March 21, 2019(updated March 21, 2019) Published by Sai Teja
In quantum physics, there has always been suspense that how some particles travel from one place to another, passing impenetrable barriers, without having enough energy to do so. This question has puzzled the scientists for decades that how a particle can ‘tunnel‘ without energy.
In order to understand this process, scientists have been carrying out various experiments. In one such experiment using hydrogen atoms, it was seen that this ‘tunneling‘ process happens instantaneously. This instant tunneling has been investigated before as well, but now scientists have finally observed this process with the help of an instrument called the attoclock.
The attoclock sets up 1,000 ultra-short pulses of light per second to interact with the hydrogen atom, pulses totaling 30 gigawatts of instantaneous power. This created a condition in which the single electron of the atom could be pushed through a barrier.
Sang said, “There’s a well-defined point where we can start that interaction, and there’s a point where we know where that electron should come out if it’s instantaneous. So anything that varies from that time we know that it’s taken that long to go through the barrier. That’s how we can measure how long it takes. It came out to agree with the theory within experimental uncertainty being consistent with instantaneous tunneling.”
It was one of the most mysterious studies of quantum mechanics that the scientists now have a better handle on. The new knowledge that the attoclock provides could be useful anywhere where quantum tunneling is involved including electron microscope and the transistor in our computers.
Quantum tunneling has also been suggested as a way of harvesting energy from excess radiation and waste heat, so more we understand the process of how it actually works, the better. The new researches can be carried out in order to understand how other kinds of atoms tunnel through the barriers and at what speed.
“Now that we have learned this process, we can use this process for other atoms possibly to learn about new physics”, says one of the researchers, Igor Litvinyuk from Griffith University.
March 19, 2019(updated March 19, 2019) Published by Sai Teja
Nowadays the whole world has become digitalized and for each and everything we have an electronic device. We have a television to entertain ourselves, an iPad to watch movies and work on the go, a mobile to receive calls when we are away from home. These electronic devices have something called as the semiconductor.
A semiconductor is a substance whose electrical conductance falls between metal and insulator. However, the conducting property can be altered by adding impurities into the crystal. Some commonly known semiconductors are silicon, germanium, and arsenide. Since it becomes very difficult to produce, semiconductor becomes very expensive.
Quantum dot is the solution and can be used in place of a semiconductor. Quantum dots are basically very small semiconductors which lie in the nanometre scale. Quantum dots change its properties even with a very small change in shape or size. The quantum dots have been used in electronic instruments like solar panels, camera sensors and medical imaging tools by researchers.
David Hanifi co-author of research on quantum dots said, “These quantum dots can be made in large number in labs in a more simple way as compared to semiconductor”.
When the research started in order to understand whether they could compete with semiconductors, the researchers focused on how efficiently the quantum dots could remit the light that they absorb, and the experiments showed that the performance of quantum dots was better as compared to a semiconductor.
This research work is the result of a collaboration between the labs of Alberto Salleo, professor of materials science and engineering at Stanford, and Paul Alivisatos, the Samsung Distinguished Professor of Nanoscience and Nanotechnology at the University of California, Berkeley, who is a pioneer in quantum dot research and senior author of the paper. However, this research is a part of the collection of projects of the Department of Energy at the Frontier Research Centre.
There are various benefits that quantum dots have. Being highly customizable, one of the biggest benefits of quantum dots is that it changes its shape due to which it can change the wavelength of light that they emit which is one of the biggest advantages in colour based applications like television.
Thus, quantum dots have hit the consumer market in the form of quantum dot TV or the QLED(where Q stands for quantum dots).
Samsung QLED TV 8K – 75 inches. Credit: Bretwa/ wikimedia
As we all know that everything in this universe comes with its own disadvantages, the disadvantage that the quantum dot has is that because of its smaller size – it takes many particles to come together in order to perform a particular task. In order to form so many quantum dots, the chances of something going wrong becomes highly possible, which indirectly means that the chances of some program to go wrong also becomes possible due to which there are chances of performance getting hampered.
The researchers are finding out measurement techniques in order to evaluate these particles.
The next step in the ongoing research involves even more precise measurements and if the researchers can determine that, these quantum dots could reach an efficiency of 99.9 percent or above.
With the increase in efficiency, we can have wonderful applications like:
New glowing dyes to enhance our ability to look at biology at the atomic scale.
Luminescent cooling and luminescent solar concentrators, which allow a relatively small set of solar cells to take in energy from a large area of solar radiation and many more things.
“People working on these quantum dot materials have thought for more than a decade that dots could be as efficient as single crystal materials,” said Hanifi.
So, Let us hope for this research to go forward and get us many other efficient applications.
March 18, 2019(updated March 18, 2019) Published by Kshitij Kumar
Have you ever imagined the infused tea flowing back into the tea bag or a volcano from “erupting” in reverse? We cannot imagine about these things because we have learned about the second law of thermodynamics which states that the total entropy of an isolated system can never decrease over time. A group of researcher scientist from Russia teamed up with the scientist from the U.S. and Switzerland in order to challenge this fundamental law of energy.
The study’s lead author Gordey Lesovik who heads the Laboratory of the Physics of Quantum Information Technology at MIPT states that “This research is one of the series which adds up to violating the second law of thermodynamics which is closely associated with the notion of arrow of time that puts in position the one way direction of time from past to future.”
The physicists tried to understand if time could reverse itself for a tiny fraction of a second for a particle. They tried to do this by two methods – first by experimenting the electron in empty interstellar space.
Andrey Lebedev co-author from MIPT and ETH Zurich stated that “If we consider an electron in space and we begin to observe it, we can come to know the position of it. If not the position but at least the area can be decided since the laws of quantum mechanics don’t allow us to understand the exact position of the electron.”
The physicist then adds “The evolution of electron can be explained by Schrödinger’s equation. However, it makes no distinction between the past and the future, the region of space containing the electron will spread out very quickly. The uncertainty of the electron’s position is growing.”
Valerii Vinokur, a co-author of the paper, from the Argonne National Laboratory, U.S. adds to the discussion that “Mathematically, it means that under a certain condition of transformation called complex conjugation, the equation will describe a smeared electron localizing back into a small region of space over the same time period. However, this is only possible theoretically and not practically.”
