Lucy opens her mouth to contradict
him—Alex can tell by the way her eyebrows
go up—but the waiter has come by to take
away the dishes, refill their water glasses, and
place their entrees before them. Alex decides
bouillabaisse doesn’t look any tastier than it’s
spelled. But he digs in.
“The train cars have wheels, and they run
on tracks.” Lucy puts off trying her lobster
bisque to take advantage of Alex’s full mouth.
“Yes,” Alex drawls, “but how do the wheels
stay on the tracks?”
“Not glue, or they wouldn’t be able to
move.” Lucy takes a bite.
“The wheels have to stick just a little bit, just
the parts against the tracks, in order to push
off against the tracks and move forward.”
“That’s not glue.”
“OK, yeah, but the rails and tracks have to
adhere to each other. The rail engineers, not
“Not the people who drive the trains but the
ones who build tracks and wheels, they have
to make sure the wheels can adhere enough to
get traction, even when there are leaves on the
track, or if it’s wet…”
“Because water makes it difficult for things
to stick. Yeah.” Lucy nods. “I bet car tires
are the same way, they put treads on them to
move water out of the way.”
“I thought you weren’t interested in cars!
Or I would have borrowed the Mustang, like I
“Well, if they’re a chemistry problem…”
Alex snorts. After a second, Lucy laughs,
too. She reaches her hand across the table
and squeezes his.
This is it, Alex thinks. “So I got you a surprise for the prom.”
Lucy smiles. “Really? What? Oh, actually,
I’ve got a surprise for you, too.”
Alex stops what he was going to say. “You
did?” She did? Well, she’s not going to divert
him again. “You know Justin’s on the committee picking the prom music, right? Well, he
owes me, and I asked him to put our song on
there, no one else will know, just you and me.”
Alex grins at her.
“Oh! That’s so romantic.” She grins back.
“Yeah, especially since we’ve been talking
about sticky, gluey stuff all night.”
She narrows her eyes at him. “What?”
“Yeah, they’re going to play that old Huey
Lewis & the News song for us. You know,
where they sing, Happy to Be Stuck with You.”
Lucy starts to groan, gets a little angry, until
she realizes Alex is laughing at her.
“No, I didn’t. They’re gonna play Wake Me
Up, by Avicii.”
“Of course. Remember that was on the
radio the night we were hanging out at the
“Pouring sand through our fingers in the
dark, it was sticking together.” Lucy laughs.
“Because we have chemistry. Being stuck
with you is good.”
He stands, leaves cash on the table. “Ready
to go?” Lucy pulls out some bills. “Going
“My mom insisted. Equality and all that,”
Lucy stands up, too, steps closer to Alex.
“I didn’t give you my gift.” She leans in and
kisses him softly on his cheek. “No more
science talk for the rest of the evening.” She
laughs out loud at his surprised smile.
Diep, F. Mussels Inspire a Glue that Works
Underwater. Popular Science, Sept 22, 2014:
[accessed Nov 2015].
Scales, Helen. Mussel Adhesive Proteins.
Chemistry World, May 6, 2015: http://www.rsc.
[accessed Nov 2015].
Mary Alexandra Agner is a science writer who
lives in Somerville, Mass. This is her first article in
10 ChemMatters | FEBRUARY/MARCH 2016 www.acs.org/chemmatters
How do trains stay on the rails
when they move? What prevents
them from tipping over? The reason
is that the shape of the wheels
match exactly the shape of
the rail tracks, and the wheels
exert two types of force called
adhesion and friction, which allow
the wheels to stay connected to the
tracks, as they move. This close contact
between train wheels and rail tracks is
not related to the way mussels bind to
rocks (see main text), which is due to
intermolecular forces of attraction (see
Fig. 1, p. 9).
How Trains Stay