At 1:23 a.m. on April 26, 1986, Reactor 4 of the Chernobyl nuclear power plant exploded, following a disastrously ill-judged systems test by undertrained technicians. As surplus energy surged through the reactor, its core combusted, immediately killing nearby workers and exposing others to deadly levels of radiation. In the nearby town of Prypiat, Ukraine, people woke up to respiratory distress and nausea. Emergency response workers encased the reactor in a concrete sarcophagus and, unprepared for exposure to radioactivity, became stricken with severe symptoms of radiation poisoning. Tens of thousands of Soviet citizens filed into Chernobyl to help, considering it their patriotic duty; all were exposed to dangerous levels of radiation with no warning from the government. It took two days for the explosion to be announced, in vague terms, on the national news; not until Sweden discovered a radiation cloud that had drifted across Europe was the true extent of the Chernobyl explosion revealed.

Reactor 4 may not have been the only thing that exploded that day. Fewer than six years elapsed between the meltdown at Chernobyl and the formal dissolution of the Soviet Union—six years marked by suspicion of government, dissatisfaction with public safety, and demands for greater transparency. Could Chernobyl have caused the first, most fundamental crack in the Soviet state and led to its collapse?

That might sound like an audacious proposal, but it’s been advanced by none other than the man who oversaw the dismantling of the USSR, Mikhail Gorbachev. He states flatly that the Chernobyl explosion was “perhaps the real cause of the collapse of the Soviet Union.” According to Gorbachev, the Chernobyl explosion was a “turning point” that “opened the possibility of much greater freedom of expression, to the point that the system as we knew it could no longer continue.” Gorbachev introduced his policy of glasnost, or “openness” of ideas and expression, not long before the Chernobyl explosion. It was his remedy for widespread censorship and government secrecy. To Gorbachev, Chernobyl proved the wisdom and necessity of glasnost. The explosion and attendant tumult, he claims, “made absolutely clear how important it was to continue the policy of glasnost.”

Gorbachev’s laudable dedication to glasnost may have set the state on a path toward destruction. Sovietologists “don’t like monocausal explanations” of the fall of the USSR, said Michael David-Fox, a professor of Russian and Soviet history at Georgetown University. Still, “there’s a case to be made” that Chernobyl occurred early enough in Gorbachev’s first phase of glasnost to hasten the process and eventually drive the state into the ground.

Few Westerners were convinced that the new leader’s reforms would be serious in 1985 and 1986. Yet by 1987, the year following Chernobyl, glasnost had taken hold of Soviet society, with sudden openness dominating the press and the public forum. Outrage over the catastrophe began to spread among even loyal citizens who had never questioned the infallibility of their government. A more authoritarian leader might still have been able to crack down on complaints about Chernobyl at this fairly early date, but Gorbachev, fighting a political battle as a reformer, chose to maintain glasnost while casting censorious conservatives as nemeses of liberty and wooing the intelligentsia. Gorbachev needed this latter group’s support to achieve his reforms and hold back hardliners, so he accepted their barrage of condemnation toward the government. To keep the intelligentsia as allies, in other words, Gorbachev had to accept them as critics.

The intelligentsia’s complaints trickled down through much of the population. This opened the door to comparison with the West, a toxic line of thought in this famously closed society. Soviets had been told for decades they were the best in the world—at everything. Through the mid-1980s, they still believed they were a major superpower, facing only the United States as serious competition. When information about Chernobyl and the public health crisis leaked, though, Soviet citizens realized that their government and industries were startlingly incompetent.

Radioactivity was a novel menace for Soviets. Radiation poisoning was personal and permanent, made all the more frightening by its mysteriousness. (Apprehension over the radioactive fallout from Chernobyl extended beyond the USSR’s borders; across Europe, the anti-nuclear movement boomed in popularity, converting a side issue into a major cause for environmental activists.) A toxin imperceptible to the eye is as unavoidable as it is terrifying, yet Soviets were unable to rely upon their ostensibly dependable government to inform and protect them. As panicked citizens kindled one another’s fright and horror, the regime lost any remaining control over the public discourse. Glasnost had, in a few short months, careened out of control, fueled by frenzied dismay over the perils of radiation.

Did Gorbachev realize his visionary reforms were undercutting his regime’s legitimacy? This seems highly unlikely. Kate Brown, a Soviet nuclear historian at the University of Maryland, Baltimore County, believes that Gorbachev was a true believer in the Soviet system—and in the ability of free expression to solve the state’s myriad crises.*

“Gorbachev did really imagine an honest discussion of the country’s problems in the press and workplaces,” Brown said. But he also likely saw glasnost as an incremental process. The meltdown in Chernobyl, in contrast, was sensational and uncontainable. It wasn’t a systemic issue to be discussed in editorial pages and offices; it was a terrifying, deadly mistake caused by a poorly built and ineptly run facility and exacerbated by a slow, unsophisticated response.

Chernobyl, then, represented a fundamental shift in the relationship between the Soviet citizenry and the state. Before the explosion, most Soviets were not discontented dissidents; they believed in the Soviet system, forgave its flaws, and hoped for a better future within its confines. But after Chernobyl, the system seemed potentially unredeemable—and actively dangerous. In the early days of glasnost, stories of Stalin’s mass murders decades earlier slowly bubbled to the fore, but those generally receded, so far removed were they from everyday life. After Chernobyl, though, every citizen’s safety was at stake.

The explosion rained radioactive isotopes across the farmlands of northern Ukraine, contaminating crops, grazing areas, and livestock. “You had to ask the question, ‘What’s in my kid’s milk?’ ” Brown noted. “What’s in my food?” For many, the answer was radiation. In an attempt to dilute contaminated meat, the Soviet government mixed small amounts of radiation-tainted cow carcasses with noncontaminated beef then shipped the mix across the country. Horror stories of radiation spread; victims fled the area and then told their stories on street corners and in town halls. Testimonies appeared in books and newspapers, often with a note of criticism toward the regime’s response. The evidence was simply overwhelming: The once-hallowed regime was utterly fallible, and in this moment of crisis, it had failed.

The USSR would limp on for several more years before collapsing. One of history’s largest empires disappeared from the Earth on Christmas Day, 1991.

Though the regime is gone, Chernobyl remains—a ghost town and unintentional wildlife preserve packed with elk, wolves, wild boar, and nuclear hot spots. Its ghost lingers in northern Ukraine: The Ferris wheel from an amusement park set to open one week following the explosion sits frozen in time; children’s dolls haunt dark corners of abandoned houses; a massive indoor swimming pool sits empty, echoing the winds.

The tragedy that occurred here started as a horrible accident and then got worse as the regime first sat on its hands and then flailed them helplessly. It might have been the impetus for the downfall of the entire Soviet project. But the Chernobyl of 2013 does not look like the start of a major political upheaval. If anything, it looks more like a graveyard. Perhaps that’s only fitting. If Gorbachev’s theory is correct, Chernobyl represents the final resting place of the Soviet state, a government undone by the power of free expression. It took only one nuclear explosion to unleash that power.

Update, Jan. 28, 2013: This sentence was revised to clarify what campus of the University of Maryland system Kate Brown works at. (Return to the revised sentence.)