The second method of experimentation was done with the help of quantum computing instead of electrons, made out of two or three basic elements called superconducting qubits. They have four stages of the experiment.
The four stages are as follows:
Stage 1: Order In the first stage, like the electron was imagined to be localized in space, here, the qubit is initialized in a stage called the zero stage.
Stage 2: Degradation Similar to the electron being smeared out over an increasingly large region of space, the qubits leave the zero stage and become a complex pattern of zeros and ones.
Stage 3: Time Reversal In this stage similar to the electron being induced to fluctuation by microwave, here, a special program modifies the state of the quantum computer in such a way that it would then evolve “backward”, from chaos toward order.
Stage 4: Regeneration Again the evolution program starts from stage 2. Provided that the “kick “ has been launched successfully. The program reverses the state of qubits back into the past. It was observed that where two qubits were involved, the success rate was around 85 percent, but where 3 qubits or more than 3 qubits were involved more errors happened and it resulted in only 50 percent of the success rate.
March 11, 2019(updated March 11, 2019) Published by Kshitij Kumar
For the first time ever in history, NASA captured air to air images of the interaction of shockwaves from two supersonic aircraft merging in the air. This was done to create a Jet that flies faster than the speed of sound without producing irritating ‘Sonic booms‘.
The greatest challenge in capturing the image was timing. NASA flew a B-200 equipped with imaging system, that took 10 years to develop, reached around 30,000 feet to acquire the spellbinding image and collected 1,400 frames per second.
The image depicts two T-38 supersonic Jets from the US Air Force, during a test flight from the research center at Air Force Base, California.
The pair of T-38s were required to not only remain in proper formation but to fly within the camera’s frame at supersonic speeds, as they passed 2,000 feet beneath the B-200. As a result, the three aircrafts were at the right place and at the right time.
“I am ecstatic about how these images turned out. We never dreamt that it would be this clear, this beautiful. With this upgraded system, we have, by an order of magnitude, improved both the speed and quality of our imagery from previous research.” J.T. Heineck, a scientist at NASA’s Ames Research Center, said in a statement.
The system will be used to capture data confirming the design of the agency’s X-59 to quiet supersonic Technology X-Plane. The X-59 flying supersonic will produce shockwaves in such a way that instead of sonic boom only a quiet rumble may be heard.
Nasa Quiet Supersonic Technology Low-Boom Flight Demonstrator (Source: NASA)
When an aircraft crosses around 1,225 km per hour at sea level, it produces waves from the pressure it puts around, producing the irritating thunderous sound called ‘Sonic booms’.
Sonic booms can be Deafening to people on the ground, responsible for shattering of window panes. Few countries like United State and cities have banned the Franco-British airliner from their airspace because of its sonic booms.
“What’s interesting is, if you look at the rear T-38, you see these shocks kind of interact in a curve. This is because the trailing T-38 is flying in the wake of the leading aircraft, so the shocks are going to be shaped differently. This data is really going to help us advance our understanding of how these shocks interact.” said Neal Smith, a research engineer at NASA.
These images will be helpful for research into planes that can fly faster than sound without causing irritating sonic booms, lifting current restrictions on supersonic flight over land.
March 10, 2019(updated March 10, 2019) Published by Kshitij Kumar
A paper released in Physical Review B by Boston University researchers, Xin Zhang, a professor at the College of Engineering, and Reza Ghaffarivardavagh, a Ph. D. student in the Department of Mechanical Engineering demonstrates that it is possible to silence noise using an open, ring-like structure, created to mathematically perfect specifications, for cutting out sounds while maintaining airflow.
“Today’s sound barriers are literally thick heavy walls,” says Ghaffarivardavagh. Although noise-mitigating barricades, called sound baffles, can help drown out the whoosh of rush hour traffic or contain the symphony of music within concert hall walls, they are a clunky approach not well suited to situations where airflow is also critical.
Imagine barricading a jet engine’s exhaust vent—the plane would never leave the ground. Instead, workers on the tarmac wear earplugs to protect their hearing from the deafening roar.
A shared passion of Ghaffarivardavagh and Zhang in mathematics has buoyed both of their engineering careers, made them well-suited research partners and has guided them toward a workable design for what the acoustic metamaterial would look like.
Boston University mechanical engineers have created synthetic, sound-silencing structures—acoustic metamaterials—that can block 94% of sounds. Reza Ghaffarivardavagh (ENG) (front center) holds two of the open, ringlike structures over his ears while Stephan Anderson (MED) (left), Xin Zhang (ENG) (rear center), and Jacob Nikolajczyk (ENG) (right) make a racket. Photo by Cydney Scott
A calculation was done by them on the dimensions and specifications that the metamaterial would need to have in order to interfere with the transmitted sound waves, preventing sound—but not air—from being radiated through the open structure. On this, they said that the basic premise is that the metamaterial needs to be shaped in such a way that it sends incoming sounds back to where they came from.
First, as a test case, a structure was created by them that could silence sound from a loudspeaker and based on their calculations, they modeled the physical dimensions that would most effectively silence noises.
Bringing each of the tested models to life, they used 3-D printing to materialize an open, noise-canceling structure made of plastic. While trying out in the lab, the researchers sealed one end of the loudspeaker with a PVC pipe. On the other end, the tailor-made acoustic metamaterial was fastened into the opening. With the hit of the play button, the experimental loudspeaker set-up came oh-so-quietly to life in the lab.
Standing in the room, one would never know if a loudspeaker is turned on with blasting an irritatingly high-pitched sound, based on the sense of hearing alone. But the thrumming of the loudspeaker’s subwoofers can be seen clearly if peered into the PVC pipe.
While testing the metamaterial in the lab, the metamaterial worked like a mute button incarnate ringing around the internal perimeter of the pipe’s mouth until Ghaffarivardavagh pulled it free. The next moment, the lab was filled with the screeching of the loudspeaker’s tune.
