Neutrino is faster then photon (light) so how can be this possible?

  • #26
phinds
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OK, nothing is being moved or pushed, but the distance between objects does change, so, relatively speaking, the effect to the observer on the one side is same as if the other object moved, right?

Only if the observer is ignorant of physics. Objects at the farthest reaches of the observable universe are receding from us at about 3c. It would take a pretty total ignorance of physics for someone to conclude from this that they are moving rather than receding.
 
  • #27
Only if the observer is ignorant of physics. Objects at the farthest reaches of the observable universe are receding from us at about 3c. It would take a pretty total ignorance of physics for someone to conclude from this that they are moving rather than receding.
Of course... Though, I was speaking generally.
 
  • #28
phinds
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Of course... Though, I was speaking generally.

So for you "speaking generally" means speaking in very imprecise language in a way that doesn't have any meaning in physics.
 
  • #29
So for you "speaking generally" means speaking in very imprecise language in a way that doesn't have any meaning in physics.
If we didn't have all the data as we (luckily) have today (as Krauss says, in distant future spacetime will expand to the point when humans on Earth will be able to observe just our own galaxy and none other, thus thinking that our Milky Way is our whole observable Universe) then (I go on with my thinking) if it would happen that a star from edge of our galaxy (in appearance) starts to going away from us at faster than light speed, will people of future be able to know what is it happening? That the star is actually not moving at all, but just receding away at FTL due to spacetime expanding or will they be just puzzled and will think it moves FTL?

So, I was generally speaking because I want to have a broader picture on this phenomenon and how humans understand it.

I will stop posting questions and thoughts if what I write is perceived as meaningless.

And thanks to all who can be so patient with me :-)
 
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  • #30
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Our local group will stay together - the milky way together with Andromeda and some smaller galaxies. Stars at the edge of our galaxy will always stay there, unless they are ejected for reasons not connected to expansion (orbital mechanics, collision with Andromeda, supernovae, ...).

They might be able to observe expansion based on a few stars that were ejected from the local group.
 
  • #31
Our local group will stay together - the milky way together with Andromeda and some smaller galaxies. Stars at the edge of our galaxy will always stay there, unless they are ejected for reasons not connected to expansion (orbital mechanics, collision with Andromeda, supernovae, ...).

They might be able to observe expansion based on a few stars that were ejected from the local group.
Seems sensible, thanks.
 
  • #32
phinds
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If we didn't have all the data as we (luckily) have today (as Krauss says, in distant future spacetime will expand to the point when humans on Earth will be able to observe just our own galaxy and none other, thus thinking that our Milky Way is our whole observable Universe) then (I go on with my thinking) if it would happen that a star from edge of our galaxy (in appearance) starts to going away from us at faster than light speed, will people of future be able to know what is it happening? That the star is actually not moving at all, but just receding away at FTL due to spacetime expanding or will they be just puzzled and will think it moves FTL?

So, I was generally speaking because I want to have a broader picture on this phenomenon and how humans understand it.

I will stop posting questions and thoughts if what I write is perceived as meaningless.

And thanks to all who can be so patient with me :-)

That's a very interesting thought that you have had, and is one that has been discussed before by other physicists. The main thought that I remember from the other discussions is this: In the past, people thought that we were at the center of the universe and that our solar system (later our galaxy) was the entirety of the universe. They were far more wrong than they could imagine, but they DID to some extent base their thought on what observations they could make. In the far future, people will believe that our galaxy is the entirety of the universe and they will be more wrong than they could imagine, but they WILL be basing their thought on what observations they can make and they will be RIGHT as far as their observations are concerned.

That last bit requires the assumption that people have lost science history and are not aware of expansion and its results, but the combination of points of view (being the same but for vastly different reasons) is an interesting way of looking at things.

EDIT: by the way, this business of folks in the past being wrong and folks in the future being wrong (but for different reasons) has led to a number of statements about how interesting it is that we happen to live in an age when we have overcome the ignorance of the past and have not yet had to succumb to the lack of observational data of the future, and thus we live in interesting times for cosmologists --- times that are unique in that way.

Personally, I'm less enthralled by that observation than some folks seem to be and here's why: The period that we live in, based on that single criteria, is going to last for MANY multiples of what is now the age of the universe and even more multiple of the age of the human race. I think those observations are mainly being made simply because we are, historically speaking, just this very minute coming out of the age of ignorance of cosmology. If people are still around in a billion years they will not be significantly further into this age than we are now, but I doubt if that thought will occur to them.
 
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