Do you guys think humanity stands a chance against an alien invasion?

[Martian2]

The type of aliens I'm talking about (200 years ahead, so type 1-type 2) would likely be recognizable to us.

A type 2 civilization would already be sci-fi level (as in, Starcraft or Star Trek level).

A type 3 civilization would be fatansy level (Star Wars).

A type 4 civilization would be indistinguishable from natural phenomena.



If they were refugees from a nearby system, and superior technologically, their backs are to the wall and it'll be "it's either us or them" scenario. a vastly superior alien race would have no reason to even bother with us, but one that was only a few hundred years ahead would definitely have reasons to bother with us.

You have a problem with the Type 2 and Type 3 civilization categories. They are fictional.

The known laws of physics state that nothing can move faster than the speed of light. Einstein's Theory of Relativity has been proven over and over again. It is a law of our universe.

Hence, Star Trek warp drives are fictional. So is Star Wars hyperspace jumps.

In the real world, things are mundane and boring.

To the best of our knowledge, with the best space telescopes observing the full electromagnetic spectrum, there is nothing artificial within 1,000 light years of Earth.

Hubble is looking in visible wavelength and near-infrared.
Chandra is looking in X-rays.
Fermi is looking in Gamma rays.

Herschel looked in far-infrared and it found nothing. Sorry, no alien spaceship.

References:

Chandra X-ray Observatory | NASA
Fermi Large Area Telescope
ESA Science & Technology: Herschel

 

[FairAndUnbiased]

You have a problem with the Type 2 and Type 3 civilization categories. They are fictional.

The known laws of physics state that nothing can move faster than the speed of light. Einstein's Theory of Relativity has been proven over and over again. It is a law of our universe.

Hence, Star Trek warp drives are fictional. So is Star Wars hyperspace jumps.

In the real world, things are mundane and boring.

To the best of our knowledge, with the best space telescopes observing the full electromagnetic spectrum, there is nothing artificial within 1,000 light years of Earth.

I know. That's why I do not talk about FTL anywhere, do I?

Also, the SETI program frequently looks at objects within 1000 light years because the volume of space within 1000 lightyears of earth is on the order of 1 billion cubic lightyears. Nowhere near all objects within this volume have been classified because the telescopes are not looking at them. This, of course, is just a fun scenario to think about, but we don't even know the outer extent of the solar system right now.

 

[untitled]

If they are ET like aliens then we have nothing to worry

 

[Martian2]

I know. That's why I do not talk about FTL anywhere, do I?

Also, the SETI program frequently looks at objects within 1000 light years because the volume of space within 1000 lightyears of earth is on the order of 1 billion cubic lightyears. Nowhere near all objects within this volume have been classified because the telescopes are not looking at them. This, of course, is just a fun scenario to think about, but we don't even know the outer extent of the solar system right now.

Come on. A kilometer-length spaceship that you proposed would stand out like a giant infrared beacon against the 2.7 Kelvin temperature of outer space. It's hard to miss.

The law of thermodynamics necessitates the radiation of heat from a hot object (e.g. a spaceship) to its surrounding. For example, Earth is radiating away heat in massive quantities. Otherwise, the Earth would melt. Similarly, a spaceship engine generates a huge amount of heat. It must be radiated to its surrounding space. We can see that infrared signature.

The Herschel Space Telescope would have seen it.

 

[Kashmiri Pandit]

The real use of Nuclear Bombs is for Large Meteoroids and Alien Invasions .

A reason why US is not destroying its Nuclear Arsenal

 

[FairAndUnbiased]

If they are ET like aliens then we have nothing to worry

I am sure that if aliens exist, I think there's only a limited number of ways they can interact with humanity:

1. They are too advanced and we cannot distinguish them from the laws of physics.
2. They do not care about us/don't find us.
3. They are predators/slavers/hunting us for fun so we better lie low.
4. They are desperate refugees, so we better lie low.
5. They are microorganisms.

I doubt that any benevolent aliens would show up and give us enlightenment. I do not see any beneficial way of interacting with aliens, if they do exist.

