My Nerdy Friend

On a recent trip to Maui my family and I found ourselves at the Maui Ocean Center. (Actually, I tend to turn up at the local aquarium of any city I’m visiting that has one – one of these days I really should start doing aquarium reviews!) In the humble opinion of both my son and me, the best part of this particular aquarium was the hammerhead shark tank. Hammerheads are one of those creatures that seem to make no sense at all, something that you might think was a practical joke if you didn’t see them actually swimming around (“hey, let’s send another fake skeleton over to Byron in oceanography, we had such fun with that jack-a-lope!”)

The strangeness of the hammerheads got me to wondering how on earth something so unusual and awkward-looking would evolve? What was it that lead to the evolution of  eye sockets bulging out on either side of its head like a … well … like a hammer?

Initially I was wondered why the hammer evolved in this one case and not in any others. Well, as it turns out, there are actually several different species of hammerhead shark – eight or nine of them, to be inexact (the sources that I researched seem to vary on this point). And multiple species suggests that this evolutionary branch is not quite as rare as I thought. It is still uncommon, however, as there are 440 or so species of shark. So just why did the hammerhead evolve?

As it turns out, not much is known for certain with regard to its evolution. Only very recently have scientists determined with a fair degree of certainty and agreement that the hammerhead evolved its peculiar head shape to enhance its vision, probably to aid in the search for prey. The wide eye position gives the shark two distinct benefits – good binocular vision and full 360 degree vision vertically. The 360-degree vision in a vertical plane simply means the shark is able to see above and below itself at all times. Binocular vision has 4 beneficial characteristics: one eye can act as a spare in case the other is damaged, the two eyes give a greater field of view when the field of view of each individual eye is combined together, it enhances the ability to detect faint objects because the vision in each eye adds together, and it enables depth perception (via parallax) which in turn enables more accurate jugdement of distance.

I couldn’t, unfortunately, find anything to suggest why it was a beneficial adaptation for the hammerhead to be equipped with binocular vision when so many other shark species lack it. There are a few different theories for this, including some that I basically just made up. Maybe you can think of a few more?

1. If hammerheads tend to live in murkier water, then better vision would help them locate prey (this is one I made up!)
2. As a smaller species of shark, better vision might also help them see predators more readily (an actual theory)
3. It could be that ancestors of hammerhead sharks were isolated from other shark species in some way and underwent a dramatic evolution in response to stresses in their environment that other related shark colonies did not face.

With more study, we may one day have some good theories as to why hammerheads evolved in this way. Sadly, hammerhead sharks, like most shark species today, are endangered in many areas. The decline of sharks in our lifetime is startling and shocking (the scalloped hammerhead population has declined by 99% just in our lifetime). Most of this decline is due to overfishing, particularly in Asian markets where sharks are sold for their fins which are made into shark fin soup. This conflict of culture and ecosystem is something that needs to be resolved if we hope to protect sharks from extinction.

A friend of mine wrote to tell me of a phenomenon that she and her husband witnessed – an enormous white foggy ring around the moon. If you do happen to see it, this ring around the moon is an awesome sight.

The ring around the Moon, or lunar halo, is caused by the refraction, or bending, of moonlight as it passes through ice crystals in high-altitude cirrus or cirrostatus clouds in the upper atmosphere. Light from the moon, or more specifically, sunlight reflected off the surface of the moon, passes through ice crystals causing the light rays to bend. The ice crystals are shaped like hexagons, much like snowflakes, which means the light will bend in exactly the same way around the moon, and since the moon is round, this results in a perfectly circular ring.

This effect can actually be explained through math. Because of their hexagonal shape, the ice crystals act like 60 degree prisms, which cause light to be bent at about 22 degrees. Since the light is coming from a single object (the moon), it bends in all directions to form a circle with is 22 degrees in radius, or 44 degrees in diameter. The moon itself is about a 1/2 degree wide as we see it in the sky, meaning lunar halos are about 80-90 times large than the diameter of the moon!

The “prism effect” of the ice crystals is interesting in another way as well. If you look very closely at a lunar halo, you may notice that the light has separated into its various component colours, meaning that the halo itself is, in fact, a rainbow! Red light bends more than blue light, so you may see a redish tinge on the inside edge of the ring, transitioning to blue on the outside edge.

The appearance of lunar rings is not particulary common, and is often overlooked becuase of the sheer size of the ring. According to folklore, a ring around the moon was a harbinger of bad weather to come. While not typically very “sciencey”, there may be some truth to this. Since the halo forms when high altitude cirrus clouds are present, and these clouds typically precede a warm front which can be associated with a low pressure system bringing stormy weather. It’s always fascinating to realize that our ancient ancestors may have been able to piece together a pattern from observatsion of the moon that turns out to have a basis in fact!

Astronomers recently announced that they had the discovered the oldest/farthest known galaxy …. it is 13.2 Billion light years away. This is awesome for a number of reasons.

First on the awesome list is how it was detected. To “see” this galaxy, astonomers used a combination of two factors; one related to an interesting characteristic of galaxies and one related to a feature of the expansion of the universe.

Stars inside galaxies can produce Ultraviolet (UV) light that reacts with hydrogen gas. This means that if light from a distant galaxy passes through a cloud of hydrogen gas on its way to us here on earth, then the UV light emitted by the galaxy will be absorbed by the gas. However, other colours (or wavelengths) of light will pass through the gas undisturbed. To see this effect, all you have to do is look at the galaxy through a variety of coloured filters from red to green to blue and on to UV. The galaxy will appear in red, green and blue filters, but will disappear in, or drop out of, the UV filter since the UV light has been absorbed already by the hydrogen cloud. It’s an easy trick to detect galaxies, which scientists have cleverly dubbed the “dropout technique”.

So now that we know it’s a galaxy, how do we know how far away it is? It turns out the expansion of the universe can lend a hand here. As the universe expands, it carries galaxies along with it, and the movement of galaxies away from us causes the wavelength of the light we see from those galaxies to stretch out and become longer, shifting the light towards the red end of the light spectrum (the “rainbow” is the full visible light spectrum) since red light has a longer wavelength than other visible light. This effect is called “redshift”, and it to light what the doppler effect is to sound. The doppler effect causes sound waves to stretch as an object moves away from us, causing a corresponding drop in the frequency of the sound we hear, an effect we hear when emergency response vehicles pass us and we hear their sirens drop in pitch. The further away a galaxy is, the more its light is redshifted, and if Astronomers know how much the redshift is, they can then calculate this distance.

Putting the two pieces together, Astronomers realized that their new galaxy should drop out of UV filters, but also the light would have been redshifted so the dropout would actually occur at some wavelength shifted away from UV and toward red. If they could figure out the wavelength of the dropout, they would know the redshift and could calculate the galaxy’s distance. This turned out to be a really simple thing to do. Just observe the galaxy through different filters and figure out which on results in the dropout effect! After doing just that, Astronomers were able to calculate the distance of the galaxy as 13.2 Billion light years.

Another reason why this is awesome has to do with what we are really seeing. The universe itself is estimated to be about 13.7 billion years old, so by detecting this new galaxy, we are not only looking as far away as we’ve ever seen before, we are also seeing light that is 13.2 billion years old. To put that in reverse, we are seeing light that was forms when when the universe was only half a billion years old. This is extremely young in universe-years, and this early look should help further our understanding of how the universe came to be, and what its nature is.