6 ms·
Yeah, it's weird like the light from some of the stars takes so long to get to us that when it left home, the dinosaurs were still roaming the earth... and then
by balabaster 8y ago
Yeah, it's weird like the light from some of the stars takes so long to get to us that when it left home, the dinosaurs were still roaming the earth... and then after some 65 million years, it hits us allowing us to see that star which was once there in its place in the sky, and one assumes still is, but we can't be sure, and that's that. Done. Over. Gone.
Though, I supposed given that energy can neither be created nor destroyed it somehow changes form and is absorbed in some fashion.
Crazy for something to spend so long travelling in a straight(ish) line and the BAM! Finished.
- quakeguy 8y agoSome light that reaches us was sent out when earth wasn't even formed... And some light will never reach us, the universe is expanding at a higher rate, future astronomers will find the sky empty. That's crazy as well.
- gowld 8y agoLight travels in perfectly straight lines (geodesics in spacetime). The trip takes 0 time and 0 distance for the photon, from emission til absorption.
- balabaster 8y agoLight's path is affected by gravity of the bodies it passes in space, so technically it doesn't travel in perfectly straight lines at all.
- saagarjha 8y agoThe parent commenter mentions this when discussing "geodesics in spacetime".
- peanutz454 8y ago0 time due to time dilation, but 0 distance?
- 12298765 8y agoYeah, due to length contraction
- jstanley 8y agoI think the reason it experiences 0 time is actually because of length contraction. The photon experiences the entire universe contracted to 0 length, so of course it travels along its path in 0 time.
- Retra 8y ago"For the photon" and "the photon's experience" are nonsense concepts. There is no such frame of reference, so it makes no sense to postulate what things would look like from it.
- warent 8y agoUnless you have a better theory of spacetime and gravity than Einstein, it's safe to say frames of reference are a fundamental aspect of the nature of the universe. https://en.m.wikipedia.org/wiki/Observer_(special_relativity) https://en.m.wikipedia.org/wiki/Observer_(special_relativity...
- Retra 8y agoI didn't say frames of reference don't exist, I said frames of reference don't exist for photons. I'm not sure Einstein or his theories indicate any disagreement on that point.
- warent 8y agoYou're right, I misread and jumped the gun. That being said, can you cite photons having no frame of reference? Not denying it to be true, but would like to know more about it.
- 8y ago
- omarchowdhury 8y agoIsn't the emission from a star, and the absorption within an eye or a telescope? There is clearly distance and time between the two here, how are you reducing it to 0?
- sk5t 8y agoTime passes for us, but not for the photon traveling at lightspeed.
- omarchowdhury 8y agoWould you explain why this is so? The speed of light is finite, not infinite.
- zaarn 8y agoA photon is moving at the speed of light. Things moving at the speed of light do not experience distance or time (and have no mass), for them their creation and destruction are the same event. This effect is also valid for objects with actual mass, the faster you go the slower your time moves relative to everyone else and the shorter distances become. You can't hit the speed of light but you can get fairly close.
- omarchowdhury 8y ago> A photon is moving at the speed of light. Things moving at the speed of light do not experience distance or time (and have no mass), for them their creation and destruction are the same event. How does this follow? There is still a traversal of spacetime at a limited speed between the creation and destruction. If the speed of light was infinite then yes I would agree with the proposition that no time or space experienced. You are offering a description without the explanation.
- zaarn 8y ago>There is still a traversal of spacetime at a limited speed between the creation and destruction. From your point of view, that is correct. From the hypothetical point of view of a photon, an object moving at the speed of light, time does not pass and the distance gets squished into zero. You can observe a partial effect by looking at cosmic rays. We can detect several decay products of cosmic rays on the ground despite these decay products being far too short lived and too slow to have actually reached the ground. However, due to their high speed, their internal clock runs "slower" compared to ours and the distance between the top of the atmosphere where they are created in a collision or decay and the ground is much shorter than they can travel at their speed. A photon experiences the same effect times infinity; distance and time no longer have a reasonable meaning other than being 0.
- warent 8y agoLight that traveled across trillions of trillions of kilometers, passing endless galaxies, nebulae, planets, (possibly extraterrestrial lifeforms) and other breathtaking interstellar objects, all so that it can end its journey on the bum of a random tourist at on a beach. What a world!
- JCharante 8y agoFortunately for the light, its trip was pretty instantaneous.
- mark-r 8y agoRelatively speaking.
- balabaster 8y agoIt's a hard concept to wrap your head around. Eons of time have passed for us, planets have formed, entire species have evolved, flourished and become extinct, ice ages have happened, wars, humanity has grown up and has reached a point where we're on the cusp of escaping the boundaries of this rock we call home... but for the light, it blinked into existence and out again, in a moment, time and distance completely irrelevant to its existence... it's as if instead of traveling across our space and time, it is merely passing through from some other dimension.
- sethammons 8y agoThe one that gets me: in the future, the expanded universe will be so spread out that there will be no detectable anything outside of your immediate solar neighborhood. No stars. No nothing. There will be no reason to assume the rest of the universe even exists. We live at an amazing time in our universe's history where we can see stars and learn from them.
- dredmorbius 8y agoThe expansion constant is weaker than gravity, such that gravitationally-bound structures, including everything from asteroids up through galactic clusters, will survive. Beyond the local galactic cluster though -- quite possibly nothing.
- ValleyOfTheMtns 8y ago> Beyond the local galactic cluster though -- quite possibly nothing. Do you mean the Local Group? https://en.wikipedia.org/wiki/Local_Group https://en.wikipedia.org/wiki/Local_Group Or the Local Supercluster? https://en.wikipedia.org/wiki/Virgo_Supercluster https://en.wikipedia.org/wiki/Virgo_Supercluster
- dwaltrip 8y agoThe Local Group is gravitationally bound, but that isn't the case with the local supercluster. I believe that most (all?) superclusters are not gravitationally bound. In fact, the entire local group will eventually be a single galaxy I believe, mostly composed of the contents of the Milky Way and Andromeda galaxies.
- harshulpandav 8y agoSeeing dinosaurs could be possible if a 4 light year wide telescope is sent via a worm hole to one of the galaxies in the Virgo cluster (65m light years away) and live imagery of Earth (not via worm hole) is sent back via the worm hole to Earth.
- balabaster 8y agoI think this would give us all kinds of insight we're totally wrong about at the moment.
- swebs 8y agoEnergy is created all the time in the form of Dark Energy.