Dark Energy, Dark Matter

How does science work? And what's all this about quantum mechanics?

Moderators: AMod, iMod

User avatar
Astro Cat
Posts: 460
Joined: Thu Jun 23, 2022 11:09 pm

Re: Dark Energy, Dark Matter

Post by Astro Cat »

Impenitent wrote: Fri Jul 01, 2022 4:29 pm I am unfamiliar with the diets of black holes, but what happens when they consume each other?

-Imp
Some more about this that I forget a lot of people don't know (you may, or may not, just saying for everyone's benefit).

Black holes aren't "holes" as they're often depicted in pop science and media. They're still clumps of matter, just extremely dense clumps of degenerate matter (a really short explanation of degenerate matter is that it's so compact that it can break Pauli's exclusion principle). So when they collide they just merge into a clump of degenerate matter the size of the clumps that collided.
User avatar
Astro Cat
Posts: 460
Joined: Thu Jun 23, 2022 11:09 pm

Re: Dark Energy, Dark Matter

Post by Astro Cat »

Age wrote: Sat Jul 02, 2022 12:55 am
Astro Cat wrote: Fri Jul 01, 2022 5:12 am The threshold for quiescence is somewhat arbitrary, but several authors place it at < 10^-11 stellar masses worth of stars /yr. For comparison, the Milky Way produces about 3 stellar masses of stars per year (and the Milky Way is on its way to quenching).
Every galaxy would be on their way to quenching, correct?
If no, then what is the opposite of quenching called?
That's the general trend; but some galaxies are increasing their star formation. Some previously quenched galaxies are "waking up," but it's definitely against the overall trend and we're still understanding what circumstances this occurs under.

There's not really a term I'm aware of for increasing star formation other than just that (increasing star formation rate).

Detecting increasing SFR is also really hard because for any given galaxy we are looking at it once (at one point in time). The reason we're able to say galaxies are quenching at all is because we look at high redshifts, see many many galaxies with good SFR's (more disks, bluer light), then we look at more local galaxies (lower redshift, more recent in cosmic time) and see many many quenched, massive, spheroid, red galaxies. It follows that over time, many galaxies have quenched. (Older stars are redder, so it makes sense that galaxies that aren't making new stars are redder; and galaxies are more massive because they've been colliding and combining, and they're less disky and more spheroid precisely because of these factors).

My team has been calling the zone between 0.6 < z < 2.5 the "High Noon" because this is generally the scope where we see galaxies go from their highest SFR's to looking more like today's galaxies.

Age wrote:
Astro Cat wrote: The scale factor of the universe, a, is defined as 1 for the present universe and is used to relate the scale of the universe at different times (and is directly related to redshift, since looking out is looking back). For instance, a = 0.5 would be the time when the universe had half of its present size.
When you use the word 'universe', what are you referring to, exactly?

And, if the scale factor of the universe is just defined as 1 for the present universe, then at every moment one is looking and observing from, half the time between that moment and when the so-called 'big bang' occurred would just be half the size correct?
By "universe" I mean the physical cosmos that we observe which is asymptotically isotropic and homogeneous at scales greater than ~100 Mpc (e.g., random samples taken at scales above 100 megaparsecs will generally be the same). This is worded carefully because on some ideas like eternal inflation there could be other cosmoses beyond the scope of the cosmos we observe.

It's not correct that just halving the time elapsed would give you half of the size of the universe from that time: this is because different energy densities have dominated at different times (first radiation, then matter, and now finally dark energy very recently) and the universe expands differently during these epochs. For instance, when matter was the dominant energy density, the expansion of the universe was actually slowing down. As soon as dark energy dominated, the expansion began to accelerate. Here's a plot from a talk I gave in 2020:

Image

We are using Type 1a supernovae to constrain how the scale factor has changed over time. The different colored lines represent different cosmologies (some without dark energy, some with varying amounts of dark energy) -- basically any model that would look like the universe we see today with a=1. Well, since looking out is looking back, if we effectively measure the scale factor in the past at different redshifts it tells us what sort of history it's had (and thus what sort of future it has).

As you can see, the scale factor doesn't just double at a set rate, but evolves in a complex way.
Age wrote: This, what you call, 'looking out to redshift', I have already partly talked about and explained in this forum is just looking back, 'temporally'.

I have also partly explained how the looking at redshift then gets misinterpreted as the whole Universe is expanding, which effects the way the people with this misinterpretation then look at what is actually occuring. This misinterpretation was like when people would look at sun's movement and misinterpret this as "evidence" for a geocentric universe, which would then effect the way they look at, and thus see, what is actually occuring. That is; that it is not the Universe, Itself, that is expanding, but rather just a part of the Universe that is expanding.

How all of this happens and occurs can be shown, explained, or illustrated, for those that are interested.
I'm not sure what you're talking about. The universe is definitely expanding. We can see it plain as day, and furthermore, models based on this expansion have matched observation so closely in some cases that the error bars (the sigma) had to literally be multiplied 400x to even be seen on a graph. It's one of the greatest triumphs of prediction-to-outcome-of-experiment in the history of science. That doesn't happen based on being as radically wrong about something as thinking the universe is expanding if it's not.

(I happen to already have such a plot uploaded, you'll note the error bars had to be inflated --> 400sigma)

Image

This plot is the measurement of the CMB blackbody temperature on the assumption of an expanding universe (temperature T has an inversely proportional relationship to the scale factor a).
Age wrote:
Astro Cat wrote: Energy densities with a positive equation of state (w = 1/3) and scales by /a^4 is simply radiation.

Energy densitites with an equation of state w = 0 and scales by /a^3 is matter.
You answered and clarified somewhat what they 'are', but not what they 'do', which was what I was asking for, and thus looking for to be clarified.
I'm not sure what you mean about what they do. Most people are familiar with radiation and matter, it's usually dark energy that laypersons are fuzzy about what it does.

What about radiation and matter are you wondering about?
Age
Posts: 20043
Joined: Sun Aug 05, 2018 8:17 am

Re: Dark Energy, Dark Matter

Post by Age »

Astro Cat wrote: Sat Jul 02, 2022 2:35 am
Age wrote: Sat Jul 02, 2022 12:55 am
Astro Cat wrote: Fri Jul 01, 2022 5:12 am The threshold for quiescence is somewhat arbitrary, but several authors place it at < 10^-11 stellar masses worth of stars /yr. For comparison, the Milky Way produces about 3 stellar masses of stars per year (and the Milky Way is on its way to quenching).
Every galaxy would be on their way to quenching, correct?
If no, then what is the opposite of quenching called?
That's the general trend; but some galaxies are increasing their star formation. Some previously quenched galaxies are "waking up," but it's definitely against the overall trend and we're still understanding what circumstances this occurs under.
There are many, many things that we are still trying to understand, but there is no need to keep informing us of this.
Astro Cat wrote: Sat Jul 02, 2022 2:35 am There's not really a term I'm aware of for increasing star formation other than just that (increasing star formation rate).
Okay.
Astro Cat wrote: Sat Jul 02, 2022 2:35 am Detecting increasing SFR is also really hard because for any given galaxy we are looking at it once (at one point in time). The reason we're able to say galaxies are quenching at all is because we look at high redshifts, see many many galaxies with good SFR's (more disks, bluer light), then we look at more local galaxies (lower redshift, more recent in cosmic time) and see many many quenched, massive, spheroid, red galaxies. It follows that over time, many galaxies have quenched. (Older stars are redder, so it makes sense that galaxies that aren't making new stars are redder; and galaxies are more massive because they've been colliding and combining, and they're less disky and more spheroid precisely because of these factors).
This is all really just common knowledge and common sense anyway.
Astro Cat wrote: Sat Jul 02, 2022 2:35 am My team has been calling the zone between 0.6 < z < 2.5 the "High Noon" because this is generally the scope where we see galaxies go from their highest SFR's to looking more like today's galaxies.
"Today's galaxies" is a very relative term. As the only galaxy that would exist within the 'today' realm' is the one that 'your team' is within. Every other galaxy 'your team' looks at and observes is really what was happening and occurring before, or in 'yesterday's realm' and term.
Astro Cat wrote: Sat Jul 02, 2022 2:35 am
Age wrote:
Astro Cat wrote: The scale factor of the universe, a, is defined as 1 for the present universe and is used to relate the scale of the universe at different times (and is directly related to redshift, since looking out is looking back). For instance, a = 0.5 would be the time when the universe had half of its present size.
When you use the word 'universe', what are you referring to, exactly?

