“The radiation left over from the Big Bang is the same as that in your microwave oven but very much less powerful. It would heat your pizza only to minus 271.3°C – not much good for defrosting the pizza, let alone cooking it.”
- January 8, 1942 – March 14, 2018
- British
- Theoretical physicist, science writer
- Announced the black hole singularity theorem and Hawking radiation, and contributed to the popularization of science with his book “Talking about the Universe”
Quote
“The radiation left over from the Big Bang is the same as that in your microwave oven but very much less powerful. It would heat your pizza only to minus 271.3°C – not much good for defrosting the pizza, let alone cooking it.”
Explanation
In this quote, Stephen Hawking is referring to the cosmic microwave background radiation (CMB), which is the faint glow of radiation left over from the Big Bang. This radiation, which permeates the entire universe, is the afterglow of the early universe, about 380,000 years after the Big Bang, when the universe cooled enough for atoms to form and light could finally travel freely. This background radiation is very similar in nature to the radiation produced by microwave ovens, but the key difference lies in its extremely low temperature.
Hawking humorously contrasts the microwave radiation in our kitchens with the CMB to emphasize just how faint and cold the remnants of the Big Bang are. The CMB has a temperature of just 2.7 K (about -270.45°C), which is incredibly cold compared to the heat needed for cooking. He notes that if you used this radiation to try and heat a pizza, it would only cool it to -271.3°C, far colder than the freezing point of water and completely inadequate for cooking or even defrosting food. This comparison serves to show how small and faint the cosmic radiation is in comparison to the heat and energy we experience in everyday life.
This also touches on one of the remarkable aspects of cosmology: the CMB provides direct evidence of the Big Bang and gives scientists important clues about the early universe, its expansion, and its evolution. While it’s too weak to have any practical use for heating pizza, the CMB has been a crucial tool in understanding the origins and large-scale structure of the universe. This underscores the ongoing discovery of how the universe’s history and its physical laws are written into the background radiation that we encounter, even if it’s too faint for everyday human needs.
