There is a way of actually looking in to the past. We do it every time we look up at the sky at night. The star light that you see now was released from stars many years ago. If you look up at the Sun (highly un-recommended) you are viewing the light that it released 8 minutes ago (i.e. it is 8 "light minutes" away from us). If you look at Alpha Centuri (highly recommended), our next nearest star (actually a ~ binary star system), you are seeing the light that it released ~ 4 years ago (i.e. it is 4 light years away).
This very cool, and somewhat disconcerting. Where the heck are we in time?! There are some stars (like Betelgeuse, a super red giant in the Orion constellation) that are at the end of their stellar life cycle (don't worry... still another ~100,000 years). Betelgeuse is ~ 700 light years away and is in it's last stage in 'life'. Therefore, even if it exploded 600 years ago we wouldn't know it for another 100 years; it takes time for that light to reach us. Being relatively near, a Betelgeuse supernova, would shine as bright as a quarter Moon and would rise to peak brightness over a couple of weeks and then fade...
So the question/s is/are: how far back can we see? I see the Sun now as it was 8 minutes ago, Alpha Centuri as it was 4 years ago and Betelgeuse as it was 700 years ago. If we take very powerful telescopes, can we see the light from ancient galaxies? The early forming of galaxies? Or the beginning of the universe itself...
Now suppose you hold up a window at arm's length the size of a grain of sand. Suppose that window is a powerful telescope. One of those powerful telescopes is the Hubble telescope and it's observations are staggering. Using high magnification and a long exposure the Hubble telescope spends a couple of weeks gathering light from a minuscule portion of the sky. The images captured peer across time at some 15,000 galaxies. The red-shift (resulting from the expanding universe) of some of those galaxies are such that the light from them was formed ~ 13 billion years ago. That is a mere 500 - 700 million years after the start of our universe! Answer to our initial question: We can see galaxies now that are literally 13 billion years old! And that's not akin to 'a human memory' (an interpretive mapping of our current being to a past experience), what you see in that Hubble image above, is (for all intents and purposes) an image of the past.
So although there are ~100,000 stars in our galaxy, the Hubble image shown above looks past the stars in our galaxy only showing (at my counting... correct me if I'm wrong!) about 10 individual stars, the rest of those different coloured dots (15,000 or so) are galaxies. WOW.
But there is an elephant in the room. How are there 15,000 galaxies in the Hubble image of a region of the sky that is the size of an image through a grain of sand at arms length?! Conclusion: There are a vast number of galaxies in our observable universe estimated at 200 billion to 2 trillion galaxies.
This should lead us to wonder, speculate, ponder, fascinate at, revere, be astonish at, be curious at, amazed, dumbfounded, flabbergasted, impressed and truly humbled by it all.
The ability to peer in to the past, is an important tool in understanding the early universe and how it evolved. It is images like this that show a snapshot of galaxies through a continuum of time that are stretching the boundaries of frontiers in cosmology.
The universe. Our living quarters. Home. In a cosmic sea, living on our pale blue dot.
The image above was released by NASA on 16.08.18 as part of the Hubble Ultra Deep Field project.
Another important early universe/Big Bang observation is the cosmic microwave background radiation, which detects the microwave remnants of energy released from the big bang. Stayed tuned, for another post on this soon (hopefully!).