Category Archives: space exploration

The planets that once were

The solar system is our home, our own comfortable little neighborhood of the galaxy, and as mankind has grown as a species and become more technologically capable, we have begun to venture forth into this neighborhood and to familiarize ourselves with it. The results are far more wondrous and varied than we could have imagined when all we knew of the cosmos was what we could see with our eyes only.

The planets that have been known of since antiquity are those that are easily visible with the naked eye – Mercury, Venus, Mars, Jupiter, and Saturn. Even before we knew of these things as astrophysical objects, they were seen as bright points of light that seemed to wander independently of the background of the stars. In the 1700s and 1800s the solar system became populated with more than just these familiar few, and as these discoveries were made it became clear that it was a more diverse place than we had suspected. As Uranus (1781) and Neptune (1846) were discovered, it was clear that these objects were of the same nature, albeit a little farther and a little dimmer. But the objects Ceres (1801) and Pluto (1930) were not so clearly determined.

Pluto and Ceres share common ground in that they both have introduced us to regions of our solar system populated by hundreds of thousands of objects: the asteroid belt in the case of Ceres, and the Kuiper belt in the case of Pluto. With these discoveries came the need to further consider the nature of these objects and the proper ways to categorize them. Ceres and Pluto trailblazed the identification of asteroids and dwarf planets, but for all the discussion they have introduced, we’ve never really gotten a good look at either one. Two recent missions have set out to correct this deficit and make us a little bit more familiar with some of the Earth’s diminutive cousins.

A size comparison of different solar system bodies. [http://www.spacewallpapershd.com/wp-content/uploads/2015/03/more_planet_size_comparisons_wallpaper_free.png]

On January 1st, 1801, Giuseppe Piazzi discovered a new object orbiting at about 2.8 AU from the sun. Although it was difficult at first to ascertain the exact size of this object, dubbed Ceres, it was clear that it was not quite in the same category as the known planets. Therefore, the term ‘asteroid’ (‘star-like’) was coined. Nevertheless, some textbooks listed Ceres as a planet among the others, and continued to do so for a number of decades.

Soon after Ceres became known astronomers found other objects to populate the region of space between Mars and Jupiter, a region that has since become known as the asteroid belt. Ceres is often referred to as an asteroid, although the new designation ‘dwarf planet’ also applies.

On March 6th, 2015, the Dawn spacecraft (http://dawn.jpl.nasa.gov/) arrived at Ceres. As it approached the asteroid, it was able to achieve stunning photos of this object, revealing a pock-marked face reminiscent of the lunar surface. Dawn continues to explore the surface and atmosphere of Ceres, revealing to us information about the formation and evolution of the solar system.

Images of Ceres as taken by the Hubble Space Telescope. [http://en.wikipedia.org/wiki/File:Ceres_Rotation.jpg]

Images of Ceres as taken by the Dawn mission on its approach to the asteroid. [http://photojournal.jpl.nasa.gov/catalog/PIA19183]

The discovery of Pluto, which took place in 1930, is much more recent, and has proved to be a bit more controversial. Many people are familiar with the discussion that took place a few years ago that resulted in the re-categorization of Pluto as a dwarf planet. Some took this hard, and consider this more of a demotion than a categorization. For the entirety of the twentieth century after its discovery, Pluto was considered the ninth planet. It was only as other objects began to be discovered in the same region of space, now referred to as the Kuiper belt, that the call for reclassification came.

The deciding moment came in 2005 when the object Eris was discovered and found to be roughly the same size as Pluto, though orbiting at a greater distance. Rather than considering Eris the tenth planet, and opening the way for some as yet unknown number of similar objects to become planets, the International Astronomical Union (IAU) decided to meet and formally consider the definition of ‘planet’. They settled on the following three properties:

  1. It must be in orbit around the sun.
  2. It must be massive enough for its gravity to pull it into an approximately spherical shape.
  3. It must have “cleared its neighborhood” of similarly sized objects and become the gravitationally dominant body.

Objects that meet the first of these two requirements, such as Pluto and Ceres, but fail the third are categorized as dwarf planets.