And, if the scale factor of the universe is just defined as 1 for the present universe, then at every moment one is looking and observing from, half the time between that moment and when the so-called 'big bang' occurred would just be half the size correct?
By "universe" I mean the physical cosmos that we observe which is asymptotically isotropic and homogeneous at scales greater than ~100 Mpc (e.g., random samples taken at scales above 100 megaparsecs will generally be the same).
So, when you talk about 'the universe', you are really only looking at and talking about a part of the whole.

In other fields other than astrophysics when we use the 'Universe' word, or some use the 'universe' word, we refer to Everything, all-there-is, and totality instead.

This way we are not looking at just a narrowed and small picture of things, nor look from a very narrowed and small perspective neither.

Also, your definition explains a lot about why some people assume or believe that the Universe began and/or is expanding.

These people are only looking at a part of the whole only, and so not seeing what the actual Truth is. Well not yet anyway.
Astro Cat wrote: Sat Jul 02, 2022 2:35 am This is worded carefully because on some ideas like eternal inflation there could be other cosmoses beyond the scope of the cosmos we observe.
But that way of wording the Universe we have found to be very careless, to say the least. But some people do word things in particular ways, in order to 'try to' make their own beliefs or assumptions of things fit together somehow.

Oh, and by the way, is 'cosmoses' an esoteric word that is used in your field, of study?
Astro Cat wrote: Sat Jul 02, 2022 2:35 am It's not correct that just halving the time elapsed would give you half of the size of the universe from that time: this is because different energy densities have dominated at different times (first radiation, then matter, and now finally dark energy very recently) and the universe expands differently during these epochs. For instance, when matter was the dominant energy density, the expansion of the universe was actually slowing down.
So, only 'that expansion', which you could observe, was, supposedly, what was actually 'slowing down'.

But let us not forget that what is, or was, actually being 'observed' may not be what is, nor was, actually happening and occurring. This is because of the misinterpretation of 'observed data' equation, which comes into play. This is also not taking into account APE thinking, which also comes into play here.
Astro Cat wrote: Sat Jul 02, 2022 2:35 am As soon as dark energy dominated, the expansion began to accelerate. Here's a plot from a talk I gave in 2020:

Image
This plot is only a part of, and so does not take into account all of.

This plot is only of what was observed, which let us not forget only what happened and occurred 'previously' and so is not necessarily what is happening and occurring 'now' at all.
Astro Cat wrote: Sat Jul 02, 2022 2:35 am We are using Type 1a supernovae to constrain how the scale factor has changed over time.
What for and why?
Astro Cat wrote: Sat Jul 02, 2022 2:35 am The different colored lines represent different cosmologies (some without dark energy, some with varying amounts of dark energy) -- basically any model that would look like the universe we see today with a=1. Well, since looking out is looking back, if we effectively measure the scale factor in the past at different redshifts it tells us what sort of history it's had (and thus what sort of future it has).
But the past does not always represent nor always predict the future.
Astro Cat wrote: Sat Jul 02, 2022 2:35 amAs you can see, the scale factor doesn't just double at a set rate, but evolves in a complex way.
Most things, when people do not yet understand them, are explained as 'complex' or evolve/behave in 'complex ways'.

To be very frank and Honest with you there is absolutely nothing here that is evolving in 'complex ways' at all.

As I can see from those lines that were plotted on a graph, which were made and/or used here, by you;

1. The scale of the Universe is shrunk down to 'try to' 'fit in with' only what is able to be observed at a particular time or moment. And,

2. What the rate of expansion was no one who had anything to do with that 'plot' has absolutely any idea.
Astro Cat wrote: Sat Jul 02, 2022 2:35 am
Age wrote: This, what you call, 'looking out to redshift', I have already partly talked about and explained in this forum is just looking back, 'temporally'.

I have also partly explained how the looking at redshift then gets misinterpreted as the whole Universe is expanding, which effects the way the people with this misinterpretation then look at what is actually occuring. This misinterpretation was like when people would look at sun's movement and misinterpret this as "evidence" for a geocentric universe, which would then effect the way they look at, and thus see, what is actually occuring. That is; that it is not the Universe, Itself, that is expanding, but rather just a part of the Universe that is expanding.

How all of this happens and occurs can be shown, explained, or illustrated, for those that are interested.
I'm not sure what you're talking about. The universe is definitely expanding.
What are you talking about here?

You just said above 'the universe' is only; "the physical cosmos that we observe".[/i]

Are you not yet aware that there is MORE to only 'that' what you can observe?

Because 'the universe' is only a PART of, the MORE, then 'the universe' to you, in your narrowed and small looking field of 'astrophysics' would be 'expanding'. But, we are in a philosophy forum now and not some small fiels like 'physics' the word 'Universe' refers to some thing different.
Astro Cat wrote: Sat Jul 02, 2022 2:35 am We can see it plain as day, and furthermore, models based on this expansion have matched observation so closely in some cases that the error bars (the sigma) had to literally be multiplied 400x to even be seen on a graph. It's one of the greatest triumphs of prediction-to-outcome-of-experiment in the history of science.
Here we are SEEING 'confirmation bias' working in its prime.
Astro Cat wrote: Sat Jul 02, 2022 2:35 am That doesn't happen based on being as radically wrong about something as thinking the universe is expanding if it's not.
'Expansion' happens. This is NOT in dispute, and NEVER has been in dispute, as far as I am aware.
Astro Cat wrote: Sat Jul 02, 2022 2:35 am (I happen to already have such a plot uploaded, you'll note the error bars had to be inflated --> 400sigma)

Image
What is noted is 'confirmation bias' at work.

And what you have NOT noted and seem to MISS is that NOT EVERY one 'works' in the field that you do.

There are millions upon millions of 'plots', already uploaded, which I could put before you, but to express, "You'll note the such and such had to be such or such" is just another example of having an extremely narrowed and shallow or small view or perspective of things.
Astro Cat wrote: Sat Jul 02, 2022 2:35 am This plot is the measurement of the CMB blackbody temperature on the assumption of an expanding universe (temperature T has an inversely proportional relationship to the scale factor a).
WHY is there an assumption of an expanding universe firstly, to begin with?
Astro Cat wrote: Sat Jul 02, 2022 2:35 am
Age wrote:
Astro Cat wrote: Energy densities with a positive equation of state (w = 1/3) and scales by /a^4 is simply radiation.

Energy densitites with an equation of state w = 0 and scales by /a^3 is matter.
You answered and clarified somewhat what they 'are', but not what they 'do', which was what I was asking for, and thus looking for to be clarified.
I'm not sure what you mean about what they do. Most people are familiar with radiation and matter, it's usually dark energy that laypersons are fuzzy about what it does.
So-called "lay persons" are usually, supposedly, "fuzzy" because so-called "experts" are just NOT YET ABLE TO explain "themselves", properly and correctly. Once they do learn how to communicate better, with 'these people', then there would be far less 'lay people'.
Astro Cat wrote: Sat Jul 02, 2022 2:35 amWhat about radiation and matter are you wondering about?
You have said and stated:
Dark energy is the negative equation of state that does not scale with the scale factor of the universe, drives the acceleration of cosmic expansion.

I was wondering what you now say is 'radiation', which is said to be the positive equation of state that does not scale with the scale factor of the universe, and what it does?

In other words if the 'negative equation' 'dark energy' drives the acceleration of (cosmic) expansion, then what does the 'positive equation' 'radiation' drive or do?

If 'radiation' and thus the 'positive equation' do nothing, then just say so.

If 'radiation' and 'positive equation' do something, then just say what that is.

(As for what 'matter' does this is already known anyway, correct?)

Once you clarify this, then we can move onto other things.

By the way there is no need to add symbols, numbers, nor maths equations to any of your wording here. I am not seeking an attempt at proof for any assumption nor claim being made, through any of those methods.

