Into Infinity

• Into Infinity
• Science
• Commentary

Science

Thanks to Marcus Lindroos for Science and Observations

• The "lightship" concept clearly refers to Eugen Sanger's "photon rocket" concept of the early 1950s. Sanger's idea was to use the mutual annihilation of matter and antimatter to produce an energetic gamma ray "exhaust" which like all other photons of electromagnetic radiation (visible light, radio waves etc.) travel at the speed of light. Unfortunately, the gamma rays produced in the electron-positron reaction favoured by Sanger will come out in random directions. To turn this "gamma ray bomb" into a useful rocket, the gamma rays would have to be channelled into a directed exhaust stream using some sort of mirror reflector. No known material seems capable of this (Sanger tried to devise an "electron gas" mirror but failed).
• If the photon drive were feasible, it could theoretically accelerate a ship to ~95% of the speed of light (.95c) assuming 80% of the ship's launch mass is propellant. Unfortunately, there would be no propellant left for orbital insertion around Alpha Centauri as well as the return trip to Earth. The effective top speed would then be .20-.25c. -- much too low for Einstein's time dilation effect to become important. Consequently the Altares must carry a system for collecting propellant from space, e.g. a magnetic "ramscoop" for gathering hydrogen atoms from the tenuous interstellar medium.
• In 2003, NASA JPL engineer Robert Frisbee investigated a slightly different "beam-core" matter-antimatter concept that would annihilate protons and antiprotons. The advantage is that unlike positron-electron annihilation, some of the resulting particles (charged pions) can be directed by magnetic fields to produce thrust. Only 22% of the propellant mass produces the momentum that drives the rocket forward For this reason, the top speed of .25c is much less than what Sanger envisioned. Frisbee's spacecraft resembles the Altares to some extent (both spaceships probably consist of propellant tanks containing frozen hydrogen and anti-hydrogen fuel pellets and an aft "spine" that houses radiators and magnetic field generators). However, a real antimatter propulsion spacecraft would have to be extremely long (600 kilometres!) and slender in order to minimise radiation damage from the vast amounts of gamma rays produced by the engine.
• The Altares' speed makes rapidly receding Pluto appear red as its light is Doppler shifted. However, the asteroids encountered in interstellar space between Alpha Centauri and our Sun must apparently be travelling at roughly the same speed as Altares (i.e. near light speed) since their light is not affected...
• The comment that the ship's relative velocity "shrinks up" the apparent size of nearby stars "as predicted by Einstein" refers to the fact that the entire starfield would be dramatically compressed toward the direction of travel. So space would seem black and empty except for the region in front of the ship, where the stars would seem brighter and more blue due to the Doppler shift.

Observations

The film deals with several scientific concepts (rotating black holes, red giant stars and supernova explosions, Einstein's theory of time dilation) but not always accurately.

• As in Space:1999, there seems to be artificial gravity generators -- a rather unnecessary gimmick since the ship's constant acceleration would produce the effect of gravity anyway.
• The ship's final velocity to Alpha Centauri seems to be about 95.5% of the speed of light so an Earth-bound observer will have wait 4.5 years for the ship to arrive at its destination. Time on board the Altares will pass somewhat more slowly since it is travelling at near-light speed, but the journey will still take a few years (Einstein's theory of relativistic time dilation is largely irrelevant on short interstellar journeys since the acceleration/deceleration phase takes 1-2 years and consequently the ship's near-light speed cruise phase is cut short. Carl Sagan estimated that the travel time to Alpha Centauri would be 4 shipboard years if the ship constantly accelerates at 1g). However, the crew does not seem to age at all. The producers could have avoided this problem by incorporating a hibernation system like the one seen in Doppelganger or 2001: A Space Odyssey.
• 
  It would seem that the Altares deploys its interstellar "satellites" at a distance of a few hundred billion kilometres (~0.03 light years) from Proxima Centauri -- the faintest and nearest member of the triple star system. The Alpha Centauri A/B pair is visible in the distance 0.2 light years away; the twin sun like stars shine much more brightly than Proxima which is a faint red dwarf.
• The crew is hit by a meteor shower after leaving Alpha Centauri; meteors impacting at 95+ per cent of the speed of light would cause major damage to the Altares (most interstellar spacecraft designs have a thick erosion shield in front).
• Compared with the Sun, the radius of the red giant star is said to be 10,000 times larger although its mass is only two solar masses -- not massive enough to explode as a supernova. The largest known red supergiant stars have radii about 2000 times that of the Sun but are much more massive than the Sun (>10 solar masses).
• The nearest super-giant stars are located thousands of light years from our solar system. The Altares would have to travel extremely close to the speed of light for shipboard time to slow down sufficiently (to the crew, it seems the journey only takes a few hours although the ship apparently has moved thousands of light years).
• The ship's acceleration is implausibly rapid (tens of thousands of miles/sec.); the crew ought to be crushed out of existence by the resulting g forces. However, some sort of acceleration damping system might be necessary for the ship to be able to fully exploit the relativistic time dilation effect (see previous paragraph).
• Neutrinos are indeed released by collapsing stars shortly before the supernova explosion starts, however, these massless particles are extremely difficult to detect (in the episode, the crew seems to use a telescope like device).
• After the supernova explosion, the Altares crew detects a signal from Beacon Delta (still located on the Moon as it was in Breakaway?) that was transmitted 15 years after Altares left the solar system. Dr. Anna Bowen concludes 15 years have passed on Earth. For the Altares to encounter a supernova, it would most likely be thousands of light years away... meaning thousands of years have passed on Earth.
• Laser beams are invisible in space. They also travel at the speed of light - the SFX shows a beam visibly moving across the space (Black Sun makes the same mistake)

Images copyright Gerry Anderson Productions
Page copyright Martin Willey