They say that for every grain of sand in the world, there should be 100 Earth-like planets in the universe. So why haven’t we encountered alien life forms? One possible answer could come from the recent successes scientists have had in extending the boundaries of our cosmic map by plotting the position of our galaxy among our many neighbouring galaxies.
Looking out from our little blue planet, we see around 2500 different stars on a good night. This might seem huge, but it’s only 1 per cent of our galaxy, the Milky Way. And our galaxy is just one of many. The universe is an intricate web of galaxies, with some parts empty dark voids, and other parts dense with galaxies, called superclusters.
Brent Tully and his team at the University of Hawaii have created a map of the supercluster that includes our Milky Way galaxy. This enormous supercluster has been named Laniakea, Hawaiian for ‘immeasurable heaven’, a fitting name for a community millions of light-years across.
But what is most interesting about this cosmic map is our position. Earth and the Milky Way exist right at the farthest reaches of the Laniakea supercluster, with a blue void between us and parts dense with galaxies. Essentially, Earth is right at the end of the last cul-de-sac in the most boring part of town. Maybe we haven’t met anyone passing by because no one can be bothered driving all the way to our place.
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