Course

Special Relativity: what follows from one speed

Name: Special Relativity: what follows from one speed
Price: 1499 BDT

Assume one thing, that light travels at the same speed for everyone, and follow it until clocks disagree, simultaneity dissolves and metre rules shrink. Every result is derived on screen, and the course ends on the muons that prove it.

10 lessons1h 17mEnglish

What you'll learn

State the two postulates and identify which everyday assumption the second one contradicts
Derive time dilation from a light clock without being given the formula
Decide which observer measures the proper time in a given situation
Calculate the Lorentz factor and explain why relativity is invisible at everyday speeds
Show that two events simultaneous in one frame need not be simultaneous in another
Use the relativity of simultaneity to resolve an apparent paradox
Calculate a contracted length and say which direction is unaffected
Apply the Lorentz transformation to an event and check the interval is unchanged
Explain muon survival at sea level from either frame, and show the two accounts agree

Requirements

Comfortable with Pythagoras and rearranging algebra
Familiar with speed, distance and time, and with reading a graph
No prior relativity is assumed, and no calculus is used

Course content

10 lessons · 1h 17m

Time is not universal

One postulate, followed until clocks disagree. A light clock makes time dilation a matter of Pythagoras, and simultaneity turns out not to be a property of two events at all.

0/4

The one postulate that breaks everything

Speeds add for everything you have ever thrown. Light refuses, and something else has to give.

Preview9m 2.

Time dilation, from Pythagoras

Same speed of light, longer slanted path, longer tick. The factor is a right-angled triangle and nothing more.

Preview10m

Simultaneity is not a property of two events

One flash, two verdicts about which end was lit first. This is the result that dissolves the paradoxes.

10m

Problem set: clocks and order

Four marked parts on a probe at 0.60c: the Lorentz factor, both journey times, and which clock is entitled to call its reading proper.

Space, and the machinery

Length contraction follows from what measuring a moving object actually requires. The Lorentz transformation gathers every result so far into two lines, and muons arriving at sea level turn the whole argument into a measurement.

0/4

Length contraction, and what measuring really requires

To measure a moving rod you must mark both ends at once, and the two frames do not agree on at once.

Preview10m 2.

The Lorentz transformation, and what stays the same

Two lines that contain everything so far, and one combination of coordinates that every observer agrees on.

Preview11m

Muons at sea level: the measurement

Classical physics says one muon in four million arrives. About a fifth do, and both frames agree on why.

11m

Problem set: lengths and frames

Four marked parts on a spacecraft passing a station, ending with why each crew measuring the other as shorter is not a contradiction.

About the creator

Classytic