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Webb and Hubble confirm Universe's expansion rate

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Re: Webb and Hubble confirm Universe's expansion rate

#71

Post by vlovich123 »

dwattttt wrote: post #49
explaininjs wrote: post #26

Earlier quoted context omitted.

> Of course, all the results have error bars. Not to mention the underlying philosophical assumptions, such that the "rate of time" has been constant across all of... time. Aka: How do we know a "year" 13 Billion "years" ago bears any resemblance to one now? What would it mean for it not to?

How do we know ? Observations we can make plus models that relate those to the things we can't observe directly.

Unfortunately we can’t observe fundamental things like “what are the rules of physics and time at the beginning of the universe?”. We look for clues and make large assumptions, but given that the universe experienced a 10^78 factor expansion during the Big Bang, assuming that actually happened, then why would it make sense to assume that the rules of the universe today are the rules for the very early beginning of the universe? A strand of DNA would become 10 light years. Given that relativity redefined our understanding of basic physics but only applies as we approach the speed of light, it would stand to reason that the rules of physics would be different from our current models based on today’s observations when the matter of the universe is packed much more tightly together.

Re: Webb and Hubble confirm Universe's expansion rate

#72

Post by digging »

arcastroe wrote: post #46

I've asked this question before, but I don't think I received a good answer, so figured I'd try asking again. How do we know that galaxies are accelerating away from us and not moving at constant speed? People often point to the observation that the further away a galaxy is, the faster it appears to be moving away from us, implying acceleration. However, wouldn't we expect to see the same observation even without any…

It's because the movement is ascribed to the expansion of space itself, not the individual galaxies. We don't have any reason to believe galaxies are moving in random directions at random speeds (not at scales that explain the redshifts we call the expansion of the universe).

In your explanation, I think we'd expect to see some very distant, very slow-moving galaxies moving toward us. And there may be some very fast-moving galaxies close to us that just started really far away. Objects would be entering our local universe from outside it, and that simply doesn't happen.

Re: Webb and Hubble confirm Universe's expansion rate

#73

Post by yokoprime »

chadcmulligan wrote: post #64
harywilke wrote: post #50

Earlier quoted context omitted.

It's amazing that barely a 100 years ago The Great Debate in astronomy was weather the Milky Way was the extent of the universe or things like Andromeda were their own 'island universes'. In the 1920s, Edwin Hubble showed that Andromeda was far outside the Milky Way by measuring Cepheid variable stars. These are the same stars that we are measuring today in this debate. https://en.wikipedia.org/wiki/Great_Debate_(ast…

And not much longer before that the discussion was how long would the sun last - 5,000 years or so was the estimate if it was a big ball of burning gas (source: A scientific American article I read, wish I could find it again, hoping someone here knows)

I think it’s this one you’re referring to https://www.scientificamerican.com/article/experts-doubt-the...

Re: Webb and Hubble confirm Universe's expansion rate

#74

Post by hinkley »

rf15 wrote: post #53
tzs wrote: post #28

A little background based on a few articles about this plus my recollection of PBS Space Time videos on this: There are at least two ways to try to figure out the rate of expansion of the universe (which is called the Hubble Constant). • From variations in the cosmic microwave background (CMB) which are the result of certain conditions in the early universe it is possible to figure out what the expansion rate should…

This, together with the endless philosophising around dark energy, dark matter and whatnot paints a pretty strong arrow towards our models having some flaws when it comes to their large-scale application. I hope to live long enough to see where we made our mistake and get a better model.

I still have $20 down on "We are living in a universe inside a black hole."

Re: Webb and Hubble confirm Universe's expansion rate

#75

Post by [deleted] »

harywilke wrote: post #42

Dr.Becky goes over this in a video [0] from a year ago about the divergent results obtained by the two main ways we measure the rate of expansion. Cosmic Microwave Background Vs. Supernovae. As the accuracy of each method has improved, the end results have diverged. [0] 'theJWST just made the "Crisis in Cosmology" WORSE' https://www.youtube.com/watch?v=hps-HfpL1vc&t=858s

[deleted]

Re: Webb and Hubble confirm Universe's expansion rate

#77

Post by fsckboy »

given that a telescope conceived while Bill Clinton was president in the 1990's got named so as to complete the name "Webb Hubble", let's please please please call the next telescope "Chelsea".

https://pagesix.com/wp-content/uploads/sites/3/2020/02/chels...

https://www.wnd.com/wp-content/uploads/2015/10/Webb-Hubbell_...

(Chelsea Clinton's resemblance to Clinton family friend Webb Hubble has prompted speculation...)

Re: Webb and Hubble confirm Universe's expansion rate

#78

Post by px43 »

runeb wrote: post #62
arcastroe wrote: post #46

I've asked this question before, but I don't think I received a good answer, so figured I'd try asking again. How do we know that galaxies are accelerating away from us and not moving at constant speed? People often point to the observation that the further away a galaxy is, the faster it appears to be moving away from us, implying acceleration. However, wouldn't we expect to see the same observation even without any…

Their light is more red shifted the farther away they are. I'm no expert on this, but I believe in a constant-speed scenario they would have equal red shift no matter the distance

As I understand it, if the expansion was constant, farther away stuff would still be more red shifted. Stuff twice as far away appears to be moving twice as fast. It helps me to imagine the expansion of a metal cookie sheet, where the two edges are moving apart faster relative to each other compared to the speed that they're moving away from the center.

The surprising bit is that the far away stuff seems to be even more red shifted than that, so we're not just expanding, but the rate of expansion seems to be accelerating.

Re: Webb and Hubble confirm Universe's expansion rate

#79

Post by [deleted] »

rf15 wrote: post #53
tzs wrote: post #28

A little background based on a few articles about this plus my recollection of PBS Space Time videos on this: There are at least two ways to try to figure out the rate of expansion of the universe (which is called the Hubble Constant). • From variations in the cosmic microwave background (CMB) which are the result of certain conditions in the early universe it is possible to figure out what the expansion rate should…

This, together with the endless philosophising around dark energy, dark matter and whatnot paints a pretty strong arrow towards our models having some flaws when it comes to their large-scale application. I hope to live long enough to see where we made our mistake and get a better model.

[deleted]

Re: Webb and Hubble confirm Universe's expansion rate

#80

Post by NemoNobody »

colechristensen wrote: post #69
arcastroe wrote: post #46

I've asked this question before, but I don't think I received a good answer, so figured I'd try asking again. How do we know that galaxies are accelerating away from us and not moving at constant speed? People often point to the observation that the further away a galaxy is, the faster it appears to be moving away from us, implying acceleration. However, wouldn't we expect to see the same observation even without any…

If your idea was the case there would always be new things from very far away heading towards us, this is not the case. If the universe is flat and infinite there would be no end in supply of new galaxies with all velocities and you would always have the same mix as the initial mix of velocities. That’s not what we see.

I'm so glad "the infinite universe" as an idea is finally falling off. It works great in the Hitchhikers Guide, I love the floopy mattresses and planets that grow screwdrivers but nothing real is infinite.

I didn't even realize how many people held that belief til that article about how the universe isn't as big as we thought

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