Sudbury Neutrino Observatory

The Sudbury Neutrino Observatory (SNO)

What is the SNO?

The Sudbury Neutrino Observatory is an underground laboratory that began operating in 1999 to study and detect solar neutrinos which are particles that do not have an electric charge and nearly no mass. These invisible particles are produced in the suns core as byproduct of nuclear fusion and pass through the earth nearly at the speed of light. Due to the lack of mass and electric charge, they are extremely difficult to study which is why the Sudbury Neutrino Observatory was built for. The purpose of the SNO is to help scientists and astronomers understand the processes that take place in the sun.  It is operated by around 130 Canadian, American and British scientists.

 Development began in 1990 and was completed in 1998. It cost a total of $73,000,000 and was supported and funded by the Natural Sciences and Engineering Research Council of Canada, the Northern Ontario Heritage Foundation, United States Department of Energy, Ontario Power Generation and several more.

In the image above, you can see what the detector looks like along with the 9000 light sensors. Below is a diagram that displays the structures design and depth

Construction:

The Sudbury Netrino Observatory was built 2km underneath a mine in Sudbury called Creighton Nickel Mine. The detector is made up of a large acrylic ball that spans 12 m in diameter. The sphere hangs with the support of 10 ropes made of synthetic fiber. There are over 9000 photo multiplier tubes (or light sensors) right along the outside of the sphere that faces towards it. To detect the presence of neutrinos, these sensors observe how the neutrinos react with the water. When neutrinos interact with heavy water, it creates Cherenkov radiation, in other words, flashes of light emitted from the tank due to the interaction between neutrino and heavy water.

 There were many precautions taken in order to prevent unwanted signals from other sources and elements. The main one is the depth of the detector. SNO was built deep underground to shield the detector from noise of cosmic rays. Another is that the lab is kept extremely clean to prevent signals from the dust of the mine from interfering with the sensors.

This image shows just how deep the SNO is built.

Contribution:

The SNO has accomplished a lot in the field of neutrinos and has made important discoveries about their production along with information about the core of the sun. According to Astro-Canada, in the early 80s, “it was realized that the number of solar neutrinos detected by various laboratories were less than predicted by theoretical calculations”. This caused a debate about the suns production of neutrinos. Scientists could not confirm whether we simply did not understand our sun properly or if these neutrinos were changing form as they reached earth causing the amount to lower. The SNO discovered that neutrinos have some mass and can change form when they pass through the earth.

Although its primary goal has already been met, scientists continue using its data in order to learn as much about neutrinos as possible.

 Today, the Sudbury Neutrino Observatory has been expanded and is being operated under a new name, SNOLAB. The new observatory perform the same experiments and studies as SNO, however the laboratory has been expanded. A Queens University press release states that the lab will be “expanded by nearly 150% “,

http://astro-canada.ca/_en/a2115.php

http://physics.carleton.ca/sno/about-sno-project/sno-neutrino-detector

http://www.sno.phy.queensu.ca/sno/press_release/SNOBackgrounderNov15f.pdf

Earthquake Engineering

Earthquake Engineering

There are many regions around the globe that are at constantly at high risk of being affected by seismic waves, otherwise known as earthquakes. The reason that earthquakes tend to happen in the same areas is due to the movement and position of tectonic plates that consist of the crust and the upper mantle. In total, there are about 7 major plates and many smaller ones. Areas that get shaken by high magnitude earthquakes often are the places that are aligned between 2 different plates that rub against each other which cause the rumbling. One example of such place is the great state of California, with beautiful and diverse landscapes, nice beaches, great weather…and the occasional violent earthquake. California lies on two tectonic plates called the Pacific Plate which moves upwards and the North American Plate which travels downwards (shown in the picture below). When these two plates come in contact and rub against one another, it causes very intense vibrations which are the cause of the shaking. 

