Tag Archives: astronomy

Supermoon

If you haven’t heard already, today is a “supermoon.” Today, the moon is closer to the Earth than it has been since 1948. Visually, that means it will be bigger and brighter than usual. Intellectually, it’s gratifying to watch the cosmic ballet go on. Our solar system is like a Swiss clock, all the parts proceeding and, for the most part, fitting together perfectly. Winter (northern hemisphere) supermoons are slightly bigger because the Earth is closer to the sun; the sun’s gravitational power pulls the moon slightly, such that the supermoon is bigger. Astrobob explains it better here.

For more pontifications on the moon, check out What If the Moon Didn’t Exist, which I reviewed here. Below are some of my favorite photos of the moon, and a moonrise video over Chaco Canyon, New Mexico.

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Chaco Canyon moon, stars, and clouds

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Chaco Canyon: New Mexico’s ancient convention center

Chaco Culture National Historic Park is in remote northwest New Mexico. The drive will take you on twenty miles of dirt roads and beyond cell range. But in this most remote reach of New Mexico lies the crossroads of an ancient culture. In Chaco Culture National Historic Park lies 3,614 recorded archaeological sites, including many massive great houses. The largest, Pueblo Bonito,  has roughly 800 rooms; visitors may walk through the doors and rooms of Pueblo Bonito. The Chaco Culture also built astronomical features into many of their works; some windows align perfectly with the sun on solstice, and some decorations align with phases of the moon.

When Chaco was discovered in modernity, it was thought to be a vast city. Having walked through it, it feels that way. It feels like it could hold thousands. But archaeological evidence suggests otherwise—there is little garbage, and few burials. Massive Pueblo Bonito may have housed only 70 people on a permanent basis. The guides at the park suggest that Chaco might have been a meeting ground, used for trade and weddings and astronomical ceremonies for a small portion of the year. Remnants of cacao from 1200 miles south have been found at Pueblo Bonito. The bones of macaws, native to eastern Mexico, have been found at Pueblo del Arroyo. They apparently didn’t flourish; only the bones of adults were found. So the astonishing quantity of ruins at Chaco Culture Park may be the remnants of an ancient convention center.

Chaco offers an amazing range of ruins, from the many-roomed grand houses to petroglyphs to astronomical markers to ancient stairs and roads. Like Mesa Verde National Park, not so far to the north, the whole site was abandoned in the 1300s, well before European influence. Like Mesa Verde, archaeologists don’t know exactly why the people left. There is evidence of an ancient drought. Some argue for catastrophic deforestation after all the building at Chaco (because all that construction took a terrific amount of timber, some of which still remains in the structures), though there is not consensus.

I grew up in St. Louis, a town once called Mound City for the mounds left by the ancient Mississippian culture. The massive city at Cahokia was also abandoned around the year 1300. A city of 15,000 abandoned, around the population of London at the time, and we don’t know why. It’s easy to live in the United States and think of it as the new world. But these amazing works of ancient people live on quietly. The inconvenient mounds of St. Louis were largely destroyed; those who did so may not have even realized their origin. But the remnants of the Pueblo culture at Chaco remain, mostly protected by their isolation over the years. Though the journey today is easier than it ever has been, Chaco is still hours from the interstate and quiet. As I took in the ruins, I was filled with the same wonder and questions that Cahokia Mounds always presented. Places like Chaco and Cahokia are reminders of humanity—no matter the size of the structures we build, one day people will view the barren remnants and wonder about us. We will walk the same valleys and cliffs, touch the same stones, but we won’t know each others names or voices or values. Ruins like Chaco remind of us of our place in the universe, and how beautiful and belittling that can be.

 

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The stars through my tent at Chaco Culture Park. Chaco is one of the night sky parks, where the darkness of the sky is specifically preserved through lighting choices and such. In light of the ancient Pueblo interests in astronomy, it seems appropriate.

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Sunrise at the camp site.

Book now with the Exoplanet Travel Bureau

(You may have a wait while the technology for your flight is developed.)