I am just seeking clarification, through words, of and for some things that are written. Remember this is a philosophy forum and not some very esoteric and presumptive field like astrophysics. Plain old easy to recognize and understand wording will work quite sufficiently here. After all it is only the words that are not usually commonly used or that I do not understand, or that I use differently, which is what I am seeking clarification for here.

Furthermore, if you hit the quote button, instead of copying and pasting or writing our names, it makes it much easier to go back and research over what we had previously actually said and written.
Atla
Posts: 6607
Joined: Fri Dec 15, 2017 8:27 am

Re: Dark Energy, Dark Matter

Post by Atla »

Astro Cat wrote: Sat Jul 02, 2022 2:05 am
Atla wrote: Fri Jul 01, 2022 1:55 pm Right, so as I was wondering above, can a Milky-way sized or bigger galaxy with two or more supermassive black holes orbiting each other in the center, become quiescent? Or do they disturb the rest of the galaxy too much that would lead to increased star formation?
Yes, galaxies with binary supermassives can become quiescent, and it's probably more likely since stirring things up will turn them into an AGN.

One of the possible mechanisms of quenching is when an AGN starts firing plasma jets, it heats up gases too much to condense into star-forming densities.

Materials for star formation also come from filaments between galaxies (forming the cosmic "web" you might have seen), AGNs can be disruptive to infalling gas.
Bit off-topic but this one is one of my favourite pictures of galaxy jets, it's interesting how even in intergalactic space there can be forces that can bend them like that

Image
User avatar
Astro Cat
Posts: 460
Joined: Thu Jun 23, 2022 11:09 pm

Re: Dark Energy, Dark Matter

Post by Astro Cat »

Age wrote: Sat Jul 02, 2022 4:28 am There are many, many things that we are still trying to understand, but there is no need to keep informing us of this.
I'm not sure why you're taking issue with this. It's important to demarcate between things we observe and things we're still trying to understand. I will continue to use whichever language I feel is best to express subjects because you're not the only one reading. No hard feelings!
Age wrote: "Today's galaxies" is a very relative term. As the only galaxy that would exist within the 'today' realm' is the one that 'your team' is within. Every other galaxy 'your team' looks at and observes is really what was happening and occurring before, or in 'yesterday's realm' and term.
Sure, but this is nitpicky when we're talking about very small redshifts. In terms of cosmic time, they are current. This would be like complaining that you're not watching a football game in real time because the light took a non-zero time to reach your retina: technically true, but overly pedantic and not constructive.

There is a point where redshifts are far enough away not to be well-representative of today's universe, but very short redshifts "ain't it," as they say.
Age wrote: So, when you talk about 'the universe', you are really only looking at and talking about a part of the whole.

In other fields other than astrophysics when we use the 'Universe' word, or some use the 'universe' word, we refer to Everything, all-there-is, and totality instead.

This way we are not looking at just a narrowed and small picture of things, nor look from a very narrowed and small perspective neither.
Words in the English language often have multiple contexts. I think a reasonable person knows what a physicist is talking about when they mention the universe in a cosmological context.
Age wrote:Also, your definition explains a lot about why some people assume or believe that the Universe began and/or is expanding.

These people are only looking at a part of the whole only, and so not seeing what the actual Truth is. Well not yet anyway.

...

Oh, and by the way, is 'cosmoses' an esoteric word that is used in your field, of study?
I'm not sure what you're trying to say here. The universe -- the cosmos, if you prefer -- has a beginning at least to its current state and is definitely expanding. These are more than just assumptions, they have the weight of evidence.

I don't know if "cosmoses" is a common term in cosmo or not, but I've seen it. Sure.
Age wrote: So, only 'that expansion', which you could observe, was, supposedly, what was actually 'slowing down'.

But let us not forget that what is, or was, actually being 'observed' may not be what is, nor was, actually happening and occurring. This is because of the misinterpretation of 'observed data' equation, which comes into play. This is also not taking into account APE thinking, which also comes into play here.
I'm not sure what APE thinking is, nor am I sure what kind of point you're trying to make here. If you have questions about how we know the universe is expanding, I'd be happy to give details so you can draw the same conclusion yourself.
Age wrote: This plot is only a part of, and so does not take into account all of.

This plot is only of what was observed, which let us not forget only what happened and occurred 'previously' and so is not necessarily what is happening and occurring 'now' at all.
Understanding how the scale factor has changed in the past due to changing density parameters does make a prediction for the future.
Age wrote:
Astro Cat wrote: Sat Jul 02, 2022 2:35 am We are using Type 1a supernovae to constrain how the scale factor has changed over time.
What for and why?
Type 1a supernovae are good for measuring distances. We can correlate the distances to redshift and ultimately the scale factor. The "why" is because understanding how the scale factor evolved in the past tells us what kind of cosmology the universe has: what kinds of energy densities there are, which density parameters dominated and when.
Age wrote: But the past does not always represent nor always predict the future.
In the same sense that we can't know for certain the sun will appear to rise tomorrow, but that doesn't mean we just throw up our arms and say "welp, science is pointless." I don't understand the point of this objection.
Age wrote: Most things, when people do not yet understand them, are explained as 'complex' or evolve/behave in 'complex ways'.

To be very frank and Honest with you there is absolutely nothing here that is evolving in 'complex ways' at all.
I do understand how the scale factor evolves, and to be equally honest and frank with you, you don't. I'm starting to see why someone in another thread mentioned you among people that think they know everything. It is complex because there are three different density parameters that scale differently over time, it isn't a simple curve.
Age wrote:As I can see from those lines that were plotted on a graph, which were made and/or used here, by you;

1. The scale of the Universe is shrunk down to 'try to' 'fit in with' only what is able to be observed at a particular time or moment. And,

2. What the rate of expansion was no one who had anything to do with that 'plot' has absolutely any idea.
Here I think you just don't know what you're talking about again. The scale factor is defined as 1 for the present, this is the vertical line on the plot that all lines pass through (as they must, if they would produce a universe that looks like the one we see today). I'm not sure what you're talking about shrinking down.

As for your second point that just amounts to saying "this plot is wrong, because I say so," I reiterate that you just don't know what you're talking about.

If you want to have a serious conversation and you'd like to know how we arrive to conclusions about how the scale factor changes, I'd be happy to have it. But this sort of baseless, smug denial isn't something that really interests me in suffering through.
Age wrote:WHY is there an assumption of an expanding universe firstly, to begin with?
Because we observe redshift in every galaxy that overpowers the peculiar motion (Doppler effect) out to a certain redshift, generally past the Virgo cluster. Since cosmological redshifting dominates peculiar redshifting/Doppler redshifting, the only viable explanation is an expansion. I would post some helpful plots, but you asked me not to do that (I will if someone asks, though).
Age wrote: I was wondering what you now say is 'radiation', which is said to be the positive equation of state that does not scale with the scale factor of the universe, and what it does?

In other words if the 'negative equation' 'dark energy' drives the acceleration of (cosmic) expansion, then what does the 'positive equation' 'radiation' drive or do?

If 'radiation' and thus the 'positive equation' do nothing, then just say so.

If 'radiation' and 'positive equation' do something, then just say what that is.

(As for what 'matter' does this is already known anyway, correct?)

Once you clarify this, then we can move onto other things.
Quick correction on what might be a typo in your response. Radiation does scale with the scale factor, so does matter. Dark energy is the only energy density that doesn't scale.

I still don't know what you mean by asking what it does. I suppose a relevant thing to say is that radiation and matter energy densities work against the expansion; they would slow and eventually reverse the expansion on their own.
Age wrote: Furthermore, if you hit the quote button, instead of copying and pasting or writing our names, it makes it much easier to go back and research over what we had previously actually said and written.
The first quote in my responses always have the little arrow thing, I find it's faster just to type things out after that rather than going and copy/pasting that whole thing.
Dubious
Posts: 3987
Joined: Tue May 19, 2015 7:40 am

Re: Dark Energy, Dark Matter

Post by Dubious »

There is likely only one Cosmos which contains a multiverse where eternal inflation lives up to its name; each "bubble" within the Cosmos grounded in its own local laws. In effect, Cosmos describes the superset of universes.
Age
Posts: 20043
Joined: Sun Aug 05, 2018 8:17 am

Re: Dark Energy, Dark Matter

Post by Age »

Astro Cat wrote: Sat Jul 02, 2022 5:59 am
Age wrote: Sat Jul 02, 2022 4:28 am There are many, many things that we are still trying to understand, but there is no need to keep informing us of this.
I'm not sure why you're taking issue with this.
Take issue ith 'what', exactly?

