
What We Found When X-Raying Some MLB Baseballs - gscott
https://fivethirtyeight.com/features/juiced-baseballs/
======
ISL
A cool article, laid out to be readily understandable for everyone.

Missing from the discussion, though, is a description of the change in the
moment of inertia. If the ball's mass distribution has shifted radially, the
moment of inertia can change significantly.

Spin matters very much to the aerodynamics of baseballs. A change in the
moment of inertia could have a substantial impact (positive or negative) on
the flight characteristics as the ball reaches the batter, the mechanics of
the ball/bat interaction (particularly as relates to the spin of the ball
leaving the bat), and the outbound trajectory. A lower-moment ball will spin
faster initially, but slow its rotation rate more quickly, making any
prediction of the overall effect of a change in moment of inertia difficult
indeed.

~~~
ComputerGuru
It's funny, because based off the header image on that page [0], that's what I
expected the discussion to be about. The center of gravity in those four
samples is hugely off.

[0]:
[https://espnfivethirtyeight.files.wordpress.com/2018/03/juic...](https://espnfivethirtyeight.files.wordpress.com/2018/03/juiced_coresplitpair_silo-2.jpg?quality=100&strip=info&w=2048)

~~~
venning
If you scroll down further in the article, you'll see that those are cropped
images of the cores. The cropping is off-center, not the cores. Otherwise,
they would wobble terribly when thrown or hit.

~~~
ComputerGuru
No, I understand that. But look closely at the x-ray/CT and you'll notice that
the rubber is nowhere near even around the core.

The background images appear to actually be a video or something, but here's a
screenshot I took:

[https://share.neosmart.net/View/Index/nfgSDo.png](https://share.neosmart.net/View/Index/nfgSDo.png)

The two balls in the first column (so one old and one new) have a pretty
symmetric distribution, but look closely at the others. Some are ridiculously
uneven.

~~~
da_chicken
Yeah, but that doesn't matter here because it's present in both the newer era
balls and the older era balls. We also know that seven of these are _used_
baseballs, meaning they could very well be deformed or off center from use.
There's a reason that they only use a baseball for about 8 pitches.
([https://www.foxsports.com/other/story/major-league-
baseballs...](https://www.foxsports.com/other/story/major-league-baseballs-
have-a-short-shelf-life-062912))

~~~
jimnotgym
In cricket the same ball is used for 480 balls (depending of format).
Initially the new hard ball is seen as an advantage to the fielding side as a
bowler gets more bounce and deviation from the hard seam, but a batsman can
also hit it further. There is also the phenomenon of swing (a bit like the
curve ball in baseball) which is accentuated by the fielders polishing one
side of the ball. As the ball ages and softens it's bounce becomes more true
and therefore it favours the batting side. Often towards the end of its life
the ball develops 'reverse-swing' where it curves the opposite way. They have
to keep the 'rough side' of the ball completely dry to do this, so all
fielders have to keep their hands dry. Penalties have been applied to players
trying to alter the condition of the ball. Different brands of ball are
polished differently and swing at different times. Some even have a lacquer
which takes a while to come off and start swinging at all

why I think this is relevant

1) The aerodynamic effects of the kind polish applied dramatically affect
performance

2) Since wear on the ball is critical to the long format games, the fans don't
get to take one home and sell it on ebay, even if they catch a six (ball hit
into the crowd) :(

The significant change in cricket hitting has been massively heavier bats,
which used to be made of compressed willow to preserve their life (a whole
season for a pro), but are now made of unpressed willow and considered
disposable. The unpressed bats work much like corked baseball bats are
supposed to, and have transformed the game. Slow-bowlers, like spin bowling
where the bowler spins the ball to alter its flight and make it move when
bouncing, have to be exceptional now or they get smashed into the car park!

~~~
danieltillett
The most significant change in cricket has been covered wickets when it rains.
If you have ever had the fun of playing on an uncovered wet wicket you will
understand how elite teams were able to be bowled out for under 20 runs on wet
wickets.

