March 13, 2019(updated March 13, 2019) Published by Kshitij Kumar
NASA has recently spotted layers of water molecules on the moon’s surface by the spacecraft Lunar Reconnaissance Orbiter (LRO). The LRO has observed water molecules moving around during dayside on Moon. It was astonishing as scientists thought that the Moon was dry and arid, water only exists in the form of shaded craters near the poles.
According to the paper published in Geophysical Research Letters, The instrument Lyman Alpha Mapping Project (LAMP) was responsible for measuring sparse layer of molecules temporarily stuck to the Moon’s surface, which helped to measure lunar hydration, changes over the course of a day.
Scientists have discovered surface water in sparse populations of molecules bound to the lunar soil, or regolith. But, the amount and locations were found to vary based on the time of day. The lunar water is more common at higher latitudes and tends to bounce around when the temperature of surface soars up.
Earlier the scientists had assumed that hydrogen ions in the solar wind may be the source of most of the Moon’s surface water. But when the Moon passes behind the Earth and is shielded from the solar wind, the “water spigot” should necessarily turn off.
Surprisingly, the water identified by LAMP does not decrease when the Moon is shielded by the Earth and the region influenced by its magnetic field, suggesting water builds up over time, rather than “raining” down directly from the solar wind.
John Keller, LRO deputy project scientist from NASA’s Goddard Space Flight Centre in Maryland said, “The study is an important step in advancing the water story on the Moon and is a result of years of accumulated data from the LRO mission”.
Artist concept of NASA’s Lunar Reconnaissance Orbiter. (Credit: NASA)
Dr. Kurt Retherford, the principal investigator of the LAMP instrument from Southwest Research Institute in San Antonio, Texas addressed, “This is an important new result about lunar water, a hot topic as our nation’s space program returns to a focus on lunar exploration. We recently converted the LAMP’s light collection mode to measure reflected signals on the lunar dayside with more precision, allowing us to track more accurately where the water is and how much is present.”
“These results aid in understanding the lunar water cycle and will ultimately help us learn about the accessibility of water that can be used by humans in future missions to the Moon,” said lead author Amanda Hendrix, a senior scientist at the Planetary Science Institute and lead author of the paper.
“Lunar water can potentially be used by humans to make fuel or to use for radiation shielding or thermal management; if these materials do not need to be launched from Earth, that makes these future missions more affordable,” she added.
March 10, 2019(updated March 10, 2019) Published by Kshitij Kumar
The new calculation of the measurement of the size and mass of the Milky Way is more accurate and the galaxy turned out to be more massive than thought earlier.
The galaxy has been calculated to have a mass of about 1.5 trillion Sun’s worth of mass (solar masses) within a radius of around 129,000 light years. This calculation exceeds over twice as much as previous estimates of 2016’s study in which it was estimated to have around 700 billion solar masses.
To accurately map the Milky Way in three dimensions, ESA’s Gaia Mission has been launched. This mission has given the most detailed map of our home galaxy ever made and has been refining our knowledge all over the shop.
A search team has been able to infer the galaxy’s size and mass based on the orbital motion of groups of stars called globular clusters, out in the galactic halo by combining Gaia data with those from Hubble Space Telescope observations.
The Hubble Space Telescope as seen from the departing Space Shuttle Atlantis, flying STS-125, HST Servicing Mission 4. Image Credit: Wikimedia/ Ruffnax (Crew of STS-125)
With the dark matter in play, the mass of the Milky Way can’t just be guessed based on what we can see. And the dark matter cannot be detected directly. But there is an assumption that something is out there, because of the orbital velocity of the outer region of the galaxy.
The matter orbits much faster than it should, based on the matter that can be detected – as though something, some undetectable mass, is creating extra gravity in the Universe.
It is important to infer its mass based on other methods because the dark matter can’t be observed directly. By starting with that outer-galaxy orbital velocity, astrophysicists can work backward to calculate the mass responsible, based on Kepler’s laws of orbital motion.
On the same subject, Gaia and Hubble are dedicated to working. It has been 10 years since they have been combined. And they have provided more accurate measurements of the orbital motion of globular clusters in the outer reaches of the Milky Way.
“The more massive a galaxy, the faster its clusters move under the pull of its gravity,” said astrophysicist Wyn Evans of the University of Cambridge in the UK.
