How Did the Universe Begin?

Discoveries in astronomy and physics show the universe had a beginning 13.7 billion years ago. Prior to that moment, there was perhaps nothing but during and after the moment, our universe came into existence for reasons we still do not understand. The Big Bang theory tries to explain what happened during and after the moment. Astronomers speculate that our universe sprang into existence as "singularity," which are regions of infinite mass density that defy our current understanding of physics. However, no one knows what or where that singularity came from. What we do know is that volume of the universe inflated to huge sizes in the fraction of a second after the "bang" occurred. The temperature of the universe one second after it began was 10 billion degrees Fahrenheit. As the universe continued to expand, it continued to cool down, allowing the formation of fundamental particles like neutrons, electrons, and protons that decayed and/or combined to form the cosmos that we know today.

Although the Big Bang theory is widely accepted as the explanation of what happened after the "bang" that began our universe, it does not offer explanation for "bang" itself. Some theories attempting to explain the cause of the Big Bang include the oscillating universe theory and the chaotic inflation theory. The oscillation theory builds upon the Big Bang theory in that it believes the universe starts with a Big Bang, experiences a Big Crunch and repeats the cycle again with another Big Bang. Therefore, the Big Bang that occurred 13.7 billion years ago was just another step in the continuous cycle. Stanford physicist Andrei Linde also proposed a different possible explanation in the 1980s: chaotic inflation. Linde considered the possibility that the Big Bang may have been "a scattered and irregular inflation" that occurred wherever the right potential energy was available instead of being a single event. The Cosmic Microwave Background findings in the 1990s in fact showed variations of intensity that provided supporting evidence for the chaotic inflation theory.

While predictions from the Big Bang have been supported by observations, one of the main problems with the theory is that the temperature of the universe is nearly uniform. If the Big Bang marked the beginning of the universe, then according to some explanations, there has not been enough for the universe to reach the temperature equilibrium. Instead, the most plausible explanation for that uniformity is that, soon after the beginning of time, some unknown form of energy made the universe inflate at a rate faster than the speed of light so that the temperature in the inflated cosmos would be nearly the same everywhere. Alternative theories to inflation supported by the Big Bang explain this problem. For example, a group of theoretical physicists proposed a new theory that the beginning of the universe could have happened after a four-dimensional star collapsed into a black hole and ejected debris. Their reason to doubt the Big Bang theory is that “the Big Bang was so chaotic, it’s not clear there would have been even a small homogenous patch for inflation to start working on.” Instead, they proposed a theory in which the three-dimensional universe floats as a membrane in a four-dimensional "bulk universe." Since the bulk universe has four-dimensional stars, the stars go through the same life cycles as three-dimensional ones and when the massive ones explode as supernovae, their innermost parts collapse as a black hole and create a three-dimensional membrane surrounding the boundary between the inside and the outside of the four- dimensional black hole, the event horizon. Then, expansion would occur as a result of the three-dimensional membrane's growth. While this is an interesting possibility of the "bang" and the short period after it, the main question that must be asked of this or any other alternative theory is whether it provides testable predictions. It is ultimately only through observations that we know how the universe began.

Sources:

http://www.space.com/25126-big-bang-theory.html

http://www.space.com/13320-big-bang-universe-10-steps-explainer.html
http://www.theepochtimes.com/n3/679834-3-alternatives-to-the-big-bang-theory/
http://www.universetoday.com/104863/goodbye-big-bang-hello-hyper-black-hole-a-new-theory-on-universes-creation/

- Alice Zhang

The Origin of Life on Earth

How life originated on Earth is a question that scientists have studied for centuries. Today, two leading theories for life's origin are abiogenesis, in which life arose naturally by chemical reactions, and panspermia, in which life arrived on Earth from elsewhere.

