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The universe is expanding faster than expected

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Re: The universe is expanding faster than expected

#121

Post by Triv888 »

mountainboy wrote: post #116
desideratum wrote: post #111

Earlier quoted context omitted.

Can you refer to any specific theories that don't require expansion? (for reading)

sure! Electric Universe (Thornhill, Birkeland, Scott, et al) Plasma Cosmology (Alfven, Lerner, et al) Infinite Universe Theory (Borchardt) Recycling Universe Cosmology (Mitchell) Subquantum Kinetics (La Violette) Modern Mechanics (Bryant) Push Gravity: (various, book: Pushing Gravity) The Static Universe (Ratcliffe) Steady State Universe (Hoyle, older) That's a good start at least. ;-) All of the above have one or mo…

An infinite Universe makes the most sense, let's adopt that

Re: The universe is expanding faster than expected

#122

Post by kenjackson »

ASalazarMX wrote: post #7
akka47 wrote: post #3

I always get a feeling of existential dread when I read these kind of news.

"The aggregate of our joy and suffering, thousands of confident religions, ideologies, and economic doctrines, every hunter and forager, every hero and coward, every creator and destroyer of civilization, every king and peasant, every young couple in love, every mother and father, hopeful child, inventor and explorer, every teacher of morals, every corrupt politician, every ‘superstar,’ every ‘supreme leader,’ every…

I must admit I feel that same dread. While I appreciate your intent, I'm not sure it helped.

Re: The universe is expanding faster than expected

#123

Post by AnimalMuppet »

Triv888 wrote: post #121
mountainboy wrote: post #116

Earlier quoted context omitted.

sure! Electric Universe (Thornhill, Birkeland, Scott, et al) Plasma Cosmology (Alfven, Lerner, et al) Infinite Universe Theory (Borchardt) Recycling Universe Cosmology (Mitchell) Subquantum Kinetics (La Violette) Modern Mechanics (Bryant) Push Gravity: (various, book: Pushing Gravity) The Static Universe (Ratcliffe) Steady State Universe (Hoyle, older) That's a good start at least. ;-) All of the above have one or mo…

An infinite Universe makes the most sense, let's adopt that

Reality does not care what makes sense to you. Let's find out what's true and adopt that.

Re: The universe is expanding faster than expected

#124

Post by pdonis »

User23 wrote: post #19

One thing that really frustrates me about cosmology, or at least popular science reporting and books, is a particular kind of lack of intellectual rigor. Specifically, even as a layman, it's clear that observation and model are being conflated. Cosmology is a science in the broadest sense of being a field of human knowledge, but it isn't a science the way that, for example, physics is. It would better be described as…

> It would better be described as a phenomenology

Not really, no, because current cosmological models are not derived solely by looking at cosmological phenomena and coming up with phenomenological equations that describe them. (That is not to say that past cosmological models didn't do that; only that our current ones, roughly since the early to mid-20th century, don't.) They are derived by starting from laws of physics that already work in other domains, and seeing what those laws say about the universe as a whole.

> to be absolutely clear what the assumptions of the model are, even the most trusted ones

Cosmologists are clear about that.

> maybe this is just an issue in the popular press?

I think it is, since what I see in actual textbooks [1] and peer-reviewed papers is not at all like what you are describing.

[1] A good reasonably current textbook is Liddle's Introduction to Modern Cosmology.

Re: The universe is expanding faster than expected

#125

Post by mpoteat »

pdonis wrote: post #115
grishka wrote: post #109

> It would be incredibly exciting if there was new physics It would indeed be incredibly exciting if it would lead to a less silly explanation of the redshift than "universe is expanding".

> It would indeed be incredibly exciting if it would lead to a less silly explanation of the redshift than "universe is expanding". It won't. There is no question about whether the universe is expanding. The issue is over how fast it is expanding; we have two different theoretical models that are giving different answers, and we don't understand (yet) how to reconcile them.

Not a physicist, but why isn't the simple explanation that light loses energy over cosmological distances not also a valid explanation of redshift? We already know that energy isn't conserved at those scales.

