Astronomy Picture of the Day

Explanation: How different are space and time at very small scales? To explore the unfamiliar domain of the miniscule Planck scale -- where normally unnoticeable quantum effects might become dominant -- a newly developed instrument called a Holometer has begun operating at the Fermi National Accelerator Laboratory (Fermilab) near Chicago, Illinois, USA. The instrument seeks to determine if slight but simultaneous jiggles of a mirror in two directions expose a fundamental type of holographic noise that always exceeds a minimum amount. Pictured above is one of the end mirrors of a Holometer prototype. Although the discovery of holographic noise would surely be groundbreaking, the dependence of such noise on a specific laboratory length scale would surprise some spacetime enthusiasts. One reason for this is the Lorentz Invariance postulate of Einstein's special relativity, which states that all length scales should appear contracted to a relatively moving observer -- even the miniscule Planck scale. Still, the experiment is unique and many are curious what the results will show.