Could Aliens 65 Million Light Years Away from Earth See Dinosaurs Alive?


We don’t usually think about aliens when
we think about dinosaurs, but someone by the name of Dr. Matt Caplan recently asked a very
fascinating question about these two subjects. In his search for an answer, he was forced
to delve into topics such as light speed, black holes, and telescopes. Join him in his exploration, in this episode
of the Infographics Show, Could aliens 65 million light years away from earth see dinosaurs
alive? Don’t forget to subscribe and click the
bell button so that you can be part of our Notification Squad. In theory, the answer is yes. Light that left earth 65 million years ago
is now 65 million light years away, so if aliens knew where to point their telescope,
they could see dinosaurs. But is it possible for anyone, even a super-technologically-advanced
alien, to build a telescope powerful enough? Let’s see… Light takes time to travel, so looking at
anything is equivalent to looking back in time. And the farther away it is, the further back
in time you see. For example, if your eyes are about 2 feet
away from the screen you’re watching this video on, then you’re seeing this video
as it was about 2 nanoseconds earlier. That’s basically instantaneous, and way
faster than the human reaction time, so the light-speed delay doesn’t muck up our daily
lives. But if you look at the moon, the light left
it about a second ago, long enough for there to be noticeable pauses in communication with
Apollo astronauts. For the sun, it’s closer to 8 minutes, so
if for some crazy reason the sun disappeared, then no one on earth would know it for 8 minutes. When astronomers look through their telescopes
at distant stars, they’re seeing them as they were many years ago. Coincidentally, this is one way astronomers
measure distance – a light year is just the distance it takes light to travel in a year,
conveniently tying distance and age into one number. So again, in theory, the light that left the
earth millions of years ago is now millions of light years away, and in that light is
a glimpse of dinosaurs. Since the dinosaurs went extinct 65 million
years ago, then the closest alien that could see dinosaurs, if he knew where to point his
telescope, is 65 million light years away. But in practice, it’s much harder, because
the earth is small and 65 million light years is a long distance. For perspective, the vast majority of the
visible stars in the night sky are within about 1,000 light years of us. The Milky Way is about 100,000 light years
across. The nearest galaxy, Andromeda, is about 2.5
million light years away. At 65 million light years, our alien astronomers
would be in the far-off Virgo Cluster of galaxies. So if these aliens want to see dinosaurs,
they’re going to need a big telescope. Human astronomers can only barely resolve
nearby planets in our own galaxy, let alone extragalactic planets. In fact, only a handful of observations have
been reported of extragalactic exoplanets. One is in Andromeda, and the other is cheating
– it’s only 2,000 light years from earth because it was acquired by the Milky Way in
a galactic merger. So how do telescopes allow us, or aliens,
to see across the universe? Consider an analogy. Imagine the sun is constantly casting an enormous
barrage of little tiny bouncy balls in all directions. These balls are photons, or individual particles
of light. On earth, some will bounce off of a T-Rex
and then get caught in your eye, so your brain will be able to register, “Oh, that’s
a T-Rex! I’m going to die!” The farther you are from the T-Rex, the fewer
balls make it to your eye, and so the harder it is to see the T-Rex. Some other balls will hit the T-Rex and bounce
up and off into space to travel the universe. Telescopes use lenses and mirrors to refocus
a bunch of these space-balls over a wide area to a small collector, so that we can get the
benefit of a really big eye. And the farther you want to see, the bigger
an eye you need. So how big does an alien telescope need to
be? Fundamentally, a given lens can only focus
light so well due to quantum properties of light. No matter how superintelligent these aliens
are, they can’t cheat fundamental physics. Using what we know about the resolution limits
of man-made lenses, physicists can calculate that a lens would need to be over 36 million
miles across, which is about a third of the distance to the sun. This lens would fill up about half of Mercury’s
orbit, and it would only give the aliens a view of the earth as one pixel. And if that wasn’t impossibly huge enough
already, these aliens wanted to see dinosaurs, not just the earth. If you want to resolve a dinosaur, even as
just a dot, then the telescope lens needs to be much bigger, 4.4 light years across. Such a telescope would fit comfortably between
our sun and the nearest star system, Alpha Centauri. Human astronomers often give their telescopes
hilarious names, like the “Very Large Array,” and “The Overwhelmingly Large Telescope,”
but somehow, these just feel inadequate. We don’t have to sit around and debate whether
or not an alien can build a telescope this big – Einstein’s theory of relativity actually
gives us the answer. General relativity tells us that matter curves
spacetime, and the more mass you have, the more it curves space. If you put enough mass in one spot, the spacetime
curvature will be so extreme that it must collapse on itself, forming a black hole. In fact, a ball of glass 28 light minutes
across will have enough concentrated mass to collapse into a black hole. So yes, in theory, the view of a dinosaur
is out there in space, but sadly, no aliens will ever get a glimpse of them. The script for this video was written by Dr.
Matt Caplan and adapted from a post on his website QuarksAndCoffee.com. Do you have any thoughts about his premise? Let us know in the comments! And if you liked this video, be sure to check
out our other video Could We Travel to TRAPPIST-1. Thanks for watching, and, as always, don’t
forget to like, share, and subscribe. See you next time!

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