Would We See the Aliens Coming?

Article written: 1 Jun , 2015
Updated: 27 Feb , 2017
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If aliens were heading towards the Earth, would we see them coming?

Classic sci fi trope time. The air force detects a fleet of alien spacecraft out past Jupiter, leaving enough time to panic and demonstrate what awful monsters we truly are before they come ring our bell.
Is that how this would work?

Imagine a pivotal scene in your favorite alien mega disaster movie. Like the one where the gigantic alien ships appear over London, Washington, Tokyo, and Paris and shoots its light-explody ray, obliterating a montage of iconic buildings. Demonstrating how our landmark construction technology is nothing against their superior firepower.

What could we do? We’re merely meat muppets with pitiful silicon based technology. How could we ever hope to detect these aliens with their stealth spacecraft and 3rd stage guild navigators? If we’re going to do this, I’m going to make up some rules. If you don’t like my rules, go get your own show and then you can have your own rules.

Alternately, as some of you are clearly aware, you can rail against the Guide To Space in the comments below. Dune reference notwithstanding, I’m going to assume that aliens live in our Universe and obey the laws of physics as we understand them. And I know you’re going to say, what if they use physics we haven’t discovered yet?

Then just pause this video and get that out of your system. You can make that your first decree against the state right in the comments below. As I was saying, physical aliens, physical universe. We’ll discuss the metaphysical aliens in a magic universe in a future video. The ones that have crystals and can heal your liver through the power of song.

A basic rule of the Universe is that you can’t go faster than the speed of light. So I’m going to have any aliens trying to attack us traveling at sublight speeds.

So, we’ll say they’ve got access to a giant mountain of power. They can afford to travel at 10% the speed of light, which means before they get to us, they have to slow down. At this speed, deceleration is expensive. We’d see the energy signature from their brakes long before they even reached Earth.

Let’s say they’re passing the orbit of the dwarf planet Pluto, which is 4 light-hours away. Since they’re travelling at 10% the speed of light, we’d have about 40 hours to scramble jet fighters, get those tanks out onto the streets and round up Will Smith, Jeff Goldblum and Bruce Willis to hide behind.

A composite image with Chandra data (purple) showing a "point-like source" beside the remains of a supernova, suggesting a companion star may have survived the explosion. Credit: X-ray: NASA/CXC/SAO/F.Seward et al; Optical: NOAO/CTIO/MCELS, DSS

A composite image with Chandra data (purple) showing a “point-like source” beside the remains of a supernova, suggesting a companion star may have survived the explosion. Credit: X-ray: NASA/CXC/SAO/F.Seward et al; Optical: NOAO/CTIO/MCELS, DSS

Would we even notice? Maybe, or maybe not. A growing trend in astronomy is scanning the sky on a regular basis, looking for changes. Changes like supernova explosions, asteroids and comets zipping past, and pulsating variable stars.

One of the most exciting new observatories under construction is the Large Synoptic Survey Telescope in Chile. Once it begins regular operations in 2022, this array of telescopes will photograph the entire sky in fairly high resolution every few nights.

Computers will process the torrent of data coming from the observatory and search for anything that changes. What if they engage their cloak?

Actually (push glasses up your nose) the laws of physics say that the aliens can’t hide the waste heat from whatever space drive they’re using. We’re actually pretty good at detecting heat with our infrared telescopes.

A space drive decelerating a city-sized alien spacecraft from a significant portion of the speed of light would shed a mountain of heat, and that’s all heat we might detect.

Astronomers have been searching for alien civilizations by looking for waste heat generated by Dyson spheres encapsulating entire stars or even all the stars in a galaxy. Nothing’s turned up yet. Which I for one, find a little suspicious.

Freemon Dyson theorized that eventually, a civilization would be able to build a megastructure around its star to capture all its energy. Credit: SentientDevelopments.com

Freemon Dyson theorized that eventually, a civilization would be able to build a megastructure around its star to capture all its energy. Credit: SentientDevelopments.com

If you’re from an alien race who’s planning to invade. Cover your ears. If aliens wanted to catch us off guard, they can use one of the oldest tricks in the aerial combat book, known as the Dicta Boelcke. They can fly at us using the Sun as camouflage. A rather large portion of the sky is completely obscured by that glowing ball of fiery plasma. It worked in WW1, and it’ll still work now.

Okay, aliens you can listen in again. Everyone else might want to mute the next part, as it’s not terribly reassuring. Astronomers often discover asteroids skimming by the Earth just after they’ve just gone past. That’s because they hurl at us from the Sun, just like clever aliens.

To spot those asteroids, we’ll need to deploy a space-based sky survey that can watch the heavens from a different perspective than Earth. Plans for this kind of mission are actually in the works.

Even with our rudimentary technology, we’d actually stand a pretty good chance of noticing the alien attack vessels before they actually arrived at centre of Sector 001. It’ll get better with automated observatories and space-based sky surveys.

Of course, there’s little we can do if we did know the aliens were coming. We’d be best to start with some kind of deterrent, contaminate all our fresh water, load our livestock up on antibiotics and cover our cities in toxic smog to deter the harvesting of our citizens.

Do you think we’d stand a chance against an alien invasion? Tell us how we’d do in the comments below.

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18 Responses

  1. Steven says

    I wonder if they could emit the waste hit in a targeted way in a cone around the habital zone of the Sun…. lol

    • Qev says

      Well, they’d have to be pointing their engines at us in order to slow down, so there’s not much redirecting that can be done there. 🙂

      As for our chances against an alien invasion, it would depend on the aliens’ goals and methods. If they wanted everything intact, we could probably make it very expensive for them. If they wanted us gone, period… well, it was nice knowing you, humanity.

  2. Tony Trenton says

    Every ancient religious history shows that we are hybrids of aliens and that aliens have been around for thousands of years . The anecdotal evidence is overwhelming.

