Aliens haven’t contacted Earth yet because there’s no sign of intelligence here, study claims

That's not to say we're all dummies!

There's a reason you haven't seen aliens at your local Tesco yet. A new study suggests extraterrestrials are yet to drop in on Earth because there's no sign of intelligence here. And we're not just talking about Westminster. But, that isn't to say we're a planet of dummies. Scientists have said the reason is because we've only been sending out signals detectable from space since the 1930s, so extraterrestrials haven't really had that long to receive them. The radio waves have reached about 15,000 stars and their orbiting planets. There's up to 400 billion stars in the Milky Way. On top of that, the study's author Amri Wandel, an astrophysicist at The Hebrew University of Jerusalem, wrote in the paper - published to the arXiv database - that it takes time for any return message from aliens to travel back. On that basis, only stars within 50 light-years have had time to respond since Earth started broadcasting. Another complicating factor, is that Earth's first radio signals weren't deliberately beamed into the cosmos, so aliens looking to decipher them would have struggled to make any sense of them, as they'd be jumbled by the time they even reached one light-year into space. Last month, senior military leaders in the US said The Pentagon had so far not found any evidence to suggest that aliens have visited Earth or crash-landed here. It wasn't until 1974, that we sent the first deliberate high-power broadcast to aliens with the Arecibo message. Plans are afoot to send another in the form of the Beacon in the Galaxy (BITG) message. It will include a drawing of DNA, the solar system and a diagram of the male and female form, but it also contains a lot more information about basic mathematics and science than the Arecibo message did. Wandel wrote that all of these factors were evidence that extraterrestrial life just hasn't had enough time to respond to us. He added that there would have to be more than 100 million technologically advanced planets in the Milky Way for a civilisation to have even received one of them. So, within about 50-light years of Earth, there's no intelligent aliens, Wandel suggests. But that doesn't mean they're not out there, a little further away. It may be that they're waiting for Earth's technological signals to reach them, or their reply is still on the way. Wandel wrote: "The contact probability is defined as the chance to find a nearby civilisation located close enough so that it could have detected the earliest radio emissions (the radiosphere) and sent a probe that would reach the Solar System at present. "It is found that the current contact probability for Earth is very low unless civilisations are extremely abundant. 'Since the radiosphere expands with time, so does the contact probability." He added: "The Contact Era is defined as the time (since the onset of radio transmissions) at which the contact probability becomes of order unity. At that time alien probes (or messages) become more likely. "Unless civilisations are highly abundant, the Contact Era is shown to be of the order of a few hundred to a few thousand years and may be applied not only to physical probes but also to transmissions (i.e. SETI). "Consequently, it is shown that civilisations are unlikely to be able to inter-communicate unless their communicative lifetime is at least a few thousand years." The paper can be read here. Related links:

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