Astronomy
The Effects of Solar Radiation Pressure on Spacecraft Navigation
Quick fact
Sunlight exerts about 4.5 micronewtons per square meter on a perfectly absorbing surface—enough that after a year, a spacecraft like the Mariner 10 shifted its trajectory by several kilometers.
Why this is interesting
You know how sunlight feels warm on your skin? That same light also pushes on you, and for spacecraft, this push—though gentle—can send them drifting off course over months.