The three of them could clearly feel the ground beneath their feet trembling slightly.
"The root system of the World Tree can also take root in the underground world..."
Xu Xin looked at the magnificent scenery before him, which he had helped create, and murmured.
"Thatās right, but it canāt spread like it does above ground," Xu Ying said with a hint of regret. "This underground world contains an empty area with a vertical distance of up to three thousand meters without soil. The roots of the World Tree can penetrate the ground of the underground world in this way, and this is almost its limit."
"Isnāt the root system of the World Tree able to expand to areas hundreds of kilometers away?" Li Wenxi sensed the vibrations beneath her feet. "If there were no such hollow underground world, could its roots continuously extend downward?"
"Iām not sure about that either, but judging from the situation above, it would probably reach deeper."
Xu Ying looked up at the dome.
The intricate root system covered the dome above them.
These roots had already emerged from the dome, crawling over the entire dome as if expressing their dissatisfaction.
They still want to drill downward, but thereās no soil or rock for them to penetrate.
The ground beneath continued to shake, yet the giant beasts and insects above stopped panicking and became calm, lying on the ground as if they were sensing something.
The three of them were also waiting for the vibrations to stop, waiting for the root system to crawl over this area.
"Hey, do you think this underground world could spread all over the globe?" Li Wenxi asked the question on her mind.
"Hmm? It actually does spread globally?" Xu Ying turned to look at her. "There shouldnāt be any issue with that, right?"
"If so... what supports the ground above?" Li Wenxi extended her slender finger, pointing upward.
"Ah, you mean that, right? There definitely is support," Xu Ying explained. "Although the underground world is entirely connected, there are support pillars every few kilometers, each more magnificent than a mountain, with a diameter of at least dozens of kilometers, even up to a hundred kilometers, so thereās no need to worry about that."
Xu Xin imagined it.
A pillar with a diameter of a hundred kilometers and a vertical height of only three thousand meters...
Calling them "support pillars" might be less fitting than calling them "support plates."
The Earthās crust... stepping stones?
He looked around.
Unfortunately, in this underground world, only this area had a bit of light, sourced from where the main vine bundle connects to the dome.
Further away was pitch black.
Even if he ate a red berry, he still couldnāt see far.
"No need to look around. Thereās none here," Xu Ying reminded him. "These āsupport pillars,ā if calculated by surface distance, are at least two thousand kilometers apart."
The reason for saying "by surface distance" is because underground distance is different from surface distance.
The underground world is closer to the Earthās core, so if you calculate the underground worldās distance, it would be shorter than 2000 kilometers.
"Two thousand kilometers? Thatās really far..." Li Wenxi was surprised. "If Earth didnāt become larger, Iām afraid there wouldnāt be many pillars at all."
"Thatās not the case," Xu Xin calculated. "The equator alone exceeds forty thousand kilometers, so there could be around twenty pillars along the equator, and more across the entire planet."
Currently, the Earthās surface area has expanded by a hundredfold.
Although each pillar is two thousand kilometers apart, very far away, they are actually very densely distributed considering the current size of the Earth.
Itās no wonder that the entire crust and the world above could be supported.
Xu Ying pointed upwards: "And here is a position we specifically selected. Here, the distance to each āsupport pillarā is very far; the nearest one is nearly a thousand kilometers away."
"Why choose a location furthest from each support pillar?" Xu Xin wondered. "Intentionally far from the support pillars?"
"Exactly!" Li Wenxi imagined the shape of the support pillars. "If we plant the World Tree on a āsupport pillar,ā wouldnāt its root system extend downward? Such a World Tree should be stronger!"
"Thatās true," Xu Ying pursed her lips. "But if we can think of it, wouldnāt the opposing side think of it as well."
"The opposing side... ah." Xu Xin immediately understood: "Youāre saying those alien invaders plant their World Tree on the āsupport pillarsā?"
Xu Ying nodded: "Yes, thatās right. A World Tree planted on the āsupport pillarsā would not only influence large areas on the surface but also allow its roots to extend downward from the āsupport pillars,ā continuously spreading across the underground worldās surface. In such circumstances, just one World Tree would allow them to easily control vast areas of both the above-ground world and the underground world."
Speaking this way, she carried a hint of helplessness in her tone: "This is how these alien invaders occupy Earth."
"They first developed portable World Tree seeds, took them to the support pillars, and planted them. This way, their dominion could expand across both worlds, and now, they have already occupied half of Earth."