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Tags dark energy , dark fluid , dark matter

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Old 6th December 2018, 12:17 PM   #41
Belz...
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Originally Posted by Pixie of key View Post
Pushing force is ok.

Inside visible universe is it expanding pushing force.

Too much for you.

I am sorry about that.

��
Someone have a translation for that?
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Old 6th December 2018, 12:25 PM   #42
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Originally Posted by Diablo View Post
My bold. Let's see it tested then....
Yes, testable predictions ...






predicting the flow of the dark.
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Old 6th December 2018, 12:30 PM   #43
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Belz, he's saying that the pushing force is ok, it's inside the visible universe, and it's pushing forcefully, and that he's sorry that this is too much for you, all this ok pushing in full view. You just can't handle it. I myself suffer from motion sickness.
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Old 6th December 2018, 12:36 PM   #44
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Uh oh, looks like this thread is going to be pixied!
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Old 6th December 2018, 01:05 PM   #45
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Originally Posted by Steve View Post
Ok, I accept that you have insufficient knowlege to discuss this topic. You could have just said that.
I await your maths proofs, O expert.

Originally Posted by Belz... View Post
That's not how science works.
I see.

Originally Posted by Belz... View Post
That doesn't even answer the first question.
The first question is clearly based on an invalid premise. Have you stopped beating your wife yet?

Originally Posted by Belz... View Post
What are you talking about? Baron is a super-expert in physics! I know because he told me he was despite not knowing about some pretty well-known QM stuff.
Another lie, together with a personal attack. It didn't take you long.

Originally Posted by JeanTate View Post
Because you mischaracterize DE, and “scientists understand and the behavior of which they can predict”. Maybe because you have a poor understanding of both?
Both what? I asked you a question. Is that your answer?
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Old 6th December 2018, 01:20 PM   #46
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Originally Posted by baron View Post
The first question is clearly based on an invalid premise. Have you stopped beating your wife yet?
You know, the easy answer would've been "I don't believe dark matter exists", not "no".

Quote:
Another lie, together with a personal attack. It didn't take you long.
It's not a lie. Did you forget that exchange yet? As for personal attacks, you are the one who styled yourself an expert on the matter, and thus made your credentials open for critique. It's not my fault if you failed, but you're never going to live that one down, I can tell you.
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Old 6th December 2018, 01:44 PM   #47
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Originally Posted by Belz... View Post
You know, the easy answer would've been "I don't believe dark matter exists", not "no".
You mean like this?

Originally Posted by baron View Post
I don't believe dark matter or dark energy exist.
Do you even read the thread before you comment?

Originally Posted by Belz... View Post
It's not a lie. Did you forget that exchange yet?
I'll add off-topic to the list.

Originally Posted by Belz... View Post
As for personal attacks, you are the one who styled yourself an expert on the matter, and thus made your credentials open for critique. It's not my fault if you failed, but you're never going to live that one down, I can tell you.
I'm a self-styled expert? Yet another lie! I even took pains to point out the exact opposite in the very post you quoted!

Originally Posted by baron View Post
Seems to me, taking a layman's perspective, that if...

As I say, I don't know the maths...
Please stop lying.
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Old 6th December 2018, 01:57 PM   #48
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I wonder how Farnes explains the lensing effects seen in the Bullet Cluster, and elsewhere? Surely that would be the first thing he'd need to tackle?

EDIT:
Perhaps I'm barking up the wrong tree, in which case somebody will tell me so. However, if the visible matter is separated from what we perceive as DM in the Bullet cluster, and that DM is the explanation for the strength of the lensing, then surely he must tackle this. He seems to be a reputable scientist, and doesn't appear to have a history of weird ideas.
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Old 6th December 2018, 02:36 PM   #49
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Originally Posted by baron View Post
<snip>

Both what? I asked you a question. Is that your answer?
You asked “What’s wrong with that?”

My answer, clumsily, is that you mischaracterized both the things I stated/quoted. Do you now know why and how you did that, or would you like a more detailed answer?
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Old 6th December 2018, 02:52 PM   #50
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Originally Posted by JeanTate View Post
You asked “What’s wrong with that?”

