Light is a weird thing. It is both a particle and a wave, yet it has no mass to it. This means it should be immune to certain laws of physics, such as gravity, since gravity requires two masses to generate a force. However, light does bend due to gravity. This is not the normal attraction, but rather the bending of the fabric of space itself. This curvature of space due to the presence of a massive object bends light towards the center of the massive object. The heavier the mass is, the more the light curves.
During total eclipses of the sun, the light of the sun is blocked out for a while, allowing one to observe the sky with the stars and planets during the day. One interesting phenomenon was that some bodies were spotted during this time and became visible to Earth, even if they were located directly behind the Sun.
Visualization of the bending of the light towards the sun, credit to Discover Magazine
This visual proof shows how the mass of objects bend light. With more massive objects, the larger the curve.
Newton, Kepler, Galileo, Copernicus… Eratosthenes?? The name Eratosthenes is not as universally renowned, or even as known, as the likes of Newton or Galileo.; however, his contributions are just as exceptional. More than 2200 years ago, around 240 B.C.E, Eratosthenes correctly measured the circumference of the Earth to within 5% of its correct value. Considering the rudimentary tools and relatively minimal preexisting knowledge that he had to work with, this feat is one of the most impressive in the history of astronomy. Furthermore, Eratosthenes made his remarkable calculation using only relatively basic geometry and astronomical knowledge. Eratosthenes knew that during the summer solstice, the city of Syene observe the Sun at the zenith (altitude = 90 degrees). On the same summer solstice, Eratosthenes measured the sun to be at an altitude of 83 degrees in his home of Alexandria. Because the Sun is at a great distance from Earth, the Sun’s rays that hit Alexandria and Syene are virtually parallel, and so Eratosthenes concluded that Alexandria was separated from Syene by 7 degrees of latitude. Eratosthenes knew that the north-south distance from Syene to Alexandria was approximately 5000 stadia (or 833 km), and so he calculated that 7 degrees of arc subtends 5000 stadia north-south. Eratosthenes measurements led to his conclusion that Earth was approximately 250,000 stadia or 42,000 km in circumference. In the 21st century, humans use satellites to measure Earth’s circumference. This method yields an (average) circumference of close to 40,000 km, just 2,000 km different from the value that a single person with a wooden stick calculated more than 2,000 years prior.
Hypatia is considered the first female astronomer and mathematician (of whom we have records) of the world. She lived in Alexandria in the 4th century AD, where she studied and taught philosophy and astronomy at the Neoplatonic school of Alexandria. Her father, Theon of Alexandria, was a prominent mathematician and some consider him the last member of the Library of Alexandria. The two of them worked together to edit Ptolemy’s Almagest, a mathematical and astronomical text covering the motions of the planets and stars using a geocentric model. She is also known to have built astrolabes, astronomical instruments used to calculate astronomical positions. Later in her life, she advised Orestes, a Roman state official who was feuding with Cyril, the Christian bishop of Alexandria. As a result of this conflict, a mob of Christians brutally murdered Hypatia. Some historians believe that the destruction of the Library of Alexandria, an archive of history and research, coincided with her death.
In the television show Avatar: The Last Airbender, the main character is able to commune with one of his past lives on the Winter Solstice. This happens when the sun shines through the wall and directly hits a statue of the past life that he is trying to talk to. The catch in the show is that the sun only shines on the statue once a year, during the Winter Solstice.
As seen above, the Sun perfectly aligns itself with the arches of Stonehenge during the Summer Solstice. This is just one of many real-world examples of cultures building monuments around solar events, just like they did in Avatar. The Scottish were far from the only culture to find a way to commemorate the Winter Solstice; in fact, it has significance in almost every single culture.
This Irish tomb allows light in for a few minutes on the Winter Solstice. This tomb was thought to have accompanied celebrations of life as they saw the solstice as the death and then rebirth of the sun.
Spectroscopy is the information that comes from a spectrum. The spectra of an object tell us the electrical electromagnetic radiation, the chemical composition, and the wavelength of an object. Each type of molecule and atom will react to the electromagnetic radiation in a different way. One type of spectroscopy, absorption spectroscopy , the light is absorbed by molecules and changes energy states A detector records the depth and the absorption of wavelengths. This is known as a absorption spectrum.
