[ron123456 (OP)]

I heard that one twin returned to earth from the moon younger than the one remaining on earth.....His birthday moved into the future.....To me, who remained on earth, his time dilation increased due to his velocity, with his change in time decreasing leaving him younger.....
When a light photon travels from a galaxy 10B light years away from earth to another galaxy 9B light years away from earth, would the same not happen as above to anybody observing on the galaxy 9B light years away from us? That is, would a change in time for the photon not decrease upon reaching the '9B light years away from us' galaxy'?.....
So to an observer on the '9B galaxy' there exists a discrepancy in change of time wrt the arriving photon? Change in time for the photon is smaller?...The photon would thus see a larger expansion of space at the '9B galaxy' leaving it perhaps with the same expansion rate of space that we observe here on earth for the '10B galaxy'? Thus is dark energy acceleration related to a relativistic time dilation parameter? Confusing?



 

[Bored chemist]

"Is Time Dilation related to Dark Energy?"
Yes; one relationship seems to be that you understand neither.

[ron123456 (OP)]

Yes, I'm a layperson just with an interest...Could u please elaborate simply with some educating...Thx

[Halc]

I heard that one twin returned to earth from the moon younger than the one remaining on earth

Not by anywhere near enough to make up the difference between their birth times. The one that was born first is still older even if he's the one that went to the moon. The dilation is measured in microseconds.

When a light photon travels from a galaxy 10B light years away from earth to another galaxy 9B light years away from earth

If it's moving to a galaxy closer to us, then it's not moving away from Earth, but towards us.

would the same not happen as above to anybody observing on the galaxy 9B light years away from us?

The guy isn't travelling from here and back. Yes, if he did, he'd be younger than his twin left behind.

That is, would a change in time for the photon not decrease upon reaching the '9B light years away from us' galaxy'?.....

Light doesn't have a proper age, so you can't talk about it being younger or older. There is no meaningful 'time for a photon'.

So to an observer on the '9B galaxy' there exists a discrepancy in change of time wrt the arriving photon?

We're receding from each other, so the distance between us isn't going to remain 9B LY.  You can leave now and get there, but if you immediately turn around, you'll never get back since, due to acceleration of expansion of space, the distance between us at time of arrival will exceed the distance to the event horizon. So your 9B galaxy is too far away to do a comparison of ages with somebody left behind.

Thus is dark energy acceleration related to a relativistic time dilation parameter? Confusing?

With the exception of the acceleration of expansion, dark energy is totally unrelated to the above discussion.

[ron123456 (OP)]

Thx.....I was just talking about acceleration of expansion due to dark energy...I apologize and will be a bit more cautious on my input to Just Chat ..

[Zer0]

Another Layperson tip toes in...
😁
Oink oink!

Isn't it Incredible that Photons are Massless.
😇
Any massless particle shall propogate at the speed of light.

But Why are Photons widely theorised or said to experience No Time?
🤔
Travelling from the surface of the Sun to Earth takes 8 minutes, Right!

P.S. - i found a few videos on the Phenomenon by bald men & curly haired women, but None were Helpful.
☹️
(Why don't MODS here make Utube videos?)
😑



Edit - I figured a bit of it out for myself.

It has to do with SR.
Which states that as something goes faster & faster, it shortens in the motion of direction, relative to stationary observer.
Reaching ' c ' it contracts down to 0 length.
Hence No valid reference frame at speed ' c '.

Now what is that Something that's Contracting?
Can i imagine a Spaceship plz?
I also Understand there has to be a Stationary Observer...orelse how the heck can one know...like i don't know how to say this.

Anyways, if S.O. is seeing a Ship travel at 0c then Ship ain't travelling... it's stationary.

Once Ship begins to move & reach 0.5c, then S.O. would see Ship length contracted by Half, is it?

& If Ship reaches 1c, then Ship length in motion of direction would become 0...is that what the S.O. would see?

That means that Ship would have Disappeared!?!
😲

P.P.S. - Strangely today i was wishing someone would answer this in short & brief...& Then later on a One Line Explanation popped into my head.

" But Why are Photons widely theorised or said to experience No Time? "

Ans - As an object speeds up, time dilates...faster the object moves, slower the time ticks...once speed limit of universe ' c ' is reached, Time Halts.
😇
(cool right)
Wish there was an x & y axis chart to showcase such a phenomenon.
😑
I could Not find anything online.


(ReEdit) -

I'm Learning Physics 001.
😇
(Utube...shush!)
🤫

I got something, rather Understood it.
Velocity = dist/time.
(If dist is 300mi & time is 5hrs)
Then d / t = v.
300mi/5hrs = 60mph.(v)

Now i can shuffle around...
v × t = d.   
60mph × 5hrs = 300mi.(dist)

t = d/v. 300mi / 60mph = 5hrs.(t)

Hence i Applied the same equation to Light.
t = d/v.
670,616,629mi / 670,616,629mph
= 1hr.(t)
(It Obviously fits in Perfectly)

But now if i Imagine v of Light higher than the d Light covers then...
670,616,629mi(dist)
/
700,616,629mph(unrealistic vel)
= 0.957180577hrs.(t)
🥴

Soo...Maths broke down?
☹️

Wat da heck is dis...?
" 0.957180577hrs.(t) "
(Unrealistic Gibberish)
😵




Speed is a Scalar, & Velocity is a Vector quantity.
☹️
v = s/t
😑
I ain't doin this Nomore!
😔

[ron123456 (OP)]

Yes , please move this to the cosmology section...I still feel that a photon from an ancient galaxy has more time dilation than one from a more recent galaxy closer to us explaining the acceleration of the expansion of space the further away from us.....man.....gone for camping...
.

