I am trying to discover the name of a book recommended to me by my school physics teacher some 48 years ago. The premise of the book is that the proponents visit a world where the speed of light is comparable to the speed of sound and how this affects all aspects of life.

  • Do you remember anything else about this you can edit in like how it affects life or did you just get told a basic overview?
    – TheLethalCarrot
    Oct 23, 2018 at 13:06
  • I am fairly sure they only calculated the speed of speed much later. Thunder and lightning would not have been different entities. Oct 23, 2018 at 13:07
  • More detail is needed; I can think of at least two potential answers to this, one of which was written as an accessible explanation to young people, the other a SF novel where the slow speed of light was an important plot point, but the story not intended as educational. Oct 23, 2018 at 13:12
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    George Gamow's Mr Tompkins in Wonderland (1939) immediately comes to mind, though the speed of light there is a mere 10 mph. Oct 23, 2018 at 13:22
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    @user14111 - funny, but he means definition 2: merriam-webster.com/dictionary/comparable
    – zzxyz
    Oct 24, 2018 at 0:52

3 Answers 3


This is Mr. Tompkins in Wonderland (1939). After attending a lecture on relativity the protagonist dreams that he enters a fantastical world where light moves at a mere fraction of the speed of sound.

When he opened his eyes again, he found himself sitting not on a lecture room bench but on one of the benches installed by the city for the convenience of passengers waiting for a bus. It was a beautiful old city with medieval college buildings lining the street. He suspected that he must be dreaming but to his surprise there was nothing unusual happening around him; even a policeman standing on the opposite corner looked as policemen usually do. The hands of the big clock on the tower down the street were pointing to five o’clock and the streets were nearly empty. A single cyclist was coming slowly down the street and, as he approached, Mr Tompkins’s eyes opened wide with astonishment. For the bicycle and the young man on it were unbelievably shortened in the direction of the motion, as if seen through a cylindrical lens. The clock on the tower struck five, and the cyclist, evidently in a hurry, stepped harder on the pedals. Mr Tompkins did not notice that he gained much in speed, but, as the result of his effort, he shortened still more and went down the street looking exactly like a picture cut out of cardboard.

Archive.Org - Full Text available here

  • 2
    That was my first thought, too, but the speed of light in the book is only 10 mph - far less than the speed of sound. Even bicycling introduces noticeable relativistic effects. Oct 23, 2018 at 13:25
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    @KlausÆ.Mogensen - Sound is mentioned on multiple occasions in the story though. "Also, if you move, say in a car, to meet the sound propagating through the air, the velocity of the sound as measured in the car will be larger by the amount of your driving speed, or it will be correspondingly small if the sound is overtaking you. We call it the theorem of addition of velocities and it was always held to be self- evident.", etc. Certainly it's mentioned enough that OP may have forgotten the difference in the intervening five decades
    – Valorum
    Oct 23, 2018 at 13:27
  • 1
    This sounds exactly like I remember, indeed the example given of the cyclist is one I remember him quoting. Thank you very much, now I just need to find a copy!
    – c021752c
    Oct 23, 2018 at 13:32
  • @Valorum - You posted the same link twice. The illustration one appears to go to the text.
    – Bobson
    Oct 23, 2018 at 15:30
  • You can read the whole text by following the link here and view the illustrations here
    – Valorum
    Oct 23, 2018 at 15:32

This could be Redshift Rendezvous by John E. Stith. When the titular starship Redshift is in hyperspace, the artificial black hole at its core, combined with the reduction of lightspeed in hyperspace, means the speed of sound is a quick run, while the speed of light is only several times that figure. Time dilation effects can vary noticeably between your head and your feet, you must wear a lifebelt to keep your nerve impulses fast enough to sustain life, and your watch will never agree with any other clock until you reset it after leaving hyperspace.

And in this bizarre environment, someone or something is killing people...

  • 1
    ... and this was the other one that I was thinking of! Oct 23, 2018 at 14:27
  • What's a watch? Oct 23, 2018 at 18:46
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    A watch is generally a small clock that you wear on your wrist or in your pocket (not all languages distinguish, so I'm assuming that's a serious question).
    – FuzzyBoots
    Oct 23, 2018 at 19:01
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    I'd guess that no one recommended Redshift Rendezvous (1990) in 1970. Oct 23, 2018 at 22:35
  • This was a fine story - but of course, not old enough.
    – davidbak
    Oct 24, 2018 at 1:25

While this is clearly not the answer you're looking for, the Discworld novels by Terry Pratchett would fit the bill (if not for the recommendation being 48 years ago). In the Discworld, the speed of light is explicitly described (by the author) as being about the speed of sound, and perhaps less - my memory has dropped that particular detail.

Additionally, the speed of Dark is even greater, since that's how dark gets out of the way.

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    While true in the description of disclight, relativistic effects are never touched on in the books. Not even in The Science Of Discworld. Oct 23, 2018 at 15:09
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    There is some stuff that could be considered relativistic effects in Thief of Time when Lobsang and Lu-Tze slice their way closer to the wall. Blue/Red shifting and faster personal frames of reference for example.
    – Jontia
    Oct 23, 2018 at 15:23
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    There's some talk in one of the books that there must be another type of light that travels incredibly fast that allows them to see the light that is slowed down by magic, but it's not really looked into that deeply.
    – DqwertyC
    Oct 23, 2018 at 18:26
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    @HarryJohnston I'd have to re read that one. In any case, the examples are far less prevalent and important than I'd consider necessary to answer the question. I feel that the slowness of disclight is more of a humor thing than mechanical. Ie "haha isn't that funny" a oppressed to "no, its literally like that." Remember that the explanation (a footnote!) was followed up by kingons and queenons (and possible annihilation when encountering republicons, if the character hadn't gotten thrown out of the bar). Oct 23, 2018 at 19:37
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    @Draco18s - Well, sure, the slowness of disklight IS more of a humor thing. But what in the Discworld isn't? Oct 23, 2018 at 22:40

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