We know that the space is expanding because of the redshift of the galaxies but, how can we compare the color we are receiving with the color they really are concluding the redshift if we do not even know their colors? Or do we know them?
How do we know that the galaxies are "green apples"?
It's not that the colors are different from what they "really are" it's that we see the color changing (wavelength getting bigger) which must mean the galaxies are receding from us.
Spectral patterns.
Each element and molecule has it's own emission/absorption spectrum determined by it's electronic structure. The spectrum describes the frequencies of light that the atom/molecule can accept or emit, which depends on the differences in energy levels between electron orbitals, which critically depends on the composition of the atom/molecule.
Thus, spectral patterns act as a sort of fingerprint that scientists can use to determine chemical composition by just looking at light.
When redshift occurs, a spectral pattern appears shifted, but otherwise has the same shape. By matching up the "fingerprints" and seeing how much they shifted, we can determine redshift.
Make sense?
>which must mean the galaxies are receding from us.
why
I'll give you an analogy. If you see a car and it's getting smaller, what does that mean?
you cant even make a google search?
They dont compare the light of galaxies but the light coming from a specific type of supernovas. The luminosity of this type of supernovas is a specific amount, thus they can compare it.
>implying we see galaxies getting smaller
Bad troll or just too fucking retarded to not understand what an analogy is?
Pic related, there's redshift there too
>spectral patterns act as a sort of fingerprint that scientists can use to determine chemical composition by just looking at light.
The problem is that the light may have been shifted.
>By matching up the "fingerprints" and seeing how much they shifted, we can determine redshift.
We do not know the "fingerprint" because we cannot be sure about the chemical composition since the light may have been shifted.
That makes sense
What analogy you faggot? I don't see a color shift in moving cars
But doesn't theory stated that speed of light is not relative, but absolute for each
>The problem is that the light may have been shifted.
That's not "the problem", that's the solution.
>We do not know the "fingerprint" because we cannot be sure about the chemical composition since the light may have been shifted.
For each element, we get spectral lines with the same relative positions. From the difference between what we see and we measure here on Earth we can directly calculate the redshift.
Educate yourself about some basic spectroscopy before spouting off bullshit like that.
The speed is the same, the frequency varies.
You cannot determine the composition by looking at its wavelenght because the wavelenght may have been contracted or expanded depending on wether the star is moving closer or not. Since you do not know the composition you cannot compare wavelenghts. Thus, redshifting cannot be calculated.
That's the problem.
If there were only one wavelength, you'd be right. But we consider the spectrum (lots o frequencies), not just a single frequency.
Make sense?
Yeah, it does.
>wave travel millions of years, but we still somehow get exactly same spectrum and frequency.
this is wrong.
It's a simplification to be sure, but this is more or less the idea. Everything else is just elaboration.
Of course some spectral lines will be missing/added/shifted due to intervening dust. Of course there will be a multitude of other spectra in the signal corresponding to other elements that compose the object being observed.
But applying what we know about physics, chemistry, and astronomy, these aren't insurmountable obstacles.
Btw, the topic of the thread is about redshift, so of course the frequency stays the same. Then again, it is pretty remarkable that light can travel billions of light years only to end it's journey in your eye when you look up. Remarkable as it may be, it's what happens.
>Then again, it is pretty remarkable that light can travel billions of light years only to end it's journey in your eye when you look up. Remarkable as it may be, it's what happens.
Well, there's a whole fucking lot of it out there, and it's ultimately not going anywhere.
>ultimately not going anywhere
The photon being massless means it has no rest frame; it HAS to move.
Photons going at c means that spacetime has contracted completely in their perspective. They CAN'T move.
Do the photons actually slow down or is it that their wave just gets stretched out.
nasa.gov
>holy shit guys! how we explain this? oh, let's add some more mysterious dark matter.
Dark energy*
The point of science is to explain what we observe. If what we model doesn't match up with observation, the model needs to be modified. We aren't a religion here.
...
Why do you think you're smarter than those scientists at NASA?
>has no rest frame
Explain pls
The way I understand the redshift is, that the space between ,,waves" of light is expanding, causing increase in wavelength. Atom is mostly composed of empty space
>what causes us to believe, that this space isn't expanding?
But we don't get the same frequencies, we get red shifted frequencies. We do, however, get the same energy differences which can then be used to calculate the frequency shifts and thus the red shift.
>which must mean the galaxies are receding from us
Assuming that the doppler effect is indeed the causant for red shift.
Now prove that the doppler effect is the ONLY possible explanation for the red shift.
Protip: You can't
The shift is unanimous. And ull see the spectralpattern shifted. This new pattern cant be anything else then shifted.
Its that simple. This science is not a lazy-boy cook-up. Its serious and a wast amount of papers concluding if and what would be possible othervice.
Protip: You'r making assumptions based on your feelings of authority on "uncertainty".
There is way to much hobby-philosophers by the birth of internet. That speed-reads shit all day and think they see a faulty pattern because of thiis.
>look at my evidence
>"""""photos""""" must be real
>The shift is unanimous. And ull see the spectralpattern shifted. This new pattern cant be anything else then shifted.
I don't saw any patterns. Sorry, but i can't believe a guys who recalc their ""constants" every year.
Well that is simply your own missfortune. No one else is effected my good fellah.
>Protip: You'r making assumptions based on your feelings of authority on "uncertainty".
Well I'm not asuming that it's plainly wrong, but it's really hard to belive, if you think about it, that everything is expanding and at such speeds. Having very little evidence of it, if any, doesn't help either. Believing something like "it's a property of light" seems much more feasable, but of course you can't assume that those two are the only explanations neither. In any case most things on science have strong obsvable evidence, the expansion of the universe is not on of those.
The argument that something is ,,hard to believe, therefore false" is invalid in scientific conversation. But you planted the seed of doubt. So go ahead. Find a way to test your thesis. We might learn something new about the universe
>The argument that something is ,,hard to believe, therefore false" is invalid in scientific conversation
Yep it's inavlid and that's why I have not said it, I've pointed that it's hard to belive, not that it's false. So why to point it? Becouse this way the alternatives seem more feasable. Are they really? Objectively speaking we don't know, but it's common to favor the hipotesys of your ancestors, to contrast with that bias was the intention of my statement.
>We know
>how can we compare
>we are receiving
>we do not even know
>do we know them?
>How do we know
What do you mean by "we", Peasant?
>dark matter
>not dark energy
Also,
>saying "mysterious" as if it's a bad thing
Of course it's fucking mysterious, we don't know what it is. Would you rather scientists came up with an idea for what it is without knowing?
eh its a bait