Age of Universe: Seeing More than 13.5 Billion Yrs

[BoomBoom]

I've heard stated by experts that the approximate age of our universe is about 13.5 billion years of so. The thing that doesn't make sense to me about this is that we can see more time than this. The famous Hubble deep field shot taken in the northern hemisphere shows about 13 billion years or so into the past and the other deep field Hubble shot to the south is about 12 billion years. Add them together and we can see more than 25 billion years of our universe's history and it seems to have looked quite similar to what we see in the more recent universe.

Am I missing some fundamental fact here?

 

[Garth]

Am I missing some fundamental fact here?

Yes. The fact that light itself is carried along with the expansion of space.

Therefore we can see objects that are moving away from us at speeds greater than c and as a consequence we can see objects further away in light years than the age of the universe is in years.

Also, the fact that we can look in two opposite directions and yet see these ancient objects in both directions is irrelevant.

The ancient high z universe is different from the recent low z one.

However, there are interesting high iron abundance objects that appear to be too old for the young universe they inhabit, this leads to the question Is there an Age Problem in the Mainstream Model?.

Garth

 

[russ_watters]

If two people walk away from you for 5 minutes apiece in opposite directions, does that make them 10 minutes apart...?

 

[marcus]

I've heard stated by experts that the approximate age of our universe is about 13.5 billion years of so. The thing that doesn't make sense to me about this is that we can see more time than this. The famous Hubble deep field shot taken in the northern hemisphere shows about 13 billion years or so into the past and the other deep field Hubble shot to the south is about 12 billion years. Add them together and we can see more than 25 billion years of our universe's history and it seems to have looked quite similar to what we see in the more recent universe.

Am I missing some fundamental fact here?

the stuff that made the CMB, cosmic microwave background radiation, is currently at an estimated distance of 45 billion LY.

the farthest we can theoretically "see" at the present moment is about 46.5 billion LY. that is how far stuff could be from us and we would be getting radiation emitted from it today.

the farthest back in time we can see is 13-14 billion years.
that is, the oldest light we can see is about 13 billion years old, it was emitted by stuff 13 billion years ago.

when we get instruments that can detect bigbounce neutrinos (or "bigbang" neutrinos if you like bang better than bounce ) then we will still be only looking back 13-some billion years.

the neutrinos will be, say, 13.6 billion years old, and the crud that emitted them will be about 46.5 billion lightyears away at present, and they will have been traveling towards us for 13.6 billion years.

Garth's post explained away the apparent paradox. Look back at what he said.

The expansion of space is different from a rocket ship. Recession speeds are not limited by the speed of light.

 

[Wallace]

This is why astronomers, contrary to popular belief, do not actually use 'light year' as a measure of distance. In fact distance is a surprisingly slippery concept in general relativity and cosmology, there are several active threads around the place here discussing some of the issues with defining distance that you may want to look at (I'm talking to the OP here, I think the rest of the posters are the ones doing the discussion in the other threads I'm referring to!).

 

[PRDan4th]

If what we see at 45 billion LYs away was emitted 13 billion years ago, then the actual object is much further away today, if it still exists. This would make the universe much larger than 90 billion LYs across. If the universe expansion rate is the same as it has averaged over the past 13 billion years the universe would have a diameter of roughly (45/13)*90 billion LYs or 300 billion LYs. I understand that the expansion rate is increasing making the size even larger. Is this logic correct?

 

[BoomBoom]

The whole concept of expansion of space seems confusing. Space by definition is nothing is it not? How does "nothing" expand and what would be beyond this definable "nothingness"?

Are there any models out there that suggest a more infinite universe as applied to it's age and perhaps even size?

 

[BoomBoom]

If two people walk away from you for 5 minutes apiece in opposite directions, does that make them 10 minutes apart...?

In reference to the speed of walking, yes they are.

 

[marcus]

The whole concept of expansion of space seems confusing. Space by definition is nothing is it not? How does "nothing" expand and what would be beyond this definable "nothingness"?

you haven't got the concept. You just have some words. the words ARE confusing.

the concept, when properly defined using geometry, is NOT confusing.

the basic element you are missing is the METRIC
just a technical name for the DISTANCE FUNCTION that keeps track of all the distances between events.

