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Hubble vs. Webb - How Far Back Will They See?
Roland Piquepaille writes "According to Forbes, reporting in "Peering Back At The Universe's Past," space telescopes are really acting as time machines. They can watch objects which are so far from us that light has taken billions of years before reaching their mirrors. The Hubble telescope is able to look at events that took place 13.3 billion light-years ago. But the James E. Webb space telescope, currently under construction, and scheduled to be launched in 2011, will be able to see even further and catch phenomena which happened 13.5 billion light-years ago. The astronomers think the Webb telescope might even be able to see up to 13.7 billion light-years ago, when our universe was just 200 or 300 million years old. We are used to see fantastic images from Hubble, without paying too much attention to the characteristics of the telescope itself. So here is a thorough comparison between the two space telescopes."
I think the imagery provided by Hubble to date has been phenominal and expect that imagery from Webb will just as good or better. Looking back that far in the past though is just that ... the past. When we look back and see light that is 13.3, 13.5, or 13.7, or whatever billions of years old, it is exciting and adds more to the knowledge base. However, when I see galaxies that old I can't help wonder if they're still there (probably not) and what has taken their place. What's there now ...
well, if hubble could actually see as far as (light speed * age of the universe) light years than we could gain new knowledge about the big bang theory and the creation of the universe.
as it is, knowing what the universe looked like at age 300Million is quite nice by itself and simply saying that it "ain't nuttin' new" is quite ignorant!
as the light has traveled millions of light years, we ARE actually seeing something that existed millions of years before our time and thus you could call it some kind of "looking into the past"!
isn't the speed of light not actually a constant but changing with the expansion of the universe
Short answer no, longer answer we don't know. Pretty much all of modern physics is built off the idea that the speed of light is a constant. If you start changing the speed of light then all sorts of thing "break" like conservation of energy. So if you can change the speed of light, you could create matter out of nothing. Neat trick if you could pull it off. That said changing the speed of light does solve some nasty problems surrounding the big bang.
There's also the question that if the speed of light was changing if we'd even have any way of noticing because everything would be skewed along with it. Fun stuff.
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You know... I've actually given this some thought before...
Say someday we managed to put out a large mirror...say... X number of lightyears from Earth, where X was half the number of years you wanted to be able to look into Earth's history. Here's what I'm curious about:
1.) Assuming you could get the mirror out there and set up at light speed, it would make sense that the first image of the Earth we would get back was of the craft toting the mirror leaving Earth...well, actually, probably not, since it would logically take some pre-lightspeed travel first. But you get my drift.
2.) Assuming FTL travel, could you actually see into a point in time before the point the mirror left Earth?
3.) What size mirror would be needed for a telescope to be able to capture a reflected image? Would it even be possible? Perhaps with refraction from other celestial bodies (like they've done to enhance Hubble's distance viewing).
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