APOD: A Redshift Lookup Table for our Universe (2013 Apr 08)

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Expand view Topic review: APOD: A Redshift Lookup Table for our Universe (2013 Apr 08)

Re: APOD: A Redshift Lookup Table for our Universe (2013 Apr

by neufer » Tue Apr 09, 2013 5:50 pm

Chris Peterson wrote:
Ann wrote:
Yes, "unknown size" divided by a thousand doesn't make much sense...
But I think we can quite safely say that when the photons were released, the Universe was a good deal larger than Betelgeuse!
Your Cosmology Calculator (set to: H0 = 67.8, OmegaM = 0.268, Omegavac = 0.692, z = 1089)

gives a scale of 0.069 kpc/" => equivalent to a circumference of ~ 89 Mpc

or slightly smaller than the Virgo Supercluster (circumference of ~ 104 Mpc).

Re: APOD: A Redshift Lookup Table for our Universe

by K1NS » Tue Apr 09, 2013 2:58 pm

Chris Peterson wrote: Per a previous discussion here, "nomograph" isn't quite the right word. As Art suggested, "slide" is better, since the values are always read off horizontally (a nomograph typically involves a calculation of two variables, made by drawing a line between those values in a pair of columns, and reading the answer where that line intersects a third column).
Actually, nomographs (or nomograms) can involve several variables. and the lines may or may not be straight. According to the Oxford English Dictionary, nomograms have been around since about 1909. The name comes from the Greek word "nomo" which simply means law, so nomograms are meant to facilitate calculations according to some mathematical or physical law, such as redshift in the universe.

I guess the name "slide" was suggested because this nomograph has a cursory (no pun intended) resemblance to a slide rule. And as a matter of fact, some nomographs are physical devices with cursors and reticules.

I am not aware of the previous discussion, so maybe my comments have already been covered. But I still believe this "table" or "slide" is best called a nomograph.

Re: APOD: A Redshift Lookup Table for our Universe (2013 Apr

by eltodesukane » Tue Apr 09, 2013 2:56 pm

GoatGuy wrote:Sorry to bother about what may have a trivial answer,

But what's up with the 1" scale and the kpc scales? Seems like (for the 1") 8.7 is the magic number, around which there's a kind of strange symmetry. I would have thought that there's a linear distance-size relationship. Obviously, there's something more complicated to this than meets the eye. :|
In the past the universe was smaller, but it still must fit onto the celestial sphere, so it`s angular size increases as we go back in time. The big bang itself has size zero, but it`s angular size is the whole sky.

Re: APOD: A Redshift Lookup Table for our Universe (2013 Apr

by Chris Peterson » Tue Apr 09, 2013 2:23 pm

Ann wrote:Yes, "unknown size" divided by a thousand doesn't make much sense...
But I think we can quite safely say that when the photons were released, the Universe was a good deal larger than Betelgeuse!

Re: APOD: A Redshift Lookup Table for our Universe (2013 Apr

by MargaritaMc » Tue Apr 09, 2013 7:21 am

Ann wrote:
By the way, what is "forrader"? (It looks a bit like "förrädare", which is "traitor" in Swedish, but I guess not...)

Ann
Sorry, Ann - it's early in the morning and I didn't think! (My brain needs much coffee to get it moving...) :roll:
'Forrader' is rather old-fashioned English slang meaning 'forward' ('forwarder'). So, "we are no further forrader" just means that we've made no advance.

It isn't a useful bit of linguistic knowledge as I may be one of the few people left on the planet who automatically use the term... :D

Now - COFFEE!
Margarita

Re: APOD: A Redshift Lookup Table for our Universe (2013 Apr

by Ann » Tue Apr 09, 2013 7:06 am

Yes, "unknown size" divided by a thousand doesn't make much sense... but thanks a lot for your answer, Margarita! :D It does say how much bigger the unvierse has grown since that time, certainly!

By the way, what is "forrader"? (It looks a bit like "förrädare", which is "traitor" in Swedish, but I guess not...)

