Category: Astronomy

The Sky’s Dark Labyrinth – If you’re looking for a gripping summer read, check out my friend Stu Clark’s latest book: The Sky’s Dark Labyrinth. It’s part 1 of an intriguing trilogy concept that tells the tale of how God-driven scientists, such as Kepler and Galileo (yes, they were), unravelled the heavens while the Jesuits tried to retain world order by keeping the Earth biblically still.

German Lutheran Johannes Kepler is convinced that he has been given a vision by God when he becomes the first man to distill into mathematical laws how stars and planets move through the heavens. Galileo Galilei, an Italian Catholic, will try to claim Kepler’s success for his own Church, but he finds himself enmeshed in a web of intrigue originating from within the Vatican itself. Both men become trapped by human ignorance and irrational terror to the peril of their lives and those of their families…

Makes The Da Vinci Code look like a load of boring, old codswallop. This is real-life historical science in fiction.

There was an ugly rumour that the giant red star, Betelgeuse, that is the right shoulder (on the left as you look at it) of the constellation Orion is “about to” go supernova. The rumours seemed to have started earlier in the year when observations suggested that Betelgeuse had changed shape, a sure sign of imminent explosion. Phil Plait apparently debunked the claims on his BadAstronomy blog.

But what difference would it make to us if the star whose name is derived from the Arabic phrase “armpit of the white-belted sheep” were to explode? Could this be the worst case of Health and safety gone mad or a serious concern? Would we need sunglasses, tinfoil hat or simply resign ourselves to meeting ELE.

A physicist friend of mine suggested that Betelgeuse at (probably, about) 640 lightyears distance from earth is close enough that it going supernova would be an extinction-level event if there were a plume of gamma rays emitted in our direction. My son and his physics teacher disagree, suggesting that it’s too far away to cause anything but a bright light in the night, and perhaps daytime, sky.

Nathan Bergey was keen to point out that whether or not we should worry about a particular supernova really would depend on the distance, the type of supernova, and the direction of emissions. Wikipedia has its own interpretation, he pointed out and suggested that a 1 or 2 thousand parsecs (3000-6000 lightyears) might be a safe distance to be once the blue touchpaper were lit on any stellar neighbour.

According to a 2004 study, a gamma ray burst [from a supernova] at a distance of about 3,262 lightyears could destroy up to half of Earth’s ozone layer; the direct UV irradiation from the burst combined with additional solar UV radiation passing through the diminished ozone layer could then have potentially significant impacts on the food chain and potentially trigger a mass extinction. The authors estimate that one such burst might be expected every billion years or so.

My physicist friend points out that we could easily measure the neutrino flux from the 1987 supernova SN1987A, which is 170,000 lightyears away. Radiation intensity goes with distance squared so the radiation field from Betelgeuse would be 1000 times as intense as 1987A, “it would be fun, but probably not fatal,” he concedes. “A supernova at 50 lightyears would probably be more of an issue.”

One of the problems with supernova risk assessment is that we’re not entirely sure what lies between us and the putative fireball. If there are clouds of hydrogen and cosmic dust, then lethal gamma rays will tend to undergo Compton scattering at lower energies and form electron/positron pairs at higher enegies so the intesity will tend to dissipate as the rays travel through space.

In the 1950s, public information movies warned you to duck and cover when you saw the flash from a nuclear bomb. That was never going to save your skin, but nor was a tinfoil hat. Next time you’re musing on a starry, starry night just remember to keep a good pair of sunglasses handy alongside your telescope.

As a child I devoured books on the stars and planets, on dinosaurs, volcanoes. Was fascinated by the prospect of a space shuttle and lament the fact that I was sent to bed before they landed on the Moon (I was only three at the time, and the Apollo 11 landing happened at 2am UK time).

I was ever keen to hear about the latest research developments on TV from the likes of Tomorrow’s World and Horizon as well as the revelations about life from Attenborough (Sir David, not the bro, Richard). I was constructing all kinds of gadgets with Lego and Meccano from an early age and had an electronics kits at age ten and hankered after an astronomical telescope, a dream fulfilled the Christmas before my 11th birthday. My dad still reminds me that my most favoured word even before I started school was “mechanism”.

It’s no surprise that I went into a career in science and “grew up” to be a science writer is it? Equally unsurprising is that Gott and Vanderbei’s “Sizing up the Universe” quickly rekindled some long forgotten feelings about the universe in which we will. They present stunning visual comparisons of scale from Buzz Aldrin’s footprint on the Moon, to the gas giants that orbit our Sun to the swirling whirpool of stars that is the Milky Way and onwards and outwards to the Sloan Great Wall of galaxies and beyond stretching back to the cosmic microwave background of almost 14 billion years ago and 14 billion light years away.

