Scale of temperature
Rømer temperature conversion formulae
|
from Rømer
|
to Rømer
|
Celsius
|
x
°Rø ? (
x
? 7.5) ×
40
/
21
°C
|
x
°C ? (
x
×
21
/
40
+ 7.5) °Rø
|
Fahrenheit
|
x
°Rø ? ((
x
? 7.5) ×
24
/
7
+ 32) °F
|
x
°F ? ((
x
? 32) ×
7
/
24
+ 7.5) °Rø
|
Kelvin
|
x
°Rø ? ((
x
? 7.5) ×
40
/
21
+ 273.15) K
|
x
K ? ((
x
? 273.15) ×
21
/
40
+ 7.5) °Rø
|
Rankine
|
x
°Rø ? ((
x
? 7.5) ×
24
/
7
+ 491.67) °R
|
x
°R ? ((
x
? 491.67) ×
7
/
24
+ 7.5) °Rø
|
For temperature
intervals
rather than specific temperatures,
1 °Rø =
40
/
21
°C =
24
/
7
°F
Conversion between temperature scales
|
The
Rømer scale
(
Danish pronunciation:
[??œ?m?]
; notated as
°Rø
), also known as
Romer
or
Roemer
, is a
temperature
scale named after the
Danish
astronomer
Ole Christensen Rømer
, who developed it for his own use in around 1702. It is based on the
freezing point
of pure
water
being 7.5 degrees and the
boiling point
of water as 60 degrees.
[1]
: 365
Degree measurements
[
edit
]
There is no solid evidence as to why Rømer assigned the value of 7.5 degrees to water's freezing point. One proposed explanation
[1]
: 367
is that Rømer initially intended the 0-degree point of his scale to correspond to the
eutectic temperature
of ammonium chloride brine, which was the coldest easily-reproducible temperature at the time and had already been used as the lower fiducial point for multiple temperature scales.
[1]
: 362
The boiling point of
water
was defined as 60 degrees. Rømer then saw that the freezing point of pure water was roughly one eighth of the way (about 7.5 degrees) between these two points, so he redefined the lower fixed point to be the freezing point of water at precisely 7.5 degrees. This did not greatly change the scale but made it easier to calibrate by defining it by reference to pure water. Thus the
unit
of this scale, a Rømer degree, is
of a
kelvin
or
Celsius
degree. The symbol is sometimes given as °R, but since that is also sometimes used for the
Reaumur
and
Rankine scales
, the other symbol °Rø is to be preferred.
Historical significance
[
edit
]
Rømer's scale would have been lost to history if Rømer's notebook, Adverseria, was not found and published in 1910 and letters of correspondence between
Daniel Gabriel Fahrenheit
and
Herman Boerhaave
were not uncovered in 1936. These documents demonstrate the important influence Rømer's work had on Fahrenheit, a young maker and seller of barometers and thermometers.
[1]
Fahrenheit visited Rømer in Copenhagen in 1708 and while there, became familiar with Rømer's work with thermometers. Rømer also told Fahrenheit that demand for accurate thermometers was high.
[2]
: 4
The visit ignited a keen interest in Fahrenheit to try to improve thermometers.
[3]
: 71
By 1713, Fahrenheit was creating his own thermometers with a scale heavily borrowed from Rømer that ranged from 0 to 24 degrees but with each degree divided into quarters.
[2]
: 31
[4]
At some point, the quarter degrees became whole degrees and Fahrenheit made other adjustments to Rømer's scale, modifying the freezing point from 7.5 degrees to 8, which, when multiplied by four, correlates to 32 degrees on Fahrenheit's scale
[3]
: 73
The 22.5 degree point would have become 90 degrees, however, Fahrenheit rounded this up to 24 degrees?96 when multiplied by 4?in order to make calculations easier.
[2]
: 20
After Fahrenheit perfected the crafting of his accurate thermometers, their use became widespread and the
Fahrenheit scale
is still used today in the United States and a handful of other countries.
See also
[
edit
]
Notes and references
[
edit
]