Friday, January 25, 2013

All I ask is a dung ball and a star to steer her by

Image Credit: Dacke et al. / Current Biology via NBC News
Humans are not the only animals to navigate using the sky.  Numerous birds and other animals use the sun and moon as navigational cues, and birds and seals also use stars.  Evidentially so do dung beetles, which also use the Milky Way, according to a new study in Current Biology by Swedish scientist Marie Dacke and collaborators.  (Insert your own dung-related joke here.)

Dung beetles are important insects who help to break apart the large mounds of dung produced by large animals.  They go to a pile, make a ball, and then head for home as fast as possible to try and keep other dung beetles from stealing their hard-earned treasure.  The best way to do that, of course, is to make a bee-line for home.

Being a small insect in a big world, dung beetles use visual clues to help go home.  Previous researchers found that dung beetles use the sun, moon, and polarization of the light in the sky to orient themselves and move in a straight line.  But the beetles still work if the sun and moon aren't in the sky.

Dacke and her collaborators tried to figure out what else the beetles might use to orient themselves.  They made a little arena for the dung beetles and timed how long it took them to get their dung ball out of the stage area, first with visual clues and then without.  The latter involved putting blinders on the beetles, as seen in the picture below.  This part of the experiment made me glad I am not a dung beetle researcher.
Dung Beetle hats.  Image credit: Marcus Byrne via
Anyway, to cut to the heart of the matter, the researchers found that the beetles could steer their dung balls straight (meaning they can get away from potential dung thieves quickly) under a moonless, starry sky but only if the Milky Way was visible.  Bright stars alone weren't enough.  This was tested both in the wild and in a planetarium.  Here's a drawing from their paper showing these paths.  On the left are beetle tracks under a Milky Way-lit, moonless sky, and the right are tracks made when the stars were not visible.  That's a significant difference!
Dung beetle tracks.  Dacke et al, Current Biology, (c) 2013 Elsevier Ltd
In my opinion, this is really cool.  We've known for a long time that animals can navigate long distances using all sorts of clever techniques, whether it be salmon finding their way back to the stream of their birth, arctic terns navigating from one polar sea to another, or Europeans off  to exploit the wealth of the East Indies.  So it is not surprising that even simple animals can use multiple cues to steer by.  But still - beetles using a faint smear of light draped across the sky is a wild (and seemingly correct) idea.

We shouldn't be too surprised that this technique evolved.  The moon is not visible in the night sky half of the time, so being able to steer by another celestial light is a useful adaptation.  And while the Milky Way is not always visible in the starry sky, the Milky Way is often visible when the moon is not, and vice-versa. 

Another neat finding is that the beetles cannot use bright stars to steer by.  In the planetarium, researchers projected only bright stars, and the beetles were almost as lost as if it were a blank sky.  I'd guess this is due to their poor eyesight being unable to detect the light of a single star.

I once had to navigate by the light of the Milky Way.  I was at Las Campanas Observatory in Chile at the time of the New Moon.  It was the night before I was to start using the telescope, so I was in their library working one evening and I lost track of time.  When I realized that it was night, I decided to walk back to my dorm room.  But it was so incredibly dark, I couldn't see the sidewalk when I first came out of the library.  Knowing that there was a pretty sizable and dangerous drop on one side of the walk, I didn't want to risk moving.  Being an observatory, there were no walkway lights or outdoor lights.  It was pitch black except for the stars overhead.

As my eyes adjusted, I was happy to find that the light of the stars and the Milky Way was sufficient to light up the sidewalk, and I was able to walk easily and safely back to the dorms.  Little did I know I was channeling my inner dung beetle!

Dung beetles can navigate by the Milky Way.  That's so cool!

Dacke, M., Baird, E., Byrne, M., Scholtz, C., & Warrant, E. (2013). Dung Beetles Use the Milky Way for Orientation Current Biology DOI: 10.1016/j.cub.2012.12.034

Tuesday, December 18, 2012

The true dangers of December 21, 2012

December 21, 2012.  The end of the world.  Mayan calendars.  Rogue planets.  Asteroids.  Pole shifts.  Magnetic madness.  Fire and brimstone coming down from the skies. Rivers and seas boiling. Forty years of darkness.    Earthquakes, volcanoes.  The dead rising from the grave. Human sacrifice, dogs and cats living together. Mass hysteria!  (Venkmann et al, 1984)

As a scientist, it is very tempting to dismiss these ideas out of hand and without a word (or with a few humorous statements before moving on to real science).  There is absolutely no scientific basis to any of the over-the-top scenarios being touted as certain to happen this Friday.  Granted, a few of the scenarios (like asteroid impacts or solar flares) have a needle or two of science deep in the hyperbolic haystack, but that science has been distorted and twisted to serve utterly non-scientific ends.  The sun will rise on December 22, and no creature on this planet besides a few humans will be surprised by that development.

No, the true dangers of this Friday lie with us humans.  NASA scientists have been getting emails and calls from genuinely worried children and teachers of those children.  Many of us adults are comfortable joking about doomsday theories because we've seen many doomsdays come and go, a trend that dates back to Assyrian and Sumerian civilizations

But children don't have that perspective. I remember when I was in kindergarten and I heard that Skylab was going to fall back to Earth.  Despite my parents' assurances that it would most likely hit Jaws, I still nervously watched the skies.  Why would the news talk about it if it wasn't a big danger?   And the 2012 date has been in movies, on the news, discussed by "documentaries" on supposedly serious cable channels, and splashed all over the Internet.  If I were that kindergartner today, I'd be freaked out. So if you know a child who expresses any concern about the end of the world, reassure them that the world is not ending, and that they and their friends will be safe.  Schoolchildren have enough real news to worry and frighten them without the need for fictitious dangers.

