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The universe is expanding faster than expected

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Re: The universe is expanding faster than expected

#201

Post by dotancohen »

atomi wrote: post #151
taude wrote: post #127

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 episode…

There is also one of my favorite talks tangentially related by Lawrence Krauss. He explains that eventually a civilization exploring the universe around them will only see it's own galaxy and likely believe that's all there is. We are living in an extraordinary time where we are still able to see other galaxies. https://www.youtube.com/watch?v=7ImvlS8PLIo

So what could be out there that we can't see anymore? Or even more though-provoking, what could be out there that we can't see yet?

Re: The universe is expanding faster than expected

#202

Post by bbbobbb »

bencollier49 wrote: post #200
vecter wrote: post #190

Earlier quoted context omitted.

More space. It's pretty nuts. Imagine you were stretching a rubber band. What's in-between two points on that rubber that was stretched? Just rubber, albeit thinner and less dense. In our universe, however, the space that's created is the same as the space that was just there. It'd be like if the rubber band stretched, but didn't lose any density while it did so. Insane, I know.

So as the universe grows, am I growing as well? How much is the space inside me growing on a daily basis?

No. The expansion is only apparent on intergalactic scale. On human scale, and even much larger scales, it does not overcome the fundamental forces. You're not expanding.

Re: The universe is expanding faster than expected

#203

Post by mr_mitm »

grishka wrote: post #156
pdonis wrote: post #115

Earlier quoted context omitted.

> 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.

> There is no question about whether the universe is expanding. Why? > we have two different theoretical models that are giving different answers, and we don't understand (yet) how to reconcile them. Maybe... just maybe... that's because it isn't actually expanding, but there's some other, unknown effects at play? It's about time we think outside the box. To me, as a regular programmer kind of person, the very idea t…

There is much more evidence for the expansion of the universe than just the cosmological redshift.

Where do you get the idea that it "makes the calculations work out"? You got it backwards. The calculations showed that the universe must expand. Georges Lemaitre found that out. People were skeptical at first and said the calculations don't apply, but when the cosmic microwave background was discovered in the sixties, all but the most stubborn hardliners were convinced that the universe must expand and that there must have been a big bang, i.e. a singularity in the finite past.

The microwave background is basically a picture of the universe when it was a baby. There were no galaxies, only hot gas that just cooled down enough to turn from plasma to neutral gas which later clumped into galaxy clusters, galaxies and so forth. Because the speed of light is finite, we can literally see how the universe looked liked billions of years ago. And it looked hot, because it was compressed, and it looked young, because structures hadn't had the time to form yet. The gas composition also shows only light elements, because heavy elements need to be forged in supernovae. Young stars have lots of heavy elements, far away, old stars only consist of hydrogen and a bit of helium.

The tiny, tiny irregularities that we see in the cosmic microwave background match beautifully what we know about thermodynamics, statistical physics, quantum mechanics, general relativity and electrodynamics to a very high degree. It's marvelous, really.

> the very idea that the universe is expanding makes about as much sense as dark matter

The universe does not care about what makes sense to us. It just is. And the expansion is an observational fact.

On a side note, I find it a bit presumptuous to assume that a layperson knows better than legions of professional cosmologists. These are very smart people who work full time for the better parts of their lives on these problems while you clearly haven't put in the time to understand the fundamentals. They wouldn't come to the conclusions they come to if they didn't think they had merit. You can be curious about it, you can have questions about it (please do!), you don't have to understand it, but please trust experts on their opinion and show some humility and some respect. I'm sure you wouldn't appreciate a physicist who tried to tell you how to design your programs either. (We're known to write horrible software, just look at ROOT.) Imagine some amateur telling you "for-loops don't make sense to me, why don't you use GOTO". No offense, and sorry to say it like this, but it really bugs me a bit.

Re: The universe is expanding faster than expected

#204

Post by dotancohen »

brodie wrote: post #183
johnnujler wrote: post #181

Earlier quoted context omitted.

Ah! That makes sense. I realise that talking about complex concepts in terms of analogy can be misleading, but is it like the fabric is elastic and long enough and is only getting stretched? Is there a way to reconcile this with the (3 dimensional) inside and outside aspect of our experiences.

I think it’s more like the balloon analogy or baking bread analogy is required because there’s no good way to explain what we observe without either analogies or math or unintuitive descriptions. That doesn’t mean there can’t be a higher spatial dimension that our observable universe is part of; we just haven’t observed it or can’t observe it. I guess we’re sort of like ants crawling on the surface of an opaque, seem…

  > That doesn’t mean there can’t be a higher spatial dimension
  > that our observable universe is part of; we just haven’t
  > observed it or can’t observe it.
Maybe we can not observe higher spatial dimensions, but we can observe a force that seems to propagate in higher spatial dimensions, thus there seems to be evidence of those dimensions.

Light intensity, gravity, and electromagnetism decay at 1/r^2, which is the same rate at which the area of the surface of an expanding 3D bubble grows. So each unit of light / gravity / electromagnetism could be seen as taking up a specific "patch" of expanding area.

However, the strong nuclear force decays much faster than 1/r^2. In fact, at some distance it goes negative and then decays back to zero. This could be (wild speculation) a force that propagates in many more dimensions. And it's not the only force that does this, the weak nuclear force also decays much more rapidly than 1/r^2 with distance.