Come on. A kilometer-length spaceship that you proposed would stand out like a giant infrared beacon against the 2.7 Kelvin temperature of outer space. It's hard to miss.

The law of thermodynamics necessitates the radiation of heat from a hot object (e.g. a spaceship) to its surrounding. For example, Earth is radiating away heat in massive quantities. Otherwise, the Earth would melt. Similarly, a spaceship engine generates a huge amount of heat. It must be radiated to its surrounding space. We can see that infrared signature.

The Herschel Space Telescope would have seen it.

I did not intend for this to reflect reality at all. But scientifically, engines 2 lightyears out wouldn't be a sure catch with today's technology. There are parts of the solar system (less than 0.1 light years) that are still unexplored. The inverse square law still works for infrared. In fact there's many stars out there that aren't even detectable in the visible, and are within 10 light years or so.

 

[Donald Trump]

I will fly a Teja and kill them all, oh wait....

I would prefer a JF Thunder instead as it has been portrayed as the most advanced fighter yet! Oh wait.....

 

[atomix]

If they were refugees from a nearby system, and superior technologically, their backs are to the wall and it'll be "it's either us or them" scenario. a vastly superior alien race would have no reason to even bother with us, but one that was only a few hundred years ahead would definitely have reasons to bother with us.

Mate , I commented in a philosophical jest about human nature not technically.

 

[Vapnope]

I would prefer a JF Thunder instead as it has been portrayed as the most advanced fighter yet! Oh wait...

Not better than Indigenous developed Tejas

 

[Pakistani till death]

An alien invasion means that they found us! This means they are faaar more advanced than us in every possible way which makes the conclusion pretty easy. We wont stand a chance!

 

[911]

Only idiots will invade useless earth, not some intelligent aliens. What has earth to offer that sun can't. Advanced intelligence capable of reaching earth would probably be able to build artificial earth-like living place own thier own.

 

[FairAndUnbiased]

Only idiots will invade useless earth, not some intelligent aliens. What has earth to offer that sun can't. Advanced intelligence capable of reaching earth would probably be able to build artificial earth-like living place own thier own.

depends. a generation ship filled with refugees and dealing only with real world physics wouldn't be too unimaginable. i dont think you realize how hard it is for earth to actually exist.

 

[Khan_patriot]

Don't worry, if Hollywood is anything to go by then humanity need not worry as long as we have Merica on our side

 

[Martian2]

Engines have to fire to slow down

The premise is an alien ship that is one kilometer long traveling at 0.1 light-speed and it is two light-years from Earth.

If the aliens don't want to fly by Earth at 0.1 light-speed, the one kilometer spaceship had better aim its engines at Earth and start firing to decelerate.

Since we do not see an alien ship decelerating in the infrared spectrum, we don't have to worry about it. By the way, you can't miss a one-kilometer long spaceship firing its nuclear engines in a hurry to decelerate. It will require a massive amount of energy and time to slow a one-kilometer long mass from 0.1 light-speed to zero meter per second.

 

[FairAndUnbiased]

Engines have to fire to slow down

The premise is an alien ship that is one kilometer long traveling at 0.1 light-speed and it is two light-years from Earth.

If the aliens don't want to fly by Earth at 0.1 light-speed, the one kilometer spaceship had better aim its engines at Earth and start firing to decelerate.

Since we do not see an alien ship decelerating in the infrared spectrum, we don't have to worry about it. By the way, you can't miss a one-kilometer long spaceship firing its nuclear engines in a hurry to decelerate. It will require a massive amount of energy and time to slow a one-kilometer long mass from 0.1 light-speed to zero meter per second.

that's true. However there's alot of data out there and there are wierd angles of approach, such as from perpendicular to the plane of the solar system where telescopes don't look all that often. Also, inverse square law makes it alot harder than you think to observe things. Just so you know: Proxima Centauri, a red dwarf star orbiting Alpha centauri, isn't even visible despite being only 4 light years away. It is dim in the IR. Engines output trillions of times less energy than even the dimmest star and more importantly have a tiny cross section.