title: Why is OnCollisionEnter getting called twice?
body: <p>I have got a <em>Cube</em>(player) and a <em>Plane</em>(floor) in my Scene. Both have <code>Colliders</code> attached to them and there is a <code>RigidBody</code> component attached only to the <em>Cube</em>. <em>Cube</em> is positioned above the <em>Plane</em>.</p>
  <p><em>Cube</em> has a script attached to it which looks for Collisions.</p>
  <pre><code>private void OnCollisionEnter(Collision collision)
      {
          Debug.Log(&quot;...........................Collision&quot;);
      }
  </code></pre>
  <p><strong>PROBLEM:</strong></p>
  <p>When the Plane and the Cube collides, the message gets printed twice.</p>
  <blockquote>
  <p>...........................Collision</p>
  <p>UnityEngine.Debug:Log(Object)
  jump:OnCollisionEnter(Collision) (at Assets/jump.cs:34)</p>
  <p>...........................Collision</p>
  <p>UnityEngine.Debug:Log(Object)
  jump:OnCollisionEnter(Collision) (at Assets/jump.cs:34)</p>
  </blockquote>
  <p>Why is this happening? Is collision happening twice?</p>