I also think more body protection has played a massive role in more aggressive
batting. When I was young I used to play with nothing more than pads, gloves
and a box and had to face bowlers who could bowl over 140km/hr on very
unpredictable wickets. I got out more than once getting out of the way of some
bouncer that stayed low as I was looking to avoid getting hit. I have been hit
enough times with a cricket ball to have learned self-preservation is the
better part of valour.

~~~
escapologybb
^This.

As a teenager growing up in the UK I played cricket for my school and a local
team, and when I was about 14 I had the "pleasure" of facing roughly four
balls bowled by the Legendary West Indies cricketer Viv Richards[1] when he
visited my school. I somehow managed to get the bat onto the first ball and
score a 4, at which I foolishly celebrated shouting something along the lines
of "in your face, I thought you were a professional cricketer!" What a stupid,
stupid thing to do.

There then followed a three ball lesson in bodyline bowling until I literally
lost my bottle and refused to carry on leaving the wicket with what little
dignity I had left. Seriously, seeing that giant six-foot tall man taking a
run-up and then bowling a cricket ball at my head at what seemed like
supersonic speed literally scared the crap out of me.

[1]:
[https://en.wikipedia.org/wiki/Viv_Richards](https://en.wikipedia.org/wiki/Viv_Richards)

------
adregan
This single paragraph is all the specifications for a legal ball in
baseball[0]:

> 3.01 (1.09) The Ball

> The ball shall be a sphere formed by yarn wound around a small core of cork,
> rubber or similar material, covered with two strips of white horsehide or
> cowhide, tightly stitched together. It shall weigh not less than five nor
> more than 5 ¼ ounces avoirdupois and measure not less than nine nor more
> than 9 ¼ inches in circumference.

So it leaves a lot of wiggle room, intentional or not, for modifying the
baseball to produce different results. As the article points out, 2014 was a
great year for pitchers with the fewest home runs since 1995. And that year,
1995, is significant as that was the year of the strike shortened season.

I'm still on the fence as to whether this is a good or bad thing (juiced
balls) as in the 20s there were rule changes regarding how balls were treated
that led to the live ball era[1] and the greatest baseball legend, Babe Ruth.

Baseball has a way of balancing out over time, so we may see a wild homerun
heyday before getting a period of pitching dominance. Both super fun to watch.

0:
[http://mlb.mlb.com/mlb/official_info/official_rules/official...](http://mlb.mlb.com/mlb/official_info/official_rules/official_rules.jsp)

1: [https://en.wikipedia.org/wiki/Live-
ball_era](https://en.wikipedia.org/wiki/Live-ball_era)

~~~
tialaramex
The article says the newer balls differed in mass by 0.5 grams and that this
difference was statistically significant

For reference the "not less than five nor more than 5 ¼ ounces avoirdupois" in
that rule means 141.747615625 to 148.83499640625 grams. (Yes exactly, the
"pound avoirdupois" no longer has any definition except that it's so-and-so
many SI kilograms).

So 0.5 grams is a pretty big change, but it's way inside the variation
allowed. Given the change in composition it seems to me that such a change is
to be expected and actually suggests the ball makers did NOT go out of their
way to hide what's happened here.

------
twoodfin
If MLB did this deliberately without the consent of the teams, some owners
might be upset.

As the article points out, players are already adapting their hitting approach
to produce more home runs, and presumably that’s at least partially due to the
added likelihood of success for that strategy with the juiced balls.

So of course there’s also a team-building aspect of this shift for GM’s to
consider. A decade ago, all the smart money was on high “OBP” (on-base
percentage) players over boom-or-bust power hitters. If MLB did juice the
ball, it shifted the ground out from under tens of millions of dollars of team
analytics, and billions in payroll decisions made based on them.

~~~
gameswithgo
>A decade ago, all the smart money was on high “OBP” (on-base percentage)
players over boom-or-bust power hitters.

That is not an entirely accurate characterization, in fact most of the time
the moneyball teams valued those boom and bust players more than traditional
teams. The actual equation they were using was something close to
3*OBP+Slugging so slugging is good, and they tend to get walks a lot along
with their strikeouts so OBP is usually good too.

