In existographies, Ole Romer (1644-1710) (IQ:#|#) (GPE:#) (CR:6) or "Roemer" (Ho, 1999), was a Danish astronomer noted for []

Light
In 1665, Romer conjectured that anomalies in the apparent movement of Jupiter's moon Lo, which varied depending on location of the earth in respect to the sun, led to the conclusion that light had a finite speed; this is illustrated as follows:

In 1676, Romer, based on this conjecture, estimated it took light 22 minutes to cross the diameter of the earth’s orbit. (Ѻ) This value was later combined, by Christiaan Huygens, with the value of the earth’s orbit, to obtain an estimate of the speed of light of 220,000 km/s (186,000 miles/sec), which is fairly close to the modern value of 300 km/s.
Romer, in short, was the first to measure the finite velocity of light. [2] Romer's theory was accepted by Isaac Newton and Christiaan Huygens, but rejected by Robert Hooke.

Thermometer
In 1701, Romer made a thermometer in which he defined the lower fixed point to be the freezing point of water at precisely 7.5 degrees and the upper point as the boiling point of water at 60 degrees. [1]

Fahrenheit
In circa 1708, it is said that Polish physicist Daniel Fahrenheit learned of Romer's scale during a visit with him. [3] Fahrenheit commented in a retrospect letter to Dutch chemist Herman Boerhaave, that in about 1717 he had begun using an improved Romer scale, supposedly, by increasing the number of divisions by a factor of four, using different fixed points. Fahrenheit used the fixed points of 96 (instead of 22.5 or 90), the temperature of his wife's armpit, 32 the temperature of ice melting in water, and 0 the temperature of a bath of ice melting in a solution of common salt. This scale is now known commonly as the Fahrenheit temperature scale (˚F), which found its finalized form by 1724.

Quotes | On
The following are quotes on Romer:
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Hooke doubted the ingenious argument put forward by Ole Romer in 1675, that anomalies in the apparent movement of Jupiter’s moons showed that light travelled with a finite, though unimaginably, rapid speed.”
— Stephen Inwood (2002), The Man Who Knew Too Much (pgs. 308-309)

References
1. Romer scale – Wikipedia.
2. Daintith, John. (2005). Oxford Dictionary of Science. Oxford University Press.
3. Whitfield, Peter. (1999). Landmarks in Western Science (pg. 179). Psychology Press.