Sagittarius A* Image

You probably have already seen the fabulous image of the black hole in the center of our Milky Way galaxy, published on May 12th 2022. The Event Horizon telescope team achieved an unbelievable milestone in observational astronomy one again, the first one being the picture of the black hole at the center of galaxy M87. It is terrifying to think that in the center of our cosmic home lies a monster that might eventually devour everything around it. We have already looked at black holes in detail in another post, so instead it might be more insightful to focus on the imaging techniques used to take this fantastic picture.

The first image of Sagittarius A*. Credit: ETH collaboration.

What can we see in this image? The orange/red rings are the accretion disk around the black hole. It is impossible to “see” a black hole directly, as by definition not even light can escape its gravitational pull, hence astronomers rely on the stars and gas orbiting around it to show that there is a black hole. The image looks distorted not only due to the tremendous distance that separates us from the center of the galaxy, but also because the gas rotates around at a significant fraction of the speed of light. With such an immense gravitational pull, gravitational lensing becomes significant. In fact, because we look at the black hole from an angle, we also see the back side of the accretion disk and the event horizon. Light bends around the event horizon and falls back around it, creating a dizzying display of Einstein’s general relativity. Check our this Veritasium video for a more visual explanation. Looking at a black hole accretion disk is not the same as looking at the rings of Saturn.

Sagittarius A* is massive, with a diameter of 51.8 million kilometers, but it appears tiny to us because it is located 27,000 light years away. We are seeing it how it was back when the first ceramics were created by humans. In fact, the angular diameter is 51.8 micro arc-seconds, which is 1.4*10-8 degrees. How is it possible to produce an image of something so tiny? The equation for the angular resolution of a circular telescope is

Where D is the diameter of the telescope and lambda is the wavelength measured.

The smaller the value the better, as smaller objects can be resolved using the Rayleigh criterion. You might think that the easy solution is reducing the wavelength of light that is being measured. However, due to the tremendous amount of gas near the center of the galaxy, visible light wavelengths get almost completely absorbed. Hence, astronomers have to use radio waves as they can more easily get through the light-years of gas clouds. Another way to decrease the angular resolution is to increase the size of the telescope dish. Doing this with a single telescope would require a dish the size of the Earth, so instead the EHT collaboration uses multiple telescopes stationed around the globe to produce a similar effect. They use interference patterns of radio waves to sync up the images and make an effectively huge telescope our of many smaller ones.

The locations of the EHT telescopes around the world. For the Sagittarius A* image, 8 were used. This map outlines the importance of international collaboration in astronomy, as larger effective diameters of telescopes are needed. Credit: David James.

The amount of data generated was so huge that it took the team 5 years to process it, as the initial measurements were gathered over five nights in 2017. They had to manually transport the hard drives since it would be inefficient to transport it over the internet. They then used supercomputers to combine the images using a mathematical model that produces pictures consistent with laws of physics. This is another reason why the superimposed image looks distorted, but the team has made significant progress since the M87 black hole image in 2019.

The insane data processing that went into this image suggests once again the importance of programming and computer science skills for physicists. So much of current research relies on coding and understanding of processing power that computational physics should be one of the core topics covered in physics curricula.

What’s the big deal with this image? Before 2019 we only had indirect evidence of the existence of black holes, based on the movement of stars. However, now we are able to directly see the edges of the event horizon. The more data (images) we have, the stronger the hypothesis of supermassive black holes existing in centers of almost all big galaxies is. Furthermore, taking more pictures of Sagittarius A* may allow us to track how exactly the black hole consumes matter around it, which can teach astronomers more about its properties. It is definitely an exciting time for black hole research.


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Khadilkar, D. (2022, May 22). Snapping sagittarius A*: How scientists captured the first image of our galaxy’s Black Hole. RFI. Retrieved May 24, 2022, from

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Yazgin, E. (2022, May 20). Black Hole Sagittarius A* imaged for the first time. Cosmos. Retrieved May 24, 2022, from

Cosmological Constant

The cosmological constant went from being called Einstein’s biggest blunder to a fundamental field of research in contemporary physics. Nowadays, we think of it as a form of energy that opposes the pull of gravity and makes the expansion of the universe accelerate. However, the story of how it came to be like this is very interesting and also slightly mathematically unsettling. It is sure to be connected to the next great breakthrough in astrophysics as new observations are targeted at confirming its value and existence. It’s a rare comeback story in physics, which makes it even more exciting.

Measurements of supernova redshifts from 1997 that were used to show the accelerating expansion of the universe. Credit: ESO.