~~~
majormajor
Yep, "three-true-outcomes" (HR, strikeout, walk) players were seen as
undervalued. Much of today's developments can be seen as flowing out of that
re-evaluation of the "badness" of strikeouts.

OBP driven by consistent-but-weak contact was the sort of thing that
sabermetrics types in 2008ish were shifting away from. Adam Dunn types (high
OBP power hitter, low average) were seen as undervalued compared to Juan
Pierre types (low power, higher average).

E.g. [http://www.firejoemorgan.com/2008/03/this-column-is-
eternal....](http://www.firejoemorgan.com/2008/03/this-column-is-eternal.html)

Fun thing about Pierre vs Dunn - Fangraphs has them practically tied in career
WAR in the same number of seasons. But traditional evaluations praised the
scrappy Pierre types a lot more than the strikeout-happy Dunn types.

~~~
jghn
Right. What people always seem to forget about the analytics based approaches,
particularly the "moneyball" concept is that the intent was to identify those
undervalued players. If the current trend is to prefer players with attribute
X, that means that they'll be more expensive than their relative worth, so
identify attribute Y which is also important and you can pay them a lot less.

People still refer to moneyball style approaches as if the exact metrics which
were used in 2001 are the end all be all, but as soon as people caught on to
OBP and such the real moneyballers were by definition off to something else.

------
KC8ZKF
He might be a little biased, but Justin Verlander tweeted some R analysis on
exit velo and launch angle 2014 v 2017:

[https://twitter.com/JustinVerlander/status/96939000476931686...](https://twitter.com/JustinVerlander/status/969390004769316864)

Seems the balls are flying farther?

------
forapurpose
There's an assumption that Major League Baseball cares about fair competition
and integrity, but those things are much less important than you might think.

In the 1990s, a very large number of players used performance-enhancing drugs
(PEDs). Those who were honest and declined to use them were penalized by being
less competitive (a problem any time you allow corruption - the market favors
the corrupt and weeds out the honest), undoubtedly some losing their jobs and
dreams.

MLB did nothing, other than to change the rules and ban the use of the drugs.
The cheaters suffered no penalties and their records stand; the victims,
including honest players as well as fans, no compensation or even official
acknowledgement (that I know of). One of the most prominent cheaters has a job
as a coach on major league teams, including as a hitting instructor for many
years. Another had his jersey retired by his team and was inducted into their
team Hall of Fame, and now has a job with them. (The cheaters are having a
hard time getting into the national Hall of Fame, but that's due to
sportswriters and others voting against them, and they are coming closer each
year.)

Does MLB care if the balls are juiced, or if current players have discovered
new ways to cheat?

------
Theodores
This article really does a good job of making this topic accessible to those
of us that live outside of the 'land of the free'. The graphics and UX are
really neat.

The research does prove that the ball has changed.

However, the composition of the ball has changed many times over the years
with new technology and new rules. It should be possible to look back at when
the core changed from rubber to cork (for example) and to see the effects this
has had. This bigger narrative could be useful in understanding what has gone
on lately.

[https://en.wikipedia.org/wiki/Baseball_(ball)](https://en.wikipedia.org/wiki/Baseball_\(ball\))

~~~
KC8ZKF
Exit velocity and launch angle of the ball have only been recorded since 2014.
2015 league-wide. That's why this latest change is causing all this analysis.

------
whatisunseen
Is anyone else surprised by the sample size? I'm not sure that eight baseballs
provides enough data for any relevant conclusions, especially when the
differences are so small to begin with.

~~~
mortehu
Assuming there has always been 50% light balls and 50% heavy balls, the
probability of picking 4/4 heavy balls from the earlier period and 4/4 light
balls from the later period by chance is 0.4%.

Although this statistic might be less relevant if the balls were not
statistically randomly selected.

~~~
ada1981
Presumably the eBay balls were probably homers or hit into the stands, no?

~~~
Jackim
They could also be foul tips or grounders thrown to the crowd.

------
Tarrosion
Something I rarely hear discussed around the MLB home run boom, maybe because
it's just too obvious (?):

Warm weather -> less dense air -> balls fly farther. Recent years have been
record warm. Does that have any measurable or meaningful effect?

