On July 16, 2186, the Moon will align perfectly between the Earth and the Sun, creating an eclipse without historical precedent. Unless he eccentric millionaire determined to rejuvenate succeed, none of us will be here to see it. But our descendants will want to spend that day somewhere in Colombia, Venezuela or Guyana.
7 minutes and 29 seconds. The longest total solar eclipse in history will exceed by almost two seconds the duration of the one that held the record until now: the eclipse of June 15, 743 BC, which reached a totality of 7 minutes and 27 seconds over the Indian Ocean, near present-day Kenya and Somalia.
No eclipse will have lasted as long from before 4000 BCand none will do so until after 8000 AD, so we can be sure that it will be a truly unique astronomical event. The longest total solar eclipse in an interval of 12,000 years.
The Moon will darken South America. The historic solar eclipse of 7 minutes and 29 seconds will not occur on land: the strip of totality will reach its longest duration over the Atlantic Ocean.
However, northern South America will also enjoy extraordinarily long totalities. Especially in Colombia (from Cali to Puerto Ayacucho), Venezuela (from the Orinoco to Imataca) and Guyana (in the entire northern half of the country, including Georgetown).
The show will not be limited to that narrow strip. Virtually all of South America, including the entire Brazilian territory, will be able to observe a partial eclipse of great magnitude. The eclipse will also be partially visible from Mexico to Paraguay, and west of Africa. In Spain it will barely touch the Canary Islands at sunset.
Why will it last so long? The reason for this extreme duration is a “perfect storm” in the positions of the three bodies. The Earth will be at its furthest point from the Sun (its aphelion), which will make the solar disk appear slightly smaller.
The Moon, for its part, will be at its closest point to the Earth (its perigee), so its apparent disk will be larger. And finally, the path of the eclipse will pass very close to the Earth’s equator. This combination maximizes the time it takes for the Moon’s shadow to sweep across the Earth’s surface.
How are we so sure? Eclipse prediction is one of the most successful feats of computational astronomy. Scientists feed their supercomputers the current positions and velocities of the Earth and Moon, and then use Newton’s laws of motion to figure out what will happen several centuries or even millennia from now.
These algorithms are actually models that integrate gravitational equations to project their positions into the future. And they do it with astonishing precision, usually within a margin of error of less than a minute over hundreds of years.
First cousin of the great eclipse of 2024. The total solar eclipse of 2186 belongs to the same “lineage” as the Great North American Eclipse of April 8, 2024, the Saros cycle 139. A Saros cycle is a period of approximately 18 years, 11 days and 8 hours, after which the Sun-Earth-Moon geometry is repeated in an almost identical way, producing a very similar eclipse but displaced about 120 degrees to the west.
Discussions among eclipse enthusiasts are already fantasizing about what the hunt for this event will be like in 2186. There is talk of fleets of cruise ships positioned in the Atlantic and flights in hypersonic planes to chase the shadow and further extend the experience of totality.
Although we will not see the millennium eclipse, there is no need to wait that long to experience a totality: on August 12, 2026, Spain will chain the first of three Iberian eclipses. They are not the “wonders of the cosmos”, but we cannot complain.
A version of this article was published in July 2025
Image | THAT
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