Before introducing the abiogenesis hypothesis, I would like to talk about the spontaneous generation theory that states that life arises suddenly and spontaneously from lifeless material. People before the 19^th century believed fervently in the spontaneous generation theory. For instance, people observed that worms would be produced in a sealed bag of garbage, not realizing that worm eggs had gotten into the garbage before the bag was sealed. It was during the 19^th century that Louis Pasteur designed experiments that proved that living organisms cannot arise from non-living material. Thus, the spontaneous generation idea was refuted.

The abiogenesis theory is also called the chemical evolution theory. Like spontaneous generation, it says that life arises naturally from lifeless materials. However, the timescales over which life forms is much longer than that of the spontaneous generation theory. In other words, in abiogenesis, life arises in a series of chemical reactions that do not occur suddenly. The first life must been extremely simple forms such as small organic molecules, which combined to form larger biomolecules, and then combined to create primitive living organisms.

The panspermia theory is very different from the abiogenesis theory; it maintains that microscopic living organisms were initially carried to Earth by an asteroid or comet. In other words, primitive life originated naturally in an extraterrestrial environment and then landed on Earth. However, this hypothesis is not viewed favorably by most scientists, who argue that outer space itself is too harsh an environment to allow unprotected cells to survive over a long period of time. Thus, a theory related to panspermia called "weak panspermia" is more popular. The idea states that it was not cells, but only ingredients of life, such as organic molecules, that were delivered from space. Evidence for weak panspermia includes the Murchison meteorite, which contains over 14,000 different molecules that would be capable of helping to spawn life. The evidence not only shows the presence of organic components in outer space, but also points to the ability of these materials to reach Earth.

The theories of the origin of life on Earth remain debatable, but they are worth pondering.

Sources:

http://www.asa3.org/ASA/education/origins/chemical-cr.htm

https://www.cfa.harvard.edu/~ejchaisson/cosmic_evolution/docs/fr_1/fr_1_chem2.html
http://serendip.brynmawr.edu/exchange/node/1919

- Cora Wu

The Mayan Calendar

The Mayans are an incredible civilization that achieved amazing feats in science and astronomy; one of them was the development of the Mayan calendar. The Mayans were a pre-Columbian civilization located in Central America that was obsessed with the cosmos. That obsession influenced everything from their pyramids (which each had four 91-step staircases and a platform on top, making 365 steps in all) to when they were going to plant and harvest. Their astronomical knowledge was extremely advanced for their time; for example, they could predict solar eclipses and solstices hundreds of years in advance. For example, Harvey Bricker, author of "Astronomy in the Maya Codices," found a Mayan calendar that dated to the 11th or 12th century that accurately predicted a solar eclipse to within a day in 1991, centuries after the Mayan civilization had ended.

The Mayan calendar dates back to the 5th century BC and is still in use today in a few Mayan communities. The Mayan calendar actually does not consist of one but rather of three calendars: the Tzolkin, the Haab, and the Long Count. The Tzolkin is the divine calendar that consists of 260 days, divided into 20 periods of 13 days each. It was used to determine the time for religious ceremonies and it is related to nine moon cycles and the zenith of the Sun. The Haab is a 365 days solar calendar that is divided into 18 months of 20 days each and one month of five days. There is evidence that they knew that a year was not exactly 365 days but their primitive numerical system did not allow them to calculate the exact length of a year. The Long Count is an astronomical calendar that was used to calculate longer periods of time since the other two restarted every 52 years. The Long Count had a period of 1,870,756 days (5,125.36 solar years) or 13 b'ak'tuns, which was referred to as the universal cycle. It started on August 11, 3114 BC, the day the Mayans believed mankind was created and ended on December 21, 2012 with the universe destroyed and recreated. The mystery lies not in why the world did not end but how were they so precise to calculate the end to be exactly on the winter solstice.