~~~
ofcrpls
Similar discussion on cricket ball and how science shows no impact of weather
on balls flying through air significantly enough but still remains a common
misconception through out the sport's fraternity.

[http://theconversation.com/why-we-think-the-weather-
affects-...](http://theconversation.com/why-we-think-the-weather-affects-how-
a-cricket-ball-swings-when-it-doesnt-46587)

------
dbg31415
Baseball is such a data-driven sport, and numbers don't tend to lie. There's
always always some new form of juice, some changes to the mound, something
going on with the bats and balls...

* Baseball just saw its biggest home run surge since the steroids era. Here’s why. - The Washington Post || [https://www.washingtonpost.com/news/fancy-stats/wp/2016/03/0...](https://www.washingtonpost.com/news/fancy-stats/wp/2016/03/07/the-perfect-storm-that-created-baseballs-biggest-home-run-surge-since-the-steroid-era)

The real graph to pay attention to: [https://img.washingtonpost.com/wp-
apps/imrs.php?src=https://...](https://img.washingtonpost.com/wp-
apps/imrs.php?src=https://img.washingtonpost.com/news/fancy-stats/wp-
content/uploads/sites/28/2016/03/2300homeruns03071.jpg&w=1484)

Do the materials in a baseball show up differently over time, say over a 20-30
year span? I'd really want to see this done on more sets of baseballs. In
addition to testing players, if the goal was consistency it would be prudent
to scan the balls, do a core sample of the pitcher's mound every game, make
sure bat composition and temperatures are consistent... The new pitch clock
isn't going to empower pitchers either though, look for batter power to rise
again next year.

------
Someone
I find the referenced [https://fivethirtyeight.com/features/in-mlbs-new-home-
run-er...](https://fivethirtyeight.com/features/in-mlbs-new-home-run-era-its-
the-baseballs-that-are-juicing/) more interesting.

It suggests the lower air resistance makes pitchers throw faster, too.

I would think lower ridges also made pitchers throw more predictable balls.
That may have made going for a big hit a more profitable strategy.

~~~
fernly
Definitely, here is a key sentence: "The decrease in drag is probably a result
of a smaller, slicker baseball with lower seams."

The article ignores the fact that it is air resistance on the seams that
creates the "break" in a curve ball. Less drag, less effective curves, ergo,
advantage to the batter. So more HRs might come from less effective pitching.

------
mannykannot
The MLB might be well-advised to accept this analysis (together with
FiveThirtyEight's previous analysis suggesting that the rest of the uptick
might be explained by an increase in batters swinging upwards), as one
alternative putative explanation for this uptick would be that there has been
a development of new and undetectable methods of doping.

~~~
maxerickson
It's just speculation, but I would not be at all surprised if there are
protocols designed to maintain HGH and testosterone near the allowed limits.

Combine that with moderate improvements in training and there you go, 35 year
olds that can train like they are 20.

~~~
adventured
While last year didn't see particularly outsized top end homerun figures (like
the old steroid days), the increase in the huge number of people hitting 20
and 30 or more homeruns is interesting. That plays to the notion of what you
mentioned about staying near limits, as a lot of people saw a lift;
alternatively, the ball is juiced. Stanton and Judge hitting 50+ is very odd
historically as well.

2010: 18 players hit >= 30 homeruns. 77 players hit >= 20 homeruns.

2011: 24 players hit >= 30 homeruns. 68 players hit >= 20 homeruns.

2012: 27 players hit >= 30 homeruns. 79 players hit >= 20 homeruns.

2013: 14 players hit >= 30 homeruns. 80 players hit >= 20 homeruns.

2014: 11 players hit >= 30 homeruns. 57 players hit >= 20 homeruns.

2015: 20 players hit >= 30 homeruns. 64 players hit >= 20 homeruns.

2016: 38 players hit >= 30 homeruns. 111 players hit >= 20 homeruns.

2017: 41 players hit >= 30 homeruns. 117 players hit >= 20 homeruns.

Something substantial changed in 2016.

------
gz5
Can exit (exit from bat) velocity, trajectory and spin be measured and used
with the climate conditions at time of hit to compute an expected batted ball
distance which could then be compared to actual batted ball distance, with
changes over time identifying possible ball changes?

------
stretchwithme
Has anyone tested different runs of baseballs by hitting them and seeing how
far they go?

------
poulsbohemian
Something I didn't see covered in the article (maybe I missed it) was a
discussion of errors. If the ball is moving faster and potentially with more
bounce, wouldn't we also expect to see an uptick in fielding errors?

