January, 2014Archive for

Searching for Life in our Solar System

Tuesday, January 21st, 2014

Titan in Natural Color

Astrobiology is the study and search for extraterrestrial life – exotic life forms existing on other celestial bodies. While studies are underway searching for intelligent life throughout the galaxy such as SETI, there are a few places astrobiologists are looking in our own solar system.

Titan

Titan is the largest moon of Saturn, almost twice the size of our own moon. It is a unique celestial body in our solar system, in that it is the only satellite with a dense atmosphere, and has evidence of liquid on its surface.

Artist rendering of Titan’s Methane lakes

Titan’s atmosphere is primarily made up of Nitrogen, and is much thicker than Earth’s. This makes it extremely opaque, and for many years we had no idea what the surface looked like. In 1995 Hubble used its infrared instruments to image the surface of Titan, and discovered shallow lakes of liquid methane on the surface.

These lakes may support life, in a way that Earth’s oceans do. Instead of carbon based life, these creatures could be methane based, where they would inhale Hydrogen, and exhale methane. While no concrete evidence of these exotic life forms exists, the necessary building blocks are there. There are numerous plans to return to Titan (the Huygens probe landed on the surface in 2005), though none have been funded as of yet.

Enceladus

Enceladus’ icy surface

Enceladus is a small moon that orbits Saturn. It is only about 500km across, or about 13% the width of our moon. It exists about 238,000km away from the surface of Saturn, and takes 218 days to orbit.

Enceladus has recently been deemed the most habitable spot in the solar system beyond Earth. This is because Enceladus is covered in water ice, and is also extremely geologically active. At the southern end of the moon, giant plumes of liquid water spray out of the icy surface like geysers. These jets of water, known as cryovolcanoes, turn to vapor and give Enceladus the most notable atmosphere of any solar system moon outside of titan. The jets also indicate the core of the moon is warm due to tidal heating from Saturn’s gravity, which could allow for a water ocean underneath the ice. Fractures and a relatively low number of impact craters indicate the entire surface is tectonically active – another sign the moon is warm in its core.

Enceladus’ Cryovolcanoes

This warmth, along with water oceans, may lend itself towards the existence microbial extremophiles, if the hot rocky core is releasing its energy through hydrothermal vents. The existence of life using this method can be seen on Earth at extremely deep and geologically active points in the ocean, where no energy by means of sunlight can be utilized.

Europa

View of Europa’s Icy Surface

Europa is the fourth largest moon of Jupiter, only slightly smaller than our own moon. It is similar to Enceladus in that it is covered in water ice, and also believed to be warm at its core due to tidal heating from Jupiter’s gravitational pull. As with Enceladus, this could also harbor microbial life at or near hydrothermal vents. Additionally, it has been calculated cosmic radiation could convert some of the oxygen locked up in the surface ice into free oxygen in the oceans beneath. This could conceivably support larger life forms, such as small fish.

While Europa is thought to be one of the best chances for finding life in the solar system, the likelihood of a very thick ice shell makes it difficult to access the inner ocean. However, In December 2013 it was discovered that Europa also has large plumes of water, some as high as 200km, ejecting out of its surface, similarly to Enceladus. If these jets are releasing water from the subsurface oceans, it would be relatively easy for orbiting spacecraft to study the chemical makeup of the water vapor, and determine if life does in fact reside there.

Rendering of the proposed interior of Europa

Recently the US House Appropriations Committee has supplied $80 million in funding for the creation of future Europa exploration missions. These missions include Europan flybys, orbits, and eventually landing on the surface. These missions ultimately are intended to determine the likelihood of extra terrestrial life on Europa. Additionally, the Jupiter Icy Moons Explorer (JUICE), was recently approved by the European Space Agency, which will spend some time observing Europa. This mission is set to launch in 2022.

Warp Drives. Science Fiction, right?

Monday, January 13th, 2014

A warp drive, at a conceptual level, is a propulsion system that allows faster-than-light travel. Under Einstein’s Theory of Relativity, this is currently impossible. This is because any object with mass would require infinite energy to accelerate to the speed of light.

