Laser makes ultra-light mirror out of tiny beads

Shooting a laser at polystyrene beads, scientists have made a mirror that is held together by light. The creation could be a step towards putting ultra-light mirrors in space that would be big enough to see continents and forests on planets orbiting far-off stars.

Current space telescopes have limited vision because is it costly and complicated to send large, heavy mirrors into orbit. The mirror on NASA’s premiere planet hunter, the Kepler space telescope, is just 1.4 metres across and cannot see planets directly. Instead Kepler spots the tiny changes in brightness when a world crosses in front of its host star.

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> Current space telescopes have limited vision because is it costly and complicated to send large, heavy mirrors into orbit.

I tend to disagree with this. The wavelength of red light is less than 1 micron. So metal 1 micron thick is thick enough to act as a mirror for all wavelengths of light, especially in space where corrosion is much less of a problem. Give it a thin strong supporting framework that, for calculation’s sake, doubles the weight of the mirror. The James Webb telescope mirror ways 5.5 tons. A quick calculation says that that weight allows a mirror 1000 meters * 1000 metres to be lifted into space. It would be crumpled up into a ball in the payload bay and naturally uncrumple (perhaps with a bit of help) in space. So large mirrors in space don’t need to be difficult. In addition, it would be so thin that impacting particles would go right through it without damaging more than a square millimeter or so.

So whereas the technique of making a mirror out of tiny beads is very interesting scientifically, it is not the sort of technology that is useful for large space mirrors, at least not with round beads.