Imagine you're a Brontosaurus with your face in a prehistoric tree top, munching on fresh leaves. Your relatives have ruled planet Earth for more than 150 million years. Huge and strong, you feel invincible.

You're not.

Fast forward about 65 million years. A creature much smaller and weaker dominates the Earth now, with brains instead of brawn. Its brain is a lot larger relative to its body size - plenty big enough to conceive a way to scan the cosmos for objects like the colossal that wrought the end of your kind.

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