If you think about it, you'll see that there has to be a distance function to catalog the distances between things that happen. Its basically simple: there are distances between welldefined events. what they call the metric keeps track of them.

the metric is what is governed by the 1915 law of gravity called GR, that replaced Newton's 1680 force model.

the metric is what "expands", in the obvious sense that on average largescale distances in the catalog are forced to get larger by the 1915 law of gravity which governs the metric.

that is not the only way it could work out but it characterizes a large class of solutions----there are also contracting solutions where largescale distances get smaller by a certain percentage step by step.
==================

when you say "space is nothing and how can nothing expand, so how can space expand?" you miss the point. I am not talking about "nothing". I am talking about the METRIC----the distance function---that defines our geometry. It is not a material---an expanding material analogy doesn't work. So what should I say?
"The distance function enlarges itself"
"the distances in the catalog increase bit by bit percentagewise."
That's awkward to say. so how about "The metric expands."

Does that work for you, BoomBoom?

 

[BoomBoom]

"The distance function enlarges itself"
"the distances in the catalog increase bit by bit percentagewise."
That's awkward to say. so how about "The metric expands."

Are these distances from us or from each other or both? Are things closer together the further back in time we look? Or is the metric calculated based on the prediction of where things should be in the present considering speed and direction of movement of where they were when the light left them?

Please pardon my ignorance in these matters, I am trying to wrap my mind around the concept of inflation of space-time. It seems as if the universe expansion (space-time if you want to call it that) was supposed to be at a rate not possible to account for the "history" we see today.

 

[marcus]

Are these distances from us or from each other or both?

both

Are things closer together the further back in time we look?

yes

Or is the metric calculated based on the prediction of where things should be in the present considering speed and direction of movement of where they were when the light left them?

not sure I understand the question. the metric is a SOLUTION of the law of gravity with two or three parameters plugged in. the law of gravity (einstein's GR equation) is a differential equation governing how metrics evolve. you find out the correct values of the parameters by adjusting them so as to get the best fit to the data

It seems as if the universe expansion (space-time if you want to call it that) was supposed to be at a rate not possible to account for the "history" we see today.

Why does it seem that way? I don't understand.

Be sure you don't confuse expansion with inflation.
Routine expansion of the universe is a familiar feature which has been understood since 1930 (or earlier by some) and fits the observations in a beautifully consistent way. Also our law of gravity forces it on us---solutions of the basic gravity equation typically have expanding or contracting distances.

It is as if the universe is trying to teach us to realize that it is not in the nature of distances between things to remain constant (unless bound together by atomic molecular or some other force)

But inflation is something else---it refers to a scenario which might have occurred in the first fraction of a second of expansion where there was a different mechanism in control, that goes beyond ordinary matter and the law of gravity we can see working and test experimentally. Inflation could well be fantasy. Although a lot of experts favor the notion. We don't have proof of it, only plausibility.

Inflation is a conjectured (fantasized) feature of the first fraction of a second.
Expansion has been a familiar part of our worldview since 1930s and checks nicely with huge numbers observations made over the years.

 

[BoomBoom]

Be sure you don't confuse expansion with inflation.

That is precisely what I did. Thanks for catching that one.
I was actually referring to inflation in which the size of the universe expanded at an "impossible" rate.


...and thanks for your answers Marcus, I have a much better idea now of what they are actually measuring.

 

[marcus]

That is precisely what I did. Thanks for catching that one.
I was actually referring to inflation in which the size of the universe expanded at an "impossible" rate....and thanks for your answers Marcus, I have a much better idea now of what they are actually measuring.

You are welcome! I didn't actually see a case where you were confusing ordinary expansion with inflation, BoomBoom. I only meant to warn against getting the two confused. (there was no implied criticism.)
I still don't fully understand some of what you are saying about "impossible" rates of expansion.