The topic of light in regards to astronomy or any study of space is incredibly fascinating. In a vacuum, the speed of light travels around 300,000 km/sec and is known to be the fastest phenomenon in the entire universe. There’s so many interesting aspects that come out of studying light. One such example would be that the closer an object moves to the speed of light, the slower time becomes for that object. It is even believed that if we were to create a vessel that travels faster than the speed of light, time travel would be possible. Now as crazy and captivating as that sounds, it is not even the most interesting thing about it. In fact, in a far more practical sense, we as humans can experience “time travel” every day in everything we see. If you are ever to stare out into the night sky, you are looking at the stars, moon, sun, and planets in the past as takes time for light to reach us. Yes, even despite how quickly light moves, there is still calculable times that it can take light to reach us from a certain distance. And this is where the idea of looking into the past comes into play. When we stare at the sun for example, there is roughly an 8-minute time gap for the sun’s light to reach us. Essentially what is occurring is us seeing the sun 8 minutes in the past. Even when we look at the moon, there is roughly a one-minute gap until its light reaches our eyes. The thought of peering out at something and only ever seeing it as it once existed moments, minutes, hours, or years ago in the case of other stars in the galaxy, is simply so enthralling. Moreover, even when you look at your friends in person, you are only seeing them in the past as it still takes time for the light from them to reach your eyes. If you stare at your feet you are still viewing it from the past. Of course due to its immense speed to the time buffer is unnoticeable and infinitesimally small, but the concept still remains true. Anything we ever see is still technically a past version of it, which is why I think this aspect of studying light is the most interesting and remarkable of them all.
If the Sun were to disappear, how long would it take for us to notice? This question usually brings about an answer of ‘8 minutes’, or about the time that it takes light from the Sun to reach Earth. However, Earth is orbiting the Sun, and if it were to instantaneously disappear, would Earth still orbit the space that was occupied by the Sun? This question, along with many other mysteries of the universe, was answered by Albert Einstein. To confirm Einstein’s theories, satellites such as the Gravity Probe A and B were launched into space in 1976 and 2004, respectively.
‘The speed of gravity’ refers to the speed at which warped space will conform to its non-warped state, and it is equal to the speed of light (about 3.0 x 108m/s). If the Sun were to instantly disappear, Earth would orbit the space for about 8 minutes, the same time it takes light to reach Earth. Einstein had come to this solution by theorizing the concept of space-time, or a fabric in which space and time are linked — different from Newton’s theories of separating space and time.
Water tides are a very interesting topic, yet most people think very shallow about them. Previously, all I knew or cared about tides was whether it was safe to go in the water. After a little research, I learned how important they are in terms of climate change. Humans recently have been dramatically altering the tides by burning lots of fossil fuels. This is causing the water to come much much higher up the coasts. This might seem like a small deal, and would just reduce the size of beaches, but in reality it puts many places at risk to seriously flood. This is a problem because the gravitational pull from moon to earth does not change rapidly in the slightest, but what is changing is the way the waters are effected. This is also evident in very shallow waters around the world, some waters can change so drastically that one day a ton of land emerges, and the next it is gone. Scientists are now accounting for these drastic changes, and studying the new tidal habits of water to better plan for these drastic changes.
When many people think about the Hubble Telescope, they tend to think of some of the most spectacular photos that it has captured over its five missions (with an example displayed in Figure 2). However, some people may fail to recognize the importance of the spectrographs that the Hubble Telescope produced and the valuable information that this provided us with concerning some characteristics of our universe. Spectroscopy, as defined by HubbleSite, deals with the study of spectra from various materials when they emit/interact with light. By using a spectrometer (or spectrograph), one can split the incoming light into component colors/wavelengths. This can provide information about material properties.
Figure 2. Hubble Telescope image of the Pillars of Creation (residing in the Eagle Nebula).
During the second Hubble mission, the Space Telescope Imaging Spectrograph (STIS) was implemented. This was a groundbreaking device at the time as it possessed the capability of outputting the spectrum of spatially extended objects (e.g. galaxies, supernovae, etc). The STIS could essentially capture the spectrum across many points within a captured image. This instrument was sensitive enough to capture a broad range of wavelengths of light, ranging from ultraviolet light to almost-infrared light.
So, what are some key discoveries that came from the Hubble Telescope and its STIS system? First, it captured the spectrum of galaxy M84 (shown in Figure 3). The associated spectrum to the nucleus of the galaxy indicated massive spikes in the center of the image. These spikes show that the stars in this region moved at a rapid pace; hence, the black hole residing at the center of the galaxy M84 was discovered. Additionally, as mentioned above, STIS is capable of simultaneously recording up to 50 different locations inside of a spatially extended object, like a galaxy. This gives it the ability to map complex environments in the universe. Capabilities like these allowed the Hubble Telescope to remain relevant for such a long period of time and has opened our eyes to things that we cannot see with the naked eye.
I’ve always been taught that light is both a wave and a particle, and I’ve never faltered in believing it. However, I chose to challenge myself and question what I’ve always known to be true. Accordingly, I explored the origins of the photoelectric effect to understand how physicists arrived at their conclusions.
In my research, I discovered Heinrich Hertz, a german physicist. In an exploration of electromagnetism, Hertz accidentally became the first person to record the photoelectric effect in action. In his trials, he noticed that his equipment would spark and in an attempt to better observe it, he moved his setup into a dark case. Curiously, the magnitude of the sparks was reduced when inside the case. This reduction was a product of the photoelectric effect, but contemporary physicists were far from understanding it.
After witnessing this phenomenon, he focused on exploring it. Reconfiguring his equipment, Hertz found that exposing electrodes to ultraviolet light changed the voltage between them. This work laid the foundation for physicists that followed, eventually culminating in Einstein’s theory of light.
