Greenland ice Roman lead levels Imperial era

Greenland ice records a rise in Roman lead pollution

4× prehistoric levels

Lead trapped in Greenland ice preserves a record of ancient air pollution. During the Roman Imperial period, lead levels rose to about four times prehistoric levels before falling again later. The pollution provides a clue to the scale of Roman metal production.

Galaxies can merge without their stars colliding

If the Milky Way and Andromeda eventually merge, individual stars would still be extremely unlikely to collide. Galaxies contain enormous amounts of empty space, so their stars can pass through one another’s systems even as the galaxies combine.

Some butterfly migrations take several generations

No single monarch or painted lady butterfly always completes the whole migration route. One generation travels part of the way, reproduces, and dies. Later generations continue the journey.

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Greenland ice Roman lead levels Imperial era

Greenland ice records a rise in Roman lead pollution

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