I am just informing you that, 'you are still trying to understand things', you do not need to inform us of. We know, and already knew, that you are still trying to understand many, many things.
Astro Cat wrote: Sat Jul 02, 2022 5:59 am It's important to demarcate between things we observe and things we're still trying to understand.
Are you not yet aware that what you observe, and think or believe you understand, is truly not necessarily the case at all?
Astro Cat wrote: Sat Jul 02, 2022 5:59 am I will continue to use whichever language I feel is best to express subjects because you're not the only one reading. No hard feelings!
And I will continue to inform others of things that they do not need to continually do. Like, for example, keep informing us that there are still things that they are trying to understand.
Astro Cat wrote: Sat Jul 02, 2022 5:59 am
Age wrote: "Today's galaxies" is a very relative term. As the only galaxy that would exist within the 'today' realm' is the one that 'your team' is within. Every other galaxy 'your team' looks at and observes is really what was happening and occurring before, or in 'yesterday's realm' and term.
Sure, but this is nitpicky when we're talking about very small redshifts.
And, not being so-called 'nitpicky' is WHY there are still so many things, which you are trying to understand.

Once one gets down to the nitty-gritty, then this is WHERE understanding is found.
Astro Cat wrote: Sat Jul 02, 2022 5:59 am In terms of cosmic time, they are current.
If you say and believe so.

In terms of so-called 'cosmic time', that the Universe began 10,000 years ago, is still very 'current' also, to SOME people.

It is ALL very relative.
Astro Cat wrote: Sat Jul 02, 2022 5:59 am This would be like complaining that you're not watching a football game in real time because the light took a non-zero time to reach your retina: technically true, but overly pedantic and not constructive.
But considering the Fact that absolutely NO one WAS complaining here, your now complaining is just attempting to over-shadow what is actually and irrefutably true.

It could also be argued and pointed out that you calling what is 'irrefutably true', 'technically true' is just you being 'nitpicky' and/or overly pedantic and not constructive, at all, also.

If some thing IS True, then it does not matter whether 'it' is technically or not technically true.

If it is True, then it is IRREFUTABLE, and a part of what is sometimes sort out in and through philosophical discussion.

And, philosophical discussion is what this forum was set up for, one could imagine.

Also, watching a 'football game' take place, when what 'took place' as already been SEEN, and the 'end score' is already been KNOWN, some might infer is unnecessary.

Astro Cat wrote: Sat Jul 02, 2022 5:59 am There is a point where redshifts are far enough away not to be well-representative of today's universe, but very short redshifts "ain't it," as they say.
Age wrote: So, when you talk about 'the universe', you are really only looking at and talking about a part of the whole.

In other fields other than astrophysics when we use the 'Universe' word, or some use the 'universe' word, we refer to Everything, all-there-is, and totality instead.

This way we are not looking at just a narrowed and small picture of things, nor look from a very narrowed and small perspective neither.
Words in the English language often have multiple contexts. I think a reasonable person knows what a physicist is talking about when they mention the universe in a cosmological context.
Does EVERY know that 'you' class 'yourself" as a "physicist"?

Also, is there another way to mention the Universe not in a cosmological context?

If yes, then how exactly?
Astro Cat wrote: Sat Jul 02, 2022 5:59 am
Age wrote:Also, your definition explains a lot about why some people assume or believe that the Universe began and/or is expanding.

These people are only looking at a part of the whole only, and so not seeing what the actual Truth is. Well not yet anyway.

...

Oh, and by the way, is 'cosmoses' an esoteric word that is used in your field, of study?
I'm not sure what you're trying to say here. The universe -- the cosmos, if you prefer -- has a beginning at least to its current state and is definitely expanding.
Here we have another example of the views of the 'religious'. That is, they BELIEVE that what they 'observe' and think or assume is true, is ACTUALLY, IRREFUTABLY TRUE.

Just like those other BELIEVERS who BELIEVED that the sun REALLY did revolve around the earth.

What do you propose the Universe from or of, exactly?

And, I would ENJOY having a discussion about WHETHER the Universe, Itself, is expanding or not. But, sadly you ALREADY KNOW what is DEFINITELY and thus IRREFUTABLY TRUE, and so are NOT OPEN to ANY thing else here.

Also, how MANY 'states' do you envision the Universe has had, and will have?

ANY 'state' could be narrowed down in an attempt to "prove" one's claims are true.
Astro Cat wrote: Sat Jul 02, 2022 5:59 am These are more than just assumptions, they have the weight of evidence.
The suns movement in the sky WAS also said and claimed to 'evidence' that the sun revolves around the earth.

'evidence' NEVER outweighs 'proof'.

There is NO ACTUAL 'proof' that the Universe BEGAN, nor IS EXPANDING.

There is, however, 'proof' for the opposite. But, AGAIN, sadly most people here BELIEVE what DEFINETELY happens and occurred.
Astro Cat wrote: Sat Jul 02, 2022 5:59 am I don't know if "cosmoses" is a common term in cosmo or not, but I've seen it. Sure.
I questioned whether the word 'cosmoses' was a word used in your field, of study.

You say you have seen that word before. Do you know what is means or refers to, exactly?

If yes, then will you explain for us here?
Astro Cat wrote: Sat Jul 02, 2022 5:59 am
Age wrote: So, only 'that expansion', which you could observe, was, supposedly, what was actually 'slowing down'.

But let us not forget that what is, or was, actually being 'observed' may not be what is, nor was, actually happening and occurring. This is because of the misinterpretation of 'observed data' equation, which comes into play. This is also not taking into account APE thinking, which also comes into play here.
I'm not sure what APE thinking is, nor am I sure what kind of point you're trying to make here.
Here we have another example of WHY people took so long to LEARN and DISCOVER, back in those days when this was being written.

Absolutely NO 'curiosity' AT ALL, as seen, was existing.
Astro Cat wrote: Sat Jul 02, 2022 5:59 am If you have questions about how we know the universe is expanding, I'd be happy to give details so you can draw the same conclusion yourself.
I have MANY questions. First one;

How do you, SUPPOSEDLY, 'know' the Universe, Itself, is expanding. (This is NOT forgetting that this is a philosophy forum, and not some astrophysics forum, so we can use the Universe word in the far more 'bigger' definition and usage here, rather than tiny, little and narrowed definition used in astophyisics.)

In other words, how do you KNOW that the area of all-there-is, totality, or Everything is expanding?

OBVIOUSLY, expansion exists. No one disputes this. So, how we KNOW expansion exists is just obvious anyway. But the claim the Everything, all-there-is, or totality is expanding is a huge claim.

But if you want to still continue to claim that the 'Universe', Itself, that is; Everything, all-there-is, or totality is expanding, or even began, then please let us in on how 'you', and maybe some "others", supposedly KNOW this.

I would love to see those 'details'.
Astro Cat wrote: Sat Jul 02, 2022 5:59 am
Age wrote: This plot is only a part of, and so does not take into account all of.

This plot is only of what was observed, which let us not forget only what happened and occurred 'previously' and so is not necessarily what is happening and occurring 'now' at all.
Understanding how the scale factor has changed in the past due to changing density parameters does make a prediction for the future.
Age wrote:
Astro Cat wrote: Sat Jul 02, 2022 2:35 am We are using Type 1a supernovae to constrain how the scale factor has changed over time.
What for and why?
Type 1a supernovae are good for measuring distances. We can correlate the distances to redshift and ultimately the scale factor. The "why" is because understanding how the scale factor evolved in the past tells us what kind of cosmology the universe has: what kinds of energy densities there are, which density parameters dominated and when.
Correct me if I am wrong here, but you said;
"different energy densities have dominated at different times (first radiation, then matter, and now finally dark energy very recently) and the universe expands differently during these epochs." Does this mean that 'dark energy' came much later after the 'big bang', than 'matter' and 'radiation' did?

And if so, then how does this correlate with the claims that expansion was much greater immediately after the 'big bang'?

