[DungeonMaster]

How can they know the distance of the most distant galaxies and then say the Red Shift is lower? They use the Red Shift to determine that distance.

[ETL]

How can they know the distance of the most distant galaxies and then say the Red Shift is lower? They use the Red Shift to determine that distance.

Redshifts are determined by estimating the distances to objects via other distance measuring techniques. Then a distance is associated with that particular redshift.

From the article: "Hubble and Gaia performed their measurements by examining Cepheid variables, a type of star that brightens and dims in a predictable pattern. The pattern allows scientists to learn how far away these stars are from us. The data is then used to measure the universe's expansion rate, which is also called the Hubble constant. That constant is also used to estimate the age of the universe, which makes it a fundamental equation for astronomers."

[Don Corleone]

How can they know the distance of the most distant galaxies and then say the Red Shift is lower? They use the Red Shift to determine that distance.

What do the Democrats have to say about the Red Shift within their party? Is it faster on the east or west coast? By how many light years per parsec? Drs. Schummer and Pelosie want to know as do Sheldon Cooper and George Soros.

[Phlyer]

They use the Red Shift to determine that distance.

The red shift is just a first-order way to estimate the distance. If the Hubble Parameter (which used to be called the Hubble Constant when people thought it was constant) was a simple constant, that's a straightforward calculation. When it became more complex it becomes more of a table lookup, but as a first order it's still fairly valid. By that, it means that for items without some better way to estimate their distance, it's a good start.

The best way to estimate the distance to some deep space object is by measuring the apparent brightness of something with a known absolute or intrinsic brightness. The article mentions Cepheid variables which are a very good way to do that, and form the basis for Edwin Hubble's first recognition that the universe was much larger than the Milky Way, and eventually to identify the Hubble Constant. However, in detail it is known to have limitations because some galaxies are influenced by galactic clusters and so their relative motion is not solely due to the expansion of the universe. For example, Andromeda galaxy is approaching us, not receding.

Type 1A supernovae are the most distant distinctly observable phenomena for which we believe we know the intrinsic brightness and enough about the spectrum that we can determine both their absolute distance (from apparent versus intrinsic brightness) and relative velocity (from red shift of the spectrum). They are the main reason we now think the Hubble "Constant" is not really constant, but drops off with distance (or, conversely, increases as you get closer in distance and time). That accelerating expansion is not explained by gravity - in fact, it contradicts the expected effect of gravity. Since the velocity (and hence energy) of observed objects seems to be increasing, they call the mechanism we can't otherwise detect "dark energy."

[Migraine]

Circular reasoning is very much in vogue nowadays.