Well, that sure is a good point. Upon further reading, looks like you can achieve >99.9998% reflectance for a 10% wavelength band (in this case, in the infrare

Well, that sure is a good point. Upon further reading, looks like you can achieve >99.9998% reflectance for a 10% wavelength band (in this case, in the infrared). [http://www.crystallinemirrors.com/wp-content/uploads/20130721_nphoton-2.pdf http://www.crystallinemirrors.com/wp-content/uploads/2013072...] Still, you're right in saying that it's probably still quite a ways off.