The dumbest question you can ask a scientist—or any other creator, inventor, or discoverer—about his or her work is, “What’s the economic value?”

One reason: In 1888, after eight years of experiments, Heinrich Hertz created electromagnetic waves in air. He died six years later, believing his work was theoretical and without practical value. (In an often repeated, probably apocryphal story, Hertz tells students the waves have “no use whatsoever.”) Then, after his death, inventors found Hertz’s waves could be used to communicate, renamed them “radio waves,” and started a revolution of immeasurable consequence. First came wireless telegraph, then voice broadcasting, two-way radio, radio telescopes, radar, television, microwave ovens, radio satellites, cellphones, radio-frequency identification, GPS, UAVs, Bluetooth, Wi-Fi and, now, the Internet of Things—Hertz’s children all.

Another reason: In 1924, Gordon Dobson, working in his backyard in England, invented a device for measuring atmospheric ozone. In 1976, after deploying 100 of them globally, he died. His work helped save the world. Scientists discovered that CFCs, chemicals used in refrigerators and aerosols, could destroy ozone, exposing us to deadly radiation. The chemical company DuPont, which made billions of dollars selling CFCs, demanded “reputable evidence.” NASA satellites found nothing, but one of Dobson’s devices, in Antarctica since 1957, detected a massive ozone hole. CFC production stopped. Now the hole, once larger than North America plus China, will be gone by 2050.

Why does this matter? Because the dumbest question holds us back. In 2009, physicist David Kaplan gave a lecture on the Higgs boson. An audience member asked, “What do we gain? What’s the economic return? How do you justify all this?”

Kaplan’s good-natured response appears in the movie Particle Fever: “I have no idea.” (Then he mentioned radio.)

The question must be especially painful for American physicists like Kaplan. Scientists discovered the Higgs boson—or something almost exactly like it—using Europe’s Large Hadron Collider. Members of Congress killed the American equivalent, the Superconducting Super Collider, in favor of what one, Don Ritter, called, “making things people want to buy.”

Kaplan’s audience member was interested enough to show up at the lecture, and Ritter is an MIT alumnus who branded himself “the scientist-congressman,” yet both make the mistake at the heart of the dumbest question: confusing unknowable value with no value. History shows that basic science brings the greatest economic value of all—Hertz and Dobson are two of many examples.

Why? First, because of what economics is. Science begets technology, which begets products, which beget value. Science is the principal source of value in modern economies. Second, because economies are chaotic, most of the consequences of any particular technology are unpredictable. An example: The watermill led to the automatic loom, which led to general literacy.

Add in the fact that the point of basic science is to know what’s unknown, and we see that the dumbest question requests the unknowable value of the unknowable consequences of an unknown thing. Note that only two of these are “unknowable.” The third, the “thing,” is only “unknown.” And the unknown, not the unknowable, is what should guide basic science. Kaplan ended his answer by saying, “Basic science needs to occur at a level where you are not asking what is the economic gain, you’re asking what do we not know? And where can we make progress?”

He’s absolutely right. The work of basic scientists like Hertz, Dobson, and Kaplan can only be driven by curiosity, not purpose. What is the value of a particular curiosity? There is no way to know in advance. Discovery is curiosity’s product; everything else, including immeasurable economic value, follows. We cannot know the worth of something we have not yet discovered. In science, as in all truly creative work, the joy is the rainbow, not the hope of gold at the rainbow’s end.

Kevin Ashton is the author of the new book: How to Fly a Horse—The Secret History of Creation, Invention, and Discovery.