NASA, Robert Williams, and the Hubble Deep Field Team (STScI)
Light and Distance in an Expanding Universe
https://theness.com/neurologicablog/light-and-distance-in-an-expanding-universe/
The universe has been expanding since the Big Bang, with matter becoming less dense and hot over time. However, the expansion of space-time itself also causes light to become less dense and its wavelength to expand, making distant objects appear fainter than they would due to distance alone. This means that measuring the distance to a distant object is complex, as light has to “catch up” with the object as it moves away with the expansion of space.
The “lookback time” – the time light has been travelling to reach us – is not the same as the current distance, which is much greater. Our visible universe corresponds to the age of the universe, with objects beyond 41 billion light years away being outside our visible range. As the universe expands, the percentage of the total universe that is visible will decrease, with estimates suggesting only about 1.5% is currently visible.