed of light, and that reference point is moving relative to the first one? My head hurts

    Your reference frame can't be exactly at the speed of light because you end up with your length scale contracting to zero, but if it's close, the light (which is the only thing that will be travelling at the speed of light) will be travelling at the speed of light

    Imagine you accelerate to near the speed of light, and then the rest of the universe is deleted somehow. Are you still moving without any other reference points? if you add a reference point back in but it's stationary relative to you, without having changed your momentum from before the universe was deleted, can you now accelerate up to near the speed of light again as if you were at rest?

    The physics (ie. energy required to have the same relative speed from two hypothetical reference frames at different speeds) should be the same, since in both cases the reference frames are not accelerating

    2t67wm1lojs6.gif

    BahamutZERO.gif
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    PlatyPlaty Registered User regular
    edited July 2021
    KetBra wrote: »
    To peel this out of the tabletop thread: The speed of light is constant relative to reference points right? But what if a different reference point perceives the same object traveling at the speed of light, and that reference point is moving relative to the first one? My head hurts

    Your reference frame can't be exactly at the speed of light because you end up with your length scale contracting to zero, but if it's close, the light (which is the only thing that will be travelling at the speed of light) will be travelling at the speed of light

    Imagine you accelerate to near the speed of light, and then the rest of the universe is deleted somehow. Are you still moving without any other reference points? if you add a reference point back in but it's stationary relative to you, without having changed your momentum from before the universe was deleted, can you now accelerate up to near the speed of light again as if you were at rest?

    You can arbitrarily consider yourself at rest anytime you're not accelerating (like a person on the surface of the earth)

    Your own accelerating path through spacetime is going to look very different to you and an outside observer due to time dilation and length contraction

    Platy on
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    Librarian's ghostLibrarian's ghost Librarian, Ghostbuster, and TimSpork Registered User regular
    I read Hawking’s book several years ago so I’m glad I actually understand the technical posts.

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    KetBraKetBra Dressed Ridiculously Registered User regular
    KetBra wrote: »
    The whole E=mc^2 thing is just the rest mass energy, it's just one type of energy

    Things like electric and magnetic fields can also hold energy, but have no mass. Also, photons happen to be made of them.

    675yrw6zbf56.png

    Electric and magnetic fields, such as produced by charges or currents, can store energy. We use this in things like capacitors or inductors. You can think of it somewhat equivalently to the classical view of gravity, where something on Earth which is higher has more gravitational potential energy than something that is lower. Light is electromagnetic radiation, and so consists of oscillating electric and magnetic fields. The smallest amount of this oscillating (wiggling wave-like) field possible is a photon, which still is an oscillating electromagnetic field

    KGMvDLc.jpg?1
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    GundiGundi Serious Bismuth Registered User regular
    edited July 2021
    how fast do you have to be traveling for time dilation to be appreciable?

    like, I don't want to live through it, but I'm interested to see how the world ends up in a couple decades.

    could I conceivably get into some manner of satellite and orbit Earth fast enough that I can take a day long Klonopin nap and wake up 20 years later?


    Not unless you know a way to accelerate something to like very, very close to the speed of light. Like. for your particular example I think, 99.986% the speed of light. I'm not gonna calculate the amount of energy that would require because it'd be such a high amount of energy that it'd be meaningless. We kinda don't reference points.

    Gundi on
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    Duke 2.0Duke 2.0 Time Trash Cat Registered User regular
    Quantum field theory could very well be correct, while also being bullshit

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    ElvenshaeElvenshae Registered User regular
    PiptheFair wrote: »
    Duke 2.0 wrote: »
    Know that despite their best efforts, people who know the math cannot dumb it down enough. They will start using terms that mean specific things to those in the know like Reference Frames that you might have a sorta idea about until you ask a question and the person in the know gets irate because you just asked something stupid like what if red was green.

    https://www.youtube.com/watch?v=Q1lL-hXO27Q

    I love Feynman so much.

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    GundiGundi Serious Bismuth Registered User regular
    PiptheFair wrote: »
    Pinfeldorf wrote: »
    Knob wrote: »
    Pinfeldorf wrote: »
    Okay since it's been brought up I'd like to ask a question.

