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What makes galaxies spin in a certain direction? Part two

One reader wonders if the outer-points of a galaxy’s spirals precede or trail the rotation

15 November 2023

B1PP5G Spiral Galaxy M74 i. Image shot 2008. Exact date unknown.

NASA/Dembinsky Photo Associates/Alamy

What makes galaxies spin in a certain direction? And do they all spin in the same direction? (cont.)

Steve Powell
Hursley, Winchester, UK

One aspect of this question seems not to have been addressed. Spiral galaxies spin, we are told, and their direction of spin depends upon our perspective, of course. But do the outer points of the spirals precede or trail the rotation?

We instinctively feel that the arms should be “swept back” from, or trail behind, the rotation. But that, surely, is a result of our local experience of rotations driven centrally in a friction-providing medium, as…

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