can we calculate the orgin of the big bang based on the wmap and drift of galaxies?
No, all we can conclude is it has no center, or edge.
The matter/energy was not evenly distributed after the big bang is this correct? I like to think of the big bang as all matter/energy in a perfect sphere that explodes out perfect and symetrical, but the evidence proves otherwise I guess? Other branes pulling perhaps on our universe altered the expansion in different areas? The rate of expansion has increased over time making it difficult to extrapolate back as well I suppose?
Perhaps a supermassive blackhole resides in the spot in our current universe where the big bang occurred????
I answered this already in your other thread, fyi.
BB was not a localized event. Various factors have influenced the rate of expansion , depending on which period we speak of. Currently , the universe appears to expand greatly due to dark energy.
Scientifically it is nonsensical to speak of an edge / center , how can we define boundaries to something we can't measure / theorize.
The matter and energy of the universe was very nearly, but, not perfectly smoothly distributed. Slightly overdense regions existed which became stars, galaxies, clusters of galaxies, etc. These initial overdense regions were, however, randomly distributed throughout the universe which gives it a homogenous and isotropic appearance. Take a look at the 2MRS map - http://www.cfa.harvard.edu/news/2011/pr201116.html - and the SDSS map - http://www.sdss.org/includes/sideimages/sdss_pie2.html for a visual reference.
I think that Universe is so much big so that any point can be taken as centre.
How do you justify this? If a circle is big enough does it suddenly have the center everywhere inside it?
In regard to what ? >
That is only true if the universe is spatially infinite. We have no compelling evidence it is, or is not.
There is no such 'spot' as far as is theorized.....
What sort of 'galaxy drift' do you imagine?
Simply thought a computer could extrapolate back if we had all the evidence (expansion rate, size of the visable universe, current speed of galaxies, etc) along with the WMAP, but doesn't sound like thats possible. Drift in respect to CMB? No point of reference though I guess. Thanks for clearing it up.
The big bang was NOT an explosion. The entire universe, everywhere, was filled with an extremely hot bath of radiation and plasma ('quark-gluon plasma'). As time passed, the universe expanded, the radiation cooled, and the plasma became less dense. Eventually, evenly distributed clouds of gas began to form, eventually becoming the galaxies.
When I say that the universe expands, let me explain what that means. Because the universe is homogeneous and evenly distributed over large scales, the universe expands from EVERY point in intergalactic space. Every galaxy appears to be at the center, as the space in between galaxies is expanding.
So, firstly, there is no center. The big bang was a moment in time, not a location in space. Every galaxy appears to be at the center. Second, there is no edge or boundary. If the universe is finite, then it is either simply or non-simply connected. That is, it wraps back around on itself, so that traveling sufficiently far will bring you back to your original poison.
There is no centre everybody is rushing away from me no matter where I go in the universe, just like what happens when I use my wrong aftershave. And it was like that at every point inside the universe right from the start.
People have asked me this question so often and I often wondered why this idea is so common. I now think I know who we have to blame: the people that do the graphics for popular science tv-shows. They always show a point in the distance on the screen and then that point starts to expand more or less violently depending on the channel. As if we could observe the big bang from "outside the universe". In that picture of an expanding sphere there is a very clear centre.
But that picture is complete nonsense. We can only observer the universe from the inside. And inside no place is more equal than the rest. We are stuck with universal equality.
We have a FAQ about this: https://www.physicsforums.com/showthread.php?t=506991 [Broken]
Also in case nobody mentiond it, WMAP shows a remarkably uniform distribution of radiation in all directions,,,all around us..so there is nowhere else to "look"...
Galaxies drift locally in random directions...for example, Andromedia and our own Milky way are approaching each other....many others move apart in every imaginable direction locally. But they all move apart at vast cosmological distances.
A good way to think about the lack of an origin is if the universe modeled as a two dimensional surface of a balloon...NOT the center of the balloon, just an expanding surface.
If you search BALLOON ANALOGY in these forums, you'll turn up dozens of discussions.