Currently the fastest manmade object ever to exist was the Helios II probe, which made an elliptical orbit around the sun at approximately 70km per second in 1976. Blisteringly fast compared to Earth based travel, but only about .023% the speed of light.

Spacetime contracting and expanding around a warp drive spacecraft.

The Alcubierre Drive

In 1994 physicist Miguel Alcubierre published a paper outlining a possible mechanism for faster than light travel by altering space-time around a craft. Among the many flaws in the system, it required both negative mass (which hasn’t been proven to exist), and more energy than all of humankind could produce.

The drive works by exploiting the ability to manipulate space-time by contracting it in front of the craft, and expanding it in the rear. Thus a “warp bubble” is produces, and although the contents within the bubble do not travel faster than light relative to its local space-time, the craft will arrive at its destination faster than light traveling through static space-time. In essence, the distance between the craft and its destination shrinks.

Artist rendering of an Alcubierre/White warp drive

White’s enhancements

In 2012 physicist Harold White submitted a simple yet effective change to the warp drive in order to reduce the mass-energy requirement to a feasible size (that of the Voyager 1 spacecraft, approximately 700kg). To do so, he proposed a “doughnut shaped” warp bubble, rather than a sphere. He also proposed a reduction in total energy needed by oscillating the warp drive over time.

Difficulties

There are a number of issues with the Alcubierre drive, even with the refinements made by White. For instance, it has been argued that the craft could not control the bubble once engaged, therefore steering and stopping would be impossible. Also it has been suggested that the amount of Hawking Radiation would destroy anything within the bubble. It also is heavily dependent on whats known as “Exotic Matter”, or matter that currently defies the standard laws of physics.

Pillars of the Big Bang

Monday, January 6th, 2014

Where did the universe come from? Perhaps one of the most puzzling and inspiring questions humanity has ever posed. Countless religions, philosophers, and scientists have tried to answer this question, often at odds with one another. In the last century, scientific discoveries have finally given us a clue as to how old the universe is, what the early universe was like, and ultimately, what happened at the moment of creation.

The Big Bang Theory

Generally speaking, the Big Bang Theory is the overwhelmingly accepted concept for the creation of the universe. It essentially states that all of the matter and energy currently in the universe was at one time located in a single point of space – with infinite density – in what is known as a singularity. For reasons we are still not quite sure, the singularity exploded and sent pure energy out in all directions. As the early universe cooled, the energy began forming the earliest forms of matter, including protons, neutrons, and electrons. Over time, these particles formed the first elements, primarily Hydrogen and Helium. As the universe continued to expand, gravity took over and these elements formed the first stars. We can now say with relative certainty that the universe is about 13.8 billion years old.

The Four Pillars

Evidence for the Big Bang Theory comes from four distinct but related observations of our universe, which all directly support the theory’s key concepts.

Big Bang Neucleosynthesis

As mentioned, the early universe formed the first elements, a majority of which was Hydrogen, along with some Helium. These are the three lightest elements in the periodic table. We would expect to see about 75% of the early universe made up of Hydrogen, about 25% Helium, and about .01% of other trace elements such as Lithium. Upon observation of the universe as a whole, we find the ratios of these elements in the exact ratio we would expect, which is a strong indication our understanding of how early matter formed is correct.

Cosmic Microwave Background Radiation (CMBR)

WMAP visual representation of the CMBR

In the 1960’s Bell Labs built a radio antenna originally designed to communicate with early satellites. After its need was exhausted, it was turned over to two scientists, Arno Penzias and Robert Wilson took over use of the horn-shaped dish. When attempting to study radio signals from distant galaxies, they noticed no matter what direction they pointed the antenna, a weak but consistent electromagnetic signal was being received.

This signal is now known as the Cosmic Microwave Background Radiation. Shortly after the big bang, calculations indicate that a tremendous amount of radiation would have been emitted in all directions. Billions of years later, this intense radiation has settled into a faint microwave radiation, only a few degrees above absolute zero. Since Wilson and Penzias’ discovery matched exactly the prediction radiation, it became another strong support for the Big Bang model of the early universe.