Ordinary expansion of the sort that has been going on for most of the age of the universe does involve superluminary recession speeds, so it boggles some people and they think of it as impossible.

but I think you understand how there can be superluminary recession speeds (ask about it if you don't) and you see that aspect of ordinary expansion is not "impossible"

I won't try to secondguess and speculate as to what you find strains credulity.

 

[russ_watters]

In reference to the speed of walking, yes they are.

I worded that badly, or perhaps didn't finish the thought: does the fact that they are now 10 "walking-minutes" apart mean that they have been walking for 10 minutes? No - the elapsed time is still only 5 minutes. That's exactly like the HDF and UDF only showing ~14 billion years of age even though the depth of the two images added together would be 14+14=28 billion light years. In both cases, we're in the middle, so the distance traveled is half the total distance between the two.

I think everyone else added complexities to this about inflation that aren't really necessary for explaining the initial question.

 

[BoomBoom]

In both cases, we're in the middle, so the distance traveled is half the total distance between the two.

Would that not require the assumption that we are sitting on ground zero of the BB?

 

[marcus]

Would that not require the assumption that we are sitting on ground zero of the BB?

There you go again, BoomBoom, with your obsession about ground zero, or the "center point" of expansion.

You've got to purge your head of that.

Have you ever thought about the Balloon Analogy[/color]?

You must have encountered it many times in previous discussion boards and elsewhere.

As a purely geometrical analogy, it is very good. Just don't take the rubber material the balloon is made of as part of the analogy.

The geometrical analogy is simply that at least IN SPACE WHERE WE ARE there is no center of expansion. Each point on the expanding balloon surface is equally a point from which the others are receding.
the other points are all getting farther from it.

to follow the analogy you have to put yourself into the 2D surface of the balloon and look at things as a 2D-critter.
there is no other space, outside the balloon surface.
that is how to think of the analogy.

distances between galaxies increase like the distances between pennies glued to the surface of a gradually expanding balloon.

everybody gets repeatedly exposed to this analogy. and learn from it that IN THE SPACE WHERE WE ARE there is no one central point to the expansion.

do you have real trouble grasping that? or are you just kidding (to drive the rest of us nuts) when you keep returning to the "ground zero" idea?

 

[wilgory]

edit due to duplicate post

 

[wilgory]

BoomBoom,

It may help if you consider the raisinbread analogy. Think of a loaf of raisinbread as it cooks. It expands in all directions with the raisins moving away from each other. Think of each raisin as a galaxy. An observer on one raisin sees the others moving away. While an observer on a distant raisin sees the same thing.

It may also help if you consider that there is more to the universe than we can observe optically. What we can see tends to put us in the center of the observable area of the universe. There is more, and we can't be sure of where we are with respect to the "edge". If there is an "edge".

We say the universe is expanding due to the redshifts we observe. There is a redshift caused by the velocity of a galaxy, and one caused by the expansion of space. Using these, we can calculate where a galaxy is currently.

I hope I have helped and not hindered your understanding. As a fellow laymen I thought I would share my understanding of things. There are several discussions on this forum dealing with these questions. Use the search function and search for "universe expansion".

NASA also has a site that is useful in answering questions about the universe.

http://www.nasa.gov/

Also check out these sites.

http://www.math.ucr.edu/home/baez/RelWWW/

http://www.astro.ucla.edu/~wright/cosmolog.htm

 

[marcus]

BoomBoom,

It may help if you consider the raisinbread analogy.

that is a very useful analogy, thanks for presenting it! and also the excellent links.
as I picture it, the raisinbread-dough is being allowed to "rise" by yeast action, before baking, and I think of the dough as filling all the space I can imagine, extending indefinitely in all directions (so that it will not have any boundary and will never meet a wall)

the balloon surface also has this feature of having no boundary---from the 2D-creatures standpoint.

an important thing to warn about, in either case, is thinking of space as a material (like rubber or dough)
the analogy is the geometrical relation between the pennies stuck on the balloon surface---the fact that distances between all are increasing---or the geometrical expanding-distance relation between the raisins

another thing to stress is that GR is a theory of spacetime geometry in which there is no prior space, no rigid framework in which things happen
and therefore the "bigbang" or expanding-space cosmology is not an explosion of crud outwards into a pre-existing empty space
it is an expansion which includes space itself, or more precisely it is an expansion of the metric which is the sum of all geometric relationships.

the material crud is basically just getting a free ride, like the raisins and pennies

so it is impossible to think meaningfully of some kind of 'center point' of the expansion. what is expanding has no boundary and no center.