My answer, clumsily, is that you mischaracterized both the things I stated/quoted. Do you now know why and how you did that, or would you like a more detailed answer?
Well, something between 'you don't understand' and a page of maths equations, tending towards the former, specifically focusing on what I actually got wrong.
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Old 6th December 2018, 02:57 PM   #51
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Originally Posted by jonesdave116 View Post
I wonder how Farnes explains the lensing effects seen in the Bullet Cluster, and elsewhere? Surely that would be the first thing he'd need to tackle?
He’s pretty clear on the limitations of the toy model he presents.

However, lensing is not even mentioned.

As I read the paper, he has chosen to tackle items of far greater importance than lensing.

Quote:

EDIT:
Perhaps I'm barking up the wrong tree, in which case somebody will tell me so. However, if the visible matter is separated from what we perceive as DM in the Bullet cluster, and that DM is the explanation for the strength of the lensing, then surely he must tackle this. He seems to be a reputable scientist, and doesn't appear to have a history of weird ideas.
It’s not straightforward to track his papers in arXiv (he seems to use several different ways of writing his name), but yes, he does seem to have a number of other, non-single author published papers.

I suspect that lensing is not covered because, in his idea, it will be the same as for a standard LCDM model, to first order effects anyway.

I think a more valid critique might be why he seems to rely on so many rather old references, especially observational.

Anyway, it’s a first paper, so no surprise that it’s far from comprehensive.
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Old 6th December 2018, 03:03 PM   #52
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Originally Posted by baron View Post
Well, something between 'you don't understand' and a page of maths equations, tending towards the former, specifically focusing on what I actually got wrong.
Thanks.

First, scientists do understand Lambda, which is the current best explanation of DE. Second, scientists can predict the behavior of Lambda. And, so far, all relevant observational results are consistent with the theory.

Do you now understand why and how your characterization is wrong?
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Old 6th December 2018, 03:45 PM   #53
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Originally Posted by JeanTate View Post
He’s pretty clear on the limitations of the toy model he presents.

However, lensing is not even mentioned.

As I read the paper, he has chosen to tackle items of far greater importance than lensing.


It’s not straightforward to track his papers in arXiv (he seems to use several different ways of writing his name), but yes, he does seem to have a number of other, non-single author published papers.

I suspect that lensing is not covered because, in his idea, it will be the same as for a standard LCDM model, to first order effects anyway.

I think a more valid critique might be why he seems to rely on so many rather old references, especially observational.

Anyway, it’s a first paper, so no surprise that it’s far from comprehensive.
OK, cheers for the explanation, JT. I think it is a highly speculative paper, but there is no harm in that. It is in a decent journal, so should get some views.

P.S. Still waiting to see if anyone cites Lerner's MNRAS paper. Hasn't happened yet.
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Old 6th December 2018, 03:46 PM   #54
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Originally Posted by JeanTate View Post
Thanks.

First, scientists do understand Lambda, which is the current best explanation of DE. Second, scientists can predict the behavior of Lambda. And, so far, all relevant observational results are consistent with the theory.

Do you now understand why and how your characterization is wrong?
Not really, no. From memory, and I stress from a layman's perspective, isn't it correct that quantum theory does not agree with calculations based on the cosmological constant to such a spectacular degree that no other calculation in science has even approached this level of inaccuracy?
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Old 6th December 2018, 03:52 PM   #55
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Originally Posted by baron View Post
Not really, no. From memory, and I stress from a layman's perspective, isn't it correct that quantum theory does not agree with calculations based on the cosmological constant to such a spectacular degree that no other calculation in science has even approached this level of inaccuracy?
Indeed.

But what does that have to do with DE (and DM)? And what does it have to do with Farnes’ paper ( the topic of this thread)?
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Old 6th December 2018, 03:57 PM   #56
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I haven't read through the whole thread yet so forgive me if this has already been asked, but wouldn't "negative matter" be anti-matter? If not why not?
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Old 6th December 2018, 03:57 PM   #57
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Originally Posted by JeanTate View Post
Indeed.

But what does that have to do with DE (and DM)? And what does it have to do with Farnes’ paper ( the topic of this thread)?
What does the cosmological constant have to do with DE? Is that what you're asking?

