Astronomy
The Interstellar Medium's Effect on Starlight Polarization
Quick fact
Starlight can become polarized by as much as a few percent when it passes through dense clouds of interstellar dust, and this polarization is observable even though dust grains are about the size of smoke particles.
Why this is interesting
When you look at a star, its light might have a secret twist—polarization—that tells you about invisible magnetic fields and tiny dust grains thousands of light-years away. How can a simple property of light reveal so much?