 

[BoomBoom]

I hope I have helped and not hindered your understanding. As a fellow laymen I thought I would share my understanding of things.

Yes thanks Wilgory (and Marcus). Great links!

I still have a hard time understanding how the immense size of the universe could have come about in such a short period of time, it seems as if the age should be much older to account for this. I don't see why it necessarily needs a "birth", but I guess if we can see another few billion LYs and don't see any formed galaxies that would be proof correct? If we do keep seeing further and further and still see formed galaxies, I guess they will need to keep adjusting the age estimation?

Even a loaf of bread has a center, if the universe is expanding in all directions and it is assumed it had a "birth" from a much more dense and compact state, then there must be a point (or area) of origin.

I will work on educating myself on these matters. Thanks again for your input.

 

[madphysics]

I agree with BoomBoom. The big bang was only at one point, so how can we say that there is no center point.Now, the fact that there remains a center point now remains to be seen.

As the universe expands, the "expansion point" grows in size.It shouldn't dissappear, though.

 

[wilgory]

BoomBoom and madphysics,

If you consider that space-time is what is expanding, you can imagine the "center" you refer to also expanded with the rest of the universe so the "center" is everywhere. We know this because the cosmic background radiation is uniform in all directions. If there was a center we could point to, then we would see the radiation stronger coming from that direction.

Do not think of the expansion as an explosion. That is why I use the raisinbread analogy. Also consider the expansion is 4 dimensional and the analogy is only 3D.

I think with the latest satelite survey we have "seen" back to the first light of the expansion. You can research this on the NASA site. It is a large site, so use the search feature.

 

[pervect]

I agree with BoomBoom. The big bang was only at one point, so how can we say that there is no center point.Now, the fact that there remains a center point now remains to be seen.

As the universe expands, the "expansion point" grows in size.It shouldn't dissappear, though.

While the observable universe may have been concentrated to a very small region at the big bang, the universe as a whole is not considered to have started at a point.

See for instance http://www.astro.ucla.edu/~wright/infpoint.html

How can the Universe be infinite if it was all concentrated into a point at the Big Bang?

The Universe was not concentrated into a point at the time of the Big Bang. But the observable Universe was concentrated into a point. The distinction between the whole Universe and the part of it that we can see is important. In the figure below, two views of the Universe are shown: on the left for 1 Gyr after the Big Bang, and on the right the current Universe 13 Gyr after the Big Bang ...

You'll have to visit the webpage if you want to see the diagrams.

But it's definitely wrong to argue that the universe has a center according to current models. Current models assume the cosmological principle, which assumes the universe is homogeneous and isotropic. This is not compatible with having a 'center'.

 

[madphysics]

I see it now:
the "starting point" of the big bang contained all the matter that forms the universe today, so there is no real expansion point. However, is the universe still expanding from all the points of matter in the universe? Or is contracting?

http://adsabs.harvard.edu/abs/2004astro.ph..3012S

 

[marcus]

I see it now:
the "starting point" of the big bang contained all the matter that forms the universe today, so there is no real expansion point. However, is the universe still expanding from all the points of matter in the universe? Or is contracting?

http://adsabs.harvard.edu/abs/2004astro.ph..3012S

progress.
every point in space can be viewed as the "center" of expansion because the rest is receding from it

you can say "there is no (one unique) center" or you can say
"every point is central".

reality is imperfect---local concentrations of mass like stars bend and pucker, black holes make nearby stuff approach instead of recede, so you can say that reality has local WARTS and zits and imperfections

but when you smooth the picture out and airbrush out the bumps, you get an overall evened-out picture of universal expansion which looks the same from any spot you choose.