And I've no idea what it has to do with the paper in the OP because (a) I haven't read it and (b) I wouldn't understand it even if I did. I simply made the comment I don't believe DM and DE actually exist, which is what you took issue with. I'm still unsure of what obvious error I have made, other than you disagree.
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Old 6th December 2018, 04:01 PM   #58
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Originally Posted by Mycroft View Post
I haven't read through the whole thread yet so forgive me if this has already been asked, but wouldn't "negative matter" be anti-matter? If not why not?
I know that one. Antimatter doesn't have negative mass, only a reversed charge (as opposed to matter). That's the limit of my knowledge.
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Old 6th December 2018, 04:05 PM   #59
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Originally Posted by Mycroft View Post
I haven't read through the whole thread yet so forgive me if this has already been asked, but wouldn't "negative matter" be anti-matter? If not why not?
No. The two come from very different theories of physics: anti-matter is from QM, but experimental results so far point to it being just ordinary (positive) mass in GR; ATHENA will make this very clear (we hope).

The negative matter in Farnes’ paper comes from a somewhat overlooked aspect of GR; I’m not at all familiar with this idea ... maybe someone more familiar with GR could comment?
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Old 6th December 2018, 04:15 PM   #60
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Originally Posted by baron View Post
What does the cosmological constant have to do with DE? Is that what you're asking?

And I've no idea what it has to do with the paper in the OP because (a) I haven't read it and (b) I wouldn't understand it even if I did. I simply made the comment I don't believe DM and DE actually exist, which is what you took issue with. I'm still unsure of what obvious error I have made, other than you disagree.
Thanks.

If so, may I ask how is what you “believe” relevant, to this thread?

Your obvious error (one of them anyway) is that you feel - without much evidence - that scientists do not understand the behavior of Lambda, and cannot predict how it behaves; they do, and they can.
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Old 6th December 2018, 04:23 PM   #61
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Originally Posted by JeanTate View Post
Thanks.

If so, may I ask how is what you “believe” relevant, to this thread?
It's relevant because I'm giving my opinion on the two key factors in this thread. That's what happens on forums, people voice their opinions regarding the topic at hand.

Originally Posted by JeanTate View Post
Your obvious error (one of them anyway) is that you feel - without much evidence - that scientists do not understand the behavior of Lambda, and cannot predict how it behaves; they do, and they can.
Yeah, this is a bit like pulling teeth. I've asked several times for information on what I got wrong and the only thing you offer, other than I must be wrong because you say so, is to question how the cosmological constant has anything to do with dark energy. Something doesn't stack up here, that's all I'll say. Have a good evening.
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Old 6th December 2018, 04:28 PM   #62
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Originally Posted by baron View Post
It's relevant because I'm giving my opinion on the two key factors in this thread. That's what happens on forums, people voice their opinions regarding the topic at hand.



Yeah, this is a bit like pulling teeth. I've asked several times for information on what I got wrong and the only thing you offer, other than I must be wrong because you say so, is to question how the cosmological constant has anything to do with dark energy. Something doesn't stack up here, that's all I'll say. Have a good evening.
Thanks.

If you don’t understand the key GR equation, with Lambda in it, there’s not much more I can do ... are you prepared to at least try to understand that equation?
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Old 6th December 2018, 10:16 PM   #63
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Originally Posted by jonesdave116 View Post
I wonder how Farnes explains the lensing effects seen in the Bullet Cluster, and elsewhere? Surely that would be the first thing he'd need to tackle?

He did run two simulations, one with 45000 DM particles distributed evenly and starting motionless around a 5000 particle normal matter galaxy. It formed a non-cuspy DM halo and behaves similarly to CDM models.
He also did another large scale simulation and it also seems to give a similar DM distribution to CDM models.
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Old 6th December 2018, 10:22 PM   #64
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Originally Posted by baron View Post
I don't think we do. Seems to me, taking a layman's perspective, that if you discover that the equations you once believe described the universe only describe five percent of it, there's something wrong with those equations. Cosmologists seem to be tying themselves in knots by trying to shoehorn observations into existing theory. As I say, I don't know the maths, but that's not how I envisage science should work. First stop should be to go back to the drawing board. It wouldn't be the first time Einstein was wrong.

Your perspective is totally wrong though. Einstein's theory was never wrong, and it still isn't.
Your beliefs seem to be stuck in a pre-relativity era.
You have a lot of catching up to do.
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Old 7th December 2018, 02:36 AM   #65
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Originally Posted by Dave Rogers View Post
If it only requires a single unknown substance, then at the very least it's more parsimonious.

