Hal Clement's "Longline" (novelette, first contact): What if speed of light is not a limit but a divider?

What if we share space with a different kind of matter - stuff that cannot move slower than light! This is the story of human first contact with "tachyon people" made up of this alternate stuff.

Story summary.

Early part of the story is dedicated to establish alienness of "these tachyon people". They are supposed to be incomprehensible to us, as we are incomprehensible to them; this part is generally in the same spirit as Terry Carr's "The Dance of the Changer and the Three" (included in SciFiction's selected online classics).

There are parts in this section I found completely incomprehensible. These aliens cannot move slower than light, yet they can sort-of reverse direction of their movement, & can, in fact, stop in the sense that we understand the term (or the way I understood it!).

1. To them, "direction" is "as abstract a notion as I've ever heard of, and I can't put it into ordinary words."
2. "momentum is naturally as meaningless as direction, kinetic energy almost equally so, & the interactions between forces & the various fundamental particles follow very different rules."
3. These aliens don't have a "shape" in the sense we understand the term. They cannot perceive most of the matter we perceive - even most stars!
4. They're comfortable "Inside a neutron star"!
5. Their "time is not really commensurable with that in the Einstein-matter universe."
6. Their travel between two points comprises of a series of "casts" - move for a certain time (usually overshooting the target), then move the other way (except that other way is not exactly reverse!) decreasing the error, then repeat this process; humans perceive these movements as confined to some sort of a hemisphere centered at target location (if I recall correctly).
7. There is other weirdness.
   

To help us comprehend the weirdness, author offers this association: "just as a man groups the patterns of electrons & other force fields around him into perceived objects, so did Wattimlan & Feroxtant. A pattern capable of identity maintenance, growth, & duplication, which maintained its existence by ingesting & restructuring other such patterns, might be called a lion or a shark by a human being; such an entity would also possess an identification symbol in the minds of the explorers".

Experienced Feroxtant & young Wattimlan form the crew of the alien expedition to Sirius system - from someplace. A large human expedition also arrives at Sirius system about the same time. There is no way the two sides can perceive each other - except for neutrino discharge that accompanies the movement of both alien ship & human ship. "Longline", of title, is the name of the ship aliens have traveled in.

Both sides are puzzled by unexplained neutrino source, until Jeb Garabed of human expedition gets the wild idea. And generates first few integers & their squares in the form neutrino pulses by controlled movement of a small lifeboat; & gets responses with next higher numbers & their squares - thus beginning the process of contact.

See also.

1. A Bertram Chandler's "Chance Encounter": Another first contact story where aliens are made up of weird matter.

Fact sheet.

First published: Jack Dann & George Zebrowski (Ed)'s anthology Faster Than Light (1976).
Rating: A
Related: All stories of Hal Clement.