Re: The universe is expanding faster than expected

#126

Post by chanakya »

Can someone explain why the universe is expanding at all? I've heard it said "it's the momentum from the Big Bang". That sounds reasonable, but then we're told that it's not that the galaxies are flying apart, it's that the "basic metric of space itself is expanding".

I can understand momentum from an explosion, but why would "space itself" expand because of an explosion?

Re: The universe is expanding faster than expected

#127

Post by taude »

If you're finding this interesting, I recently discovered this YouTube channel on How Far Away Is It [1]. There's a few different playlists of what he calls digital books, that are all worth watching for a novice: How Far Away is It? [2]; How Small is It [3]; How Fast is It [4]

As a side benefit, it can be soothing and nap inducing, but in the best ways. It's taken a couple attempts to get through some of the episodes, but in the end I find the explanations pretty amazing.

[1] https://www.youtube.com/user/howfarawayisit [2] https://www.youtube.com/playlist?list=PLpH1IDQEoE8QWWTnWG5cK... [3] https://www.youtube.com/watch?v=zKbZeUvPnWI&list=PLpH1IDQEoE... [4] https://www.youtube.com/watch?v=KE4SpkTOY1A&list=PLpH1IDQEoE...

Re: The universe is expanding faster than expected

#128

Post by ferbass »

akka47 wrote: post #3

I always get a feeling of existential dread when I read these kind of news.

Don't worry it will be a problem for the future politicians and universe expand protections groups. "We have to stop the universe expansion, the universe is expanding faster than expected" they say.

Re: The universe is expanding faster than expected

#129

Post by pdonis »

cygx wrote: post #62
horsawlarway wrote: post #22

Earlier quoted context omitted.

I agree with you here. A phrase that always echoes in my mind when discussing cosmology is "All models are wrong - some models are useful" The farther you venture from the verified useful section of a model (by which I mean - the farther you are from model predications that have been validated with observational evidence), the less you should trust it - ALL MODELS ARE WRONG! And for most sciences - this isn't a huge…

Note that the most distant astronomical object we've observed has a redshift of 11, corresponding to a light travel distance of 13.4Gly. This means that if our models are correct and the universe is indeed about 13.8 billion years old, then we've seen 97% of the universe's history. Including the microwave background in that pushes the number to 99.997%.

> the most distant astronomical object we've observed has a redshift of 11

And even though that seems like a large distance, it is a very small redshift compared to the total time the universe has existed. The cosmic microwave radiation background, for comparison, was emitted at a redshift of about 1100. So a redshift of 11 only covers 1 percent of the expansion of the universe since the CMBR was emitted.

> we've seen 97% of the universe's history

No, we haven't. See above.

> Including the microwave background in that pushes the number to 99.997%.

No, it doesn't, because even though we can see the CMBR, we can't see anything useful in between its redshift and the redshift of 11--not because there's nothing there, but because what's there is too distorted and faint to see. (The only reason we can see the CMBR is that it's black body radiation at a temperature we can independently predict from our knowledge of the physics of recombination, so we can tailor extremely sensitive instruments to looking for its precise signature.) So there is a lot of universe that we haven't seen.

Re: The universe is expanding faster than expected

#130

Post by azernik »

pratyushc wrote: post #120
garbagetime wrote: post #113

Earlier quoted context omitted.

Could the great filter be something like developing language? That's something that seems quite rare (only one species on Earth has it). If so, then discovering bacteria in the Solar System wouldn't be such a cause for worry.

> Could the great filter be something like developing language? Perhaps it's a combination of factors? Dolphins are social animals that appear to be capable of complex communications among themselves, but don't have hands to manipulate their environment the way we can. Apes have hands, but don't have complex language.

Another interesting one I've heard is getting into space, period. It's possible that there are other technological civilizations out there, but all stuck under a few hundred km of ice or on a 2-earth-mass monster where it's impractical to reach orbit.

Earth may only be special in being in a sweet spot between Mars (too small to hold an atmosphere or protect from cosmic radiation, hence no life) and Gliese 832c (with its low-orbit velocity of something like 15km/s, hence much less practical to put stuff in space).

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