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The neutrino project is once again in the news. A delegation led by Lok Sabha MP TR Balu met Union Minister for Commerce and Industry Piyush Goyal ahead of PRAGATI meeting chaired by the Prime Minister and conveyed the state government’s opposition to the project. Chief Minister MK Stalin had already written to the centre that the project will not be allowed at the proposed site.

 There are several myths and rumours surrounding this project. In this two-part series, we will bring out the facts.

 Here are some fears voiced by the concerned:

That the drilling and explosions at the site during the construction of the project will put in danger Mullaiperiyar dam some 30 km away and other sites;

That the project is only an adjunct to America-based Fermi Lab’s neutrino project. At the Theni site, neutrino rays produced at the ‘neutrino factory’ from Fermi Lab will be researched. This is why the site is exactly 180 degrees from the lab’s location in Illinois, USA. The lab is part of a secret bomb project in which the US and India are collaborating.

Above are some pseudo scientific “facts” being spread. But they are Hollywood movie-type conspiracy theories. The truth is something else.

Neutrinos are all around us. The particles are second only to photons in abundance in the universe – light is composed of photons. So they are as ubiquitous as light. Neutrinos are constantly produced due to the cosmic activity of galaxies, the sun and interaction of cosmic rays on Earth’s atmosphere. They are everywhere, all around us. In fact, every instant, about 400 crore of neutrinos pass thorough an area equal to finger nail. While so abundant we know very little about the nature of this elusive particles. Scientists are probing the nature and properties of neutrinos by setting up labs all over the world.

 Some young Indian scientists, seeing an opportunity to do world class science, proposed a  observatory to study neutrinos, especially the atmospheric neutrinos, in 2000s. After they successfully answered a series of questions posed by the government, with regard to the viability of the study and its importance, funds were allocated in 2015.The project was supposed to have been constructed in five years, the observatory must have been up and running. 

The siting of the observatories are important. For instance, telescopes are not located on the surface in towns and cities. The powerful lights in these urban areas will obscure the dim light coming from galaxies. Therefore, such telescopes are installed on top of mountains so the meagre photons coming from distant galaxies could be captured by the instrument.

Neutrinos are weekly interacting particles, they can just enter from one side of the Earth and come out unblemished at the other end; that is why scientists call the ethereal neutrinos elusive. Detecting the neutrinos are not simple. Atmospheric neutrinos, the main interest of Indian scientists, are mixed with cosmic rays. Hence, if neutrino observatories are kept on the ground, then all the other cosmic rays will also fall on the observation equipment, not just neutrinos. The noise that all the cosmic rays generate will obscure the elusive neutrinos; and the observation will not yield result. Scientists bore through mountains, create a tunnel and place the detector there. The reason is that all the other cosmic rays will get absorbed by the solid rock and other material in the mountains by the time the rays reach the observatory down below. 

Typically, some 1.5km high mountains with dense rock are bored to filter out the cosmic rays. Inside the mountains, tunnels are dug and the observatory placed there. Since they are atmospheric neutrinos, the site has to be located near the equator.  

Further, from environmental and social viewpoint, scientists wanted to ensure that no agricultural land was taken over and forests  destroyed for construction of the observatory. And they search for a suitable location to ensure this. With the help of geologists, they located Pottipuram, near Theni and felt it was most appropriate. 

The observatory is passive kind; the detector identify and count the atmospheric neutrinos falling on it. It is not an active instrument, producing or emitting. Lie a rain-gauge, it would just measure the amount, strength and the direction of the neutrinos falling on it.  Evaluating how many neutrinos are falling from which direction can help scientists understand many of the neutrino’s properties. 

Early on in the project, certain people raised a pseudo-scientific objection; they falsely claimed that the  the big magnets will pull in neutrinos traveling in all directions. If there is a power cut,  the neutrino is attracted by the magnet would bounce back, radiate for 100 kilometers and go on to contaminate groundwater . Moreover,they averred digging the tunnel will lead to vibrations that will affect Mullaperiyar dam. 

But the truth is that this safe, benign basic science project that will not harm the environment is being portrayed as a big, dangerous project by scaremongers. No wonder the people living in and around Pottipuram are troubled and confused about the observatory. 

The rumours being spread about the project are not very different from pseudo scientific beliefs such as “Ganesha drank milk,” “Pushpaka Vimanam was there 6,000 years ago,” and “Cows breathe in oxygen and breathe out oxygen.” 

The idea that the chargeless neutrinos are attracted by magnets or that 5kg to 10kg explosives will set off vibrations several kilometers away is similar to saying, “Planting 16 basil plants will purify the atmosphere and help avert climate change,” and “Smoke given out during yagnas will purify the air around.”The cavern proposed is just like the Punalur railway project, contracted few years back in the same region; in no way the construction would affect the dams situated 30 kilometres away.  

We have seen how government structures respond when common people are affected by pollution such as in the Bhopal gas tragedy. When rich-poor divide widens and economic growth reaches only a few people, it is natural that people living in the area ask if it is necessary to do dangerous research in their neighbourhood. 