~~~
djrogers
Possibly, but this would somewhat be countered by the fact that you can’t get
a fielding error on a home run.

Edit to add more context: Home runs are much more common than errors - in
2017, there were a total of 2,820 errors, less than half the number of home
runs. One of the more common types of fielding errors is dropping a fly ball,
so it wouldn’t take a huge percentage of would-be dropped fly balls converted
to home runs to counter any uptick in fielding errors due to the ball being
bouncier.

------
joncrane
This smacks of some kind of inadvertent formulation change (like a company
started buying a component from a new supplier that met whatever specs they
were measuring, but resulted in a ball with significantly different
characteristics). Now that's it's been a couple of years, the MLB is not going
to change it back.

------
rvshchwl
Heard a segment on this on Pardon the Interruption on ESPN yesterday. I agree
with their argument that it's not a bad thing because we are in a time of
sports where games need to be more exciting. We want more home runs, and more
scorings, and if lighter baseballs means that we get them, then it's just a
normal progression.

~~~
PakG1
If we accept lighter baseballs as a way to get more home runs, what's wrong
with corked bats or any other mechanical mechanisms that could be used to
juice home runs? Sammy Sosa was suspended 8 games for using a corked bat,
which was claimed was supposed to only be for practice and was used
accidentally.

[https://en.wikipedia.org/wiki/Corked_bat#History_of_use_in_M...](https://en.wikipedia.org/wiki/Corked_bat#History_of_use_in_Major_League_Baseball)

I suppose like any other sport, baseball is picky and arbitrary about what's
OK and what's not OK when it comes to changing equipment and standards.

~~~
milesvp
I once read an article about the 'sport' of speedwalking that drove this point
home to me. This is a sport, where pretty much the only rule is that one foot
must always be touching the ground at all times. But in the age of video, it's
pretty clear that this one rule is violated by every speedwalker every race.
But the ruling body of the sport didn't care about any of the video evidence,
and doubled down on using judges with a set of criterium to determine if
walkers had both feet in the air.

My other takeaway was that if your sport can't enforce it's only major rule,
because physics, they'll find ways to lie to themselves to maintain the status
quo. It's probably a profound lesson in politics if I really think about it.

------
ada1981
I imagine someone at Ralings ”refining” the process and then placing bets for
the season on number of homers or some other metric that would payoff.

If it is in fact a variation, one should be able to create a subscription
service that sends out regular testing results on the balls, along with bets
that capitalize on the information asymmetry.

------
LoonyBalloony
Maybe just a classic case of trying to make more money by saving on material
costs and passing it off as the same product?

------
anonu
If all teams use the same baseball, does this matter? Probably not. At least
the game feels more exciting with more homers...

Nonetheless, good research...

------
thom
Stuff like this just makes me weep for sample sizes. All this data, but now
another variable to account for in _everything_.

------
oh_sigh
Will climate change have an effect on home runs? I'd imagine there would be
more home runs in warmer years.

------
weinzierl
This is a beautiful and well written article, but I find the argumentation
rather weak. Let's roll up the reasoning backwards:

The article claims that changes to three factors (weight, bounciness and air
resistance) could have caused a _25 percent increase in the number of home
runs_ [1]. The increase in the number of home runs could be from the possibly
altered balls flying farther [2].

The factors they looked into are weight, bounciness and air resistance and
their contributions break down as follows:

\- 5 feet, less air resistant, according to previous research [3]

\- 3 feet, increased speed around 0.6 mph, according to previous analysis of
bounciness [4]

\- 6 inches, decreased weight by 0.5 g of the ball, which their analysis did
_not_ show. [5]

Never mind that 5 feet 6 inches is a little less than 8.6 feet.

