Simplify the following text for a Grade 4 native English-speaking person.
Original: The coldest theoretically possible temperature is absolute zero , also called absolute temperature , which is 0 K on the Kelvin scale , a thermodynamic temperature scale , and â ' 273.15 Â C on the Celsius scale .
Simplified: The coldest possible temperature is â ' 273.15 Â C , which can be expressed as about -459.67 Â F on the Fahrenheit scale . This is called absolute zero .