Sports Science: Football

The fourth Thursday in November is the perfect time to spend time with family, eat some home-cooked comfort food, and watch grown men throw around an inflated pig bladder.

That’s right, folks; the world’s first American football was actually an inflated pig bladder, hence the nickname “pigskin.” Don’t worry, modern footballs are made of leather or vulcanized rubber, but the shape of a football remains the same as it’s ever been, lending itself to an interesting discussion of physics.

My sophomore year of college at Washington University in St. Louis, my physics professor’s lecture the week of Thanksgiving featured two balls, a red rubber kickball and an American football. She asked us to predict how the balls would bounce. The spherical kickball was easy; the American football was not.

Football shape

The ovoid shape combined with the two sharp points at each end mean that the ball can bounce in just about any direction at any angle depending on its orientation as it is falling and what part of the football makes contact with the ground. That’s why every football coach I ever had drilled us on just falling on the ball instead of trying to catch it or scoop it up; it is extraordinarily difficult to predict just which way the ball will bounce! These bounces often manifest on plays when a bouncing ball is live, like a fumble, an onside kick or following a punt.

As the game evolved, so did the football itself. As you can imagine, inflating animal bladders can be inconsistent; now, the NFL football is standardized at about 11 inches long from tip to tip and a circumference of about 28 inches around the center. Those bladders could also be difficult to grip, so the modern football has a coarse, pebbled texture as well as white laces in the center.



Because of its shape, the football cuts through the air most easily when spinning around its longest axis, called a spiral. This spiral minimizes air resistance and allows the ball to move in a more predictable parabolic motion.

A common misconception is that the spiral motion allows the ball to travel farther, but this idea falls apart with basic physics. When a ball is initially thrown, there is a set quantity of total energy in the system. That set amount cannot be increased or decreased, just changed from one form to another according to the Law of Conservation of Energy. The spinning motion of a football in the air requires kinetic energy, so every Joule of kinetic energy required to keep the ball spinning is less energy dedicated to the football’s motion.

Instead, the spiral is important because of a concept called angular momentum. A spinning football behaves like a gyroscope; a ball will maintain roughly the same orientation while travelling. This makes the football’s movement from point to point easier to track and predict for a player.step0So when tossing around the ol’ pigskin Thanksgiving Day, make sure you grip the ball with the laces as you throw! What works best for me is to put my middle finger, ring finger and pinkie finger on alternating laces at the front of the ball (as pictured above).

When throwing a football, it is important to generate the force for the ball from your legs. If you are right-handed like me, stand sideways with your right leg behind you. Push off against the ground with your back leg and turn your body to throw as you do so. Bring the football backwards and then forwards over your shoulder, allowing the ball to roll off of your fingers straight. No need for any wrist twisting, as the ball should naturally move in a spiral. (See proper form below.)step1Step one: feet shoulder width apart, hands meet on the ball.step2Step two: weight on your back foot, bring the ball back, wrist out.step3

Step three: throw the ball, wrist in. Allow the ball to roll off of your fingers, but keep your wrist straight and stable. Release the ball over your shoulder. Remember, it’s not a baseball. step4Step four: follow through after the release.

Whether you’re facing the New Orleans Saints or the neighbors across the street, the principles of physics are crucial to your football team coming out on top. May the forces be with you! Happy Thanksgiving!

Holiday How-to: Chocolate Leaves

My mom was a chemistry and home-ec teacher, so I grew up in a home where ingredients were carefully measured and food items were attractively arranged. While I got to help out in the kitchen as much as I wanted, I always liked being in the kitchen around the holidays. There were always new tricks or special touches added to dishes and along with these came short science lessons on why we were doing things that particular way.

One of my favorite things to help with in the kitchen were chocolate leaves. When done correctly, these are perfect little molds of the living leaf, just like the perfect molds and casts in the Morian Hall of Paleontology.

A chocolate leaf is made by smearing melted chocolate onto a leaf and putting it into the fridge to harden. Sounds easy, right? It is pretty easy. Read on!


Activity: Chocolate Leaves


Leaves (*See note in step 1.)

Chocolate candy melts

Parchment or wax paper

A cookie sheet or plate for your leaves to rest on as they cool


1. Pick your leaves. I like to use slightly waxy leaves so you don’t have to worry about fuzzy bits in your chocolate. NOTE: Learn about the plant you are picking leaves from before you decide to use them. Many household plants are decorative but poisonous.  Oleander is a great example of a plant that is pretty but poisonous. If you hate botany or don’t know about the Internet, getting pre-packaged basil or mint from the grocery store is a safe way to go. These leaves will be a little less firm, so you will need to be more careful with them.

2. Don’t pick leaves from poisonous plants. Seriously.

3. Wash your leaves with soap and water, rinse them thoroughly and then dry them completely. The chocolate won’t stick to wet leaves, so don’t rush this step. You will only be frustrated.