The Mayans did not have complex instruments for charting the position of celestial objects; their observations were with the naked eye. They may have had rudimentary instruments such as crossed sticks but not instruments such as sextants. Although they did use their buildings as instruments, they aligned the temples to help observers monitor the position of celestial objects, like the Sun or Venus. Two of the corners pointed in the direction of the Sun (one pointed towards the Sun as it rose, the other as it set) so that on the Spring and Autumn equinox, at the rising and setting of the Sun, the corners of the structure casts a shadow in the shape of a plumed serpent or Quetzalcoatl along the west side of the north staircase. On these two annual occasions, the shadows from the corner tiers slither down the northern side of the pyramid with the Sun's movement to the serpent's head at the base.

Still the question arises: how did the Mayans do it? We still do not know exactly the answer to this question but it is truly amazing that they were able to do things like create extremely precise calendars, calculate the solstices and equinoxes, and calculate when the Earth and Mercury are aligned hundreds of years in advance.

Sources

http://www.webexhibits.org/calendars/calendar-mayan.html
http://content.time.com/time/health/article/0,8599,2114645,00.html
https://explorable.com/mayan-astronomy
http://www.livescience.com/26070-maya-predicted-1991-solar-eclipse.html

- José Uribe

Space: the Final Frontier or Our New Home?

While humankind populates Earth and flourishes at the moment, it is rapidly depleting the resources that Earth has to offer, making it impossible to sustain its current growth. Even with research and development in renewable resources, we will eventually run out of natural resources and be forced to colonize a new planet, either to inhabit or from which to extract resources.

The first step in expanding off of Earth is to find a suitable planet that we can inhabit. There are two possible locations for space colonization, either on a planet, moon, or asteroid, or in orbit. There are different advantages to both: a planet could provide natural resources and would require a much lesser technological requirement while an expansive space habitat in orbit would require an enormous amount of resources, but it would provide a stable environment. However, a large space habitat that would orbit in space is largely unrealistic with our current technology.

If we choose to live on a planet, moon, or asteroid, there are two choices as well: a location near Earth such as Mars, which we could resupply relatively easily, and exoplanets, which are much farther away but could provide more habitable resources. For long-term or permanent inhabitance, planets close to Earth are unlikely candidates. These planets do not possess “Earthlike” conditions, which can sustain life. These conditions include possessing a similar gravity to Earth to prevent muscle and bone loss, a strong atmosphere to protect the inhabitants from radiation, and a temperate climate, all of which could vary depending on our technology in the future and how we can protect ourselves from them. However, what makes settling exoplanets unlikely is their distance from the Earth. According to NASA, the closest terrestrial exoplanet candidates to Earth are Alpha Centauri Bb and Tau Ceti e, which are 4.23 and 11.90 light years away respectively. However, Alpha Centauri Bb has since been rejected as a habitable planet since it orbits too close to its star.

Plans to establish a settlement on an alien planet would require thousands of people so that the gene pool doesn’t face inbreeding. These thousands of people would all need to be trained before going into space, which seems impractical. One solution to this problem would be sending frozen sperm and eggs on the voyage so that there would be a population boom if the colony manages to start up. This would reduce the amount of people needed to a fraction of what it was before. However, this option is still not desirable, as it would require the facilities and resources to successfully breed thousands of people.

As of now interstellar travel is viewed more as of science fiction than as a viable possibility, since it is effectively impossible given our current technology. Before we plan for these ambitious missions to colonize space, we first must develop the technology in order to do so. As of now, a mission to colonize Mars or the Moon would only serve as a test for colonizing space. It is a much-needed experience so that when we are actually forced to colonize a new planet, the probability of success will be greater and we will know what possible complications may arise from it. We shouldn’t be dissuaded from exploring space; when the technology arises, we will be able to utilize it to its fullest extent.