    If E=MC², how can photons have energy if they do not have mass? Anything times 0 should remain 0, right? Also, if photons are massless, how does light have mass? Or maybe what I should be asking is, what is the difference between a photon and light?

    a photon has a rest mass of zero but is also has a rest mass of not zero and we kind of have to accept both of these as true because of they weren't it'd break a lot of other things we've measured

    Thanks. This doesn't really help me understand anything but I guess it's as as close to an answer I can understand as exists.

    yeah, it's like the feynman video

    basically, because theoretical physics is completely fucking insane and alien to anybody who does not study it, theres just some shit you kinda have to accept even if it sounds dumb as hell because there is absolutely no reference point
    B: "That's crazy. That's bullshit!"
    A: "The crazy bullshit works based off all our previous observations and experiments".
    B: "Okay but how does it work?"
    A: "Um, okay look at this enourmous mathematical equation-" *Clubs B over the head*

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    KetBraKetBra Dressed Ridiculously Registered User regular
    Just like fyi Feynman was a sexist asshole

    KGMvDLc.jpg?1
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    PolaritiePolaritie Sleepy Registered User regular
    Gundi wrote: »
    PiptheFair wrote: »
    Pinfeldorf wrote: »
    Knob wrote: »
    Pinfeldorf wrote: »
    Okay since it's been brought up I'd like to ask a question.

    If E=MC², how can photons have energy if they do not have mass? Anything times 0 should remain 0, right? Also, if photons are massless, how does light have mass? Or maybe what I should be asking is, what is the difference between a photon and light?

    a photon has a rest mass of zero but is also has a rest mass of not zero and we kind of have to accept both of these as true because of they weren't it'd break a lot of other things we've measured

    Thanks. This doesn't really help me understand anything but I guess it's as as close to an answer I can understand as exists.

    yeah, it's like the feynman video

    basically, because theoretical physics is completely fucking insane and alien to anybody who does not study it, theres just some shit you kinda have to accept even if it sounds dumb as hell because there is absolutely no reference point
    B: "That's crazy. That's bullshit!"
    A: "The crazy bullshit works based off all our previous observations and experiments".
    B: "Okay but how does it work?"
    A: "Um, okay look at this enourmous mathematical equation-" *Clubs B over the head*

    The worst part is relativity is actually the shallow end of the pool there with how easy it is to demonstrate experimentally and such.

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    KetBraKetBra Dressed Ridiculously Registered User regular
    KetBra wrote: »
    Just like fyi Feynman was a sexist asshole

    Joan Feynman was cool though I read a chapter of an air force manual by her it was pretty good

    KGMvDLc.jpg?1
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    milskimilski Poyo! Registered User regular
    how fast do you have to be traveling for time dilation to be appreciable?

    like, I don't want to live through it, but I'm interested to see how the world ends up in a couple decades.

    could I conceivably get into some manner of satellite and orbit Earth fast enough that I can take a day long Klonopin nap and wake up 20 years later?

    Depends on what you mean by appreciable. Time dilation already factors in to GPS calculations to make sure you have accuracy better than "within this football field sized area", but you'd need a ship faster than anything we've ever built by orders of magnitude to realistically dilate your personal time in a way that's noticable.

    I ate an engineer
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    ElvenshaeElvenshae Registered User regular
    KetBra wrote: »
    KetBra wrote: »
    Just like fyi Feynman was a sexist asshole

    Joan Feynman was cool though I read a chapter of an air force manual by her it was pretty good

    Shit, she died last year. I didn't realize that.

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    milskimilski Poyo! Registered User regular
    I experienced appreciable time dilation with my posting, that's why I was so late.

    I ate an engineer
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    ChallChall Registered User regular
    edited July 2021
    Hey relativity thread, good timing. I just saw a thing about how we photographed the "emissions" from a Black Hole's ass for the first time

    Chall on
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    KnobKnob TURN THE BEAT BACK InternetModerator Mod Emeritus
    how far does science have to go before we can pay a black hole to sit down on a birthday cake and fart

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    MadicanMadican No face Registered User regular
    [shower thought]
    Is time dilation an actual thing or an alteration of perception that we consider to be time dilation. And is there a functional difference between the two.
    [/shower thought]

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    KetBraKetBra Dressed Ridiculously Registered User regular
    Madican wrote: »
    [shower thought]
    Is time dilation an actual thing or an alteration of perception that we consider to be time dilation. And is there a functional difference between the two.
    [/shower thought]

    Relativity is fundamentally a matter of perception, it's our understanding of how physics work given different frames of reference

    KGMvDLc.jpg?1
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