“The moment we first placed and removed the silencer…was literally night and day,” says Jacob Nikolajczyk, who in addition to being a study co-author and former undergraduate researcher in Zhang’s lab is a passionate vocal performer.
“We had been seeing these sorts of results in our computer modeling for months—but it is one thing to see modeled sound pressure levels on a computer, and another to hear its impact yourself.”
It was found by comparing sound levels with and without the metamaterial fastened in place that an exact of 94% of the noise could be silenced, making the sounds emanating from the loudspeaker imperceptible to the human ear.
With the prototype being successfully proven to be effective, the researchers have some big ideas about how their acoustic-silencing metamaterial could go to work making the real-world quieter.
“Drones are a very hot topic,” Zhang says. Companies like Amazon are interested in using drones to deliver goods, she says, and “people are complaining about the potential noise.” “The culprit is the upward-moving fan motion,” Ghaffarivardavagh says. “If we can put sound-silencing open structures beneath the drone fans, we can cancel out the sound radiating toward the ground.”
The acoustic metamaterials can be of great help to fans and HVAC systems that are closer to home or the office that render them silent yet still enable hot or cold air to be circulated unencumbered throughout a building.
Ghaffarivardavagh and Zhang also point to the unsightliness of the sound barriers used today to reduce noise pollution from traffic and see room for an aesthetic upgrade. “Our structure is super lightweight, open, and beautiful. Each piece could be used as a tile or brick to scale up and build a sound-canceling, permeable wall,” they say.
According to Ghaffarivardavagh, The shape of acoustic-silencing metamaterials, based on their method, is also completely customizable. “We can design the outer shape as a cube or hexagon, anything really,” he says. “When we want to create a wall, we will go to a hexagonal shape” that can fit together like an open-air honeycomb structure. Such walls could help contain many types of noises. Even those from the intense vibrations of an MRI machine, Zhang says.
According to Stephan Anderson, a professor of radiology at BU School of Medicine and a co-author of the study, the acoustic metamaterial could potentially be scaled “to fit inside the central bore of an MRI machine,” shielding patients from the sound during the imaging process.
Zhang says the possibilities are endless since the noise mitigation method can be customized to suit nearly any environment: “The idea is that we can now mathematically design an object that can block the sounds of anything,” she says.
The most powerful and largest particle accelerator host CERN is up to experiments to look for particles that are associated with the mysterious dark matter. The dark matter is believed to make up about 27% of the universe according to the European physics lab.
The dark matter is a mysterious substance which is perceived through its gravitational pull on other objects. According to the scientists associated to the study of space science, the so-called ordinary matter – which includes stars, gases, dust, planets and everything on them – accounts for only five percent of the universe. “Some of these sought-after particles are associated with dark matter,” a statement from CERN said.
Using observations from NASA’s Hubble Space Telescope and Chandra X-ray Observatory, astronomers have found that dark matter does not slow down when colliding with itself, meaning it interacts with itself less than previously thought. Researchers say this finding narrows down the options for what this mysterious substance might be. Dark matter is an invisible matter that makes up most of the mass of the universe. Because dark matter does not reflect, absorb or emit light, it can only be traced indirectly by, such as by measuring how it warps space through gravitational lensing, during which the light from a distant source is magnified and distorted by the gravity of dark matter. (Credit: NASA Goddard)
On Tuesday, the European Organization for Nuclear Research (CERN) announced that it has approved the experiment designed to look for light and weakly interacting particles at the Large Hadron Collider (LHC) — a giant lab in a 27-kilometer tunnel straddling the French-Swiss border.
The Lab has also given a statement about the Forward Search Experiment (FASER) that it will complement CERN’s ongoing physics programme, extending its potential to several new particles. Some of these sought-after particles are associated with dark matter, which is a hypothesized kind of matter that does not interact with the electromagnetic force and consequently cannot be directly detected using emitted light. FASER will search for a suite of hypothesized particles including so-called “dark photons“, particles which are associated with dark matter, neutralinos and others.
“It is very exciting to have FASER approved for installation at CERN. It is amazing how the collaboration has come together so quickly and we are looking forward to recording our first data when the LHC starts up again in 2021,” said Jamie Boyd, co-spokesperson of the FASER experiment.
“This novel experiment helps diversify the physics programme of colliders such as the LHC, and allows us to address unanswered questions in particle physics from a different perspective,” Mike Lamont, co-coordinator of the PBC study group, said in a statement. “The four main LHC detectors are not suited for detecting the light and weakly interacting particles that might be produced parallel to the beam line”, he added.
They may travel hundreds of meters without interacting with any material before transforming into known and detectable particles, such as electrons and positrons. The exotic particles would escape the existing detectors along the current beam lines and remain undetected.
The detector’s total length is under five meters and its core cylindrical structure has a radius of 10 centimeters. It will be installed in a side tunnel along an unused transfer line which links the LHC to its injector, the Super Proton Synchrotron.
A collaboration of 16 institutes is building the detector and will carry out the experiments which will start taking data from LHC’s Run 3 between 2021 and 2023.
The LHC was used in 2012 to prove the existence of the Higgs Boson – dubbed the God particle – which allowed scientists to make great progress in understanding how particles acquire mass.
What is dark matter?
Dark matter is a hypothetical form of matter that accounts approximately 85% of the matter in the universe, and about a quarter of its total energy density. dark matter does not interact with the electromagnetic force. This means it does not absorb, reflect or emit light, thus making it extremely hard to spot. Dark matter seems to outweigh visible matter roughly six to one, making up about 27% of the universe.
February 22, 2019(updated June 5, 2019) Published by Kshitij Kumar
The Higgs Boson God particle has been widely talked about in the recent past. You might have heard people talking about how its discovery has simplified explanations for why electrons have mass. You might have even heard about how it has aided in proving that the Standard Model is not incorrect. The discovery of the particle received tremendous attention from the press, and, was celebrated quite remarkably. So, what is all the fuss about? What really is the Higgs Boson? How does it help explain certain phenomena? Why is it called God particle? If you are looking for answers to any of these questions, or, are simply intrigued and want to know more about the Higgs Boson, then, look no further, you’re at the right place.