You have stated after all that;
"when matter was the dominant energy density, the expansion of the universe was actually slowing down. As soon as dark energy dominated, the expansion began to accelerate."

Also, would it be possible to just remove the 'universe' word, so this does NOT interfere with what we are actually talking about and looking at here?

If we want to look at and talk about 'expansion', itself, then that is one thing. And, looking at and talking about whether the Universe, Itself, is expanding or not is another thing.
Astro Cat wrote: Sat Jul 02, 2022 5:59 am
Age wrote: But the past does not always represent nor always predict the future.
In the same sense that we can't know for certain the sun will appear to rise tomorrow, but that doesn't mean we just throw up our arms and say "welp, science is pointless." I don't understand the point of this objection.
1. There was and is NO 'objection'.

2. That you "saw" and "see" an 'objection' would explain your absurd and ridiculous remark, "but that doesn't mean we just throw up our arms and say "welp, science is pointless."

3. Where and why you JUMPED to that ASSUMPTION, you made here, was from NOTHING I wrote.

4. I was just pointing out and stating a Fact.

5. That I put a Fact, straight after a particular question, is no excuse to jump to an assumption nor claim, which was NEVER being made AT ALL anyway.

Astro Cat wrote: Sat Jul 02, 2022 5:59 am
Age wrote: Most things, when people do not yet understand them, are explained as 'complex' or evolve/behave in 'complex ways'.

To be very frank and Honest with you there is absolutely nothing here that is evolving in 'complex ways' at all.
I do understand how the scale factor evolves, and to be equally honest and frank with you, you don't.
OF COURSE NOT.

To be Honest and frank with you, again, this is the first time I have seen and talked about these terms. But this is probably VERY OBVIOUS to you. Especially considering the fact of the forum we are in and the questioning I am proposing to you here.

The reason WHY I am questioning 'you' is so that I can BETTER understand what 'it' is, which you claim here you do understand.

There are also LOT of things that you do NOT understand, but this is WHY I do NOT bring up those esoteric wording and understanding, in a forum like this one.

Now, if the 'scale factor' as you have already explained, and I have NOT misunderstood you, is just the name given to what one considers is the Universe is in Its current or present form or state, when the Universe is being observed, in relation to whether the Universe is, supposedly, expanding, shrinking, or neither, and which are, supposedly, caused by ''density energies', which is either 'dark energy', or 'negative equation', of the state that does not scale with the scale factor of the Universe, which, supposedly, expands the Universe, or the other two 'energy densities', which are 'radiation' and 'matter'.

Which, by the way, I am stil trying to work out what they do, if 'dark energy' 'energy density' supposedly drives the expansion of the Universe, but which supposedly only came about AFTER the other two 'energy densities', but which contradicts the claims made previously that expansion was greater nearer the 'big bang'.

And, this is without looking at and questioning your claims about how the so-called 'scale factor of the Universe' coincides with the 'present state of the Univese', which is OBVIOUSLY continuously CHANGING. As the present state of the Universe is in a CONSTANT 'state' of CHANGE.

So, what this actually means is, if one was looking at things, from a DIFFERENT 'present state', say in one of those other claimed states whent the Univese was said to be 'shrinking', then the 'scale factor of the Universe' THEN would be DIFFERENT, but would also be MADE TO BE defined as 1 ALSO.
Astro Cat wrote: Sat Jul 02, 2022 5:59 am I'm starting to see why someone in another thread mentioned you among people that think they know everything.
Did you also notice that that one who mentioned me among people that think they know everything was also one mentioned as one among people that think they know everything?
Astro Cat wrote: Sat Jul 02, 2022 5:59 am It is complex because there are three different density parameters that scale differently over time, it isn't a simple curve.
And, what would ALSO makes this SEEMINGLY 'more complex' is the Fact that the so-called and newly-called or named 'density parameters', which, supposedly, 'scale differently over time' could also NOT be DIFFERENT in relation to the Unverse, Itself,

Sure, the 'rate of expansion', of ANY individual so-called 'bang', would CHANGE or be DIFFERENT, at different times, but there is absolutely NO need to add other words here, which just very simple words would suffice.

Adding these newly formed words and terms, and mixing them in with the Universe word, only complicates things, and which makes things far more complex than they really need to be here.

Now, you say and claim that the;

'energy density' known as 'dark energy', is a so-called 'negative equation of state, but drives the 'acceleration of cosmic expansion'.

And, the 'energy density' also known simply as 'radiation', which is a 'positive equation of state' scales with the so-called 'scale factor of the Universe' and so to does the 'energy density' also known simply as 'matter', but which is neither a 'positive equation' nor a 'negative equation' 'of state' but is rather just 'an equation of state' also scales with the so-called 'scale factor of the Universe', correct?

If this is correct, then 'different density parameters, which scale differently over time' is not really that complex.

This is just part of the naturally, and really, very simple and easy way of how the constantly-ever-changing Universe actually works, or behaves.

Also, there is NEVER any so-called 'simple curves' in the 'vastly different density parameters, which scale differently over time', with EACH and EVERY different 'bang' or 'expansion'. But this is just ALL these 'curves' will be, naturally, and very simply, vastly different.
Astro Cat wrote: Sat Jul 02, 2022 5:59 am
Age wrote:As I can see from those lines that were plotted on a graph, which were made and/or used here, by you;

1. The scale of the Universe is shrunk down to 'try to' 'fit in with' only what is able to be observed at a particular time or moment. And,

2. What the rate of expansion was no one who had anything to do with that 'plot' has absolutely any idea.
Here I think you just don't know what you're talking about again. The scale factor is defined as 1 for the present,
Here I think you just do not, yet, know what I am talking about, and referring to, again. The present, is EVER CHANGING. Therefore, the 'scale factor' as defined by 'you' here, as 1, will also be ever changing. This is because the 'density energy' is ALWAYS CHANGING, and thus the EVER CHANGING 'present' 'scale factor' will also be constantly changing.
Astro Cat wrote: Sat Jul 02, 2022 5:59 am this is the vertical line on the plot that all lines pass through (as they must, if they would produce a universe that looks like the one we see today). I'm not sure what you're talking about shrinking down.
You claimed that the Universe you refer to is ONLY what you observe. OBVIOUSLY, there is MUCH MORE than just what 'you' and some "others" observe. Therefore, what 'you' and "them" are 'trying to' do is 'shrink down' the MORE to 'try to' fit the MORE into 'your' own little view of things.

Lines on a plot will NEVER match the Correct perspective nor view of the Universe, that is; the MORE that 'you' can see and observe.
Astro Cat wrote: Sat Jul 02, 2022 5:59 am As for your second point that just amounts to saying "this plot is wrong, because I say so," I reiterate that you just don't know what you're talking about.
Here we have, another, example of;

One SAYING, "You do NOT know what you are talking about, whereas I do. I say, 'you are wrong', therefore I am right, and this is because I KNOW what I am talking about".

Look, I am just going by the actual words written on that plot. Those words are;
After inflation, the expansion EITHER; first decelerated, then accelerated OR always accelerated. Which amounts to saying; "We have absolutely NO idea as to what 'the rate of expansion' was." This can be transferred over to the 'future' section of that plot. The opposing words of what could take place, also reiterates that the ones who had anything to do with that 'plot' has absolutely NO idea of what the 'rate of expansion' WAS nor WILL BE.
As I was saying; What the rate of expansion was, no one who had anything to do with that 'plot' has absolutely any idea.

Another way of saying or showing this is through the answer, or non answer, given to the clarifying question, What is the AGREED UPON 'rate of expansion' after what is called 'inflation' did expansion 'first decelarate, then accelerate', or, 'always accelerate'?
Astro Cat wrote: Sat Jul 02, 2022 5:59 am If you want to have a serious conversation and you'd like to know how we arrive to conclusions about how the scale factor changes, I'd be happy to have it. But this sort of baseless, smug denial isn't something that really interests me in suffering through.
If you want to have a serious conversation, with me, then STOP MAKING ASSUMPTIONS and JUMPING to FALSE and WRONG CONCLUSIONS.

The Fact that the 'scale factor' CHANGES, and is ALWAYS CHANGING, was ALREADY A KNOWN Fact.

