Innocent me (stop laughing, Kev) decided to read an article on Hubble (“Is Hubble Worth the Upgrade Mission’s Risk and Cost?“) over on LiveScience. There’s a bunch of links down at the bottom of the article (below the poll) and one of them linked to a Science.com article “Why the Universe is All History” which deals with the light/time issue that I brought up earlier.
This article discusses the issue well, although it still hurt some to read it then try to grasp the concepts. The first bit of the article is what caused a big AHA! moment for me. I bolded the section that I like the most.
It took 300 years of experiment and calculation to pin down the speed at which light travels in a vacuum: an impressive 186,282 miles per second.
Light will travel slightly slower than this through air, and some wild experiments have actually slowed light to a crawl and seemingly made it go backward, but at the scales encountered in our everyday lives, light is so fast that we perceive our surroundings in real time.
Look up into the night sky and this illusion begins to falter.
Cool. So because the light here is slower (in galactic terms) what we see right now is in real time. The article continues by saying the moon’s (reflected) light is 1.2 seconds old when we see it. When we look at the closest star system (Proxima Centauri), the light from it that we perceive is 4 years old.
Where I went lost earlier is that in bringing Proxima Centauri closer via the telescope, we aren’t necessarily looking at its 3 yr old light vs the 4. The “age” of the light hasn’t changed because we’ve not moved. The telescope lens only brings that perceived light into better focus. No matter how big a telescope we make, we’ll only ever see 4 yr old light from that star system.
What is happening with bigger telescopes–and the telescopes in space–we are seeing further away and therefore, seeing further back into time. We can now see galaxies that are so far away, their light is billions of years old. We’ve not moved toward it, only been able to bring space into better focus. And that focus is getting better and better.