A lot of my first reading as a child was astronomy books and magazines. When I was little, my brother told me there was a black hole under his bed (to keep me from snooping—nerd children fight dirty), and after that, I had to know more about the enigmatic and alarming properties of the universe.

One of the things I remember was the hunt for the first exoplanet, that is, the first confirmed planet outside of the solar system. Scientists were quite sure they should exist (why wouldn’t they?), but the equipment and techniques thus far hadn’t shown them. I remember reading about some of the first exoplanets in the hazy early 90s. They were massive, close to their stars, and had outrageous properties that inspired wild imaginings.

Now confirmed exoplanets number in the thousands. And poking around the internet on an unrelated chore the other night, I found this gem: the Exoplanet Travel Bureau. NASA’s Jet Propulsion Laboratory (the extremely prestigious and awesome JPL) made travel posters for four exoplanets in the style of retro travel posters. Each of them features characteristics of their planet. I promptly printed out three and hung them in my guest room. I’m still ecstatic about them; these are the kinds of visions and dreams I had so long ago as a kid, and that I love to chase in my own art. These are awesome, and I love them, and you can download them at full size. Tell all your friends, and print your own! Here they are!

Click on the image for more image sizes. Images by the NASA Jet Propulsion Laboratory.

Click on the image for more image sizes. Images by the NASA Jet Propulsion Laboratory.

Click on the image for more image sizes. Images by the NASA Jet Propulsion Laboratory.

Click on the image for more image sizes. Images by the NASA Jet Propulsion Laboratory.

Book review: What If the Moon Didn’t Exist? (Neil F. Comins 1993)

What If the Moon Didn’t Exist? is a book that asks just that– what would Earth be like if the ancient collision that led to our present-day moon never happened and the Earth had no moon? Comins, a professor of astronomy and physics at the University of Maine, also asks what if the moon was closer, what if the Earth was smaller, what if the Earth was tilted like Uranus, among other questions.

This book is a must-have for science fiction writers interested in writing about other planets. Comins follows through on his initial questions in a way that science fiction enthusiasts will appreciate. If the moon didn’t exist, the moon’s tidal pull wouldn’t exist. Due to the lack of that tidal pull, Earth’s day would be 8 hours long, not 24. Which would cause much stronger winds and storms. And the tides would be lower. Which would impede the transition of  life from water to land. And that life would have to adapt to the windy, stormy short days. Would that life develop hearing, with all that wind? Would plants opt for low-surface-area needles instead of broad leaves? Assuming humans developed, how would early man tell time without a lunar cycle? Would this influence man’s scientific development? Comins asks and suggests answers to all of these questions. It’s exciting food for thought, and it made me want to go dream up worlds of my own.

What If the Moon Didn’t Exist? is over twenty years old now. I expect some of the science in it may be outdated (none that I actually noticed, but given the advances in planetary science since 1993, it seems likely). However, the logic the book employs is sound, and I still found it very stimulating. And in researching this post, I discovered two more recent books my Comins: What If the Earth Had Two Moons? written in 2011 and The Hazards of Space Travel: A Tourist’s Guide written in 2007. They seem similar in tenor and I expect to like them too.

Fun Science: Vacuum and Pressure

Pressure is caused by collisions between particles. Scientists use the term “vacuum” when there are few particles, and thus few collisions. Air in our atmosphere is dense with particles; atmospheric pressure is very high compared to lab vacuum or the vacuum of space. Scientists use vacuum in many ways. Vacuums were used in lightbulbs and vacuum tubes (such as the old CRT or cathode ray tubes of old TVs and computers). Vacuums are used for depositing materials in clean environments, such as on silicon wafers for microcircuitry. Vacuums are used for separating liquids that have different evaporation points. In scientific labs, we can produce pressures billions of times lower than atmospheric pressure, but the pressure in space is still lower.