Sources:

http://settlement.arc.nasa.gov/Basics/wwwwh.html
http://en.wikipedia.org/wiki/List_of_nearest_terrestrial_exoplanet_candidates
http://news.discovery.com/space/tau-ceti-another-interstellar-target-121223.htm
http://www.space.com/26603-interstellar-starship-colony-population-size.html

- Charles Wang

The Importance of Bioastronautics for Our Journey to Mars

If we can send landers and rovers such as Viking I, Viking II, and Pathfinder to explore Mars, then why can’t we send humans there as well? Many responses indicate the limited budget of NASA, the heavy weight of humans and the resources that are needed for humans as compared to rovers, and fear of disasters such as those that befell the space shuttles Challenger and Columbia. Although these are all valid concerns, one vital concern that is often not mentioned is the bioastronautics of spacefaring.

This is an example of how Earth's
atmosphere diffuses incoming cosmic
rays, protecting us from these
cancer-causing rays.

Bioastronautics is the study of biological aspects of life in space. Life-threatening situations in space are more than just the asteroid fields and flying debris as depicted in sci-fi films; they also include the damaging effects of cosmic rays and the debilitating effects of microgravity. Cosmic rays are ions, mostly protons, that race through space near the speed of light. While our atmosphere protects us from these cancer-causing rays, in space, astronauts do not have the same amount of matter between them and these ions. When these ions pass through the human body, more ions are created and chemical bonds are broken. A unit of radiation dosage is measured in rem. The average annual cosmic radiation dosage received by a human on Earth is 0.03 rem. On a trip to Mars, astronauts would receive as much as 80 rem a year. This amount of radiation would induce cancer as well as cataracts and brain damage. Solar flares also produce dangerous bursts of protons and heavy nuclei. These bursts can deliver a radiation dose in the hundreds of rem in an hour or so- “a lethal dose for unshielded astronauts.”

Microgravity is another concern for NASA’s astronauts. Initial symptoms of microgravity include disorientation, pallor, malaise, loss of motivation, irritability, drowsiness, stomach awareness, and infrequent but sudden vomiting. These symptoms usually fade away in two to three days; however, the lasting effects of bone degeneration continue throughout the time astronauts are in space. Calcium eliminated through urination and defecation causes up to three hundred milligrams to be lost per day. Although it is still unclear whether acute calcium loss is completely reversible, there are exercises and diets given to astronauts to minimize calcium loss in space. To be sure, bone decalcification has few consequences in space; the major concern is the return of astronauts to Earth’s gravity. If humans were to colonize Mars, which has about one-third the gravity of Earth, they would be subjected to the effects of Mars' light gravitational pull over their entire lifetimes. Prolonged exposure to such conditions on the human body has yet to be tested.

In order to research these effects, on September 11, 2014, NASA increased its contract with Wyle Integrated Science and Engineering Group of Houston from $75 million to almost $1.5 billion. Wyle is a leading provider of specialized engineering, professional, scientific, and technical services to the federal government, and is the number one life-services provider to NASA. As listed on their website, one of Wyle’s primary responsibilities to NASA is to “investigate operationally relevant environmental issues associated with human space flight.” The twenty-fold increase in the budget outlay from NASA to research bioastronautics will hopefully allow us to venture to Mars in the near future.

Sources

http://www.nasa.gov/press/2014/september/nasa-extends-increases-value-of-bioastronautics-contract-at-johnson/#.VRKmvpPF84Q
http://www.space.com/11417-mars-missions-space-travel-challenges.html
http://www.faa.gov/education/educator_resources/educators_corner/grades_7_8/losing_calcium_in_space/
http://www.wyle.com/about-us.html

- Siqi Yang

Where is Everybody?

“Where is everybody?” is a famous question that physicist Enrico Fermi asked when talking with a group of scientists about extraterrestrial life in 1950. This simple question has attracted many scientists’ attention. With a hundred billion stars in the galaxy, even if there is a slim probability of planets developing technological civilization, there should be a large number of them. However, until now, the Earth is the only known planet where such a civilization has developed. So, where is everybody?