The Higgs boson is considered to be the particle excitation of the Higgs field and is named after the physicist, Peter Higgs. Peter Higgs and five other scientists are credited with coming up with the mechanism that provided evidence to the existence of such a particle.
What is all the fuss about then?
The reason there has been so much buzz surrounding the Higgs boson till recently was because its existence was only experimentally proven as recently as 2012. The reason it took so long for scientists to confirm its existence is the fact that the technology needed for confirming the existence of the Higgs boson, had not existed for a very long time. This discovery was a physics version of the discovery of DNA.
The discovery of this particle was made possible by the Large Hadron Collider (LHC). The Large Hadron Collider is a particle collider and is gigantic in nature. It is the largest machine in the world. It is present in a humongous tunnel near Geneva in Switzerland. Without the LHC, it would have been an extremely daunting, and some can even say, an improbable task to prove the existence of the Higgs boson.
You can read everything about search and discovery of Higgs boson here ->The Higgs Boson discovery pdf by CERN
Particle accelerators and the Large Hadron Collider
The Large Hadron Collider is a particle accelerator that is used to accelerate charged atomic and subatomic particles to large enough speeds to observe their behaviour. The Large Hadron Collider is currently the largest among such colliders. The tunnel in which it lies is massive and is 27km in circumference. It was built by the European Organization for Nuclear Research (CERN) and is used for studying the observations made by the collision of particle beams, generally, proton beams.
CERN LHC Particle Collider (Source: CERN)
Particle accelerators such as the LHC are considered to be fundamental in answering some of the questions that remain in the field of particle physics. These accelerators generally use an electromagnetic field to carry out the acceleration. You may ask, why is there a need for an electromagnetic field? To understand this, you will need to know how particle accelerators work. Particle accelerators need to have a source. A source is what generates particles such as protons and electrons. The electric fields are used in the process of accelerating these particles while the magnetic fields are responsible for controlling the paths of these particles.
To generate electrons for these particle accelerators, ‘electron guns’ are generally used. The electron gun consists of a cathode, which, is heated to high temperatures causing electrons to be produced from its surface. The electron gun consists of electrical and magnetic deflectors and the electron beam is obtained from a narrow hole at the end of the gun. This electron gun can also be viewed as an accelerator since it also consists of an electric field that accelerates the electrons, and magnetic deflectors that help in controlling the path. These electrons move towards the anode present in the gun and while passing through the electric field pick up speed and come out of the gun as a narrow beam.
To generate protons for the accelerators, hydrogen gas is used since only the nuclei of hydrogen atoms consist of single protons. The gas is ionized, and the protons and electrons are separated through electric fields and the beam of protons is obtained through a hole.
The beams produced are then collided and the particles that result from the collision are observed by detecting electrical signals. The detectors used in particle accelerators are built so that the electrical signals can be converted to digital data and analyzed. Higgs boson was detected in 2012 during such collisions.
Now that we know how Higgs boson was detected, let’s delve into what it really is.
The Higgs boson is a particle that is generated by the quantum excitation of the Higgs field. You may ask, what is the Higgs field? Well, the Higgs field is a field that exists evenly distributed throughout the universe. Some particles are said to interact with this field and obtain mass while some particles are said to not interact with it. The Higgs field is quite dissimilar to other fields, since, it is scalar. A scalar field is one where every point in the field can be associated with a scalar value.
So, what does that mean? It means that the Higgs field is directionless, it has a spin value of 0. Unlike other fields such as electromagnetic fields, the Higgs field has no preferred direction.
The particles carrying the strong force are the:
The strong interaction is observable at two ranges: on a larger scale (about 1 to 3 fm), it is the force that binds protons and neutrons (nucleons) together to form the nucleus of an atom. On the smaller scale (less than about 0.8 fm, the radius of a nucleon), it is the force (carried by gluons) that holds quarks together to form protons, neutrons, and other hadron particles.
What is all this stuff about the Standard Model then?
All things in this world are constituted by atoms. Atoms, in turn, are made up of protons, neutrons and electrons. These particles are made up of even smaller subatomic particles. The Standard Model was able to explain the interactions between these subatomic particles and hence provided the basis for the explanations of electricity, magnetism and radioactivity. However, the Standard Model, before the discovery of the Higgs boson, was unable to provide evidence for how these particles gained mass.
This is where the Higgs field comes into play. Like I mentioned earlier, some particles interact with this field, while some do not. The ones that do not interact with this field, like the photons, do not gain mass and can hence travel at the speed of light. The ones that do interact with this field, like the electrons, gain mass through the interactions. Think of it this way, if the Higgs field did not exist, there would be no interactions with the field and therefore, all subatomic particles would have no mass.
Why is the Higgs Boson called the God particle?
Perhaps, the term ‘God particle’ is justified. The Higgs boson helped fill a large hole in the Standard Model and is considered to have provided evidence that proves a large number of phenomena. In some sense, this particle is truly Godly!
But, the term ‘God particle’ arises from the title of Leon Lederman’s book, ‘The God Particle’, in which, the Higgs boson is the primary subject of discussion. Leon Lederman is credited with providing this particular title to the particle. But, the story is actually even more fascinating. Lederman wanted to title his book as ‘The Goddamn Particle’ because of how difficult it is to find the particle and actually prove its existence. His publishers, however, would not allow for such an audacious title and the book was then titled ‘The God Particle’.
Is this particle dangerous? Can it prove to be detrimental?
Stephen Hawking has cautioned the world about the potential dangers that the Higgs boson might harbour. Some researchers believe that this particle could lead to the destruction of the universe. However, this destruction will not take place anytime soon. These researchers estimate that this catastrophe is at least billions of years away. The mass of the Higgs field will be to blame if this occurs. Since the Higgs field is present everywhere, even a small change in its mass would cause major instability in the universe, causing the universe to collapse.
