Echoes Through Time
From Halopedia, the Halo wiki
The third episode quickly began with a piece of audio from the second server that revealed an image. MSN released Iris themed items, that featured imagery that looked like the image revealed from the second servers audio. When the audio was played on a hidden screen on Halo3.com, an animation played leading people to the third server. The third server detailed the problems the Forerunners faced while trying to deal with the Flood, while also giving a direct message from the mysterious entity.
On July 26, at Halo3.com, on the concept art section, after the thumbnail for Spartan Laser, is a thumbnail labeled "The Device". When the thumbnail is clicked, a window will pop up, and once you click "Initiate", it tells you it's waiting for sound input. If you have a microphone connected, you can speak and it will make echoes of your voice. By tapping hard enough to generate some noise on your microphone repeatably with a certain interval between each tap, or by playing the file 719 Hz.wav downloaded from one of the episodes, it will unlock the glyph and give you a link to Server 3. Note: A few people have unlocked the glyph by whispering Iris into their microphone, although this is doubtful how it was meant to be unlocked.
Ψ(bar, sub 0) = √(m/π)*e^(-2α(xbarsubi)² + A)
This is the quantum mechanics wave form formula. The original equation given to us is incomplete, though it can be seen as an example of Schrödinger’s equation. Many of his equations incorporate Newton's second law: f=ma. Einstein theorized that if you could travel faster than the speed of light, you would be able to observe the past in some way. Of course, it's incomplete and different from most of Schrödinger’s equations, so it's possible that it is trying to hypothesize time travel.