Ann

Re: APOD: A Redshift Lookup Table for our Universe (2013 Apr

by MargaritaMc » Tue Apr 09, 2013 7:00 am

Ann wrote:
Chris Peterson wrote:
MargaritaMc wrote:This post is only tangentially linked to today's Apod, but it is this chart by Pilipenko that sparked off my interest when it was first posted in Breaking Science News some days ago.

I'm intrigued to know the redshift of CMB and what the emitting wavelength was.

The quotations below (and other sources I've looked at) give the estimated temperature of the original radiation but not the wavelength.
That is your answer. The CMB is not seen as one wavelength today, because it was not emitted as a single wavelength. The CMB is observed as a blackbody spectrum, which peaks at about 2 mm. That is the blackbody spectrum equivalent for a radiator at 2.7 K. When the photons were emitted, the source temperature was about 3000 K, meaning the spectrum peaked at a bit under 1 micrometer, just into the near IR. Visually, the light would have appeared warm white.
You mean we're talking about a universe-sized Betelgeuse? :shock: How big was that universe?

Ann
Our Universe Part 11: Decoupling Epoch
The universe is now about 379,000 years old. It has expanded to about a thousandth of its present size and it has cooled to about 4000 K.

http://sciexplorer.blogspot.com.es/2011 ... epoch.html


But as we don't know the "present size" of the universe that doesn't take us any further 'forrader' :!:

Margarita

Re: APOD: A Redshift Lookup Table for our Universe (2013 Apr

by Ann » Tue Apr 09, 2013 2:45 am

Chris Peterson wrote:
MargaritaMc wrote:This post is only tangentially linked to today's Apod, but it is this chart by Pilipenko that sparked off my interest when it was first posted in Breaking Science News some days ago.

I'm intrigued to know the redshift of CMB and what the emitting wavelength was.

The quotations below (and other sources I've looked at) give the estimated temperature of the original radiation but not the wavelength.
That is your answer. The CMB is not seen as one wavelength today, because it was not emitted as a single wavelength. The CMB is observed as a blackbody spectrum, which peaks at about 2 mm. That is the blackbody spectrum equivalent for a radiator at 2.7 K. When the photons were emitted, the source temperature was about 3000 K, meaning the spectrum peaked at a bit under 1 micrometer, just into the near IR. Visually, the light would have appeared warm white.
You mean we're talking about a universe-sized Betelgeuse? :shock: How big was that universe?

Ann

Re: APOD: A Redshift Lookup Table for our Universe (2013 Apr

by neufer » Tue Apr 09, 2013 2:11 am

GoatGuy wrote:
... what's up with the 1" scale and the kpc scales? Seems like (for the 1") 8.7 is the magic number, around which there's a kind of strange symmetry. I would have thought that there's a linear distance-size relationship. Obviously, there's something more complicated to this than meets the eye. :|
Think of yourself at the north pole with a cold clear global atmospheric inversion near the surface such that you can literally see as far as you like. By looking down the Oº meridian (i.e., line of longitude) and the 1º meridian you view distant objects that are physically further & further apart until (as you view objects as far away as the equator) they are 60 nautical miles apart. After that, more distant objects in the Southern Hemisphere are physically closer & closer together until you simply observe the tiny South pole down both meridians.

Hence, in this situation, 60 nautical miles is "the magic number around which there's a kind of strange symmetry." This symmetry happens at precisely the half way point (i.e., 9Oº latitude distance) or in polar stereographic projection terms at precisely a radius z=1 (vs. z= ∞ for the South Pole).

The fact that the Redshift Lookup Table doesn't also show strange symmetry at precisely "the half way point" (i.e., 13.8/2 = 6.9 Gyr distance) or at precisely z=1 (vs. z= ∞ for the tiny Big Bang) is due to the complication of Dark Energy Expansion. (This expansion situation is probably analogous to a pear shaped Earth.)

Re: APOD: A Redshift Lookup Table for our Universe

by Chris Peterson » Mon Apr 08, 2013 6:01 pm

K1NS wrote:
zbvhs wrote:It's a nomograph . . .
Yes, that's the word. It's not just a "table," it's a nomograph! :D
Per a previous discussion here, "nomograph" isn't quite the right word. As Art suggested, "slide" is better, since the values are always read off horizontally (a nomograph typically involves a calculation of two variables, made by drawing a line between those values in a pair of columns, and reading the answer where that line intersects a third column).

