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Anonymous Tue 09 Mar 03:53:02 2021 No.12809387 View Reply Original Report

Quoted By: >>12809408

Does the CMB allow you to know exactly what time it is anywhere in the universe? Like.. if you went into stasis and woke up at an arbitrary point in the next billion or so years, could you use the CMB to tell what time it was? I got this idea from my dad and he wants to know if it works.

Anonymous

Anonymous Tue 09 Mar 2021 03:59:53 No.12809408 Report

Quoted By: >>12809432

>>12809387
Theoretically, maybe. It’s hard to say how accurate you could get.

Although I should mention there’s currently a big issue right now in cosmology concerning estimating the age of the universe because Hubble’s constant and the CMB give us two different answers. This has been known for a while, but about a year or two ago their error bounds stopped overlapping, meaning we REALLY have a problem.

Anonymous

Anonymous Tue 09 Mar 2021 04:01:52 No.12809413 Report

Quoted By: >>12809432

>>128094087
Sorry I should specify: They stopped overlapping because our instruments kept getting more and more accurate, and thus they shrunk the error bounds. We expected the two answers would just keep inching closer together, but they didn’t.

Anonymous

Anonymous Tue 09 Mar 2021 04:08:33 No.12809431 Report

Quoted By:

wouldn't it require you to already know CMB dymanics?
if you simply look at a CMB map you won't know the "time" you're at unless you know how the CMB evolves over time. the only reason we can identify our current "time" is because we have other sources to compare with.

Anonymous

Anonymous Tue 09 Mar 2021 04:08:53 No.12809432 Report

Quoted By: >>12809450

>>12809408
>>12809413
I define "now" by what we are seeing "now", i.e. along a past light cone. Does that simplify things?

Anonymous

Anonymous Tue 09 Mar 2021 04:15:07 No.12809450 Report

Quoted By: >>12809951

>>12809432
You’re think about it too much. You wanna know if you could estimate at what point in time you’re at based on the CMB, then the answer is yes. The CMB’s frequency is constantly decreasing as the universe expands, so it is possible to use the CMB as a sort of clock, albeit not incredibly accurate.

Also I think at a certain point it will be impractical because the frequency will have been too far redshifted, but that would likely be hundreds of billions of years in the future.

Anonymous

Anonymous Tue 09 Mar 2021 07:06:44 No.12809951 Report

Quoted By:

>>12809450
You can measure time as accurately as you can measure the temperature of the CMB. But it is highly dependent on your model of the expansion of the universe

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