First, let’s go back to Einstein’s general relativity to explain how the constant originated. When Einstein first published the equations in 1915, they did not have the cosmological constant. These field equations are differential equations, so they are derived and solved using integrals. As with any indefinite integral, a constant C is added (or often forgotten by students), as the derivative of the constant is just 0. Einstein initially ignored a constant, as the predictions for the rate of change of the distribution of matter and energy in space remain valid no matter the constant. Nevertheless, in 1917 Einstein realized that his theory predicted an expanding and dynamic universe, where space changes with time. The scientific and philosophical consensus at the time was an eternal, unchanging universe, so Einstein introduced the cosmological constant Λ to make his equations static.

Einstein field equations with the cosmological constant Λ included.

However, very quickly the idea of a static universe collapsed, as I have talked about in this post on the expanding universe. In 1922, Alexander Friedmann showed that field equations were valid in a dynamic universe whatever Λ was. Furthermore, in the 1920s Hubble’s observations of redshift clearly showed that stars were moving away from us. In 1931, Einstein finally accepted his mistake and proposed a model of an expanding universe called Einstein-de Sitter space-time. Nobody expected that half a century later the cosmological constant was about to make a comeback.

In 1998, two independent teams lead by Saul Perimutter, Adam Riess and Brian Schmidt, showed that the expansion of the universe was accelerating. They measured the redshifts of supernova and found that their redshifts from one another was increasing at an accelerated rate. This implied a mysterious dark energy, which counteracts the pull of gravity, and a positive cosmological constant. Suddenly, we realised that Einstein was right after all, except in a strange reverse way. A cosmological constant exists, but it does not keep the universe static. It does just the opposite, pushing it apart at an increasing rate.

However, there is a big problem with the cosmological constant. We don’t know where it physically comes from. A theoretical idea is that a cosmological constant is equivalent to the vacuum energy of empty space, which arises from the creation of virtual particles. It is a constant quantum hum that persists in the emptiest regions of the universe. However, the force resulting from vacuum decay is 120 orders of magnitude greater than the measured cosmological constant! This is one of the most significant unsolved problems in physics and perhaps connecting the cosmological constant to quantum physics will require a unified theory. Without any theoretical explanation for the cosmological constant, it just appears like a neat mathematical trick for now. Or perhaps it is just an intristic property of the fabric of spacetime, but that would go against modern understanding of string and quantum loop theories.

The story doesn’t end here. The precise value of the cosmological constant is of tremendous importance for predicting the future and fate of the universe. When discussing dark energy, many scientist use the equation of state w. It is the ratio of pressure that dark energy puts on per unit volume. The equation is quite simple, with w being equal to the ideal gas constant R multiplied by temperature and divided by speed of light squared. If w = -1, the acceleration of the universe is constant and dark energy is the cosmological constant. If w < -1, which is called phantom dark energy, then the expansion is going to accelerate at such a rate that it will result in the big rip. For w > -1, the big crunch will occur as the dark energy will not be strong enough to counteract the pull of gravity.

The different scenarios for the end of the universe are based on the behavior of dark energy, If the strength of dark energy increases enough with time, we get a big rip caused by an ever-accelerating expansion. If the strength decreases, the gravitational attraction of objects within the universe eventually leads to a collapse. If dark energy is a cosmological constant, the universe continues expanding at a ‘mild ‘ constant accelerating rate and eventually ends in heat death. Credit: NASA.

The most precise measurement of the equation of state to date made by the Planck collaboration in 2018 put it at −1.028±0.032. This is close to the expected -1, however some physicists propose that dark energy is a scalar field so its value may differ in various regions of space. Ethan Siegel writes that the next decade, with advancements such the Vera C. Rubin observatory and the Euclid observatory we will be able to confirm if the cosmological constant is equivalent to dark energy, by increasing the accuracy of our measurement. Or perhaps we will find something totally surprising, like in 1998, which will shift our perspective on the cosmos.

As a sidenote, not all ends of the universe are directly connected with the value of w and dark energy. A very interesting apocalyptic scenario that I learned about in Katie Mack’s The End of Everything: (Astrophysically Speaking) is false vacuum decay. All physical systems tend to the most energetically stable equilibrium. The theory proposes that our universe is in a false equilibrium, like a valley in really tall mountains, but a more energetically stable value is still possible to reach, like a sea a few kilometers to the north. If by chance, in a process called bubble nucleation, a part of the universe would reach this more stable state, it would spread to the whole cosmos causing massive havok. And we wouldn’t see it coming because it would spread at the speed of light. It might even be happening somewhere far away right now…

The energy of the scalar field with a false and true vacuum. A transition to a true vacuum would be catastrophic for the universe, as the fundamental particles and constants might be changed. It would occur through quantum tunnelling. The probability of vacuum decay is a lot higher in the vicinity of black holes, yet this research is still recent and developing. Credit: Gary Scott Watson.


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The Discovery of Pulsars – Jocelyn Bell Burnell

Pulsars are powerful cosmic lighthouses. They are swiftly rotating magnetized neutron stars that emit high-energy electromagnetic radiation. They are a particularly useful tool for astronomers since they can be used to probe the space between galaxies and even act like precise clocks. Due to their regularity, they are used in maps of the cosmos, hence the relative position of the Sun to pulsars was etched on the Voyager golden record. Yet for me, the discovery of pulsars is the most fascinating. It is a story of passion, perserverance, and ingenuity that is very inspiring to future researchers.

