What does the word "thumper" mean when used to measure distance?

Question

There are several places in Dune where the word "Thumper" is used as a measure of distance:

• On the north polar map of Dune, there's an arrow pointing to the left with the caption:

  20 Thumpers to Palmaries of the south

• After Paul summons and rides his first sandworm:

  Paul studied the cliff, the great streaks of rock crossing it like waves. No green, no blossom softened that rigid horizon. Beyond it stretched the way to the southern desert – a course of at least ten days and nights, as fast as they could goad the makers.

  Twenty thumpers.

• Appendix I The ecology of Dune

  Kynes went down to the palmaries himself – a twenty thumper trip (in a palanquin like a wounded man or Reverend Mother because he never became a sandrider).

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The arrow on the map starts at about 60°N and from the cartographic notes for the map, we know that the palmaries are at 40°S, so 20 thumpers subtends about 100° of the planet's circumference.

From the "They have tried to take the life of my son" chapter, we know that Dune's surface gravity is 0.9g:

'Hey! Feel that under your dogs? That's gravity, man!' 'How many G's does this place pull? Feels heavy.' 'Nine-tenths of a G by the book.'

From that, I'm assuming that Dune is roughly the same size and constitution as Venus which also has a surface gravity of about .9g, so an equatorial diameter of 12,092 km and circumference of 37,988 km. So a thumper would be approximately 527.6 km (or almost 328 miles).

In the Terminology of the Imperium, a thumper is described as:

THUMPER: short stake with spring-driven clapper at one end. The purpose: to be driven into the sand and set "thumping" to summon shai-hulud. (See Maker hooks.)

An interpretation might have been that a "thumper" is the distance at which it can be heard or sensed (by sandworms). However, it doesn't seem likely that a small mechanical device could be heard at a distance of over 500 km.

What does the word "thumper" mean when used to measure distance?

Answer 1

The "Thumper" is not an exact distance, it is the average distance you can travel on a single sandworm. The books discusses how the sandworms can be ridden until they become too tired and just stop. When the hooks have been removed the worm then goes deep down into the sand to rest and another worm has to be called.

The book does discuss different sizes of worms being able to go different lengths, so that is why this is not an exact measurement.

Answer 2

When measuring distances, it's the distance an average sandworm will go bearing riders. It's a synonym for "worm" as a unit of distance.

We can infer that it's about 5° latitude from the text (given ; we also know that the local gravity is 0.9G, giving a rough diameter about 0.9 Earths; this gives about 36000 km (rounded from 0.9 x 40075=36067) circumference, and thus about 100km per degree. This puts a Worm/Thumper at about 500km. This presumes an Earth-like composition. (Venus as a comparison is less dense than earth.)

It's noted that a worm can hear a thumper for several kilometers - Paul's wormsign starts at the horizon...

Slowly, he scanned the horizon, listening, watching for the signs he had been taught.It came from the southeast, a distant hissing, a sand-whisper. Presently he saw the faraway outline of the creature’s track against the dawnlight and realized he had never before seen a maker this large, never heard of one this size. It appeared to be more than half a league long, and the rise of the sandwave at its cresting head was like the approach of a mountain

Note also that Liet-Kynes states that large worms typically stake out territories of 200-400 square kilometers, and can defend that, implying up to 20 km range - if it's only able to sense targets to half that, it's still 10 km, while the horizon is likely to be about 4.2 km, a distance at which Paul spots his called worm.

Paul leaned forward, touched Kynes’ shoulder. “How big an area does each worm stake out?”

Kynes frowned. The child kept asking adult questions.“That depends on the size of the worm.”

“What’s the variation?” the Duke asked.

“Big ones may control three or four hundred square kilometers. Small ones—” He broke off as the Duke kicked on the jet brakes.

So, we know that a worm is able to hear the thumper over the horizon, calculating the horizon to some 4+ km. We can calculate the distance one can travel at an average of 500 km, knowing that some worms will go considerably further.

More importantly, given the Fremen tendency to plan for the worst, 500 km is not even likely the actual average, but more likely the bound of the first standard deviation below average; in other words, probably 2/3 of worms answering a thumper can go further.