Physics in the Olympics

Posted on February 12, 2018 by astronomydylan
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These athletes understand physics!

We have all heard the joke which rings all too true: the Olympics need one average person competing for reference. Last night, olympic figure skaters dazzled the international community with their many spins and jumps. I found myself extremely curious as to how the skaters are able to spin so many times with apparent ease.

When a figure skater spins, as they are able to do for very long durations, they actively conserve angular momentum by bringing their arms and legs inward, reducing the distance between the skater’s center axis of rotation (the skate on the ice) and the skater’s mass. Thus, by conserving angular momentum, rotational velocity increases, and the figure skater is able to complete what appears somewhere between extremely nauseating and impossible to the rest of us.

Angular momentum is basically similar to linear momentum, which is simply calculated by multiplying mass and velocity of the object. While the formula is not the same, if no external force is present, then momentum must be conserved and not change, in both linear and angular form. Since there is virtually no friction slowing down a figure skater on the ice, angular momentum is conserved, and thus the skater is able to increase speed by compressing mass into a smaller amount of space. 

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The Map in the Stars

Posted on February 12, 2018 by Nathan Xiao

Getting around is always a difficult task. Even with supercomputers that fit in the palm of our hand and tell us how to get literally anywhere, we still get lost. That being said, it was much more difficult to navigate when all we had were the stars in the sky. Celestial navigation is a craft lost to the changing tides of time, but for a long time it was an essential skill. Primitive tribes, like the Maori from eastern Polynesia, observed the night sky, local weather patterns, and ocean currents to find their way to New Zealand.

The basics of navigation start with with the ordinate system, based on longitude and latitude, which itself is tied to the location of the stars. At the North Pole, which is 90 degrees latitude, Polaris is directly overhead at an altitude of 90 degrees. At the equator, which is zero degrees latitude, Polaris is on the horizon with zero degrees altitude.  In ancient times, navigators would measure the altitude of Polaris, and bring Polaris to the appropriate angle to find the proper altitude.

A device called a kamal was used by Arab cultures to locate Polaris and adjust their navigation accordingly. Later on, they introduced the quadrant and the astrolabe to European navigators. The astrolabe was used to find the time of rising and setting of the sun and selected stars. It was often used by Muslim cultures to find the direction of Mecca for their daily prayers.  The quadrant was a tool used to measure angles and establish a frame of reference when looking to the stars. A navigator could determine his latitude by using a quadrant to take the altitude of the sun, and then use that information to make proper adjustments.

These methods were great for finding latitude, but determining longitude was more problematic. The crux of the problem was measuring time. The creation of the sextant  served to fix this problem. Navigators could measure the angles between the moon and other bodies, measure the appropriate amount of time, and engineer out the longitude. This tool proved to be a major step forward in celestial navigation, and proved to be an invaluable tool for navigators of the stars.

astrolabe

A 17th Century Astrolabe 

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The Fate of the Universe

Posted on February 12, 2018 by Caroline Henning

The Universe may have begun in the widely accepted theory of the Big Bang. As a simple summary, the Universe began as an infinitely small, infinitely dense singularity which has since inflated for 13.8 billion years into the Universe we know today. No single theory, however has claimed the most likely outcome for how the Universe will end. A handful of theories surround the fate of the Universe, which may be summarized in three categories. These three categories are separated by the density of matter and energy in the cosmos: Ω, an unknown value.

If Ω>1, then space-time is “closed” like the surface of a sphere. If dark energy exists, such a Universe would expand forever. If it does not, the Universe would stop expanding and actually begin contracting, eventually collapsing in on itself in the “Big Crunch”.

If Ω=1, the Universe would be a flat, infinite plane, expanding in all directions. Without dark energy, such a Universe would gradually expand–but at a decelerating rate. Eventually, the expansion would come to a standstill. In the presence of dark energy, however, expansion would speed up to an unsustainable rate, eventually tearing apart the Universe in the “Big Rip”. First, the Universe’s outward expansion would tear galaxies and stars apart, eventually growing strong enough to overwhelm the forces that hold atoms together and tear them apart as well. All matter in the Universe would be left frigid and alone.

Finally, if Ω<1, then the Universe must be “open”, like the surface of a saddle. In this case, regardless of the existence dark energy, the expansion Universe would eventually accelerate to the point of the “Big Rip” as well.