Re: APOD: A Redshift Lookup Table for our Universe

by K1NS » Mon Apr 08, 2013 5:55 pm

zbvhs wrote:It's a nomograph . . .
Yes, that's the word. It's not just a "table," it's a nomograph! :D

Re: APOD: A Redshift Lookup Table for our Universe (2013 Apr

by stephen63 » Mon Apr 08, 2013 5:20 pm

BMAONE23 wrote:
stephen63 wrote:Never mind. The objects ARE receding faster, as indicated by the red shift. :derp:
I don't think they are receding faster than my hair line :wink:
Who knew? A relativistic bald spot!

Re: APOD: A Redshift Lookup Table for our Universe (2013 Apr

by Beyond » Mon Apr 08, 2013 5:11 pm

BMAONE23 wrote:
Beyond wrote:I've got an automatic. I don't shift anymore. But when i used to shift, i never shifted in the red. :no: :mrgreen:
Well, shifting in the Red is a feat that takes large amounts of Dark Energy to accomplish and unfortunately most Datsun 280Z's still run on Regular energy
haha, that's why Boomer12k hasn't tried driveing his 280-Z to Jupitor. However, i see that he is only 15 posts away from 500, when one is declared to be officially insane, so who knows...

Re: APOD: A Redshift Lookup Table for our Universe (2013 Apr

by BMAONE23 » Mon Apr 08, 2013 5:06 pm

stephen63 wrote:Never mind. The objects ARE receding faster, as indicated by the red shift. :derp:
I don't think they are receding faster than my hair line :wink:

Re: APOD: A Redshift Lookup Table for our Universe (2013 Apr

by BMAONE23 » Mon Apr 08, 2013 5:02 pm

Beyond wrote:I've got an automatic. I don't shift anymore. But when i used to shift, i never shifted in the red. :no: :mrgreen:
Well, shifting in the Red is a feat that takes large amounts of Dark Energy to accomplish and unfortunately most Datsun 280Z's still run on Regular energy

Re: APOD: A Redshift Lookup Table for our Universe (2013 Apr

by GoatGuy » Mon Apr 08, 2013 4:40 pm

Sorry to bother about what may have a trivial answer,

But what's up with the 1" scale and the kpc scales? Seems like (for the 1") 8.7 is the magic number, around which there's a kind of strange symmetry. I would have thought that there's a linear distance-size relationship. Obviously, there's something more complicated to this than meets the eye. :|

Re: Back to the future?

by stephen63 » Mon Apr 08, 2013 2:13 pm

neufer wrote:Why is "2013 April 8" off the scale on the age chart :?:

(Can I postpone now sending in my income taxes?)
“A citizen can hardly distinguish between a tax and a fine, except that the fine is generally much lighter.” – GKC ILN, 5/25/31

So, do you want a tax+fine? :lol2:

Re: APOD: A Redshift Lookup Table for our Universe (2013 Apr

by MargaritaMc » Mon Apr 08, 2013 2:11 pm

Image

Thank you, Chris and Art, very much indeed.

Margarita

Re: APOD: A Redshift Lookup Table for our Universe (2013 Apr

by neufer » Mon Apr 08, 2013 1:46 pm

MargaritaMc wrote:
So, at what wavelength(s) would the
Cosmic Microwave Background originally have been emitted?  And what would its redshift be?
z = 1089

2.72548 K x (1 + 1089) = 2971 K

Peak radiation in the infrared = 975 nm
https://en.wikipedia.org/wiki/Redshift#Extragalactic_observations wrote:
<<The most distant objects exhibit larger redshifts corresponding to the Hubble flow of the universe. The largest observed redshift, corresponding to the greatest distance and furthest back in time, is that of the cosmic microwave background radiation; the numerical value of its redshift is about z = 1089 (z = 0 corresponds to present time), and it shows the state of the Universe about 13.7 billion years ago, and 379,000 years after the initial moments of the Big Bang.>>

Re: APOD: A Redshift Lookup Table for our Universe (2013 Apr

by Chris Peterson » Mon Apr 08, 2013 1:43 pm

MargaritaMc wrote:This post is only tangentially linked to today's Apod, but it is this chart by Pilipenko that sparked off my interest when it was first posted in Breaking Science News some days ago.