Atmospheric pressure: Every cubic centimeter (also called a milliliter) of air contains 2.5 x 1019  air molecules. That’s 25,000,000 trillion molecules, where the US debt is roughly $12 trillion, and a terabyte (TB) hard-drive holds a trillion bytes of information. That is a lot of particles causing a lot of collisions. The average particle travels only 66 nanometers before colliding with another particle. That’s only about 200 times the size of a nitrogen molecule.

On top of Mount Everest: Pressure is roughly 1/3 of the pressure at sea level, and there are 8 x 1018 molecules of air per cubic centimeter. The average particle travels 280 nm before colliding with another particle.

Incandescent light bulb: The pressure inside a lightbulb is 1 to 10 Pascals (pressure at sea level is 100,000 Pascals). There are still about 1014 molecules/cm3, or 100 trillion molecules. The average particle travels a mm to a cm before a collision. This pressure is too low for plants or animals to survive.

Ultra high lab vacuum: The most sophisticated lab vacuum equipment can produce pressures of 10-7 to 10-9 Pascals, yielding about 10,000,000 to 100,000 molecules/cm3, respectively. Particles travel an average distance of 100 to 10,000 km before colliding with another particle. Such extreme vacuums require highly specialized equipment, including specialized pumps and chambers. Only certain materials can be used; paint, many plastics and certain metals can release gases at very low pressures, making them unsuitable.

Space vacuum: The vacuum of space depends on what part of space you mean. The pressure on the moon is 10-9 Pa, or roughly our highest lab vacuum, with 400,000 particles/cm3. The pressure in interplanetary space (within the solar system) is lower yet, with only about 11 particles/cm3. It is estimated that there is only about 1 particle per meter cubed in the space between galaxies. Still, some microorganisms have survived exposures of days to space vacuum by forming a protective glass around themselves.

Going the other way, there are pressures much higher than the pressure of our atmosphere.

At the bottom of the Mariana trench: Pressure is about 1.1 x 108 Pa, or about 1100 atmospheres. A variety of life has been observed in the Mariana trench.

At the center of the sun: Pressure is about 2.5 x 1016 Pa, or 2.5 x 1011 atmospheres, or about 100,000 times the pressure at the core of the earth. This pressure is sufficient to fuel the fusion process of the sun, where hydrogen is combined to form helium.

At the center of a neutron star: Pressure is about 1034 Pa, or 1018 times the pressure at the center of the sun. Here, pressure is so high that normal atoms with electrons around a core of protons and neutrons cannot exists. Nuclei cannot exist in the core of a neutron star.

Read about other science topics on my fun science page.

Fun Science: Gravitational waves

Gravitational waves were first predicted in 1916 by Einstein’s general theory of relativity; today we are trying to directly observe them. A gravitational wave is a tiny oscillation in the fabric of space-time that travels at the speed of light; all other findings from general relativity predict its existence. Many objects will create minuscule gravitational waves, and even the largest objects create ones we just barely hope to see (such as binary stars and black holes). From the LIGO wikipedia page “gravitational waves that originate tens of millions of light years from Earth are expected to distort the 4 kilometer mirror spacing by about 10−18 m, less than one-thousandth the charge diameter of a proton.”

What would we gain from this? Astronomers believe that gravitational waves could eventually become another mode of imaging by which to analyze the universe, like gamma ray, x-ray, and infrared imaging.

Example of gravitational wave distortions (from wikipedia)

The LIGO (Laser interferometer gravitational-wave observatory) ran from 2002 to 2010; it was unsuccessful in its hunt for gravitational waves. It is being recalibrated to restart in 2014. The two observatories in Louisiana and Richland, Washington record the same events and compare the time at which they arrive. Below is a schematic of this set-up. LISA, the laser interferometer space array, has been discussed for years as an orbiting detector with greater length scales (and therefore greater accuracy) than LIGO; a proof-of-concept is due for launch in 2014.

Laser interferometer set-up (wikipedia)

If you want to learn more, Einstein Online, which is run by the Max Planck Institute, is a great resource (the Max Planck Institute is involved in great cutting edge research, perhaps comparable to NASA). The above link is for info on gravitational waves, but there is also great info on other concepts related to relativity if you are interested.