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Evidence that the key assumption made in discovery of dark energy is in error

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Re: Evidence that the key assumption made in discovery of dark energy is in error

#281

Post by mr_mitm »

ltbarcly3 wrote: post #268
mr_mitm wrote: post #156

Earlier quoted context omitted.

Please read this and let me know if you are still convinced that energy must be conserved in General Relativity: https://www.preposterousuniverse.com/blog/2010/02/22/energy-... (edit: Nevermind, this is the same content as the Discovery article linked above, except with better formatting). In short: conservation of energy is a result from the Noether theorem, which says it must be conserved iff the laws of physics ar…

You are using circular reasoning. Energy is not conserved if the universe is expanding. I am saying of course that isn't happening, the evidence for expansion is poor and now has been shown to be unreliable. Without expansion energy is conserved. The example from your article is expansion, which it assumes to be a fact based on the poor evidence that is now invalidated.

I don't know what you are talking about. The expansion of the universe is an observational fact. The evidence is overwhelming and you'll be hard pressed to find a single professional cosmologist who won't agree.

Now whether the expansion is accelerating is another question, which is what the article of this thread is about. That's something that is still considered a fact, but the evidence is not quite as overwhelming. It's still strong, but questions about the validity of standard candles should be taken seriously.

Re: Evidence that the key assumption made in discovery of dark energy is in error

#282

Post by gbrown »

6nf wrote: post #9
gbrown wrote: post #6

Earlier quoted context omitted.

I thought there was little reason to expect a big rip, because it requires assumptions about an increasing cosmological constant, which there’s no evidence for.

What do you mean? There's lots of evidence that the expansion of the universe is accelerating and that's the whole reason we believe that dark energy exists. Most cosmologists do believe we're heading for a big rip.

The big rip would imply that eventually, all points in space are accelerating away from one another faster than the speed of light, which would tear apart atoms, subatomic particles, and everything down to the smallest divisible units of matter and energy. The accelerating expansion doesn't imply this at all, and would instead leave big dense things like galaxies intact to burn out and fade away.

Acceleration comes from the cosmological constant - more volume means more dark energy, which means more velocity (acceleration). Only if the cosmological constant isn't constant would we expect a big rip.

Now, we're questioning the acceleration part also apparently.

Re: Evidence that the key assumption made in discovery of dark energy is in error

#283

Post by gbrown »

pdonis wrote: post #40
6nf wrote: post #9

Earlier quoted context omitted.

What do you mean? There's lots of evidence that the expansion of the universe is accelerating and that's the whole reason we believe that dark energy exists. Most cosmologists do believe we're heading for a big rip.

No, "big rip" and "accelerating expansion" are not the same thing. A big rip would require that the density of dark energy in the universe is increasing with time. We have no evidence that it is, and most cosmologists do not believe we are heading for a big rip.

Exactly.

Re: Evidence that the key assumption made in discovery of dark energy is in error

#284

Post by gbrown »

rs23296008n1 wrote: post #252
tiborsaas wrote: post #177

Earlier quoted context omitted.

Dark matter is definitely not a rounding error [0]. There are multiple evidence for strong gravity effects where we just don't see the required matter the explain the observed phenomenons [1][2] [0] https://www.forbes.com/sites/briankoberlein/2016/09/23/rotat... [1] https://en.wikipedia.org/wiki/Bullet_Cluster#Significance_to... [2] http://cosmology.berkeley.edu/Education/CosmologyEssays/Grav... Briefly, dark matter…

I'm feeling verbose. So here we go. Dark matter: Maybe something that we'll one day make lunch boxes out of. Maybe also a rounding error. Of some sort. In some way. You haven't got the mountain-of-data yet. A lot-of-data is a good start. This doesn't mean the missing matter isn't some super-energy infused version of something we already know about. For all we know, its simply "ordinary" matter we'd otherwise already…

I feel like comparing dark energy and dark matter is really disingenuous. Dark energy is a placeholder to explain a really bizarre phenomenon (which is now being questioned). Dark matter is something we can map the distribution of throughout the visible universe via it's gravitational effects. We even have plausible hypotheses for what kind of stuff it might be (WIMPs etc.)

Re: Evidence that the key assumption made in discovery of dark energy is in error

#285

Post by rs23296008n1 »

gbrown wrote: post #284
rs23296008n1 wrote: post #252

Earlier quoted context omitted.

