Re: APOD: Planck Maps the Microwave Background (2013 Mar 25)
Posted: Tue Mar 26, 2013 1:04 pm
by ignacio_db
Thanks for the explanation. So, to be clear, one should think this as matter (dark and regular) measured in its energy equivalence via mc^2 and then compared with dark energy? In that case, the importance of dark energy strikes me as even more impressive, given the huge conversion factor involved.
Ignacio
Re: APOD: Planck Maps the Microwave Background (2013 Mar 25)
Posted: Tue Mar 26, 2013 2:21 pm
by Chris Peterson
ignacio_db wrote:Thanks for the explanation. So, to be clear, one should think this as matter (dark and regular) measured in its energy equivalence via mc^2 and then compared with dark energy? In that case, the importance of dark energy strikes me as even more impressive, given the huge conversion factor involved.
Correct, modern physics views the contents of the Universe as being energy. Matter is simply a state of energy, in the way that ice is a state of water. When, where, and why some of that energy is in the matter state is an interesting question that informs cosmological models, of course, but in the end, it's still all just energy. And everything we easily see- ordinary matter and light- represent just a few percent of the total.
Re: APOD: Planck Maps the Microwave Background (2013 Mar 25)
Welcome to the Planck ‘toolkit’ – a series of short questions and answers designed to equip you with background information on key cosmological topics addressed by the Planck science releases. The questions are arranged in thematic blocks
Margarita
Re: APOD: Planck Maps the Microwave Background (2013 Mar 25)
Posted: Tue Mar 26, 2013 10:27 pm
by bls0326
Why the egg-shaped universe picture? Is the universe really that way or is this just a representation of a 3 dimensional sphere in 2 dimensions?
Re: APOD: Planck Maps the Microwave Background (2013 Mar 25)
Posted: Tue Mar 26, 2013 10:38 pm
by Chris Peterson
bls0326 wrote:Why the egg-shaped universe picture? Is the universe really that way or is this just a representation of a 3 dimensional sphere in 2 dimensions?
The data represents the 2D surface of a sphere, not the 3D volume. We are seeing the projection of a spherical surface onto a plane. This map uses a Mollweide projection because it preserves area proportions.
Re: APOD: Planck Maps the Microwave Background (2013 Mar 25)
Posted: Tue Mar 26, 2013 11:39 pm
by Anthony Barreiro
Chris Peterson wrote:
bls0326 wrote:Why the egg-shaped universe picture? Is the universe really that way or is this just a representation of a 3 dimensional sphere in 2 dimensions?
The data represents the 2D surface of a sphere, not the 3D volume. We are seeing the projection of a spherical surface onto a plane. This map uses a Mollweide projection because it preserves area proportions.
This map is a composite image of the whole sky in a way that you could never see it in actuality. The equator of the map is the circumference of the Milky Way as seen in the sky. The poles are the north and south galactic poles in the constellations Coma Berenices and Sculptor. The center of the map is the center of the galaxy in the constellation Sagittarius.
The cosmic microwave background radiation is mapped onto the coordinates of our galaxy because our galaxy emits a lot of microwave radiation. The "local" microwave radiation from our galaxy needs to be subtracted from the total microwave radiation detected to yield the true value of the cosmic microwave background radiation.
Re: APOD: Planck Maps the Microwave Background (2013 Mar 25)
Posted: Wed Mar 27, 2013 2:52 am
by tardigradess
why is the microwave back ground map egg shape and not triangular or hexagon or rectangular or a circle or a random dynamic amoeba shape?
Re: APOD: Planck Maps the Microwave Background (2013 Mar 25)
Posted: Wed Mar 27, 2013 5:19 am
by geckzilla
tardigradess wrote:why is the microwave back ground map egg shape and not triangular or hexagon or rectangular or a circle or a random dynamic amoeba shape?
Seems to be a good way to map a sphere onto a 2d surface. You could make it a rectangle like a map of the earth but then the poles get pretty distorted.