The authors offer up the almost unimaginable vastness of the universe in this lavishly illustrated tome (plenty of beautiful Hubble space telescope images and much more, including backyard astronomical photography by Vanderbei). They say almost, but even after forty+ years of trying I personally cannot grasp the notion of the universe being a billion, billion, billion times bigger than that lunar footprint. Moreover, it’s not as if a billion, billion, billion is even a particular large number. Evidence suggests that the universe is a whole lot bigger than the limits of what we can see stretching back to the Big Bang, after all it has been expanding all that time. What’s more, if our universe is simply one bubble in a truly unimaginable froth of multiverses, then what now for “almost”?

You can order Gott and Vanderbei’s Sizing Up the Universe: The Cosmos in Perspective from Amazon, right now. Perfect for emergent science writers whose favourite words might include black hole, dinosaur, and even mechanism.

Ask a child how many stars they can see on a clear night, and the answer is likely to be some rather precise and yet strangely diffuse number like 200 and twenty-nine billion million thousand. An adult might suggest millions(?) with an inflection in their tone of voice to suggest that they are uncertain of that number and think it might be much higher.

Of course, the real answer is way, way lower. On a really clear night away from city lights and air pollution and with the best eyes in the world you would struggle to count just a couple of thousand visible to the naked eye. With a decent telescope you could see many more and, of course, there are literally (to paraphrase the late, great Carl Sagan) billions upon billions of the astral orbs in the universe as a whole. See “Ask a Scientist” on the ANL site where they suggest that there are 10 billion stars in the Milky Way and a possible 10 billion galaxies, which means 10 billion billion stars (that’s a 10 followed by 18 zeroes).

However, Sciencebase reader Luke McGuiness alerted me to an even more unimaginable estimate from Marcus Chown. In his book The Never-Ending Days of Being Dead, Chown suggests that there are 150 billion observable galaxies and probably about 500 billion in total in the universe, which puts the star count at 5000 billion billion, a few orders of magnitude higher than the ANL estimate. Although even more recent Hubble estimates suggest 300 billion stars per galaxy. So could be 150,000 billion billion stars…a number that’s starting sound like the kind of child’s exaggeration I mentioned earlier.

This brief post was inspired by a post on a futurology blog that suggested one might see millions and by a quick google that revealed the answer (Universe Today) I already thought of as being a couple of thousand. Across the globe their are probably about 6000 stars visible to the unaided eye.

More about stars and galaxies

• What’s eating the stars out of our galaxy’s heart? (newscientist.com)
• Distant Spiral Galaxy May Reveal Clues About Our Milky Way (space.com)
• Hubble snaps a cosmic photobomb (blogs.discovermagazine.com)
• Top 10 Summer Sky Objects to See Before Fall (space.com)
• What is a Galaxy, Anyway? (astrobasics.blogspot.com)

Latest scientific news with a spectroscopic angle

• Extraterrestrial molecules – An astronomical infrared study reveals one of the most complex organic molecules yet found in the interstellar medium – anthracene – offering possible new clues to the way the building blocks of life might have emerged.
• Wrinkles improve spectra – Polydimethylsiloxane can be used to produce wrinkles on a glass surface to pattern lines of gold which are twice as effective as conventional SERS substrates, according to German and Spanish researchers.
• Chemical communications – A new system for non-electronic communication that can transmit alphanumeric information encoded as pulses of light, over intervals of hours, without needing electricity and so remaining operational even without batteries in remote, hazardous or poor locations.
• Terrestrial life is plausible – A 2009 explanation for how the building blocks of life could have been activated now has new crystallographic evidence to support the emergence of the "RNA world" 4 billion years ago.
• Cheating spectroscopy – REDOR, a new form of NMR has been used by researchers in the US to figure out why the cheatgrass weed out-strips soy crops, particularly in higher carbon dioxide. Their results have serious implications for agriculture in the face of climate change.
• It is brain surgery, you know? – MRI scans allow surgeons to safely and effectively operate inside the human brain through small incisions in the natural creases of the eyelid rather than drilling through skull to get to the grey matter at the front of the brain.

