It all started with the Arecibo message sent in 1974 using the Arecibo telescope. This telescope delivered a power of three trillion watts, & was directed towards the globular star cluster, M13- 25000 light years from Earth. The message was made using binary digits and contained information about Earth: numbers from 1-10, the DNA molecule, the world population in 1974, human appearance, their average height, a model of the solar system and some technical details of the Arecibo telescope. But why did the scientists resort so much energy and resources to communicate with the aliens, & that too when there was a slim chance of a positive outcome? Well, the Arecibo message was not an actual attempt to communicate with the aliens. Instead, it was to show that with the Arecibo telescope, it was possible to communicate with nearby star systems, highlighting a technological achievement. Also, they wanted to find intelligent extraterrestrials who shared the universal principles of math and science. Therefore, the Arecibo message marked the start of a new era, opening the door of endless possibilities for scientists. In 1977, for the first time, scientists sent a message to aliens via voyager 1.
Voyager 1 carries a golden record with a record player and is noted to have covered 12 billion miles from Earth to date- the farthest human-made object from Earth. It is not directed towards any specific star and is expected to be "found by aliens". This time, however, scientists used hydrogen atoms and binary digits as a mode of communication. Scientists are now contemplating sending another message, which will be a more advanced version than the previous two messages. Alongside the previous message content, it marks the location of Earth using globular star clusters in the Milky Way as markers on their proposed map. It also has a timestamp using hydrogen atoms so the intelligent aliens can know when the message was sent. This will allow the scientists to send multiple messages in the future, and the aliens will be able to track it as a timeline. The message will be sent in 2 ways. One will be sent via China's world's largest radio, expectedly in 2023. This message will be directed to millions of stars in the centre of the milky way. However, this wide range has caused the expected reply to span over 10,000-20,000 light years from Earth. The second attempt is directed towards only one star, enabling a quicker response. The star, Trappist-1, has seven planets, three of which have Earth-like worlds in the "Goldilocks zone", thereby increasing chances of liquid and, possibly, life on those planets.