Why aren't our nearer galaxies accelerating away from us at the same speed as those viewed 13 billion years ago? Also why do 13 billion year old galaxies accelerate faster that 12 billion year old which accelerate faster than 11 billion year old etc etc?
You're asking about distance growth speeds at various "lookback times". It's kind of interesting. Distances have been growing all along, for the whole 13.7 billion years. But for the first 7 billion years or so their growth was decelerating. Then around the 7 billion year mark the growth curve started getting steeper.
You can see it on this plot. The heavy solid line is the standard model one. You can see it starting off convex (getting less steep) and then around -6 or -7 (around 6 or 7 billion year lookback) it gets concave and the slope starts steepening.
The deceleration and acceleration of distance growth is a fairly subtle effect so its good to get an idea of the distance growth rates themselves. Here's a table if you want to look at a few speeds of distance growth at various times in the past. https://www.physicsforums.com/showthread.php?p=4022179#post4022179
Keep in mind that these are not like speeds of ordinary motion. In a uniform pattern of expanding distances nobody gets anywhere---everybody just gets farther apart. So we not talking about travel speeds. Distance expansion can easily be faster than the speed of light, indeed for large distances it typically is.
On the Caltech graph I am assuming that the redshift axis is for another graph. Otherwise we would be getting future blue shifts.
If we had an anomaly which was spherical and was expanding at a rate faster than the surrounding universe then compaction would shrink the space in that area to accommodate this stretching. At what point would this shrinkage be equivalent to a black hole. I am not saying this is possible but if we think of black holes as space compaction maybe it would bring some new ideas.
Also we assume that objects would be torn apart by the gravitational forces in black holes but the universe stretches and we aren't torn apart. It may be that inside a black hole to the observer it is like a 13 billion year big crunch. Also inside a black hole doppler redshift I would assume would appear larger at greater distances.
That's an interesting guess! But actually the redshift scale belongs there as an alternative to the regular scale on the left side of the plot.
The point is we don't receive light from the future. Our galaxy sends light to the future.
So for us to send them a normal wavelength (say for example 1 meter) wave we would have to first compress it.
Across from scalefactor 1.5 there should be written
because we have to shorten the wavelength by a third in order for it to get to those people.
(They are living at a time when distances are 50% larger than now.)
Across from scalefactor 2.0 on the plot, very near the top, should be written
because those people are living at a time when distances are TWICE what they are now.
So in order to make sure they receive a normal size wavelength we have to shorten what we send them by half---we have to reduce the wavelength by 50%
When you are thinking redshift you are always thinking from the perspective of the present moment, what we receive from the past, or send to the future.
If you use the letter a(t) for the scalefactor at time t, then the formula for z is
1+z = a(now)/a(then) = a(us)/a(other people)
If they live when distances are half what they are now, then 1+z = 2, so z = 1
If they live when distances are twice what they are now, then 1 + z = 0.5 so z = - 0.5
f they live when distances are 1.5 what they are now, then 1 + z = 0.666 so z = - 0.333
I'm just repeating what I said earlier but with a formula.
I'm glad you had a look at the scalefactor curve at the Caltech site.
It is from a valuable article by Charley Lineweaver. For another Charley article, try the SciAm link in my signature. It is also enlightening and well illustrated.
Let's take the ripples in a pond scenario. I am at point a somewhere in a pond let's call me object A. Two other objects B and C are at remote distances. Object C is twice as far away from me as object B. If ripples are started at both points B and C at the same time. Object C's ripple takes twice as long to reach me. If I measure the diameters of the received ripples these will have been magnified by a significant amount. Neither object B or C have moved away from me but some amplifying factor, the outspreading wave, has increase the magnitude I perceive. This of course is not an analogy that can be directly applied to the universe, but if we didn't know the proper cause and effect of this ripple phenomena with any certainty we could apply all sorts of theoretical models to it and make them sound reasonable.
Thank you for bearing with me. I like to be devil's advocate sometimes.
I know that the supernova studies showed objects as more distant than expected, but if those objects are further away due to a stretching of spacetime then we should perceive an increase in object size. Matter is not independent of spacetime and surely must be affected by this stretching. Are those distant galaxies larger than expected? Has anyone tested for this?
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