Question: what is the furthest a camera can see into space

Tim Duckenfield answered on 5 Mar 2018:

This is a great question! As it turns out, because our cameras are so good (and if the object we look at is big and bright enough), the key limit to how far we can see is less about distance, and more about time. The furthest objects we can see in the sky are also the oldest, because the further away something is, the longer it takes the light to reach us. This blows my mind – when you see a star in the sky you are actually looking at that star as it was years and years ago, but it may not exist any more! We measure distance in space in light-years so 1 light year is how far light travels in one year (which is about 5.88 trillion miles!) If you see a star 100 light years away shining happily right now, you’re actually seeing how it looked 100 years ago. It may have exploded by now – but you’d have to wait 100 years to find out!

Now to return to the question, how far we can see? Well the universe is about 13.8 BILLION years old, so the furthest we could even hope to see is 13.8 billion light years away… but it does get more complicated. The universe is thought to be stretching, as though we were stood on a rubber band that is getting pulled apart. What we measured as 1 light year before the universe started expanding might be longer now. So depending on this expansion, we might ‘see’ further. However scientists haven’t agreed how stretched the universe is, so we aren’t quite sure. This stretching also changes the colour of what the camera sees, called ‘redshifting’ because light that starts green stretches into red. And finally, Einstein tells us that space is ‘curved’ so perhaps our universe is like standing on a ball. You can’t see the other side of the ball, only as far as the ‘horizon’, which is what we call the limit of what we can see on the Earth due to it being round. Perhaps there is a ‘cosmological horizon’ for our universe?