Originally featured on Quora, this query delves into the intriguing concept proposed by scientists: the notion that extraterrestrial beings, positioned 65 million light years away, equipped with powerful telescopes, might witness the era of "dinosaurs" on Earth. Let's unravel the mystery.
Answer by Corey Powell, Book author and science editor at Aeon, Former editor in chief of Discover, on Quora:
The crux of this question revolves around the captivating phenomenon of look-back times, a consequence of the finite speed of light. As we gaze into the night sky, we are essentially peering into the past. A stellar example is Sirius, situated 8.6 light years away. The light we perceive tonight commenced its journey 8.6 years ago. Extending this principle to more distant entities amplifies the temporal shift.
Consider the stars of the Big Dipper, spanning 60 to 125 light years away. When observing Dubhe, the foremost star in the Dipper's "bowl," the light we witness predates our own existence.
An engaging exercise involves identifying your birth star among the brightest stars. By ranking them based on distance, the chosen star represents the age of its visible light — your birth star takes you back to the time of your own birth.
Now, introduce the Andromeda Galaxy, visible to the naked eye and 2.5 million light years distant. The light currently reaching us commenced its odyssey 2.5 million years ago, revealing the galaxy's state when modern humans were nonexistent.
Transitioning to galaxy NGC 4845, residing 65 million light years away, we observe it as it was 65 million years ago, coinciding with the extinction of the T. rex. Importantly, the reciprocal holds true: intelligent beings in NGC 4845, beholding the Milky Way, witness our galaxy as it existed during the age of dinosaurs. Theoretically, they might catch a glimpse of our planet during that epoch.
However, a substantial caveat arises. Perceiving the Milky Way from the era of dinosaurs does not equate to discerning individual dinosaurs. Current technology, even with the most audacious theoretical advancements, cannot resolve details on distant planets, let alone creatures smaller than planets. NGC 4845's vast distance compounds the challenge, rendering the prospect of seeing dinosaurs an insurmountable feat.
In essence, astronomers from another galaxy could witness our cosmic neighborhood as it appeared during the dinosaur era. Nevertheless, glimpsing actual dinosaurs necessitates a technological prowess far surpassing current human comprehension. The extreme distance diminishes the photon count, rendering the resurrection of detailed images, like a T. rex succumbing to an asteroid, implausible.
In conclusion: Yes, extragalactic astronomers could witness our region of space from the time of dinosaurs. No, visualizing dinosaurs demands technology currently beyond our grasp.