Whether we like it or not, crores and crores of neutrinos are passing around, in us and outside us. They penetrate mountains and the earth and fall on the ground all the time. Even those who know high school physics will understand that electrically neutral particles such as neutrinos are unaffected by magnets. Scaremongers’ pseudo science is exposed by this. 

Any vibration attenuates and weakens over distance. Any engineer can calculate how far the vibrations set off by the explosions required during construction of the project will travel. When rote learning passes off as scientific education, it is difficult for common people to expose false rumours. Instead of educating people on science, fiction is being spread by bogus activists. Such things will only spread irrationality. 

Below are my answers to questions swirling in social and news media regarding the project. 

Q) Isn’t there any other site for the project other than Theni? If there is no danger, why not go to Gujarat? Or go to Ponmudi in Kerala where the mountains are even older.

A) Every research project has some requirements regarding location. They cannot be sited anywhere. For instance, telescopes are typically installed on top of mountains. Similarly, some geological requirements are there for the neutrino project. 

It is not only necessary that old mountains are required, other factors need to be considered, too. The site should be such that the mountain can be bored through from the base of the mountain like in a railway tunnel and the detector should installed on the surface right below the apex of the mountain. Requirements on age of the mountain relate to hard rock formation in older mountains. Such rocks are sturdy and strong enough to withstand tunnels being dug.

Neutrino Observatory site at Pottipuram

The site of the proposed Indian Neutrino Observatory at Pottipuram, Theni. A tunnel will be bored inside the mountain on the surface and the observatory will be located right below the apex of the mountain

Pottipuram site is located at a low seismic activity zone (Zone II). Drilling a cave is easier here. 

Himalayas are tall but not sturdy. They are mostly composed of sediment rock. They are an agglomeration of small rocks and, for that reason, Himalayan rock formations are not as strong. Rock formations in other states are also not appropriate. 

The West Bodi hills in Theni are made of charnockite. Mountains are typically single-rock formations unlike in the Himalayas. In addition, this particular hillock does not have dense forests, nor are their agricultural lands. If the project site required that agricultural land needed to be appropriated or trees in forests had to be felled, then that site would not be desirable. 

The site in Pottipuram was selected after a thorough search taking into account all factors. No forests need to be felled here, no lands to be appropriated. The rock formations are strong, too.

If atmospheric neutrinos are being researched, then it is better to site the place as close as possible to the equator. Old rocks will help to filter out other cosmic rays and allow only the tiny neutrinos to pass through deep down. 

From where the observatory is installed, there should be rocks one kilometer all around. Therefore, a 1 or 1.5 km tall mountain is required. But if the mountains are taller, then the pressure on the cave will be more and there is a danger of the tunnel getting destroyed. Such nuances are required to be evaluated, too.

Q) When lakhs of tonnes of explosives are being set off and rocks of lakhs of tons weight are being split, it is natural that the environment will be impacted severely. Won’t groundwater get affected while boring through the mountain?

No mountain will be destroyed. No rocks will be destroyed like in stone quarries. Mountains will not be dug top-down like in a well, so no groundwater will be affected. 

Like how during the laying of the Metro rail in Chennai or when rail lines are laid through mountains, a tunnel will be dug into the mountain through which two trucks can pass through. The height will be 7 meters. The cave will be all along the surface only. When the cave reaches right below the apex of the mountain, drilling will be stopped. This means the cave will not be through-and-through.

At the end of the cave, the observatory will be located which will detect atmospheric neutrinos. 

Only some 450 tons of explosives will be used spread over five years. Since explosives will be used only to lay the way in, they will be set off twice or three times a day. They will ensure no cracks develop in the mountain. In two months, they would have reached 300 meters inside. After that, the construction activity will not be felt outside. 

Today, subways are being dug to lay Metro rails. In Kolkata, for instance, the tunnel goes below a river. This technology is not new for us. The neutrino project in Pottipuram is similar to the Punalur railway tunnel nearby. 

Further, the impact of explosions can be clearly assessed. Any vibration will diminish in strength over a distance. If Wt is the amount of explosive that will be used, “Dist” is the distance where the vibration needs to be calculated then the below formula will tell us how much will be the vibration at that distance.

PPV = H x (Dist / Wt0.5)-1.6

In this, H is a constant that depends on the material and shows how much the vibration will be allowed to travel in the material. For instance, in solid ground, the vibration will travel longer while in sand, vibrations will dissipate over shorter distance.

The impact of the explosions here will not be felt even beyond 500 m. In the rock formation at the site, the vibrations will travel at less than 1 mm/second 500 m away. Vaigai and Mullaiperiyar dams are located 30 km away whereas these vibrations will not be felt even in villages nearby.

TV Venkateswaran is a scientist at Vigyan Prasar, Department of Science and Technology, New Delhi

This is the second part of the neutrino article.


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