Doomsayers are also preying on other vulnerable people.  Millions of dollars of books, videos, survival kits and doom bunkers have been sold. (Which begs the question - if these charlatans truly know the world is ending, what's the point of collecting money for goods and services?  Money won't be useful in their post-apocalypse scenarios).   These snake-oil salesmen target many different groups of people: those who are already nervous about the economy, those who are deeply religious, those who are paranoid, those who are not well-educated.  And on December 22, these swindlers will be laughing all the way to the bank with no legal repercussions, while their victims will have spent their life savings or even gone into bankruptcy over worthless fears.

Many people with mental health issues also suffer from well-publicized end-of-the-world scenarios.  Many of these people are not capable enough of rational scientific thought to be assured that this 2012 hooey is just that. 

"Popular" doomsday scenarios like 2012 are much more insidious than simply the deranged ravings of a few kooks.  Some polls suggest 10% of Americans think the world will end this Friday.  I suspect that is high, but even if it is just one out of a thousand people who is truly worried, that still ads up to over 7 million people worldwide.  (And what number of them are stocking up on guns and ammunition with the sole aim of protecting themselves in a post-apocalyptic world?  I shudder at the thought).

There are real threats to humanity, and the phantom threats about this Friday are not among them.  Hoaxes like 2012 distract us from these very real concerns.  To name just a few: violence, disease, nuclear proliferation, global warming, hunger, poverty, hatred -- all of these are very real threats.  We must better educate ourselves and our children to be able to discern clear and present dangers from monsters that hide in our closets at night.  Alas, my personal doomsday scenario is that we will fail in that crucial mission.

Here are some trustworthy and sound sources on the 2012 Doomsday Hoax:
  • NASA - Beyond 2012 - NASA scientists lay out some of the commonly cited agents of doom and the science disproving each.
  • - Scientists and rational citizens have created a massive repository of the hoax, its roots, its proponents, its lies, and the scientific truth.
  • Resources for Responding to Doomsday 2012 - Scientist and educator Andrew Fraknoi has created a compendium of links with honest discussions and facts about 2012, especially useful for educators needing to address students' concerns

Tuesday, August 28, 2012

Even white dwarfs must obey Einstein

The white dwarfs are 1/3 the Earth-Moon distance apart
The Earth-Moon system (top) and binary white dwarf system (bottom) to scale.  Click to enlargify.  Earth (right) and Moon (little brown spec on left) images from NASA/JPL/Galileo; artwork by yours truly.
3,100 light-years away in the direction of the constellation Gemini lurks one of the most extreme pair of stars that we know about.  Two white dwarfs, the remains of ordinary stars similar to the sun, whirl around each other every 12 minutes and 45 seconds.  As they orbit, Einstein's theory of general relativity predicts that their gravity distorts space and time itself, and these distortions (called gravitational waves) carry away some energy from the system, forcing the two white dwarfs to draw ever nearer.  Locked by gravity in a slow death spiral, these white dwarfs are destined to collide and merge in two million years. At least that was the prediction, and today it was confirmed by an international team of astronomers (including many friends and colleagues of mine, though I wasn't involved).

Wednesday, July 18, 2012

What professional astronomers know about telescopes (often, not much!)

Professor Astronomy and the Kitt Peak telescopes.
Yours truly at Kitt Peak in 2002 (I think).
Most people assume that we astronomers know everything there is to know about telescopes.  After all, we use giant ones for much of our work!  So it shouldn't be surprising that one of the most common questions we get asked (after the black holes and aliens have been addressed) is something like: "I've been thinking about getting a telescope.  What should I get?"

Many of these people are then quite disappointed to find out that I cannot help them much.  Sure, I give them the standard (and excellent, IMHO) advice that they should avoid $49 specials at Walmart, start with binoculars and then, if still interested, progress to something like an Astroscan. (Full disclosure - I own an Astroscan and love it, but I don't get any compensation whatsoever to talk them up).

But if you ask me which is better: a Celestron NexStar or an Orion StarMax, and I will give you a blank star.  I have no clue.  Or if you ask me why your iOptron SmartStar Maksutov has this weird coma when you put a certain filter in but not with a different filter by the same manufacturer, and I'll only be able to blurt out the obvious "maybe there is something wrong with the filter?"

Thursday, June 07, 2012

Pictures of the Venus Transit and Festivities

Sun setting behind Kitt Peak with transiting Venus
Venus transiting the sun as it sets behind the telescopes of Kitt Peak.  Image (c) 2012 David A Harvey, used with permission.
Tuesday afternoon, the planet Venus passed in front of the Sun as seen by the Earth.  (If you've been reading this blog, you already know that).  The next transit of Venus will happen on December 10-11, 2117 (my birthday, though I don't expect to see it).

Here at Texas A&M University - Commerce, we had an open house at our observatory.  Roughly 150 people came, which is absolutely amazing.  We had to fight some clouds - the transit started behind a thunderstorm, and the last hour that the sun was still up it was hidden behind clouds, and there were enough clouds we closed down early and didn't stay up to view the night sky.  But those who braved the heat and waited out the clouds were treated to quite the spectacle.

In case you missed the transit because of clouds, work, school, sleep or indifference, here are some pictures, both from us and from others.  Picture sources are indicated in the caption.  You may feel free to use any images labeled as being from NASA (here are their terms of use), and you may use any images labeled as from me as long as you attribute them and don't use them for commercial purposes (my terms of use).