         

The first image shows the hazard of earthquakes (red is high risk). The second picture shows the direction of the North American Plate relative to the Pacific Plate along the west coast. You can see that areas that are on top of the edge of a plate have a higher risk of earthquakes.

Unfortunately, preventing an earthquake from occurring isn’t exactly possible since superman doesn't exist however, cities in high risk areas can take measures to minimize the damage as much as they can. One of the main consequences of earthquakes is the damage done to buildings. In some cases, if the structure isn't strong enough, it can collapse completely. In order to prevent this, engineers need to design and build structures in a certain way to make them earthquake resistant. This is known as earthquake engineering. There are also methods of strengthening existing structures known as seismic retrofitting, however I’ll be talking about the former.

The process of building an earthquake resistant building starts way before the construction and even the design. Before planning anything out, engineers have to determine the seismic activity in the area which they are building. One of the things they must consider is the probability of a major earthquake occurring for the next couple of decades. They also look at previous earthquakes to determine the risk of another one. Once the first step is complete, they can move on to designing the building. When creating a building in an area with high seismic activity, engineers tend to avoid structures with unique shapes such as “t” shaped or hourglass buildings since they would not be able to withstand the force of an earthquake although they are visually appealing. One way of making a building earthquake resistant is to make it triangular. This is not the primary choice since today we have better technology and new methods, but since the shape causes the center of gravity to be rather low and the majority of the weight of the structure lies in the bottom portion, it can be a reliable way to reduce the shaking of the building.

The main method that is used today is a base isolation system. Its function is to physically separate the base of the building from the floor using a mechanism.

There are different types of base isolations. One of them is the spherical sliding bearing system which supports the building with rounded and low friction bearing pad. The rounded bearing pad allows the building to be less affected by the shock of the earthquake by allowing it to slide horizontally smoothly.

This video explains and shows how the effects of an earthquake can be minimized in this base isolated building in LA

The second method is the lead-rubber bearing system which is commonly used for earthquake resistant buildings. They are made by many alternating layers of rubber and steel plates that are firmly compressed against each other. The job of this block of rubber/steel is to move left and right very flexibly along with the movement of the earthquake to allow the building to feel less of the shaking. In other words, while a structure that has a fixed base (not resistant to earthquakes) is susceptible to shaking violently due to the earthquake, an isolated base structure remains less affected due to the mechanism that takes the shock in between the ground and the structure.

Here we can see the function of the base isolation. The fixed-base building is clearly having a bad time compared to the isolated building...

Its a great thing that humans have discovered ways to prevent earthquakes and other natural disasters from causing too much damage to urban areas with large skyscrapers and structures. I guess our next goal is to find a solution for the possibility of an alien invasion...

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The International Space Station

Up to this point, the International Space Station may be one of humanities greatest accomplishments. The estimated 100 billion dollar machine which is constantly being “renovated” and improved has helped us find many new scientific discoveries which would have been nearly impossible without its existence.  It also gives us the opportunity to test out experiments which can only be done in space.

What is it?

The International Space Station (ISS) is a space station that orbits the earth from space. Since it is so large and orbits so low, it is actually possible to view the station with the naked eye at night time, however it travels at an incredible average speed of 27,000 km/h. The first module was launched on November 20^th 1988 from  with the intention of being used as a laboratory, an observatory and factory for conducting research that could not be done on earth for astronauts from all over the world rather than one nation (hence the name “International Space Station” . It is also used to provide a home for people in space who are studied by scientists during their stay in order to learn the effects of living in space. 

How it was built:

Since the International Space Station is so large and heavy (approximately 450,000 kg which is quite a bit), it would be out of the question to build it as one piece on earth and launch it into space. Instead, with the agreement and collaboration of 15 different countries (although most belong to the European Space Agency), they sent different flights to supply the ISS with new parts and supply for habitation from all the partnering countries in an organized manner.  Since the ISS has been adding and replacing different sections since its launch, it has been created in a very flexible way to allow the addition of new pieces to be as simple and efficient as possible.