A visualization of a pulsar emitting high-energy cosmic rays from its magnetic poles. Credit: NASA

Jocelyn Bell Burnell was born in 1943 in Northern Ireland. Her dad was an architect who designed the Armagh Planetarium. Through her visits there with her father and by reading books, she became interested in astrophysics as a child. Her education was difficult due to the social norms for women. She went to a prestigious grammar school, yet only boys were encouraged to study technical fields. Her parents had to convince the school to change its policy in order for Burnell to study science. She eventually graduated with a BS from the University of Glasgow and went on to pursue a Ph.D. at Cambridge, which she completed in 1969.

A picture of Jocelyn Bell Burnell during her graduate studies in 1967. Credit: Roger W Haworth.

Her graduate work coincided with a boom in radio telescopes. Alongside Anthony Hewish, she worked on constructing the Interplanetary Scintillation Array. Scintillaton is random fluctuation in the intensity of the radio waves emmited by objects from space. It is mainly caused by changing refractive properties of the solar wind. Think of an analog with visible light. From high school physics we know that water refracts light because it is denser than air, so light travels more slowly through it. Now imagine a mixture of water and oil that we stir vigorously. If we shine a beam of light through it, some of the light will hit larger oil droplets and some will just pass through the water. The uneven diffraction will cause intereference between different beams and thus irregularities in the amplitude. The solar wind plasma is a mix of electrons and protons that varies in density, so it acts like the water and oil mixture but for radio waves.

The main goals of constructing this array were investigating scintillation in more depth and looking for quasars, which are massive, and luminous active galactic nuclei powered by huge black holes. Burnell spent her research reviewing massive printouts from the instruments, looking for interesting details. In November 1967, when analysing signals from that summer, she found an anomaly. It appeared that a signal repeated itself every 1.33 seconds with imense regularity. It couldn’t be a coincidence and random scintillations could not explain it. The source was jokingly dubbed LGM-1 for Little Green Man, as some publications pondered if the regularity could come from alien communications. Burnell described her discovery as a pulsating radio source, which was shortened to pulsar by a BBC correspondent.

The chart of the pulsar was published in the Cambridge Encyclopedia of Astronomy. Peter Saville used it when designing the cover of the iconic 1979 Joy Division album Unknown Pleasures. Credit: Patrick Weltevrede.

Yet, despite her brilliant discovery the prejudice of society towards women still deeply affected her. In a 2020 Harvard lecture she disclosed, that when the research team was discussing their discovery Hewish would be asked about the physics, while Burnell would be asked about the color of her hair and how many boyfriends she had. Moreover, she did not receive the 1974 Nobel Prize, despite building the Interplanetary Scintillation Array for two years, pursuading Hewish that this regular phenomenon was not just interference, and meticulously going over 30 meters of paper per night. Of course, her male supervisor received the award and was invited to speak in conferences across the globe.

Despite the injustice she faced in the academic world, she has been undeterred. She taught at a lot of universities, even acting as the president of the Royal Astronomical Society, and currently is a professor at Oxford. In 2018, she was awarded $3 million and the Breakthough Prize in Fundamental Physics. She spent the money on funding Ph.D. studies for physics students from underpriviledged backgrounds. Burnell often speaks about supervisors getting more credit than the students that carry out the experiment. Many of the greaterst discoveries in physics were actually made by graduate students. For instance, the Rutherfold gold foil experiment that showed that a nucleus is a dense positive charge, was actually carried out by his grad students Geiger and Marsden. While Hewish laid out the basics of scintillations in the 50s, it was Burnell who actually applied them. For anyone who has done independent experimentation in physics, you know how challenging and unexpected some of the things we have to deal with are. I strongly hope that more and more professors will give credit to their graduate students in their papers and during conferences.

A portrait of Jocelyn Bell Burnell that occupies the top of the grand staircase in the Royal Society building. In the past few years, academia has began giving more credit to women who contributed greatly to science. Credit: Stephen Shankand.

I would like to finish this post with a personal update. I have been accepted to JHU, my dream school :). I’m planning to major in physics and I am very excited to write about research or interesting things I learn in classes. I will have a lot of free time soon, so I’m definitely going to review more books and maybe even new articles I find on arXiv. Thanks to everyone for supporting me on my high school journey!


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Cofield, C. (2016, April 22). What Are Pulsars? Space.Com.

Drake, N. (2021, May 4). Meet the Woman Who Found the Most Useful Stars in the Universe. Science.

HEWISH, A., SCOTT, P. F., & WILLS, D. (1964). Interplanetary Scintillation of Small Diameter Radio Sources. Nature, 203(4951), 1214–1217.

