Fringe : Season 3 : Episode 5 : “Amber 31422”
This week in Earth-2 events, we have identical twins pulling the old switcheroo on the Fringe team, even after one of them has been encased in synthetic amber for several years. The trend of watchable but science-light stories has finally been broken, and this week I’ll be talking about ion lasers.
My first thought when the twin-extraction team pulled down that block of amber was, “that must weigh an absolute ton”. Turns out it’s synthetic amber, which behaves suspiciously like ballistics gel as soon as it’s removed from the main mass. It also appears to be self-repairing, with no apparent source of new matter.
No, there is no such thing as “negative matter”. The closest we might get is antimatter, which nobody on either Earth could conceivably possess. Should we suppose that the hole in the wall appears through matter-antimatter annihilation? Well, let’s say that the removed concrete is a cylinder with a diameter and depth of 1 m. This give us a volume of ~0.785 m3 (π r2 h), which would have a mass of around ~1800 kg (assuming a density of 2300 kg m-3). Converting this to energy (E = m c2) gives us ~1.6 x 1020 J that our bank robber has to get rid of somehow. To put this in perspective, 1.6 x 1020 J is roughly equivalent to 39,000 megatons, 2,500,000 Hiroshimas, or the entire world’s energy consumption for four months.
Perhaps the stolen ferrocene has something to do with this apparent stumbling block? It was one of the first sandwich compounds to be discovered, renewing interest in organometallics back in the 1950s, but has absolutely no relation to antimatter, lasers or unusual vibrational frequencies. Suggestions as to how the writers managed to get from atom-dissolving negative matter rings to ferrocene are welcome.
Presumably nobody works in the souvenir store that Olivia keeps jumping into, or they might notice somebody appearing and breaking snow-globes.
The ion laser
First of all, Agent Lee couldn’t have reliably identified an ion laser just by looking at it, because all lasers look the same (i.e. a metal box). We do know that the Fringe-verse sometimes clearly labels items (e.g. the CAR BATTERY in The Man From the Other Side), in which case his pronouncement was completely redundant.
You may recall from previous shows that atoms and molecules have discrete energy levels, and that electrons can be excited up to higher levels with an appropriate energy input. The excited states are unstable, and the atom/molecule will eventually relax back to ground state by (usually) emitting a photon. This process is called spontaneous emission, and is identical to fluorescence. However, if a photon with the same energy as the energy difference between the upper and lower states interacts with the excited atom/molecule, then the atom/molecule will immediately relax and emit an additional photon. This additional photon has the same direction, energy and phase as the incident one, giving an amplification effect. This process is called stimulated emission.
In order for stimulated emission (and therefore our laser) to work, we need a steady supply of photons with a certain energy, and a lasing medium rich in excited atoms/molecules. Generally, an electrically-powered photon source is used to generate metastable excited states (which are long-lived, and therefore more likely to interact with an incoming photon) – a process known as pumping. The excited states spontaneously relax as expected, and mirrors then reflect the emitted photons back into the lasing medium. These photons have the same energy as the excited/ground energy difference, and hence interact with new excited states (formed due to the pumping action) to give us our stimulated emission. Between ~1 % and ~10 % of these photons are reflected in such a way that they escape the lasing medium as the laser beam.
There are many different kinds of lasing medium, which can be selected and modified to produce a wide range of laser frequencies and intensities. Ion lasers use an ionised gas (commonly argon or krypton), and hence have higher energy requirements than other gas lasers due to the extra energy needed for ionisation.
For background information on this topic, see the primer on energy levels.