Photo Credits: M.J. Padgett, J. Leach (U.Glasgow) et al., Royal Society
As many of my fellow classmates may know, the Earth orbits about the Sun, while also spinning on its axis. It is less known however, that light exhibits the same behavior. Normally, measurements regarding light record things such as direction and energy, and occasionally the spin polarization. Light also has an orbital angular momentum (OAM) however, similar to the orbital momentum of a planet.
When focused with a lens, light with a 0 OAM measurement comes to a point, however light with any OAM value greater than 0 will focus to a ring. The twisting property of light has potential use to increase the information content of communication, or as an astronomical tool, however this is not entirely practical, and is not frequently used.
The light from a distant galaxy gets warped and distorted thanks to the immense gravity of the closer reddish-orange galaxy
We usually think light is pretty fast. Usain Bolt can set new records for how quickly man can run. There are motorcycles that can travel faster than our own nerve impulses. Aircraft has long since broken the sound barrier. And yet, we have never broken the “light barrier;” in fact, we are so pathetically far away from being able to move at the speed of light that our fastest vehicles moving 10x faster than they could, still may as well not be moving at all.
Light is fast, there is no doubt. But space is a gigantic and sometimes dangerous place, even for something as speedy and evasive as a photon. Light is not invincible, and one well-known entity that can imprison light itself is the black hole – an object of infinitesimal size but infinite density, whose gravitational pull is so strong that one would need to travel faster than light in order to escape.
An artist’s perception of a black hole. The black sphere is NOT actually the black hole. The physical black hole itself, or the singularity, is incredibly tiny, theoretically infinitesimally small. The black ball is simply the event horizon – an area of space that, were you to enter, you could never leave. It is black because the photons that are unfortunate enough to wander inside this region can never return, making it a dark, desolate place from our perspective.
It is often taught in physics that gravity comes from mass, and affects other objects that have mass. It is also often taught in chemistry that photons have zero mass. This is because the universe is weird and loves to play mind games with us. Only very recently did Albert Einstein come across a startling discovery, which he described in his famous equation, E = mc^2. In shorthand, this means that mass itself is a form of energy, and vice versa. Photons may not have mass, but they do have energy (how else would a sunny day be warmer than a cold, miserable night?).
Because of this, photons are very much affected by gravity, and will absolutely be at risk for being imprisoned by black holes. In fact, anything with gravity can and will affect light. In the first picture shown above, the blue galaxy behind the red one is warped and twisted in appearance, thanks to the immense gravity of the Red messing around with the light coming from Blue. Galaxy Blue is, of course, perfectly fine – it may not even realize Galaxy Red exists – but the photons that it emits certainly do.
As we sit comfortably on planet Earth, instinctively believing we are the center of the universe, it is sometimes easy to forget that reality may not always be how we humans see it. The cyclic visual wonder of the lunar phases, for instance, gives the illusion that different amounts of the moon are illuminated as the cycle goes on. And through this change, many implications can arise. Indeed, mythology and legend have let us to believe that the moon’s phase from our perspective can have drastic effects on our blue marble itself.
It can be counterintuitive to learn that the moon’s phases are not actually anything special. It’s simply caused by the way we see the moon – which is always half-illuminated by the Sun, just like the Earth (with a possible exception of a total lunar eclipse, in which the moon is completely in the Earth’s shadow). The moon, being tidally locked to our planet, must always show the same side of the moon, leaving the other side, the so-called “dark side” – invisible to us. But even this name is misleading. The dark side of the moon receives just as much light as the “light side.” If it didn’t, we would not have our beautiful lunar phases. A new moon is caused when all of the light from the Sun hits the “dark side,” leaving none for the side we are familiar with.
Since the moon is always half-illuminated, the phases solely depends on our perspective of it. A lunar quarter, where the moon appears half lit, is simply us seeing it exactly from the side. In a full moon, we see its entire illuminated face. The more stereotypical crescent moons are simply the moon viewed at an angle where more of the poorly-named “dark side” is illuminated compared to the light side. There really is nothing mysterious about the side of the moon we never see, nor is there anything otherworldly about the moon’s quite predictable phases.
But who knows – maybe there are those who dread looking up in the night sky once every 29.5 days.
One of the (very morbid, but still fascinating) topics I enjoy in astronomy is the concept of a black hole – and how exactly you would die if you went into one. A black hole is a place in space that is so massive and so dense that its gravitational pull is too strong for even light to escape. Scientists believe that some black holes were created when the universe was born and that others, called stellar black holes, form when the center of a huge star collapses, causing a supernova. The super tiny, super massive center of the black hole is called a singularity. The “point of no return”, the boundary of the black hole, the point at which gravity precisely counteracts light’s efforts to escape, is called the black hole’s event horizon. If matter passes the event horizon, it is not escaping that black hole.