    Alien abductions counted in the Millions and ongoing through families.

    The characteristic features show that the Aliens are able to detect their prey anywhere on this Planet.

    They are able to control us at their will and incapacitate us with what appears to be a beam of some sort.

    They can ‘Beam us through solid objects’.

    So the primitive concept of an alien invasion to take over this ball of dirt. Is mute and totally unrealistic.

  3. Member
    Aqua4U says

    Within the boundaries of this conversation, I might suggest that an advanced race traveling interstellar distances would probably have figured out controlled fusion reactions and use that to propel their ship(s). If this were true, then we’d not only see a waste heat signature but we’d also see an inexplicable gamma ray beam sweeping past us from a high speed point source. That point source surrounded by a polarized – in the direction of travel – magnetic field.

    “No, that isn’t a magnetar… it’s too close.”

    • Member
      Aqua4U says

      I still like the idea that an interstellar ship would collect +H and O2 molecules to make an ice coating around the hull as it travels thru interstellar space. Say a 5 km thick coating? Shed that when you reach the destination star and lose velocity with a tight/close pass by the star, THEN light up the plasma engines for maneuvering. All the while looking like a simple sun-grazing comet with brightly lit fragmentary comet remnant(s) covering up the ship’s engine exhaust(s) as it emerges from the sun’s glare.

      This scenario is kind of spooky.. there have been a LOT of sun-grazing comets in our time (Thank you SOHO and SDO!) and we’d never know if one or more of them were artificial?

      • Member
        Aqua4U says

        If an ETI came to our planet would they even bother to contact us? Instead they may have a completely different agenda or reason for their voyage. They may be here to take advantage of the advanced life in our seas by collecting and transporting them to ‘nearby’ suitable but barren water worlds? If this is so, then why weren’t we humans invited? I mean after all… Just because we are the source of the ongoing extinction(s) doesn’t mean we are all bad?

  4. meekGee says

    The can decelerate while hiding behind Jupiter, or behind the sun. (Both move slow enough in relation to the Earth) By the time they emerge from behind either body, the detection delay will have shrunk from hours to minutes.

    This is assuming they need to decelerate at all. The first object can just be a small rock moving at 10% c and never slowing down. The ships will arrive years later, once the planet is habitable again. No detection problem then.

    • MarcusAurelius says

      The latter, but that assumes that they are just looking for habitable zone planets, and we happen to be the next one. But a 10%c rock would probably shatter the crust of the planet, not to mention disrupt the magnetic field and probably eject most of the water vapor/atmosphere.

      However, if they are traveling at 10%c, they probably have to decelerate outside the solar system, due to Oort Cloud objects that could be in their path.

  5. kiplingmartin says

    Close Encounters was 1977 dummy.

  6. wokencitizen says

    Our governments may see the aliens coming, but they will not say a thing to the general public…..They are too firmly entrenched in the Brooking’s Inst. Doc of the 60’s that says any knowledge of aliens will cause us all to run amok, hate scientists, hate our government, and, well….. just like the 1939 Halloween radio production of War of the Worlds………..just awful…..

  7. LapsedPacifist 2 says

    One of the most efficient drives possible using known physics would be a photon drive with a very narrow exhaust… something like a very powerful laser. The exhaust would be impossible to detect from outside the beam unless it actually hit something.

    The Earth is a moving target, so the aliens would want to intercept its future location – so if they followed the most direct route the beam would not point at Earth (besides, they probably wouldn’t want to vaporize their destination before arrival!). But its effect on the zodiacal dust would almost certainly make it visible.

    If they want to sneak in though, that should be easy with a well-planned approach from behind the Sun. They only need to keep their exhaust beam pointed directly at the Sun from behind while shedding most of their velocity, leaving just enough to approach Earth in an unpowered NEO-like orbit (like an Apollo asteroid). That would give them a few months to observe us before arrival. And with even rudimentary stealth technology (like we already have) we’d never notice them unless they occulted something obvious.

    At least that’s how I’d do it. 😀

  8. Member
    Ray Bingham says

    Great presentation. Who ever gave Fraknoi and DeGrassi their jobs missed hiring the right guy.

  9. Member
    jamerz3294 says

    If the aliens don’t hide behind the Sun, we’ll see them. But if they want to conquer us with minimal expenditure, they’ll simply toss some asteroids at us. But if they want to enslave us (and really, what alien race doesn’t?) all they hafta do is use Social Media.

  10. TonyTrenton says

    Attempting to travel interstellar distances through the space/time medium at light speeds is totally unacceptable .

    Warping space/time is the only way to go !!!
    There is no limit to the effective speed of warping Space/Time !!!

    Other species from other worlds have most probably fathomed this out thousands of our years ago !!!

  11. kkt says

    Interstellar travel would be incredibly expensive under the laws of physics as we understand them. It seems unlikely that any invasion could possibly be profitable, even for a race that could manage it technically. What could Earth have that they couldn’t get from any number of solar systems with no intelligent life?

  12. bugzzz says

    We won’t see them b/c more likely they’ll be non-biological, microscopic machine intelligences. They could check us out and easily mask their presence.

  13. Steven says

    Like consider another approach to the infrared question….

    a sign of a civilization, not just a rocket thing slowing down, is excess infrared, right? And there were local hunts for excess infrared that came up dry… like http://arxiv.org/pdf/1408.1134.pdf and I seem to recall something similar more recent but can’t find it. Also the infrared surveys of the neighborhood that say there isn’t anything really big really close to the solar system (giant planets out to the neighborhood distances.)

    But then there are… https://en.wikipedia.org/wiki/Luminous_infrared_galaxy

    yes there is a wave of the hand argument it is a colliding galaxy… makes sense…

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