Happy New Year!

The New Moon of Monday, September 29, is an important one to many people of the world. In the Hebrew Calendar, it marks Rosh Hashanah (literally, ‘head of the year’) which is the beginning of year 5769. On Tuesday night, September 30, Muslims across the world will see the first slender crescent of this lunar cycle. That will mark the end of Ramadan and the beginning of the next month, Shawwal. 1 Shawwal is ‘Eid ul Fitr, one of the greatest holidays in the Islamic calendar. This week, then, is a good time to think about the Moon, why it’s here, how it orbits, and how we have used it to measure time.

Moon and stars
Creative Commons License photo credit: joiseyshowaa

Unlike our months, Hebrew and Islamic months begin with the New Moon. Because twelve lunar months add to only 354 days, less than the 365.25 day solar year, an extra month is occasionally needed to keep the months roughly aligned with the seasons. In a 19 year cycle, years 3, 6, 8, 11, 14, 17, and 19 have the extra month. The year that is ending, 5678, is number 11 in its cycle and was a leap year.

Interestingly, the Jewish year has two ‘beginnings’. Tishrei (the month which begins now) is the first month of the civil calendar, and the month where 5678 becomes 5679. However, it is actually the seventh month of the religious calendar, which begins at Nisan (the month of Passover).

The Islamic calendar functions slightly differently. Its months begin with the first visible crescent low in the west at dusk, which is not with the actual New Moon. Keep in mind that at New Moon, the Moon is in line with the Earth and Sun, and the entire near side of the Moon has nighttime (and is therefore dark). The New Moon is visible, therefore, only if it blocks the Sun during an eclipse.

Since this New Moon occurs early Monday morning, the 29th, we expect it to be visible by Tuesday evening, the 30th. Observant Muslims, then, will continue to fast in daylight hours Monday and Tuesday. Upon seeing the Moon Tuesday night, they will know that Ramadan has become Shawwal, and they may break their fast on Wednesday.

Due to early controversy as to which years would have it, Muhammad outlawed the 13th month that kept Islamic months tied to the seasons. As a result, Ramadan (and each other month in that calendar) begins 11 days earlier each year according to our Gregorian calendar.

The Moon is Earth’s only natural satellite, orbiting our planet once every 27.3 days. However, a cycle of moon phases (say, from New Moon to the next New Moon), takes 29.54 days. This is because the Earth itself is moving during each 27.3 day Moon orbit. Since it is much easier to observe the Moon’s changing phase cycle than to observe the Sun directly, the 29.54 day phase cycle was the basis of many ancient calendars. Words for ‘moon’ and ‘month’ are related in English and are identical in many other languages. There is some evidence that our word ‘moon’ is ultimately related to an Indo-European word for ‘measure.’ Given how long we’ve measured time by the Moon, it is easy to take its presence for granted.

Released to Public: Jupiter Montage (NASA)
Creative Commons License photo credit: pingnews.com

However, our Moon is quite remarkable in several ways. Moons in our solar system are generally much smaller than the planet they orbit. Jupiter and Saturn, for example, are about 25 times bigger across than their biggest moons. Earth, though, is only 3.67 times the diameter of our Moon. Also, moons usually orbit in the same plane as their planet’s equator. Our Moon, though, orbits within about 5 degrees of Earth’s orbital plane, called the ecliptic, which is not the plane of the equator since Earth is tilted 23.5 degrees on its axis.

This leads most astronomers to believe that the Moon did not form with the Earth, but is the result of a collision with with an object roughly the size of Mars. According to this theory, the impactor (sometimes called ‘Theia’) struck a glancing blow on the Earth and was completely destroyed, and the Moon formed from the debris of Theia’s and Earth’s mantles.

This impact is what left Earth with a Moon much larger than what a planet Earth’s size would normally have, and left that Moon near Earth’s orbital plane (where the impact occured). Our relatively big moon has crucial effects not only on our tides, but also on the stability of Earth’s tilt.

Earth’s orbital tilt of about 23 and a half degrees as it goes around the Sun causes the seasons. The axis precesses, describing an aparent circle roughly every 26,000 years, but the amount of tilt (obliquity) stays nearly the same. Because the Moon acts a counterweight, the obliquity varies only between 22.1 degrees and 24.5 degrees over about 41,00 years (we are now at 23.44 degrees and decreasing). Even this orderly variation, called the Milankovitch cycle, is enough to influence our Ice Ages. Imagine the impact on Earth’s climate if there were no Moon, and the obliquity varied chaotically. This is exactly what happens at Mars, where the tiny moons Phobos and Deimos are not massive enough to influence Mars’ tilt.

Public Domain: Apollo 8 Looks at the Moon (NARA/NASA)
Creative Commons License photo credit: pingnews.com

One thing our Moon does have in common with most others is that it orbits the Earth and rotates on its own axis at the same rate. This is called ‘synchronous rotation’ and it occurs because the Moon is not exactly uniform in composition. From the time the Moon formed, the slightly heavier side was attracted to the Earth. Over time, this effect de-spun the Moon until it attained synchronous rotation. The Moon’s gravitational attraction also de-spins the Earth, although much more slowly as the Moon is less massive. As it does so, the Moon moves slightly farther from the Earth (just over 3 cm per year). The Moon is now 1.5 meters farther away that it was when Apollo astronauts went there. Don’t worry, though, by the time the Moon is far enough away to escape, the Sun will have become a red giant and swallowed both Earth and Moon anyway.

What is the shape of the Moon’s trajectory around the Sun? Perhaps not what you’d expect.

So, I encourage every one to watch for the reappearance of the Moon in the evening sky this week, even if you aren’t celebrating a New Year or an ‘Eid. The Earth’s companion gives all of us something to appreciate.