How 'you' FINALLY arrived at this CONCLUSION, is NOT of ANY real interest to me.

What I am far more interested in is LEARNING how to communicate with a species of beings, which ACTUALLY BELIEVES that what it, individually and/or collectively, CURRENTLY BELIEVES is true, at ANY PRESENT MOMENT, is IRREFUTABLY TRUE. The Fact that they have been SO Wrong, SO OFTEN, one would HOPE would make them LESS "BELIEVERS", but SADLY this is NOT the case.

Now, AGAIN, if you want to INSIST that 'expansion' exists, and 'its' rate CHANGES over time, then this is and WAS just common knowledge, and ALREADY KNOWN. However, if you want INSIST, and/or PERSIST, that the Universe, Itself, is 'expanding' and/or 'began', then let us continue on with this conversation/discussion, which I would LOVE to SEE and KNOW how 'you' arrived at that conclusion.
Astro Cat wrote: Sat Jul 02, 2022 5:59 am
Age wrote:WHY is there an assumption of an expanding universe firstly, to begin with?
Because we observe redshift in every galaxy that overpowers the peculiar motion (Doppler effect) out to a certain redshift, generally past the Virgo cluster.
So what?

I have ALREADY partly explained, in this forum, (not that you would be expected to have read nor be yet aware of), that 'redshift' explains 'expansion'. But, redshift does NOT explain, NOR is 'evidence' for the Universe, Itself, expanding.

What you are saying here would also be like those ones claiming the sun does revolve around the earth because we observe the movement of the sun, revolving around the earth.

What NEEDS to be UNDERSTOOD here is that what is 'observed' is NOT always what ACTUALLY is happening and occurring, nor is ALWAYS what ACTUALLY happened and occurred.
Astro Cat wrote: Sat Jul 02, 2022 5:59 am Since cosmological redshifting dominates peculiar redshifting/Doppler redshifting, the only viable explanation is an expansion.
Which NO one here is DISPUTING, and especially NOT me.
Astro Cat wrote: Sat Jul 02, 2022 5:59 am I would post some helpful plots, but you asked me not to do that (I will if someone asks, though).
Are they 'helpful' in explaining or showing that the Universe is expanding, or that there is an expansion?

If it is the former, then I would LIKE to see them.
Astro Cat wrote: Sat Jul 02, 2022 5:59 am
Age wrote: I was wondering what you now say is 'radiation', which is said to be the positive equation of state that does not scale with the scale factor of the universe, and what it does?

In other words if the 'negative equation' 'dark energy' drives the acceleration of (cosmic) expansion, then what does the 'positive equation' 'radiation' drive or do?

If 'radiation' and thus the 'positive equation' do nothing, then just say so.

If 'radiation' and 'positive equation' do something, then just say what that is.

(As for what 'matter' does this is already known anyway, correct?)

Once you clarify this, then we can move onto other things.
Quick correction on what might be a typo in your response. Radiation does scale with the scale factor, so does matter. Dark energy is the only energy density that doesn't scale.
Okay, and that was NOT a 'typo', that was completely my MISTAKE. You had written:
Energy densities with a positive equation of state (w = 1/3) and scales by /a^4 is simply radiation.

Energy densitites with an equation of state w = 0 and scales by /a^3 is matter.


Which I ASSUMED, Wrongly, that because there was an 'energy density' "with an equation of state", that this would then mean that this one does 'scale with the scale factor of the Universe, while the 'positive' and 'negative' ones would not. Again, my MISTAKE, and my APOLOGIES for ASSUMING some thing. (This is just further PROOF of WHY I say ASSUMING is NEVER a good NOR right thing to do here.)

Astro Cat wrote: Sat Jul 02, 2022 5:59 am I still don't know what you mean by asking what it does.
I was, again, ASSUMING that if 'dark energy' 'energy density' drives acceleration of expansion, then the 'energy densities' of 'matter' and/or 'radiation' would be said to do/drive some thing as well. As I said, if they do not do any thing or do drive any thing at all, then just say so. But if they do/drive some thing, then just say that, as well.
Astro Cat wrote: Sat Jul 02, 2022 5:59 am I suppose a relevant thing to say is that radiation and matter energy densities work against the expansion; they would slow and eventually reverse the expansion on their own.
I just found where you had already answered my question. You wrote:
different energy densities have dominated at different times (first radiation, then matter, and now finally dark energy very recently) and the universe expands differently during these epochs. For instance, when matter was the dominant energy density, the expansion of the universe was actually slowing down. As soon as dark energy dominated, the expansion began to accelerate.

When was 'matter' the 'dominant energy density', exactly?

But if you do not know when, exactly, then roughly would suffice?

Also, how would 'radiation' and 'matter', supposedly, slow, and eventually reverse, 'expansion', on their own?

Furthermore, 'radiation' being, supposedly, first, would imply, according to your claim here, that the 'rate of expansion', if it was not reversed/contracting, "in the beginning", was much slower, which opposes what some others say and claim. And, when you say 'dark energy' only came about in a time 'very recently', when was this 'very recent' time, exactly, or roughly?
Astro Cat wrote: Sat Jul 02, 2022 5:59 am
Age wrote: Furthermore, if you hit the quote button, instead of copying and pasting or writing our names, it makes it much easier to go back and research over what we had previously actually said and written.
The first quote in my responses always have the little arrow thing, I find it's faster just to type things out after that rather than going and copy/pasting that whole thing.
You would only have to copy once, and just paste every other time, but if it is quicker for you to do this that way, then all good. At least you do have the little arrow thing in there at least once. Which is all that is really needed and a lot more than other posters will do.
Age
Posts: 20043
Joined: Sun Aug 05, 2018 8:17 am

Re: Dark Energy, Dark Matter

Post by Age »

Dubious wrote: Sat Jul 02, 2022 8:27 am There is likely only one Cosmos which contains a multiverse where eternal inflation lives up to its name; each "bubble" within the Cosmos grounded in its own local laws. In effect, Cosmos describes the superset of universes.
When you say, 'Cosmos', do you mean, or refer to, the Everything, to the all-there-is, and/or to the totality of things?

If yes, then, OBVIOUSLY, there could ONLY ever be One.

But, if no, then how are you defining the 'Cosmos' word here?

Why change what the word 'Universe' USED to mean, and refer to, and add another word for that 'thing', and then give the 'Universe' word another definition?

As for these so-called 'multiverses', which you speak of, talk about, and refer to here, what are they, EXACTLY?

WHY would any thing you say here imply that the so-called 'eternal inflation' would somehow live up to its name?

WHY would each so-called 'bubble' have its OWN 'local laws'?

WHAT, EXACTLY could and would be ABLE TO 'separate' these 'bublles' from each other?
User avatar
attofishpi
Posts: 9939
Joined: Tue Aug 16, 2011 8:10 am
Location: Orion Spur
Contact:

Re: Dark Energy, Dark Matter

Post by attofishpi »

Astro Cat wrote: Fri Jul 01, 2022 5:12 am I began a thread in The Lounge trying to get to know other members and I wanted that thread to stay on topic. So, I'm moving over some questions that appeared there to be discussed on their own. For background, I'm a researching astrophysics grad student (which is how these questions arose in the first place).
Hi Astro Cat, and welcome to the nuthouse of PHN forum.

I hope you stick around and don't let wackjobs like me put you off :D

I'd be interested on whether this video (10 mins) is particularly bad in any way in what you have already been attempting to cover with simple folk like me - don't worry if you cbf it.

If the universe is only 14 billion years old, how can it be 92 billion yearswide: https://youtu.be/vIJTwYOZrGU

I just thought it might help explain in simpler terms some of what your are addressing for us.