Wikipedia contributors. (2022, February 11). Jocelyn Bell Burnell. Wikipedia.

Helgoland by Carlo Rovelli

In the summer of 1925, Werner Heisenberg outlined the theory of quantum mechanics on the tiny German island of Helgoland. In his newest book, Carlo Rovelli poetically intertwines the story of the origin of quantum theory with its interpretation and philosophical consequences. It is his best work yet and includes a very lucid presentation of relational quantum mechanics. In this post, I want to go over some of the most interesting things the author touches upon. However, I highly recommend picking up this short and sweet work to grasp all the details for yourself.

The Helgoland island. Credit: Pegasus2 through Wikipedia Commons.

In the first few parts of the book, the author outlines the initial debate between the boys’ physics of Jordan, Heisenberg, Pauli, and the wave theory of Schrodinger. The inspiration behind Heisenberg’s insight was attempting to figure out equations that predict the intensity of the light emitted when an electron becomes deexcited in an atom and falls down an energy level. Guided by Max Born and Niels Bohr, he decided to focus on only what is observable without mudding up his theory with previous ideas. In this way, he came up with the idea that if physical variables representing the electron get replaced with matrices, the equations predict exactly what experimental evidence shows. Paul Dirac also came up with a similar idea at that time, called non-commutative algebra. The idea was that order of physical variables matters, and position multiplied by momentum is not the same as momentum multiplied by position.

In 1926, Schrodinger managed to come up with his famous equation when spending some time in the mountains with his lover. There is a common theme of isolation and solitude that allows one to access the depths of nature here, which is quite poetic and reminds one of the famous Caspar David Friedrich’s painting Wanderer above the Sea of Fog. The key distinction of Schrodinger was that the ‘invisible’ wave function determines the probability of a particle’s position and pilots it through a hidden deterministic mechanism. On the other hand, Heisenberg and Bohr thought that quantum physics was strictly indeterministic and “God does not play dice”. This clash of ideas launched a century-long debate on the interpretations of fundamental quantum mechanics, which crosses the boundaries of philosophy, physics, literature, and art.

Wanderer above the Sea of Fog. The painting is from around 1818. Image credit: Cybershot800i through Wikipedia Commons.

Then Rovelli outlines the main interpretations that have emerged since the 1920s. He critiques the many-worlds, hidden variable, and physical collapse theory on the basis of not being observable. He then discusses QBism or quantum Beyanism, which states that a human observer feels like quantum mechanics is not deterministic because she cannot see the whole picture. Rovelli is quite biased against these theories, especially with quickly dismissing physical collapse. This serves as the ground for presenting his relational interpretation, which he came up with in the 90s to explain entanglement.

Relational quantum mechanics builds upon special relativity in that each quantum state is observer dependent and two different observes can give two accurate descriptions of a quantum system. For instance, he states that entanglement is a dance for three and not a dance for two, meaning that the observer has a clear role in impacting quantum phenomena. However, he clearly solves some of the problems of the Copenhagen interpretation, which vaguely states that wave function collapse occurs when a macroscopic object is used to measure microscopic phenomena. Rovelli argues that particles that are in relation with other particles impact quantum mechanics and the wave function and that the universe is an interconnected web of relations. This is a very elegant theory that draws from logical positivism and the ideas of Ernst Mach, who inspired both Einstein and Heisenberg. It focuses only on what is observed, without trying to explain these phenomena with metaphysical invisible phenomena.

The author then transitions to connecting his theory with the Buddhist ideas of Nagarjuna who wrote that things do not exist, but only relations make up the world we know. This very beautiful connection between physics, literature and art is later continued when Rovelli discusses the easy and hard problems of consciousness, stating that there is no distinction between the mind and the body other than a different set of relations.

A Japanese painting of Nagarjuna from the artwork The Eight Patriarchs of Shingon from the 13-14th century. Credit: National Museum, Japan.

Overall, this book is a great introduction to interpretations of quantum mechanics. Even though, it does not offer textbook explanations and categorizations of each opposing viewpoint, Rovelli goes through the thinking process of physicists and philosophers who grapple with these ideas. The connections made with Shakespeare, Greek philosophers, Nagarjuna and personal anegdotes from Rovelli’s life make up a particularily entertaining read. It’s my favourite book of his yet and I am very excited for more. On a side note, it might seem that a few recent posts are slightly tangential to astrophysics. Personally, I am attempting to explore multiple areas of physics before I get to university, so that I am more well versed with terminology and interdisciplinary research. However, I think soon we will return to pure astrophysics. I especially want to make a few posts about the succesful (so far!) launch of James Webb and what it means for science.


Laudisa, F., & Rovelli, C. (2019, October 8). Relational Quantum Mechanics. Stanford Encyclopedia of Philosophy.