I'm feeling verbose. So here we go. Dark matter: Maybe something that we'll one day make lunch boxes out of. Maybe also a rounding error. Of some sort. In some way. You haven't got the mountain-of-data yet. A lot-of-data is a good start. This doesn't mean the missing matter isn't some super-energy infused version of something we already know about. For all we know, its simply "ordinary" matter we'd otherwise already…

I feel like comparing dark energy and dark matter is really disingenuous. Dark energy is a placeholder to explain a really bizarre phenomenon (which is now being questioned). Dark matter is something we can map the distribution of throughout the visible universe via it's gravitational effects. We even have plausible hypotheses for what kind of stuff it might be (WIMPs etc.)

And as soon as we know what it is and the phenomena responsible the naming will change. Especially when we find out its not actually "dark" and is instead x, y or z under a, b, c conditions.

Re: Evidence that the key assumption made in discovery of dark energy is in error

#286

Post by rs23296008n1 »

tylerjwilk00 wrote: post #278
rs23296008n1 wrote: post #252

Earlier quoted context omitted.

I'm feeling verbose. So here we go. Dark matter: Maybe something that we'll one day make lunch boxes out of. Maybe also a rounding error. Of some sort. In some way. You haven't got the mountain-of-data yet. A lot-of-data is a good start. This doesn't mean the missing matter isn't some super-energy infused version of something we already know about. For all we know, its simply "ordinary" matter we'd otherwise already…

Unicorns are real. They're just call by a different name, Elasmotherium sibiricum [1], a now extinct species of rhinoceros that shortly co-existed with man. [1] https://www.google.com/search?q=Elasmotherium+sibiricum&tbm=...

I consulted the relevant and qualified[0] unicorn[1] expert who presented evidence[2] to confirm this is all legitimate[3] so it is deemed[4] to be true[5]: Rhinos or mammoths can't be unicorns. There was mention about not being able to ride[6] them but that is not a convincing argument. Domestication of a more horse-like animal was the larger deciding factor.

That said I fully get how a mammoth / rhino could inspire and may actually be the real root of the folk story. While Subject Matter Experts[0] can be wrong the folk story now has its own definition[1] and physical evidence[2].

Sidenote: Now I know why Pratchett likes footnotes.

--

[0] 8 year old who has read everything about unicorns

[1] reference for the horselike resemblance https://en.wikipedia.org/wiki/Unicorn

[2] relevant toys and pictures presented as proof

[3] like a lot of political "facts"

[4] someone authoritatively says so

[5] or true enough, see [3], to meet perceptual expectations[1].

[6] rhinos can be ridden if you're suitably enthusiastic and are also able to run faster. Mammoths with horns were probably similar. This is logically not much different to how wild unicorns[1] would be so I'd not discount too much. The riding aspect is therefore a weak disqualifier.

Re: Evidence that the key assumption made in discovery of dark energy is in error

#287

Post by ltbarcly3 »

ncmncm wrote: post #274
ltbarcly3 wrote: post #267

Earlier quoted context omitted.

All of science is just a collection of observations combined with attempts to find patterns in those observations. Read up on Hume, Inductive Reasoning. There is no fundamental grounding for the idea that what any of the rules we observe the universe following won't change suddenly for no reason apart from the fact that we have never seen it happen.

Inductive reasoning works reliably in mathematics and formal logic, and literally nowhere else . So, if you have a mathematical model of physics, you can use inductive reasoning on that model, but the universe is under no obligation to obey your model. In fact, we have found our models to be violated by nature over and over , countless thousands of times. Quantum field theory and General Relativity arose specifically…

Despite the wonderfully dismissive tone of your post, it seems like you don't know what the term 'inductive reasoning' means.

> Inductive reasoning works reliably in mathematics

Mathematics does not use inductive reasoning. Inductive reasoning is not logically valid. Perhaps you have confused 'inductive reasoning' with 'the method of induction'. While there are some shared root words they are not related concepts. 'The method of induction' uses deductive reasoning, as does every mathematical proof. There are no exceptions to this, see: https://plato.stanford.edu/entries/mathematics-nondeductive/ . Mathematicians might look at examples or write computer programs to explore a problem, but when it comes time to write a proof there is no such thing as a non-deductive proof.

> In fact, we have found our models to be violated by nature over and over,

This doesn't even disagree with anything I have said.

> You may insist that red shift is not caused by universal expansion

I'm not insisting that red shift is not caused by universal expansion. I'm insisting that expansion, if it exists, violates the conservation of energy. The conservation of energy is extremely well established in that we can't find exceptions to it locally. Meanwhile expansion is extremely hard to study, and relies on connecting long chains of measurements for which we cannot reliably estimate the accuracy of.

