Gallery: 9 Geeky Equations Our Readers Think You Should (at Least Pretend to) Know
01drake-equation
Last week, as part of Wired's nine-week-long geek-list parade, we gave you [nine equations that we think every true geek should know](http://stag-komodo.wired.com/wiredscience/2011/11/equations-for-geeks/) (or at least pretend to know). This week, we bring you some of the equations our readers think should have been on that list. Which list is the geekiest? We'll leave that up to you. __Above:__ Searching the Skies: The Drake Equation --------------------------------------- [](http://stag-komodo.wired.com/wiredscience/?attachment_id=85954)Fifty years ago astronomer Frank Drake attempted to estimate the number of detectable alien civilizations in our galaxy. The result is this well-known equation, which many readers felt had been overlooked. Drake’s equation states that the number of extraterrestrial civilizations in the Milky Way could be estimated by knowing several key factors, including the rate of star formation, the number of stars with planets, the number of planets that can host life and the fraction of life-bearing planets that evolve intelligent beings on them. Since it was written, astronomers have refined several of the terms, such as the number of nearby exoplanets, but many of the values in this formula are yet to be determined. Commenter [Brent pointed out](http://stag-komodo.wired.com/wiredscience/2011/11/equations-for-geeks/#comment-355847668) that the Drake equation is “relatively new and represent\[s\] still-expanding fields of knowledge” while [Bill Parrott added](http://stag-komodo.wired.com/wiredscience/2011/11/equations-for-geeks/#comment-355870241) that “the concept of life throughout the universe is one that geeks of any ilk can all get excited about.” *Image: The Arecibo Observatory in Puerto Rico, which has been used to both to search for alien radio signals and transmit our own message from Earth into space. [H. Schweiker/WIYN and NOAO/AURA/NSF](http://www.nsf.gov/news/special_reports/astronomy/images/photos/full_size/21.jpg)*
02einsteins-mass-energy-equivalence
The Most Famous Equation: E=mc^2^ --------------------------------- [](http://stag-komodo.wired.com/wiredscience/?attachment_id=85953)Many Wired Science readers reprimanded us for not including what commenter [Chris Burke called](http://stag-komodo.wired.com/wiredscience/2011/11/equations-for-geeks/#comment-355658113) “the most basic \[equation\] that everyone in the world knows.” Einstein’s mass-energy equivalence states that, taken together, matter and energy are conserved throughout the universe. The famous equation underpins the production of energy in nuclear reactors and the bellies of stars as well as the destructive force in an atomic bomb. As commenter [jack33w put it](http://stag-komodo.wired.com/wiredscience/2011/11/equations-for-geeks/#comment-356924410), this formula deserves to be on the list “because of its simplicity and profundity but also its applied impact on 20th century history.” *Image: The U.S. Navy sailed three nuclear powered vessels 49,190 km around the world in 65 days without a single refueling or replenishment in 1964. “Operation Sea Orbit” demonstrated the capability of nuclear-powered surface ships. [U.S. Navy](http://www.navsource.org/archives/02/026522.jpg)*
NASA/JPL-Caltech03einstein-field-equations
Curving Spacetime: Einstein Field Equations ------------------------------------------- [](http://stag-komodo.wired.com/wiredscience/?attachment_id=85952)Our original list included the [Friedmann equations](http://stag-komodo.wired.com/wiredscience/2011/11/equations-for-geeks/?pid=2357), which describe the life of the universe from start to finish. It therefore makes sense to mention the “granddaddy equation” from which these formulas are derived: Einstein’s field equation, the core feature of General Relativity. As commenter [pjcamp astutely wrote](http://stag-komodo.wired.com/wiredscience/2011/11/equations-for-geeks/#comment-355610272): This is a blindingly simple equation with profound meaning. The left hand side is the gravitational field tensor, a description of the curvature of spacetime \[plus the [cosmological constant](http://en.wikipedia.org/wiki/Cosmological_constant)\]. On the right hand side are a couple of constants and the energy tensor, a description of the distribution of mass and energy in spacetime. What it is telling us is that the structure of geometry is determined by the distribution of energy; a truly weird idea. Going a little further, since gravity is itself a form of energy, the field equation is telling us that gravity can serve as its own source, and there are, in fact, nontrivial solutions to the Einstein equations that contain nothing but empty space, no other forms of matter or energy at all. *Image: Artist's representation of the curvature of spacetime due to two massive galaxies. [NASA/JPL-Caltech/R. Hurt (SSC)](http://www.galex.caltech.edu/media/glx2011-01r_img01.html)*
SrA Kenny Holston04shannon-hartley-theorem