Dave
It requires an unkown substance with an unknown property.

Hans
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Old 7th December 2018, 02:51 AM   #66
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Originally Posted by MRC_Hans View Post
It requires an unkown substance with an unknown property.

Hans
Dark matter and dark energy require two unknown substances with unknown properties.

Dave
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Old 7th December 2018, 03:07 AM   #67
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Originally Posted by Dave Rogers View Post
Dark matter and dark energy require two unknown substances with unknown properties.
According to the so-called experts on these boards they're already proven fact and anybody who disputes this is a heretic with 'a lot of catching up to do'
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Old 7th December 2018, 03:09 AM   #68
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Originally Posted by baron View Post
You mean like this?

Do you even read the thread before you comment?
That changes nothing about your answer to "why".

Quote:
I'm a self-styled expert?
A figure of speech, man. Geez, I know it was the low hanging fruit, but you could've either addressed the actual point or ignored it altogether.

Quote:
Please stop lying.
That's like asking me to stop beating my wife.

Originally Posted by baron View Post
I know that one. Antimatter doesn't have negative mass, only a reversed charge (as opposed to matter). That's the limit of my knowledge.
And spin.
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Old 7th December 2018, 03:23 AM   #69
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Originally Posted by Belz... View Post
That changes nothing about your answer to "why".



A figure of speech, man. Geez, I know it was the low hanging fruit, but you could've either addressed the actual point or ignored it altogether.
Perhaps if you quoted the parts you're having trouble with, or disagree with, I can clarify. Making personal attacks does nothing but dig a deeper hole for yourself.

Originally Posted by Belz... View Post
That's like asking me to stop beating my wife.
Do both.
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Old 7th December 2018, 03:33 AM   #70
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Originally Posted by baron View Post
According to the so-called experts on these boards they're already proven fact and anybody who disputes this is a heretic with 'a lot of catching up to do'

OK, GR has been tested to mind boggling precision. Even if it ultimately fails and is replaced with something better, that will not change that fact that it does apply to almost the totality of spacetime and only fails under exceptionally extreme and rare conditions.


There is absolutely no doubt that the universe is expanding and started much smaller, denser and hotter.


To deny that, is to deny a host of thoroughly established facts.
Surely you need a better reason than 'I believe' for such an extreme opinion.
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Old 7th December 2018, 03:55 AM   #71
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Originally Posted by Cheetah View Post
OK, GR has been tested to mind boggling precision. Even if it ultimately fails and is replaced with something better, that will not change that fact that it does apply to almost the totality of spacetime and only fails under exceptionally extreme and rare conditions.


There is absolutely no doubt that the universe is expanding and started much smaller, denser and hotter.


To deny that, is to deny a host of thoroughly established facts.
Surely you need a better reason than 'I believe' for such an extreme opinion.
GR doesn't mandate DM, DM is something postulated to plug a discrepancy in observation, i.e. our predictions are wrong therefore there must be something out there that's completely undetectable to account for it.
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Old 7th December 2018, 05:13 AM   #72
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Originally Posted by baron View Post
GR doesn't mandate DM, DM is something postulated to plug a discrepancy in observation, i.e. our predictions are wrong therefore there must be something out there that's completely undetectable to account for it.

What discrepancy?


DM is clearly visible in how it affects orbits, causes gravitational lensing, affects large scale structure formation, etc. etc etc. directly because of GR.
It's affects are also visible in the early universe, in the CMB.


Do you know that it was quantitatively predicted in the late 80's that the presence of DM would cause redshift-space distortions on large scales? This was confirmed in 2001.



GR clearly shows the presence of invisible matter, on many scales and different times.


Is it because it's invisible that you don't like it?
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Old 7th December 2018, 05:31 AM   #73
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Originally Posted by Cheetah View Post
What discrepancy?


DM is clearly visible in how it affects orbits, causes gravitational lensing, affects large scale structure formation, etc. etc etc. directly because of GR.
It's affects are also visible in the early universe, in the CMB.
That's one way of putting it, kind of like "Oh, we've found thus stuff, we'll call it dark matter, now what does it do?". Another way is that most of the universe was found not to behave as predicted and an entity called DM was proposed to explain it. We know DM is a hypothesis, that shouldn't be in dispute. And increasing numbers of scientists don't see a need for it.