Expansion and Hubble’s Law

One important requirement of the universe in order to support the Big Bang Theory is that if the universe started at a single point, and we now exist inside of it, it must have expanded. Based on the calculations of the early universe, we would expect the universe to be very large right now, and still expanding in all directions.

Representation of Red Shifting light from an object moving away from us

This was ultimately confirmed in 1929 by astronomer Edwin Hubble. Hubble discovered that distant galaxies (at the time called nebulae, because they were considered still a part of the Milky Way Galaxy), were receding from us. He determined this by analyzing the light emitted from these galaxies, and determined it was slightly stretched out from what we would expect. In the same way that sound can sound higher and lower as a moving vehicle passes you with the Doppler Effect, light waves can also compress and expand based on the velocity of the source. In all directions, distant galaxies seemed to be shifted towards the red end of the spectrum, hence the term Red Shift.

The Red Shift of galaxies in all directions indicates that the entire universe is expanding, and in almost all cases galaxies are spreading apart from one another. It stands to reason that if we play back the universe in reverse, all of these galaxies would at one point in time come from the same location – The Big Bang.

Galactic Structure and Evolution

Hubble’s Galactic Evolution

The final and most recent observable support for the Big Bang is how galaxies form over time. A valuable and important tool we have when studying the universe is the fact that light travels at a finite speed. This means light emitted from distant galaxies will not reach us for billions of years. Thus, we can look at the most distant observable galaxies and see what they looked like billions of years ago, in the early universe.

What we see is a very different picture of what we currently see in nearby galaxies. Early galaxies are simple in their structure, essentially “blobs” of young stars. Galaxies such as the Milky Way have ornate spiral structures, which have formed over billions of years. We also see, as we look back into the more recent past, that larger structure of galaxy clusters start to form which did not exist in the early universe. This is strong evidence that the complexity of the universe is increasing, meaning the universe must have at some point been much simpler than it is now.

Book Review: My Brief History – Stephen Hawking

Thursday, January 2nd, 2014

Relative to the rest of his works, Stephen Hawking’s Autobiography, aptly named My Brief History, is actually a fairly quick read. However even in its brevity, it still could be split into two significant parts – a biographical portion and a scientific portion.

The first half is a fascinating journey of his early life, including his family’s struggles living in England during and after World War II. For both parents being “Intellectuals” as he calls them, they actually were not particularly well off, as his father made a living from research grants to study tropical diseases.

Stephen worked his way up through the educational system of the time, and made his way into Oxford knowing he wanted to study physics. Cosmology (science of the origin and fate of the universe), was Stephens ultimate passion, but was not a well studied field at the time, primarily due to the explosion of particle physics after the advent of the Hydrogen bomb. Nevertheless, Stephen worked his way into a research position as a grad student at Oxford, and began his quest towards his greatest discoveries.

Of course one of the most notable facts about Stephen Hawking is his battle with ALS, and he thoroughly discusses his symptoms and physical deterioration throughout the battle. He does not, however, discuss it as if it was a curse, but rather just a challenge he faced.  He states more than once how he is fortunate to be a theoretical scientist, as almost any other career would be impossible for him.

The second half of the book starts becoming more of a discussion on his scientific research. He bounces back and forth between technical commentary and relevant life experiences during the time, which is very interesting, if not a bit confusing. The closer his story gets to the present day, the more interested he is in explaining his discoveries and theories, which tend the story towards some of his more technical writings. For someone who has read his books such as A Brief History of Time (to which this book owes its namesake), The Universe in A Nutshell, The Grand Design, etc, it is a familiar and welcome style of writing. These sections may be a bit off-putting to someone who is new to Hawking’s technical writing.

I thought this was an excellent autobiography that settles itself perfectly between being a life story and being a learning experience.  Though Hawking is one of the most important and recognizable scientists of our time, he does not approach his biography with any sort of egotism or pride. In fact in many cases his humility leaves the story a bit lacking. Nevertheless, I am glad to have read it, and hope you might consider enjoying it too.

Verdict: 4/5