When it comes to bring the argument home the article either refers to other
sources instead of linking the claims together or it suggests a connection it
fails to support. All the lengthy talk about the composition of the core is
interesting and I enjoyed reading about it. It could have been used to support
the argument about the overall weight, except the article didn't show a
significant change in overall weight. It could have been used to support the
argument about bounciness, but it fails to draw that conclusion while
referring to previous research in a hand-wavy way.

I think they should just have skipped the CT scans, thermogravimetric analysis
and the scanning electron microscope analysis. For the saved money they should
have bought more balls. They could have weighed them precisely and measured
their bounciness. This wouldn't have made such a beautiful article but it
would have probably made a much stronger argument.

\--------

[1] "According to Nathan’s calculations, this would lead to a more than 25
percent increase in the number of home runs. Asked whether these changes in
combination could have significantly affected the home run rate, MLB declined
to comment."

[2] "Combine all these factors together — a lighter, more compact baseball
with tighter seams and more bounce — and the ball could fly as much as 8.6
feet farther."

[3] "According to a previous analysis performed by The Ringer, that increase
in bounciness alone would add around 0.6 mph to the speed of the ball [..]"

[4] "[..] previous research at FiveThirtyEight showed that they also became
less air resistant. The decrease in drag is probably a result of a smaller,
slicker baseball with lower seams. The change in air resistance could add an
additional 5 feet to the travel distance of a fly ball."

[5] "The overall weight of the balls also dropped by an average of about a 0.5
grams between groups, but, unlike with the cores, this difference was not
statistically significant.x

