Could Aliens 65 million light years away possibly see dinosaurs on the Earth? Well, theoretically yes. The last known species of dinosaur became extinct approximately 65 million years ago. So the light that left the earth back then is now 65 million light years away.
With directing a huge telescope at the right direction (towards the Earth) aliens might be able to witness dinosaurs. But how large the telescope should be to capture anything from that distance? Let’s try to answer it step by step.
The speed of Light
The speed of light is 299,792,458 m/s or approximately 300,000 km/s. Whatever we see in our surroundings are visible only because it reflects light, that’s the general optics. Now, presuming that you are reading this article on your tablets or computers at a distance of 2 feet, then you are actually seeing this word as it was 2 nanoseconds (one nanosecond is one billionth of a second) earlier.
If we talk about the moon, the light from it takes a whole 1 seconds to reach us, that means the moon we are seeing is 1 second old. The differences became more staggering in the case of the Sun. Situated at a distance of 149.6 million km from the Earth, light from the Sun takes nearly 8 minutes to reach here.
This is completely out of the topic, but if the Sun somehow disappears due to some weird reason, here at the Earth, we will not be able to sense it for the next 8 minutes.
Our point here is that looking at anything is technically looking that object what is was in the past, and it is directly proportional to the time, i.e., the further away it is, the further back in time you see. In the same fashion, the light that left the earth millions of years ago is now millions of light years away, and in that light is information of dinosaurs.
So is it Practical?
So far we have discussed the theoretical possibility of the subject matter. But is it really practical? The answer is no. The universe in vast. Precise astronomical calculations revealed that the Milky Way is alone 100,000 light years across and out there are million more which are way larger than our’s. One such galaxy is the Andromeda, which also happens to the nearest galaxy to the Milky Way at about 2.5 million light years away.
At about 65 million light years, our fellow alien astronomers would somewhere be in one of the galaxies in the Virgo galaxy cluster. For them to look back at the Earth, they need a real bad ass telescope. We will talk about exactly how large the telescope should be in a moment.
Before going any further, let’s first understand the basic principle on which every telescope works. Photons are the elementary particle of the electromagnetic field or simply light. Let’s imagine that the Sun harbors countless numbers of tiny bounce balls and it’s continuously releasing those tiny balls in all directions. These are photons which we are talking about.
We can see most of the things in our surroundings because of these photons. The further you are less and less of these tiny balls your eye will be able to catch. Space telescopes make distant observations by capturing a bunch of these photons or ‘space-balls’ and project it to a smaller collector, so basically the larger the telescope, farther we can see.
Back to the question, how huge the telescope should be that can enable aliens to observe dinosaurs and not just the planet Earth. So let’s find the diameter of the lens that they will need. To do that, we can use the formula for the angular resolution.
Angular resolution = 1.22 × Wavelength / Diameter of Lens
Solving the equation by putting the values in place give us a lens diameter of (5.8×1010) that is nearly the half of the distance from Sun to planet Mercury. And it will only let them see the Earth as one dot, just one dot.
To see dinosaurs even just as a dot on the surface of the Earth, they will have to build a truly monstrous lens with a diameter of 4.4 light years, that is the distance between Alpha Centauri and our Sun.
Here, we have just used the same equation, but this time putting different numbers. Instead of Earth’s diameter, we have to use the length of the dinosaur. Since Triceratops was about 9 meters, and T-Rex was about 14 meters, we used 10 meters as a median and for an easy math. Back on Earth, even with the help of modern technology, we can barely detect planets in our own galaxy, let alone a planet from a distant galaxy.
Well, we do not argue anymore that the construction of a telescope this huge is even possible or not. Einstein’s theory of relativity explains us how matter curves the spacetime – more the mass, more it will curve the space fabric.
When enough mass is accumulated in one spot, the spacetime bending will be so intense it will eventually transform into a black hole. A glass telescope with a diameter of 4.4 light-years is a far fetched, even a circular glass 14 light minutes in radius will have mass dense enough to collapse into a black hole.
So here we are, yes, aliens at a certain distance from the Earth can theoretically see the dinosaurs that existed 64 million years ago, but sadly or maybe luckily they cannot possibly acquire any means to do it.