from any spot you choose it will always look (aside from some local effects) as if everything is fleeing from that spot

all distances that arent prevented by some sort of "glue" tend to INCREASE BY A CERTAIN PERCENT EACH YEAR
so naturally the big distances increase by more, in absolute terms (because a fixed percent of a bigger thing is bigger)
and therefore the farther away stuff is the faster it is receding

there is no static non-expanding space in which this happens
the metric IS space

likewise the 4D version of the metric IS spacetime

===================
You give link to a paper by William Q. Sumner.
He has 3 papers on the archive:
http://arxiv.org/find/astro-ph/1/au:+Sumner_W/0/1/0/all/0/1

AFAICS no other scholar ever cites these papers. His papers only get cited when he himself cites them in his own writing.

He says that ATOMS IN DISTANT GALAXIES (back in the past) WERE BIGGER SO THEY MADE LONGER WAVELENGTH LIGHT
which is why it is redder.

My advice is learn mainstream physics and astronomy first, before you branch out to the farther reaches of the Fringe.
then when you read something by an isolated eccentric you will enjoy it more because you will appreciate the special weirdnesses for yourself
and won't need to have their unique and wonderful wackiness explained to you. A joke is always funnier if you "get it" yourself.

 

[madphysics]

Gee.
I guess I should learn a little bit more before I open my big mouth.

 

[wilgory]

madphysics,

This link will help sort through the different theories on the web.

http://www.math.ucr.edu/home/baez/RelWWW/HTML/wrong.html

The other links on this thread are excellent places to expand your understanding of what is "known" about the universe.

I may be able to help with a couple of misunderstandings you have about the early universe.

When we push the rewind button at take things back to the early universe. What we can be reasonably sure of is, it was (compared to today) very small (not a point), very dense, and very hot (to hot for matter to form). Matter formed when the universe expanded and cooled enough for it to exist. Before there was matter, what would become matter, was energy.

The other thing is, all of space and time was in the small, dense, and hot universe and started expanding with everything else. It is difficult to grasp this part. It will lead to more questions than I can deal with on a forum and will probably be beyond my ability to explain. If there is anything beyond our space-time continuum, it is in a different space-time continuum. We will never know because we can't observe anything beyond the one we are in.

You might google "LAMBDA COLD DARK MATTER". This is the model of the universe that fits the observations best.

If I have gotten some of this wrong, I hope the more qualified members of this forum will correct me.

 

[BoomBoom]

I think I am getting it...so at the time of BB, the universe was actually still fairly large and the expansion over time is spreading that signature so we see the CMB wherever we look?

One thing I am not getting, however, is that if the velocities of galaxies are greater as the distance is greater, wouldn't that mean the expansion is slowing down rather than accelerating? Since the closer we look to "right now" in time, the slower the velocities and the further back in time we look they are larger. Or do I have that backwards?

 

[wilgory]

BoomBoom,

I think the idea that we see back in time is misleading. What we see when looking through a telescope is an image of what a galaxy looked like when it emitted the light. We don't really see "back in time". Not being a cosmologist I can't say for sure but I think the models of the universe take the distance we look out into space and the time it takes to see things into account when they calculate the expansion.

As I said in my previous post. These questions are getting beyond my ability to answer. Most of your questions have been answered somewhere in this forum or on the websites that the links direct you to. On some of the other sites there are sections called "Frequently Asked Questions" (FAQs). These have been very helpful in my quest to understand the structure of the universe.

 

[madphysics]

I think the idea that we see back in time is misleading. What we see when looking through a telescope is an image of what a galaxy looked like when it emitted the light. We don't really see "back in time". Not being a cosmologist I can't say for sure but I think the models of the universe take the distance we look out into space and the time it takes to see things into account when they calculate the expansion.

We know that light travels over time, but how can we calculate it if we don't have another factor?

 

[Chronos]

Space expands and carries light with it . . . its called expansion. Light waves stretch along with the space they travel through.

 

[BoomBoom]

Space expands and carries light with it . . . its called expansion. Light waves stretch along with the space they travel through.

Does this phenomena cause the light to redshift?

