# The Naked Scientists Forum

### Author Topic: How come the CBR Map is an ellipse and not a circle?  (Read 1580 times)

#### Nizzle

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##### How come the CBR Map is an ellipse and not a circle?
« on: 03/09/2009 07:07:13 »
Look here for the WMAP of 2008 of the Cosmic Background Radiation.

I've always wondered why the image is elliptic and not circular.
And how should i interpret this 2D representation of the 3D universe? (an image is a snapshot, so let's forget about the 4th Dimension for now)

#### Vern

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##### How come the CBR Map is an ellipse and not a circle?
« Reply #1 on: 03/09/2009 13:57:50 »
I suspect that the ellipse is just the shape chosen by the creator of the map. The colours are exaggerated; probably to enhance the very slight differences in the CMBR frequency to illustrate some point.

#### lightarrow

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##### How come the CBR Map is an ellipse and not a circle?
« Reply #2 on: 03/09/2009 14:42:04 »
Look here for the WMAP of 2008 of the Cosmic Background Radiation.

I've always wondered why the image is elliptic and not circular.
And how should i interpret this 2D representation of the 3D universe? (an image is a snapshot, so let's forget about the 4th Dimension for now)
The elliptical is just a kind of geographic chart, like this:
http://en.wikipedia.org/wiki/File:AYool_topography_15min.png
these kinds are elliptical because the chart is made "unrolling" the real spherical surface along the major axis of the ellipse.
About the 2D, of course you don't know what happens in the 3 dimensions, you only know what you measure here on Earth (to know which is the CMBR 1 light year from us, for example, you should go there to measure it); clearly they make assumptions on its homogeneity.
« Last Edit: 03/09/2009 14:44:12 by lightarrow »

#### PhysBang

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##### How come the CBR Map is an ellipse and not a circle?
« Reply #3 on: 03/09/2009 15:03:59 »
The CMB is 2d. We are seeing the surface of a sphere (approximately) around us.

#### The Naked Scientists Forum

##### How come the CBR Map is an ellipse and not a circle?
« Reply #3 on: 03/09/2009 15:03:59 »