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.
Reflecting on how science and astronomy have grown and blossomed into what we study today really illustrates how amazing ancient feats of astronomy and observation were. The impacts of archeo-observations of the night sky still effect us today, including in the name of months, the days of the week, and the length of our days and years.
Many monuments have been discovered that illustrate the feats of engineering and calculation that ancient peoples achieved to record and interact with celestial events like solstices and equinoxes.
One of the most interesting (in my opinion) examples that we mentioned in class, is the Samarkand observatory known as Ulugh Beg’s observatory. This structure was built in the 1420’s, over a hundred years before the completion of Stonehenge, and was used by Ulugh Beg to house a 36 meter (118 ft) tall sextant. Half of the sextant was underground to ensure that the building was not too tall. The lower portion of the sextant is all that remains today, though descriptions of the building in its prime allow us to better understand other measurements that were taken there.
The sextant would have been used to measure the angle of elevation of celestial objects, especially during solstices, when light from the sun would shine through a small opening and alight on the track of the device, providing precise angle measurements.
Ulugh Beg and his astronomers calculated very precise measurements with this observatory, most shockingly, the measure of Earth’s tilt in relation to the ecliptic! His results were incredibly close to modern measurements.
Ancient Greek philosophers such as Plato and Aristotle deduced that moving heaven bodies makes circular motion because a circle is the perfect heaven path. Later scientists such as Tycho claimed that heavenly bodies are pushed by angels. Nobody previous to Isaac Newton was aware of the concept “Gravity.” Perhaps the most famous legend about gravity is that the idea of gravity came to the mind of Isaac Newton when he was struck by a fallen apple under the apple tree (though it might not be true at all).
Where G is the gravitational constant; r is the distance between two objects; m1 and m2 are mass correspond to two masses. It can be seen from the formula that gravity exists between any two objects. It would be safe to conclude that modern science and humanity’s understanding of the Universe took flight after Newton discovered gravity.
Nonetheless, though Newton’s classical law works perfectly in most cases, it failed to explain some phenomena. For example, Newton’s physics cannot explain why a clock on a high-speed airplane might be slightly slower than a clock on the ground. Here enters Albert Einstein:
Einstein developed a whole new idea of gravity: general relativity and specific relativity. According to Einstein, a 4-dimensional spacetime is a unified entity of space, time, and gravity resulting from the spacetime curvature. Since light travels through spacetime, massive objects will also be bent. Einstein’s theory was substantiated by discovering “Einstein Cross,” which is perfectly predicted by his general relativity theory. There are four images of a distant star because the light emitted was bent a massive object.
Nevertheless, modern particle physics claimed that gravity resulted from the exchange of elementary particles between two objects. Gravity, along with EM force, the strong-interaction force, and the weak interaction force, are four fundamental forces in the Universe. All objects with mass exchange graviton and thus creating attraction force within. The range of this exchange is infinite.
Human beings have been working on gravity for hundreds of years, yet we still have conflicting (also complementary) theories regarding what causes gravity. Our endless exploration is ahead of us.
Telescopes have come a long way since they were invented in 1608. Not only have ground based telescopes made significant advances, but in recent decades telescopes have even been launched into space to mitigate the effects of Earth’s atmosphere on observations. The very first space telescope was the Orbiting Astronomical Observatory 2, or OAO 2 […]
A simple video that shows why we observe retrograde motion of planets
It is often easy to look back at historical astronomical theories and think that they were silly or nonsensical. Of course, hindsight is 20/20, and with what ancient astronomers knew at the time, it makes sense that they created bizarre models of the universe. Retrograde motion is a phenomenon that gave scientists a lot of trouble in the past and was responsible for many astronomical oddities such as the use of epicycles. Retrograde motion is when planets pause their night-to-night migration across our sky and move backwards for several nights. We now know that this is a natural result of our heliocentric solar system—see the video for a simple visualization—but in the geocentric models of the past, the cause of retrograde motion was a mystery. Astronomers kept coming up with increasingly complicated models with nested epicycles in their attempts to explain retrograde motion, like Ptolemy’s impressively accurate theory, but heliocentrism was the big breakthrough that explained all planetary and stellar motion with one elegant idea.
The Hubble Space Telescope has been a staple in the NASA space program since its launch in 1990. It has led to monumental discoveries and pictures such as the famous Hubble Deep Field; however, 30 years later, technology has evolved tremendously and so, NASA has launched a new telescope aimed at succeeding it.
Planning of the James Webb Space Telescope (JWST) began in the early 1990s when NASA astronomers wanted to improve upon the design of the Hubble Space Telescope. That being said, it took over 30 years for it to be fully funded, developed, and launched. The JWST is so impressive due to size of the mirror, or should I say the size of the combined mirror segments. The JWST is comprised of many mirror segments that fold up in order to launch; however, each segment is moved into a specific position by extremely precise motors following the launch.
The mirror segments combined are the size of a house and have the capability of showing us (humans) extremely faraway places in our universe. While the JWST was launched only a few months ago on December 25, 2022, it has potential to lead to some amazing discoveries in the near future. I hope to continue following its progress and see what great things follow for the JWST.
Rendering of the James Webb Space Telescope (NBC News)
As you may have heard in the news recently, the James Webb Space Telescope (or JWST) was launched into space on December 25, 2021. The JWST is meant to be the successor to the Hubble Telescope, as it detects light further into the infrared spectrum than the Hubble telescope, and so can see stars that are older and further away which are more redshifted due to the expansion of space. The JWST also has a light collecting area that is over six times that of the Hubble telescope, enabling it to have far better light gathering power and resolution.
The telescope began to be developed in 1996, but was only launched last year after a series of delays. The JWST was launched into orbit at the Lagrange 2 point, which is a spot in Earth’s solar orbit about 1.5 million kilometers away from Earth. The launch was nearly perfect, allowing the telescope to save fuel and extend its potential mission time from 5-10 years to about 20 years.
The selfie taken by the JWST of itself little more than a week ago (Space.com)
On February 11, we received the first images from the JWST, which included a selfie of the telescope and its first image of a star being used to calibrate the telescope’s mirrors. With the JWST, astronomers are hopeful to learn more about older artifacts of the universe and potentially about the beginning of the universe itself.
