Echoes (Stargate Atlantis)

"Echoes (Stargate Atlantis)"

"Echoes" is an episode from Season 3 of the science fiction television series Stargate Atlantis.

Plot

Teyla begins to see repeat visions of Ancients on Atlantis. First she is assumed to be under stress, but after a while other people on board begin to see the same visions.

Meanwhile, McKay and Sheppard see a sea creature named "Sam" (after Samantha Carter) by McKay, similar to that which led Sheppard and Zelenka to rescue McKay in "Grace Under Pressure" and decides to take a Puddle Jumper to investigate underwater. During a close encounter with the sea creatures, Sheppard and McKay develop intense headaches and McKay falls unconscious.

In the infirmary, Zelenka explains that the sea creatures emit a low frequency pulse and an electromagnetic field which, in combination, are very dangerous to humans. Very soon, most of the city is affected by this. Many victims are transported to the Daedalus, now orbitting the planet, but there are too many in the city to all be removed.

After recovering, McKay locates an Ancient bio-lab dedicated to studying the native marine life and manages to translate what the whales are saying. The Atlantean whales are warning that the sun is about to send out a gigantic coronal mass ejection (similar to a solar flare) straight at the Lantean planet and although the shield will protect Atlantis, the radiation wave will kill all plant and animal life on the planet and render the atmosphere unbreatheable. The whales are congregating underneath Atlantis for protection.

The visions that people have been seeing are a racial memory that the whales have of this catastrophe, which happens every 15,000 years. An Ancient ship was near to the sun when the ejection began and most of its crew were killed immediately by the radiation. The pilot managed to jump to hyperspace and overtake the radiation wave before it reached Atlantis and warn the people there.

Now knowing what is happening, the team consult the Ancient database and discover that the last time this happened the Ancients managed to temporarily expand the cities' shield to encompass a large percentage of the planets surface. Unfortunately, with only one functioning ZPM, McKay is only able to expand the shield to a radius of a few kilometers.

In order to save Atlantis as well as the planet, Sheppard comes up with an idea. The ZPM is transferred to the Daedalus and the ship moves into position between the sun and the planet. When the coronal mass ejection begins, the shields aboard the Daedalus (boosted by the ZPM) successfully deflect the emission away from the planet, the Daedalus sustaining only minor thermal damage in the attempt.

Notes

• Three ZPMs were installed in Atlantis to power the Stardrive during the Asuran invasion in "The Return", which were recovered by the expedition when they reclaimed the city. One ZPM is being used by Atlantis, while the other two are being used to power the Ancient outpost in Antarctica and the Odyssey.
• There are new areas of the city that can be explored due to the repairs completed by the Asurans, such as the lab discovered by Rodney.
• The Lantean name of the alien "whale" species is flagisalis.
• How the whales could forecast the flare well in advance of the sensors on Atlantis is not explained in the episode, but reference is made to Terran animals having similar ability to sense natural disasters.
• When McKay and Sheppard discover the second flagisalis circling the city, Sheppard remarks that it's "the size of a football field," whereupon McKay replies, "Canadian football field." American football fields differ in size depending on whether they are high school, college, or NFL, but he is most likely referring to professional football. In this case, Sheppard believes the flagisalis to be around 360 feet (110 m) long. Canadian football fields, however, are larger, so McKay is saying that the flagisalis is closer to 450 feet (140 m) long.