In conclusion, regardless of density of matter and energy throughout the cosmos and the possible existence of dark matter, the Universe is dying (this concept is discussed in more detail in a well-written essay by astrophysicist Paul Sutter). Happy Monday!

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Twinkle Twinkle Little Star

Posted on February 12, 2018 by interplanetira

“Twinkle Twinkle Little Star

How I Wonder What You Are

Up Above the World So High

Like A Diamond in the Sky

Twinkle Twinkle Little Star

How I Wonder What You Are”

We all know the song, but do we know the science behind it? What actually causes stars to twinkle? Despite what that question may imply, the stars do not actually twinkle themselves, rather it is an effect of the Earth’s atmosphere. As the light from the star enters Earth’s atmosphere, it can hit a patch of moving air called “turbulence”. This moving air causes the light to reflect in all different directions, which from the ground, appears as a shift in the star’s brightness and/or position. We characterize this change in brightness and/or positioning as the “twinkling” of a star.

Turbulence
Source: Red Chair Blogs

 

Even though it may appear pretty in the night sky, atmospheric turbulence is actually a very inhibiting phenomenon for astronomers. Atmospheric turbulence actually makes obtaining accurate information on the brightness and the location of stars much harder for astronomers. To combat this, astronomers have started building observatories and world-class telescopes in dry, arid regions – where atmospheric turbulence would have a minimal effect. But this does not fix the problem altogether, its best to rely on telescopes in space, such as the Hubble Telescope, since they do not have any atmospheric hindrances.

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Don’t Take Light Lightly

Posted on February 12, 2018 by interplanetira

 

When you hear the word “light”, a few things might pop into your mind – the Sun, lightbulbs (or artificial lights in general), or maybe even the colors of the rainbow. What you probably don’t think about are the other forms of light on the Electromagnetic Spectrum. The fact of the matter is that our perception of “light” only includes the visible portion of the spectrum, which if laid out graphically would only take up a very small portion of the electromagnetic spectrum. In order from shortest wavelength to the longest (highest frequency to the lowest, highest energy to the lowest) is Gamma Rays, X Rays, Ultraviolet, Visible, Infrared, Microwaves and lastly Radio. Some of these might sound familiar to you, but you might’ve never thought of these as light.

electromagnetic-spectrum
The Electromagnetic Spectrum, Source: Colour Therapy Healing

You also probably didn’t think of all we can use light for (aside from, you know, seeing). We can use light to determine the composition of astronomical bodies based on their emission line spectrum. As electrons absorb photons and become “excited”, they may jump up a specific energy level. As they jump back down energy levels, they release photons of certain energy levels, which correlate with certain wavelengths, and we can use that to determine what an object is made of. We can also use this same concept to determine the velocity at which an object is moving (assuming it’s not moving tangent to us) by observing the Doppler Shift. If the spectral lines of an element are at a longer wavelength than what they are at at rest, then we know the object is moving away from us. If the spectral lines of the element are at a shorter wavelength than what they are at at rest, we know the object is moving towards us. Light has so many more forms and uses than what most people think, and they have allowed us to make many discoveries concerning the compositions and velocities of stars in distant solar systems.

Doppler+effect
Source: Socratic
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Time Travel

Posted on February 12, 2018 by Caroline Henning

Anything that has mass can bend the “four dimensional fabric” of space-time. This bending in space, known as gravity, causes objects to move in a non-linear fashion through space. According to Einstein’s theory of general relativity, gravity can bend time. By this theory, time moves faster or slower depending on your speed relative to something else–if someone in a spaceship could travel at a speed approaching the speed of light, they would age more slowly than their twin on Earth.

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Back to the Future: is time travel just for fiction?

One theory for time travel involved traveling faster than the speed of light in a vacuum. Einstein’s equations, however, show that such an object would need infinite length an a mass of zero. This seems to be generally impossible, though some scientists have extended Einstein’s equations and argued for its viability.

Stephen Hawking has suggested the method of time travel by means of the enormous gravitational force of a black hole. One would travel around the speed of light, rapidly orbiting the edge of a black hole. As they circled, they would experience about half the time of anyone on Earth. In other words, if an astronaut circled the black hole for two years, his twin on Earth would age two years more than the astronaut in that period.

