A Brief History of Time

A Brief History of Time

by

Stephen Hawking

Teachers and parents! Struggling with distance learning? Our Teacher Edition on A Brief History of Time can help.
Imagine a ripple on a pond—there are peaks and troughs to the wave. The more powerful the ripple, the shorter the gap between the peaks, called the wavelength, and the higher the frequency of the waves. If a trough of one wave meets a peak, or crest, of another, they cancel each other out. In physics, waves, and even particles, move in a similar manner, so studying their wavelength can provide useful information.
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Wavelength Term Timeline in A Brief History of Time

The timeline below shows where the term Wavelength appears in A Brief History of Time. The colored dots and icons indicate which themes are associated with that appearance.
Chapter 2
The Search for a Unifying Theory of the Universe Theme Icon
Human Curiosity and Ingenuity Theme Icon
...the electromagnetic field would travel at constant speeds, just like ripples in ponds. The different wavelengths (the distance between each wave crest) were different types of light; there are, for example,... (full context)
Chapter 3
Human Curiosity and Ingenuity Theme Icon
...light spectrum. The Doppler effect tells us that as something moves away from us, each wavelength will be longer, while if it is approaching us each wave would reach us more... (full context)
Chapter 4
Human Curiosity and Ingenuity Theme Icon
...the light in the quantum, the more accurately you can see the particle, because the wavelengths of the light will be shorter. But that means more energy will be applied to... (full context)
Human Curiosity and Ingenuity Theme Icon
...distances from the light source, and through the slits, to reach the wall. Therefore, the wavelengths of these beams of light will overlap rather than arrive “in phase with each other,”... (full context)
Human Curiosity and Ingenuity Theme Icon
...mechanics, the electrons would move as waves, and therefore would only form orbits where the wavelengths were whole numbers. If the wavelengths needed to complete an orbit was not a whole... (full context)
Chapter 5
Human Curiosity and Ingenuity Theme Icon
The question remains as to what the truly indivisible particle is. The smallest wavelength of light we can see is larger than these particles, so we cannot “look” at... (full context)
Chapter 8
The Search for a Unifying Theory of the Universe Theme Icon
Human Curiosity and Ingenuity Theme Icon
...whole universe. To find a space-time that is really possible, one adds up all the wavelengths of all the associated possible particle histories of that universe. (full context)
Chapter 10
Human Curiosity and Ingenuity Theme Icon
...the plates. Within the plates, the photons would only occur in the space if their wavelengths matched the width of the space between the plates in terms of whole numbers, otherwise... (full context)