In 1959, Giuseppe Cocconi and Philip Morrison wrote an article called “Searching for Interstellar Communications” and published it in Nature. In the article, they suggest that the way to communicate with extraterrestrial life is by using radio waves since the galaxy is transparent to them. It was the first time scientists had proposed a specific strategy for searching for extraterrestrial intelligence.

Soon after Cocconi and Morrison’s article was published, Frank Drake came up with an equation that estimates the number of technological civilization that may exist in the galaxy. The equation is written as

N = R^* x f_p x n_e x f_l x f_i x f_c x L

N is the number of civilizations in the Milky Way, R^* stands for the rate of formation of stars suitable for the development of intelligent life, n_e is the number planet per solar system that is suitable for life, and L stands for the length of time that the intelligent civilization needs to emit detectable signals into space. F_p, f_l, f_i and f_c refer to different fractions, from that of the stars with planetary systems to that of civilizations that release detectable signs of their existence into space. Depending on the values that we adopt for each variable in Drake’s’ equation, the number of intelligent civilizations in the Milky Way can vary from less than a thousand to about a billion. However, even though there is a debate on the exact values of the variables in the equation, Drake’s equation is generally accepted as a tool for estimating how many intelligent civilizations may exist in the galaxy.

Currently, there is no hard evidence supporting the existence of extraterrestrial life. Therefore, in his essay, “An Explanation for the Absence of Extraterrestrial on Earth,” after rejecting all other hypotheses, Michael H. Hart claims that the best hypothesis that can explain this fact is that that there are no other advanced civilizations in the Galaxy. Hart groups the hypotheses that assume there is life in the galaxy into four main categories: physical explanations, sociological explanations, temporal explanations, and past-visit explanations.

Physical explanations say that extraterrestrial visitors have never arrived on Earth because they are physically or intelligently incapable. Nonetheless, using mathematical calculations and the example of Apollo and Skylab missions, Hart concludes that neither the time of travel nor the energy required would render a visit impossible. Therefore, Hart rejects the physical explanation. Sociological explanations include any hypothesis that the extraterrestrials have chosen not to visit the Earth. Hart also rejects this proposal, saying that the social structure and the interest in space travel should have changed throughout their history. Holding the same belief for thousands or even millions of years is not plausible. In addition, Hart believes that if the hypothesis is true, scientists would be able to find evidence of extraterrestrial life in the space, but the lack of proof indicates the argument is not valid. Even if the physical and sociological explanations are rejected, temporal explanations, which say that extraterrestrial life has not yet had the time to reach the Earth, may still be valid. However, since our galaxy is at least 10¹⁰ years old, there has been ample time for extraterrestrials to visit. Hart argues that the temporal explanation is plausible but highly unlikely. There is also the possibility that extraterrestrial beings have come, with some perhaps leaving after their visits and some perhaps staying unnoticed among us. Hart questions these hypotheses and believes further study is needed to prove them. For now, Hart concludes there is simply no extraterrestrial life.

Sources

http://www.seti.org/drakeequation
http://www.geoffreylandis.com/percolation.htp
http://www.bigear.org/vol1no1/interste.htm
http://www.nasa.gov/sites/default/files/files/Archaeology_Anthropology_and_Interstellar_Communication_TAGGED.pdf
http://adsabs.harvard.edu/full/1975QJRAS..16..128H

- Jiaxuan Liu

Dark Matter - What We’re Missing

Dark matter sounds exactly like what it is: elusive and fantastic. Dark matter was first hypothesized to exist by Vera Rubin, and since then the search for it has expanded to dominate almost all particle physics research. In 1970, while observing redshifts of galaxies to measure their rotations, Vera Rubin noticed something horribly off with the speeds of these rotating spiral galaxies. From what she could see, the galaxies were spinning much faster than they should have been able to with the mass they had. Somehow, they weren’t ripping themselves apart. She came to the conclusion that what she could observe, what she called “luminous mass,” did not comprise all of the mass in the galaxy. She called this unknown substance “dark matter,” as it does not interact at all with light, but still has mass and provides gravity.

