Naked Science Forum

Non Life Sciences => Physics, Astronomy & Cosmology => Topic started by: jeffreyH on 08/06/2019 23:04:20

Title: Is the expansion of the universe inertial?
Post by: jeffreyH on 08/06/2019 23:04:20

A gravitational field makes free fall equivalent to an inertial frame. Can the same principle be applied to whatever drives the accelerated expansion of the universe?

Title: Re: Is the expansion of the universe inertial?
Post by: Halc on 09/06/2019 01:49:44

Pretty good question if you ask me.  Yes, it is equivalent in that like gravity, any acceleration is locally undetectable.  Expansion itself is completely inertial and requires no force/dark-energy at all.  But accelerated expansion does.  You mention acceleration in your post, but not in the title.

Title: Re: Is the expansion of the universe inertial?
Post by: jeffreyH on 09/06/2019 11:00:25

Quote from: Halc on 09/06/2019 01:49:44

You mention acceleration in your post, but not in the title.

That was on purpose.

Title: Re: Is the expansion of the universe inertial?
Post by: Bored chemist on 09/06/2019 11:24:36

Quote from: Halc on 09/06/2019 01:49:44

Yes, it is equivalent in that like gravity, any acceleration is locally undetectable.

Sat on my chair, and watching the springs compress, I can detect local gravity.

Title: Re: Is the expansion of the universe inertial?
Post by: yor_on on 24/06/2019 19:53:49

Maybe?

you could take a look at this one. https://phys.org/news/2017-03-expansion-universe-dark-energy.html It puts a different 'spin' on the acceleration.