Cheng Xin

''Death's End'' () is a science fiction novel by the Chinese writer Liu Cixin. It is the third novel in the trilogy titled ''Remembrance of Earth's Past'', following the Hugo Award-winning novel '' The Three-Body Problem'' and its sequel, '' The Dark Forest''. The original Chinese version was published in 2010. Ken Liu translated the English edition in 2016. It was a finalist for the 2017 Hugo Award for Best Novel and winner of the 2017 Locus Award for Best Science Fiction Novel.

Plot

In the 2010s, the early years of the Trisolar Crisis, young aerospace engineer Cheng Xin is recruited by the Planetary Intelligence Agency (PIA) under its coldly rational chief Thomas Wade. They initiate the "Staircase Project", which attempts to send a human spy at relativistic speed to the approaching Trisolaran invasion fleet. Technological limitations for achieving such speed restricts the payload to a human brain, which the PIA hopes the Trisolarans can revive upon its reception.

Cheng requests an old university classmate afflicted by terminal cancer, Yun Tianming, to donate his brain. Unbeknownst to Cheng, Yun harbors romantic feelings for her, and he has previously purchased for Cheng the rights to distant star DX3906 in a United Nations-organized fundraiser. After Yun's brain is launched, Cheng enters hibernation to await the Staircase Project's outcome.

Some 200 years later, Cheng wakes from hibernation and becomes immensely wealthy by selling her rights to DX3906. By this time, Earth and Trisolaris have entered a truce due to the dark forest deterrence. The deterrence is enforced by the "Swordholder": an individual who, should Trisolaris violate the truce, is authorized to send a cosmic broadcast containing Trisolaris' location, which would invite the mutual destruction of both Trisolaris and Earth by third parties. Cheng's newfound fame results in her election to succeed the aging Luo Ji, the inaugural Swordholder who established the dark forest deterrence. However, immediately after the Swordholder succession, Trisolaris launches an attack on Earth's cosmic broadcast abilities, gambling correctly that Cheng will refuse to activate the deterrence.

With Earth-based deterrence systems neutralized, Trisolaris announces a renewed invasion effort. However, one remaining functional broadcast system remains onboard the starship ''Gravity'', which was initially sent to deep space to capture the fugitive ship ''Blue Space''. Trisolaris' attempt to attack ''Gravity'' is thwarted by ''Blue Space's'' crew, who exploit the fourth dimension to do so. Believing Earth to be lost, the two ships' combined crew activate ''Gravitys broadcast system as revenge against Trisolaris' treachery, resulting in Trisolaris' destruction by a third party. Understanding that Earth is also at risk of imminent destruction due to its relative proximity to Trisolaris, the surviving Trisolaran fleets abandon their invasion attempt.

Having intercepted Yun's brain and revived him, the Trisolarans permit Cheng to converse with him. He sends a coded message in the form of a fairy tale, containing survival advice for humanity. Three survival strategies are created with this information:
* The "Bunker Project": After Trisolaris' destruction, Earth observed that several ships survived by hiding behind other stars in the system. Humanity begins building space cities in the gas giants' shadows to survive the Sun's destruction.
* The development of lightspeed travel: Thanks to clues from Yun, lightspeed propulsion is developed by decreasing the energy of spacetime behind the ship. However, its visibility and danger of attracting attention lead to it being banned.
* The development of a "black domain", a region of space with decreased lightspeed that prevents anything from leaving. This acts as a sign of harmlessness, since the civilization inside the domain cannot affect anything outside.

During the next few decades, as Cheng hibernates, humanity builds several space cities according to the Bunker Project, but progress on the Black Domain Plan is stalled. Cheng is awoken as Wade has successfully but illegally developed the backbone technology for lightspeed travel, and requests Cheng's permission to proceed, which she denies. Wade is executed for his transgressions as Cheng re-enters hibernation.

Several decades later, an unknown hostile alien race launches the anticipated dark-forest attack. However, instead of destroying the sun, they send a weapon which progressively collapses the three-dimensional Solar System into two dimensions, rendering the bunkers useless. As the escape velocity from the dimensional attack is lightspeed, the vast majority of humanity is killed due to the lack of lightspeed travel technology. Cheng and her aide AA are awoken amidst the attack. They visit Luo Ji on Pluto, who informs them their spaceship contains the only surviving lightspeed engine from Wade's experiments. Cheng and AA escape the attack, becoming the only humans remaining in the universe alongside Yun and the crews of ''Gravity'' and ''Blue Space''.

286 years later, Cheng and AA arrive at the distant star DX3906's "Planet Blue", though the voyage passes quickly for them due to time dilation from lightspeed travel. There they encounter Guan Yifan, a civilian cosmologist on ''Gravity'', who explains that the two ships' crew have founded several interstellar societies. Leaving AA on Planet Blue, Cheng and Guan fly to the nearby "Planet Gray", where they discover several unstable seed elements of a black domain that grows to encompass the entire DX3906 system. The significantly decreased lightspeed within the black domain cause Cheng and Guan to experience severe time dilation; almost 19 million years have passed in Planet Blue's reference frame by the time they return to Planet Blue.

In their absence, Yun had visited Planet Blue to deliver "Universe 647": a Trisolaran-constructed self-contained micro-universe that exists outside of the conventional timeline. Cheng and Guan live in Universe 647's pastorally decorated interior, hoping to outlast the main universe and observe its rebirth in a Big Bounce. After a period of idyllic living, they receive a message from the main universe, stating that the presence of micro-universes deprives the main universe of mass, disrupting its cycle of expansion, collapse and rebirth. Feeling a moral responsibility to the universe, they re-integrate Universe 647 with the main universe before departing on interstellar travel.

Key characters

;Cheng Xin ()
:Aerospace engineer from the early 21st century, the proposer of the Staircase Project, the second Swordholder, and the owner of the DX3906 star system.
;Yun Tianming ()
:Cheng Xin's university classmate and secret admirer. His brain is sent into space and captured by the Trisolaran fleet, who clones his body and returns him to life.
;Thomas Wade ()
:The cold-hearted and ruthlessly rational PIA Chief who later leads an effort to create lightspeed propulsion.
;Ai AA ()
:Astronomer from the Deterrence Era; Cheng Xin's aide, friend and travelling companion.
;Luo Ji ()
:Cosmic sociologist, former Wallfacer, and the inaugural Swordholder. Returning character from '' The Dark Forest''.
;Guan Yifan ()
:Civilian astronomer aboard the spaceship ''Gravity'' and Cheng's companion after the dark forest strike on the Solar System.

Awards

References

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2010 science fiction novels
Novels by Liu Cixin
Novels about alien invasions
Fiction about suspended animation
2010 Chinese novels
Novels about the end of the universe
Locus Award–winning works