Why screens look the way they do.
Every viewport on this site is a rectangle someone argued over. Where 72 DPI came from, why 640×480 was the floor for a decade, how 16:9 won by being everyone's second choice, where the word pixel came from, and why a tube taught us to say “refresh rate”.
72 DPI, and the WYSIWYG bargain
The original 1984 Macintosh display was built to roughly 72 pixels per inch on purpose. Printers' type is measured in points at 72 to the inch, so one point equaled one pixel, and a 12-point font on screen stood 12 pixels tall — what you saw was what would print.
Every later fight about “logical pixels” and 2× displays descends from that bargain. That's the number this whole site is quietly negotiating with when it draws a viewport at true CSS-pixel size.
640 × 480, the industry floor
IBM's VGA standard, in 1987, defined 640 × 480 — the resolution that became the floor of the industry for a decade, and the reason “SD” video is the shape it is.
16:9, the negotiated rectangle
When television needed a widescreen standard, SMPTE engineer Kerns Powers surveyed the aspect ratios in actual use — from boxy 4:3 TV to CinemaScope-wide film — and found that a rectangle near 1.78:1 (16:9) was the compromise that fit them all with equal letterboxing pain: wide film loses the same fraction to bars as narrow TV does.
16:9 won not by being anyone's favorite but by being everyone's second choice. Which is why it's the aspect you'll see most on the formats page.
Where the word “pixel” came from
Pixel is short for “picture element”. The term settled into print through 1960s image-processing work at JPL — Frederic Billingsley's 1965 usage is commonly credited as the first in print. The abbreviation “pel” fought it, and lost.
The CRT, and why we say “refresh rate”
One electron beam, sweeping line by line, sixty times a second — an image that never actually exists all at once. Phosphor persistence and the eye do the rest.
This is why we still say “refresh rate”, and why old cameras caught rolling bars on CRT screens: they were photographing a picture mid-sweep. The flat panel you read this on inherited the vocabulary of a tube it no longer resembles.