“Most previous measurements have found the speed at which a cluster is approaching or receding from Earth that is the velocity along our line of sight. However, we were able to also measure the sideways motion of the clusters, from which the total velocity, and consequently the galactic mass, can be calculated.”
On this basis, the team reached the 1.5 trillion solar masses figure. But the thing is that there are only about 200 billion stars in the galaxy. Sagittarius A*, the supermassive black hole at the galactic center, accounts for another 4 million solar masses. And there’s a bunch of dust and gas. But all that concludes around 90% of the mass meaning, there is the dark matter that is yet to be found out.
“We want to know the mass of the Milky Way more accurately so that we can put it into a cosmological context and compare it to simulations of galaxies in the evolving universe,” explained physicist Roeland van der Marel of the Space Telescope Science Institute in the US.
The Milky Way galaxy has been noted to be in an intermediate range according to the new measurements put it at a pretty healthy size and mass for its class, but the extra heft doesn’t even put us near the biggest galaxies – those are in the range of 30 trillion solar masses.
For many years, the Milky Way has been thought to the biggest galaxy in nearby intergalactic space was Andromeda, with the Milky Way coming in second.
But according to Andromeda’s new calculations last year, the Milky Way was put to be at around 800 billion solar masses which could mean that it is actually number one – and has been all along. And so, rather than the other way around as we previously thought, it could mean that Andromeda gets subsumed into the Milky Way when the pair collide in 4.5 billion years.
The astronauts aboard the International Space Station (ISS) are scheduled to conduct the first all-female spacewalk on March 29 if it goes according to the plan. These astounding women are Anne McClain and Christina Koch. They will set out on a space venture together for about 400 km above the Earth and make history.
According to the significance of their mission, the spacewalk will take place during Women’s History Month.
“It was not orchestrated to be this way,” said NASA spokeswoman Stephanie Schierholz. “These spacewalks were originally scheduled to take place in the fall — they are to upgrade batteries on the space station.”
This spacewalk of McClain and Koch’s will be the second of three planned excursions for Expedition 59. This spacewalk is supposed to be launched next week on the very Pi Day at 3:14 pm ET (8:14 pm UTC).
One NASA flight controller expressed her excitement about working on the mission.
Koch, on the other hand, is an electrical engineer and she is supposed to join McClain on March 14 and have her first ever space flight, according to NASA. Space is just the latest exciting frontier Koch has conquered: her work and passion have taken her on expeditions to the South Pole and the Arctic.
She was asked in a February interview about the importance of conducting her mission during Women’s History Month. On this, she said, “It is a unique opportunity, and I hope that I’m able to inspire folks that might be watching.”
Noting she did not have many engineers to look up to growing up in Jacksonville, North Carolina., she added, “I hope that I can be an example to people that might not have someone to look at as a mentor … that it doesn’t matter where you come from or what examples there might be around you, you can actually achieve whatever you’re passionate about.”
“If that’s a role that I can serve,” she said, “it would be my honor to do that.”
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.
At the fifth Kepler/K2 Science Conference which was held in Glendale, CA on Tuesday, March 5th 2019, Ashley Chontos, an astronomer of NASA’s Kepler Mission announced the confirmed identification of the first exoplanet candidate.
The Kepler Telescope was launched by NASA almost exactly 10 years ago. The mission was designed specifically to survey the region of the Milky Way galaxy to discover hundreds of Earth-size and smaller planets in or near the habitable zone and so far, it has done its best. It is in search of hundreds of billions of stars in our galaxy that might have such planets.
The Kepler-1658b was the first planet candidate discovered by the Kepler Telescope and so it was named after its telescope, which by the way characterized as a big star by the Kepler data later recorded.
It came out to be three times larger than previously thought. “Our new analysis, which uses stellar sound waves observed in the Kepler data to characterize the host star, demonstrated that the star is in fact three times larger than previously thought. This in turn means that the planet is three times larger, revealing that Kepler-1658b is actually a hot Jupiter-like planet,” said Chontos.
Illustration of NASA’s Kepler telescope. (Credit: NASA)
Although the team of astronomers led by Chontos had refined analysis and everything pointed to the object truly being a planet, but confirmation from new observation was still needed.