Dark energy/matter apparently makes up 95% of the mass-energy of the universe. Is it thought that this 'stuff' is fairly evenly distributed throughout the universe?
User avatar
Astro Cat
Posts: 460
Joined: Thu Jun 23, 2022 11:09 pm

Re: Dark Energy, Dark Matter

Post by Astro Cat »

Ok, I have tried to whittle this down to questions. A lot of this is based on semantics over the word "universe" which I don't find very interesting. We should expect that a physicist is talking about the material cosmos in which we live, such as the area within it that is the visible universe. Let it be understood that any time in this thread I talk about "the universe" I'm talking about the universe of physics, not the philosophical notion of "everything that exists, whether it is physical or not."
Age wrote: Sat Jul 02, 2022 9:28 am What do you propose the Universe from or of, exactly?
I'm going to infer that you're asking what I propose the universe came from. The only possible response is that nobody is sure what the answer to this question is or what a good way to ask the question might even look like. Data is limited during the Planck epoch and without a quantum theory of gravity the extremely early universe is difficult to parse.
Age wrote:Also, how MANY 'states' do you envision the Universe has had, and will have?
This is as difficult a question to answer as asking "how many states will a person have during their lifetime?" Well, what does the asker mean? There are an absurd number of possible responses depending on the level of granulation or detail the asker wants, and it is a question beyond reasonable scope in either case.

I could say something like "in terms of energy densities, there are and will be 5 states: radiation dominance, radiation-matter equivalence, matter dominance, matter-dark energy equivalence, and dark energy dominance," but I don't think that's very meaningful. I think the question is too vague.
Age wrote: Correct me if I am wrong here, but you said;
"different energy densities have dominated at different times (first radiation, then matter, and now finally dark energy very recently) and the universe expands differently during these epochs." Does this mean that 'dark energy' came much later after the 'big bang', than 'matter' and 'radiation' did?

And if so, then how does this correlate with the claims that expansion was much greater immediately after the 'big bang'?
No, dark energy was present at the same time; it just wasn't dominant.

Image

Here on the left we have how the energy densities scale (r for radiation, m for matter, lambda for dark energy. The rightmost term can be ignored as it deals with curvature). With redshift plotted against density parameters, we get a picture of which density parameters were dominant at different times in the universe.

On the x-axis, 0 is "now," that's here in cosmic time. The further left along the x-axis one looks, the further back in time they're looking. Not long ago, matter and dark energy were equally dominant energy densities (where the black and blue lines cross). Before that, matter alone was dominant. Before that, there was a time when radiation and matter were equally dominant (where the red and black lines cross), and before that, radiation comprised most of the universe's energy density (where the red line is the highest, over all other lines).
Age wrote:Look, I am just going by the actual words written on that plot. Those words are;
After inflation, the expansion EITHER; first decelerated, then accelerated OR always accelerated. Which amounts to saying; "We have absolutely NO idea as to what 'the rate of expansion' was." This can be transferred over to the 'future' section of that plot. The opposing words of what could take place, also reiterates that the ones who had anything to do with that 'plot' has absolutely NO idea of what the 'rate of expansion' WAS nor WILL BE.
As I was saying; What the rate of expansion was, no one who had anything to do with that 'plot' has absolutely any idea.
On that plot, it says "After inflation, the expansion either first decelerated or always accelerated," but it's talking about the different lines on the plot.

It's saying either the universe will fall along one of these green lines, or it will fall along one of these red lines.

Then the data is actually applied to the plot clearly showing that the data supports "first decelerated, then accelerated." It's not saying "we don't know," it's the opposite: it's showing "it's definitely this one."
Age wrote: When was 'matter' the 'dominant energy density', exactly?

But if you do not know when, exactly, then roughly would suffice?
Matter-dark energy equivalence would have happened at a=0.76, which is a redshift of 0.31, about 3.54 billion years ago by my calculations.
Age wrote:Also, how would 'radiation' and 'matter', supposedly, slow, and eventually reverse, 'expansion', on their own?

Furthermore, 'radiation' being, supposedly, first, would imply, according to your claim here, that the 'rate of expansion', if it was not reversed/contracting, "in the beginning", was much slower, which opposes what some others say and claim. And, when you say 'dark energy' only came about in a time 'very recently', when was this 'very recent' time, exactly, or roughly?
These energy densities are treated like pressures in a fluid, and in fact the equation we calculate the equation of state from is simply called "the fluid equation." Simplistically though, it's gravity that would cause contraction (just described as a pressure in a fluid).

As for dark energy being very recent, that's perhaps a misunderstanding of something I said: dark energy has always been there; it just gets more powerful the larger the universe gets.
uwot
Posts: 6093
Joined: Mon Jul 23, 2012 7:21 am

Re: Dark Energy, Dark Matter

Post by uwot »

Astro Cat wrote: Wed Jul 06, 2022 8:41 am...dark energy has always been there; it just gets more powerful the larger the universe gets.
Is there evidence that dark energy becomes more powerful, rather than just dominant?
My story about dark energy is to suppose the universe is made of something that has broadly mechanical/fluid qualities - big bang stuff, for want of a better name. Chief among those qualities is its capacity to expand, which for the sake of the narrative, I assume is ongoing. Fundamental particles are point sources of expanding big bang stuff that get twisted and tangled to make the visible universe, and the density of the big bang stuff they exude decreases in the usual inverse square way. That allows me to sneak in refraction as the cause of gravity. Anyway, at a distance I shall call x, the density becomes such that any refraction is too little to overcome the push of the exuding big bang stuff. As for dark matter, well, since individual stars are held together by gravity, the big bang stuff they exude is slowed by the big bang stuff of other stars, thereby increasing the density.
User avatar
bahman
Posts: 8791
Joined: Fri Aug 05, 2016 3:52 pm

Re: Dark Energy, Dark Matter

Post by bahman »

If the universe expands then the edge of observation moves with the speed of light which means that the matter on the edge moves with the speed of light. For this, you need to inject infinite energy at each instant! Where does this energy come from?
uwot
Posts: 6093
Joined: Mon Jul 23, 2012 7:21 am

Re: Dark Energy, Dark Matter

Post by uwot »

bahman wrote: Wed Jul 06, 2022 9:50 pm If the universe expands then the edge of observation moves with the speed of light which means that the matter on the edge moves with the speed of light. For this, you need to inject infinite energy at each instant! Where does this energy come from?
Dunno if you're asking me bahman, but if so, perhaps you could break it down.
Why does this:
bahman wrote: Wed Jul 06, 2022 9:50 pm...the edge of observation moves with the speed of light
follow from this?
bahman wrote: Wed Jul 06, 2022 9:50 pm...the universe expands
User avatar
Cerveny
Posts: 752
Joined: Thu Mar 11, 2010 9:35 pm
Location: Czech Republic
Contact:

Re: Dark Energy, Dark Matter

Post by Cerveny »

Funny enough, we don't know what physical space is, but we do know what a "black hole" is:)
viewtopic.php?p=488112#p488112
Age
Posts: 20043
Joined: Sun Aug 05, 2018 8:17 am

Re: Dark Energy, Dark Matter

Post by Age »

Astro Cat wrote: Wed Jul 06, 2022 8:41 am Ok, I have tried to whittle this down to questions. A lot of this is based on semantics over the word "universe" which I don't find very interesting.
And that you do not 'this' find very interesting, others do not find at all interesting.

But what can be clearly seen is that it is the way words are defined, differently, which is what is causing most of the miscommunication, and thus most of the confusion, among human beings.
Astro Cat wrote: Wed Jul 06, 2022 8:41 am We should expect that a physicist is talking about the material cosmos in which we live, such as the area within it that is the visible universe.
There are so many things to look at and unpack here. That is; if one wants to get down to what is irrefutably True, Right, and Correct, but because you do NOT find that understanding the actual definitions of the words being used in discussions 'very interesting' AT ALL, then there is NO use at looking into this ANY further.

Except maybe the fact that to a so-called "physicist" there is absolutely nothing more that the so-called 'material cosmos' anyway.

Also, we will note that the 'visible universe' is only a fraction of the whole, Universe.
Astro Cat wrote: Wed Jul 06, 2022 8:41 am Let it be understood that any time in this thread I talk about "the universe" I'm talking about the universe of physics, not the philosophical notion of "everything that exists, whether it is physical or not."
So, when you talk about 'the universe' you are literally NOT talking about those parts of the 'physical universe' that you can NOT observe, but which obviously still do exist, physically or not.

