Chapter 10

20 YAL

At first our mother’s departure felt much like the trips she had taken in the past when Zuri and I were children. But as the days of her absence continued, we realised that she wasn’t coming back.

“Daddy?” Ananya’s high voice piped above my head as she swayed side to side on my shoulders.

“Yes, sweetheart?”

“How many stars are there?” My eldest daughter – Ananya had emerged into the world two minutes before her sister – had recently become obsessed with counting and numbers. Petals in a flower, how many steps we took each day; anything and everything that could be enumerated was fascinating to her. I supposed that this question was a logical endpoint; it also served as a good distraction from the torrent of water flowing around my waist.

No matter which side of the ringriver we walked during our migrations, we were always forced into several crossings if we wished to continue following the circumference of the habitat. The easiest fording was just upstream of the canyonland’s waterfall, where we could skip across the chain of cherry tree islands. If we crossed forward to the bow there and walked antispinward, we’d come to a junction of the streams that brought water down from the mountains, their confluence too deep and strong to cross safely during the summer. Settling in the broad and fertile valley that they surged through, we’d usually remaiun until the next microwinter, when it was easy for the children to cross the icy trickles of the headwaters high in the alpine biome. From there we could descend back down to the ringriver and continue antispinward, crossing the island chain again to return into the summerlands.

Taking the same route on the aft side of the river brought us against Amazonia, who’s waters came down from the mountain we called Themis Mons, thirty kilometers to the stern. Skirting this riverine system was a trek of at least three days through hot and arid terrain, but it was a circumnavigation that Zuri had insisted on each time, the thought of crossing the river with the children filling her with dread. Wide, deep and turbulent, Amazonia flowed through the jungle like a snake, thick and brown with silt, and was challenging even for adults to ford at any season. But eventually we’d yielded to Hotene’s demands that we come this way.

At this point in the season the water flow around my waist thrummed against my body like the wind snapping a flag. As my sister watched anxiously from the bank, I’d crossed once with Hotene, who now sat impatiently against the thick tangled roots of a kapok on the opposite shore.

“I suppose that depends on the set of stars you’re trying to count,” I said, taking another sideways step, turning to face the current to reduce the pressure of the water against my knees. “Do you mean the stars in our galaxy, our local group, or the universe?”

A short way downstream, water flowed cleanly over the curved carapaces of the two factos that followed me step for step, their multiple arms linked together and extended outwards to form a safety line in case I slipped.

Ananya thought about that for a while. “All the stars,” she said finally. “Everywhere.”

“Ah, then you mean the cosmos.” Sliding sideways on a slick rock half-buried in the riverbed, I tottered for a moment before recovering my balance. Taking a breath, I recovered in the shadow of a standing wave passing over a boulder further upstream, leaning forward into the current. “No-one knows for sure,” I said finally. “A great many. Probably less than infinite.”

“How much less than infinite?”

“We don’t know,” I answered, resuming my careful sidesteps. “But there’s a more interesting question there, I think.”

“Like what?”

“Well, like the fact that some infinities are bigger than other infinities.”

The extended silence from above allowed me to cross most of the remaining breadth of the stream with my concentration undisturbed. “But that doesn’t make sense,” Ananya said finally. “Infinite is –” I clutched her ankles a fraction tighter as she stretched out her arms from side to side, swaying on my shoulders as we approached the far bank. “Infinite is the biggest that can be.”

“Alright. Think of all the odd numbers. Do they go on forever?” Grunting with effort, I took a giant step to bring us up onto the muddy slope.

I could feel Ananya mentally double-checking that as she climbed down from my shoulders to sit beside her sister. “Yes,” she concluded.

“Okay. Now think of all the natural numbers you could count with, odds and evens all together. Is that infinite too?”

“Yessss... “ Ananya’s dark eyebrows pressed close together in concentration.

“But there can only be half as many odd numbers as natural numbers. That means that the natural numbers must be a bigger infinity.”

“That... “ Her frown deepened. “That makes my head hurt.”

Chuckling, I reached down to gently stroke her head. “But it’s an interesting question, isn’t it.”

“Yeah.” She looked up from her perch on the thick root. “Would the takamakura have an answer to that?”

“Not answers, exactly. That’s not what they provide. But you’ll be able to learn more from them about natural densities, when the time comes.” Zuri and I had agreed to keep the devices from our daughters until they were at least 10. We wanted them to enjoy being children longer than we had. “I’ll be right back with Mom, okay?”