The story begins with the
Cassini Saturn spacecraft releasing the
Huygens Titan probe. The scene is then transposed to
Earth, where a 12-year-old girl, Jeana (voiced by
Abigail Breslin), places a
sun filter over a
telescope to view
sun spots. She asks her mentor, a
Professor (voiced by
Neil Armstrong) "Why is the
Sun so bright?" This leads the professor to launch into a
scientific explanation about
fusion. The little girl laughs, having played this trick on her mentor many times, she says "No, I meant bright, bright like happy. In most drawings, the sun has a big smile. Is he good, like the man in the moon." Knowing this means she wants a story, the
mentor begins to
spin a tale, but as a mentor, this one, while entertaining, is also
educational. As he speaks, we
transfer to the Sun, and watching a sunspot spin into view, we dive into and pass through the
chromosphere, and head toward the
center. The mentor lays down the basis of our story as we travel through the Sun. He explains that the "man in the sun is called the Core (voiced by
William Shatner)" and spins a story how he is good and that his children "
photons" are sent out to chase away the darkness, and bring life, warmth, and knowledge to Earth. He adds that the only being who does not like the Core is a creature called the "Void" (voiced by
Mark Hamill) who is an ancient, malevolent, being who existed before the
Big Bang, and who sits at the edge of the
Solar System, scheming to stop the Core. The scene fades through a
plasma wall, into "The Hall of Destiny" where we are introduced to the main character in the story – David (voiced by
Chris Pine), a young Photon who should have begun his travel to the surface a million years ago. The Core, tries to get him moving on his journey, but David is fearful. We cut to the
Kuiper Belt where a large space battle rages between two fleets – one composed of
protons, and the opposing fleet of
anti-protons. A character we call "The Ranger (voiced by
Amanda Peet), who is a
neutrino scout, makes it through the battle lines and heads to the Sun. Back in the Sun, David is kicking
solid light sculptures into a
plasma fountain. The Ranger crashes through the wall into David, followed by some imaginary creatures called Gell-Mann
ghosts. The Ranger is trying to get to
Saturn (other side of the Sun), to deliver a message to the Cassini Space Core Commander. The Gell-Mann ghosts (nasty creatures) surround them. The only way to escape is to give the message scroll to David, and ask him to deliver it while the Ranger holds the ghosts at bay. David sails through the Sun and encounters a "surfer dude" Solar Proton, Jammer (voiced by
Hayden Christensen), who surfs the solar winds. David's journey takes him through the Solar System, to an exploration of the
moons of Saturn. Eventually he finds Milton (voiced by
Robert Picardo), an older photon character who is mining for
free quarks. Milton teaches David introductory material about
electrons, protons,
quarks, etc. The two evade the evil/comical forces of the Void, until they get captured by the "Dark Side of the Moon". In the process of escaping viewers learn about the
fundamental modes of motion and introduce
basic quantum concepts. The message scroll is partially damaged, so David does not know who the space commander is, but he knows that he needs to get to the
Cassini spacecraft, because something bad will happen. He gets inside the
Cassini craft and encounters the ship's computer, GAL 2000 (voiced by
Sandra Oh), who, in the course of determining the danger, teaches David about
spectra, the mission of the spacecraft, different
radiation bands used for
remote sensing, etc. In the end, they save the antenna of the ship from a beam of
anti-matter sent by the Void. They do this with the help of Jammer. David discovers that he is the Space Core Commander (all this time, searching for himself). He leads the transmission back to Earth, and through a system of
antennas, is processed, and as Jeana accesses the Web page of JPL, he flies through the screen and enters Jeana's eye. ==Voice cast==