Going, going ... gonzo: Why are homers piling up?

Cody Bellinger has 34 home runs for the Dodgers through Aug. 22. Joe Robbins/Getty Images

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Epic blasts are leaving ballparks nearly every night in this summer of the long ball, and everybody has favorites-a Cody Bellinger moon shot here, a Joey Gallo walk-off there. I thought no home run accomplishment in 2017 could surpass a guy named Scooter clubbing four in one game until Matt Olson, Franklin Barreto and Jaycob Brugman of Oakland each mashed his first major league tater on the same day. That hadn't happened since three members of the Kansas City Packers-that's right, of the Federal League-thumped round-trippers 103 years ago.

The overall numbers are staggering: MLB batters this season are hitting a whopping 1.26 long balls per team per game (through Aug. 10), by far the most in history-a higher rate than in the days of Barry Bonds or Babe Ruth or any expansion season. Home runs now account for 14.5 percent of all hits, which is the highest proportion ever and up from 10.1 percent in the previous three years. All of which raises the question: What the heck is going on out there?

I know for some of you, steroids will leap to mind. But while the cat-and-mouse game of doping and enforcement will probably never end, chemicals are almost certainly not powering this surge. Common sense says it would be nearly impossible for any new substance to be strong enough and spread fast enough to cause such a massive, sudden jump in home runs while remaining untraceable. More important, power has increased across MLB rosters-there's no handful of high-octane supersluggers breaking away from the rest of the game, as happened when anabolics were common but unevenly effective. No player this year is close to being on pace to break Bonds' single-season record of 73 homers. That indicates a more universal cause, and the latest research has found one: The baseball itself has changed.

Ben Lindbergh of The Ringer and sabermetrician Mitchel Lichtman sent a group of balls to Washington State University's Sports Science Laboratory for testing, including 17 from the first half of 2015, just before home runs started to soar, and 10 from 2016. In research published in June, they found small but significant differences, all in directions friendly to home runs: On the whole, the newer balls were bouncier and smaller and had lower seams. The combined effect would have been enough to make baseballs travel an average of 7.1 feet farther. In another June study, Rob Arthur of FiveThirtyEight looked at air resistance to balls by tracking how MLB pitches decline in speed from point of release to crossing the plate. He found that baseballs have been generating less drag since 2015, to an extent much greater than would be likely from random variation. I would add this: Eight pitchers have gone on the DL with blisters this year compared with six total from 2010 to 2015, according to STATS LLC, suggesting that something about gripping baseballs has changed pretty abruptly.

MLB insists its balls aren't juiced, but its specifications leave a lot of wiggle room. One study conducted at the University of Massachusetts Lowell in 2000 notoriously found that two baseballs could both meet MLB's game-ready standards yet differ so much in composition that one would travel 49.1 feet farther than the other when hit. I can't tell you if it's intentional, but the numbers say that increased bounciness and tighter seams are goosing today's baseballs.

Meanwhile, researchers have studied other possible causes for the home run surge, from batting orders to global warming, without finding much. But there's one more factor worth watching: With Statcast data on launch angles and exit velocity now flooding screens, teams and players are more aware that fly balls tend to produce better outcomes for batters than ground balls. So far, new homers are mostly coming from the increased zoom of batted balls, not a major shift in their launch angles. But sometimes change accelerates because of a friendly environment. Baseball left its dead ball era, for example, not only because balls got bouncier in 1919 but also because they got cleaner in 1920, when MLB outlawed the spitball, and easier to see, when teams began regularly substituting fresh balls into games after Cleveland's Ray Chapman was killed by a pitch. And then Ruth showed the world how to treat those shiny new orbs.

We are just at the beginning of a potential fly ball revolution, with hitters such as J.D. Martinez, Daniel Murphy and Yonder Alonso improving quickly and immensely by elevating. I suspect the seam height on baseballs will continue to flow and ebb, but hard-hitting uppercutters will keep pushing home run totals skyward.