Kansas guard Wayne Selden Jr. (1) casts a stunned expression as Iowa State players and fans celebrate a three by the Cyclones during the second half on Saturday, Jan. 17, 2015 at Hilton Coliseum.

Book-smart types don’t have any trouble identifying Kansas University’s No. 1 Big 12 basketball rival now that Missouri has bolted to the SEC.

History and geography books and maps point to Kansas State. That’s nice, but basketball games aren’t played in libraries. They are played in buildings with home crowds determined to unnerve opponents.

Such crowds don’t need prompting from video message boards. The sort of noise that sustains itself comes from within. A combination of excitement, nerves and memories of big moments, uplifting and disappointing, results in crowd participation that grows louder and quieter based on the name of the visitors.

Again, we’re not talking about the electronic noise that blasts out of the loudspeakers and in the long run actually does more to sap the crowd of energy than to energize it because it bombards the spectators with sensory overload. We’re talking about the noise manufactured from within humans, not that which assaults human’s senses.

Nobody enlivens an Allen Fieldhouse crowd the way Iowa State does. Based in small part on the history of the rivalry and in greater part on recent thrilling games, Iowa State, not Kansas State, has replaced Missouri as KU’s No. 1 basketball rival.

When Bob Huggins took over at Kansas State, he said he didn’t consider its series with Kansas a rivalry because both teams must win a reasonable share of games for a series to count as a rivalry, and K-State had not held up its end. It still hasn’t. Kansas has won each of the past nine games against K-State in Allen Fieldhouse with an average margin of victory of more than 18 points. That doesn’t approach the degree K-State’s football team has dominated KU’s in the post-Mark Mangino/Todd Reesing years, but it’s still thorough.

Kansas, which split with K-State last season, has won 49 of the past 53 games against the Wildcats, who should be renamed the Powercats, the sooner the better.

Iowa State makes for a more exciting opponent, a more tension-filled arena. There won’t be a bigger game played at Allen Fieldhouse this season than tonight’s. The state of the Big 12 standings — KU is alone at the top with a 7-1 record, Iowa State and West Virginia tied for second at 6-2 — adds to the drama.

The schools have split the past four meetings, with Kansas outscoring the Cyclones, 333-331.

Kansas won all three games in 2013, but had to go to overtime in two of them. KU needed Ben McLemore’s banked three-pointer to send the Jan. 9, 2013 game in Allen Fieldhouse in overtime. Almost seven weeks later, Elijah Johnson’s 39 points led KU to a 108-96 overtime victory. His final two points came when the right play was to dribble out the clock. That sent Iowa State booster Melvin Weatherwax into such a rage that he nearly got himself arrested. That tirade aimed at KU coach Bill Self landed him on the average KU fan’s list of all-time villains, most of whom have played or worked for Missouri.

You won’t find the names of fifth-year Iowa State coach Fred Hoiberg and his players on that list. The Cyclones are a classy rival. And at the moment, they are undoubtedly KU’s No. 1 Big 12 basketball rival.