How Far Back in Time Can We See?

By independent blogger/journalist Robert Platt

The sun's light takes about eight minutes to reach Earth. Therefore, in a hypothetical situation, if the sun was to explode, we would see the sun in perfect form until eight minutes has passed. Then we would see the explosion as the light from the sun finally reaches Earth. Hence, many experts point out we as a human race would actually be looking into the past in the interim that it takes for light of the sun’s explosion to reach us. Actually, according to Einstein’s theory of relativity, we are constantly peering into the past when we see the sun. So you see TIME also has physical properties. Time is only as fast as light, and if one could exceed the speed of light, you would likewise travel back in time.

That light takes so long to reach our planet means when one looks up into the night sky, the millions of twinkling stars that we see, which are billions if not tens of billions of light years away, are actually millions of years in the past. This means that we are actually looking at our universe as it was, and not as it is (depending on exactly what you define by ‘was’ and ‘is’, of course, which can also be said to be relative). So theoretically the universe could be being ripped apart by monstrous supermassive black holes gone MAD, but as long as it is not occurring in our conscious time bubble (the third dimension), it is undetectable and we would have no idea. That is, unless we somehow found a way to travel at light speed and actually arrived at some distant point in the universe in our third dimensional conception of time, but even then it would only be visible to those who have travelled there (and if you're not confused, these friends would now have travelled to some time in our third dimensional "past"). We, here on Earth, would not even be able to observe our space-travelling friends in telescopes because it would still take millions of years for "now" in the distant universe to reach "now" here on Earth. Even a "live" televisual conversation would be taking place in our space-travelling friends' past, because it would take that long for radio frequency or even ultra-high frequency (VHF) to reach our planet. This is why it can take up to 20 minutes for signals to reach Earth from the Mars rovers.

Mind-boggling, isn't it?

And so, the further the distance between objects and our relative position - in this scenario Earth - the longer it takes for the light to reach us and, subsequently, the further back in time we are looking. While it takes eight minutes for the hypothetical sun explosion to reach our earthly views, it could take many times that amount for a hypothetical explosion of a terrestrial body to reach our realm of vision. Consequently, we are looking deeper and deeper into the past the further and further we look into space. The more distant the object in space from our relative position, the deeper in the past this picture in the way it appears to us has occurred.

Tie this to recent headlines that ESO’s Very Large Telescope has discovered the most distant known object in the universe (a redshift of 8.2). The explosion, a faint gama-ray burst, occurred 13 billion years ago, which is only 600 million years after the Big Bang.

A thought occurred to me whilst reading this news: If we continue to build more powerful telescopes that can look even deeper into the universe, we would inevitably build something that could detect a terrestrial object that would go back to exactly the time of the Big Bang. But then what? Is that where the universe stops? What is the end of the universe like? And if we could go past the Big Bang, which, supposedly, marked the creation of time itself, we would be in an entirely new dimension (if "dimension" is the right terminology, because "dimension" would presume the existence of physical properties). The implications of such a device (which hopefully will be built in the not-too-distant "future") would be tremendous in regards to our understanding of the way things came to be.