There have been many theories over the years about black holes, due to the fact that it is very hard to study them and test the theories. Anyone who has watched an outer space Sci-Fi movie knows the very cool (but very wrong) possibility that you could somehow travel through a wormhole and come out through a different wormhole, essentially “teleportation” through space (and possibly time). This occurs in many space cartoons, Star Trek, Event Horizon, possibly 2001: A Space Odyssey (assuming that’s what the weird lights were that Bowman was traveling through at the end). A recent space travel movie, Interstellar, has the astronaut Cooper plunging into a black hole and ending up in some strange space (the tesseract) where he can see the back of his daughter’s bookshelf at every point in time.
Unfortunately, astronomers and physicists are pretty sure you can’t just go through a black hole and pop out the other side – you will, in fact, die. The real question is, how exactly will you die? There have been several theories, each with their own problems, on what would happen to you. The first way to die: spaghettification. Yes, it’s really a word. Spaghettification is the phenomena of having your body stretched out to be really thin and long (thus, like spaghetti). This would happen because as you cross the event horizon and head towards the center, the part of your body that went first (let’s say your feet) would have a greater force of gravity pulling on it than the part of your body that went in last (say your head). The difference in the force of gravity between your feet and your head would stretch you out and break you apart: spaghettification.
The second way to die in a black hole: incineration. One idea is that a person falling into a black hole would encounter high-energy quanta at or near the event horizon. This “firewall” would essentially burn up anything that tried to pass through it, meaning you would get burnt to a crisp trying to enter that black hole. If you don’t like either of those ways of dying, there are other possibilities that astronomers and physicists are contemplating. You could pass through the event horizon and then have every particle in your body scrambled. You could be ripped about by strong magnetic fields. You could split reality, fall perfectly unharmed into the black hole, and then continue to fall until you died of starvation or thirst – and be instantly incinerated in a different reality.
Black holes are mysterious, confusing objects in space, even to the most brilliant minds. Basically, they warp space-time so much that it curves in on itself, creating a hole through the fabric of reality. The laws of physics as we know them seem to break down around black holes, making it nigh impossible to figure out what exactly happens beyond that event horizon. That, and the fact that we have absolutely no way of sending anything into a black hole, much less trying to retrieve information once that instrument is inside. But while astronomers and physicists are unsure as to the specifics, one thing is very clear: one way or another, stretched or spaghettified or scrambled, you will die. There is no bookcase on the other side.
Gravity on Earth acts on all objects with the same force. No matter their mass, objects fall and accelerate at a constant rate. Due to the air resistance of different shapes, this is not always apparent. On a planet or moon lacking oxygen, the law could be simpler to demonstrate. On Earth, falling objects increase speed by 9.8 meters per second. Though gravity is a constant, there are places on earth where gravity has less of an effect than the familiar force. On the top of Mount Everest, you would experience 0.28% less of the gravitational force than at around sea level, though this is almost unnoticeable. You can read more about gravity here.
In 1589, Galileo publicly demonstrated the gravitational acceleration on objects of different masses by dropping a heavy and light cannon ball simultaneously. The larger one was ten times heavier, though each object smashed into the ground at about the same time. Due to the air, their falls were not perfectly equal in speed. The experiment helped disprove Aristotle’s argument that bodies ten times larger should fall ten times faster.
Super awesome Galileo gravity experiment in vacuum chamber Here
Visible solar eclipses are relatively rare phenomenon to witness. They occur whenever the moon gets between the Sun and the Earth. The eclipse must occur with a new Moon to completely blot out the Sun. Because the Moon must be in the right location and phase, these eclipses don’t happen very often. There are three types of solar eclipses. The total solar eclipse is the most impressive occurrence with the Moon gradually covering up the daytime Sun. temperatures fall and creatures prepare for nighttime. Once the moon completely covers up the Sun, only the surrounding light from the Sun is visible, the corona. This period is called totality. There are also more common annular and partial solar eclipses, where the Moon only slightly blocks the Sun, depending on its position relative to Earth’s umbra shadow.
Luckily, since the Sun is 400 times larger than the Moon and the Moon is 400 times closer, the two objects appear to be the same size. Unfortunately, the Moon is moving about four centimeters away from Earth a year, so this will not always be the case. The next total solar eclipse visible in the U.S. will be on August 21st of this year. It has been 72 years since the last eclipse achieved totality in the United States.
