Sunday, May 15, 2016

A Galactic Collision

We experience time on a characteristic human scale. A starfish on the beach appears to only barely move. But time-lapse film shows that starfish are active, even social creatures. We need to alter our experience of time to truly observe a starfish. Longer is that of a redwood tree, or a continent, or a mountain. Galaxies live in cosmological time, and if we alter our perception to match, we find an equally social existence. 
Galaxies often collide, over millions of years, their stars interpenetrating and intermingling in a kind of cosmic mating ritual. The gravitational maelstrom of these encounters can often spin off a small eddy of stars that becomes a new galaxy, a cosmic birth. These young dwarf galaxies carry off stars, dust, and gas that originated in small regions of one or both of the parent galaxies, as if we had drawn the sample out with a syringe.

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