Lopez, D. S. (2017). Nagarjuna | Biography, Philosophy, & Works. Encyclopedia Britannica.

Rovelli, C., Segre, E., & Carnell, S. (2021). Helgoland: Making Sense of the Quantum Revolution. Riverhead Books.

Analog Computers and Tides

In the 19th century, scientists were keen to solve the problem of predicting tides. Ships needed to know when to go to the port without running aground, and fishermen wanted to know when to catch fish. Variations in water level were measured using a mechanical device that plotted the height of the sea on graph paper. However, nobody knew how to use this data to predict tides and understand what exactly causes them. The story of tide prediction is absolutely fascinating and it led to a breakthrough in computing. It also features a young Lord Kelvin, right after the worked on laying the transatlantic telegraph cable when he developed a fascination for the sea. It is important to learn about analog computing since soon we might need to return to it in a more sophisticated form, in order to face the most difficult contemporary computing problems.

An image of a receding tide. Credit: SurferToday.

Since Newton, scientists knew that tides are caused by the gravitational tug of astronomical objects, such as the Moon and the Sun. In the 1770s, Laplace developed a system of partial differential equations that approximated tides based on the variations in the gravitational pull. Nevertheless, they were still a very rough approximation and it took until the 1860s to develop an ingenious way of predicting them.

A water level graph from Newport, RI in 2009. Credit: NOAA.

Tides come in cycles, so their pattern is a combination of sine and cosine functions. In order to decompose a complicated function, a Fourier transform developed in the early 19th century, could be used. William Thomson, later known as Lord Kelvin, decided to apply the Fourier transform to tidal waves. It was known that certain tidal patterns match up with the cycles in gravitational pull of the Sun and the Moon, but just how strong the impact each factor had, was up to debate. In order to find out, Thomson had to do tons of complicated multiplication and integration, therefore he decided to automate the process.

A mechanism for generating sinusoidal motion using circular motion. Credit: E. G. Fischer.

He knew that there was a mechanism used to convert circular motion to a sinusoidal graph. If he tuned a sufficient amount of these machines to the amplitude and frequency of each of the component functions, he could recreate the original function. Hence, this could be done in the opposite way and future tides could be predicted. He combined a few of these mechanisms together and with some clever calibration, one of the most successful analog computers of all time.

The 10 component tide predicting machine developed by Kelvin in the years 1872-1873. It is on display in the Science Museum in London. Credit: William M. Connolley.

Predicting tides not only proved useful for the fishing and transport industry, but it also helped beat the Nazis in WW2. Knowing when the tide would come on D-Day was crucial in order to avoid German defences on the beaches and allow the ships with soldiers to retreat. Analog tide prediction machines were in use till the 1960s and 1970s, until more powerful digital computers took over. The advantage of analog is that it allows for a continuous input and output rather than a string of 1s and 0s. However, since they are a mechanical system with continuous variables, tiny manufacturing uncertainty can completely invalidate the result. In digital machines an output of 0.95 is still classified as a 1, so manufacturers can be more lenient with precision.

What does this have to do with astrophysics? Computation is closely linked with modern research, as this is a field were direct observation is often difficult and simulations are required. Perhaps there are some future uses were analog machines in astronomy. More importantly, this is a story about understanding a physical phenomenon that has cosmic origins. It is another chapter in the story of using technology to decipher the universe and its impact on our daily life, in this case through gravitational fields. A lot of credit goes to Derek Muller at Veritasium for making a video about this topic. Its something I never even thought about and it sparked an ‘aha’ moment that made me write this post. Happy Holidays!


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The James Webb Space Telescope

The replacement to the Hubble space telescope is planned to launch on December 18th. With production beginning all the way back in 2004, it cost a staggering $9.66 billion dollars to manufacture, including operational costs. It is an infrared telescope, which will allow us to see galaxies 100 million years after the Big Bang or 13.6 billion years ago, compared with Hubble’s 13.5 billion. It will be orbiting the Sun at the Lagrange point 2, a million miles away from Earth. Its main task is examining the atmospheres of exoplanets. It will be able to send back the first images around 6 months after launch with a resolution 100 times better than the Hubble. Let’s look at some interesting details and explain how it works.

The fully constructed James Webb telescope, which is the largest and most complex humanity has ever built. Notice the honeycomb structure of the antenna panels. Credit: NASA.

The James Webb telescope operates like a reflector, with a larger mirror that captures infrared light and sends it to a smaller mirror which then reflects it onto a sensitive detector. If you want to find out more, check out the post on telescopes. The telescope uses infrared light, which can be manifested as heat. Therefore, on one side it is heavily shielded from the Sun, in order to limit interference. On the Sun facing side, there is also the computer and devices used to communicate with Earth. On the other side, the instruments and mirrors are kept cold at -233°C, to ensure optimal working conditions.