I'm not a physicist and I would love nothing more than to hear what holes could be punched into this hypothesis.

Re: The universe is expanding faster than expected

#205

Post by dotancohen »

bbbobbb wrote: post #202
bencollier49 wrote: post #200

Earlier quoted context omitted.

So as the universe grows, am I growing as well? How much is the space inside me growing on a daily basis?

No. The expansion is only apparent on intergalactic scale. On human scale, and even much larger scales, it does not overcome the fundamental forces. You're not expanding.

So, it was the donuts?

Re: The universe is expanding faster than expected

#206

Post by cygx »

User23 wrote: post #150
lisper wrote: post #134

Earlier quoted context omitted.

> physics is a laboratory science That would come as news to most theoretical physicists, who rarely set foot in a laboratory. > we can ... produce quarks How do you know we can produce quarks? Also, where does astronomy fit into your taxonomy? Was Newton doing science or phenomenology when he came up with the inverse square law? Plate tectonics? What about (drum roll, please) biology?

> That would come as news to most theoretical physicists, who rarely set foot in a laboratory. I agree that it's fair to describe cosmologists as a species of theoretical physicist, given the long standing connection between the observation of heavily bodies and the birth of the modern physical sciences. Still the relation is rather remote. > How do you know we can produce quarks? I personally don't. I'm relying on h…

I agree that it's fair to describe cosmologists as a species of theoretical physicist, given the long standing connection between the observation of heavily bodies and the birth of the modern physical sciences. Still the relation is rather remote.

This is such a weird statement to make.

Let's not forget how we got where we are:

There are two forces active on macroscopic scales, electromagnetism and gravity. At the turn of the previous century, there were some inconsistencies in the way how electromagnetism fit into the rest of physics, which were resolved by the theory of Special Relativity. That shifted the problem to gravity, leading to the theory of General Relativity.

Friedmann then calculated what solutions General Relativity permitted under the assumption of spatial symmetry, the Friedmann models, which form the foundation of the cosmological standard model.

Most of the things I described so far happened before we even had confirmation that other galaxies existed (Friedmann published his 2nd paper in 1924, while Hubble resolved the 'Greate Debate' in 1923 by discovering Cepheids in the 'Andromeda Nebula', nowadays 'Andromeda Galaxy'). That shifted the focus on trying to figure out the model parameters that made Friedmann's model fit reality, and we've been at it ever since.

Re: The universe is expanding faster than expected

#207

Post by hnhnhnhnhn »

amelius wrote: post #59
eloff wrote: post #6

Earlier quoted context omitted.

I appreciate your optimism. I tend to be optimistic about the future myself. But there is no law of the universe that everything will work out ok. Only if we make the right decisions as a species and we don't get unlucky. I'm quite apprehensive that the great filter lies ahead - that technology accelerates too rapidly compared to our wisdom and we end up nearly destroying ourselves. We're getting the ability to progr…

> I appreciate your optimism. I tend to be optimistic about the future myself. But there is no law of the universe that everything will work out ok. Isn't there some QM law that says that with infinitesimal probability anything can materialize at any point in space? Meaning that after everything has collapsed, you can (will!) still re-materialize somewhere in space. An infinite number of times!

https://en.wikipedia.org/wiki/Boltzmann_brain

Re: The universe is expanding faster than expected

#208

Post by Fifer82 »

taude wrote: post #127

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 episode…

I think he was a software engineer before retirement, I absolutely love his video's for the reasons you highlighted. I can tell he is interested in the subject matter and spending retirement creating these videos is very noble. I started to lose comprehension of scale after the first few and a dozen more followed.

Re: The universe is expanding faster than expected

#209

Post by brodie »

dotancohen wrote: post #204
brodie wrote: post #183

Earlier quoted context omitted.

I think it’s more like the balloon analogy or baking bread analogy is required because there’s no good way to explain what we observe without either analogies or math or unintuitive descriptions. That doesn’t mean there can’t be a higher spatial dimension that our observable universe is part of; we just haven’t observed it or can’t observe it. I guess we’re sort of like ants crawling on the surface of an opaque, seem…

> That doesn’t mean there can’t be a higher spatial dimension > that our observable universe is part of; we just haven’t > observed it or can’t observe it. Maybe we can not observe higher spatial dimensions, but we can observe a force that seems to propagate in higher spatial dimensions, thus there seems to be evidence of those dimensions. Light intensity, gravity, and electromagnetism decay at 1/r^2, which is the sa…

You may not be a physicist but you’d make a convincing string theorist!

I say that partly pejoratively, with a Sabine Hossenfelder sort of jocular but judgmental tone.

I’m personally excited to see how astrophysicists will take dark matter out of its darkness and cast it into intuitive lights, like some have with the rising dough analogy for cosmic expansion.

Re: The universe is expanding faster than expected

#210

Post by dotancohen »

867-5309 wrote: post #187
dave_sid wrote: post #93

Earlier quoted context omitted.

I don’t think this joke quite got the credit it deserves.

> The Big Freeze (or Big Chill) is a scenario under which continued expansion results in a universe that asymptotically approaches absolute zero temperature. https://en.m.wikipedia.org/wiki/Ultimate_fate_of_the_univers... absolute zero == zero kelvin == 0K

https://en.wikipedia.org/wiki/867-5309/Jenny
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