BRAINDUMP
How far can we see into the past through a telescope?
Our ability to treat the universe like a great cosmic time machine is due to the limited speed of light – even though it’s the fastest thing in the cosmos it can still only travel at 5.9 trillion miles per year, so all the light from distant objects that we are seeing now set out on its journey at some time in the past.
Even with the naked eye, you should be able to spot the Andromeda Galaxy, one of our closest galactic neighbours, which is equivalent to looking about 2.5 million years back in time. A small telescope will reveal galaxies tens of millions of light years away – light from some of the galaxies in the Virgo
Cluster set out on its way to Earth around the time the dinosaurs became extinct. The most distant galaxy seen with the Hubble Space Telescope, GN-z11, is 13.4 billion light years away, so we are seeing back to a time just 400 million years after the Big Bang. The James Webb Space Telescope went further with its recent discovery of the galaxy JADES-GS-z14-0, seen just 300 years after the Big Bang. And radio telescopes can do even better than that, detecting weak microwaves from the afterglow of the Big Bang itself, some 13.7 billion years ago.