NASA's Goddard Space Flight Center/Conceptual Image Lab
If the universe originated at the big bang 13 billion years ago, how can there be stars that are 30 billion light years away?
Sarah Bloxham,
via email
Andriy Popov/Alamy
Why do our knuckles and joints make a popping sound when cracked? Does it do us any good or harm?
Noah Horne,
Patrick Space Force Base, Florida, US
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