Ryan is absolutely correct.
The main reason why people think of their physical body as "real" or "solid" is because the five organic senses project that iillusion to the Conscious Mind. In reality, the physical body only exists as Energy, and, just as in the Etheric and Astral, can be shaped by Mind. This is fully supported by Quantum Mechanics.
The apparent paradox is that as we focus, or "travel" inwards, our environment seems even more "solid" and "real due to the progressively higher vibration - as for the example is viewed as the difference between an old colour TV and a modern HD TV which has a much higher density of pixels.
If you wish to read more, here is a link to the 45 page paper I wrote on the subject:http://www.ourultimatereality.com/files/TheRealityMatrix.pdf
As for immortal - yes - we are immortal and Eternal Expressions of Source.
The Great Transition known iconically as "2012" is an opportunity to Evolve to a Higher Level, and opportunity that presents itself once every 26000 years or so. During the last Transition humans Evolved from Neanderthal to Homo Sapien. Anthroplogists will never find "the missing link" simply because there isn't one.
This does not mean that on 21 December 2012 there will be an "event". It is simply the pivotal point at which all those who can make the leap in evolution will need to be prepared. The Transition will follow over the next few years or even decades. Right now few are prepared, but the number is increasing exponentially as Consciousness is transformed from many directions. We are also seeing the polarisation between the extremes of humanity from the darkest to the Light - as has happened in previous transitional events - which is always resolved by a "cleansing" event or events, so humanity can "reset" and start over.
Those who do not make it this time around will transition to their rightful vibration in the Astral - none will simply "cease to exist". All Life continues Eternally, all paths ultimately leading to the One Source.
In Love, Light and Service,