“Yes. Let me show you. Here is the telescope. I train it on a star—a star, mark you, that is not a sun, but that shines by reflected light. This beam of starlight, contains moonlight, earthlight, sunlight (our sunlight, you know)—and the light from millions of other suns. The starlight comes out from here”—he touched the lower end of the telescope.
“Now you see this ray of my own created light passes directly in front of where the starlight comes out—that’s where they mix.”
Tubby saw the little beam of white light crossed at right angles to the telescope eyepiece and passed very close to it.
“This light of my own is created by burning zonogen—a gas I discovered myself.
“From this point, where the starlight joins it, my ray goes to the spectroscope”—he touched another portion of the Light Machine—“and it is polarized here. These”—he indicated a long row of tiny black compartments; Tubby could see the beam of light entering at one end and emerging at the other—“these are my image extractors. Each takes from the light some of its images—leaving finally only the earthlight and the images that belong to it.
“There are many other processes—some day you will understand them all. But for now—let me show you the result.
“The pure earthlight passes last of all into my projector. See it here?” He laid his hand on what looked to Tubby something like a magic lantern.
“My operating power is electricity.” He turned a switch. Tubby first heard a low hum and then a whirring, clicking sound.
“This projector magnifies the image—throws it up on a screen.” He pointed to the wall; Tubby saw a small square of canvas hung on the wall.
“Now then,” the professor continued, his voice trembling with emotion, “that star my telescope is pointing at is now exactly nine hundred and twenty-seven and one half Light-years away. That means that eighteen hundred and fifty-five years ago to-night the light we are getting back now from that star left the earth. Do you know what was happening eighteen hundred and fifty-five years ago to-night?”