Thread: The BA: HOW FAST IS THE UNIVERSE EXPANDING?

1. The BA: HOW FAST IS THE UNIVERSE EXPANDING?

http://www.syfy.com/syfywire/how-fas...it-and-thats-a

The universe is expanding.

Wow, I still love being able to write that down. It's such a wonderful, compact, simple statement, yet has implications so profound it may be decades before we understand them all. And we've known it to be true for a century already.
A century already? Instead of "a century almost"? Don't we still have a dozen years to go?

Is no one paying attention??
Last edited by grapes; 2018-Feb-28 at 10:38 AM. Reason: Merged

2. I stupidly read the comments and I can no longer think straight.

3. Order of Kilopi
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the BA just got his time-dilation calculations wrong. This is what happens when you travel around the galaxy in a flying saucer.

4. Originally Posted by grapes
http://www.syfy.com/syfywire/how-fas...it-and-thats-a

A century already? Instead of "a century almost"? Don't we still have a dozen years to go?
i just read it as “nearly a century already” (the “already” just expresses surprise at the length of time). We only have 4 years till a century from Friedmann’s initial theoretical work, another 5 for Lemaître’s use of the red shift data (already more than a century old) to calculate the rate of expansion, another year for Hubble’s publication ...

But it depends how you define “known”. I wouldn’t date that until the 1960s.

5. Well, it was 1912 when Vesto Slipher got those galactic redshifts. I suppose we could average that in for a general date.

6. Originally Posted by Solfe
I stupidly read the comments and I can no longer think straight.
I like the one from Matthew Wilson yesterday
The two distance units cancel (leaving a 3.086e+19 factor behind), leaving inverse seconds, which is a frequency. The expansion of the universe can be measured in Hertz! Looks like 2.3 × 10^-18 hertz, give or take. That's a frequency of about once every 70 billion years.
And then answered by Owen Gwynne
I'd say you've overthought this.
The reduction of the Hubble Constant to ~2.3 e-18 s-1 is simply the inverse of the age of the universe, ~13.7 Billion years.
So, how did Matthew come up with 70 billion? Did he just borrow the "70" from Hubble?

7. if he did a frequency thing, 2pi enters and makes it 86 billion which is a hand wave around 70 billion??

8. Originally Posted by grapes
So, how did Matthew come up with 70 billion? Did he just borrow the "70" from Hubble?
I can't imagine. I can only think he made a mistake with his calculation.

9. Originally Posted by profloater
if he did a frequency thing, 2pi enters
Only if you are expressing the frequency in radians, surely?

10. Banned
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Originally Posted by grapes
http://www.syfy.com/syfywire/how-fas...it-and-thats-a

A century already? Instead of "a century almost"? Don't we still have a dozen years to go?

Is no one paying attention??

A ''universe still expanding'' may be a compact statement, but it much more poetic to say

''the big bang it still happening.''

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