United States Government Latest version Hundreds of previously classified unidentified anomalous phenomena (UAPs) spanning from the 1940s to the present, along with Steven Spielberg’s new movieThe day extraterrestrial life was detected fueled the idea that aliens are visiting Earth.
In fact, opinion polls in Australiathe we and elsewhere It suggests that about a third of the public believes aliens are here.
However, while what we know about the universe suggests that aliens may exist, there are three compelling reasons why they might not visit us.
Space is big – very big
To begin with, The space is wide – Beyond our imagination.
Next to SuntoryThe closest star to our sun is about 40 trillion kilometers away, or 268,000 times further away than the sun is from Earth. This is equivalent to 4.3 light-years as measured by astronomers. A light year is the distance that light travels in one year at a speed of 300,000 kilometers per second.
We can travel through space at only a fraction of the speed of light using current technology. Even our fastest spacecraft are… Parker Solar ProbeIt travels at a maximum speed of about 191 kilometers per second – 0.064% of the speed of light.
At this speed, it would take about 6,650 years to reach Proxima Centauri, and that’s just in our local stellar neighborhood. So interstellar travel during a human’s lifetime requires much higher speeds.
Suppose we had the means to travel at close to the speed of light. This represents the first problem with traveling at this speed. Albert Einstein proved this Time is relative; The rate of flow of time is not the same everywhere in the universe. The faster a spaceship is moving away from Earth, the slower time will pass for its passengers. This is called time dilation.
For example, when NASA astronaut Scott Kelly returned to Earth after a year on the International Space Station, he was a millisecond younger than he was. Identical twin Because time moves more slowly for moving objects and the International Space Station He travels At approximately 28,150 kilometers per hour.
This difference was minimal for the Kelly twins. But for any aliens flying through our skies, that would be much greater because the journey to Earth and back from a distant star system is necessarily at a higher speed. They will return to a planet much older than the one they left – perhaps a century or more. They will be exiled through time.
Image from the Apollo 17 mission in December 1972.
NASA
Unimaginably high power requirements
Then there are the unimaginably high energy requirements for interstellar travel.
The mass of the spaceship increases with speed, so… An increasing amount of energy It is required to speed it up.
At the speed of light, the ship becomes infinitely massive, requiring an infinite amount of energy. Obviously this is impossible.
Another important issue is that space is a vacuum, but not completely. There is enough Particles for anxiety on. They can cause lethal radiation to the passengers and instruments of the high-speed spacecraft, or destroy them. The sparsely scattered hydrogen atoms turn into intense radiation at a speed close to the speed of light, and the heat generated will diminish and eventually destroy the structure.
Faster-than-light travel, according to physicist Miguel Alcubierre, is possible, but it comes with its own implications A range of issues and currently impossible energy requirements.
This raises the question: Why spend all that energy traveling to Earth? Anything we have, an advanced civilization (as they had to be to get here) would be able to achieve on their planet.
A unique biosphere
Another issue is our biosphere, which as far as scientists know is unique to Earth.
Life and the planet have evolved together. Complex life would not exist on Earth without the presence of cyanobacteria, a type of single-celled microbe Pumped oxygen In our atmosphere, which consists mostly of nitrogen, 2.4 billion years ago.
So it’s not toxic to us, but oxygen is reactive and can be very corrosive to aliens. While they can wear protective suits like humans do when going into inhospitable environments, Reports to Visiting foreigners It does not include any descriptions of the spacesuits.
So, are there aliens?
If the aliens aren’t here, are they there?
It’s an interesting question, both scientifically and philosophically. Scientists don’t have enough information yet, but they are working to solve this question.
About 6,200 exoplanets They are found in more than 4,700 solar systems, although none are like Earth or our own solar system.
Most stars can and do have at least one planet More than 100 billion stars In our galaxy alone. Therefore, the number of planets is astronomical, and some of them may be habitable.
Closer to home, there are worlds with Potential for microbial life Both past and present – Mars, Europa (Jupiter’s moon), Enceladus and Titan (Saturn’s moons). If we discover that life began twice in our solar system, this will increase the possibilities for life to exist in other places.
Since 1960We have the ability to look for intelligence elsewhere, relying on ordinary radio astronomy. The largest search for alien life projects is carried out by City Institute In California and Breakthrough listening A project based at the University of Oxford in the United Kingdom.
Nothing was found in all the searches performed. Finding intelligence in our time frame – about a hundred years – in the 13.8 billion year history of the universe is difficult.
However, like 1959 Nature paper Note that although it is difficult to estimate the chance of success, if we do not look the chance drops to zero.
Carol OliverProfessor of Communication Sciences and Astrobiology, University of New South Wales Sydney
This article was republished from Conversation Under Creative Commons license. Read Original article.
