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DR CHRISTIAN

JARRETT

Neuroscientist,

writer

DR AARATHI

PRASAD

Biologist,

geneticist

DR ALASTAIR

GUNN

Astronomer,

astrophysicist

ALEXANDRA

CHEUNG

Environment/

climate expert

PROF ROBERT

MATTHEWS

Physicist,

science writer

DR HELEN

SCALES

Marine biologist,

writer

DR PETER

J BENTLEY

Computer

scientist, author

PROF ALICE

GREGORY

Psychologist,

sleep expert

LUIS

VILLAZON

Science/tech

writer

CHARLOTTE

CORNEY

Zoo director,

conservationist

PROF MARK

LORCH

Chemist,

science writer

EMMA

DAVIES

Heath expert,

science writer

Students have long been taught that all projectiles follow a

curved path known as a parabola. The explanation is that as

they fly, they cover distance both horizontally and vertically

• but only the latter is affected by the force of gravity, which
  bends the path of the projectile into a parabola. For long-
  range rockets, things are more complex. For example, air
  resistance must be taken into account. But even ignoring
  that, a projectile doesn’t really follow a parabola – because
  the Earth isn’t flat. This means that gravity doesn’t simply pull
  objects straight back down. Instead, it pulls them towards the
  centre of the Earth, whose direction changes as the projectile
  moves further down-range, away from the launch site.
  Detailed calculations then reveal that the true trajectory is not
  a parabola, but part of an ellipse. RM

Why do rockets

follow a parabola

after launch?

PHOTO: SPACEX