How far into space can we see ?

Light has velocity, this means that light travels around at a certain speed and this speed depends on the medium but roughly speaking it is 300 million meters per second. This is so incredibly fast that it appears instantaneously, when you switch on a lamp there is no observable delay in seeing the light that is because of how fast light travels. The delay of seeing light is only really appreciable on astronomic scales, and by this I mean only light coming from space is noticeably delayed, for example it takes the light from the sun 8 minutes to reach Earth.

This leads to a really cool result, when we look out into space we also look back into history. A light-year is a measurement of distance, it is the distance that light takes 1 year to travel, so if we have a star that is a 1 light year away, we can say that what we are looking at is the light that left that star a year ago. Through this idea when we start to look at further and further objects we look more and more into the past.

The furthest galaxy we have ever seen which is also the oldest galaxy we have ever seen is 13.5 billion light years away [1]. The Big Bang which is the beginning of the Universe happened 13.8 billion years ago, this means we observed light that was emitted only 300million years after the Universe was formed.

Amazingly we can see the remnants of the Big Bang, the Cosmic Microwave Radiation, this is detectable and is 13.8 billion years old, marking the edge of our observable Universe. 13.8 billion years ago the Universe was opaque to light, imagine a fog, so we can’t see further than this currently.

However there are neutrinos and gravitationally waves from a further distance that we may soon be able to detect expanding our horizons.

[1] https://cosmosmagazine.com/space/furthest-galaxy-james-webb/#:~:text=The%20James%20Webb%20Space%20Telescope%20%28JWST%29%20has%20broken,oldest-known%20galaxy%20was%20discovered%20by%20Hubble%20in%20July.