I simply think that it is more likely, as a matter of prognostication, that it will turn out the distance ladder has significant corrections or that one of the basic assumptions underlining expansion (for example that the universe is homogeneous or isotropic outside of the visible universe) ends up being overturned.

Re: Evidence that the key assumption made in discovery of dark energy is in error

#288

Post by ltbarcly3 »

mr_mitm wrote: post #281
ltbarcly3 wrote: post #268

Earlier quoted context omitted.

You are using circular reasoning. Energy is not conserved if the universe is expanding. I am saying of course that isn't happening, the evidence for expansion is poor and now has been shown to be unreliable. Without expansion energy is conserved. The example from your article is expansion, which it assumes to be a fact based on the poor evidence that is now invalidated.

I don't know what you are talking about. The expansion of the universe is an observational fact. The evidence is overwhelming and you'll be hard pressed to find a single professional cosmologist who won't agree. Now whether the expansion is accelerating is another question, which is what the article of this thread is about. That's something that is still considered a fact, but the evidence is not quite as overwhelmin…

The expansion of the universe is consistent with our best astronomical observations. Saying it is a 'fact' is just wordplay.

Re: Evidence that the key assumption made in discovery of dark energy is in error

#289

Post by cthalupa »

ltbarcly3 wrote: post #288
mr_mitm wrote: post #281

Earlier quoted context omitted.

I don't know what you are talking about. The expansion of the universe is an observational fact. The evidence is overwhelming and you'll be hard pressed to find a single professional cosmologist who won't agree. Now whether the expansion is accelerating is another question, which is what the article of this thread is about. That's something that is still considered a fact, but the evidence is not quite as overwhelmin…

The expansion of the universe is consistent with our best astronomical observations. Saying it is a 'fact' is just wordplay.

It is a fact in as real a sense as most anything is a fact when it comes to science. Arguing against the expansion of the universe without providing any evidence whatsoever to show it isn’t expanding is a waste of time. Questioning things is fine, when productive - you are not presenting any evidence to the contrary or even a hypothesis to explain even a portion of what expansion explains, shortly after showing that your understanding of the subject matter is not solid. Please do further research on these subjects before putting yourself in a position to mislead others.

Re: Evidence that the key assumption made in discovery of dark energy is in error

#290

Post by ltbarcly3 »

cthalupa wrote: post #289
ltbarcly3 wrote: post #288

Earlier quoted context omitted.

The expansion of the universe is consistent with our best astronomical observations. Saying it is a 'fact' is just wordplay.

It is a fact in as real a sense as most anything is a fact when it comes to science. Arguing against the expansion of the universe without providing any evidence whatsoever to show it isn’t expanding is a waste of time. Questioning things is fine, when productive - you are not presenting any evidence to the contrary or even a hypothesis to explain even a portion of what expansion explains, shortly after showing that…

To what end? If someone is mislead about the interpretation of astronomical observations on a cosmological scale there is absolutely no consequence. Your sensitivity to any suggestion that the most popular interpretation may be incorrect is, to be blunt, inappropriate.

It's not my burden to prove that expansion isn't well founded. It is consistent with the best data available, however it is, in the best possible light, still a post-hoc interpretation of that data. It requires significant assumptions that do not have any basis.

So lets unpack that. Given the assumption that the universe his homogeneous, what we observe isn't different from what would be observed from any other position in the universe. Given the assumption that the universe is isotropic, the universe should be the same no matter which direction we look. There is no evidence for either of these assumptions. Since we can only observe the portion of the universe that we are able to observe, we can only assume that our cosmological observations are (in the ways we are debating here) not a function of our position in the universe. This is no different from whom we may consider a less sophisticated observer on Earth who looks around and decides that the universe is full of breathable air. After all, the universe is homogeneous and isotropic, therefore it must be entirely full of air and no matter where you look you would see air. Obviously this is not consistent with our observations, but to someone without telescopes and a modern understanding of physics it would be the logical conclusion given the same assumptions you are making.

The point is that these assumptions are assumptions. We have no evidence for them, except that the best observations we can make do not currently contradict our most recent version of the conclusions we take from those assumptions when combined with the best data we have. The problem is that this is always true, even for the unsophisticated observer who just sees air everywhere they are able to look with their primitive technology.

If you can't see why it is not valid to make these assumptions at this point you should sit and think a bit.

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