Expert: Philip Stahl - 12/8/2008

Question
Don't want this to sound silly, but if we are viewing galaxies that light has just reached us, back in time idea, say billions of years. How do we know we are not looking at our own galaxy? Or can we plot where they would be now, dec 7th, in relationship to the billions of years ago telescope view.

Answer
Hello,

First, the cosmos is not like some giant mirror. Merely because we are looking back in time (or at great distances) doesn't mean any objects are being "reflected back" to us including our own galaxy. However, it IS possible for positions of distant galaxies to be slightly deflected by virtue of the "gravitational lens" effect from general relativity. Feel free to google this.

Second, in order for such to be the case, the cosmos would have to possess much more extreme curvature than it does. In fact, from recent data we have obtained from diverse sources, the cosmos is nearly "flat" (Euclidean 4-D flat space).

One of the most distant galaxies is referenced via the link below.


http://news.nationalgeographic.com/news/2008/02/080213-AP-galaxy-pin.html

Most certainly this is not the Milky Way! (Or indeed any neighboring galaxy!)

Re: galaxy maps & plots, there has been an ongoing effort to plot galactic maps via the Wilkinson Microwave Anisotropy Project.

You can read more here:

http://map.gsfc.nasa.gov/mission/observatory_freq.html

Clearly - this is an ongoing work and seriously, can't be done properly until and unless humans can attain more diverse perspectives which are only available via space travel (probably at least interstellar, but better, intergalactic). So I would not hold my breath overly long awaiting a superior, all-encompassing map that could be relied upon to give all positions of all distant objects faithfully!