For decades, holograms have been seen largely on the screen, in sci-fi movies and TV shows like "Star Wars" and "Star Trek."
The famed holodeck on "Star Trek" was used on a variety of the Federation star ships and was mostly seen when someone had to visit the sick bay as part of the "Emergency Medical Holographic program" (EMH). A 3-dimensional transparent image of someone would suddenly appear—but it was also something that you could interact with and ask questions. In "Star Wars" there was a similar type of holographic technology (usually projected from some type of handheld device). One of the more popular instances is when R2D2 projected a 3-dimensional image of Princess Leia pleading for help from Obi-Wan Kenobi.
Hollywood makes this type of technology look easy, but in the real world, holographic technology has usually resulted in relatively primitive designs. We have experimented with a variety of different methods—some successful and some not so successful. Back in July, a team at Tokyo University was one of the first groups to successfully create a system of touchable holograms. If you had a hologram of a small red ball, for example, you could essentially interact with it.. The ball would know when it was near your hand and would appear to bounce off of it. When this technology first made news, it was compared to a primitive version of the holographic computer desktop interface in "Minority Report."
But now another major development in holographic technology is making headlines. A new device has been created that can transmit 3-dimensional images in close to real time. This could result in major advances in holographic tele-presence technologies. For example, I could conduct a keynote speech in Tokyo from the comfort of my own home—a 3D, high-resolution, full size image of my body could be projected on stage in front of a live audience over 6,000 miles away. If you are familiar with the work of my colleague, Ray Kurzweil, you may be aware that he sometimes gives "virtual lectures" where a 3D image of him is projected into a special podium. This tele-presence system, designed by Teleportec, has to have two running systems: one in Ray's office, and one on the special podium that displays the image. This allows him to conduct lectures in real time and interact with the audience on the other end. He can even making eye contact with students in the audience. (Image below: Ray Kurzweil using the Teleportec Video Conferencing Technology)
But now a small group of researchers from the University of Arizona have unveiled the fastest 3D motion hologram. What makes this different than say watching "AVATAR" in an IMAX 3D theater is one word: glasses. This group of researchers have successfully demonstrated a display screen which presents an image which is viewable from all sides without 3D glasses. They have done all this with the use of 16 cameras allowing them to create a 45-degree 3-dimensional image. Each camera takes a different snapshot (360 degrees) and the more cameras that are used, the more refined the resolution of the image. In the past, there have always been issues with the refresh rates of the image. The group's previous version only was able to render a new image about every four minutes. The new system refreshes ever two seconds, thanks to a special type of photorefractive material on the screen which reacts chemically to the lasers used to create the holographic images. All of the images that each of the cameras record is played back to the observer using fast-pulsed laser beams which then create holographic pixels "hogels" which show up on the special photo refractive polymer.
Like every other advance in technology, it will take some time to perfect before it's brought to market but it seems that we may not have to wait too long. The current system only displays in one color, but the University is stating that perhaps in another decade or so, commercially viable holographic television screens could start hitting the shelves.
The applications for such a system could essentially change our daily lives. The lead researcher of the development, Nassar Peyghambarian states that "It can be a game changer in some industries." He also states that "the first that come to mind are product demonstrations and giving the ability to actually see a product in 3-D before the money is spent to build it. It also could, for instance, immerse prospective tenants in their new office suite or show hotel mavens the interior decorator's vision for their remodeled rooms." Some other applications could include telemedicine, 3D mapping technologies, entertainment, remote guidance during emergency situations, remote video conferencing, manufacturing, and a myriad of others.
--- My webmaster, Michael Phillips, recently conducted an interview with Assistant Research Professor & first author on the paper submitted to Nature, Pierre-Alexandre Blanche, about the recent developments.
PAB: As a physicist, I was attracted by optics as a new frontier. We mostly apprehend the world thanks to our sight and when we probe the universe it isalso mostly thanks to optics (i.e. telescopes). Optics is the infinitely large, and the infinitely small with microscope, but also ultra fast with photonics that multiply the speed of electronics by several factors. Optics is beautiful like rainbows, and dramatics as the Hubble space telescope images. Finely, holography is manipulating the light and tailoring it as a sculptor will do with marble.
