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Mysterious signal hints at nearby alien life

Would aliens look like us? As scientists pick up a mysterious radio signal from the Earth’s closest star, some think we could be on the brink of our first ever alien encounter. In April 2020, astronomers at the Parkes telescope in Australia picked up an unusual radio signal. It was coming from the direction of Proxima Centauri, the closest star to our own solar system. It was definitely artificial, not natural. And tiny shifts in frequency suggested that it might be coming from another planet. For nearly a year they kept it secret. After all, unexplained radio signals usually turn out to be man-made. But now they have gone public. Why? Because, after months of failing to find any human source for the signal, they believe this could be the most promising breakthrough in the search for aliens since the Wow! signal of 1977. They have named it Breakthrough Listen Candidate 1 (BLC-1). Next to Proxima Centauri is an exoplanet slightly larger than Earth. Named Proxima b, the planet is thought to orbit within the habitable zone, meaning that it has the right atmospheric conditions to host liquid water. This would allow life to develop on its surface. If there are aliens on Proxima b, we have a real chance of meeting them. Travelling at 20% of the speed of light, a spacecraft could travel from one system to the other in a few decades. In fact, researchers are already working on a tiny, laser-powered probe that would be able to make the trip. And while humans are still a long way from the technology needed to transport people out of our solar system, a more advanced alien civilisation might already have this capacity. So, if a spaceship from Proxima b does end up setting down on Earth, what will our visitors look like? For well over a century, humans have speculated about the appearance of aliens. Some have imagined them as humanoid, like Superman or The Doctor. But others have suggested aliens would look completely different from us. John Wyndham’s book The Kraken Wakes is about a jellyfish-like species that can only live in ocean trenches. Proxima b is a very different place from Earth. Its year lasts just 11 days. It orbits a red dwarf star that releases fierce radiation. And it is probably tidally locked with its sun: half of it in constant day, and the other half in constant night. That would mean its only habitable space would be a thin band between these two zones, trapped in eternal twilight. It is difficult to see how any species evolving in these conditions could look like us. They would likely have huge eyes to cope with the dimmer light on their home planet. They might also have less tolerance for large temperature changes. They would have evolved in a lower atmospheric pressure, meaning that the pressure on Earth could crush their bodies. On the other hand, thanks to the more powerful gravitational field on Proxima b, they would probably be physically stronger than human beings. But there might also be similarities between us. In order to use tools, they would have to have at least two limbs – one to hold a tool and one to hold an object – and digits capable of gripping things. And if aliens are behind BLC-1, they must have similar technology. Would aliens look like us? Peas in a pod Yes, say some. To develop advanced technology, the aliens would have to have sophisticated problem-solving capacity and at least two dextrous limbs. That alone would make them very similar to human beings. They must have complex language, like we do. Most importantly, if they are broadcasting their location to the universe, they probably share that most fundamental human trait: curiosity. Not at all, say others. Alien life would have evolved in very different conditions from ours. Their civilisations might have developed very differently, and they might have faced entirely different moral and social questions. Their way of thinking could be completely incomprehensible to us. They might not even be able to survive in the conditions of Earth. KeywordsHabitable zone - Also known as the Goldilocks zone. The range of orbits where the temperature is "just right" for liquid water.

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