What is the Lagrange point 2? In the 18th century Lagrange found five solutions to the three body problem, which are stable orbits where the objects stay in the same position relative to each other. This will allow it to keep in constant communication with the Earth. This position is held by the gravitational fields of the Earth and the Sun, which means little rocket power will be needed for adjustments. However, it will not just sit stationary in L2, it will orbit around the point with a period of 6 months. This keeps it out of Earth’s and Moon’s shadow, which will allow continuous operation as the Hubble gets in shadow every 90 minutes. This will allow for longer exposure times. Take a look at this video if you want to see a simulation of the orbit. It is not the first object to be put in L2, as the WMAP and Planck satellites have been there before. It will take around 30 days to reach that point.

The five Earth-Sun Lagrange points. Credit: NASA.

There has been a great deal controversy around its name. James Webb was a NASA administrator that oversaw the Apollo program. Nevertheless, this was also the era of the Lavender Scare, when LGBTQ employees were hunted down and forced to quit. While, Webb’s name does not appear in many documents, David K. Johnson who wrote a 2004 book on the Lavender Scare claims that he helped establish the “modus operandi” of the Hoey Committee when he was acting as undersecretary. In March 2021, four astronomers wrote an article in the Scientific American and created a petition which gathered 1700 signatures from other experts in the field. This pushed NASA to launch an investigation into the name in July, nonetheless the result of it was keeping the name. Another proposed name was the Harriet Tubman telescope. Tubman was an abolitionist who escaped slavery and then made 13 brave return missions to rescue 70 more enslaved people. According to Chanda Prescod-Weinstein, she “represents the best of humanity, and we should be sending the best of what we have to offer into the sky”. I think it is a fantastic idea, if we are not naming it after a scientist in the first place. Names can be changed, so hopefully NASA will go back on its decision in a few years with more pressure from the scientific community.


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Telescopes have been the most significant observational tool in astronomy since its invention by the Dutchman Hans Lippershey in 1608. It played a significant role in Galileo’s observation of the phases of Venus, Jupiter’s moons and craters on the Moon. Nowadays, we have the Hubble Space Telescope, and later in 2021 we will send the James Webb Telescope. They allow us to see the deepest corners of the universe. But how do they work?

Galileo (1564-1642) observing the night sky with one of his telescopes. Credit: Hulton Archive.

The basic working principle of a telescope is magnifying an image, thus making it larger than it would normally be to the eye. The most basic type of telescope is the refractor, invented in 1608. It is made out of three main components, a long tube, a convex objective lens and a concave eyepiece. Light falls into the objective lens, which focuses it down on the back of the tube. The eyepiece magnifies the image and brings it to the eye.

A simple refractor with a convex objective lens and a concave eyepiece. Credit: OpenStax College.

Nonetheless, a better way telescopes use is implementing mirrors to magnify images. These are called reflectors and were created by Newton around 1680. They use a large curved concave mirrors to capture the light and reflect it to a smaller mirror, which then reflects the light into the observer’s eye. The first mirror flips the image, but this is fixed as the second mirror flips it into the correct orientation again. Large mirrors that do not distort images are easier to manufacture, therefore this is the way that many telescopes operate.

A simple reflector. Credit: Academy Artworks.

In the 20th century, there were massive breakthroughs in telescope technology. One example are radio telescopes developed in the 1930s and infrared telescopes developed in the 60s. As you can tell by the name, we do not have to observe the universe using only the visible parts of the electromagnetic spectrum. In fact, many of the distant objects are only observable using infrared light.

Radio telescopes are immense antennas and radio receivers. They have to be so huge, as signals from far away objects are very faint. This is why they are also located in remote and often stunning areas far away from major cities, to avoid radio interference. The biggest radio telescope is located in Guinzhou province in China and the dish diameter spans 500m.

The Five-hundred-meter Aperture Spherical radio Telescope. Credit: Absolute Cosmos

The second prominent type of telescope is the infrared telescope. All objects in the universe with a temperature above absolute zero emit radiation and an infrared telescope can detect radiation that is too faint to be seen with visible light. This is a breakthrough in the search for planets and brown dwarfs. Furthermore, due to the longer wavelength of infrared radiation, it is less impacted by scattering in clouds of intergalactic dust, which allows us to see objects like the center of our galaxy. These telescopes need to be situated at high altitude, as Earth’s atmosphere absorbs a lot of infrared radiation. Therefore, they are often put on mountains, in planes and most effectively in space. The successor of the Hubble as NASA’s flagship observational project, the James Webb Space Telescope is an example of an infrared telescope.

With all types of telescopes, there are similarities in terms of what affects the quality of the image. For visible light telescopes, the most obvious limitation is a cloudy sky. Overall, the atmosphere creates all types of distortions, therefore it is crucial to have telescope up in space for the greatest image quality. Therefore, we should be very excited for the James Webb telescope replacing the now 30 year old Hubble. The name isn’t as catchy, but it might significantly change the paradigm in observational astrophysics.