The question that particle physicists have been wondering since Rubin’s discovery has been: how do you see something that can’t be seen? To start with, physicists have tried to get other theories to explain dark matter, so they can at least try to define how the particle acts. The Standard Model does not account for any sorts of particles that could form dark matter. To make matters worse, two opposing theories postulate the existences of two different types of dark matter, “hot” and “cold.” Hot dark matter would be very small and travelling at nearly the speed of light out of the Big Bang, as researched by Yakov Borisovich Zel'dovich, while cold dark matter would be much more massive and slow, as researched by James Peebles. It is now held that for galaxies to form after the Big Bang, both hot and cold dark matter must have been present.

Physicists have examined many candidates over the years to see if they fit the role of dark matter, even delving into physics beyond the standard model. The first candidate for the extra mass in the universe was ionized gas clouds. It only made sense, given that some were ten times the size of the galaxies they inhabited. However, it was quickly discovered that the gas clouds did not have anywhere near the requisite gravity dark matter provided. Black holes were thought of as another possibility, after all, they have so much gravity that they absorb even light. But even black holes cannot provide the amount of gravity needed to keep galaxies together like dark matter does. It would take a million black holes’ worth of gravity to replace the dark matter in an average galaxy! Neutrinos were thought of as the perfect candidate for hot dark matter because they only interact through the weak nuclear force and have an almost-zero mass. However, as discovered by the Sudbury Neutrino Observatory, neutrinos definitely have mass, but not enough to provide galaxies with the gravity needed to stay together. At this point, nothing within the standard model can account for dark matter, so scientists are now considering looking at the supersymmetric extensions of standard model particles. Possible dark matter particles are now classified as WIMPs, or weakly interacting massive particles. Out of the WIMPs, the most promising as of now seems to be the LSP, or lightest supersymmetric particle, because it is stable in almost every supersymmetric theory and only interacts with the weak nuclear force. Now that a particle that fulfills every requisite for dark matter has been identified, it is only a matter of time before it is synthesized and its existence is proven.

Sources:

http://home.web.cern.ch/
The 4-Percent Universe by Richard Panek
"Dark Matter Detection" by P.F. Smith & J.D. Lewin (Physics Reports)

- Jacob Lee

Introduction to Time Travel: Let’s Travel into the Future!

We live in a world with three spatial dimensions: width, height and depth. One might think that is enough to accurately pinpoint a location. But let’s think about this more carefully. Let’s say my friend is hosting a party. Excited to be social, I ask him where it will be located. He says, “Of course! It’s on the corner of 34^th Street and 4^th Avenue in NYC.” Visualizing NYC as a two-dimensional grid, I now know where the party will be located in the x and y direction. He continues and says, “Oh yeah, I live on the third floor. Apartment number 36149. See ya later.” Perfect- now I know exactly where the party is. Thinking the z-axis as height, I have pinpointed an exact point in space where the party will be. I have all the information to go to his party…or do I? Although I know exactly where this party will be held, I have no idea when it is to happen. Tomorrow? Next week? In three years? Without a time, the location of the party is just a concept. Just like how a line is physically impossible as it has no thickness, a three-dimensional object (or place) cannot exist if it not passing through time. So time is our fourth dimension. Now the question is if we can manipulate objects within the three spatial dimensions, can we also manipulate our fourth dimension, time?

There have been countless books having characters go into a time machine and travel back/forward through time. There have been countless movies with time travel as the main plot device. There have been countless theories on time travel, from the absolutely absurd ones to ones take make sense in the realms of physics. Let’s take a look at one plausible way of traveling into the future: traveling at high speeds.