Following on from yesterday’s summer book review, we go from inner space to outer space: Exploring the Solar System with Binoculars: A Beginner’s Guide to the Sun, Moon, and Planets by Stephen James O’Meara. Stephen James O’Meara shows you how to observe our Solar System’s wonders with ease, using nothing more than the unaided eye and inexpensive handheld binoculars. The guide presents a new way to identify and appreciate the wonders of the Solar System in detail, such as lunar and solar eclipses, sunspots, the Moon’s craters, the planets, meteors, and comets. Buy it on Amazon
A Question and Answer Guide to Astronomy, Bely Pierre-Yves, Christian Carol, Roy Jean-René. This book answers the fascinating questions that we have been asking ourselves for hundreds of years. Using non-technical language, the authors summarize current astronomical knowledge, taking care to include the important underlying scientific principles. Buy it on Amazon

Findings on Elasticity by Pars Foundation, Hester Aardse, and Astrid Baale. What happens when one gives a simple rubber band to an architect, historian, choreographer, chemist, artist, mathematician, physicist, economist, anthropologist, and geologist and asks each of them for a statement on elasticity? Buy it on Amazon

From gorillas, space, and elasticity to risk: How Risky Is It, Really?: Why Our Fears Don’t Always Match the Facts by David Ropeik. The author takes an in-depth look at our perceptions of risk and explains the hidden factors that make us unnecessarily afraid of relatively small threats and not afraid enough of some really big ones. Buy it on Amazon

Finally, the pyramids. The Great Pyramid Secret: Egypt’s Amazing Lost Mystery Science Returns by Margaret. The Great Pyramid Secret delves into the unsolved mysteries of ancient Egyptian engineering and presents many new and intriguing surprises but avoids the traps of sensationalism and dumbing down. It posits an alternative viewpoint that thankfully precludes the need for space aliens, Atlanteans, winged Egyptians or any other such popularist nonsense, to account for the outstanding engineering solutions found by the ancient Egyptians.

So, what is Morris’ answer? With several pieces of evidence and more than a nod to Davidovits, Morris suggests that the Egyptians made artificial rock that when mixed with aggregates, ‘forms concrete that has fooled geologists’ and that the stones of the pyramids were made from blocks produced on site.

The truly fascinating thing about books like this is that they’re truly incredible and no one can prove otherwise so that authors must repeat their message year in year out, perhaps with a string of books in the hope that someone will listen and their theory be accepted. It is, however, quite rare that paradigm shifts in thinking occur (even Einstein was no revolutionary, he simply spotted something that emerges from nineteenth century science and looks obvious in retrospect) and I suspect that we will not be rebuilding our ideas about the pyramids any time soon, despite this publication. Buy it on Amazon

Late addition – The Dark Matter Problem – by Robert H Sanders: Most astronomers and physicists now believe that the matter content of the Universe is dominated by dark matter: hypothetical particles which interact with normal matter primarily through the force of gravity. Though invisible to current direct detection methods, dark matter can explain a variety of astronomical observations. Sanders comments on the sociology of these developments, demonstrating how and why scientists work and interact.

Why does the full moon seem bigger when it’s near the horizon than when it’s high in the sky? The moon illusion, which also applies to the perception of the size of the sun in the sky, has intrigued artists and puzzled psychologists for many years.

The moon illusion refers to the fact that the sun and moon appear (to most people) to be a lot bigger when low on the horizon than when they are above us in the sky. Regardless of their position in the sky, however, the full moon and the sun both subtend an angle of about 0.5 degrees. There is no weird atmospheric refraction-magnification effect taking place.

That said, there is a slight variation in the angle subtended by the moon depending on its actual distance from the earth, and atmospheric refraction makes the moon’s image slightly smaller in its vertical axis when close to the horizon, giving it an oval appearance. These physical effects reduce the image size of the low moon by about 10%, and certainly cannot account for the perceived enlargement of about 150%.

To span the sky in a standard landscape photograph (35 mm lens in a conventional 35 mm camera) requires 100 full moons touching in a row. However, artists of all ages often represent a low-lying moon as being a lot bigger and sunrises and sunsets commonly show the sun as spanning a much bigger portion of a landscape than it actually does.

Examples of gross distortions of the sun or moon’s size in art can be found in Vincent van Gogh’s Sower with Setting Sun (ten times too big), Honore Daumier’s The Bluestocking (four times), Samuel Palmer’s Coming from Evening Church (five times), Ernest Briggs’ The Northern Twilight — Returning from the Fishing (four times).

There are many explanations of the moon illusion, but none are entirely satisfactory. Among them is the notion that we perceive the sky as a flattened dome so that the horizon is from our internal perspective farther away than the zenith above, and so an object lying near the horizon appears bigger because it is scaled for distance. Think of it this way, scattered clouds across the sky give the odd impression of a gently curving sky as we look above us and then towards the horizon. It’s perhaps all about cues to distance, which in a sky are few and far between.

The problem with this explanation is that, given that perception, the moon should appear bigger but farther at the horizon, but to most people it doesn’t – it appears bigger and closer. Experiments show that the apparent enlargement of the moon’s diameter varies between about 1.3 and 1.8, with 1.5 being typical of most people’s perception.

