5.5K views · 231 reactions | When it comes to planted aquarium lights, many people want to know the PAR rating. PAR stands for "photosynthetic active radiation" and basically measures how bright a plant light is. However, many things can effect the PAR rating of a light — such as the distance from the light, height of the tank, use of an aquarium lid or not, and placement of the plants. #AquariumCoop | Aquarium Co-Op | Facebook

Why do you see a blue glow inside of a reactor? | International Atomic Energy Agency (IAEA)

What’s that blue glow surrounding a reactor? It’s a phenomenon known as Cherenkov Radiation when electrically charged particles, such as protons or electrons, travel faster than light in a clear medium like water. | U.S. Department of Energy Office of Nuclear Energy