What percentage of the universe is dark matter?

  Astronomers estimate that roughly 85% of all the matter in the universe is dark matter, meaning only 15% of all matter is normal matter. Accounting for dark energy, the name astronomers give to the accelerated expansion of the universe, dark matter makes up roughly 27% of all the mass energy in the cosmos, according […]

Where did ocean currents come from?

Flows of water in Earth’s seas have guided navigators for centuries and shaped climates for much longer. But how did ocean currents first emerge?  These flows would have appeared with the planet’s first oceans, around 4 billion to 4.5 billion years ago, spurred by the same forces that propel them today: winds, tides, global differences […]