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jarroe
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can we calculate the orgin of the big bang based on the wmap and drift of galaxies?
jarroe said: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 black hole resides in the spot in our current universe where the big bang occurred?
jarroe said: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 black hole resides in the spot in our current universe where the big bang occurred?
Ank!t said:I think that Universe is so much big so that any point can be taken as centre.
Ank!t said:I think that Universe is so much big so that any point can be taken as centre.
That is only true if the universe is spatially infinite. We have no compelling evidence it is, or is not.Ank!t said:I think that Universe is so much big so that any point can be taken as centre.
Perhaps a supermassive black hole resides in the spot in our current universe where the big bang occurred?
jarroe said: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 black hole resides in the spot in our current universe where the big bang occurred?
. Drift in respect to CMB?
hubble_bubble said: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?
marcus said: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.
http://ned.ipac.caltech.edu/level5/March03/Lineweaver/Figures/figure14.jpg
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.
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.hubble_bubble said:On the Caltech graph I am assuming that the redshift axis is for another graph. Otherwise we would be getting future blue shifts.
marcus said: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
- 0.333
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
- 0.5
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 wen distances are twice what they are now, then 1 + z = 0.5 so z = - 0.5
f they live wen 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.
http://ned.ipac.caltech.edu/level5/March03/Lineweaver/Figures/figure14.jpg
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.
hubble_bubble said: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?
The center of the universe is a concept that has been debated by scientists and philosophers for centuries. According to the Big Bang theory, the universe does not have a specific center. Instead, it is expanding from a single point, known as the singularity, which is thought to have existed around 13.8 billion years ago.
The Big Bang theory is the most widely accepted scientific explanation for the origin of the universe. It states that the universe began as a singularity, a point of infinite density and temperature. This singularity expanded rapidly, creating space, time, and all matter and energy in the universe.
The Big Bang theory was first proposed by Belgian astronomer Georges Lemaitre in the 1920s. It was further developed by scientists such as George Gamow and Edwin Hubble in the following decades. The theory gained widespread acceptance in the 1960s after the discovery of the cosmic microwave background radiation, which is considered a remnant of the Big Bang.
There are several lines of evidence that support the Big Bang theory. The cosmic microwave background radiation, the abundance of light elements in the universe, and the observed redshift of galaxies all provide strong evidence for the expansion of the universe from a single point. Additionally, the Big Bang theory accurately predicts the observed distribution of galaxies and the rate of expansion of the universe.
While the Big Bang theory is the most widely accepted and supported explanation for the origin of the universe, there are other theories that have been proposed. These include the Steady State theory, which suggests that the universe has always existed and is continuously creating matter, and the Inflation theory, which proposes a rapid period of expansion in the early universe. However, these theories have not been as extensively supported by evidence as the Big Bang theory.