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Smith, B. (2019, March 2). Things Found in the Exosphere. Sciencing.

Telescopes | Physics. (n.d.). LumenPhysics.

Solaris – Book and Movie Review

Solaris is a science fiction book, written by Polish author Stanisław Lem in 1961. It’s a scary and powerful depiction of the limits of human rationality. While, I don’t usually review fictional texts here, this book is fantastic and I just have to share it. In a way it is like Frank Herbert’s Dune, as it is incredibly multidimensional dressing a variety of themes. I’ve recently watched the Soviet film adaptation, and I couldn’t help myself to not write about it, so here we are. I don’t have a specific category for movies on the blog, at least not yet, so I decided to attach my impressions of the 1972 Tarkovsky film here too.

Stanisław Lem (1921-2006) was a Polish science fiction author and essayist. He was one of the most prolific writers in the genre of hard science fiction in the country. His other famous works include The Cyberiad, Eden and The Invincible. His work is difficult to translate due to the many neologisms. Credit: Alamy.

Let’s begin chronologically with the book. The story follows the journey of Kris, a doctor of psychology also known as Kelvin, who is tasked to evaluate the wellbeing and research purpose of the men working on the Solaris station. He arrives at the planet and finds only 3 people there, where one of them called Gibarian committed suicide a few days before. He finds Snaut and Sartorius in mental disarray, paranoid and not wanting to talk. He feels something strange is happening, but the real horror begins when he wakes up the next day. In the room stands his wife, who committed suicide 10 years ago. She is referred to as a guest, both Snaut and Sartorius also are visited by such creatures. Yet, they are not monsters but almost completely human. As we later find out, they are composed of neutrinos stabilised by the gravitational field of Solaris (don’t ask). They are self aware, but need to be constantly in the presence of their “host”, else they lash out with violence and terrible screams. They also can regenerate wounds and resurrect from drinking liquid oxygen.

The pinnacle of the story story, in my opinion, is when Kris explores the library. There we get a detailed overview about the past study of Solaris and Berton’s mission. The planet Solaris has been studied for decades and was once at the pinnacle of funding and interest. Nevertheless, the planet proved extremely difficult to comprehend, and now it is a playing field for unfalsifiable hypotheses. As a last resort, the researchers used strong radiation on the ocean, which caused the planet to respond, by acting as a mirror for the human psyche. It spawned these guests, which are products of the researcher’s subconscious mind. It puts into question the limits of human knowledge. The different approaches, efforts of brilliant scientists and creative theories all turned out to be fruitless. It makes one wonder if it is worth studying things that we will never understand; should we give up or continue like Sisyphus?

Lem hated both movie interpretations (there was another one in 2002 directed by Steven Soderbergh), as he thought that they misrepresented the main theme of his work, and I couldn’t agree more. The Tarkovsky film focuses more on beautiful visuals and symbolism, rather than the profound philosophical insights of the author. This misrepresentation by all means does not make it a bad movie, and here is why.

A frame from the movie Solaris, when Kris is standing on the field next to his family home. Credit: Andrei Tarkovsky.

The 1972 film has been called a Soviet response to 2001: Space Odyssey, but that is an awful oversimplification. The film plays an entirely different cultural role. It emphasises the theme of love and identity through phenomenal lighting. Harey’s selfless The small budget made for some interesting artistic choices, such as using very long shots of Japanese tunnels and highways to portray a retro-futuristic city. To be honest, it works better than today’s CGI and fits perfectly with the theme.

Tarkovsky exemplifies Harey’s dilemma. Kris grows to love her, as he regrets having an argument with his wife these 10 years ago. Nevertheless, as time goes by she becomes more and more self aware, and doubts his love and her real existence. She knows she is not that Harey, but someone completely else. The story is about contact, contact wit the pseudo-consciousness of the planet and Kris’ lost love. It’s a beautiful parallel between romantic love and the innate thirst for knowledge.

Solaris is a thought provoking text and film, especially in the context of astrophysics. We spend a lot of brain power and money on the study of black holes, the Big Bang, dark matter and dark energy. Yet, the energies required to verify string theory or perhaps some aspects of dark matter may never be achievable, and we might reach a point of unfalsifiable theories. A pessimist might already notice that the study of quantum gravity, since the early 2000s, has reached relative stagnation and we might have to wait for a long time for a resolution of the string theory vs. loop quantum gravity debate. Nonetheless, we have reached such periods before with quarks, the Higgs boson and other fundamental particles. Science keeps surprising us in terms of just how much we are able to discern from our tiny vantage point on Earth. But the limitations of science are still worth thinking about.

A frame from the 1972 film, featuring Kris and Harey. Credit: Andrei Tarkovsky.


Diana @ Thoughts on Papyrus. (2019, July 24). Review: Solaris by Stanisław Lem. Thoughts on Papyrus.