I'm intrigued to know the redshift of CMB and what the emitting wavelength was.

The quotations below (and other sources I've looked at) give the estimated temperature of the original radiation but not the wavelength.
That is your answer. The CMB is not seen as one wavelength today, because it was not emitted as a single wavelength. The CMB is observed as a blackbody spectrum, which peaks at about 2 mm. That is the blackbody spectrum equivalent for a radiator at 2.7 K. When the photons were emitted, the source temperature was about 3000 K, meaning the spectrum peaked at a bit under 1 micrometer, just into the near IR. Visually, the light would have appeared warm white.

The ratio of current peak wavelength to emitted peak wavelength is about 1100, which is therefore the redshift of the CMB.

Re: APOD: A Redshift Lookup Table for our Universe (2013 Apr

by MargaritaMc » Mon Apr 08, 2013 1:20 pm

This post is only tangentially linked to today's Apod, but it is this chart by Pilipenko that sparked off my interest when it was first posted in Breaking Science News some days ago.

I'm intrigued to know the redshift of CMB and what the emitting wavelength was.

The quotations below (and other sources I've looked at) give the estimated temperature of the original radiation but not the wavelength.

http://archive.ncsa.illinois.edu/Cyberi ... mpany.html
But after about 300,000 years, the opaque soup of nuclear matter and radiation began to clear. By this time, the temperature of the universe dropped to 3,000 K. ... The vast sea of photons created during the earliest epochs prior to recombination persist to this day, in the form of cosmic microwave background that pervades the universe. No longer so energetic after being stretched by the expansion of the universe ... this radiation has cooled to a chilly 2.73 K
http://www.astro.ucla.edu/~wright/CMB.html
But even though the temperature of the Universe changes as it evolves, with TCMB = To (1+z), the Universe looks isothermal because the redshifting of radiation makes the warmer but redshifted distant Universe appear to have exactly the same temperature as the Universe today.
The CMBR has a thermal black body spectrum at a temperature of 2.725 K, so it peaks in the microwave range frequency of 160.2 Ghz(1.9 mm wavelength).
http://www.universetoday.com/79777/cosm ... radiation/

So, at what wavelength(s) would the
Cosmic Microwave Background originally have been emitted?  And what would its redshift be?

Can anyone help me?
Margarita

Re: APOD: A Redshift Lookup Table for our Universe (2013 Apr

by Chris Peterson » Mon Apr 08, 2013 1:17 pm

stephen63 wrote:Never mind. The objects ARE receding faster, as indicated by the red shift. :derp:
Well, sort of. Keep in mind that cosmological redshift isn't an indicator of how fast objects are receding (which would be Doppler redshift), but of the amount that space has expanded in the time that the light has been traveling. The distinction can be subtle, but it's important.

Re: APOD: A Redshift Lookup Table for our Universe (2013 Apr

by Chris Peterson » Mon Apr 08, 2013 1:16 pm

drollere wrote:very nice. the original paper has added scales for small z and recent lookback times.
i hope ned wright soon updates his cosmological calculator, which i've found very useful ...

http://www.astro.ucla.edu/~wright/CosmoCalc.html
What's to update? His calculator gives exactly the same values as today's calculator. Maybe you want the default hubble and omega values updated so you don't have to type them in?

Re: APOD: A Redshift Lookup Table for our Universe (2013 Apr

by stephen63 » Mon Apr 08, 2013 1:15 pm

Never mind. The objects ARE receding faster, as indicated by the red shift. :derp:

Re: APOD: A Redshift Lookup Table for our Universe (2013 Apr

by zbvhs » Mon Apr 08, 2013 1:14 pm

It's a nomograph harking back to the sliderule era bc (before computers). You lay a straight-edge across between z values and read values of the scales in between. For example, for z = 2, I read H = 204, dm = 46, age = 3.3, time = 10.5, and so forth. Do these numbers sound right? My engineering instincts quail at the thing, however. Units are not shown! The author may show how to use it somewhere, but I didn't look that far into it.

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