“We alerted Dave Latham (a senior astronomer at the Smithsonian Astrophysical Observatory, and co-author on the paper) and his team collected the necessary spectroscopic data to unambiguously show that Kepler-1658b is a planet,” said Dan Huber, co-author and astronomer at the University of Hawaii. “As one of the pioneers of exoplanet science and a key figure behind the Kepler mission, it was particularly fitting to have Dave be part of this confirmation.”
Being three times larger in size than the Sun itself, Kepler-1658b is 50% more massive. It is one of the closest-in planets around a more evolved star orbiting at a distance of only twice the star’s diameter. As seen from the earth, the star would appear to be 60 times larger in diameter of the Sun if one is standing on the planet.
It is however, very rare for a planet similar to Kepler-1658b to orbit around an evolved star and the reason for this absence is poorly understood yet. The extreme nature of the Kepler-1658b system allows astronomers to place new constraints on the complex physical interactions that can cause planets to spiral into their host stars.
According to the studies and insights gained from Kepler-1658b, this process happens slower than thought earlier. Although, this might not be the primary reason for the lack of planets existing around more evolved stars.
“Kepler-1658b is a perfect example of why a better understanding of host stars of exoplanets is so important.” said Chontos. “It also tells us that there are many treasures left to be found in the Kepler data.”
About NASA’s Kepler Space Telescope
About Kepler Mission: Launched in 2009, the Kepler mission is specifically designed to survey the region of the Milky Way galaxy in order discover hundreds of Earth-sized and smaller planets in or near the habitable zone and determine hundreds of billions of stars in our galaxy that might have such planets.
Scientists in Geneva have declared, lately, that they have perceived the first ever evidence of an ancient groundwater system consisting of interconnected lakes on Mars. These interconnected lakes lay deep beneath the planet’s surface, five of which may have minerals vital for survival.
Although Mars appears to be a sterile land, its surface shows potent signs that once there were large quantities of water existing on the planet.
Researches and researchers have said that the history of water on Mars has been a complicated topic, and is intricately associated with understanding whether or not life ever arose there – and, if so, where, when, and how it did so.
The recent study, which was earlier predicted by models, says that: “Early Mars was a watery world, but as the planet’s climate changed, this water retreated below the surface to form pools and groundwater“.
The lead author Francesco Salese of Utrecht University, further added – “We traced this water in our study, as its scale and role is a matter of debate, and we found the first geological evidence of a planet-wide groundwater system on Mars”.
Salese and his colleagues explored 24 deep, enclosed craters in the northern hemisphere of Mars, with floors lying roughly 4000 meters below Martian ‘sea level’ (a level that, given the planet’s lack of seas, is arbitrarily defined on Mars based on elevation and atmospheric pressure).
How Mars Express gathered evidence for groundwater on Mars. (Source: NASA/JPL-CALTECH/MSSS; DIAGRAM ADAPTED FROM F. SALESE ET AL. (2019))
They found features on the floors of these craters that could only have formed in the presence of water. Many craters contain multiple features, all at depths of 4000 to 4500 meters – indicating that these craters once contained pools and flows of water that transformed and diminished over time.
These features include channels etched into crater walls, valleys carved out by sapping groundwater, dark, curved deltas thought to have formed as water levels rose and fell ridged terraces within crater walls formed by standing water, and fan-shaped deposits of sediment associated with flowing water. The water level aligns with the proposed shorelines of a putative Martian ocean thought to have existed on Mars between three and four billion years ago.
“We think that this ocean may have connected to a system of underground lakes that spread across the entire planet,” adds co-author Gian Gabriele Ori, director of the Università D’Annunzio’s International Research School of Planetary Sciences, Italy.
“These lakes would have existed around 3.5 billion years ago, so may have been contemporaries of a Martian ocean.”
Exploring these sites reveal the conditions suitable for finding past life, and are therefore highly relevant to astrobiological missions such as ExoMars – a joint ESA and Roscosmosendeavor. While the ExoMars Trace Gas Orbiter is already studying Mars from above, the next mission will launch next year.
ExoMars Trace Gas Orbiter, seen at ESOC in Darmstadt, Germany (Source: wikimedia.org)
Mars Express was launched on 2 June 2003 and reached 15 years in space in 2018. The studies and researches conducted lately, have been proved to be fruitful as we have got some really good results from them.