On July 14, 2015, the New Horizons spacecraft (http://www.nasa.gov/mission_pages/newhorizons/main/) is expected to arrive at Pluto, achieving a fly-by distance of about 10,000 km. Due to the distance between the Earth and Pluto, it will have taken New Horizons over 9 years to reach its destination. When it arrives, it will be able to take images superior to those possible from Earth with even the most powerful telescopes.

Pluto and its moon Charon, as seen by the Hubble Space Telescope. [http://nssdc.gsfc.nasa.gov/photo_gallery/photogallery-pluto.html]

For all the discussion of categorization, in the end, names are just names. A dwarf planet, by any other name, would orbit just as sweet, to butcher Shakespeare. Categorizations are a useful tool to help us understand Nature and its workings, but there will likely always be natural phenomena that defy these classifications, no matter carefully we define them. The important matter is not what we call something, but what new insights into the universe it has to offer.
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Deprovincialization

That’s us.

Much of human history can, I think, be described as a gradual and sometimes painful liberation from provincialism, the emerging awareness that there is more to the world than was generally believed by our ancestors.

Earth day was this past Monday, a good reason to give some extra consideration to that ‘pale blue dot’ that every human being that has ever lived has called home. Will there ever be a day when that will no longer be true?

Carl Sagan, owner of the above quote (from Broca’s Brain) and a chief proponent of space exploration, was always a forward thinker, often extrapolating in the most hopeful ways from present realities to future possibilities. Some of his visions may have been a bit too hopeful, such as his conjecture that “perhaps by the early twenty-first century there will be interplanetary regattas competing for the fastest time from Earth to Mars”, but in general I think he stays square on the optimistic side of realistic. And he, like another famous astrophysicist/communicator, is a huge proponent of manned space flights.

Some of the reasons for space exploration are very much down to earth, addressing such practical realities as overcrowding and resource scarcity. To put it bluntly, minerals and elbow room are limited on the planet, unlimited outside of it.

But apart from such practical considerations, Sagan also encouraged space exploration for its metaphysical returns. He speaks of this ‘deprovinciaiization’ of mankind. As we learn more about places we visit, we understand more about how where we come from, the ideas and the culture of the place we call home, fits into this larger scheme. It gives us perspective. It fills in blank areas on the map and expands our sense of the relationships between places and people. One extreme example of this is the overview effect, in which astronauts experience a change in awareness concerning the earth and its place in the universe. From space there are no divisions between countries and people.

This deprovincialization of mankind has been aided powerfully, I believe, by space exploration – by exquisite photographs of the Earth taken from a great distance, showing a cloudy, blue, spinning ball set like a sapphire in the endless velvet of space; but also by the exploration of other worlds, which have revealed both their similarities and their differences to this home of mankind.

This kind of thinking is mirrored by Steven Pinker (Violence Vanquished), who argues that the world today is far safer than it has ever been before, largely due to the growth of government and global organizations and a more educated and worldly population.

A third peacemaker has been cosmopolitanism—the expansion of people’s parochial little worlds through literacy, mobility, education, science, history, journalism and mass media. These forms of virtual reality can prompt people to take the perspective of people unlike themselves and to expand their circle of sympathy to embrace them.

Both Sagan and Pinker are addressing some very important ideas. The more we know about how we relate to people in other places, whether historical or geographical, and the more we know about the natural world, the better we understand our own circumstances at a specific place and time. Travel makes the world more peaceful. So it’s important to read and explore, to remove the barriers of ignorance. I often find that a simple walk around the block teaches me a lot about my neighborhood and a bike ride teaches me a lot about my city. The further I travel from my origin, the more I find out things that challenge my assumptions, that shake me up a bit and reveal a world I never knew existed.

The Overview Effect

Once a photograph of the Earth, taken from outside, is available… a new idea as powerful as any in history will be let loose.

Starting with this quote from astrophysicist Fred Hoyle, the film OVERVIEW explores the changes in perspective that arrived with manned space flights and accompanying images that showed, for the first time in human history, the tenuous piece of real estate on which we all reside. When viewed from this vantage point, the Earth exists as a complete and unified whole, virtually free of any arbitrary divisions created by humankind. It also appears fragile and alone, something that needs to be fought for, cherished, and protected.

It’s a brilliant and beautiful film. It may be the most wonderful thing I’ve seen so far this year.