The Opposition Effect

It was pretty obvious, an odd bright spot in the trees below that followed the helicopter. Having educated myself on quite a few optical phenomena I knew exactly what it was I was seeing, and made a point of taking a few photographs.

Opposition Effect
A bright spot in the Puna rainforest caused by the opposition effect
The mechanism for this bright spot is remarkably simple… No shadows.

Called the opposition surge, Seeliger effect or shadow hiding this simple optical phenomena occurs when looking at rough or irregular surfaces that are directly away from the light source, usually the Sun. On an irregular surface some parts will shadow other parts, resulting in an apparent darkening of the overall surface. When looking at that part of the surface directly away from the light source no shadows are seen, making that region appear brighter.

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The Volcanic History of Mauna Kea

The tour guides give the basic story behind the creation of Mauna Kea. The story given is simple… A hot spot in the mantle is the source for a plume of magma that punches through the oceanic crust and forms the Hawaiian volcanoes. As the pacific plate moves the islands are formed one by one, the latest being the Big Island of Hawaiʻi.

Puʻu Kole Panorama
A panarama from atop Puʻu Kole showing Mauna Kea and a distant snow covered Mauna Loa
This is basically correct, but is also a vast simplification of the process. If you want to learn more about the formation of these impressive volcanoes you need to look further.

Fortunately there is a good source for answers… The Geology and Petrology of Mauna Kea Volcano, Hawaii —A Study of Postsheild Volcanism, Edward Wolfe, William Wise, and G. Brent Dalrymple. This seems to be the definitive paper on the geology of Mauna Kea. Any time I see a list of references for the geology of the mountain, this paper appears. Published in 1997 it incorporates much of the earlier studies on Mauna Kea into one compendium.

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A Still-Growing El Niño Set to Bear Down on US

JPL press release

The current strong El Niño brewing in the Pacific Ocean shows no signs of waning, as seen in the latest satellite image from the U.S./European Ocean Surface Topography Mission (OSTM)/Jason-2 mission.

El Nino 2015
The latest satellite image of Pacific sea surface heights compared with 1997. Credit: NASA/JPL-Caltech
El Niño 2015 has already created weather chaos around the world. Over the next few months, forecasters expect the United States to feel its impacts as well.

The latest Jason-2 image bears a striking resemblance to one from December 1997, by Jason-2’s predecessor, the NASA/Centre National d’Etudes Spatiales (CNES) Topex/Poseidon mission, during the last large El Niño event. Both reflect the classic pattern of a fully developed El Niño. The images can be viewed at:

The images show nearly identical, unusually high sea surface heights along the equator in the central and eastern Pacific: the signature of a big and powerful El Niño. Higher-than-normal sea surface heights are an indication that a thick layer of warm water is present.

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The Most Reviled of Scientific Instruments

Scientific instruments have a habit of presenting us with uncomfortable truths. Galileo’s telescopes showed that our solar system did not conform to the prevailing teachings of the day. The great particle accelerators show a complexity underlying reality that defies a simple explanation of the universe. Likewise an almost forgotten instrument sitting atop a volcano has shown that humans have altered our world in very damaging ways.

NOAA Mauna Loa Climate Observatory
The NOAA Mauna Loa Climate Lab in the light of dawn
I had driven to the top of Mauna Loa for a session of Geminid meteor watching and photography, joining Steve, a local photographer and friend for a cold, beautiful morning atop the mountain. As we were about to leave another friend drove past. Ben used to work with me at Keck and now tends the solar observatory adjacent to the NOAA climate laboratory. Looking at the sky and the drizzling fog that had rolled in with the dawn he noted that it would be a while before he could open the telescope. Instead he offered us a tour.

It was in the main building that we stopped to look at a little instrument parked rather oddly in the hall. Not much, a simple box with a few aluminum tubes and a bit of circuitry and wiring. It took me a moment to realize I was looking at a piece of scientific history. Here was the Scripps Carbon Dioxide Analyzer that has provided the data that has changed our relationship with our planet.

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Neil Gets The Question

More than once I have gotten “The Question“.

Standing in front of the crowd under a starry sky, I spend an evening answering questions. There are many versions of “The Question”… God, UFO’s, anything where astronomy crosses with the unknown, or imagined.

There are things we just do not know. When faced with an unknown many people prefer to simply make something up, or adopt a common belief that may have no basis in fact. This is where belief and science clash… A critical skill for a true scientist it the ability to be comfortable with the unknown.

Having answered the usual questions so many times I do get better at it. I also enjoy watching other folks answer these same thorny questions, I learn and borrow some of the good lines. The trick is to somehow convey the proper skepticism of a scientific view without directly confronting the closely held beliefs of your audience. Not an easy task.

No one is better at explaining science than Neil deGrasse Tyson, Director of Chicago’s Hayden Planetarium. Watching him field questions from an audience is pure gold to anyone who does public outreach. He is personable, he connects well with the audience, and he nails the science with perfection.

Note: This article originally posted July 7, 2011 on the old Darker View blog.

Don’t take my word for it, watch the video as Neil answers “The Question”. At the end of the video Neil gives the answer I use most often for the UFO version of the question… Amateur astronomers, like myself, do not generally report UFO’s, because we have seen, and understand many of the interesting things nature can display in the sky. Education is the key.

Exploding Glass: Prince Rupert’s Drop

As anyone who has worked with glass knows, the material is fascinating. Glass is fragile, yet it can be extraordinarily strong. This is a seeming contradiction, but one that makes sense if you start to understand what makes glass crack.

Via Phil at Bad Astronomy, a truly awesome video on Prince Rupert’s Drop, a simple construct of glass that exhibits the strength and weakness of glass in a very visual way.

Science is cool!