February 5, 2019(updated September 6, 2019) Published by Kshitij Kumar
Aliens and their types, as well as visitors to our planet, has been a matter of study for scientists and many other researchers for a number of years now. It has been a subject of interest for the movie-makers as well as the common public, and that is why from various corners of our planet frequent news of the visit of aliens and their various proofs of presence come forward.
All think of human being, as the most intelligent, technologically advanced species in the whole universe. But when you see things upside down, there are more than 400 billion stars in our own galaxy – Milky Way only, and there are more than two trillion galaxies in the whole universe. Now it may seem that life can be inevitable in some of these places.
So, let us discuss all the prospects of possible alien life in the universe and what all we know about it. Let us go through different theories and findings around extraterrestrial life.
Number of possible technologically advanced civilizations – Drake’s Equation
What do we need to know about to discover life in this huge cosmos? How can we estimate the number of technologically advanced civilizations that might exist among the stars? While working as a radio astronomer at the National Radio Astronomy Observatory in Green Bank, West Virginia, Dr. Frank Drake conceived an approach to give limits to the terms involved in estimating the number of technological civilizations that may exist in our galaxy. The Drake Equation, as it has become known, was first presented by Frank Drake in 1961 and identifies specific factors which are thought to play a role in the development of such civilizations. Although there is no unique solution to this equation, it is a generally accepted tool used by the scientific community to examine these factors.
Drake’s equation (Credit: SETI Institute)
N = The number of civilizations in the Milky Way Galaxy whose electromagnetic emissions are detectable.
R* = The rate of formation of stars suitable for the development of intelligent life.
fp = The fraction of those stars with planetary systems.
ne = The number of planets, per solar system, with an environment suitable for life.
fl = The fraction of suitable planets on which life actually appears.
fi = The fraction of life-bearing planets on which intelligent life emerges.
fc = The fraction of civilizations that develop a technology that releases detectable signs of their existence into space.
L = The length of time such civilizations release detectable signals into space.
So, these magnitudes that were indefinite in the past are now quite definite to an incredible degree of precision. For beginners, the understanding of the extent and measure of the cosmos has been enhanced dramatically. This is only being possible with the state of the art space and ground laboratories, that jackets the complete scale of the wavelengths, and can determine, how many galaxies are present within it and how many beyond.
The number this equation gives is quite huge. It can range from tens of thousands to hundreds of thousands. This big number signifies the probability of the existence of extraterrestrial intelligence the universe has ever had, over the past 13.8 billion years, the age of its existence. Certain things can overturn as well. The key ingredients of the very first start come augmented with the heavy elements and constituents that are necessary for life.
Though this equation predicts the existence of such a big number, we haven’t found even one alien species. Seeing this, there is a possibility that this equation might be wrong or we might be missing something. The Drake Equation: Could It Be Wrong?
Sara Seager, a Canadian-American astronomer developed a parallel version of the Drake equation to estimate the number of habitable planets in the galaxy. Instead of aliens with radio technology, Seager has revised the Drake equation to focus on simply the presence of any alien life detectable from Earth. The equation focuses on the search for planets with biosignature gases, gases produced by life that can accumulate in a planet atmosphere to levels that can be detected with remote space telescopes.
Seager’s Equation is
where: N = the number of planets with detectable signs of life
N* = the number of stars observed
FQ = the fraction of stars that are quiet
FHZ = the fraction of stars with rocky planets in the habitable zone
Fo = the fraction of those planets that can be observed
FL = the fraction that has life
FS = the fraction on which life produces a detectable signature gas
Seager’s equation predicts that there is a probability that we should at least detect 2 exoplanets with biosignatures.
All these predictions aside, if at all aliens are there, where are all of them? This is when the Fermi Paradox comes into the picture.
The Fermi Paradox
The observable universe is 90 billion years in diameter and there are at least 100 billion galaxies each with 100 to 1000 billion stars. With these huge numbers in place, there is nothing wrong in expecting the existence of extraterrestrial intelligence and there should be many of them out there. The Universe is as old as 13.8 billion years. We know that a technologically advanced civilization has existed on earth for the last 300 years only. There is an obvious possibility that some civilization would have started way before us and in that case, they had a lot more time to develop and become a super-powerful civilization. But if such civilization exists in the observable universe, we would have observed them by now. But we didn’t yet. Here comes the Fermi Paradox.
