Many scientists argue that sending messages into space without knowing who will receive may be a bad idea. This could lead to a bad future for Earth.
Since the 19th century, humanity has started using electric lights. This device has so far been more advanced, less power-efficient and brighter. The houses and streets at night are lit, people can live normally like day.
Besides the undisputed socio-economic benefits, artificial lighting is also the cause of many concerns. The first is light pollution that disturbs the natural order of nocturnal animals, or wastes energy.
Even scientists are concerned that artificial light can attract a number of other species, just like electric light bulbs attract moths. Only thing, these species do not come from Earth.
The question of whether or not any civilization other than us exists in the universe does not yet have an answer. However, the more we search, the more convinced the scientists are that there are living and growing creatures like ourselves. They can be very advanced, may just be in the form of bacteria.
What if a certain alien race has the technological potential of being superior to humans, discovering we are here, in the Milky Way? Many scripts and films about this subject have been born, bringing both positive and opposite views. But more than anyone else, it's the scientists who are arguing the most about aliens.
In 1974, Frank Drake radio astronomer used the most powerful radio transmitter at Arecibo, Puerto Rico, to broadcast the message into space, announcing human presence. This message is now 45 light years from Earth. Although there are more stars and planets near us, they are not on the broadcast trajectory of Drake.
Instead of waiting for feedback signals, scientists have made more efforts to find such signals in space. As more planets are discovered around other stars, the search for extraterrestrial intelligence - abbreviated SETI - has become hotter than ever.
In 2015, businessman Yuri and Julia Milner spent $ 100 million on Breakthrough Listen SETI project. They hire observatories to detect "artificial" signals from outer space.
The universe was immense but cold and seemingly empty. Scientists began to wonder why we have never found the aliens' signal. This question is called "Fermi paradox", named after physicist Enrico Fermi.
In many ways to answer this question, a hypothesis seems very reasonable. That aliens may fear other aliens invade, so they choose to remain silent.
Many scientists agree that sending messages into space without knowing who it is can be a bad idea. After sending, maybe alien civilizations do not answer us.
Unlike a post on Facebook, this greeting cannot be removed. Is it safe to tell others your location? Further, is there any civilization that has heard and prepared our invading fleet?
Human radio communications, including aircraft navigation, television broadcasting and the Internet, can also be detected from space. Inadvertently, people broadcast many artificial signals that any advanced civilization can recognize.
Recently, however, the Earth has been much quieter , thanks to fiber-optic cable and carefully tuned satellite signals. In the past, we were too reckless to broadcast a lot of radio waves. Now, when we know "fear", mankind gradually becomes wiser.
However, there is still an inevitable 'eyes and ears' of curious people, which are LED lights .
The image of Earth at night shows that our presence is breathtaking. Cities, each of which is highlighted by the contours of the continents in the lights. Oil rigs are scattered across the sea and ships are tiny bright spots across the ocean.
This type of light differs from old light sources using incandescent lamps, without a natural spectrum. From orange or bluish sodium mercury lamps, to white light-emitting diodes (LEDs), the artificial origin of the modern light spectrum is easily recognized by an advanced technology civilization.
In the coming decades, space agencies on Earth will develop many means of detecting artificial light from planets around us.
We may fail, if the aliens believe that the smartest thing to do if we want to live in peace is to remain silent and stay in the dark. On the other hand, we may have been seen and the fleet that conquered Earth may be on its way here.
This raises the question: Is the single person in the universe a gift?