Register

Adv. Query

Q&A (4871)

Reviews (203)

Open problems (47)
Meta (439)

Site Statistics

206 submissions , 164 unreviewed
5,103 questions , 2,249 unanswered
5,355 answers , 22,798 comments
1,470 users with positive rep
820 active unimported users
More ...

Is the early cosmos subject to gravitational time dilation?

195 views

Since the early universe was much more dense and clumpy (evidence are the SMBHs detected by JWST at high redshift) than today, gravitational time dilation due to the stronger gravitational potential of matter should result. But why do cosmologists ignore these effects and agree on a linear cosmic time scale and a corresponding continuous cosmological redshift for describing the evolution of the universe?

asked Sep 7 in Astronomy by rhkail (0 points) [ no revision ]
recategorized Sep 8 by Dilaton

The relation between redshift and look-back time can be found for example in Bergström, Goobar "Cosmology and Particle Astrophysics". This look-back time is the difference in cosmological time between "now" and a given event in the past. The derivation in the book is based on the Robertson-Walker metric and thus presupposes a homogeneous and isotropic universe (i.e., no clumpiness (at least not on cosmological distances)).

As for clumpy matter: The effects of time dilation are most notable in the vicinity of the clump. Viewed at large scale, such a clump is a "particle" in an on average homogeneous universe.

commented Sep 9 by Flamma (110 points) [ no revision ]

Your comment on this question:

To answer, leave an answer instead. Comments are usually for non-answers.
To mask links under text, please type your text, highlight it, and click the "link" button. You can then enter your link URL.
To alert a user, please use the "@" command and remove spaces from the username, example, the user "John Doe" should be pinged as "@JohnDoe", while the user "Johndoe" should be pinged as "@Johndoe". The post author is always automatically pinged (unless you are the post author).
Please consult the FAQ for as to how to format your post.

Live preview (may slow down editor) Preview

Your name to display (optional):

Email me at this address if a comment is added after mine:

Privacy: Your email address will only be used for sending these notifications.

Anti-spam verification:

[captcha placeholder]

Please complete the anti-spam verification

Your answer

Please use answers only to (at least partly) answer questions. To comment, discuss, or ask for clarification, leave a comment instead.
To mask links under text, please type your text, highlight it, and click the "link" button. You can then enter your link URL.
Please consult the FAQ for as to how to format your post.
This is the answer box; if you want to write a comment instead, please use the 'add comment' button.

Live preview (may slow down editor) Preview

Your name to display (optional):

Email me at this address if my answer is selected or commented on:

Privacy: Your email address will only be used for sending these notifications.

Anti-spam verification:

If you are a human please identify the position of the character covered by the symbol $\varnothing$ in the following word:
p$\hbar$ysicsOve$\varnothing$flow
Then drag the red bullet below over the corresponding character of our banner. When you drop it there, the bullet changes to green (on slow internet connections after a few seconds).

Please complete the anti-spam verification

user contributions licensed under cc by-sa 3.0 with attribution required

Your rights

...