4. Put wax or parchment paper on a cookie sheet or plate. You want this to be something that will fit in the fridge with no problems.

5. Get out your candy melts. The melts come in a hundred colors. We are using chocolate colored ones in this tutorial. There will be instructions on the package on how to melt the specific brand of melts you purchased. In general, you will put the melts in a microwave safe bowl and microwave them a few seconds at a time stirring as you go. Don’t overheat the melts. They get gross and there is no coming back from that.

6. When you have everything melted and creamy, hold the leaf by its stem. I like pinching it between my thumb and index finger and then using my middle and ring finger to support the leaf. Do what feels comfortable to you.

7. Dip your stirring spoon into the chocolate. Use the BACK of the spoon to spread the chocolate on the leaf. Make sure the chocolate is thick enough that it won’t break when you try to peel it. Place the leaves on the parchment as you work, and don’t let them touch.


8. The side of the leaf you use is up to you. If you are using mint and you put the chocolate on the back of the leaf, you will have some crazy patterns.  If you want something more subtle, use the front of the leaf. Coat the leaf almost to the edges. If you go too far, you will get ugly edges that are hard to peel. But don’t worry! Those leaves are the best to eat.

9. Put the tray of leaves in the fridge and wait a few minutes.


10. When the chocolate is set, peel the leave off the chocolate. You should have a perfect little mold of your original leaf. This may take a little practice. Work quickly as you have something designed to melt with heat in your hot little hands.

11. Done! You can store the leaves in the fridge until you are ready to use them. If the leaves got soft when you were working with them, put them back in the fridge to firm them up. Once they are firm, you can toss them in a plastic container.


Okay! So what’s the science here?

The word “chocolate” comes from the Nahuatl word Xocolatl for “bitter water,” referring to its original incarnation as a hot, spiced beverage in the Mayan and Aztec traditions. Traditionally, chocolate is a mixture of cacao powder, cocoa butter, and a sweetener. To make chocolate palatable and stable, we now mix milk solids, added flavors, modifiers, and preservatives.

Those candy melts? NOT CHOCOLATE! In this example, they are sort of chocolate colored, so they have that going for them, but they also come in a bunch of colors that are not known to nature so… not chocolate. They are mostly made of sugar and vegetable fats – not cocoa butter – and depending on the brand, they may throw in a little wax for better melting. Mmmmm… wax.

The advantage to the melts over the regular chocolate is that they do have the wax and the vegetable oil in them, which makes melting easier since the chocolate doesn’t need to be tempered. It hardens pretty quickly and sticks to whatever you dip in it, so it makes a great coating for cake pops or whatever crazy things show up on Pinterest this month.

Want to get super nerdy about your chocolate?  (I assume you do…) MIT has these tidbits available.

What’s in typical chocolate?

  • 10-20% cacao
  • 8-16% milk solids
  • 32-60% sugar
  • 10-20% cocoa butter
  • 2% theobromine and polyphenols

Cocoa Butter Chemistry

Fats and oils are organic molecules made up of three fatty acids chemically linked by an ester bond to glycerol. Fats are solid at room temperature, while oils are liquid.

Cocoa butter fats are made up predominantly by three major fatty acid molecules: Palmitic Acid, Stearic acid, and Oleic acid.

Oleic acid is unsaturated (has a double bond on its carbon chain), making it kinked and unable to pack well with other molecules. Because of this, a greater portion of oleic acid in the fat results in a lower melting temperature for the cocoa butter.

Chocolate makers can adjust the amounts of each fatty acid to produce a chocolate that melts only in the mouth, giving it a superior quality.

Tempering chocolate

The cocoa butter in chocolate can have several different crystal structures (three-dimensional patterns in which the fat molecules pack). There are six known chocolate crystal forms, or polymorphs. You can obtain each form by varying the fatty acid ratios and the temperature at which the chocolate is tempered (cooled).

Only a few of the polymorphs are considered good for gourmet chocolate because they give the right blend of snap (when you bite into the chocolate) and melting (when it warms up in your mouth). Melting is especially important because it controls how well the chocolate disperses and releases flavor onto your tongue.

Whether you will be constructing culinary masterpieces this fall or sitting back and enjoying the kitchen creations of others, we hope you have a happy holiday with you and yours!  (And when you’ve had a little too much togetherness, we will be open on Friday…)

Mark Your Calendars for these events happening at HMNS 11/16-11/22

Bust out your planners, calendars, and PDAs (if you are throwback like that), it’s time to mark your calendars for the HMNS events of this week! 