Originally Posted by Cheetah View Post
Do you know that it was quantitatively predicted in the late 80's that the presence of DM would cause redshift-space distortions on large scales? This was confirmed in 2001.
I do indeed.

Originally Posted by Cheetah View Post
GR clearly shows the presence of invisible matter, on many scales and different times.

Is it because it's invisible that you don't like it?
Visibility isn't an issue. Undetectability is, even if it's not a word.
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Old 7th December 2018, 06:04 AM   #74
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Originally Posted by baron View Post
Perhaps if you quoted the parts you're having trouble with, or disagree with, I can clarify.
I did.

Quote:
Making personal attacks does nothing but dig a deeper hole for yourself.


Quote:
Do both.
Lie and beat my wife? No thanks. And I'll note you just asked me to commit a crime.
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Old 7th December 2018, 06:29 AM   #75
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Bee, at Backreaction, on this paper: http://backreaction.blogspot.com/201...-have-not.html

There’s a comment by Farnes, well worth reading, as is Bee’s response.

Tl;dr version: a LOT more work needed, and the idea may be fatally flawed.
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Old 7th December 2018, 06:34 AM   #76
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Originally Posted by MRC_Hans View Post
It requires an unkown substance with an unknown property.

Hans
Nitpick: negative mass is not unknown; Farnes makes a case that it’s not often discussed, but has a very good (theoretical) pedigree. Likewise, Farnes claims at least some properties are known (again, theoretically).

Per my link above, at least someone who knows their GR far better than I do rather strongly disagrees with Farnes.
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Old 7th December 2018, 06:36 AM   #77
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Originally Posted by baron View Post
According to the so-called experts on these boards they're already proven fact and anybody who disputes this is a heretic with 'a lot of catching up to do'
That is quite a strong statement! Somewhat at odds with the facts, I feel.
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Old 7th December 2018, 07:14 AM   #78
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Originally Posted by baron View Post
Yeah, this is a bit like pulling teeth. I've asked several times for information on what I got wrong and the only thing you offer, other than I must be wrong because you say so, is to question how the cosmological constant has anything to do with dark energy. Something doesn't stack up here, that's all I'll say. Have a good evening.
GR doesn't tell us what the value of Lambda is, but we can get that from observation, and plugging that value into the theory returns results that are consistent with everything that we see.

When we try to use QM to predict what the value should be, as you say we get a value that is 120 orders of magnitude off. But we can't actually do that calculation, so we do one that approximates it, which means that it may be off because of those parts of the calculation that we are leaving out (this is where ideas like supersymmetry come in). On the other hand maybe this is a sign that QM is wrong and we need a new theory from which to derive the value of Lambda. Some also suggest that the value can't be derived but varies in different regions of the multiverse.

But all of those issues are issues with deriving the value of Lambda, not about whether or not Lambda is a valid part of GR.

ETA To make an analogy, Newton didn't tell us the value of G, that had to be determined through experiment (and wasn't known until after Newton's time), but that wasn't a problem with his theory, and if we'd had some other theory through which a failed attempt to derive G had been made, that wouldn't have been a knock against Newton either.
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Last edited by Roboramma; 7th December 2018 at 07:18 AM.
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Old 7th December 2018, 07:35 AM   #79
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Originally Posted by baron View Post
Neither.



I don't think we do. Seems to me, taking a layman's perspective, that if you discover that the equations you once believe described the universe only describe five percent of it, there's something wrong with those equations. Cosmologists seem to be tying themselves in knots by trying to shoehorn observations into existing theory. As I say, I don't know the maths, but that's not how I envisage science should work. First stop should be to go back to the drawing board. It wouldn't be the first time Einstein was wrong.

This statement:

"I don't know the maths"

Makes this statement worthless:

"Cosmologists seem to be tying themselves in knots by trying to shoehorn observations into existing theory."


Unless and until you can do the maths, you're just guessing.


Oh, and:

It's all just a model.

The model is never actually going to be the thing modeled. The object of the exercise is to arrive at something that consistently, accurately describes whatever it is you're studying.
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Old 7th December 2018, 12:10 PM   #80
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Originally Posted by Dave Rogers View Post
Dark matter and dark energy require two unknown substances with unknown properties.

Dave
Dark matter as hypothesized in not unknown, it is a WIMP like a nutrino, just much more massive.
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