Voyager I will reach a nearby star sometime around the year 42,013 A.D.
That’s not Voyager 1’s mission, though. The primary mission was to visit the planets, and even for secondary missions, I don’t think there were any plans beyond crossing the heliopause. By the time it reaches the vicinity of any other star, it’ll just be a chunk of dead space debris. One might as well consider the “completion date” of a building to be the time when it finally collapses to rubble.
Yeah, that’s taking longer than they thought. 
I was thinking about the pitch drop experimentwhich started in 1927 and might have another century to run, but most of these beat that to hell and back.
Are any eastern temples or monasteries actually doing something like the Tower of Hanoi, which will take cosmic cycles to complete? Not that necessarily but something equivalent?
Something else about the Sagrada Familia: while the main nave is barely complete and has been used very few times, Masses have been ongoing in the crypt* for decades, and it was made a parish church in 1930. So it’s not complete but it has been serving as a church for 85 years.
- In this case, crypt means “underground place” or “basement”, not “burial place”. There are a few people buried there but that’s not its main purpose.
The most amazing thing about Water Tunnel No. 3 is that it’s actually a little ahead of schedule.
Completion of construction on the Gulf Freeway in Houston. It was started in 1948 and to this day, construction is still occurring somewhere on it. And there doesn’t appear to be an end date for the construction, so apparently it will continue until the Earth is consumed by the Sun or something like that.
Are there any components in Voyager that have a limited lifespan? That is, could it theoretically still be working by then?
The Voyagers (and Pioneers and the Pluto mission New Horizons) are powered by Plutonium 238 radioisotope thermoelectric generators. Pu-238 has a half-life of 87.7 years, so no. According to Wikipedia the Voyagers should have enough power from the RTGs to continue its current experiments which still communicate data back to Earth until 2025.
Thanks. I thought they were partially solar powered, but considering where they’re going that wouldn’t have made sense.
While not as sexy or as long-lasting as the other projects noted here, I have to bring up the construction of the Cathedral of St’ John the Divine in new York City.
Construction began with the laying of the cornerstone on Dec. 27, 1892 (St. John’s Day). The church was opened for use in November 1941. Construction has proceeded in fits and starts, with them often having to establish schools to teach people the arts of Gothic design or medieval stonecutting. The western façade was finished in 1997, and no substantial exterior work has been done since then. In 2001 a fire did damage to the north Transept. The choir parapet was completed the same year. In 2005 they performed restoration of the interior, and rededicated the church in 2008.
God knows when it will be finished (if ever). I recall an old Ripley’s Believe it or Not cartoon that told of a niche left to be filled with a sculpture of the most notable person of the 20th century. I suspect t they thought the project would be finished before the end of the century. I hope they left a space for the 21st century. And maybe the 22nd.
I just ordered a sandwich at the Creekside Deli. I’ve got to be somewhere in the running.
It’s done now, but work on Stonehenge lasted ~1500 years. Not continuously, of course.
The Cathedral of Milan took 600 years to complete. Milan Cathedral - Wikipedia
I got curious and Wikipedia reports that the 20th century figure was put already in place and they are 4!: