The image below was obtained in a completely darkened room using a camera sensitive to infrared light. The light detected in this image is being emitted directly from the person and his surroundings. All hot objects glow -- a phenomenon known as blackbody radiation. The hotter the object the brighter the glow. Objects at temperatures of thousands of degrees (like the Sun) are hot enough to glow with light visible to the eye. Cooler objects, humans for example, will primarily emit infrared light. The hotter the object, the more infrared light emitted. This particular human is holding two identical coffee cups. One is filled with hot coffee. The other is filled will cool water. Your eyes would not be able to distinguish between the two cups, but the difference is quite apparent when the observations are made using infrared light. Similarly, the Universe can look quite different when information is collected using light beyond the range of human senses.