Draw Dinos Right!

Someone asked me: What are you?  Science Guy or Artist?

Both.

Leonardo da Vinci said: “I don’t understand a thing ‘till I draw it.” When you draw, your finger tips teach your brain what’s important.

Cleaning Bones & Feeling Dinosaur Muscles

Most fossil-cleaners are good artists.  As they chip away the rock, their finger tips record each bump and hole, every place that’s smooth, every place that’s rough. Expert fossil-cleaners dream about the fossil – they see it rotating, turning every which way.

Let’s say we have an ankylosaur skeleton, fresh from the field. We clean off the rock slowly. Every time we have a square inch clean, we paint thin glue on it (so it doesn’t crack and fall apart). As we do, we make sketches of the bone. That helps plan the complete cleaning. It’s X-ray vision, sort of.  As we sketch the bone we can draw in the parts of the specimen that are still buried in the rock.

For instance: let’s say we have the upper left arm (humerus). And we have the elbow end cleaned, but the shoulder end is still in the rock. A sketch will help us imagine where the bone is and how to chip the rock off so we don’t break anything accidentally.

Putting Muscles and Ligaments Back On

Fossils from a Dimetrodon hip bone.

Texture of fossil bone is important:

Rough spots full of squiggly ridges are where tough ligaments and tendons attached to the bone.

Smooth spots are where soft muscle attached.

Bones with big pits are armor plate – in life the pits were filled with a thick layer of finger-nail like skin.

At the Zoo with Brachylophosaurus

Now let’s shift to Leonardo, the Brachylophosaurus,  the dino-mummy now visiting the Houston Museum of Natural Science. I wanted some drawings of the critter, and to prepare I spent a lot of time watching live animals.

I sketch live critters in the zoo all the time.  And I make diagrams of the heads, bodies and legs of skeletons from species that are still alive today. I can’t imagine a live Brachylophosaurus  or any other dinosaur without studying rhinos and elephants,  ostriches and cassowaries, giant tortoises and water buffalo.

Tweensy Gator Hands

Most plant-eating dinos have hands like the one in the little vegetarian dinosaur Hypsilophodon.  There were five fingers in this animal and most other herbivores. Carnivores sometimes have  three, as in Velociraptor,  or two as in T. rex  and all members of the rex family.  In all dinos, meat-eater and plant-eater,  only the inner three fingers had claws. In herbivores the claws are blunt and hoof-like. Carnivores tend to have sharp-tipped claws. In all dinos, the outer two fingers had no claws at all.

The five fingers/three claws is standard equipment for most ancestors of dinos too.

Gator
Creative Commons License photo credit: James Jordan

Who has this  five/three  hand in a zoo today?  Only in one clan – gators and crocs. Lizards and turtles have claws on all five fingers.  Crocs & gators have three claws, five fingers, no claw on outer two. Watch out when you draw dino hands – a lot of books make the mistake of giving a dino  four or five claws. Even the movie “Jurassic Park” makes that error with the Triceratops. Don’t YOU do it! Remember: five fingers but only three claws in most plant-eating dinosaurs.




No Bowling for Duck-Bills

Duck-bill dinos have a puzzling variation on the basic veggie-saur hand. The outer two fingers are fine – no claw or hoof. But there are only four fingers in total. Which is missing? The thumb. Duck-bills are the only dinos without any thumb. That’s strange because the thumb is usually one of the strongest fingers in all other dinosaurs. Even T. rex  has a thumb. There’s a predatory dino with just one finger – Mononychus – and that single finger is, you guessed it, the thumb.

One result of being thumb-less is that when you’re choosing a bowling team, you don’t want a duck-bill. They can’t hold the ball. Continue reading

Rodents use tools to gather food

Our degu as a juvenile

Our degu as a juvenile

We have two adorable Degus (Octodon degus) in our collection.  These intelligent rodents are from Chile, but have recently become more popular in the pet trade.  They have become a wonderful addtion to our educational programs as not many people have heard of them.  As it turns out, they are also my personal favorite (we each have favorites, even though we try not to!)

Degus have also been used in medical research for diabetes, sleep patterns, & most recently, their ability to use tools! Before purchasing any new animal, we do a lot of research to make sure that they will be a good fit for our programs.  With that said, we knew that our new furry friends would be smart, energetic, and try to chew through anything.  We were prepared, but after reading articles on how degus were able to use a rake to gather food, we were impressed! Check it out:

Game Day: Moving a 6-ton fossil

Last week a colleague commented in her post on this blog that she’s ridiculously excited about the debut of Leonardo. The entire Houston Museum of Natural Science team echoes her sentiments.

It’s been a challenging couple of weeks since Ike’s wrath came upon our city. The museum was closed to the public for about five days due to the storm’s aftermath.  We were left without power; therefore, the opening date of Dinosaur Mummy CSI: Cretaceous Science Investigation was delayed until Sept. 26 (originally scheduled to open Sept.19).

Now we’re up and running and it’s only 23 hrs. and about 10 minutes until visitors are able to see Leonardo on display. It took a lot to get him here—a special palette; a very heavy fork lift; an air cushioned tractor trailer; a crane; along with our very own dynamic paleontology staff and outstanding support from supreme moving specialists. As Dr. Bakker says, “Moving a fossil is like moving a piece of art.”

In this video, we thought we would give you a rare peek of what David Temple calls “Game Day,”— moving Leonardo, a 77 million-year-old adult duckbilled dinosaur, from our off-site facility to the museum.

Check out the other videos in this series:
The mummified dinosaur Leonardo: too good to be true?
Mapping a dinosaur with Dr. Robert Bakker.
First in a paleontologist’s toolkit: glue.
Or, check out our channel on YouTube for even more video.