90 degrees Fahrenheit equates to 32.22 degrees Celsius. The equation will be:

The mercury thermometer was invented by Gabriel Fahrenheit, a German scientist in Holland in 1714. It was used to measure temperature. He was also able to define the boiling and freezing points within water as 212 degrees and 32 degrees Fahrenheit.

Carolus Linnaeus from Sweden defined the centigrade scale 25 years later. This was subsequently refined by Anders Celsius in 1742. The Celsius temperature was thus born, and marked the boiling and freezing points within water as 100 and 0 degrees Celsius.

Although Celsius and Fahrenheit is each a different measurement, they nevertheless still have a common source and can convert easily to each other.

For the most part, the United States is still using the Fahrenheit scale while Celsius is used almost everywhere else throughout the world. The Celsius scale is from the metric system. It is quite easy to convert Fahrenheit to Celsius:

- C= (F-32)x 5/9.

The mercury thermometer was invented by Gabriel Fahrenheit, a German scientist in Holland in 1714. It was used to measure temperature. He was also able to define the boiling and freezing points within water as 212 degrees and 32 degrees Fahrenheit.

Carolus Linnaeus from Sweden defined the centigrade scale 25 years later. This was subsequently refined by Anders Celsius in 1742. The Celsius temperature was thus born, and marked the boiling and freezing points within water as 100 and 0 degrees Celsius.

Although Celsius and Fahrenheit is each a different measurement, they nevertheless still have a common source and can convert easily to each other.

For the most part, the United States is still using the Fahrenheit scale while Celsius is used almost everywhere else throughout the world. The Celsius scale is from the metric system. It is quite easy to convert Fahrenheit to Celsius:

- Start with the Fahrenheit temperature. In this instance it is 90.
- Subtract 32 from 90. This will be 58.
- Divide 58 by 9. This will be 6.44.
- Multiply 6.44 by 5. Your answer is 32.22 degrees Celsius.

- When the Celsius temperature scale was invented, it first denoted the point of boiling water as zero while freezing point was denoted as 100. The scale was subsequently reversed the following year.

- The very first thermometer was invented in 1654. There were no degrees denoted on it.

- · In 1701, Isaac Newton invented the very first scale.

- · The lowest possible temperature in theory is called Absolute Zero. At minus 459.67 degrees Fahrenheit or minus 273.15 degrees Celsius, all heat energy within any matter will be lost and the motion of all molecules ceases.