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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

#171

Post by jjgreen »

galaxyLogic wrote: post #164
roywiggins wrote: post #103

Earlier quoted context omitted.

So, imagine the box is filled with hydrogen gas. The space inside the box gets bigger. But protons don't, they're little packets of quarks that hold each other very powerfully. You'd have to expand space very, very, very fast to rip those quarks apart from each other, and once you did, you would have a bunch of bare quarks, not hydrogen. The quarks aren't getting bigger, since they appear to be indivisible and essent…

Well so in other words "space" is NOT expanding. It's particles of matter that are moving away from each other. Right? So fine, but then why would we say that space is expanding, that would seem to imply we know there is some edge of space which is moving away from us, but what evidence do we have that space has such an edge? Saying that "space is expanding" seems to hold the assumption that space has a (limited) wid…

Mandatory: https://xkcd.com/895/

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

#173

Post by alex77456 »

flashman wrote: post #34

To know if the universe is expanding, we need to know the following: how far away things are, and whether they're moving away from us. In an accelerating universe, there's evidence that things were moving away from us slower in the past. The evidence that things are moving away from us is that as the universe expands, the wavelength of any light travelling through it also expands, shifting it towards the red end of t…

>To know if the universe is expanding, we need to know the following: how far away things are, and whether they're moving away from us

May be a stupid question but wouldn't this apply only if we knew that the universe is uniformly dense? And we only see a tiny portion of it.

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

#174

Post by saagarjha »

inakarmacoma wrote: post #126
fennecfoxen wrote: post #102

Earlier quoted context omitted.

Consider yourself. Consider a galaxy N million lightyears away that is moving away from you at high speed... Or is it really? What if it's staying perfectly still, and YOU'RE the one moving? ... How could you even tell? The principle of Relativity is that you cannot tell any difference, for the laws of physics are the same whether you are moving or the galaxy is moving. The theory of Special Relativity describes whic…

... at which point you also get to enjoy your arrival at linguistic metaphysics. If you can identify all material objects that all observers can feasibly see, then you subtract the material objects that one person sees, from the material objects the other person sees in their reference frame, and you end up with... something... that is both a material object, and not a material object at the exact same point in time.…

An unseeable material object does not cease to exist, even though it cannot affect us.

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

#175

Post by nxpnsv »

So these guys criticize SN-!a as standard candles, and then rely on other results criticizing BAO and CMB measurements also indicating accelerating expansions. However, why all these measurement would err in the wrong direction is not clear. I'm not convinced yet.

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

#176

Post by has2k1 »

mikorym wrote: post #159
has2k1 wrote: post #141

Earlier quoted context omitted.

> if you're calculations don't fit, then your mathematics is not suitable, so change the math before you change the physical description Physics is littered with mathematical formulations predicting new phenomenon (forces and particles). > What is the relationship between dark matter and dark energy There is no known relationship between dark matter and dark energy. They could have been called unknown matter and unkn…

> Physics is littered with mathematical formulations predicting new phenomenon (forces and particles). Sorry, I should have clarified: I mean I would spend all my days doubting the mathematics, rather than doubting the physical universe. If that makes sense? Of course all of mathematics can be argued to have a physical sort of root.

You cannot choose your allegiance and stick with it. The reality is that there is always various types of evidence to contend with.

Chances are if you were a physicist/cosmologist you would be of the same opinion as the majority because you would be exposed to just about the same evidence.

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

#177

Post by tiborsaas »

rs23296008n1 wrote: post #75

Good. Science is meant to be a honest search for facts: data, knowledge and wisdom. Being wrong is a feature. "I don't know" is an acceptable starting point with no shame attached. Being certain means a mountain of data to back it up. Being allowed to be wrong is a requirement. Anyone saying a scientist can't ever be wrong is likely placing oddball limits on progress that will only damage and limit the future[1]. How…

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 is very real, it's our knowledge that is dark.

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

#178

Post by BoiledCabbage »

inakarmacoma wrote: post #126
fennecfoxen wrote: post #102

Earlier quoted context omitted.

Consider yourself. Consider a galaxy N million lightyears away that is moving away from you at high speed... Or is it really? What if it's staying perfectly still, and YOU'RE the one moving? ... How could you even tell? The principle of Relativity is that you cannot tell any difference, for the laws of physics are the same whether you are moving or the galaxy is moving. The theory of Special Relativity describes whic…

... at which point you also get to enjoy your arrival at linguistic metaphysics. If you can identify all material objects that all observers can feasibly see, then you subtract the material objects that one person sees, from the material objects the other person sees in their reference frame, and you end up with... something... that is both a material object, and not a material object at the exact same point in time.…

Clearly it exists to them because it can interact with someone they can interact with.

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

#179

Post by BoiledCabbage »

igravious wrote: post #88
bananabreakfast wrote: post #77

Earlier quoted context omitted.

Speaking from the pov as a former astrophysicist, that definition of redshift is not quite accurate. While we have observed the universe expanding since Edwin Hubble published his findings 90 years ago, it was in fact the Friedmann equations produced 10 years earlier that established how it would work within the context of general relativity. The Universe is expanding at every known point at the same time at the same…

One thing I've never understood is this. How do we tell the difference between the expansion of space and the dilation of time? Given that space and time are crudely specking intertwined (spacetime) how do we know that the effect we see -- redshifting -- is due to the spatial expansion at every known "point" and not the temporal expansion (contraction?) at every known moment? Could not the spatial size of the univers…

That's the same thing that's always bothered me. That physicists never seem to discuss global time dilation - which also to my layman's eyes seems like a simpler explanation.

Time everywhere is slowing down (speeding up?) Which it's why the expansion of space seems so perfect to neither accelerate nor decelerate.

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

#180

Post by wolfram74 »

dieppe wrote: post #90
bananabreakfast wrote: post #77

Earlier quoted context omitted.

Speaking from the pov as a former astrophysicist, that definition of redshift is not quite accurate. While we have observed the universe expanding since Edwin Hubble published his findings 90 years ago, it was in fact the Friedmann equations produced 10 years earlier that established how it would work within the context of general relativity. The Universe is expanding at every known point at the same time at the same…

> The Universe is expanding at > every known point at the same > time at the same rate This part I don't get (I am in no way versed in astrophysics). If I am in a box, and that the box grows 10%, but that at the same time I grow 10%, what has changed? I mean, if every point in the universe expands at the same rate at the same time, what does it change? Relatively speaking, everything is the same size before and after…

Think about drawing two circles on a balloon, one with radius 1cm, and the other with radius 2cm. the distance between the two perimeters is 1cm, but if we inflate the balloon so that the surfaces double, now the inner circle has a radius of 2, and the outer circle a radius of 4, the distance between the perimeters has grown along side the rest of all the lengths. That's my best understanding of the situation, I mostly do non-linear classical mechanics.
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