Wait, Isn’t Batman Supposed To Be Great At Science?

Batman Thermodynamics

Batman and Robin should enroll in Superhero Sensitivity Training Classes and find healthier ways to disagree. Meanwhile, the house is getting colder and colder because they fought about it rather than just shutting the damn window.

Okay, there’s good and bad here. Batman says “THERMODYNAMICS II: The heat goes out!”

Fair enough. The Second Law of Thermodynamics does imply, among other things, that heat energy is transferred from a warmer region to a cooler region.

Robin says “It’s because of Diffusion!”

No. Robin should have said convection rather than diffusion.

In terms of heat transfer, diffusion is generally synonymous with conduction; that is, the transfer of heat energy between bodies through direct contact. See, when an object is warm, its molecules are moving about at high speed (even if the object itself isn’t moving). Those molecules have kinetic energy. If a hot body comes in contact with a cold body (whose molecules are not moving very fast at all), the energy from the hot body’s molecules will diffuse into the cold body through sub-microscopic collisions. The hot object will get cooler as its molecules slow down, and the cold body will get warmer as its molecules speed up. This process will continue until both bodies are the same temperature.

Convection is when a fluid (like air or water) carries heat with it as it flows from one place to another. This movement is usually due to differences in buoyancy or pressure; for example, when we say that “heat rises and cold sinks”, we mean that warm air, being less dense, is buoyed up by denser cold air. As the warm air rises, it carries its heat content with it. That’s convection.

Now imagine that you’ve left the window open on a cold winter day. If there were no air movement between the interior and exterior of your home, then conduction (i.e. diffusion) would be the only way for heat to move in or out. But air is not terribly conductive, and the process would be slow. Also, air does flow, and it flows quite easily. Cold air will rush into the house and warm air will rush out. The average temperature of the air inside your house will decrease because of convection.

Robin says “And its[sic] winter[sic] i[sic] need the heat.” Batman says “We are in Australia.” Robin says “its[sic] cold there too.”

Yes Robin, Australia has winter too. There’s no reason Robin couldn’t be cold in Australia during winter. However, Australia’s seasons are opposite to those in the northern hemisphere; in other words, Australia has summer when the folks in Gotham are bundling up for winter (assuming Gotham City is in the United States). So it’s odd for Robin to imply that it would be cold in Australia at the same time it is cold in Gotham City, if that is what he’s implying.

Speaking of which, why are Batman and Robin in Australia to begin with? They could be there on vacation, but why are they in full costume? Did the Penguin commit a crime in Queensland that needs investigating?

Robin says “Its[sic] due to the elliptical path.”

I can only assume Robin is referring to the fact that Earth’s orbit around the Sun is not perfectly circular. Earth follows an elliptical path around the Sun, which means that in the course of one year, Earth gets closer to and farther away from the Sun. Earth’s closest approach to the Sun – called perihelion (pear-uh-HEE-lee-on) – occurs on January 4, and its farthest point from the Sun – aphelion (a-FEE-lee-on) – occurs on July 4. The thing is, the difference between the perihelion and aphelion distances is small compared to the size of Earth’s orbit. The average radius of Earth’s orbit is about 150 million kilometers, but the difference between perihelion and aphelion is only about three percent of that distance. In other words, if you could see Earth’s orbit traced out on a giant sheet of paper, you’d be hard pressed to tell that it isn’t actually circular.

The difference between the Earth’s perihelion and aphelion distances is not major enough to account for seasonal differences, and even if it were, it doesn’t mesh up with northern hemisphere seasons. At the moment when Earth is closest to the Sun, North America, Europe, and Asia are locked in the dead of winter, and when Earth achieves its greatest distance from the Sun, the northern hemisphere experiences summer.

The seasons are caused by Earth’s axial tilt. Earth revolves around the Sun every 365.25 days in an imaginary plane called the ecliptic. Earth also rotates on an imaginary axis every 24 hours. If the rotational axis were perpendicular to the ecliptic, then Earth would not have seasons; each and every day the Sun would pass directly overhead for folks living on the equator, and for everybody else the Sun would rise to a maximum height approximately equal to 90 degrees minus the observer’s latitude. For an observer at the north or south pole, the Sun would seem to skirt the horizon 24 hours a day, leaving the poles in perpetual twilight.

Of course that’s not the way things work. Earth’s rotational axis is tilted by about 23.5 degrees, so that it’s north rotational pole points roughly toward the star we call Polaris. As Earth moves around the Sun, the northern and southern hemispheres get varying degrees of direct sunlight, which leads to rises and falls in average surface temperature. In June, the northern hemisphere is tipped toward the Sun and receives the most direct rays of sunlight; at the same time the southern hemisphere is tipped away from the Sun and receives indirect sunlight. As a result, it’s much warmer in the northern hemisphere in June and much colder in the southern hemisphere. Six months later, in December, the northern hemisphere is tipped away from the Sun and the southern hemisphere is tipped towards the Sun. Now the northern hemisphere receives indirect sunlight while the southern hemisphere receives direct sunlight. That’s why summer comes to Australia as Gotham City is pulling out its winter clothes.

There are only two times when the Sun appears directly overhead at the equator; on the vernal and autumnal equinoxes. These days in March and September mark the beginning of spring and fall (or fall and spring if you’re in Australia), and are the days when neither hemisphere is tipped toward or away from the Sun.

Batman says “Then why dont[sic] you become batman[sic]” and Robin replies “Because Batman doesnt[sic] know Science[sic]”.

I’m not sure why becoming Batman would affect the transfer of heat or the movement of Earth in its orbit, but Robin should remember that expression about being without sin and casting stones.


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