What are the main differences between the E-ELT and existing telescopes?
The European Extremely Large Telescope (E-ELT) will have a diameter of 42 metres (almost half the length of a soccer pitch) and will thus be the biggest telescope in the world — by far — to observe in the visible and the near-infrared (there are of course larger radio telescopes). In other words, it will be the world’s biggest “eye” on the sky. The current largest optical telescopes have a diameter of about 10 metres, and the E-ELT will thus be four times greater.The 42-metre diameter was chosen because it is the minimum diameter needed to achieve some of the driving science cases: to image rocky exoplanets to characterise their atmospheres, and to measure the acceleration of the expansion of the Universe directly.The main principle behind the telescope is that it is an adaptive telescope. Adaptive mirrors are incorporated into the optics of the telescope to compensate for the fuzziness in the stellar images introduced by atmospheric turbulence. One of these mirrors is supported by mor
