Akasha

Akasha is the element from which all things arise and to which all things return.  It is the backdrop or the "space" that makes it possible for all the other elements to exist.  It is all at once completely empty and yet all encompassing.  We think of all that we know as being made up of "stuff", but if you look closely enough, there's space between the stuff.

When I was in Costa Rica earlier this year, studying with Shiva Rea, I was blessed to have a physicist in my tribe.  As a wildly intelligent, spiritual practitioner, he would not only entertain my "nerding out" about all things yoga, but he would translate the vastly complex ideas into simple terms that I could understand and wrap my mind around.  I'll never forget one of our conversations about the space element when he asked me to imagine the smallest possible thing that I could.  I answered with a single atom and he described how it could be smaller still because at the center of the atom is a nucleus made up of protons and neutrons.  (Something I learned years ago, but hadn't thought about in ages.)  The next closest "something" circling the nucleus is an electron in the electron cloud...stay with me.  Between the nucleus and the electrons is space.  Now, to put this into terms that we can more readily understand, imagine that the earth were the nucleus of an atom, the next closest something (an electron) would be at a distance of Jupiter away!  So the stuff we think of as solid is really made up of organized space.  Unless there's smaller stuff that we don't yet have the ability to understand.  Hopefully I didn't lose you there, maybe Dustin Hoffman and Mark Walberg can explain it more clearly:

When hearing the word "space" I generally think of outer space - the cosmos and the sense of awe rushes over me when gazing up at the night sky.  For me, this sensation often results in contemplations on infinity and the edge of the universe which Inevitably yields acceptance of the unknown and joy in the unknowing. 

We can search and seek outside ourselves for answers, but yoga gives us an opportunity explore the inner space of our consciousness with the same curiosity and wonder that we do outer space.

Here's another video of just how mind boggling the scale of space can be.

And finally, here is a sequence to awaken the space element, akasha inside the body. 

Vayu

The air element is matter in its gaseous form.  The particles move faster and spread out making it less dense than the heavy elements of earth and water and giving it a quality of lightness.  The most direct way to experience the air element is through the breath.  We take air in and breathe air out, feeding our bodies with up to 30,000 cycles per day.  And yet, we often don't recognize this element as nourishment.  Consider however, that you can go 3 weeks without food (earth) and 3 days without water, but you can only go 3 minutes without air. 

Air resides inside the heart chakra, anahata, which is where our true nature resides and in our most natural state, we are joyful.  When meditating on the air element, I am reminded of Danielle Laporte's perfect analogy:

Happiness is like rising [champagne] bubbles -- delightful and inevitably fleeting. Joy is the oxygen -- ever present.

Agni

The fire element, agni, is the energy of accelerated change or dissolution, it transforms matter from one state to another.  It's the churning of digestion, the energy of passion and personal power.  For this reason, when we think of the fire element, we most often think of extreme heating with movement that is erratic and unpredictable.  Yet, fire element is intrinsically meditative.  One of the earliest forms of meditation for humans was to simply become mesmerized by gazing into the fire. 

Striking a balance of this element within the body is all about the practice of intelligent firekeeping.  We have to stoke the inner fire enough so that the flames do not weaken, but no so much that we "burn out" and consume all of our physical, mental and emotional resources.  On the mat, excessive fire can manifest as ego.  We push too hard or we chase a particular pose.  When in balance, the fire element supports healthy, steady strength and a slow heating of the body from the inside out.   This practice explores all forms of the fire element, both stoking the flame and cooling the inner fire.

Jala

From the stability and grounding of the earth element, we transition to matter in its liquid state.  The boundary begins to relax and we experience the fluidity of motion.  Water is dynamic and adapts to its container.  When faced with obstruction or resistance, water doesn't stop or struggle, it spontaneously changes its form and flows around the impediment following the path of least resistance.  The breath, when fluid, guides us along this same path, flowing in and out of our deepest caverns to create slow change over time. 

In the body, water or jala, is responsible for all the biofluids that keep our tissues healthy and functioning.  And in its most natural state, water flows.  When the flow stagnates, problems can occur.  In the body, this equates to poor circulation, sometimes resulting in illness or disease.  The practice of yoga asana balances the water element by clearing space for circulation and movement in both our physical and energetic bodies through the vehicle of the breath. 

Water originates in the svadhisthana (2nd) chakra and is the energy of our creativity.  It represents our ability to adapt and go with the flow.  It helps to soften our hardened edges and connect us with our inner essence, beyond the physical form.