Lem Vs. Tarkovsky: The Fight Over ‘Solaris.’ (2020, June 16). Culture.Pl.

Lopate, P. (2011). Solaris: Inner Space. The Criterion Collection.

Shave, N. (2020, May 1). I’ve never seen . . . Solaris. The Guardian.

The Order of Time by Carlo Rovelli

Time is more than just an emotionless variable. It gives rise to the fear of death, memory and the flow of the universe. Carlo Rovelli depicts time from this human perspective in his 2017 book.

The Italian physicist is one of the founders of quantum loop gravity and a bestselling author. He is interested in Ancient Greek culture and currently teaches at the Aix-Marseille University.

We commonly view time as something absolute and uniform across the universe. The author shows that time is much more flexible and dependent on other variables in reality. Time passes differently depending on the speed of the observer or the strength of the gravitational field. This is Einstein’s brilliant idea of relativity. Time passes faster the further away you are from the source of a gravitational field. Thus, clocks move a tiny bit faster in the mountains relative to sea level. This was experimentally verified by flying an atomic clock in an airplane. In short, time is just perspective.

But it gets even stranger. The idea of past and future is determined only by entropy. Time flows from low to high entropy, as things tend to get more disordered. However, Rovelli states that entropy is not an objective quantity. Imagine a standard deck of cards, with half of the cards marked red and half marked black. Let’s arrange them so that the first half of the deck is all red cards, and the second half of the deck is black cards. If we shuffle them, you might say that they are less ordered. However, that is only because we assumed that this half red half black configuration is what we consider order. Perhaps, the shuffled cards are now in a particular state that another person considers ordered. Therefore, entropy also depends solely on perspective.

This doesn’t mean that I can see a different entropy than you. Simply, the state of the universe that we observe manifests this particular entropy that we can use to differentiate past from the future. But this is not absolute, and the author proposes that we feel the flow of time only because of our unique vantage point. Throughout the book, the familiar concept of time completely crumbles.

The Order of Time is a great read for anyone interested in physics. The author sprinkles in bits from Greek poetry and Proust, in order to contrast our intuition with our equations. He shows that time is beautiful and fundamental to the human experience, since we are formed from memories. I really recommend this book although, you might get disappointed if you are looking for a lot of equations and diagrams.

Private Space Exploration

The emergence of private space companies began in the early 2000s: Space X was established in 2002 and Blue Origin in 2000. Currently, the three major players are Virgin Galactic, Blue Origin, and Space X. Their goals are to make space more accessible for people not formally trained as astronauts. Space X is making other technological leaps with the StarLink wifi satellite system and their reusable rocket boosters. Recently, they have been focused on planning the trip to Mars by developing Starship: the tallest rocket ever. 

Space X Starship. This monster is 120m tall and weighs 5000t. It is designed to carry passengers and cargo to the Moon or Mars.

The main motivation of these companies is profit and passion. They are all run by billionaires who made their fortunes in other companies. They want to become the first to reach the goals of commercialising spaceflight, in order to have a firm grip on the industry when it ‘takes off’. They have enough capital to be able to cover the early failures of R&D, which is why they are able to outclass small competitors and even public agencies like NASA. They receive funding through investments and fulfilling contracts. Space X mainly makes money by launching satellites to space, through the rideshare program.

These companies will definitely be profitable in the future, it’s just a matter of how many years it will take. Space X is definitely the closest to that goal due to its stellar R&D, contracts with NASA, and work with the ISS on the Dragon 2 Capsule. Virgin Galactic also secured a ton of money from space rides already being booked by influential people. All these companies heavily rely on social media for marketing. Richard Branson even flew on his craft a few weeks ago, which was heavily discussed online.

Virgin Galactic’s SpaceShipTwo. It will be carried by a plane to an altitude of about 15,000 meters and then the rocket boosters will propel it to space. It will cost $250,000 for a seat.

There are many legal concerns with commercializing space. Countries and companies cannot own parts of the Moon or other planets, but the smell of profits from mining could result in abolishing these laws. Potential collisions in orbit or technical difficulties with expensive payloads on board would require the development of a sound insurance system. Who will control certain regions of the orbit, once the volume of commercial flights increases? Can space be used for criminal means?

Let’s hope that the rise of these private companies will only result in bringing space closer to everyday people, solving climate change, and developing new technologies. Getting a perspective on our pale blue dot from space could have a great impact on the polluting activities of very influential people.


Gohd, C. (2021). Elon Musk is thrilled as Space X’s Starship becomes world’s tallest rocket – and he’s not alone.

Monica Grady. (2020, November 20). Private companies are launching a new space race – here’s what to expect. The Conversation.

Neuman, S. (2021, May 2). 4 astronauts splash down in SpaceX Dragon capsule after 6 months in orbit. NPR.

Wattles, J. (2021, June 30). SpaceX launches 88 satellites in Rideshare mission. CNN.