>>4264392 (lb)
>https://listverse.com/2013/12/30/10-crazy-facts-about-mirrors/
ahhhh i found it.
>We all know that you can travel through time in a wormhole, right? The only trouble is that wormholes have a tendency to collapse, which prevents anything from passing through them. However, help is at hand, with a simple pair of mirrors. All you need is two uncharged mirrors (or metallic plates) in a vacuum, placed a few micrometers apart—make sure there is no external electromagnetic field. Now comes the Casimir effect, which is a physical force arising from a quantized field between the two mirrors. This quantum electrodynamic force produces a mass-negative region of space-time between the mirrors, which could stabilize a wormhole, and allow faster-than-light travel. Theoretically, you could travel to the past, but not the future—so you couldn’t get next week’s winning lotto numbers, unfortunately. Another fly in the ointment is that the stable wormholes produced by the mirrors are infinitesimally small, so don’t plan a holiday to visit your ancient ancestors just yet.