Joule

Pronunciation

• enPR: joul, IPA: /dÊ’uːl/
• IPA: /dÊ’aÊŠl/
• Rhymes: -uːl
• Homophones: jewel

Origin

Named after the English physicist James Prescott Joule.

Full definition of joule

Noun

1. In the International System of Units, the derived unit of energy, work and heat; the work required to exert a force of one newton for a distance of one metre. Also equal to the energy of one watt of power for a duration of one second. Symbol: JThe Greisen–Zatsepin–Kuzmin limit (GZK limit) is a theoretical upper limit on the energy of cosmic rays (high energy charged particles from space) coming from "distant" sources. The limit is 5×10¹⁹ eV, or about 8 joules. The limit is set by slowing-interactions of cosmic ray protons with the microwave background radiation over long distances (~163 million light-years). The limit is at the same order of magnitude as the upper limit for energy at which cosmic rays have experimentally been detected. For example, one ultra-high-energy cosmic ray has been detected which appeared to possess a record 50 joules (312 million TeV) of energy (about the same as a 60 mph baseball).