Play Ball

                It’s baseball season.  My favorite sport ever is a seven month marathon that stretches from April to October (although, you could argue late February – November).  Being born in Philadelphia makes me a huge Phillies fan.  I’m not one of those fair-weather fans or band-wagoners, either – I’ve loved the Phillies since 1993.  I still loved them when they weren’t the best in the late 90s/early 2000s because they are my hometown team.  When I scored a ticket the second half of World Series Game 6 in 2008, I nearly cried - I got to see them win the World Series.  I also saw them beat the LA Dodgers the next year for their second straight NL pennant.  Nothing beats screaming “Beat LA” with your rally towel.  Nothing.

                Anyone who watches baseball has heard commentators say such things as “The ball is going to fly well on this hot night!” and “Well, we’re in Colorado.  This is a homerun park.”  Basically, the commentators are saying that baseballs tend to fly farther on hotter nights than colder nights or at baseball parks at higher elevations than others.  Baseballs that fly farther mean more homeruns.  

                Why is that?

                Let’s talk about air first.

                What we call “air” is a gas that is a mixture of several different molecules: oxygen, nitrogen, carbon dioxide, among others.  That should make sense – humans breathe in oxygen and breathe out carbon dioxide so those gases must be floating around in the air.  (Plants do the opposite: they take in carbon dioxide and let out oxygen – gotta love plants.)

                So, are all these molecules just bouncing off each other?  Is the air a jumbled mess of molecules that are all jostling around like in Figure 24.1?

                The answer is no.  Gases look different than the other two phases of matter: solids and liquids. I’m going to explain what a gas actually looks like by comparing it to a how solids and liquids look like.

                Let’s start with solids.

                Solids, such as ice or table salt, are ordered arrays of molecules (Figure 24.2).  The individual atoms or molecules are actually touching and strongly interacting with each other.  Think of a solid as a marching band: all the individual players (molecules/atoms) must stand in their respective places and any movement requires all the players to move together.

                Next comes liquid.

                Liquids have lost their orderly array and are more a jumbled mess (Figure 24.3).  The individual atoms or molecules interact with each other far less and can move somewhat independently.  Think of a liquid as a large crowd trying to move through a corridor.  Each person is moving independently but their movements are limited or affected by the other people in the hallway.

                Finally, we have gases.

                Gases have very large spaces between the individual molecules and atoms (Figure 24.4).  The interactions between the individual particles are very small.  They barely see each other!  Gases are mostly empty space.

                Okay, so what does this have to do with baseball?

                Baseballs are flying through air, which is a gas.  Figure 24.4 is showing you what a gas looks like.  Where there are no molecules is just empty space.  Baseballs are flying through mostly empty space with some molecules floating around.  

                The post called Absolute Zero briefly discusses something called the Ideal Gas Law.  I’m not going to go into it here except to say that due to their large amounts of empty space, gases are highly affected by temperature and pressure.  You might want to go back and read the post (It was a 2011 February post) before I explain why baseballs will fly farther in either hotter temperatures or higher elevations.

                Let’s start with hotter temperatures.

                The Ideal Gas Law tells us that a colder gas is a smaller gas.  The number of particles don’t change but the volume those particles inhabit becomes smaller.  Figure 24.5 shows you how a gas looks at two different temperatures.  A colder gas has its molecules closer together than the hotter gas.  You can also say that a colder gas has a larger density, where density is telling you how many particles you have per unit volume. 

                What does this mean for baseball?  On a hot night, a baseball will fly through a hot gas.  A hot gas has its molecules further apart, meaning there is more empty space.  The more empty space a baseball has to fly through, the further is can go because it won’t be encountering other molecules.  Sure a baseball is much larger than a molecule, but every molecule the ball encounters serves to slow down its speed.  The less it sees, the further it will go.  Hence, hot nights mean more homeruns.

               

                Okay, let’s now do pressure.

                The Ideal Gas Law tells us that a lower pressure gas has a larger volume.  The number of particles don’t change, but the volume of those particles inhabit becomes bigger.  Figure 24.6 shows you how a gas looks at two different pressures.  The pressure in Colorado is much lower than the pressure in Philadelphia.  Lowering the pressure has the same effect as heating a gas up – more open space, less molecules for the baseball to encounter and hence, more homeruns!

               

                If you, like me, love baseball, then enjoy the All Star Game this week!  I’m thrilled to see Halladay, Lee and Hamels go.  Congrats to those Phils who won’t play due to injury: Placido Polanco (starting 3^rd baseman) and Shane Victorino (final chosen outfielder).  

I hope the second half of the season is as awesome as the first!

Density: a measure of how much matter exists per unit volume.  For gases, a higher density means more particles per unit volume, while a lower density means fewer particles per unit volume.  

Lower density = fewer particles = more open space = further a baseball will fly.

Higher density = more particles = less open space = less a baseball will fly.

Hotter temperatures = higher elevations = lower density = everything written above!

REFERENCES

Zumdahl, Steven S. “Chemical Principles, 4^th Edition” (2002) Houghton Mifflin Company, Boston, MA.