Why Einstein Changed Physics
The World Before Einstein
Physics in the 1800s
Before Einstein, many scientists believed space and time were the same for everyone. If two people watched the same event, they were expected to agree on the time and distance in a simple, universal way. This worked well for everyday life, but it started to fail when people studied light and very fast motion.
Big Idea
Einstein did not begin by asking how to make physics more complicated. He asked how the laws of nature could stay true for every observer, even when they move relative to each other.
The Puzzle of Light
Experiments showed that light seemed to move at the same speed for different observers, which was hard to explain using ordinary ideas about motion. If you ran after a flashlight beam, you might expect the light to look slower, but nature does not work that way.
Important Words
What problem helped motivate Einstein’s special theory of relativity?
The surprising part was that light’s speed appeared to be the same for all observers, which did not fit older ideas of motion.
Correct answer: Light seemed to have the same speed for all observers
In one sentence, what did Einstein want physical laws to do for all observers?
He wanted laws that work consistently no matter how an observer moves.
Correct answer: Stay the same for all observers
What is a reference frame?
A reference frame is the coordinate viewpoint from which measurements are made.
Correct answer: A viewpoint used to describe motion
Course Roadmap
In this course, you will learn what relativity means, why time and distance are not absolute, how mass and energy are related, and how gravity was reimagined as geometry.