PAB: We have already demonstrated the feasibility of multicolor holograms in the same article. We did not implement multicolor into the telepresence system yet since this setup is constantly remodeled to experiment new ideas and applications. If there is interest, it sure can be done.
PAB: In the next 5 years, this is our goal to demonstrate different feasibilities for that technology. The most important one is video-rate, we want to be able to record our holograms at a rate comparable to television so the viewer de not experience any lag or flickering; and we have already traced the roadmap to achieve it. We also have different setup in mind like a tabletop display where the viewer can look around and see the object according 360°. We are working on that one right now.
PAB: We see the development of this technology in two steps. First we want to develop systems that correspond to very specialized application like medical imaging and military imaging. All the corner stones for such systems have been laid out and there is no to much breakthrough that need to be discovered for this to happen. It is more about refinement. Next we can think about more general audience when image speed achieve video rate and the size of the system can be shrunk thanks to new laser technology and better polymer performance. Telepresence for large conference rooms is one of those applications. Ultimately, yes we envision a holographic television in lets say 15 years.
PAB: A lot of work! What we reported in our publication are land marks but certainly not an end per se. We are not resting in our laurels, and since we submitted our manuscript to Nature, we already made some progresses in several areas.
Excerpt from a 19th century map of the Paris Catacombs, showing the labyrinthine layout underground (in color) beneath the straight-lined structures on the surface (in grey).
Ancient mining areas below Paris for limestone (red) and gypsum (green).Credit: Émile Gérards (1859–1920) / Public domain
"If you're brave enough to try, you might be able to catch a train from UnLondon to Parisn't, or No York, or Helsunki, or Lost Angeles, or Sans Francisco, or Hong Gone, or Romeless."
China Miéville's fantasy novel Un Lun Dun is set in an eerie mirror version of London. In it, he hints that other cities have similar doubles. On the list that he offhandedly rattles off, Paris stands out. Because the City of Light really does have a twisted sister. Below Paris Overground is Paris Underground, the City of Darkness.
Most people will have heard of the Catacombs of Paris: subterranean charnel houses for the bones of around six million dead Parisians. They are one of the French capital's most famous tourist attractions – and undoubtedly its grisliest.
But they constitute only a small fragment of what the locals themselves call les carrières de Paris ("the mines of Paris"), a collection of tunnels and galleries up to 300 km (185 miles) long, most of which are off-limits to the public, yet eagerly explored by so-called cataphiles.
The Grand Réseau Sud ("Great Southern Network") takes up around 200 km beneath the 5th, 6th, 14th, and 15th arrondissements (administrative districts), all south of the river Seine. Smaller networks run beneath the 12th, 13th, and 16th arrondissements. How did they get there?
Paris stone and plaster of Paris
It all starts with geology. Sediments left behind by ancient seas created large deposits of limestone in the south of the city, mostly south of the Seine; and gypsum in the north, particularly in the hills of Montmartre and Ménilmontant. Highly sought after as building materials, both have been mined since Roman times.
The limestone is also known as Lutetian limestone (Lutetia is the Latin name for ancient Paris) or simply "Paris stone." It has been used for many famous Paris landmarks, including the Louvre and the grand buildings erected during Georges-Eugène Haussmann's large-scale remodelling of the city in the mid-19th century. The stone's warm, yellowish color provides visual unity and a bright elegance to the city.
The fine-powdered gypsum of northern Paris, used for making quick-setting plaster, was so famed for its quality that "plaster of Paris" is still used as a term of distinction. However, as gypsum is very soluble in water, the underground cavities left by its extraction were extremely vulnerable to collapse.
Like living on top of a rotting tooth: subsidence starts far below the surface, but it can destroy your house.Credit : Delavanne Avocats
In previous centuries, a road would occasionally open up to swallow a chariot, or even a whole house would disappear down a sinkhole. In 1778, a catastrophic subsidence in Ménilmontant killed seven. That's why the Montmartre gypsum quarries were dynamited rather than just left as they were. The remaining gypsum caves were to be filled up with concrete.
The official body governing Paris down below is the Inspection Générale des Carrières (IGC), founded in the late 1770s by King Louis XVI. The IGC was tasked with mapping and, where needed, propping up the current and ancient (and sometimes forgotten) mining corridors and galleries hiding beneath Paris.