Unfortunately, rotation at that kind of speed would likely blow any spaceship apart, some physicists predict. Additionally, humans may not be able to physically withstand time travel at all. Travel at nearly the speed of light would simply require a centrifuge, but would kill any person who attempted it.

Countless theories surround the notion of time travel–this blog post barely even scratches the surface. In conclusion, though, many scientists have concluded that time travel is impossible. Perhaps new technology will create avenues for time travel in the future (some wild ideas include “exotic matter”)–but in the mean time, time travel is beyond our current technological capabilities.

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The Bighorn Medicine Wheel

Posted on February 12, 2018 by alcottastr2110

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Bighorn Medicine Wheel (View from above)

 

It is very interesting to think about ancient cultures that studied astronomy hundreds or even thousands of years ago. Among these cultures were the Native American tribes. Native Americans built structures, now known as medicine wheels, in places across what is now the US. One of the most famous of these structures is the Bighorn Medicine Wheel located in Wyoming. The wheel has 28 spokes, likely to represent the days of the month or days of the lunar cycle. Different spots on this wheel align with where the sun rises and sets for the summer solstice and it is still accurate to this day. The wheel also marks different rising points of particular stars, which can correspond to particular days. It is pretty amazing that what seems like such a primitive structure is actually used for observing pretty complex information. This structure certainly brings up the question of what other astronomical observations these Native Americans made that perhaps did not get recorded to survive to modern day. It really makes me wonder what other sorts of things these Native Americans knew about back then that seem way ahead of the time, and also if they knew things about our world that perhaps we don’t even know about today.

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Solar Wind

Posted on February 11, 2018 by samssolarsystem

The corona, the outer layer of the sun’s atmosphere, can reach temperatures of up to 2 million degrees Fahrenheit.  This atmospheric temperature emits incredible amounts of thermal energy, which causes the particles in the corona to rapidly move around.  At a certain point, the sun’s gravity cannot contain these particles and they breach the sun’s atmosphere and stream into space.  This stream of particles and plasma from the sun out into space is called solar wind.  As the solar wind travels in space, it contains charged particles (ions) and strong magnetic clouds.  The solar wind gusts off of the sun in all directions at close to 400 km/s (roughly 1 million miles/hr).  However, solar wind is not constant.  While it travels away from the sun, it changes speeds depending on its location.  The solar wind is at highest speed over coronal holes (800 km/s) and lowest over streamers (300 km/s).  These different speed winds interact with each other and as the sun rotates, they pass by the Earth and clash with the Earth’s magnetic field, producing storms in the magnetosphere.

solar-wind.jpg

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Solar Wind

Posted on February 11, 2018 by samssolarsystem

The corona, the outer layer of the sun’s atmosphere, can reach temperatures of up to 2 million degrees Fahrenheit.  This atmospheric temperature emits incredible amounts of thermal energy, which causes the particles in the corona to rapidly move around.  At a certain point, the sun’s gravity cannot contain these particles and they breach the sun’s atmosphere and stream into space.  This stream of particles and plasma from the sun out into space is called solar wind.  As the solar wind travels in space, it contains charged particles (ions) and strong magnetic clouds.  The solar wind gusts off of the sun in all directions at close to 400 km/s (roughly 1 million miles/hr).  However, solar wind is not constant.  While it travels away from the sun, it changes speeds depending on its location.  The solar wind is at highest speed over coronal holes (800 km/s) and lowest over streamers (300 km/s).  These different speed winds interact with each other and as the sun rotates, they pass by the Earth and clash with the Earth’s magnetic field, producing storms in the magnetosphere.

solar-wind.jpg

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The Odds of Finding Life Outside of Earth

Posted on February 11, 2018 by Michael Natinsky

While we assume that there is no life on other planets in our solar system, the probability that there is life somewhere out there seems pretty high. It is a difficult question because we know how special earth is. It is the perfect distance away from the sun for life to form. If the Earth’s orbit was on average even an inch closer or farther from the sun, the overall climate of Earth would be dramatically different and it is possible that no life would have ever formed.

For these reasons it seems very unlikely that another planet happened to get captured in a stars orbit in the same perfect manner the Earth did. But this only applies to life as we know it. There could be life that exists in a way humans could not only comprehend. Our senses are limited. There could be methods of perception that no human could ever experience. We only know what we can observe. And it is possible that other “life” exists in a way that is unobservable to us humans.

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