Six years ago today, physicists at the Large Hadron Collider announced the detection of the Higgs Boson, completing the Standard Model of Particle Physics and possibly indicating a disastrous fate for our Universe. https://t.co/UdtB3yD8ef#Higgs#VacuumDecay
In conclusion, the Higgs boson is the result of the excitation of the Higgs field. The Higgs field is a scalar field that provides mass to the subatomic particles that interact with it. Without the Higgs field, all subatomic particles would have no mass. This entire mechanism was suggested by Peter Higgs and five other scientists in 1964. The Higgs boson, however, was not discovered until 2012, when it was first discovered by the Large Hadron Collider, which, is a particle accelerator. The name ‘God particle’ was the result of Lederman’s similarly titled book about the Higgs boson.
Although the ‘God particle’ certainly seems to be a misnomer, the name given to the Higgs boson might have done the world a whole lot of good. The title given to the particle has ensured that more and more people look for the Higgs boson on the internet and try to understand what it means and how much effort has been put in, to find it. The name, ‘God particle’ could even be the reason why you are currently reading this. Any scientist would give you the death stare for calling the Higgs boson, the ‘God particle’, but, maybe the name is not so bad after all. Perhaps, the magnitude of the reception of the news of the discovery of Higgs boson should be entirely credited to this misnomer!
February 5, 2019(updated July 10, 2019) Published by Kshitij Kumar
Wormholes have served as fodder for numerous science fiction stories and movies for quite some time now. There have been several theories that try to explain how wormholes work and several more on how time travel could be made possible through these wormholes. Much like black holes, wormholes are beguiling and tend to leave people mesmerized with the intricacies. If you have ever wondered about what these things are, or, if you want to better understand all their alluring intricacies, then, this article is exactly what you need. Read on to learn more about the splendour of these mysterious bodies.
Wormholes can be visualized as portals that can allow entities to travel through space and time. Black holes consist of a point of singularity where all mass is said to accumulate. These black holes consume anything in their proximity. Scientists hypothesize that there also exists a white hole at the other end of a black hole. These white holes spit out the matter, and light, absorbed by the black hole. The entry point and the exit point exist as separate points in the universe. The bridges that link two separate points in space-time are referred to as Einstein-Rosen bridges. This phenomenon of the existence of bridges was predicted in 1935 when Albert Einstein and Nathan Rosen published a paper showing the existence of a corridor or passage directly connecting one part of the universe to another as part of a black hole-white hole system.
These bridges, however, are highly unstable and tend to collapse due to the influence of the gravitational force on them. A wormhole, in this context, is a passage from one point in space-time to another. Each wormhole is expected to have two mouths and a neck, that, serves as a bridge between the two mouths. Proposedly, one mouth of a wormhole is a black hole and at the other mouth is a white hole. Both black holes and white holes are solutions to Einstein’s field equations.
A black hole is Schwarzschild’s solution to Einstein’s field equations. Ludwig Flamm discovered the presence of another solution to these field equations while understanding the Schwarzschild’s solution, and this solution was referred to as the white hole. There exists a parameter, called the Schwarzschild’s radius for every entity with mass. This radius is the radius of a sphere such that if all the mass of an object were to be compressed within the sphere of radius equal to the Schwarzschild’s radius, the escape velocity from the surface of the object would equal to the speed of light.
“Embedding diagram” of a Schwarzschild wormhole (Source: wikipedia.org)
Mathematically it could be represented as,
R = 2GM/c2
R is the Schwarzschild’s radius, G is the gravitational constant, c is the speed of light, and M the mass of the black hole.
To understand a wormhole through better visualization, we would have to consider the analogy of a piece of paper consisting of two points on it. The two points represent different points in space-time. For those of you who are absolutely tired of hearing about this analogy (in various movies or explanations), skip the next couple of lines.
For those of you who have not heard of this analogy, pay attention. When the paper is not bent or folded, there is a certain distance between the two points. Now, imagine that the paper is folded, poking a pencil through the paper to connect the two points would provide a shortcut between the points. This distance is seemingly much lesser than the distance between the points had the paper not been folded. A wormhole works in a similar manner to this shortcut. It provides a shortcut between two points in space-time. These points could even belong to different universes.
Wormhole visualized (Credit: Wikimedia Commons)
Wormholes have not been discovered yet. In theory, their existence is proven, but, nobody has ever found one.
Many physicists and astronomers believe that the supermassive black holes that exist at the centre of most galaxies could potentially be wormholes.
Wormhole vs Black Hole
What’s the difference between black holes and wormholes? Like I have mentioned, wormholes are better explained as passages while a black hole is just a mouth to this passage. Before I get to the specific differences, let’s look at some of the similarities between the two. Both are mathematically consistent. Both distort space and thus both should have matter swirling around them. Both are immensely fascinating, and both have not been fully understood!
This artist’s concept illustrates a supermassive black hole with millions to billions of times the mass of our sun. (Source: NASA JPL)
Now, let’s get to the differences between the two. Recently, we got an image of a black hole whereas wormhole is yet to be found. One more distinguishing factor between black holes and wormholes is the Hawking radiation. Black holes lose energy continuously through the emission of Hawking radiation. This emission is initially slow and builds speed as the process continues. Only black holes are said to emit this Hawking radiation.
Another difference is the lack of an event horizon in wormholes. The event horizon of a black hole is its boundary. To escape from within a black hole, one would have to travel faster than light, at speeds greater than the escape velocity of the black hole.
In black holes, there is no point of return. Once you enter a black hole, there is no escaping it. On the other hand, when you travel through a wormhole, if the wormhole is kept open for a sufficiently long enough time, you could potentially travel back to the same place through the same wormhole. There is a lot of controversy over this theory though since you would not end up going back to the same point in space-time that you initially started at.
Take the below question to quickly test your understanding of wormholes and black holes
How much is the escape speed in Schwarzschild radius?
The escape velocity from the surface (i.e., the event horizon) of a Black Hole is exactly c, the speed of light. Actually, the very prediction of the existence of black holes was based on the idea that there could be objects with escape velocity equal to c.
Perhaps, the most distinguishing aspect is the fact that wormholes are purely theoretical, while black holes are proven to exist. A black hole is a massive dent in the fabric of space-time that seems to cause a puncture in it. Anything that enters this puncture is consumed and is present at a single point of singularity. A wormhole, on the other hand, can be considered as two punctures in space-time that are connected to one another. The two punctures could exist as any two points in space-time.
