Redshift: Speed of Light & Beyond?

In summary, the amount of redshift observed in galaxies is directly related to their distance from us, with more distant galaxies exhibiting higher redshift values due to the rapid expansion of space. This can explain why some galaxies appear to be moving away faster than others. Additionally, galaxies that are beyond 14 billion light years away from us are moving away at speeds greater than the speed of light, which is not a violation of Special Relativity but rather a result of the expansion of space.
  • #1
EMFsmith
33
0
Just a little confused about amounts of redshift, I read somewhere about redshift and how some galaxies are moving at redshift 3 (I think), which was said to be at or near the speed of light, then later in the article is said a galaxy was found to be moving at redshift 6.

I understand how the universe is expanding, and its this expansion that is increasing the distance, what I don't get is how some things are moving away faster than others, Is it relevant to their distance from us or something?

So any help here would "ease my worried mind, ooooh". :smile:
 
Physics news on Phys.org
  • #2


EMFsmith said:
Just a little confused about amounts of redshift, I read somewhere about redshift and how some galaxies are moving at redshift 3 (I think), which was said to be at or near the speed of light, then later in the article is said a galaxy was found to be moving at redshift 6.

I understand how the universe is expanding, and its this expansion that is increasing the distance, what I don't get is how some things are moving away faster than others, Is it relevant to their distance from us or something?

So any help here would "ease my worried mind, ooooh". :smile:

Galaxies that are farther away are moving away more rapidly than galaxies that are closer to us. This is because space is expanding more rapidly as the distances increase. The farther something is, the more rapid its motion away from us. In fact, if you keep looking far enough, you'll find galaxies moving near the speed of light away from us, because space is expanding that fast at those distances.

In case you do not know, anything that is beyond 14 billion light years away from us is moving away from us at GREATER than the speed of light. This means that it is beyond the observable part of our universe and we cannot see it because the light that has left those places have not reached us. This does not violate Special Relativity because the galaxy is not moving at greater than the speed of light relative to the space around it, but because the expansion of space around it is so great, it exceeds the speed of light.
 

1. What is redshift?

Redshift refers to the phenomenon where light waves from distant objects in the universe appear to have longer wavelengths and lower frequencies when observed from Earth. This is due to the expansion of the universe causing the light to be stretched as it travels towards us.

2. How does redshift relate to the speed of light?

Redshift is directly related to the speed of light as it is a measure of how much the wavelength of light has been stretched. The higher the redshift, the faster the object is moving away from us, and the longer its wavelength will appear to us. The speed of light is considered a universal constant, so it does not change, but the redshift allows us to measure the relative speeds of objects in the expanding universe.

3. What can we learn from studying redshift?

Studying redshift allows us to understand the movement and expansion of the universe and its objects. It also provides evidence for the Big Bang theory and helps us measure the distances of galaxies and other celestial objects. Redshift can also provide insights into the composition and evolution of the universe.

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

Yes, redshift can be used to estimate the age of the universe through the Hubble Law, which states that the more distant an object is, the faster it is moving away from us. By measuring the redshift of distant objects and using the Hubble constant, scientists can estimate the age of the universe to be around 13.8 billion years.

5. Is there a limit to how far redshift can measure?

Redshift can measure the distance of objects up to a certain point, known as the observable universe, which is estimated to be around 46 billion light-years in radius. This is because beyond this point, objects are moving away from us faster than the speed of light, making them undetectable by redshift. This does not mean that the universe ends at this point, but rather that we cannot observe objects beyond it due to the limitations of redshift and the speed of light.

Similar threads

B Experimental evidence on cosmological redshift
    • Cosmology
Replies
34
Views
2K
I Doppler and Searchlight (Headlight)
    • Special and General Relativity
Replies
21
Views
484
B What value of z (redshift) equals apparent superluminal recession?
    • Cosmology
Replies
28
Views
1K
B Detecting cosmological redshift in an empty part of the Universe
    • Special and General Relativity
Replies
5
Views
790
B Difference between special relativity and redshift?
    • Special and General Relativity
Replies
11
Views
1K
B Speed of Push vs Speed of Light
    • Other Physics Topics
Replies
5
Views
2K
B For object 3.26 million light-years away, light redshifted by 70 km/s
    • Cosmology
Replies
12
Views
1K
B Can the "creation" of space in the Universe affect the speed of light?
    • Cosmology
Replies
6
Views
489
I Have I got the right picture for cosmological redshift?
    • Cosmology
Replies
2
Views
2K
I Challenges to the Redshift Method and Hubble's Law
    • Astronomy and Astrophysics
Replies
5
Views
2K

Hot Threads

Recent Insights

Back
Top