[Eternal Student]

Hi.

   I think several of us are struggling to understand what you (Ron) have written in the original post.
   Halc has raised some points and issues, which seem sensible but It's mainly talking around the issue.

   Is Time Dilation related to Dark Energy?   That's a question we can understand.   I'll offer a short, medium and boring but sensible answer:

(Short)   No.  They are separate topics.

(Medium)   Dark energy is not well understood.  Rather than being a thing or a substance, it can be thought of as an indication that our current best theory of gravity (General Relativity) is incorrect or needs adjustment.   So anything is possible.

(Boring but sensible)   We can observe time dilation in reality.  This can be done over distances where we are reasonably confident that dark energy and the expansion of the space are not important.
     Examples:   Atomic clocks kept in motion in aircraft   vs.  atomic clocks kept on the ground;
            Time dilation effects that would influence the GPS used on your mobile phone or car SatNav.

    Could I try to clarify some of what you have written in your (@ron123456) original post?  Do you think a photon experiences time, as Halc and Zer0 have implied?  That's a topic that could be discussed more fully.

But Why are Photons widely theorised or said to experience No Time?

   If you're interested,  Zer0 and/or Ron then it would seem reasonable to start a new thread on that topic.  Ron asked if the existing thread could be moved to another section but you could just start off the new thread in that section.

NOTE:  I am not a moderator, my opinion counts for little.  For whatever it is worth, I think such a question would seem appropriate for the Physics, Astro. and Cosmo. section.

[Colin2B]

I still feel that a photon from an ancient galaxy has more time dilation than one from a more recent galaxy closer to us

That idea would put this topic into New Theories rather than cosmology. As @Halc says, there is no meaningful ‘time for a photon’, so to speak of 2 photons having different time dilations is meaningless.

Just chat is not a good place to put questions like this one.
If you have a new idea or variation on an established theory then New Theories is the place.
If you have questions of clarification about the current understanding of dark matter or expansion of space then best to put them in the physics, astronomy, cosmology section.

@Zer0 you are on the right track. If you look at the SR equations you will see that as an object’s speed gets closer to the speed of light (relative to us) the time it experiences and distance  travelled tend towards zero (important word that  ). So to talk of any object travelling at the speed of light, relative to us, experiencing time is meaningless, such a traveller would arrive instantaneously, so again differences in time dilation are only possible for sub-light objects. Best not go there - there lies philosophy 

[yor_on]

I agree, photons 'intrinsic clock' seems a fun subject :)  ES. Especially if one think as me that it is reasonable to use it ('c') already, as a equivalence to a clock,. That would mean I now would need to define 'c'  as a 'external equivalence' to ones local clock, as well as presuming it to harbor a intrinsic clock That is if I'm thinking right there? It would certainly make my universe more interesting.

Ps: Hope all went well with the laundry and all. Usually socks disappear for me, but I buy them in the same color, so I consider it a well kept secret. Never let chaos win, or maybe the opposite?


syntax
and some more syntax
It never ends.
=

Better add that the equivalence I mentioned is purely local, 'observer dependent' from a global definition, a 'constant' from a local definition. And nothing to be discussed here I think. It belongs to 'New Theories'

[Zer0]

Yes , please move this to the cosmology section...I still feel that a photon from an ancient galaxy has more time dilation than one from a more recent galaxy closer to us explaining the acceleration of the expansion of space the further away from us.....man.....gone for camping...
.

Suppose, The Maximum Speed Limit of the Universe is ...
186,000 miles/sec.

If i somehow imagine trying to reach the M.S.L....
" c " constant.

I begin at v = 0.
Stationary.
Time - 1 sec.

At v = 87% ' c '
Time slows down by Half.
Time - 0.5 sec

At v = 99.5% ' c '
Time slows down to 0.1 sec
Time - 0.1 sec

At v = 100% ' c '
Time Stops.
Time - 0 sec

Taking a Photon as an example...
It Begins & Ends at the Maximum Speed Limit of the Universe..
Hence it's default v = 100% ' c '
So Time = 0 sec.
If no time is passing, time might not dilate.

Time Dilation is effects of...
Energy, Momentum & Mass.

Dark Energy is Expansion of Space faster than ' c '.

Perhaps Dark Energy does not add to the far separating galaxies...
Energy, Momentum & Mass.
Hence Expansion of Space might not add to any time dilation.
It's just Space Adding, without affecting Time.

If i would have somehow gradually gone from
v = 0 to v = 100% ' c '...
M.U.S.L.
Maximum Universal Speed Limit.
I would have perhaps shrunk in length.
Maybe length would be 0.

But the Photon begins at v = 100%
Hence no time to contract or shrink
As Time is 0 sec.


P.S. - Happy Camping Ron!
✌️
(Sciences have stemmed & branched out quite incredibly & prosperously.
But whatever little that lies on the other side might be equally important.
Philosophy shall always remain at the Roots)
✌️😇