B Why does expansion redshift light if....

[unwillingly ignorant]

isn't expansion essentially making more space rather than moveing us in it? So why does it redshif light?

Or is that just a super facile explanation of expansion that they explain people like me who wouldn't get it?...

 

[phinds]

isn't expansion essentially making more space rather than moveing us in it?

No.

So why does it redshif light?

It carries photons away from us (slightly) as they are traveling towards us. Since they always travel at c, they are traveling at c when they reach us but because of the expansion's effect, they are red shifted.

Or is that just a super facile explanation of expansion that they explain people like me who wouldn't get it?...

No, it is an exact description of what is happening.

EDIT: One of the things that will presumably occur to you eventually, if it has not already, is the following. The photons start out at c at a certain frequency. They get to us still traveling at c but at a lower frequency. This CLEARLY says that they lost energy somewhere along the way. OK, since energy has to be conserved, where does that energy GO ?

The answer is that is doesn't "go" anywhere, it just disappears, and this is OK because "conservation of energy" is a local effect and does not apply on a cosmological scale. This is one of the many things that made me tear my hair out and say bad words when I first encountered it.

 

[unwillingly ignorant]

Ok.. I'm grabing clumps of hair ready to tear. Sooo is it essentially, literally streatching the photons' wave frequency as space is added/streached(?)?

Was that just a totaly nonsense question?

 

[PeterDonis]

Sooo is it essentially, literally streatching the photons' wave frequency as space is added/streached(?)?

No. The redshift of photons with the expansion of the universe is due to spacetime curvature. In a curved spacetime, photons can redshift (or in some cases blueshift) because of the curvature. More precisely, a photon traveling between two observers in a curved spacetime can redshift (or blueshift) depending on the relationship between the worldlines and the geometry of the curved spacetime.

 

[unwillingly ignorant]

riiight.. So it's a bit like those depictions of gravity where the grid stretches down into a gravity well except.. Everywhere at once, and not 2D, and it's the bending of those lines that shifts the frequency.. Am i anywhere close with that?

 

[PeterDonis]

it's a bit like those depictions of gravity where the grid stretches down into a gravity well except.. Everywhere at once, and not 2D, and it's the bending of those lines that shifts the frequency.. Am i anywhere close with that?

Not really, because the "grid lines" you are thinking of are coordinate dependent, and the redshift/blueshift of photons is not; it is there regardless of the coordinates you choose (which means regardless of how you draw "grid lines" in spacetime).

 

[unwillingly ignorant]

that's what i meant by "everywhere at once".. I think..?
anyway, wouldn't that just result in a uniformed shift that wouldn't tell us anything?

 

[PeterDonis]

that's what i meant by "everywhere at once".. I think..?

I don't see how.

wouldn't that just result in a uniformed shift that wouldn't tell us anything?

I don't understand what you are referring to here. The redshift/blueshift of photons being independent of your choice of coordinates does not mean it's the same for all photons and all observers. It just means that for a given photon and a given observer, the redshift/blueshift is the same regardless of what coordinates you choose to describe it. But your description in terms of "space stretching" only applies in a particular set of coordinates.

 

[m k]

isn't expansion essentially making more space rather than moveing us in it? So why does it redshif light?

Or is that just a super facile explanation of expansion that they explain people like me who wouldn't get it?...

Is your "more space" more spacetime, distance or something else?

Redshift is a name of something that is observated, just like (cosmological)expansion and (energy)conservation.
For now they don't add up.

 

[phinds]

just like (cosmological)expansion and (energy)conservation.
For now they don't add up.

What do you mean "for now they don't add up" ? They will NEVER add up since it is known that energy conservation does not apply on cosmological scales.

 

[m k]

As I understand "known" I wouldn't say so.

 

[phinds]

As I understand "known" I wouldn't say so.

Well, then you should study some cosmology.

 

[rootone]

isn't expansion essentially making more space rather than moveing us in it

Yes.

So why does it redshif light?

Because the speed of light is constant, while wavelength depends on gravity and/or dark energy ... *insert math stuff here*

 

[Khashishi]

If the light wave is traveling through space, and you stretch out space, then you stretch out the wavelength of the wave. The distance between two peaks or troughs has increased.

 

[m k]

Well, then you should study some cosmology.

I have now studied some of it and learned that we know quite a bit of few percents of it and a bit less of the rest.

Still wouldn't say so.

Should you now study some definition [can't include maths here] fine tuning?

 

[phinds]

I have now studied some of it and learned that we know quite a bit of few percents of it and a bit less of the rest.

Still wouldn't say so.

Then you still have not come to terms with the fact that while yes indeed there are tons of things we know little about, energy conservation on cosmological scales is not one of them. There is no energy conservation on cosmological scales and if you continue to insist that there is, you are simply ignoring reality.

 

[PeterDonis]

I have now studied some of it and learned that we know quite a bit of few percents of it and a bit less of the rest.

This is not a fair statement of our current theories of cosmology.

Still wouldn't say so.

Then you have not understood what you have studied.

In any case, the OP's question has been answered. Thread closed.