system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why do computer screens make ripples when I put my finger on them?

I have always been intrigued by the water-like ripples created by touching computer screens. Why does it happen?
gpt
LCDs, use liquid crystals, which were first discovered in 1888. These crystals are actually liquid chemicals that align perfectly when subjected to electrical fields; when they're properly aligned, they allow light to pass through them. LCDs use this property by using electrical currents to align the crystals and allow varying levels of light to pass through and create the desired images and colors.

To be more technical, the liquid crystals are sandwiched between two pieces of polarized glass ("substrate"). The fluorescent light source, also known as the backlight, emanates light that passes through the first substrate. The electrical currents then cause the crystals to align, allow varying levels of light to pass through to the second substrate. The end result is what you see onscreen.

LCDs can use either active-matrix or passive-matrix structure. Most LCD monitors, along with LCD TVs, use active-matrix.

Any discussion regarding LCD monitors won't be complete without the word "pixel". A pixel is a single point in a graphic image, and stands for "picture element". Each pixel on an LCD monitor comprises of three cells -- one for the color red, one for green, and the last one for blue. Electric currents are used to straighten the liquid crystals within each cell so that light is not bent at this level. An active matrix thin-film transistor is used to activate each cell.