There’s a whole bandwagon of us out there who’ve seen the following meme. Or something similar.
And then there’s a whole lot who might have not.
I was blown away when my little brain first understood the possibility. Imagine you seeing, not on video, but live, a flesh tearing T-Rex wreaking havoc on land, while a pair of Pterosaurs prayed to the heavens that they had wings.
Yeah, just like in the Jurassic movies.
But just so that you know, the T-Rex and the Pterosaurs never belonged to the same dinosaur period. And it is a pity the Pterosaurs were not even dinosaurs.
But while we are at it, let us get into imagining what it would take for us to visit the dinosaurs back in time.
The reason we see objects is because light has bounced off that object and reached our eye. And a major portion of that bounced-off light has also sped out towards outer space. All through its journey from the Sun to, let’s say somewhere in space, these packets of light called photons have been bouncing off objects, dust particles, the water vapour in the clouds and have scattered on every collision.
Pretty much like the way the blobs scatter themselves in the following animation of a nuclear fission chain reaction.
Now, the farther the object from you is, the lesser the number of light particles your eye receives. Makes for a pretty undetailed and block like image on your retina.
You cannot make out whether that’s a ballroom with couples dancing on the ship. Or a lecture hall with sailors on their first lessons at sea.
That’s where resolution comes into play. Resolution, purely in the optical sense, simply means the ability of an imaging system to resolve detail in the object that is being imaged.
To capture detail, you need to capture the photons that have struck that ‘detail’ and focus them on a screen. The purpose of focusing them is to get as many of those ‘detail’ carrying photons to come together at a localized place so that you obtain a sharper, clearer image of the ‘detail’.
Ever seen images of Jupiter in all its glory, or Saturn with its hula loop spinning away on a background of nothingness? Those images are taken by what the humans call an astronomical telescope. Just a fancy name for a combination of magnifying glasses. These combinations do the exact job of collecting and focusing large groups of photons from outer space onto a screen. The stuff that we spoke about earlier.
Now light from Jupiter is coming from somewhere around 628,743,036 km away. This is the distance between Earth and Jupiter when they are closest to each other on their Merry-go-rounds around the Sun.
Imagine the distance between the Earth and the Moon. Imagine 1635 times that distance. That’s where Jupiter is at its closest to the Earth.
This comparison might still not put things in perspective. So we’ll try another comparison.
Imagine the Moon to be a metre away from the Earth. That would be just a little more than an arm’s length away. At this scale the Earth is just about the size of a table tennis ball. And the moon is a shiny little colourful marble.
Jupiter is just around the corner. A balloon just big enough to fit your 16.3 inch screen laptop, bobbing in space at approximately 1.6 kilometres from earth. A table tennis sized earth, that is.
Now against the vast canvas of darkness, this huge planet Jupiter is nothing but a tiny detail that needs to be resolved by a telescope.
Now there’s a formula in optics that deals with angular resolution.
Angular resolution, in very simple terms, is nothing but the least angle by which two distinct objects should be away from each other, so that they are registered as two distinct objects by the lens.
I was inclined towards explaining the formula involved and the crazy technical terms that come with that, but thank your good Gods, I’ll choose to skip that messy part.
But we’ll still go into what that formula means for the practical purposes of creating a lens that has the ability to resolve any said object into a distinct clear ‘detail’ distinguishable from its surroundings.
By some little calculation of my own, I came to some interesting numbers.
If you had a lens to just resolve the marble (our Moon) that’s at a distance of 1 metre, that lens would fail terribly at trying to resolve the big balloon (our Jupiter) that’s a nice 1.6 kilometres from us.
You’d require a lens of at least 45 times the diameter to just resolve Jupiter. By just resolving I mean that we are simply making sure that we can differentiate the marble from its surroundings. Differentiating the colours within the marble is a whole different story.
Back to the dinosaurs. History records that they were swept clean from the face of the earth somewhere around 65 million years ago. That means the photons that had hit the T-Rex and its poor prey have been travelling for 65 million years now. Of course, colliding and scattering on impact with every super minute thing that came in its way. But once it got to outer space, it was on a biker’s paradise. A highway. It’s difficult to collide with nothingness. Now these photons that are travelling at the speed of light, literally, have traveled HUGE distances. I’m not even bothering to write the result of this equation:
Distance traveled by that photon we are after = Speed x Time = 3 x 108 metres/second x 65 x 106 x 365 x 24 x 60 x 60 seconds
Maybe Scientists didn’t want to write such huge numbers either. So, for the love of humanity, there’s a unit of distance called a light year, which is pretty much self-explanatory. A light year is the distance light travels in vacuum over a period of one year.
So our lighting fast photons are speeding outwards, some 65 million light years away. Our little minds can’t comprehend what a huge distance that is. But just so that you know, the Sun is about 499 light seconds away from us.
We’re in luck. We’ve calculated the distance we need to travel to catch that photon. Provided we travel that distance this instant. Not a second’s delay. You’d just give that photon a lead of 3 x 108 metres.
Alright, not gonna happen. At least not with the speed of our current spaceships.
But we so badly want to see the dinosaurs that were so ruthlessly wiped off by a disaster, thankfully not man-made.
How about having aliens waiting just around the 65 million light years mark and recording a 1080p clip for us. That’ll do.
Of course they’ll need to gather lens material to build a lens powerful enough to resolve the dinosaurs (or the photons that have their beloved memories).
Referring to an article that my friend Vijay pointed out to me, a lens to resolve the Earth 65 million light years away would require a diameter of 5.8 x 108 metres. Again, let’s not try to visualise that size.
Nope. We will. Cos it’s fun. That’s about 1 and a half times the distance between the Earth and the Moon. On our modified scale, that’s a lens of a diameter of 1.5 metres. Please recall that our Earth is just the size of a table tennis ball.
Anyways, that’s the aliens’ problem. We’ll get what we paid for. A ‘real’ dinosaur GIF.
But the aliens come back with a question. Is that just our Earth we want them to resolve, or do we want them to capture the ‘details’, the dinosaurs?
Our lens diameter would need to be a good 4.4 light years in diameter.
Let us not try to visualize this distance. Only for the sake that I may visualize this distance in another blog post.
But then, the aliens come back with another problem. I really should move on to the next blog post.
Our mission to watch the dinosaurs remains unaccomplished. Catch you after a popcorn break!
Information Courtesy: Google! The guy who thought it was a good idea to write this: Vijay The website that I was inspired by to write this: WaitButWhy Readers Courtesy: All of you!
Please fire questions of all sorts and curse me for anything that you find technically wrong. Also do let me know! There’s nothing like your beliefs being overturned by a fine eye!
Do note that I have made every sincere attempt to keep things as simple and technically correct as my little mind could comprehend. That said, get back to the start of this para.
Revel in Science!