Would advanced civilizations be aware of humanity’s existence?

As we float amidst the vast expanse of the cosmos, it’s kinda tough to believe we’re the only ones here, right? When you gaze up at the night sky, it’s almost impossible not to ponder the chance of other civilizations cruising out there. The more we’ve delved into the cosmos, the more it feels like there might just be some extraterrestrial buddies out there. But, despite all our efforts to connect, the universe seems to be giving us radio silence.

Sure, there’s a chance we’re cosmic loners, or maybe other space folks are just really good at staying incognito, using tech we can’t even see. But, you see, we’re all about that radio life – it’s like our go-to tool for chatting across the cosmos, and it doesn’t break the bank. We’ve been blasting radio signals from Earth for ages, so it kinda makes you wonder, why wouldn’t other civilizations be rocking the radio wave too?

Are humanity’s signals reaching them?

Some folks think we might be a tad too hopeful about this. You see, we’re constantly sending out radio signals, but here’s the thing: the strength of those radio waves weakens the farther they travel, kind of like a fading flashlight beam in all directions. Plus, space itself isn’t exactly a friendly environment – there’s dust and gas floating around that can mess with our signals. 

So, realistically, our radio messages are probably only audible within a few light years of Earth using the kind of radio gear we’ve got right now. Sure, we’ve sent out some powerful radio messages directly into space a few times, like that Arecibo message we shot toward the Hercules cluster back in ’74

Well, you know, we humans are pretty fresh on the cosmic scene and not all that fancy in the grand scheme of things. Now, imagine if there were some super ancient, super high-tech aliens out there – maybe they could sift through our messages hidden in all that space dust. But here’s the real kicker: could they do that trick from hundreds or even thousands of light-years away? That’s the big question that this new paper on arXiv takes a good, hard look at.

Also read: Is interstellar travel really possible or just a distant dream?

How far could these civilizations be?

So, the writer kicks things off by diving into something called the Kardashev scale, which is basically a way to size up how advanced a civilization is. This scale, which was first thrown out there back in 1964, measures civilizations based on how good they are at harnessing energy resources. 

Picture it like this: a Type I civilization can handle energy on a planetary level, a Type II can tackle energy on a whole star system scale, and a Type III is like a cosmic boss, dealing with energy on a galactic level. Now, folks like Carl Sagan and pals took this idea, and kind of turned it into a flexible sliding scale. They took a gander at where humans stand and pegged us at about 0.73 on this scale.

So, with that in mind, the author starts pondering a big question: What level on this scale would a civilization need to be in order to spot the leftovers of our human civilization, and how far away could they do this from?

Can other civilizations pick our signals?

So, since our radio signals can only travel about a hundred light-years before they start fading into nothingness, it’s more likely that another species would have a shot at picking up some of the cool stuff we’ve got going on here on Earth. We’re talking about things like entire cities or massive structures that we’ve built, like those iconic pyramids in Giza. Those ancient wonders have been standing tall for thousands of years, and just to give you an idea, the base of the Great Pyramid is roughly 230 meters wide.

Considering how much light makes its way to Earth, you wouldn’t be able to spot those pyramids from super far away, even if you had the fanciest telescope in the universe. There just wouldn’t be enough of those little light particles, or photons, reaching beyond a certain point to let you see anything clearly. 

If we’re talking about the middle of the visible light spectrum, which is around 550 nanometers, and you’re trying to resolve details as small as 10 meters, you’d max out at roughly 3,000 light-years as the farthest distance you could spot something like the pyramids.

So, if you want to see stuff the size of pyramids from that far away, you’d need a ginormous optical telescope, something with a diameter about as big as Saturn’s orbit around the Sun, which is roughly 10 astronomical units (AU). To make such a monster telescope, you’d have to dream up a massive array of millions of satellites spread out across Saturn’s orbit.

Also read: What makes dust swirl so quickly on the Moon without wind

A near-impossible task

But let’s be real here: that’s a colossal undertaking, way beyond what we or any civilization on a planetary scale could even dream of pulling off. To even think about building something like that, you’d have to be masters of your entire star system, no small feat!

So, bottom line, if we’re talking about a Type II civilization, they could potentially spot the awesome stuff we’ve built on Earth if they’re within about 3,000 light-years of us. So, there’s a chance they could figure out we’re here after all.

But, here’s the kicker: it’s gonna take us a few thousand years to level up to Type 2 status ourselves before we can start peeping back at them in the same way.