Problems with travel through wormholes
The problems with travel through wormholes arise due to their size and stability. Primordial wormholes are considered to be so small that they are microscopic in nature. Travelling through microscopic wormholes would be highly impossible.
The other problem is the stability of wormholes. Wormholes, under the influence of gravitational forces, tend to collapse rather easily. In order to travel through these wormholes, wormholes should remain open. This requires the presence of Exotic Matter, which, I will cover in the next section. However, this exotic matter also only exists in theory. Keeping a wormhole open is a daunting challenge, indeed.
Keeping a wormhole open
In the case of wormholes that are existent through the explanations of the string theory, the wormholes are kept open by cosmic strings. In the case of man-made and other wormholes, they would have to be kept open by exotic matter. Exotic matter is a special kind of hypothesized matter. The exotic matter has negative mass. This means that it is repulsive in nature. Positive masses that exist in this universe tend to attract each other, while exotic matter tends to repel.
Due to the presence of gravity, it would not be easy for wormholes to remain open. This exotic matter can counter gravity and allow wormholes to remain open. Exotic matter can be used to weave space and time and sustain wormholes. One candidate for the exotic matter is the vacuum of space.
To understand why the vacuum of empty space could be a potential candidate, you will first have to understand why empty space is not empty. Empty space consists of several virtual particles that are randomly generated. These particles cancel each other out, in pairs. Each pair is said to be a particle-antiparticle pair.
This property, where pairs of particles cancel each other out, can be manipulated to produce similar pairs of matter that cancel each other out. Exotic matter can thus be produced. The exotic matter would provide a great deal of help in the stabilization of wormholes by keeping them open.
Exotic matter, unlike regular matter, would accelerate in directions opposite to the applied force. Despite its peculiar properties and its deviation from the behaviour of normal matter, it is not inconsistent mathematically. It also does not violate the principles of conservation of energy or momentum.
For exotic matter, the mass-energy equivalence would be represented as,
E = -mc2
E represents energy
m represents mass and
c2 is the coefficient of proportionality where c is the speed of light.
The concept that interstellar travel is possible, is most certainly enthralling. The possibilities that can be unlocked through the travel in space-time are enormous and could change how we view the universe entirely. Through such travel, the vastness of the universe could be diminished. We could travel across galaxies and universes and unlock so many secrets of the universe. Although space-time travel has enormous potential, we are hindered by the fact that wormholes, at least for now, only exist in theory.
Eleanor Roosevelt, the former First Lady of the United States once said, “The future belongs to those who believe in the beauty of their dreams”. Maybe, one day we will uncover the secrets of the universe through space-time travel and view the universe in all its glory. Until then, we will have to settle for these dreams of what could be.
February 5, 2019(updated August 24, 2019) Published by Kshitij Kumar
There are a lot of objects and bodies that exist in this gargantuan universe of ours. Everything in this vast abode that we call the universe, whether big or small, is said to consist of matter. Your phone, your body, your hair, dust, air and everything you see around is matter. Each and every one of these objects consists of matter and their existence can generally be perceived rather easily.
Estimated division of total energy in the universe into matter, dark matter and dark energy based on five years of WMAP data (Credit: Wikipedia)
But what if I told you that most of the matter that exists in the universe cannot be perceived? What if I also told you that more than 85% of the matter in the universe has never been observed? These facts are hard to believe and are rather astounding, but, they are, indeed, facts. There is a special kind of matter called Dark matter, which constitutes about 85% of all the mass of universe and has never been observed directly.
Indeed, talking about the energy composition the universe is composed of roughly 4.6% matter, 23% dark matter and 72% dark energy (this is energy composition not to be confused with the above-mentioned mass composition). It is thought that we can neither detect nor measure dark energy but we can clearly see its implications. Let us talk about Dark matter in this blog and keep Dark energy aside for another blog.
To understand about Dark Matter, you have to understand about Matter first. The matter is something that has mass and occupies space. Matter can exist in any form or state. There are seven states of matter and they are:
Matter consists of atoms, or, to be precise, the matter is made up of protons, neutrons, and electrons. This matter is called “Ordinary Matter”. The sub-atomic particles are built with some fundamental particles. These particles can be put into two groups: fermions and bosons. Fermions are the building blocks of matter. They all obey the Pauli exclusion principle. Bosons are force-carriers. They carry the electromagnetic, strong, and weak forces between fermions.
Fermions can be put into two categories: quarks and leptons. Quarks make up, amongst other things, the protons and neutrons in the nucleus. Leptons include electrons and neutrinos. The difference between quarks and leptons is that quarks interact with the strong nuclear force, whereas leptons do not.
There are four bosons in the right-hand column of the standard model. The photon carries the electromagnetic force – photons are responsible for electromagnetic radiation, electric fields and magnetic fields. The gluon carries the strong nuclear force – they ‘glue’ quarks together to make up larger non-fundamental particles. The W+, W– and Z0 bosons carry the weak nuclear force. When one quark changes into another quark, it gives off one of these bosons, which in turn decays into fermions.
All the above particles make up the Standard Model of particles and dark matter doesn’t come in this standard model
There are many observations which strongly suggests the presence of some strange non-luminous matter or the dark matter. Let us see some of them:
The speed of bodies located farther from the galactic centre: From Kepler’s Second Law, it is expected that the rotation velocities will decrease with increase in the the distance from the centre of the galaxy, similar to the Solar System. This is not observed and the only obvious reason we could find is the presence of Dark matter.
Mass velocity discrepancy: Stars in bound systems must obey the Virial theorem which together with the measured velocity distribution, can be used to measure the mass distribution in a bound system, such as elliptical galaxies or globular clusters. However, some velocity dispersion estimates of elliptical galaxies do not match the predicted velocity dispersion from the observed mass distribution. This discrepancy also tells that there is some extra invisible mass out there.
Gravitational Lensing: Galaxies and other huge interstellar objects act as a lens and bends light. Actually, these massive things distort or bend the fabric of space-time and light passing through this distortion bends. So, the bending of light clearly depends on the mass of the galaxy. Researchers have made many such observations of light coming from quasars through some galaxy clusters. The bending of that light clearly tells that there is some extra mass out there.