 

[marcus]

Does this phenomena cause the light to redshift?

that's what they tell you in cosmology class is the cause of the cosmological redshift

(you are warned not to consider space as a material, like rubber, but geometrically the analogy is pretty good)

the cosmological redshift ratio of wavelength received to wavelength emitted is exactly the ratio by which distances have increased while the light was traveling.

Like for example space has expanded 1100-fold since the time the CMB photons were last emitted and started flying on their way to us

and their wavelengths are longer by just the same ratio: they are longer now (when we receive them) by a factor of 1100 than they were when some hydrogen atom emitted them or scattered them, sending them on their way.

=============

or if we see a quasar and the light has been redshifted by a factor of 6
that means that distances in the universe have expanded by a factor of 6 during the time the light was traveling on its way to us.

if you can visualize the Maxwell wave equation (by which electromagnetic waves propagate) operating in a space where distances are very gradually increasing then you don't need any other explanation of the cosmological redshift from the one Chronos just told youwavelength now/wavelenght then = spatial scalefactor now/scalefactor then = (or in more casual terms) "size of U now/size of U then"

 

[BoomBoom]

that's what they tell you in cosmology class is the cause of the cosmological redshift

Obviously, a class I never took. :(

Your help has been appreciated.

 

[pervect]

I see it now:
the "starting point" of the big bang contained all the matter that forms the universe today, so there is no real expansion point. However, is the universe still expanding from all the points of matter in the universe? Or is contracting?

http://adsabs.harvard.edu/abs/2004astro.ph..3012S

Note that this is just it a preprint - it hasn't been published in a peer reviewed journal.

However, http://adsabs.harvard.edu/abs/1994ApJ...429..491S apparently has been published. But after reading it, I don't think it makes a lot of sense. Maybe we can get some other people to comment on this paper.

 

[hellfire]

However, http://adsabs.harvard.edu/abs/1994ApJ...429..491S apparently has been published. But after reading it, I don't think it makes a lot of sense. Maybe we can get some other people to comment on this paper.

I don't think this paper is right. The reasoning might apply for free particles, but most of the matter in the universe is bounded to interactions. In that case the behaviour is different, see for example:

In an expanding universe, what doesn't expand?
http://www.arxiv.org/abs/gr-qc/0508052

 

[BoomBoom]

wavelength now/wavelenght then = spatial scalefactor now/scalefactor then = (or in more casual terms) "size of U now/size of U then"

Ok, another layman thought here:

I was reading in some other threads about how expansion is not observable locally, I presume because we are part of a local galaxy cluster or group that has an effect on expansion rates due to gravity interactions.

So I was thinking that all our experience with how light behaves has been in this context (as part of a solar system within a galaxy that is part of a group of other galaxies). All of our assumptions about the properties of light are within this framework.

My point being that perhaps it behaves differently when separated from gravitational effects so that as light leaves a cluster region and enters a large void region, the tug of gravity from the cluster it left as it enters a vacuumous region along with the pull of gravity as it approached us would stretch it and thus give the optical illusion that everything was migrating away from us?

It just seems odd that this great accelerating expansion is virtually undetectable in our local (and present) part of the universe.

 

[Chronos]

Expansion is much too small to observe locally. At 72 meters per megaparsec, local effects are nonexistent. Assuming it is a force, such as gravity, it may only have consequences in the vast empty spaces between galaxies.

 

[marcus]

Expansion is much too small to observe locally. At 72 meters per megaparsec, local effects are nonexistent.

I think you meant to say "72 kilometers per second" instead of "72 meters"

the first is a recession speed, the second is a length and wouldn't make logical sense in the context.

 

[marcus]

Ok, another layman thought here:

I was reading in some other threads about how expansion is not observable locally, ...

My point being that perhaps it behaves differently when separated from gravitational effects so that as light leaves a cluster region and enters a large void region, the tug of gravity from the cluster it left as it enters a vacuumous region along with the pull of gravity as it approached us would stretch it and thus give the optical illusion that everything was migrating away from us?

It just seems odd that this great accelerating expansion is virtually undetectable in our local (and present) part of the universe.