Let it also be understood, that ANY time you talk about 'the universe', in this thread, you are NOT talking about the WHOLE Universe and so are only talking about a fraction, or just parts, of the Universe.
Astro Cat wrote: Wed Jul 06, 2022 8:41 am
Age wrote: Sat Jul 02, 2022 9:28 am What do you propose the Universe from or of, exactly?
I'm going to infer that you're asking what I propose the universe came from.
Yes, correct. My mistake sorry.
Astro Cat wrote: Wed Jul 06, 2022 8:41 am The only possible response is that nobody is sure what the answer to this question is or what a good way to ask the question might even look like.
There is also the other possibility that the Universe never 'came from' ANY thing. That is; in the sense of SOME thing outside of the Universe, Itself.
Astro Cat wrote: Wed Jul 06, 2022 8:41 am Data is limited during the Planck epoch and without a quantum theory of gravity the extremely early universe is difficult to parse.
ONCE AGAIN, we have ANOTHER example of this UNDERLYING BELIEF or ASSUMPTION within these human beings, that the Universe, Itself, 'came' or 'began', 'from' some OTHER thing.

Once these human beings got RID OF this ASSUMPTION or BELIEF, then they COULD LOOK AT and SEE the ACTUAL 'data' far more correctly and accurately, and then that is when they began to find and see what the IRREFUTABLE Truth is, EXACTLY.

Until then they REMAINED making these Wrong INTERPRETATIONS.
Astro Cat wrote: Wed Jul 06, 2022 8:41 am
Age wrote:Also, how MANY 'states' do you envision the Universe has had, and will have?
This is as difficult a question to answer as asking "how many states will a person have during their lifetime?" Well, what does the asker mean? There are an absurd number of possible responses depending on the level of granulation or detail the asker wants, and it is a question beyond reasonable scope in either case.
EXACTLY.

And also because of the Fact that the Universe, Itself, has, is, and always will be in just the One constant-state, of CHANGE.
Astro Cat wrote: Wed Jul 06, 2022 8:41 am I could say something like "in terms of energy densities, there are and will be 5 states: radiation dominance, radiation-matter equivalence, matter dominance, matter-dark energy equivalence, and dark energy dominance," but I don't think that's very meaningful. I think the question is too vague.
It could also be said here that your answer is very vague. Especially considering the fact that so-called "physicists" used to say and claim differently, from what you do now, which could infer that "physicists", in the future, will say and claim things differently, AGAIN.
Astro Cat wrote: Wed Jul 06, 2022 8:41 am
Age wrote: Correct me if I am wrong here, but you said;
"different energy densities have dominated at different times (first radiation, then matter, and now finally dark energy very recently) and the universe expands differently during these epochs." Does this mean that 'dark energy' came much later after the 'big bang', than 'matter' and 'radiation' did?

And if so, then how does this correlate with the claims that expansion was much greater immediately after the 'big bang'?
No, dark energy was present at the same time; it just wasn't dominant.
So, this would mean that immediately after the 'big bang' there was NO expansion AT ALL, and so either there was contraction, or 'stability', or expansion was much slower closer to the 'big bang' than it is say 13 or so biilions of years after the 'big bang'.
Astro Cat wrote: Wed Jul 06, 2022 8:41 am Image

Here on the left we have how the energy densities scale (r for radiation, m for matter, lambda for dark energy. The rightmost term can be ignored as it deals with curvature). With redshift plotted against density parameters, we get a picture of which density parameters were dominant at different times in the universe.
And let us NOT FORGET that 'that' is ONLY in relation to just a fraction of the Universe, and NOT in relation to the WHOLE Universe, from which a WHOLE DIFFERENT picture and equation emerges.
Astro Cat wrote: Wed Jul 06, 2022 8:41 am On the x-axis, 0 is "now," that's here in cosmic time.
What does the term 'cosmic time' even actually refer to, exactly?

The further left along the x-axis one looks, the further back in time they're looking. Not long ago, matter and dark energy were equally dominant energy densities (where the black and blue lines cross). Before that, matter alone was dominant. Before that, there was a time when radiation and matter were equally dominant (where the red and black lines cross), and before that, radiation comprised most of the universe's energy density (where the red line is the highest, over all other lines).[/quote]

Is this an IRREFUTABLE Fact, or just what some so-called "physicist" ASSUME is true?

Also, just about ANY one can draw lines on a graph, add some very esoteric symbols, figures, or numbers, and then CLAIM that this then is the 'data', which 'tells us' what actually took place.
Astro Cat wrote: Wed Jul 06, 2022 8:41 am
Age wrote:Look, I am just going by the actual words written on that plot. Those words are;
After inflation, the expansion EITHER; first decelerated, then accelerated OR always accelerated. Which amounts to saying; "We have absolutely NO idea as to what 'the rate of expansion' was." This can be transferred over to the 'future' section of that plot. The opposing words of what could take place, also reiterates that the ones who had anything to do with that 'plot' has absolutely NO idea of what the 'rate of expansion' WAS nor WILL BE.
As I was saying; What the rate of expansion was, no one who had anything to do with that 'plot' has absolutely any idea.
On that plot, it says "After inflation, the expansion either first decelerated or always accelerated," but it's talking about the different lines on the plot.
That is; those lines, which were put there by human beings.

And they are NOT lines that correlate with what ACTUALLY TOOK PLACE. Unless, OF COURSE, you want to state and claim otherwise.
Astro Cat wrote: Wed Jul 06, 2022 8:41 am It's saying either the universe will fall along one of these green lines, or it will fall along one of these red lines.

Then the data is actually applied to the plot clearly showing that the data supports "first decelerated, then accelerated." It's not saying "we don't know," it's the opposite: it's showing "it's definitely this one."
LOL So, it is a DEFINITE, and thus IRREFUTABLE, Fact that 'expansion' decelerated, and then accelerated.

What could the ACTUAL 'thing' be that makes expansion accelerate? In other words what could that 'energy density' be composed of EXACTLY? If the other two so-called 'energy densities' are composed of either 'radiation' or 'matter', then what is this third 'energy density' made up of, EXACTLY?
Astro Cat wrote: Wed Jul 06, 2022 8:41 am
Age wrote: When was 'matter' the 'dominant energy density', exactly?

But if you do not know when, exactly, then roughly would suffice?
Matter-dark energy equivalence would have happened at a=0.76, which is a redshift of 0.31, about 3.54 billion years ago by my calculations.
So what was the so-called 'dominant' 'energy force' or 'energy density' before this period?
Astro Cat wrote: Wed Jul 06, 2022 8:41 am
Age wrote:Also, how would 'radiation' and 'matter', supposedly, slow, and eventually reverse, 'expansion', on their own?

Furthermore, 'radiation' being, supposedly, first, would imply, according to your claim here, that the 'rate of expansion', if it was not reversed/contracting, "in the beginning", was much slower, which opposes what some others say and claim. And, when you say 'dark energy' only came about in a time 'very recently', when was this 'very recent' time, exactly, or roughly?
These energy densities are treated like pressures in a fluid, and in fact the equation we calculate the equation of state from is simply called "the fluid equation." Simplistically though, it's gravity that would cause contraction (just described as a pressure in a fluid).
So, once again, HOW would 'radiation' and 'matter', supposedly, slow, and/or eventually reverse, 'expansion', on their own. Saying, "it is gravity that would cause contraction", is NOT explaining how 'radiation' NOR 'matter', themselves cause contraction.

That 'you', so-called "physicists", call the reverse of 'expansion', 'contraction', is just obvious. And, by the way, HOW 'matter' causes what is referred to as 'contraction' is also obvious as well as very easy and simple to understand and know. We, though, just wait for your explanation.
Astro Cat wrote: Wed Jul 06, 2022 8:41 am As for dark energy being very recent, that's perhaps a misunderstanding of something I said: dark energy has always been there; it just gets more powerful the larger the universe gets.
But this just sounds like very weak 'reasoning' to just say and explain that the 'observable universe' is expanding 'more', 'now' in relative terms.

Claiming that 'it' has always been here, but 'it' has only 'recently' become dominant, and that 'it' is a so-called 'energy density', when, and if, LOOKED INTO FULLY will EXPOSE what the ACTUAL Truth IS here.

That is; these people have ATTEMPTED to FIND some 'thing', which they could use to 'try to' "justify" what they currently and already ASSUME or BELIEVE is true. That being; the Universe BEGAN, and IS EXPANDING. Which the ABSURDITY and RIDICULOUSNESS of, will soon be REVEALED.
Post Reply