ScAm - 09.2019

September 2019, ScientificAmerican.com 7

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fects that Roush articulates stem from the
use of targeted ads, which Facebook de-
pends on to make money because it does
not charge users a fee for its services.
So an obvious fix is to have users pay
for Face book. Then there would be no
need for it to sell ads or harvest personal
information about its users. The users
would decide for themselves who they
want to connect with and what infor ma-
tion to receive, not Facebook. Without the
ability or the need to target users, the
“emotion pump” Roush describes would
be turned off. As a result, social and poli-
tical polarization would diminish, and
voter manipulation would become impos-
sible—or at least much more difficult.
Facebook’s annual revenue is about
$50  billion, which comes almost entirely
from selling ads. With around two billion
users, each one would have to pay only
$25 a year to replace that revenue, which
would be a tiny fraction of what we al-
ready pay for Internet access. And the ac-
tual cost should be lower because if Face-
book stopped selling ads, all the expenses
as sociated with the advertising side of its
business would disappear.
PAUL LUKE via e-mail

CLARIFICATIONS

“Alzheimer’s AI,” by Rod McCullom [Ad-

vances], describes two brain images as

showing PET scans of a normal brain and

one with Alzheimer’s, respectively. While

the agency that provided the images fur-

nished those descriptions, an expert found

that they were not the most typical rep-

resentations for normal and Alzhei mer’s

brains, although they could have come

from such patients. Scientific Ameri can

was unable to clarify the original source of

the images.

In “Reactor Redo,” by Rod McCullum,

the opening photograph is described as

showing fuel rods. It should have ex-

plained that the rods are contained within

the visible hexagonal structures.

ERRATUM

“Night Visions,” by Amber Dance, incor-

rectly referred to a shooting star as one

point of light at any given moment. A

shooting star, or meteor, is a streak of light

rather than a single point, created when a

meteoroid enters Earth’s atmosphere.