The helicopter hovered above the maw of the maelstrom, and as everyone looked down at the spinning funnel, they soon felt nauseated and dizzy. Someone entered directions into the navigation system for the helicopter to spin, matching the whirlpool’s rotation below. This way, the whirlpool appeared still, but the world outside—sky, sea, and mountains—began to spin around them. The maelstrom seemed to become the center of the world, and the observer’s nausea wasn’t reduced in the slightest. AA vomited up all the fish she had eaten.
As she gazed at the whirlpool below, another whirlpool appeared in Cheng Xin’s mind: It was made up of a hundred billion silver stars spinning in the sea that was the universe, taking 250 million years to complete one rotation—it was the Milky Way. The Earth was not even as big as a mote of dust in this whirlpool, and the Moskstraumen was but another mote of dust on the Earth-dust.
Half an hour later, the boat fell into the eye and disappeared abruptly. Amidst the unchanging rumbling, they seemed to detect the sound of the boat being ground apart.
The helicopter dropped Jason off at Mosken, and Cheng Xin promised to compensate him with a new boat as soon as possible. Then they said farewell and the helicopter headed for Oslo, the nearest city with a sophon-free room.
Everyone remained deep in thought through the voyage, not even conversing with their eyes.
The Moskstraumen’s meaning was so obvious that no thought was required.
But the question remained: What did lowering the speed of light have to do with black holes? What did black holes have to do with the cosmic safety notice?
A black hole couldn’t change the speed of light; all it could do was to change the wavelength.
Lowering the speed of light in vacuum to one-tenth, one-hundredth, or even one-thousandth of its natural speed would mean thirty thousand kilometers per second, three thousand kilometers per second, and three hundred kilometers per second, respectively. It was hard to tell how black holes would be involved.
There was a threshold here that had to be crossed—hard to do for normal patterns of thinking, but not so for this group, among the most brilliant minds humanity had to offer. Cao Bin, in particular, was good at unconventional ideas. As a physicist who had crossed three centuries, he knew something else: Back during the Common Era, a research group had successfully reduced the speed of light through a medium in a lab to seventeen meters per second, slower than someone riding a bike. Of course, this was not the same as lowering the speed of light through vacuum, but at least it made what he imagined next seem not so crazy.
What if the speed of light were reduced even further, to thirty kilometers per second? Would that involve black holes? It still seemed essentially the same process as before… wait!
“Sixteen point seven!” Cao Bin shouted. The fire in his eyes quickly set the other eyes around him ablaze.
The third cosmic velocity of the Solar System was 16.7 kilometers per second. A spacecraft from the Earth could not leave the Solar System without exceeding this limit.
It was the same with light.
If the speed of light through vacuum in the Solar System were reduced to below 16.7 kilometers per second, light would no longer be able to escape the gravity of the Sun, and the Solar System would become a black hole. This was an inescapable consequence of the derivation of the Schwarzschild radius of an object, even if the object was the Solar System. More precisely, the necessary speed limit would be even lower if a larger Schwarzschild radius were desired.
Since nothing could exceed the speed of light, if light couldn’t leave the Solar System’s event horizon, nothing else could either. The Solar System would be hermetically sealed off from the rest of the universe.
And therefore completely safe—as far as the rest of the universe was concerned.
How would a distant observer see the Solar System black hole created by lowering the speed of light? There were two possibilities: for technologically primitive observers, the Solar System would simply disappear; and, for technologically advanced observers, they should be able to detect the black hole, but instantly understand that the system was safe.
This was the cosmic safety notice. The impossible was possible, after all.
The interpreters thought of the Glutton’s Sea, thought of the Storyless Kingdom sealed off from the rest of the universe by the sea. This additional bearing coordinate really wasn’t necessary—they already understood.
