Expert: Ed - 5/29/2011

Question
Hi Ed,
Curious about gravitational lensing. I've been wondering how we look into deep space and acquire "accurate" images at whatever distances. Are we not seeing such massively distorted images as to make our interpretation irrelevant? Basically, with so many massive objects altering space-time, how can we accurately view even the near universe? I'm sure you understand what I'm getting at, but to be clear; if looking in a straight line towards a star, with another in between the line of site, the one in between would curve the line of site slightly off, or at least slightly alter its "true" position, no? If that's true, how do we compensate? If not, please explain.

Answer
Anthony, wow, that is a great question.  I will do my best to answer it.

One of the first things that come to mind, that I think you might enjoy pondering, is Olbers' Paradox.  This poses the question of why the night sky is not very bright, as there should be stars in virtually all directions, as we look up at the night sky.  Are we not viewing the surface of a star, at some distance, at every imaginable angle as we look upwards?  Here are some NASA discussions of this question:

http://starchild.gsfc.nasa.gov/docs/StarChild/questions/question52.html
http://imagine.gsfc.nasa.gov/docs/ask_astro/answers/980815b.html

Your question touches on a similar topic, which is, the density of stars around us in the sky.  By that I mean, not how dense each star itself might be, but rather how many stars are there, for example, in a given cube of space, saaayyyyy ten light years on each side?

The answer seems to be that there aren't enough stars NEAR US, to have enough of an effect to produce the observational problems that you describe.  Perhaps, if there are intelligent beings on a planet revolving around a star near the center of our galaxy, where the stars are in much closer proximity to one another, then those intelligent beings would face the problem you describe.  Fortunately, we are pretty far out from the center of our galaxy, so space-time isn't THAT distorted right around us.

I hope this is helpful.  Keep Looking Up!
-Ed