"Our known Universe contains matter, radiation, and dark energy."
"Dark energy, the zero-point energy of empty space, possesses a positive, non-zero value."
https://www.forbes.com/sites/startswithabang/2021/08/16/5-ways-that-dark-energy-might-not-determine-the-fate-of-our-universe/?sh=5f9fc66e4515
"Dark energy is a hypothetical form of energy that is proposed by physicists to explain why the universe is not just expanding but is doing so at an accelerating rate."
https://www.space.com/dark-energy-what-is-it
"According to a new study scheduled to be published in The Astrophysical Journal, scientists have determined that outer space isn’t pitch black at all — it’s actually filled with light. While we all know that stars emit plenty of visible light, we’ve generally assumed that space, as a whole, is completely dark in the absence of stars. And it is definitely dark, but apparently, it’s not that dark."
https://www.travelandleisure.com/trip-ideas/space-astronomy/nasa-scientists-discover-outer-space-isnt-pitch-black
"A black object absorbs all wavelengths of light and converts them into heat, so the object gets warm. A white object reflects all wavelengths of light, so the light is not converted into heat and the temperature of the object does not increase noticeably."
https://profound-answers.com/why-does-black-absorb-more-heat-than-light/
"The average temperature of outer space near Earth is 283.32 kelvins (10.17 degrees Celsius or 50.3 degrees Fahrenheit)."
https://sciencing.com/temperatures-outer-space-around-earth-20254.html
"Thermal expansion is the phenomenon observed in solids, liquids, and gases. In this process, an object or body expands on the application of heat (temperature). Thermal expansion defines the tendency of an object to change its dimension either in length, density, area, or volume due to heat."
https://byjus.com/thermal-expansion-formula/
"The electromagnetic (EM) spectrum encompasses all wave frequencies, including radio, visible light and X-rays. All EM waves are made up of photons that travel through space until they interact with matter; some waves are absorbed and others are reflected."
https://sciencing.com/7-types-electromagnetic-waves-8434704.html
"Dark energy makes up 68%, about two-thirds, of the universe."
https://spaceplace.nasa.gov/dark-matter/en/