What Would It Actually Take for Aliens to Reach Earth? An Aerospace Scientist Did the Math

[Freija]

What Would It Actually Take for Aliens to Reach Earth? An Aerospace Scientist Did the Math

To assess the plausibility of alien visitors, it’s necessary to understand the obstacles that an extraterrestrial vessel would need to overcome to reach Earth.

studyfinds.com

This is somewhat of a lengthy read but my opinion of the "aerospace scientist's" analysis is that it is entirely based on our current levels of understanding and technology and doesn't take into account there could be civilizations millions or billions of years older than our own that have developed completely different solutions

In a Nutshell​

• Any alien civilization capable of visiting Earth would need to travel at least 4.25 light-years from the nearest star system, a distance so immense that even optimistic estimates put a realistic cruise speed at roughly 10% the speed of light — a journey taking a century or more.
• Propulsion alone presents an almost insurmountable hurdle: chemical rockets would require more fuel than the entire observable universe contains, antimatter remains nearly impossible to produce at scale, and even nuclear fusion would demand fuel mass roughly 150 times the weight of the spacecraft itself.
• No single law of physics rules out interstellar travel outright, but the compounding weight of hundreds of extreme, often conflicting engineering requirements — shielding, fuel load, structural integrity — may make a crewed voyage to Earth physically impossible regardless of how advanced a civilization becomes.

Finding a way to accelerate the ship to its target cruise speed is the central challenge facing any would-be alien explorers.

Interstellar space is unforgivingly vast, but the emptiness has some advantages. The lack of atmosphere means there is no aerodynamic drag. So when the ship reaches its cruise speed, it can shut down its propulsion system and coast toward the final destination. Unfortunately, the lack of atmosphere also means there is nothing to slow the ship down prior to arrival. So ideally, the propulsion system would be used for both acceleration at the start of the trip and deceleration at the end.

One of the more exotic propulsion strategies employs high-powered laser beams to push the ship through space. The beam is projected from a stationary array near the travelers’ home planet and directed toward a thin reflective sail attached to the ship. The beam’s photons exert radiation pressure on the sail, propelling the ship forward.

The Trillion-Dollar Question​

Ultimately, engineering challenges are just some of the many barriers to interstellar travel. Any prospective alien visitors must also have sufficient cognitive ability, technological maturity, physical resources, collective desire and proximity to Earth.

That said, if the stars were to align and an alien vessel made it to Earth intact, it would trigger a torrent of burning questions: Where are they from? What do they want? What are they made of?

But the question that would go furthest in shedding light on the deeper mysteries of the universe is, “How on Earth did they get here?”