Einstein’s special theory of relativity is one of the most commonly used ideas to prove that theoretically one can time travel. This theory is based on two ideas: (1) the laws of physics are the same for everyone, regardless where they are in space, and (2) the speed of light is constant for every person that is in uniform motion. Einstein’s theory leads us to think that if there was one person on Earth and one person in a spaceship that could travel very near the speed of light (like 99.0006% the speed of light), the person on the spaceship could travel out into space, come back, and find he/she is much younger than the person on Earth. To look at this more in depth, Einstein developed a thought experiment by using light clocks. These clocks are made up of two mirrors with light reflecting in between them. With two mirrors that are three feet apart and assuming that light travels at 300,000 kilometers/second, it takes one photon three nanoseconds to get from one mirror to another. That is one “tick” for the clock. Using the spaceship example again, if a light clock was put into a transparent spaceship, the observer on the ground will see something peculiar. As the spaceship moves, the light bouncing in-between the mirrors will look like it’s going in a zigzag pattern. The light will actually travel more distance between the two mirrors than three feet because to the observer on the ground, the light from the mirror has already shifted to the right due to the speed of the spaceship (the diagram illustrates this). If distance has grown, but the speed of light is still constant, then that means time must have increased. The person on the ground will see the ticks of the light clock to be longer than three nanoseconds.

Now instead of a light clock and its ticks, let’s look instead at a person’s heartbeat. The same concept applies; the person on the ground will see (or hear) the heartbeat of the astronaut in the spaceship to be much slower. Biologically, this means the person on the ground sees the person in the spaceship to be aging slower. Conversely, after traveling through space at the speed of light, the person on the spaceship will come back to Earth noticing he is a lot younger relative to everything on Earth. Thus, the person in the spaceship has time traveled into the future.

Sources:

J. Richard Gott. Time Travel in Einstein’s Universe
http://en.wikipedia.org/wiki/Special_relativity

- Eric Lee

Measuring Enormous Distances

Our planet Earth is only a tiny piece of rock in a vast, expanding universe. When philosophers and astronomers began to look out into space several thousand years ago, it was impossible to determine how far from us a star or galaxy in the sky was. Today, we know of multiple ways to measure distances to various objects that we find. Some of these methods are mostly effective in determining nearby distances, while others have the potential to measure objects that are incredibly far away. In this post, I will be discussing three methods that are used to determine large distances within and beyond our Milky Way galaxy.

The simplest and most straightforward method of measuring distances within our galaxy is called stellar parallax. This technique involves nothing other than basic geometric calculations. Parallax is the change in a star’s position due to the change in the observer’s point of view. As Earth orbits the Sun, we look at stars at different angles. Stars nearer to us appear to move relative to those lying farther away. By measuring the angle of displacement of a star relative to its background, we can easily obtain the distance from us to said star. There is a simple relationship between parallax angle and the distance: d = 1/p , where d represents distance in parsecs and p represents the parallax angle measured in arcseconds. Unfortunately, this method is only useful for near distances (less than about 100 parsecs.) Anything farther will have a displacement that is undetectable. We, however, have alternative methods of measurement, which is good considering that most stars in the Universe are farther than 100 light years from us.

A second method involves the use of Cepheids, or Cepheid Variables. Cepheids are luminous stars that pulsate in a predictable way. By measuring the period of a distant Cepheid, astronomers can calculate the luminosity of the star. The longer the period, the brighter the star is. Using the known absolute brightness of the Cepheid, we can calculate the distance by comparing the absolute brightness with the apparent brightness. The apparent brightness of a star is how bright or dim we see an object from where we stand. A faraway object will look dimmer than if it were closer to us. Using this difference, Cepheid variables can be used to accurately measure distances in our galaxy, and even distances to nearby galaxies.

A more effective method for estimating large distances uses Type 1a Supernovae. Unlike other supernovae, Type 1a’s are caused by the destruction of a white dwarf star with a companion star. White dwarfs are one of the densest forms of matter and their gravity therefore is intense. In binary systems, these dwarfs can pull matter from their companion star. Once these white dwarfs reach a critical mass, they explode (the critical mass is called the Chandrasekhar limit; it is approximately 1.4 solar masses). Similarly to the Cepheid method, the apparent brightness of the explosion is compared with the known luminosity of all Type 1a Supernovae. The difference can be used to calculate the distance. This method is known to work for distances up to about 1 billion light-years; for comparison, the nearest galaxy, the Andromeda Galaxy, is approximately 2 million light-years from our solar system.