A delightful hiding place
Also around that time, the dead of Paris were getting in the way of the living. At the end of the 18th century, their final destination consisted of about 200 small cemeteries, scattered throughout the city — all bursting at the seams, so to speak. There was no room to bury the newly dead, and the previously departed were fouling up both the water and air around their respective churchyards.
Something radical had to happen. And it did. From 1785 until 1814, the smaller cemeteries were emptied of their bones, which were transported with full funerary pomp to their final resting place in the ancient limestone quarries at Tombe-Issoire. Three large and modern cemeteries were opened to receive the remains of subsequent generations of Parisians: Montparnasse, Père-Lachaise, and Passy.
Who says stacking skulls and bones can't be fun?Credit: Rijin via Wikimedia and licensed under CC BY-SA 4.0
The six million dead Parisians in the Catacombs, from all corners of the capital and across many centuries, together form the world's largest necropolis — their now anonymized skulls and bones methodically stacked, occasionally into whimsical patterns. The Catacombs are fashioned into a memorial to the brevity of life. The message above the entrance reads: Arrête! C'est ici l'empire de la Mort. ("Halt! This is the empire of Death.")
That has not stopped the Catacombs, accessible via a side door to a classicist building on the Avenue du Colonel Henri Rol-Tanguy, making just about every Top 20 list of things to see in Paris.
An underground economy
However, while the Catacombs certainly are the most famous part of the centuries-old network beneath Paris, and in non-pandemic times draw thousands of tourists each day, they constitute just 1.7 km (1 mile) of the 300-km (185-mile) tunneling total.
Subterranean Paris wasn't just used for mining and storing dead people. In the 17th century, Carthusian monks converted the ancient quarries under their monastery into distilleries for the green or yellow liqueur that still carries their name, chartreuse.
Because the mines generally keep a constant cool temperature of around 15° C (60° F), they were also ideal for brewing beer, as happened on a large scale from the end of the 17th century until well into the 20th century. Several caves were dug especially for establishing breweries, and not just because of the ambient temperature: going underground allowed brewers to remain close to their customers without having to pay a premium for real estate up top.
Overview of the Paris Catacombs.Credit: Inspection Générale des Carrières, 1857 / Public domain.
At the end of the 19th century, the underground breweries of the 14th arrondissement alone produced more than a million hectoliters (22 million gallons) per year. One of the most famous of Paris' underground breweries, Dumesnil, stayed in operation until the late 1960s.
In that decade, the network of corridors and galleries south of the Seine, long since abandoned by miners, became the unofficial playground for the young people of Paris. They explored the fantastical world beneath their feet, in some cases via entry points located in their very schools. Fascinated, these cataphiles ("catacomb lovers") read up on old books, explored the subterranean labyrinth, and drew up schematics that were passed around among fellow initiates as reverently as treasure maps.
As Robert Macfarlane writes in Underland, Paris-beneath-their-feet became "a place where people might slip into different identities, assume new ways of being and relating, become fluid and wild in ways that are constrained on the surface."
Some larger caves turned into notorious party zones: a 7-meter-tall gallery below the Val-de-Grâce hospital is widely known as "Salle Z." Over the last few decades, various other locations in subterranean Paris have hosted jazz and rock concerts and rave parties — like no other city, Paris really has an "underground music scene."
Hokusai's Great Wave as the backdrop to the "beach" under Paris.Credit: Reddit
Cataphiles vs. cataphobes
With popularity came increased reports of nuisance and crime — the tunnels provided easy access to telephone cables, which were stolen for the resale value of their copper.
The general public's "discovery" of the underground network led the city of Paris to officially interdict all access by non-authorized persons. That decree dates back to 1955, but the "underground police" have an understanding with seasoned cataphiles. Their main targets are so-called tourists, who by their lack of knowledge expose themselves to risk of injuries or worse, and degrade their surroundings, often leaving loads of litter in their wake.
The understanding does not extend to the IGC. Unlike in the 19th century, when weak cavities were shored up by purpose-built pillars, the policy now is to inject concrete to fill up endangered spaces — thus progressively blocking off parts of the network. That procedure has also been used to separate the Catacombs to prevent "infiltration" of the site by cataphiles.
