Speed of light they appeared 13 billion years ago, when the universe was less than a billion years old. The fact that more distant objects appear to be younger, due to the finite speed of light, allows astronomers to infer the evolution of stars, of galaxies, and of the universe itself. Astronomical distances are sometimes expressed in light-years, especially in popular science publications and media. A light-year is the distance light travels in one year, around 9461 billion kilometres, 5879 billion miles, or 0.3066 parsecs. In round figures, a light year is nearly 10 trillion kilometres or nearly 6 trillion miles. Proxima Centauri,
IBM 3270 PC a different System Unit 5371, while their AT counterparts (PC AT/G and PC AT/GX) had System Unit 5373. The additional hardware occupied nearly all the free expansion slots in the computer. It included a video card which occupied 1-3 ISA slots (depending on what level of graphics support was required), and supported CGA and MDA video modes. The display resolution was 720×350, either on the matching 14-inch color monitor (model 5272) or in monochrome on an MDA monitor. A further expansion card intercepted scancodes from the 122-key 3270 keyboard, translating them into XT scancodes which were then sent to the