Click HERE for more details and for safety viewing the eclipse.
As we learned from Chapter 4, tides and waves are caused by the actions of gravitational force of the Moon and the Sun. Without tides, scientist won’t be able to predict the alarming predicament of global warming and the beachgoers are not able to enjoy surfing at the beach. There are also countries who generates electric from the tidal energy. So, without us knowing, tides bring advantages to us.
In Europe, the highest tides occurs at Mont Saint-Michel in Normandy, France. It is said to be having less than 50 people living there. This is because Mont Saint-Michel can only be “accessed” during low tide periods. The bay at Mont Saint-Michel is very dangerous because the sea water could rise as tall as a four-floors building and faster than a human could swim. On 30th March 1997, about 3 million people came to this place to watch the supertide or better known as “The Tide of the Century”.
The phenomena is called Spring Tide. It is caused by the alignment of the Sun and The Moon with Earth in between which usually occurs in Spring (which explains the name). The gravitational force from the Moon and the gravitational force from the Sun are added up together thus enhancing the tidal effect. I think it’s amazing how the universe works. At some point, Mont Saint-Michel is an island and at another point, it becomes an opportunity for tourists and locals to walk on the seabed while embracing the spectacular Norman architecture. Read more here.
Ever wonder where a rainbow ends or starts? And what is at the rainbow’s end? Children might think a pot of gold awaits for them there.
I might not be able to answer those questions but I can tell you about the colors of the rainbow. The reason why the have different colors.Its because, the light have a continuous spectrum of light.
Visible light is only a small range of electromagnetic wave that can be seen by our naked eyes.
From our left is gamma ray, X-ray, ultraviolet ray, visible light, infrared, microwave and radio. They are in a sequence of decreasing energy, decreasing frequency and increasing wavelength.
The small fraction of electromagnetic spectrum-visible light
As you can see, the colors composing a rainbow are actually the spectrum of light so does the sequence of the colors of a rainbow. From right, the characteristics are the same as for electromagnetic spectrum.
Scientists have created observatories to observe different type of electromagnetic spectrum-click here
Despite the name, zodiacal light is not a component of a horoscope, but is instead a band of light that is occasionally visible. The phenomenon of zodiacal light is caused by clouds of interplanetary dust particles that orbit the Sun near the ecliptic, similar to the orbit of other planets. The light from the Sun reflects from these dust particles, resulting in a visible band of light.
At certain times this zodiacal light causes a different phenomenon, known as false dawn. When the grouping of dust particles responsible for zodiacal light are oriented vertically to the eastern horizon, the thick atmospheric gases which usually block the light from observers do not cover the band of light. This results in a triangle of light near the eastern horizon before the sunrise, creating a “false dawn”.
How does tides occur? It is due to combination of gravitational pull of the Sun and moon. Tidal force affects the whole earth but the most significant effect is tidal bulge of ocean. The ground only moves by several centimeters but the sea level can increase up to several feet. Spring tides occur during full moon and new moon where moon and the Sun almost align, gravitational force of the moon and the sun sums up creating a large tidal force. Neap tides occur during third quarter and first quarter of moon phases, gravitational force of the moon is opposite of the sun creating small tidal force.
Supermoon occurs when the position of the moon is closer to the Earth than it usually is. So, the gravitational force of the moon contributing to tidal force increases dramatically. It appears brighter and closer to the earth. Unfortunately, this magnificent view unfortunately can cause natural disasters to occur.
Some of the natural disasters that might have been caused by supermoon:
The 2011 Japanese earthquake and tsunami were related to supermoon but some people debated about this as some source stated that supermoon did not occur on March 11 2011.
There is an interesting article about supermoon and its relation to natural disaster click here
Visible solar eclipses are relatively rare phenomenon to witness. They occur whenever the moon gets between the Sun and the Earth. The eclipse must occur with a new Moon to completely blot out the Sun. Because the Moon must be in the right location and phase, these eclipses don’t happen very often. There are three types of solar eclipses. The total solar eclipse is the most impressive occurrence with the Moon gradually covering up the daytime Sun. temperatures fall and creatures prepare for nighttime. Once the moon completely covers up the Sun, only the surrounding light from the Sun is visible, the corona. This period is called totality. There are also more common annular and partial solar eclipses, where the Moon only slightly blocks the Sun, depending on its position relative to Earth’s umbra shadow.
Image of 