Helen Ross of the Department of Psychology, at the University of Stirling, Scotland, and Adele Cowie have tested children aged 4 to 12 years and adults aged about 21 years by asking them to draw the apparent size of the moon on a photocopy of a landscape, both near the horizon and high in the sky. The mean ratio of the low to high moons was 1.57, and the size of the illusion did not vary significantly with age. “The illusion, like size-constancy in the near distance, is well established by age 4,” the authors say. Indeed, the illusion is present in full strength in young children, so cannot depend on perceptual skills that develop later in life, Ross says.

Writing in the International Journal of Arts and Technology, Ross and Cowie
explain this perceptual paradox:

At near distances, spatial perception is governed by non- pictorial cues such as motion parallax, convergence, accommodation and stereopsis; at far distances, it is governed by pictorial cues such as image size, linear perspective and texture gradients. At near distances, constancy is automatic and it is very hard to distinguish between angular size (retinal image size) and true object size. At far distances constancy is imperfect, and distant objects appear small; but with experience we can learn to estimate the true size of objects, by taking account of distance and other cues.

The authors suggest that the moon illusion may be similar to those geometrical illusions that show no clear age trends, and to size-constancy at near distances. Both effects are observed in young children, and this would imply that the moon illusion is caused by low-level automatic processes in the brain rather than by some sophisticated mental acrobatics that allow us to scale for distance, a function that improves with age. “If observers [of all ages] are not scaling the moon by its apparent distance, but by other factors, then the apparent distance is irrelevant,” the authors say. The sight of the terrain is the most important factor. It may be that size is scaled in relation to other sizes in the scene, or perhaps the terrain is a cue to orientation.

Experiments show that tilting one’s head or bending over and looking at the moon through one’s legs reduces the illusion. Our perception changes depending on the angle at which we look at something relative to the local terrain. It seems there really is no single satisfactory answer to the illusion, but instead it is caused by a combination of factors.

One final thought for fans of the new moon, as opposed to the full moon. When the new moon is “cradling the old moon in its arms” one can see the sun’s light faintly reflected from the earth, earthshine, on the region of the moon that is facing away from the sun itself and so otherwise dark. The partial disc of the moon illuminated by earthshine appears slightly smaller than the extrapolated circle of the moon’s “arms” would suggest it should be. This is not entirely apparent in a photograph but is easily seen with the naked eye. This shows how yet another factor, brightness, affects the apparent size of the moon.

Helen E. Ross, & Adele Cowie (2010). The moon illusion in children’s drawings Int. J. Arts and Technology, 3 (2/3), 275-287

Outside the tropics we experience four seasons – Spring, Summer, Autumn, or Fall, and Winter. These occur because the Earth’s axis about which it rotates once a day is tilted at an angle relative to the Earth’s orbit around the sun. Because the axis always points towards the north star throughout the year, the seasons are cyclical. In the northern hemisphere, when the North Pole points towards the sun, the sun’s light is more directly overhead at mid-day and the sun is in the sky for longer; it is summer. At this time the opposite is true in the Southern hemisphere.

Spring and Autumn are the half-way points when the Earth’s tilt is neither angled towards or away from the sun. These seasons usually have milder temperatures than the extremes of winter and summer. The difference between spring and autumn is essentially one of biology as the organisms experience warming day after day in Spring and respond accordingly and cooling day after day in Autumn.

So, all that in hand, it must have been quite confusing for viewers of the BBC’s latest scientific blockbuster “The Wonders of the Solar System” to watch the earth wobbling like a spinning top as it orbited the sun and learning that this change is the cause of the seasons. Actually, the way they showed it, the Earth was static and the sun was orbiting it.

Now, the producers were actually using the 3D graphics to show the relative position of the tilt of the Earth’s axis to the “fixed” sun. Whereas what they showed did resemble astronomical precession (which does not cause the seasons). Precession is the regular oscillation of the axis of any spinning object whether gyroscope or planet, that occurs as the object rotates.

Precession will be familiar to anyone who has played with a child’s spinning top or a gyroscope (a spinning top for grown ups). The main axial oscillation is slower than the spinning but is quite visible. For the much bigger Earth, spinning on its axis once a day, the oscillation of that axis is much slower. The main large precession of the Earth’s axis takes tens of thousand years to complete a single loop.

Despite precession being a long timescale feature of the Earth, it has a number of observable effects, if you’re willing to wait. First, the positions of the south and north celestial poles appear to move in circles against the space-fixed backdrop of stars, completing one circuit in 25,771.5 years (measured at the year 2000 rate). So, the north star, Polaris, today lies approximately at the north celestial pole, this will change over time, and other stars will become the “north star”, today’s north star was not the north star seen by the earliest human navigators thousands of years ago. It also provides a point of confusion for historians looking at ancient star charts and scientists must take it into account in climate studies, for instance.

I modified this post after Brian Cox commented. I *did* understand what they were showing and what they were trying to show. But, I and others, felt the imagery might have been somewhat confusing for the average viewer.