Communication Foundation: Shannon-Hartley Theorem ------------------------------------------------- [](http://stag-komodo.wired.com/images_blogs/wiredscience/2011/11/shannon-hartley.jpg)Developed to describe how much information could be carried over a telegraph line, the Shannon-Hartley theorem has become "the foundation of all communication system we use today, from mobile phones, through cable modems to satellite communications and fiber optic channels," [wrote commenter stoffer.](http://stag-komodo.wired.com/wiredscience/2011/11/equations-for-geeks/?pid=2364&pageid=83817&viewall=true#comment-355605070) "This formula is the foundation of modern communications age." *Image: [Kenny Holston](https://secure.flickr.com/photos/kennyholston/4977284472/)/Flickr*
05pythagorean-theorem
Triangle Appeal: The Pythagorean Theorem ---------------------------------------- [](http://stag-komodo.wired.com/images_blogs/wiredscience/2011/11/pythagorean_theorem.jpg)As elegant an equation as exists, the Pythagorean theorem is a masterpiece of classical mathematics: It states that, for a triangle with one 90-degree angle, the squared length of its longest side is equal to the squared and added lengths of the other two sides. This simple fact is as useful now as it was 2,600 years ago. *Image: [Niek Sprakel](https://secure.flickr.com/photos/thcganja/419539392/)/Flickr*
06bayes-rule
How Likely is That?: Bayes' Rule -------------------------------- [](http://stag-komodo.wired.com/images_blogs/wiredscience/2011/11/bayes_rule.jpg)First proposed in the 18th century by the Reverend Thomas Bayes, his rule is a scalable tool for determining probability. "Simple and universal for everything from spam filters \[and\] vaccination efficacy to finding lost atomic bombs," [commented Jonathan Pace.](http://stag-komodo.wired.com/wiredscience/2011/11/equations-for-geeks/?pid=2364&pageid=83817&viewall=true#comment-355847698) *Image: [Tomi Tapio](https://secure.flickr.com/photos/tomitapio/5095950637/sizes/l/in/photostream/)/Flickr*
07ohms-law-triangle-pin
Resistance is Futile: Ohm’s Law ------------------------------- We thought Ohm’s Law was too plain to list, and we feared it might conjure unpleasant physics laboratory flashbacks. [](http://stag-komodo.wired.com/images_blogs/wiredscience/2011/11/ohms-law-nasa-glenn.jpg)But some readers wielded hot soldering irons over our omission. “Not even ‘geeks’ could reference, nor understand, some of these equations,” [wrote user Agilis.](http://stag-komodo.wired.com/wiredscience/2011/11/equations-for-geeks/?pid=2364&pageid=83817&viewall=true#comment-355766763) “All you did is make some of your readers’ minds hurt.” The primary equation of Ohm’s Law describes the inescapable relationship between voltage (V), current (I) and resistance (R) of an electrical system. Another form (bottom) gives the power (P) of heat dissipated by a resistor as charged particles (e.g., electrons) bump into the resistor’s atoms during their amped-up journey. *Images: 1) [Rain Rabbit](http://www.flickr.com/photos/37996583811@N01/5410336250/)/Flickr/CC[](http://www.flickr.com/photos/37996583811@N01/5410336250/) 2) [NASA Glenn Research Center](http://www.grc.nasa.gov/WWW/k-12/airplane/ohms.html)*
08force-equals-mass-times-acceleration-fence
The Force: Newton’s Second Law ------------------------------ More than any other equation, the one representing Newton’s second law of motion was sorely missed by readers of our first geeky gallery. “It's the mother of all equations!” [wrote user Dan Sager.](http://stag-komodo.wired.com/wiredscience/2011/11/equations-for-geeks/?pid=2364&pageid=83817&viewall=true#comment-357171897) Commenter [kamikrazee provided](http://stag-komodo.wired.com/wiredscience/2011/11/equations-for-geeks/?pid=2364&pageid=83817&viewall=true#comment-356083778) a practical application: “Newton’s Second Law … serves mainly to keep us from crapping ourselves on a rough flight.” Aristotle was one of the first to suspect the relationship between force (F), mass (m) and acceleration (a). However, he neglected the role of friction. Galileo picked up where Aristotle left off by hashing out inertia, but gravity as a vertical force eluded Galileo. Sir Isaac Newton eventually cleaned up by developing differential calculus and his famous equation, F = ma *Image: [roblz.com](http://www.flickr.com/photos/roblz/2445993119/)/Flickr/CC*
09boiling-liquid-nitrogen
Up In Smoke: The Ideal Gas Law ------------------------------ Readers found no shortage of ways to gas Wired Science about leaving out PV = NkT from our [geeky equations](http://stag-komodo.wired.com/wiredscience/2011/11/equations-for-geeks/) gallery. The equation of state most geeks know is PV = nRT, but both forms show the interplay between pressure (P), volume (V) and temperature (T) in ideal system. It cuts to the heart of countless gassy phenomena, including boiling liquid (above), weather patterns and even bong hits. “Poor geeks.. stoner’s only need one equation,” [wrote user AngryBuddha.](http://stag-komodo.wired.com/wiredscience/2011/11/equations-for-geeks/?pid=2364&pageid=83817&viewall=true#comment-355839661) *Image: [Dave Mosher](http://www.flickr.com/photos/davemosher/6010975573/)/Wired.com/Flickr/CC* __See Also:__
