# Have we measured the change in the red shift over time?

• I
• Justin Hunt
In summary: This is a way to measure the change in redshift of distant galaxies as they're moved across the foreground galaxy(s). However, this measurement is only precise to within 1%.Is it possible to measure a change in red shift of distant objects due to this acceleration?.
Justin Hunt
Have experiments been done to measure the red shifts of distant objects over time? If inflation is correct, the the speed at which an object is receding relative to us is based on how far away that object is located. Therefore, the most distant objects would also have the highest acceleration. Is it possible to measure a change in red shift of distant objects due to this acceleration?

I am a bit of a skeptic of the expanding universe conclusion we derived by comparing red shift values to brightness when it could be explained with actual velocities versus expansion of space time or some combination of the two. In my opinion testing changes in red shift over time would be the most decisive way to determine what part of the velocity is due to actual velocity and what part is due to the expansion of space between us and the distant object.

Justin Hunt said:
Have experiments been done to measure the red shifts of distant objects over time? If inflation is correct, the the speed at which an object is receding relative to us is based on how far away that object is located. Therefore, the most distant objects would also have the highest acceleration. Is it possible to measure a change in red shift of distant objects due to this acceleration?.

This is called redshift-drift, and it occasionally come up here at Physics Forums. See,

https://www.physicsforums.com/threa...or-cosmological-redshift.617506/#post-3981620

DanielMB, rootone and PeterDonis
Justin Hunt said:
I am a bit of a skeptic of the expanding universe conclusion we derived by comparing red shift values to brightness when it could be explained with actual velocities versus expansion of space time or some combination of the two. In my opinion testing changes in red shift over time would be the most decisive way to determine what part of the velocity is due to actual velocity and what part is due to the expansion of space between us and the distant object.
There's no difference between the description of our universe as "stuff is moving apart" and "space is expanding". They're two different ways of describing the exact same phenomenon. Each description has strengths and weaknesses in terms of providing understanding of what's going on.

rootone
Keep in mind the rate of expansion is absolutely microscopic compared to the size of the universe. The Hubble constant is about 70 km/sec/MEGAparsec. That translates into about 7x10-9% per year. We cannot measure redshift with such phenomenal accuracy - even at vast distances over many, many years. Scientists have come up with a very clever effortt using gravitational lensing as described here; https://arxiv.org/abs/1703.05142, Redshift drift of gravitational lensing

## 1. What is red shift and why is it important to measure?

Red shift is the phenomenon in which light from an object appears to have a longer wavelength, or is shifted towards the red end of the electromagnetic spectrum, due to its relative motion away from the observer. It is important to measure because it can provide information about the expansion of the universe and the rate at which galaxies are moving away from each other.

## 2. How is red shift measured?

Red shift is measured using a spectrometer, which separates light into its different wavelengths. The amount of red shift is determined by comparing the observed wavelength of an object to its expected wavelength based on its known velocity. This measurement is expressed as a value called the redshift z.

## 3. Has the change in red shift over time been measured?

Yes, the change in red shift over time, or the rate at which the universe is expanding, has been measured through various observational techniques. These include measurements of the cosmic microwave background radiation, the luminosity and distance of Type Ia supernovae, and the clustering of galaxies.

## 4. What have we learned from measuring the change in red shift over time?

By measuring the change in red shift over time, scientists have been able to confirm the theory of the expanding universe and estimate the age of the universe. They have also discovered that the expansion of the universe is accelerating, which has led to the theory of dark energy.

## 5. Are there any uncertainties in measuring the change in red shift over time?

Yes, there are uncertainties in measuring the change in red shift over time, as with any scientific measurement. These uncertainties can be caused by various factors such as observational errors, systematic errors, and assumptions made in the measurement methods. However, scientists continue to refine their techniques and measurements to reduce these uncertainties and improve our understanding of the universe.

• Cosmology
Replies
14
Views
2K
• Cosmology
Replies
16
Views
2K
• Cosmology
Replies
49
Views
3K
• Cosmology
Replies
15
Views
2K
• Cosmology
Replies
23
Views
3K
• Special and General Relativity
Replies
132
Views
6K
• Cosmology
Replies
3
Views
1K
• Special and General Relativity
Replies
46
Views
3K
• Cosmology
Replies
2
Views
2K
• Cosmology
Replies
3
Views
1K