Jingle Tree 3

Film Screening – The Northern Lights: Nature’s Spectacle with Pal Brekke
Monday, Nov. 16
7:00 p.m.
Imagine what it must have been like for the first northern inhabitants to raise their eyes to the dazzle of the Northern Lights. The Aurora Borealis still casts its mysterious and colorful spell over us, and Norwegian solar physicist Dr. Pal Brekke has captured that enduring fascination in a new documentary, The Northern Lights: A Magic Experience.

Sip ‘n See Open House & Luncheon
Tuesday, Nov 17. 
11:30 a.m. – 1:30 p.m.
HMNS at Sugar Land
Next up is our open house Sip n See, Tuesday, November 17, from 11:30 am to 1:30 pm. This fabulous strolling lunch event will allow you, your friends and associates to see the trees up close and perhaps even “pre-buy” the one you fall in love with!

Lecture – Fire Masters: Cooking and Feasting 10,000 Years Ago by Andrew McCarthy
Tuesday, Nov. 17
6:30 p.m.
The food we eat and its preparation define us as humans as few things do. Archaeologists theorize that cooking and feasting enabled the human brain to expand. Excavations on Cyprus reveal the presence of large stone ovens much larger than a single tribe required, apparently for the purpose of sharing feasts in the Neolithic period dating to 10,000 years ago. Dr. Andrew McCarthy will explore how cooking and feasting may be decisive steps toward the development of civilization. Perhaps the origin of our holiday feasts is result of humankind³ greatest prehistoric inventions.

Drink and be Merry Happy Hour and Auction Closing
Thursday, Nov. 19
5:30 – 8:30 p.m.
HMNS at Sugar Land
We’ll wrap things up with a cool Happy Hour, Thursday, November 19, an evening filled with cocktails, tree viewing, on-line bidding and a fabulous live auction. All bids close that evening at 8:00 pm!

Class – Atlatl Workshop: Stone Age Spear Slinging
Saturday, Nov. 21
9:00 a.m.
Journey into prehistory by literally chucking the past! Experimental archaeologist Dr. August Costa will introduce you to the science and prehistory of hand-cast projectiles and biomechanics of their use. Participants will build their own cane dart and learn how construct throwers. After instruction on using the Stone Age spear-throwe–the atlatl, participants will fling full-scale replicas at stationary targets. The class will culminate in a tournament competition, with a sharp grand prize.

Mark Your Calendars for these events happening at HMNS 11/9-11/15

Bust out your planners, calendars, and PDAs (if you are throwback like that), it’s time to mark your calendars for the HMNS events of this week! 


Lecture – The Fastest Evolving Regions of the Human Genome by Katherine Pollard
Wednesday, Nov. 11
6:30 p.m. 
Although a child can tell the difference between a chimp and a man, identifying the specific DNA mutations that make us human is one of the greatest challenges of biology. The genomic sequence is approximately 3 billion letters long, with millions of mutations and rearrangements specific to humans. Using computational algorithms to compare our DNA to that of chimpanzees, other mammals, and Neanderthal and Denisovan fossils, we learned that the human genome did not evolve especially fast. Instead, it seems that a few mutations in critical places had big effects. Most of these “Human Accelerated Regions” are not genes, and science has no clue to their function when they were discovered a decade ago. New techniques in stem cell biology, genome editing, and high-throughput molecular biology are allowing us to discover the functions of the fastest evolving regions of the human genome and dissect how individual DNA mutations altered these functions to make us human. Dr. Katherine Pollard is a Senior Investigator at the Gladstone Institutes and Professor of Biostatistics and Human Genetics at the University of California, San Francisco. Dr. Pollard’s lab develops statistical and computational methods for the analysis of massive biological datasets, with an emphasis on evolutionary genomics of humans and the human microbiota. She pioneered the comparative genomic approach to scan genomes of related species to identify regions that are evolving with different rates or patterns in a particular lineage. Using this technique, her lab identified the fastest evolving regions in the human genome and in the DNA of many living and ancestral species.

This lecture is sponsored by The Leakey Foundation.

World Trekkers – Thailand
Friday, Nov. 13
6:30 – 8:30 p.m.
Last World Trekkers of the year! Featuring traditional Muay Thai boxing performances by Houston Muay Thai, Thai themed painting with Young Picassos, photo ops, a living Buddha statue, exotic animals, arts & crafts, food trucks and more, you don’t need a plane ticket to visit Thailand this year! Our World Trekkers program is a series of cultural festivals for the whole family. Buy tickets now!

World Trekkers generously underwritten by GDF Suez Energy Resources.

Cookies with Santa and Event Kickoff
HMNS at Sugar Land
Saturday Nov. 14
10 a.m. – 1 p.m.
The event kicks off with our family friendly Cookies with Santa, Saturday, November 14. It’s your first chance to view the trees and catch Santa during an early holiday visit to Sugar Land. Be sure to bring your camera to snap some candids!