From the “maybe visiting extraterrestrial beings aren’t so friendly department”

 Is it possible to transport millions of biological beings over interstellar distances?

That is indeed easier than you may think at the moment. Already during the 1970s a NASA study group showed that this would be possible even with the technology of those times.

Many millions of individuals would be able to exist absolutely self-sufficiently for an unlimited period of time.
They worked out that each of the space arks would consist of a huge rotating cylinder with a length of 32 km and a diameter of 6.4 km, inside it would offer living space for 10 million individuals with 1g including larger lakes, forests, agriculture, etc. With this diame-ter the atmosphere would already create a blue sky with layers of clouds at an altitude of 1-2 km, so they would have earth-like weather and ozone as a protection against cosmic radia-tion.

Space arks with these dimensions are on the limit of what makes sense today from an ecological point of view, but they are still physically feasible.

It would be possible to use the materials available today to build space arks with a diameter of up to 19 kilometres and living space for up to 100 million people. Of course these arks would not accelerate to almost light speed. Under these circumstances with a high quality of life it would be suffi-cientto travel through space »at a leisurely pace« of »only« 60% light speed or even less, and reach the Earth after 350 or more years.

So, that would be the kind of extraterrestrial UFOs we might expects on the sky, far away from what has been sighted as UFOs. Instead of small and nimble saucers ETI UFOs are huge objects with an extension of umpteen kilometres, which because of their mass will only be able to move at a leisurely pace in space and especially near the Earth. In this respect Roland Emerich’s description of extraterrestrial spacecraft in the science fiction film “Inde-pendence Day” was quite correct.

But certainly not his suggestion that they would be hove-ring over the Earth at low altitudes. The required propulsions with their many millions of tons of thrust would leave a corridor of destruction of several square kilometres on the Earth’s surface . The space arks would rather circle the Earth on a safe orbit of some hundred kilometres, and use smaller payload vehicles to descend to the Earth.

Well, the original question whether these ETIs would come with peaceful intentions, is under these circumstances no longer relevant. The crucial issue for them would be to survive, to look for a new home planet. And humans would just be a nuisance on such an attractive planet as the Earth.

 Interstellar space arks as a concept has been around over 100 years, before the Wright Brothers got off the ground with powered flight even!

Despite the heavy anthropomorphic assumptions in the essay, I found it refreshing that at least someone in the mainstream scientific community has given the subject some thought.

Welcome On Planet Earth…?

Hat tip to Adam Crowl of Crowlspace
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Recently, some scientists and SF writers have expressed their concern that sending messages to the stars in our galaxy, which may have a habitable life, jeopardizes existence of our own civilization because our signals helps ETs to pin down location of the Solar System in the Milky Way.

If the Aliens reached the level of a super-civilization, it might send a space fleet to the Earth to either destroy it or to convert us to slaves.

The goal of this letter is to estimate the probability of detection of the terrestrial radio signals by a presumable hostile super-civilization existing somewhere in our galaxy.

 
Dr. Zaitsev then refers to his chart that shows our incidental signal leakage is more than his METI messages, a 1000 times more!

I’m not too sure about that. His METI radio signals are concentrated and narrow, that’s true. But incidental radar is only pointed at targets here on Earth and in the Solar System and would diffuse greatly at interstellar distances.

Maybe if the aliens were close enough, say maybe out to Alpha Centauri distance (4.3 light-years), they might detect leakage, but even that’s a stretch.

I don’t know. I’m the type of person who wouldn’t wave a bunch of bananas to the 800 pound gorilla in the room unless I had a very, very, very, very good reason to do so.
 
Detection Probability of Terrestrial Radio Signals by a Hostile Super-civilization

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