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The physicists analyzed Gaia's measurements of more than 33,000 stars, including some of the farthest stars in the galaxy, and determined each star's "circular velocity," or how fast a star is circling in the galactic disk, given the star's distance from the galaxy's center.

She and her colleagues measured the circular velocity of stars and found that the resulting rotation curves were surprisingly flat.

They then incorporated this map into a model of circular velocity, to simulate how fast any one star must be traveling, given the distribution of all the other stars in the galaxy.

Sickness might also be produced probably with advantage by whirling the patient in a chair suspended from the cieling by two parallel cords; which after being revolved fifty or one hundred times in one direction, would return with great circular velocity, and produce vertigo, similar I suppose to sea-sickness.

At the planet’s mean distance, the circular velocity of the vortex is equal to the circular velocity of the planet, and, at different distances, is inversely in the sub-duplicate ratio of those distances.