1. Join Date
Feb 2017
Posts
18
Originally Posted by Reality Check
Proper distance is the distance that we actually measure.
Through what means do we measure extra-galactic proper distance?

2. Order of Kilopi
Join Date
Aug 2008
Location
Wellington, New Zealand
Posts
3,142
The Cosmic distance ladder is something you should already know about since learning about the mainstream is part of the process of creating an against the mainstream idea. You should certainly know how Hubble measured extra-galactic proper distance (Cepheid variable stars) given the number of times that I have cited Hubble's law.
Last edited by Reality Check; 2017-Mar-27 at 09:02 PM.

3. Join Date
Feb 2017
Posts
18
Originally Posted by Reality Check
The Cosmic distance ladder is something you should already know about since learning about the mainstream is part of the process of creating an against the mainstream idea. You should certainly know how Hubble measured extra-galactic proper distance (Cepheid variable stars) given the number of times that I have cited Hubble's law.
Cepheid Variables are based on measurements on apparent magnitude, and knowledge of absolute magnitude. How is it not a measurement of luminosity distance that this method yields?

4. Order of Kilopi
Join Date
Aug 2008
Location
Wellington, New Zealand
Posts
3,142

5. Originally Posted by Reality Check
The Cosmic distance ladder is something you should already know about since learning about the mainstream is part of the process of creating an against the mainstream idea.
To clarify this statement: while it is certainly a very, very good idea to understand the mainstream science you seek to modify or overturn, our rules do not require prerequisite knowledge of it. On the other hand, the ATM forum is not the place to ask for instruction about mainstream theories. You can ask questions in the Q&A forum where you'll get mainstream answers that you may not dispute on an ATM basis. This thread is about your claims and your defense of them.

6. Join Date
Feb 2017
Posts
18
We can get recessional velocity V_r from this alternate model with this form:

then using hubble's law, we can divide this speed by H_o to yield Proper distance.

So there's Proper Distance. I've graphed them out to z=10 against the equation from conventional cosmology: recessional velocity, Proper Distance

Realitycheck, I believe you are in error about the measurability of proper distance on extragalactic scales:

"With few exceptions, distances based on direct measurements are available only out to about a thousand parsecs, which is a modest portion of our own Galaxy. For distances beyond that, measures depend upon physical assumptions, that is, the assertion that one recognizes the object in question, and the class of objects is homogeneous enough that its members can be used for meaningful estimation of distance."

"While the Hubble law distance is in principle measurable, the need for helpers all along the chain of galaxies out to a distant galaxy makes its use quite impractical. Other distances can be defined and measured more easily."

Hubble's law is also an approximation that doesn't accurately describe our universe observationally on large scales. The Proper distance that you are referencing is absent from the cosmology calculators and is not defined mathematically in the wikipedia articles that you are linking. Maybe proper distance=luminosity distance in gravitationally bound regions, but if you are measuring luminosity, as is the case in virtually every extra-galactic measurement technique including cepheids, you are yielding luminosity distance.

, again, note the D_l.

7. Order of Kilopi
Join Date
Aug 2008
Location
Wellington, New Zealand
Posts
3,142
Originally Posted by substitutematerials
...then using hubble's law,
That is where you go wrong making the post moot. Hubble's law is derived from mainstream cosmology and matches empirical evidence. It is not valid in a universe where galaxies are receding away from us at the speed of light which is your ATM idea.
It is the empirical Hubble's law that states that your ATM idea is wrong because all galaxies do not recede from us at the speed of light: v = HD where v varies with distance.

ETA: Starting with a formula that seems to appear from nowhere is not wise.
Last edited by Reality Check; Today at 03:13 AM.

8. Order of Kilopi
Join Date
Aug 2008
Location
Wellington, New Zealand
Posts
3,142
Originally Posted by substitutematerials
Realitycheck, I believe you are in error about the measurability of proper distance on extragalactic scales:
Your links do not show that proper distances on extragalactic scales cannot be measured or are wrong.: cosmic distance ladder.
The Ned Wright page you cited has:
Many Distances
With the correct interpretation of the variables, the Hubble law (v = HD) is true for all values of D, even very large ones which give v > c. But one must be careful in interpreting the distance and velocity. The distance in the Hubble law must be defined so that if A and B are two distant galaxies seen by us in the same direction, and A and B are not too far from each other, then the difference in distances from us, D(A)-D(B), is the distance A would measure to B. But this measurement must be made "now" -- so A must measure the distance to B at the same proper time since the Big Bang as we see now.
Hubble's law is an approximation that accurately describes our universe observationally on large scales. There are deviations from it which is why we say that the expansion of the universe is accelerating.

#### Posting Permissions

• You may not post new threads
• You may not post replies
• You may not post attachments
• You may not edit your posts
•