Re: APOD: Planck Maps the Microwave Background (2013 Mar 25)
Posted: Wed Mar 27, 2013 5:21 am
by geckzilla
Anthony Barreiro wrote:I have enough trouble understanding one universe. It seems like asking for trouble to speculate about a multitude of other universes that we will never see. My own personal belief is that we will never know everything, our theories and models will always be imperfect, and even this one universe will always be bigger, more complex, and more mysterious than we can possibly understand. Still, there is great value in striving for greater knowledge and understanding. And to have a better map of the universe 380,000 years after the big bang than we had a few years ago is an impressive accomplishment.
I go through moments of existential confusion every time I think about this because anytime one of us takes it into consideration we are actually the universe thinking about itself.
Re: APOD: Planck Maps the Microwave Background (2013 Mar 25)
Posted: Wed Mar 27, 2013 5:50 am
by Ann
Man (or woman): I think, therefore I am.
Universe: An inconceivably tiny and fleeting part of me is thinking of itself, thereby conveying existence upon me.
Universe: On second thought... I think I will keep on existing even after that fleeting microparticle of mine has ceased functioning. But it's nice that someone is thinking about me.
Ann
Re: APOD: Planck Maps the Microwave Background (2013 Mar 25)
Posted: Wed Mar 27, 2013 6:06 am
by geckzilla
Hey, you never know how many inconceivably tiny and fleeting parts of the universe is thinking about itself. Could be a lot.
Re: APOD: Planck Maps the Microwave Background (2013 Mar 25)
Posted: Wed Mar 27, 2013 12:21 pm
by stephen63
geckzilla wrote:Hey, you never know how many inconceivably tiny and fleeting parts of the universe is thinking about itself. Could be a lot.
And wondering if they are the only one.
Re: APOD: Planck Maps the Microwave Background (2013 Mar 25)
Posted: Wed Mar 27, 2013 1:42 pm
by neufer
Click to play embedded YouTube video.
stephen63 wrote:
geckzilla wrote:
Hey, you never know how many inconceivably tiny and fleeting parts of the universe is thinking about itself. Could be a lot.
And wondering if they are the only one.
Re: APOD: Planck Maps the Microwave Background (2013 Mar 25)
Posted: Wed Mar 27, 2013 2:06 pm
by Chris Peterson
geckzilla wrote:Seems to be a good way to map a sphere onto a 2d surface. You could make it a rectangle like a map of the earth but then the poles get pretty distorted.
All projections of spherical surfaces onto a plane necessarily introduce distortions of one kind or another. As I noted above, this particular projection was chosen because it preserves the size of local areas- important where the interest is in examining structure and homogeneity.
Re: APOD: Planck Maps the Microwave Background (2013 Mar 25)
Posted: Wed Mar 27, 2013 7:42 pm
by Case
slashdot.org wrote:Damien George, of Cambridge University, has created a 3D visualization of the latest data from the Planck mission. Using WebGL, it lets you spin and zoom a 3D model of the Cosmic Microwave Background, and select different wavelength bands.
Re: APOD: Planck Maps the Microwave Background (2013 Mar 25)
Posted: Fri Mar 29, 2013 1:04 am
by bls0326
Nice 3D visualization. really looks like random fluctuations, but looks can be deceiving.
Re: APOD: Planck Maps the Microwave Background (2013 Mar 25)
Posted: Fri Mar 29, 2013 7:11 pm
by neufer
Click to play embedded YouTube video.
bls0326 wrote:
Nice 3D visualization.
really looks like random fluctuations,
but looks can be deceiving.
If it were random then the power spectra would be flat
(There is an excess of structure at ~ 1º angular sizes.)
Re: APOD: Planck Maps the Microwave Background (2013 Mar 25)
Posted: Sat Mar 30, 2013 3:51 pm
by bls0326
Art: thanks for the power spectra input. Unfortunately I am just an interested retired civilian. I have a little math background but too long ago. I'll need to do some research on your clips and comments for it to mean much to me. Something new to work on, at least for me.
My own personal belief is that we will never know everything, our theories and models will always be imperfect, and even this one universe will always be bigger, more complex, and more mysterious than we can possibly understand. Still, there is great value in striving for greater knowledge and understanding. And to have a better map of the universe 380,000 years after the big bang than we had a few years ago is an impressive accomplishment.
