So there is no need for bigbang-theory?

[Hello2]

If there is a redshift of light in the universe because of distance,

then galaxies that move away with constant velocity seem to move away with acceleration.

So there is no need for bigbang-theory?

[Bufofrog]

12 minutes ago, Hello2 said:

If there is a redshift of light in the universe because of distance,

The redshift is due to the expansion of space.

12 minutes ago, Hello2 said:

then galaxies that move away with constant velocity seem to move away with acceleration.

The recession velocity is proportional to the distance, due to expansion.  There is no movement through space so there is no acceleration.  The expansion of space has began to increase but that is not the reason for the red shift.

You need to be a bit clearer what you are asking.

12 minutes ago, Hello2 said:

So there is no need for bigbang-theory?

The BBT matches observations.

Edited September 11, 2020 by Bufofrog

[joigus]

There still is a need for the BB. Extrapolation backwards of receding galaxies makes inevitable some kind of bang.

The cosmic background radiation, the remnant of the explosion, is the best evidence. It has exactly the frequency spectrum of light filling all of space and continually cooling off (at different rates following known phases of cooling) for 13.7 billion years give or take.

So yes, there must have been a big bang.

[Janus]

15 minutes ago, Hello2 said:

If there is a redshift of light in the universe because of distance,

 

then galaxies that move away with constant velocity seem to move away with acceleration.

 

So there is no need for bigbang-theory?

 

If the universe were not expanding, we would not see any red shift with distance.   Thus the increasing red-shift we see with increasing distance is evidence that the universe is expanding over time, and was smaller in the past than it is now.  If we extrapolate back in time, we get the  very dense, very hot state of the Big Bang.

The acceleration of the the expansion over time is evidenced by the exact relationship between red-shift and distance.

There are three possible scenarios for an expanding universe. All of them will show a red-shift:

Case 1:  expansion slows over time

Case 2: expansion remains constant over time.

Case 3: expansion speeds up over time.

Only in case 2 will there be a perfect direct relationship between distance and red-shift, where doubling the distance exactly doubles the red-shift.

In the other two cases,  doubling the distance results in a red-shift that is not an exact doubling.  Whether it is less than double or more than double distinguishes between the two cases.

We have found that the red-shift distance ratio indicates that the universe's expansion rate has been increasing over time, and thus the rate of the expansion is accelerating.

 

 

[Hello2]

On 9/11/2020 at 8:15 PM, Hello2 said:

If there is a redshift of light in the universe because of distance,

then galaxies that move away with constant velocity seem to move away with acceleration.

 

I’m having questions with this:

Is it so that the further the galaxie, the larger the redshift?       

And: Are there galaxies with a constant redshift, or is it so that all galaxies with a redshift have a redshift that is increasing?

[Genady]

49 minutes ago, Hello2 said:

Is it so that the further the galaxie, the larger the redshift?       

For most galaxies, yes, it is so. For the very close galaxies, e.g. Andromeda, no.

51 minutes ago, Hello2 said:

And: Are there galaxies with a constant redshift, or is it so that all galaxies with a redshift have a redshift that is increasing?

The redshift didn't change in the last 100 years.

[zapatos]

Did you get lost on the way back from the bathroom? 😁

The further the galaxy, the larger the redshift. But this is only true on the scale of superclusters. For galaxies that are gravitationally bound the expansion of space has no impact on redshift.

If a galaxy is receding at constant velocity, the redshift will be constant. The recession of nearby galaxies will not be due to the expansion of space, and therefore they can be receding at a constant velocity.

 

Edit: x-posted with Genady.

Edited April 17, 2022 by zapatos

[Janus]

11 hours ago, Hello2 said:

I’m having questions with this:

 

Is it so that the further the galaxie, the larger the redshift?       

 

And: Are there galaxies with a constant redshift, or is it so that all galaxies with a redshift have a redshift that is increasing?

 

Further objects only have a larger red-shift due to the fact that the universe is expanding.  If the universe did not expand, there would not be any change in red-shift with distance.

The amount that the red-shift of any particular galaxy will have changed over the period we have been measuring them is too small to notice.

But that doesn't mean that we can't measure how fast the universe was expanding in the past.  When we look at the light from a galaxy, that light tells us the state of that galaxy when the light we see now left it.  The further the galaxy is away from us, the longer it takes the light to reach us.  Thus, as we look at galaxies further and further away, we are seeing them as they were when the universe was younger and younger than it is now.  That includes how fast they were receding from us, and the red-shift that the recession produces.

If the rate of expansion had been constant over time, you would see a one to one relationship between distance and red-shift measurements of recession speed.  If you measure anything else, that means that the rate of expansion has changed over time. It is that simple.

[beecee]

On 9/12/2020 at 4:15 AM, Hello2 said:

If there is a redshift of light in the universe because of distance,

 

then galaxies that move away with constant velocity seem to move away with acceleration.

 

So there is no need for bigbang-theory?

The redshift observed and measured, is a cosmological redshift, or a redshift caused by the expansion of space, not a Doppler redshift determined by the galaxies themselves moving away.

This along with other areas of evidence such as the CMBR re-enforces the BB model of universal/space/time evolution.

19 hours ago, Hello2 said:

Is it so that the further the galaxie, the larger the redshift? 

This is what is known as the Hubble Constant. https://www.google.com/search?q=hubble+constant&rlz=1C1RXQR_en-GBAU952AU952&oq=hubble+constant&aqs=chrome..69i57j0i512l9.6544j0j7&sourceid=chrome&ie=UTF-8

Hubble constant, in cosmology, constant of proportionality in the relation between the velocities of remote galaxies and their distances. It expresses the rate at which the universe is expanding.

19 hours ago, Hello2 said:

   And: Are there galaxies with a constant redshift, or is it so that all galaxies with a redshift have a redshift that is increasing?

The cosmological expansion (redshift)observed is seen over the larger scales of the universe. Over smaller scales such as our Local group of galaxies, and clusters of galaxies, the increased mass/energy density and consequently gravity, over such regions, sees such regions decoupled from the overall cosmological expansion, much as for example, a fish (galaxy)swimming upstream at 10 kms/hr, against  a current (space expansion) of 8 kms/hr. Over such high mass/energy density regions, we may see a Doppler Blueshift. eg: Milky Way and Andromeda.

Edited April 17, 2022 by beecee