Cosmic Microwave Background © ESA

Does the Universe have an edge?

Cosmic background radiation suggests that the Universe is finite, but that doesn’t necessarily mean it has an edge.

Asked by: Gerard Rooney, Newry

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Since light takes time to reach us from the furthest depths of space, and the Universe hasn’t existed forever, there is a distance beyond which we cannot see. This distance is roughly 46 billion light-years away and marks the boundary of the ‘observable Universe’. Since we can never see the Universe beyond this, we have no real idea about how big it may be.

Some research suggests that the Universe is infinite. Other studies, most notably those of the temperature ripples in the cosmic microwave background (the afterglow from the Big Bang), imply that the Universe is actually finite. Even if the Universe is finite in size, it may still not have an ‘edge’, in the same way that the surface of the Earth is finite in area but doesn’t have an ‘edge’.


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