It sounds like you are skeptical of expansion. You don't want to believe in it. My attitude is that people should be allowed to believe what they want and whatever you want to believe is fine.

I only think it would be a good idea if everyone in the discussion learns about and understands something of the mainstream consensus model cosmology.

Along those lines, I can explain the mainstream view and why what you are saying doesn't make sense, but I don't want to ARGUE or try to PERSUADE you of anything. You should go on believing whatever feels right to you.
============

redshifts are not the only evidence for expansion. they are part of a huge body of interlocking different kinds of evidence supporting GR
GR does not predict expansion of distances between bound-together objects. So it is no surprise that we don't see expansion redshift locally.
We see a huge amount exactly where GR tells us to expect it.

you offer an alternative explanation for redshifts, but it is faulty:
light IS redshifted by leaving a concentration of mass and this has been observed ON EARTH in labs. it is also blueshifted as it approaches a concentration of mass----so in a rough sense the effects "cancel". In your alternative explanation you get half of it backwards---you describe a gravitational redshift at both ends of the trip. But that's all right, what you describe wouldn't work anyway, because:

this socalled gravitational redshift has been measured and is not enough to explain the cosmological redshift. it does not even come within a factor of 1000 of being able to explain.

(also it is a bad idea to think of gravity "tugging" on light and "stretching" it as if it were a force acting on a spring====lightwaves aren't material objects===material analogy can be misleading)

the CMB light has been redshifted by a factor of around 1000 and it does not come from any concentration of mass! Your picture of light getting redshifted by "leaving" another galaxy doesn't apply. CMB light came from space uniformly filled with ionized gas before any stars and galaxies had formed

You are welcome to disbelieve this, BoomBoom But you are struggling against a vast body of consistent observation. People have been trying to find alternative explanations for this or that feature ever since the 1930s.

they never manage to find a way to explain away ALL the different sorts of evidence.

just as you are doing with your "gravity tugging" explanation of the redshift, there have been people who made a big effort to promote other alternative explanations like "tired light" which work better than yours. these are professional astronomers I am talking about and they have worked hard at it. but for 70 years they've tried and the alternatives just poop out.

Of course we all know the standard model is WRONG. It is based on Einstein's 1915 theory of gravity and we know for sure that is wrong because it predicts singularities (breaks down in certain situations)

And people are working on FIXING the basic gravity theory and perfecting the cosmological model.

this is happening----but the improved models will still have distances expand!

The improved model cosmology which is emerging from the confusion of many researchers' efforts will NOT BE ANY MORE ACCEPTABLE TO YOU.

We know GR and LCDM are wrong, and they are being improved. But what is wrong about them is not what you find wrong, so the progress under way will not make it better for you.

right now, I accept GR and LCDM provisionally, as amazingly good fits to reality despite their obvious flaws-----and I am trying to glimpse the vague outlines of the improved picture that will gradually come to replace them.

 

[Chronos]

Correct, 72 km/s. I was wondering why all my calculations were off by 1000!

 

[BoomBoom]

I only think it would be a good idea if everyone in the discussion learns about and understands something of the mainstream consensus model cosmology.

I agree and thank you for the education. I have learned much since coming here.

I apologize for my uninformed speculation and will refrain from speculating in the future.


On another note:

I was curious about how they determine the mass of galaxies. Is it assumed that most stars have solar systems such as ours or are individual masses determined from observations of surrounding materials?

When I hear predictions about the mass of the universe, I can't help but think it must have a HUGE margin of error.

 

[marcus]

..

When I hear predictions about the mass of the universe, I can't help but think it must have a HUGE margin of error.

that is something that professionals (grad student cosmologists) can speak to like SpaceTiger and Wallace

you are necessarily talking mass DENSITY, that is mass per cubic lightyear volume. because nobody knows what the volume is.

I was curious about how they determine the mass of galaxies. Is it assumed that most stars have solar systems...

You can tell the mass of a spiral galaxy by how fast the edges are whirling around, which you can tell by doppler, if you can see it edge on. part of the edge is coming towards and part is going away and the dopplershift tells the speed.

that is similar to how you tell the mass of the sun----by how fast a planet (at some given distance) whirls around it.

