Redshift is due to the expansion of the universe

In summary, the cosmological redshift is caused by the expansion of the universe and affects all light emitted by a moving object. This is due to the effects of special and general relativity on the wavelength of light. Gravity also plays a role in the redshifting of light. Everyday forces of attraction prevent objects from experiencing redshift on smaller scales. Other types of waves, such as sound waves, also experience redshift. Additional explanations and diagrams can be found on Wikipedia.
  • #1
phobowute
1
0
Okay, from what I understand, the cosmological redshift is due to the expansion of the universe. I'm confused as to how this works. I don't understand why, if the universe is expanding, that the waves don't just have farther to travel. I also don't understand what is waving or why other things don't get 'redshifted'. Why isn't my bed farther from the wall than it was yesterday? Also, how do we know that the redshift isn't due to a heavy object near the 'edge' of the universe? Could someone explain redshifting in further detail?
 
Physics news on Phys.org
  • #2


The waves do have farther to travel. But since the light moves at the same speed regardless of how fast their source is moving (special relativity), its wavelength is different when viewed by someone who's not moving at the same speed as the source.

It's not just light from distant galaxies that gets shifted. All light that's emitted by a moving (relative your frame of reference) object gets shifted (in your frame of reference).

Then there's gravitational redshift, which is due to general relativity. In brief gravity curves space-time, so things in a gravitational field get 'stretched'; including light.
 
  • #3


None of this has anything to do with quantum physics, by the way, just classical wave theory.

Why isn't my bed farther from the wall than it was yesterday?

Gravity holds, say, Earth to rotating around the sun; mostly electrostatic forces hold the Earth together, and even gravity between your bed and the wall is much stronger than any separation effects. The cosmological expansion or redshift is called that because it's only over vast cosmological distances, not even within a galaxy for example, where the expansion overcomes everyday forces of attraction.

I don't understand why, if the universe is expanding, that the waves don't just have farther to travel. I also don't understand what is waving or why other things don't get 'redshifted'.

They do, even sound waves from a passing vehicle or train for example...

You can get some physical explanations and diagrams here:
http://en.wikipedia.org/wiki/Doppler_shift
 

What is redshift and how is it related to the expansion of the universe?

Redshift is a phenomenon in which light from distant galaxies appears to be shifted towards the red end of the spectrum. This is due to the expansion of the universe, which causes the wavelengths of light to stretch as the galaxies move further away from us.

Why is redshift considered evidence for the expansion of the universe?

Redshift is considered evidence for the expansion of the universe because it shows that the galaxies are moving away from each other, rather than staying in a fixed position. The amount of redshift observed in a galaxy is directly proportional to its distance from us, providing further evidence for the expansion of the universe.

How does the expansion of the universe cause redshift?

The expansion of the universe causes redshift because as space expands, the wavelength of light also expands. This stretching of the light waves is what causes the shift towards the red end of the spectrum, as longer wavelengths are associated with the color red.

Does redshift only occur in visible light?

No, redshift can occur in all types of electromagnetic radiation, including radio waves, microwaves, infrared, ultraviolet, X-rays, and gamma rays. This is because the expansion of the universe affects all types of wavelengths in the same way.

Can redshift be used to measure the age of the universe?

Yes, redshift can be used to estimate the age of the universe by measuring the rate at which galaxies are moving away from each other. This, combined with other observations and calculations, has led to the current estimate of the age of the universe being 13.8 billion years.

Similar threads

I Expansion of Space: Questions on How the Universe Works
    • Quantum Physics
Replies
1
Views
812
I Is there an equivalent "redshift" for cosmic rays due to expansion?
    • Cosmology
Replies
14
Views
397
I Sachs-Wolfe effect in a Dark Energy universe?
    • Cosmology
Replies
1
Views
1K
B Detecting cosmological redshift in an empty part of the Universe
    • Special and General Relativity
Replies
5
Views
785
I Can the integrated Sachs-Wolfe & the Rees-Sciama effects have any influence on matter?
    • Cosmology
Replies
0
Views
258
B For object 3.26 million light-years away, light redshifted by 70 km/s
    • Cosmology
Replies
12
Views
1K
B Universe rate of expansion: speeding up or slowing down?
    • Cosmology
Replies
5
Views
1K
I Expansion of the Universe and the cosmological principle
    • Cosmology
Replies
9
Views
1K
I Galaxy redshift and thermodynamics
    • Thermodynamics
Replies
10
Views
2K
B The accelerated expansion of the universe; redshift and time/distance
    • Cosmology
Replies
3
Views
2K

Hot Threads

Recent Insights

Back
Top