Cosmic Microwave Background: The Cosmic Microwave Background radiation or CMB for short is basically electromagnetic radiation which has been travelling for these 14 billion years since the big bang. This has the temperature data also. Scientists have collected a lot of data from this radiation and created a map. This map perfectly matches with the Dark matter model and clearly tells that the universe cannot exist without Dark Matter.
9-year WMAP image of cosmic microwave background (Credit: NASA)
Like this, there are many other proofs but these four are the most prominent proofs for the existence of some unknown and invisible matter out there.
Types of dark matter
The classification of dark matter is based on its velocities. Free streaming length (FSL) is used to describe the distance objects would travel due to the random motions in the early universe. The size of a protogalaxy is used for determining the category of dark matter.
Cold dark matter: Dark matter whose constituents have an FSL less than the size of a protogalaxy.
Warm dark matter: Dark matter whose constituents have an FSL comparable to the size of a protogalaxy.
Hot dark matter: Dark matter whose constituents have an FSL greater than the size of a protogalaxy.
Why should we find dark matter?
Dark matter constitutes 85% of the Universe’s Mass and it is present in really huge quantity and a lot of it might be present here on earth as well. If detected, we could probably use it for energy production and many other unbelievable applications might come up.
Other than applications, dark matter could unveil some of the dark secrets of the universe which are lying unanswered for centuries.
What could dark matter be made of?
There are several theories about what dark matter could be made of and some of them are:
WIMPs(Weakly interacting massive particles): WIMPs are hypothetical particles that are thought to make the dark matter. These are totally new particles interacting through weak forces which are probably weaker than the weak nuclear force. These particles are not included in the above-mentioned standard model. Researchers are trying and developing a lot of experiments to detect such particles.
Axions: Axion is another hypothetical elementary particle. It was actually postulated to solve the strong CP problem in quantum chromodynamics. Scientists believe that if they axions exist and have some specific properties then they can be a possible component of dark matter.
Like this, there are many proposed things and to understand all these hypothetical particles, we need a deeper understanding of physics. There are theories also saying that the current understanding of gravity itself is wrong and should be modified according to the observations but there are limitations to this also.
How could we detect dark matter?
We can locate the places in the universe where dark matter is present using techniques like Gravitational Lensing and we can even create the model of galaxies including dark matter. But we are not yet able to detect the particles which make this dark matter. So, how could we detect dark matter? Let us discuss the possible approaches. Basically, there are three approaches and they are:
Large Underground Xenon detector inside watertank (Credit: Wikipedia)
Make it here: Physicists have been bombarding particles in accelerators like LHC and there is a hope that someday we create dark matter particles and hopefully detect them.
Direct Detection: Considering the amount of dark matter present in the universe, there is a possibility that dark matter is present here on earth as well and there is a possibility that some sensitive detector could detect it. So, scientists have been building extremely sensitive detectors to detect dark matter. One such detector is The Large UndergroundXenon experiment (LUX) aimed to directly detect weakly interacting massive particle (WIMP) interactions with the ordinary matter on Earth
Dark matter collisions: Scientists believe that collisions of dark matter could probably release something which we could detect. So, researchers are trying to use this approach as well.
The Pauli's Exclusion principle states that two electrons in same orbitals have:
The Pauli Exclusion Principle states that, in an atom or molecule, no two electrons can have the same four electronic quantum numbers. As an orbital can contain a maximum of only two electrons, the two electrons must have opposing spins.
Why is dark matter still a mystery?
While dark matter is the simplest explanation for the extra gravity and mass that exists, it is not necessarily the correct explanation. There are several theories that claim to explain this extra gravity and mass in the universe. Nobody really knows for sure if the existence of dark matter is a sufficient enough explanation for the existence of the extra mass. Dark matter does not give off light and as I have mentioned, does not interact with particles. Without any interactions, it is extremely hard to derive any conclusions on its nature and properties.
A recent paper in the physical review journals gave the maths claiming that dark matter might be created before the big bang itself which ads another mystery to the already existing mysteries around dark matter
Dark matter may be considered as the universe’s biggest mystery. It is known that something makes objects faster than they should but we do not actually know what it is and where it came from. The origins of dark matter might be even more peculiar than it is known.
Jonathon Swift, an Anglo-Irish poet once said, “Vision is the art of seeing what is invisible to the others”. Dark matter may be invisible, but it has served to solve a lot of mysteries in this astonishingly mysterious universe. Without the invisible phenomenon of dark matter, there would still be a lot of perplexity regarding the formation of galaxies and their movements. Despite all the information we possess about the universe, nobody can say with certainty that dark matter exists. Perhaps, that is where the magnificence of physics lies, in its mystery, and this mystery is what makes the search for the truth worthwhile.
February 5, 2019(updated July 10, 2019) Published by Kshitij Kumar
Gravitational waves were proposed by Henri Poincaré in 1905 and subsequently predicted in 1916 by Albert Einstein on the basis of his general theory of relativity. There are so many aspects of physics that are aesthetically pleasing. These aspects are not necessarily pleasing due to their visible or on the surface features, rather, they are aesthetically pleasing in their detail. Gravitational waves are certainly one such phenomenon. They have immense importance, and their impact in understanding the theories of physics is considerably high.
Gravitational waves are ripples in the fabric of space-time that are formed due to the acceleration of masses. These ripples propagate outwards from the source of mass. One must understand that distortions are created in the fabric of space-time by bodies of mass. To visualize this concept, think of this fabric as a piece of paper or a blanket, with people holding on to it from all sides. When an object of mass is placed on the paper or blanket, there is a visible dent or distortion of the shape of the paper or blanket at the position where the object was placed. Now when these bodies of mass are moved about, that is, they are provided acceleration, these distortions also move about in the fabric of space-time. These accelerated bodies lead to the formation of waves in space-time. These waves are the gravitational waves.