There are many possible explanations for the paradox:
The development of life is not as easy as we think: We don’t yet know how life has evolved on earth and it is a possibility that this process is pretty complex and is very rare especially in the case of intelligent life.
Intelligent life is there only on earth and nowhere else (this is pretty scary)
Intelligent life eventually destroys itself and it is its nature: If this is the case, then we might be getting closer to the end of human civilization.
The Universe kills intelligent life periodically: Probably, the universe kills life periodically by natural extinction events like a meteor shower. In this case, we might have a danger in the near future. To overcome this, we should start expanding our civilization into the cosmos.
Life has formed too far to observe: The universe is too big and is expanding and it is going very fast. So, life might have simply formed too far to observe or detect.
The aliens are too different from us: We hope that aliens also understand the radio signals we transmit but what if aliens have evolved differently. They might be existing in some other dimension and we can’t see them. The sky is the end for such imaginations.
The types of civilizations that can exist – Kardashev Scale
Nikolai Kardashev, a Russian astrophysicist gave the Kardashev civilization classification scale.This scale classifies civilizations depending on the basis of their energy harvesting and consuming capabilities.
On that basis, the civilizations are classified into three categories namely Type 1, Type 2 and Type 3 but Type 4 and Type 5 civilization can also be imagined.
Carl Sagan suggested a rough formula to rate the civilization on the basis of their energy consumption (Note: this formula is not a part of Kardashev theory). The formula is:
K = Rating of civilization
P = Power used by the civilization
Putting our energy use as P = 17.54 Tera Watt we get a rating as 0.7244 but according some researchers human civilization is not even at 0.7 and would take around 150 more years to reach Type-1 level.
So let us know about each type of civilization:
Type 1 Civilization: This civilization can use and store all the energy of its planet and is thus known as a planetary civilization
Type 2 Civilization: This civilization can control the energy of its solar system. They would be able to build megastructures like Dyson Spheres around there star and harness energy. They might also produce antimatter and harness energy from it. This type of civilization is known as Stellar civilization.
Type 3 civilization: This type of civilization can harness energy at the scale of its galaxy. Just imagine the amount of energy they could access. They can harness energy from neutron stars. They may also be able to tap energy released by supermassive black holes. This type of civilization is called a galactic civilization.
And below are some research papers and articles that you can read to get a much deeper understanding of things like the Kardashev scale and Dyson sphere:
Apart from these three types of civilizations, we can also imagine the existence of Type 4 civilization which might be operating at the scale of the universe.
The Search for Aliens
Now, after knowing about the odds of finding aliens, possibilities, fermi paradox, Kardashev scale, we also need to know a few things about the search for aliens. Researchers around the world are working day and night to find some clue of extraterrestrial intelligence. There are many non-profit organizations like SETI who are spending millions in this. So, let us move through some missions, programs and their findings related to extraterrestrial intelligence.
The Kepler space telescope was launched on March 7 2009. These space telescopes monitor the light coming from distant stars and a periodic drop in the light indicates the presence of a planet there. From the amount of light drop, we can estimate the properties of that planet. By, this we can estimate the distance of the planet from its star and predict whether life can exist there or not. Kepler has found close to 3000 exoplanets during its 9.5 years of spaceflight and there are many potential candidates in there.
One star has baffled the science community, known as the Tabby star or KIC 8462852. The Kepler data from this star was so weird that scientists started imagining that there was a Dyson Sphere built around this star and there was an extraterrestrial civilization around there. But astronomers now claim that that light block was due to dust and all.
Huge Radio Telescopes
Humans have built a lot of radio telescopes for detecting radio telescopes coming from the cosmos. We have been doing this in a hope to detect some signal from some civilization trying to contact from deep space. We have really big radio telescopes like China’s National Astronomical Observatories. These radio telescopes can detect extremely weak signals also.
There were a few mysterious signals we detected, like the famous ‘Wow signal‘. We never again received a similar signal, so researchers thought that it might be an alien signal. But recently the mystery of was solved
Researchers are trying very hard to find aliens by trying all the possible methods. We have gigantic radio telescopes, powerful space telescopes. There are many non-profit organisations like SETI which are spending millions of dollars on several exploration programs. But still, we don’t even have a single clue about any extraterrestrial civilization. Things again come back to the Fermi Paradox.
Let us hope that future missions like the James Webb space telescope give us at least a few signs of extraterrestrial intelligence.
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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