The ball as a whole weighs much more than the core alone, and there was more
variation in the weight of the full baseballs than in the weight of the cores,
both of which meant that the bar for statistically significant variations in
weight was higher for the whole baseball than for just the core."

~~~
nkurz
Can you unpack their explanation of [5]? It rings false to me, because I think
it's based on a false assumption of the distribution of baseball weights. I
think their assumptions are that both the weights of the total ball and weight
of the core follow normal distributions, but after showing that the cores do
not, they continue to assume that the weight of the whole balls does. This
feels like one of the classic critiques of frequentist statistics, where
effect size gets conflated with sample size.

Worse, shouldn't we presume that there is a (strong) quality control step,
which eliminates the tails of the distribution for overly heavy and overly
light balls, but perhaps not for heavy and light cores? Which means that our
assumptions that both the cores and balls follow the same normal distribution
for ball weight is wrong from the start, and thus the notion of "statistically
significant" shouldn't depend on total weight of the ball.

That is to say, I think the evidence is just as strong that the cores are .5 g
lighter as that the balls are .5 g lighter, but it's just a quirk of p-value
and our (known-to-be-false0 assumptions of normal distribution that make one
conclusion "significant" and the other "not significant". They did find that
the balls were .5 g lighter, right?

------
nkurz
_The cores of the new balls weighed, on average, about 0.5 grams less than the
cores from the old group. This difference was statistically significant, which
means it’s highly unlikely that it was due to sampling error._

I'm doubtful about their use of statistics here, and whether they actually
show what is being claimed. They have 4 "old" balls, and 4 "new" balls, and
are making claims about the differences between the pools of (let's guess)
100,000 balls from which they were respectively taken. They then go from here
to hypothesize that the measured differences in the samples can explain the
number of home runs hit per year.

Assume that instead of baseballs they were trying to talk about mortality
rates in small American cities, and their procedure was to sample 4 Americans
from each of two cities with different mortality rates, and then run tests on
them to determine what's causing the different death rates. While not
impossible, it would seem surprising if such a small sample would provide firm
evidence toward any conclusion. It would be less surprising if by doing
multitude of tests one could come up with something that is "statistically
significant" about the differences in the samples.

The first things that bothers me about the article is that they don't give the
actual measured values, they just say "this difference was statistically
significant". I mean, there are only eight numbers, let's see them! Also, they
don't clearly say whether there was overlap in the distributions --- that is,
where any of the "old" balls lighter than any of the "new" balls. If there was
no overlap, I'd assume they would have said so, so their silence makes me
presume overlap. By how much? What assumptions are being made about the
distributions?

Second, I wonder what other tests they ran. Presumably, if they were X-raying
the balls, they expected to see something different about the interiors, but
was this the difference they were planning to test? If you run twenty tests
(and only report one of them), you'll probably find a statistically
significant result even if it's just by chance. So did they preregister this
hypothesis? And what else did they test? One of the odd things about
concluding a "lighter core" is responsible for more home runs is that I think
a similar narrative could explain why a "heavier core" could also be an
advantage.

Third, I wonder about the sampling. Are these balls (which were bought off
Ebay) really randomly sampled from the game balls used at the each time? If
they were bought from the same sellers, might they have have been from the
same batch and thus not randomly sampled? If these were actual game balls,
were they sampled from "home run balls" rather than all balls? If so, how does
sampling from the extremes change the sample distribution? And might the balls
have changed while in storage? That is, might the older balls have heavier
cores simply because they are older, perhaps because they've been stored
somewhere humid and are absorbing water?

Fourth, rather than hypothesizing about how this tiny observed difference
might cause a large difference in number of home runs per season, how about
some tests? Do the lighter balls actually fly farther? One might take
measurements of a full set of balls, set up a batting practice with a real
pitcher a real batter, and measure how far they fly. No, one doesn't have to
do this for every article, but one also doesn't have to claim "statistical
significance" about every hypothesis. Even if the testing doesn't explain the
jump in home runs, it would be nice to have something real in the article
beyond hypothesis.

Lastly, has anything else changed? A few different pitchers and a few
different batters might also cause a large difference in home runs per season.
The weather, the stadiums, night vs day games? The "bonus" paid for hitting
home runs? They mention in the article that "The remainder could be reasonably
chalked up to a philosophical shift among MLB hitters, who are likely swinging
upward to maximize the number of balls they hit in the air and are not shy
about the increase in strikeouts that may come with that approach." Rather
than than accounting for the "remainder", is there any reason to assume that
this doesn't fully account for the difference?

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lucb1e
TL;DR: The core of the balls are 0.5g lighter, good for 15cm of extra range.
The balls are more bouncy, good for 90cm of extra range. And the balls are
slicker/smoother/less air resistant, good for 1.5m extra range. The total of
~2.6m extra range could make the difference for the observed record number of
home runs.

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dan1234
Does anyone know what they're using to layout articles like these?

I usually hate the parallax & scroll-jacking effects but they're used really
well here.

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extra88
The animated background image is actually a video [0]. There are class names
that contain "scrollmagic" so maybe that's it [1].

[0]
[https://espnfivethirtyeight.files.wordpress.com/2018/01/juic...](https://espnfivethirtyeight.files.wordpress.com/2018/01/juiced.mp4)

[1] [http://scrollmagic.io](http://scrollmagic.io)

~~~
dan1234
Yes, looks like that could be it. Thanks!

Scrubbing through the video like that is quite an interesting technique.

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fanpuns
This is such an excellent use of parallax scrolling

~~~
JeremyMorgan
Ha! my first thought as well. It's generally used in such a gimmicky fashion,
it was nice to see how this actually made the article much more useful.

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rdiddly
I hereby object to their use of "air resistant." I know what they're trying to
say, but a ball does not resist the air. The air resists the ball. Air
resistance is a property of the air, in other words, not the ball. So a ball
can't be "air resistant" at all, much less _more_ air resistant or _less_ air
resistant. In fact, because air is where the friction and resistance comes
from, it seems like "air resistance" as possessed by a ball, would be a good
thing. "This ball flies farther because it's more air resistant."

~~~
abtinf
This seems like intentional trolling. You are nitpicking a word in the article
that did not impede communication. You incorrectly describe friction without
even a first semester understanding of physics.

~~~
rdiddly
Suddenly realized why the disconnect. You're talking physics (high school
physics at that), while I'm only talking about English.

We don't say an airplane is air resistant. We say it experiences air
resistance. Case closed. You need to relax, I'm not trolling.

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redleggedfrog
Poor baseball - it's tough when you've got a hundred years of tradition to
live up to.