Many subterranean streets have their own names, signs and all. This is the Rue des Bourguignons (Street of the Burgundians) below the Champs des Capucins (Capuchin Field), neither of which exists on the surface.Credit: Jean-François Gornet via Wikimedia and licensed under
The cataphiles, however, are fighting back. In a game of cat and mouse with the authorities, they are reopening blocked passages and creating chatières ("cat flaps") through which they can squeeze into chambers no longer accessible via other underground corridors.
Catacomb climate control
Alone against the unstoppable tide of concrete, the amateurs of Underground Paris would be helpless. But the fight against climate change may turn the subterranean labyrinths from a liability into an asset — and the City of Paris into an ally.
The UN's 2015 Climate Plan — concluded in Paris, by the way — requires the world to reduce greenhouse gas emissions by 75 percent by 2050. And Paris itself wants to be Europe's greenest city by 2030. More sustainable climate control of our living spaces would be a great help toward both targets. A lot of energy is spent heating houses in winter and cooling them in summer.
This is where the constant temperature of the Parisian tunnels comes in. It's not just good for brewing beer; it's a source of geothermal energy, says Fieldwork, an architectural firm based in Paris. It can be used to temper temperatures, helping to cool houses in summer and warming them in winter.
One catch for the cataphiles: it also works when the underground cavities are filled up with concrete. So perhaps one day, Paris Underground, fully filled up with concrete, will completely fall off the map, reducing the city's formerly real doppelgänger into an air conditioning unit.
Cool in summer, warm in winter: Paris Underground could become Paris A/C.Credit: Fieldwork
Strange Maps #1083
Got a strange map? Let me know at strangemaps@gmail.com.
The prevalence of allergies arising in childhood has increased over the last 50 years, with 30 percent of the human population now having some kind of atopic disease such as eczema, food allergies, or asthma. The cause of this increase is still subject to debate, though it has been associated with a number of factors, including changes to the gut microbiomes of infants.
A new study by Canadian researchers published in Cell Reports Medicine may shed further light on how these allergies develop in children by examining the contents of their first diaper.
The things you do for science
The research team examined the first stool of 100 infants from the CHILD Cohort Study. The first stool of an infant is a thick, green, horrid-looking substance called meconium. It consists of various things that the infant ingests during the second half of gestation. Additionally, it provides not only a snapshot of what the infant was exposed to during that time, but it also reveals what the food sources will be for the initial gut bacteria that colonize the baby's digestive tract.
The content of the meconium was examined and found to contain such varied elements as amino acids, lipids, carbohydrates, and myriad other substances.
A graph of the comparative, summed abundance of different elements in a metabolic pathway after scaling to median abundance of each metabolite. The blue figures are those children without atopy, the yellow ones show the data for those with an atopic condition. Petersen et al.
The authors fed this information into an algorithm that used this data, along with the identities of the bacteria present as well as the baby's overall health, to predict which infants would go on to develop allergies within one year. The algorithm got it right 76 percent of the time.
A way to prevent childhood allergies?
Infants whose meconium had a less diverse metabolic niche the initial microbes to settle in the gut were at the highest risk of developing allergies a year later. Many of these elements were associated with the presence or absence of different bacterial groups in the digestive system of the child, which play an increasingly appreciated role in our overall health and development. The findings were summarized by senior co-author Dr. Brett Finlay:
"Our analysis revealed that newborns who developed allergic sensitization by one year of age had significantly less 'rich' meconium at birth, compared to those who didn't develop allergic sensitization."
The findings could be used to help understand how allergies form and even how to prevent them. Co-author Dr. Stuart Turvey commented on this possibility:
"We know that children with allergies are at the highest risk of also developing asthma. Now we have an opportunity to identify at-risk infants who could benefit from early interventions before they even begin to show signs and symptoms of allergies or asthma later in life."
A model for early childhood allergies
Petersen et al.
As shown above, the authors constructed a model of how they believe metabolites and bacterial diversity help prevent allergies. Increased diversity of metabolic products in the meconium encourage the development of "healthy" families of bacteria, like Peptostreptococcaceae, which in turn promote the development of a healthy and diverse gut microbiome. Ultimately, such diversity decreases the likelihood that a child will develop allergies.