As you would imagine, larger bodies tend to create larger intensity waves. Theoretically, any movement of a body having mass can cause these ripples. A person walking on the pavement, in theory, also causes these ripples. However, these ripples caused by a walking person are very minuscule and insignificant.
So, what is space-time?
The universe was long thought to be consisting of the three dimensions of space only. But, Albert Einstein proved that the universe consisted of a fourth dimension, time. It would be impossible to move in space without moving in time. Similarly, it would also be impossible to move in time without moving in space. Space and time, therefore, have a very integral relationship. Einstein stated that there is a profound link between motion through space and passage through time. He hypothesized that time is relative. Objects in motion experience time slower than objects at rest.
The three dimensions of space and the dimension of time are viewed as the four-dimensional space-time. Hermann Minkowski provided a geometric interpretation that fused the three dimensions of space and the dimension of time to form the space-time continuum. This was called the Minkowski space.
Minkowski Space Illustration. Image Source: Wikipedia
In three dimensional space, the distance, D between any two points can be represented using the Pythagorean theorem as:
D2=(Δx)2 + (Δy)2 + (Δz)2
Δx represents the difference in the first dimension, Δy represents the difference in the second dimension and Δz represents the difference in the third dimension
The spacetime difference of two points given by (Δs)2 varying by time Δt would be given as:
(Δs)2=(Δct)2 – (Δx)2 + (Δy)2 + (Δz)2
c is a constant, representing the speed of light that enables conversion of units used to measure time to units used to measure space.
Gravitational pull and formation of waves
Every body that has mass tends to attract other bodies. Whether the mass is small or large, every body exerts a force on the other. This attraction is the gravitational pull. The greater the mass of the object, the larger its gravitational pull. The larger the distance of an object from another object, the lower its gravitational pull on it. Since every object, however large or small, tends to exert this pull on every other object, changes in gravity can provide insight into the behaviour of these objects.
If the distance between two bodies is doubled, the force of attraction F between them will be:
Since the force of gravity acting between any two objects is inversely proportional to the square of the separation distance between the object's centers, Force F will be reduced by 1/2 x 1/2 = 1/4 times.
Consider the earlier example of the distortion caused by placing an object on paper or blanket, now, if we were to place a larger object, this would result in an even larger distortion. The larger object would cause a larger depression in the paper or blanket and hence, is said to have larger gravity. If the two objects were placed on the paper or blanket together, the larger object with the larger distortion would seem to be exerting a larger force of attraction towards the other object. If these objects moved, there would be ripples formed on the paper or blanket. This is similar to how gravitational waves are formed, the only difference being that the paper or blanket would be replaced by the fabric of space-time.
These gravitational waves cannot be felt easily. To detect these, you would require special equipment. These detectors are L shaped instruments with generally long arms.
Detection of gravitational waves
Gravitational waves were first witnessed in September 2015. Scientists observed the waves that were a result of two black holes colliding. These black holes were said to possess masses several times that of the sun. The black holes were attracted to each other due to the gravitational forces and slowly, over the course of several years, began to spiral into each other. One day, they finally merged. Before they merged, they let out gravitational waves that were felt on earth billions of years later in 2015.
This was picked up by a detector called Laser Interferometer Gravitational Wave Observatory (LIGO). This signal was very short lived and lasted only a fifth of a second. These wobbles in space-time picked up by the LIGO was thousands of times smaller than the nuclei of atoms. This is because the gravitational waves over the course of time gradually became weaker. The Laser Interferometers were configured in such a way that even these small ripples could be picked up.
LIGO consists of two gigantic laser interferometers located thousands of kilometres apart. Each detector consists of two 4km long steel vacuum tubes arranged in an ‘L’ shape. A special covering is provided to these tubes to ensure protection from the environment.
Aerial view of the LIGO Hanford Observatory. (Source: Caltech/MIT/LIGO Laboratory)
These tubes are the arms. The lengths of these arms are measured with lasers. If the lengths are changing, this could be due to compression and relaxation of arms due to gravitational waves. Studying these gravitational waves enables scientists to derive certain information about the objects that produced them. Information such as the mass and size of the orbit of the object that created the wave can be extracted from studying these gravitational waves. In the year 2017, The Nobel Prize in Physics was received by Rainer Weiss, Kip Thorne and Barry Barish for their role in the detection of gravitational waves.
Today, LIGO is trying to detect Gravitational waves with even more sensitive instruments in hope to detect more merging neutron stars and black holes and maybe some new discoveries too
These gravitational waves help scientists gain information about the physical properties of the objects that created the waves. These gravitational waves provide a new way to observe the universe. A way that never existed previously.
The detection of the gravitational waves allows us to understand interactions in the universe in a completely new way. The waves detectable by LIGO are waves generated due to the collision of two black holes, exploding stars, or perhaps the birth of the Universe.
Before this form of understanding the universe was realized, most observations of the universe were made based on electromagnetic radiation. Something like the collision of black holes would have been impossible to have been picked up by electromagnetic radiation.
A major difference between gravitational waves and electromagnetic waves is the fact that gravitational waves interact very weakly with matter. Electromagnetic radiation, on the other hand, reacts strongly with matter and could face several alterations in its properties. Gravitational waves can travel through the universe virtually unimpeded.
The information, such as the mass and orbit of the object that caused the waves could be understood in a clearer manner. The information carried by the waves is free from any alterations or distortions that result from interaction with matter present in the universe.
The gravitational waves can also penetrate regions of space that electromagnetic radiation cannot. These properties have led to the creation of a new field of astronomy, called gravitational field astronomy. Gravitational field astronomy aims to study large entities in the universe and their interactions through unadulterated properties of gravitational waves.
Famous basketball player, John Wooden once said, “It’s the little things that are vital. Little things make big things happen”. In the case of gravitational waves, the little things are the ones that provide the knowledge of the larger things. Little observations made on the properties and complexities of the gravitational waves are what gives rise to the details pertaining to the larger bodies existing in the universe. There is no denying the fruitfulness of the existence of gravitational waves. One can even go so far as to say that gravitational waves have revolutionized physics. I can say without a cloud of uncertainty that gravitational waves will surely help us uncover more secrets of the universe in the future.
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