Even friendly aliens can cause risks for humanity.

There are two types of risks. That ETI (Extraterrestrial Intelligence) can cause. The first one is internal. The ideas of ETI are against the ideology of some religious people. And that thing can cause violent actions from those people. But if we think that we would someday face the ETI. That thing can cause many types of risks. 

The biggest risk is that the friendly aliens are telling lies. That means they are playing friendly but are hostile. 

And they will come to conquer our planet. But that risk is minimal. If we would get alien contact or confirmed alien contact that thing causes a big change in the human way think and seeing things. 

Cultural differences between humans are a huge thing. So what would you think about differences between humans and hypothetical Kardashev scale II or III civilizations? 

In real life, hypothetical contact between huge-scale civilizations can involve multiple dangers. There is the possibility that aliens are hostile. Or something goes wrong in the communication. In that case, the aliens will use too much power in communication to destroy the entire planet. 

In some other scenarios the power source of their craft, which can be like antimatter would accidentally be released into the atmosphere. That thing can blow the entire Earth. 

The environment and especially microbes on Earth are different than on an alien planet. So that means the microbes will eat those aliens that are landing on our planet. 

And those traveling aliens are the biggest risk that we can imagine. If aliens are traveling by using the fleet of giant O'Neill cylinders. That means they can be cosmic refugees. Or maybe one day in the future automatic alien probe is coming to our solar system. 

It is the possibility that there is an error in those systems. And that causes the alien spacecraft to impact Earth. 

But there is one another risk. If the alien craft uses a black hole as an energy source or communication platform there is a possibility. That something damages the core of the hollow ball where that black hole is. And the Earth will fall in that thing. 

Or there is the possibility that the aliens and humans are making contact. And something will interpret as a threat. Then another side will open fire. 

There is a possibility. That those hypothetical aliens do not think that some civilization has a lower technological level than they have. So those aliens expect that every other civilization is using wormholes as communication. And that can be risky business. Because if those aliens would try to create a wormhole on some other planet, that thing can cause very bad destruction. 

In some other versions, the aliens use tiny wormholes as signal transmit. So, aliens will start to create a wormhole to Earth that makes communication more comfortable. Then the huge energy load will impact Earth. 

Image: https://www.express.co.uk/news/science/1179496/alien-contact-end-times-seti-aliens-discovery-space-universe-news-stephen-hawking

A couple of things about Carl Sagan's novel "The Contact".

Black holes are the loops of time. When information falls in the singularity. It comes out from the point where the black hole formed. This is the thing called the time paradox. The time moves backward in the black hole. 

And if people would go to space travel by using black holes they would come out from the place in time and space where that black hole formed. So the hypothetical astronaut cannot ever prove to be on that journey.

There is a theoretical possibility that engineers can create the hollow singularity around the spacecraft. The system requires the impacting gravitational waves. If the system wants that time moves forward in the craft. It makes the singularity around the craft. And when that thing wants that time moves backward the singularity forms inside the craft. 

And why does the hollow black hole rip astronaut into pieces? The answer is that their system requires two black holes. The symmetry of the gravitation of those two singularities or gravitational cores denies that astronauts ripped into pieces. When the outer gravitational core will pull an astronaut to it. Other black holes in the middle of the capsule pull our hypothetical astronaut back to the capsule's center. 

In the novel and movie "The Contact" the alien civilization tells humans how to create an artificial black hole. And humans send the astronaut journey by using that capsule. Then the astronaut returns and all collected data from that journey is lost. Jodie Foster plays the main character in that film. 

So what if we will make that thing in real life? Or what is the context of reality in that novel? The fact is this. If we would create singularity around the astronaut.  That singularity does not probably rip that person into pieces. In that case, the singularity forms around the traveler.

There are two ways to make that kind of craft. In the first case, the craft will stress by using radiowaves until it turns into a black hole. In another version, the electromagnetic radiation that reflects from the craft pushes atoms and electromagnetic radiation away from its core. 

And that thing makes the WARP bubble around the craft. Then that craft will put spin with extremely high speed. That kinetic energy will turn that object's mass so high that it slips from the universe. 

The thing is that inside a black hole time moves backward. And that's why everything that is stored in tapas is gone. So when black holes form and information fall in a black hole it comes out at the point in space and time where the black hole is formed. 

So this is Einstein's time paradox as I wrote at the beginning of this text. That means even if an astronaut will travel to stars inside a black hole that person will come out from that thing at the point in space and time, where the black hole formed. And that means nobody can even see that our astronauts were on that journey.