Just listened to the BBC Inside Science podcast episode on The James Webb telescope.
The thing is chuffing incredible, but one fact about it actually blows my mind. Ok, you use the fact EM radiation has a fixed speed (that being ‘c’) to essentially see back in time - if you detect a star 1000 light years away, you’re seeing what that star was like 1000 years ago.
James Webb can see so far away, and detect such small amounts of light, that it can essentially detect the light from the very first stars. After the Big Bang, everything was essentially particle soup, and eventually that soup formed into clouds of hydrogen and helium and those clouds got more and more dense due to gravity which caused them to heat up and eventually - we think maybe about 500 million years after the big bang - the heat got to the point where nuclear fusion could happen, and the first stars came into being.
James Webb can see the light emitted from those stars. It can see right back to the very dawn of the macro scale physical universe.
But that’s not the mind blowing bit - the mind blowing bit is this is as far back as we’ll ever be able to see. It doesn’t matter how powerful a telescope we can build, or how faint light we can detect because before the point where James Webb can see to, there just isn’t anything to see. There are literally just dark, silent clouds of hydrogen, emitting nothing.
James Webb is not only the best telescope we’ve ever built, it’s the best telescope we’re ever going to need to build.
