Should France rebuild Notre Dame exactly as it was?

The lack of tall, strong oak trees poses something of a problem for the restoration effort.

Should France rebuild Notre Dame exactly as it was?
Photo credit: Chesnot / Getty Images
  • A fire destroyed Notre Dame's 115-foot roof on April 15, immediately sparking a debate on how France should restore the cathedral.
  • Some argue that it should be rebuilt to its original specifications, while others say alternate materials would be a better options.
  • The debate calls to mind the philosophical thought experiment known as "The Ship of Theseus."

French President Emmanuel Macron has promised that France will rebuild Notre Dame, whose roof caught fire on April 15, within five years. However, some experts say it could take longer, even decades. Either way, it's a virtual certainty that the 850-year-old cathedral will be restored in time. The question is how, and with what materials?

Some argue the roof should be restored as closely as possible to its original state.

"We'll use modern methods, but it should be done by the books," Mechtild Rössler, the director of the Unesco World Heritage Center, told Business Insider.

However, one major problem is that France probably doesn't have enough tall oak trees to restore the roof as it was. Even in the 13th century, it wasn't exactly easy to find the 3,000 tall oak trees, some of which were up to 400 years old. French forests have only dwindled since then.

However, the insurance firm Groupama has pledged 1,300 oak trees, which are about 100 years old, from forests it owns in Normandy. No matter, though.

"The ability to find around 3,000 more big, strong trees in the next two decades is going to be tricky," medieval historian Dr. Emily Guerry told CBS News, adding that the Baltic might have enough suitable oak trees.

Work Takes Place On Notre Dame Cathedral After Devastating Fire. Photo credit: by Chesnot / Getty Images

But even this might upset some of the purists who say the new roof should be made from oak from the forests of Normandy, like the original construction. To others, rebuilding the roof with another material — perhaps iron — makes more sense, consider it'd decrease the chances of the roof catching fire again in the future.

"I doubt they'll use wood," Carolyn Malone, a professor of art history and gothic architecture at the University of Southern California, told Business Insider.

Still another concern is restoration expertise.

"We need carpenters with the skill set to spot the right trees, treat them properly, and then erect them into this beautiful fan-like fabric," Guerry told CBS News. "These skills aren't really common in the modern age, but I'm sure there are really talented people out there that will be hurrying to do this job for Paris."

At the heart of the restoration debate is a clash between the "ancients and moderns," as art historian Dr. Jean-Michel Leniaud described to The Art Newspaper. Those in the latter camp might be more inclined to pursue a pragmatic restoration approach, in which it wouldn't be considered a "betrayal" of French culture to rebuild the roof with a visibly modern touch.

The Ship of Theseus

The debate calls to mind the Ship of Theseus philosophical thought experiment, part of which asks:

"... suppose that the famous ship sailed by the hero Theseus in a great battle has been kept in a harbour as a museum piece. As the years go by some of the wooden parts begin to rot and are replaced by new ones. After a century or so, all of the parts have been replaced. Is the 'restored' ship still the same object as the original?"

If the answer is no, does that mean France should be any less concerned with rebuilding the cathedral to its exact original specifications? If the answer is no, should the lovers of Notre Dame take this tragedy as an opportunity to imbue a bit of modernity to the iconic cathedral, both in terms of materials and design?

This is what aliens would 'hear' if they flew by Earth

A Mercury-bound spacecraft's noisy flyby of our home planet.

Image source: sdecoret on Shutterstock/ESA/Big Think
Surprising Science
  • There is no sound in space, but if there was, this is what it might sound like passing by Earth.
  • A spacecraft bound for Mercury recorded data while swinging around our planet, and that data was converted into sound.
  • Yes, in space no one can hear you scream, but this is still some chill stuff.

First off, let's be clear what we mean by "hear" here. (Here, here!)

Sound, as we know it, requires air. What our ears capture is actually oscillating waves of fluctuating air pressure. Cilia, fibers in our ears, respond to these fluctuations by firing off corresponding clusters of tones at different pitches to our brains. This is what we perceive as sound.

All of which is to say, sound requires air, and space is notoriously void of that. So, in terms of human-perceivable sound, it's silent out there. Nonetheless, there can be cyclical events in space — such as oscillating values in streams of captured data — that can be mapped to pitches, and thus made audible.

BepiColombo

Image source: European Space Agency

The European Space Agency's BepiColombo spacecraft took off from Kourou, French Guyana on October 20, 2019, on its way to Mercury. To reduce its speed for the proper trajectory to Mercury, BepiColombo executed a "gravity-assist flyby," slinging itself around the Earth before leaving home. Over the course of its 34-minute flyby, its two data recorders captured five data sets that Italy's National Institute for Astrophysics (INAF) enhanced and converted into sound waves.

Into and out of Earth's shadow

In April, BepiColombo began its closest approach to Earth, ranging from 256,393 kilometers (159,315 miles) to 129,488 kilometers (80,460 miles) away. The audio above starts as BepiColombo begins to sneak into the Earth's shadow facing away from the sun.

The data was captured by BepiColombo's Italian Spring Accelerometer (ISA) instrument. Says Carmelo Magnafico of the ISA team, "When the spacecraft enters the shadow and the force of the Sun disappears, we can hear a slight vibration. The solar panels, previously flexed by the Sun, then find a new balance. Upon exiting the shadow, we can hear the effect again."

In addition to making for some cool sounds, the phenomenon allowed the ISA team to confirm just how sensitive their instrument is. "This is an extraordinary situation," says Carmelo. "Since we started the cruise, we have only been in direct sunshine, so we did not have the possibility to check effectively whether our instrument is measuring the variations of the force of the sunlight."

When the craft arrives at Mercury, the ISA will be tasked with studying the planets gravity.

Magentosphere melody

The second clip is derived from data captured by BepiColombo's MPO-MAG magnetometer, AKA MERMAG, as the craft traveled through Earth's magnetosphere, the area surrounding the planet that's determined by the its magnetic field.

BepiColombo eventually entered the hellish mangentosheath, the region battered by cosmic plasma from the sun before the craft passed into the relatively peaceful magentopause that marks the transition between the magnetosphere and Earth's own magnetic field.

MERMAG will map Mercury's magnetosphere, as well as the magnetic state of the planet's interior. As a secondary objective, it will assess the interaction of the solar wind, Mercury's magnetic field, and the planet, analyzing the dynamics of the magnetosphere and its interaction with Mercury.

Recording session over, BepiColombo is now slipping through space silently with its arrival at Mercury planned for 2025.

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Photo by Reinhart Julian on Unsplash
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Image: u/curiouskip, reproduced with kind permission.
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