Then if you know the mass of spiral galaxies you can match that up with their luminosity---how much light they make (and adjust the scale for various minor corrections). brighter means more and more means more massive. you use empirically discovered relationships.

And then you can use that mass/luminosity scale to tell the masses of ALL galaxies, not just the spiral ones.

============

and also you can assume UNIFORM DENSITY on average and if you do that then you only have to estimate the mass per cubic lightyear in a representative sample volume like space around the Local Group and halfway out to the next cluster. Or some larger sample box of space.
You measure inside that box, by the mass-to-light ratio and the rotation of spirals, and then you just ASSUME that the density outside the box is the same as inside.

And they have gotten very good at this so the estimates of matter density are surprisingly consistent. You can come in and pick an entirely different box and (if it is big enough to contain the average and not some fluke) it will turn out to have the estimated density. The universe is pretty uniform.
============

There is another angle which depends on CURVATURE. What I just told you doesn't depend majorly on Gen Rel, the ruling theory of gravity, which says how mass density (actually total energy density including possible immaterial energy) BENDS SPACE.
Now GR has been tested a lot of ways and people tend to trust it. If you believe GR then you can reckon the overall density of energy (or mass) in space by looking to see how curved it is (and how fast distances are expanding, which is another aspect of curvature).

the massenergy density you get by measuring expansion rate and spatial curvature (which turns out to be nearly zero so the main contributor is expansion)
OUGHT to equal the massenergy density you get by doing these huge galaxy surveys inside these big sample boxes.

My advice is, for starters don't worry about that approach, it is the one that is responsible for a confusing discrepancy that people fudge by saying "dork energy". Study that later
=============
the main thing is they estimate the space density of ordinary and dark matter by actually doing surveys of what is in sample boxes.
Little known fact: astronomers are some of the best statisticians on the planet.

 

[Chronos]

BoomBoom, space is really big, that is all we know for sure. Big enough that we haven't yet seen 'circles in the sky'.

 

[Wallace]

When I hear predictions about the mass of the universe, I can't help but think it must have a HUGE margin of error.

I'm not sure where you have heard such things! As marcus points out what we can make predictions and measurement of is the energy density of the universe, mass per volume. One way we can determine this is by looking at the CMB. The pattern of slight fluctuations in the temperature of the observed radiation is highly sensitive to variations in the energy density of the Universe.

 

[BoomBoom]

BoomBoom, space is really big, that is all we know for sure.

I know, this is precisely why it is difficult to grasp the concept of it ever being "really small".

 

[marcus]

When I hear predictions about the mass of the universe, I can't help but think it must have a HUGE margin of error.

As I said, it's really up to Wallace or SpaceTiger to tell you what the current ideas of the margin of error are. I think they are surprisingly narrow like around 10 percent. Not huge anyway.

The thing is you can pick your sample box. The universe is remarkably uniform and there is so much data. Whereever you choose to look and measure you find that it's about the same density!

I actually think the density of the universe is one of those basic, fairly reliable, numbers that one should KNOW BY HEART because it is a basic fact about where we live.

Like the circumference of the earth, or the percentage dry land. I mean, it's your universe, so shouldn't you know by heart what its density is?

 

[marcus]

In case you were wondering, BoomBoom, it is about one joule
per cubic kilometer.

A joule amount of energy is like when you lift a physics textbook about 10 centimeters (4 inches) off the table. That amount of energy.

 

[BoomBoom]

In case you were wondering, BoomBoom, it is about one joule
per cubic kilometer.

A joule amount of energy is like when you lift a physics textbook about 10 centimeters (4 inches) off the table. That amount of energy.

LOL...nice analogy!

This density in an expanding universe should increase the farther we look correct? I am assuming that density is for "today's" universe...

 

[BoomBoom]

I mean, it's your universe, so shouldn't you know by heart what its density is?

Do you happen to know of any good sites out there that may have a decent mapping of our current universe? I know there are many that come up in searches, but was just wondering if you have a favorite. Thanx!