Over the years, astronomers have come up with incredibly accurate ways to measure the massive distances of space. From stellar parallax to Supernovae, we can determine distances ranging from our nearby stars to galaxies lying a billion light-years away.

Sources
http://starchild.gsfc.nasa.gov/docs/StarChild/questions/redshift.html
http://lcogt.net/spacebook/cepheid-variable-stars-supernovae-and-distance-measurement
http://news.discovery.com/space/supernova-cosmos-distance-galaxies-110827.htm
http://hubblesite.org/hubble_discoveries/dark_energy/de-type_ia_supernovae.php
http://www.universetoday.com/21914/the-closest-galaxy-to-the-milky-way/

- Sarah Shy

What is SpaceX?

For decades, Americans have been used to seeing one space agency: the National Aeronautics and Space Administration (NASA). Recently, a new space agency has entered the field, SpaceX. Founded in 2002 by Elon Musk, of PayPal and Tesla Motors fame, SpaceX has been rapidly growing towards meeting its goal of space colonization. Currently, it possesses two models of rockets: the Falcon 9 and the Falcon Heavy. The Falcon 9 is currently used for various missions, including resupplying the International Space Station. SpaceX currently possesses a $1.6 billion contract with NASA to resupply the International Space Station, for at least 12 missions. Currently, they are using the Dragon capsule to transport cargo to the ISS, but it was actually designed for human use. The first manned test flight with Dragon is slated to occur in the next 2-3 years, and is expected to take astronauts to the International Space Station by 2017.

The proposed Falcon Heavy,
which is planned to launch later
in 2015.

The rockets of SpaceX are very innovative. The Falcon Heavy, which is still currently in development, will be the most powerful rocket in the world by a factor of 2. Also, in the past, rockets have only been able to be used once; however, SpaceX is currently trying to develop a program that would allow rockets to be reusable, by landing the first stage on a large floating platform. This could greatly diminish the cost of launching, which is currently at a very affordable $100 million, in comparison to the $200 million launch costs of the past. An attempt was made in January 2015 to make a soft landing on a floating platform, but the booster made a hard landing and it was unable to be recovered, due to the hydraulic fluid, which stabilizes the booster, running out. Nonetheless, with the number of rockets launches that are planned in 2015 (13), it is just a matter of time before the first stage of a rocket can be recovered and reused. Also, when the Falcon Heavy is launched in late 2015, the plans are for it to have the two boosters and the middle core booster to fly to Earth and make upright landings.

SpaceX has greater aspirations than just providing an alternative way of resupplying the International Space Station. It has begun to launch micro-satellites to provide high-speed and low-cost internet to people across the globe. In addition, Musk wants his internet system to expand all the way to Mars, so it can also have internet access. In regards to SpaceX’s ultimate mission of space colonization, Musk stated that the Mars Transport System would be announced later in 2015, with the goal of being able to transport 100 metric tons of payload to Mars. A journey to Mars could be just a couple of years away, and is certainly possible in the conceivable future. With SpaceX leading the way, space travel could see a lot of changes in the near future.

Sources
http://www.technologyreview.com/news/526806/spacex-brings-a-booster-safely-back-to-earth/
http://spacenews.com/42305next-falcon-9-launch-could-see-first-stage-platform-landing/
http://www.spacex.com/about/capabilities
http://www.spacex.com/about
http://www.bloomberg.com/news/articles/2015-01-17/elon-musk-and-spacex-plan-a-space-internet

http://www.space.com/28396-spacex-reusable-megarocket-video.html
http://www.spacex.com/falcon-heavy

- Kevin Li