Mindfulness of breathing - What is meant by "arising and passing away of the body"? When it is said that one is "mindful of the arising and passing away of the body" -- what is meant with "being mindful of the arising and passing away of the body"?

The body is here all the time, solid, and I am not understanding how it is "arising and passing away"? How can I see the impermanence of the body -- it is not the same as thoughts that can arise and pass, because the body is present here all the time.
The body is here all the time, solid, and I am not understanding how
  it is "arising and passing away"?


It is extremely common to believe that the body is present all the time. Persistence of the body is actually an illusion that can be seen through using insight meditation.


  How can I see the impermanence of
  the body -- it is not the same as thoughts that can arise and pass,
  because the body is present here all the time.


First some questions to address your belief that the body is present all the time:


When you are in a deep sleep or dreaming, is your body present?
Are you always feeling the presence of your clothes pressing against your skin?


It is important when doing insight meditation to analyze your personal experience. How does your personal experience confirm or disprove the beliefs about your body that you currently have?

Most people have a deep seeded belief that the "body" and the "mind" are two separate entities. They believe that the body creates the mind through sensory organs. When I say "mind", I am referring to the experiences of seeing, hearing, tasting, touching, smelling, and thinking. If you analyze your experience honestly and without belief, you will find that experiences of mind is all that has ever arisen. We have never experienced a body, only the experiences of mind. If we have only experienced mind and never body, on what basis do we believe in the bodies existence?

So what is the body? The body is simply a label we put on different experiences. When we look in the mirror, we say "This sight is my body". When we feel a sensation of touch we say, "This pain is happening in my body". We mistakenly identify mental sensations as something more than just mental sensations.

What you call "the body" is simply mental sensations that arise and pass. The reason your "body" feels solid is because you believe it is always there.

When you have a dream you are walking somewhere, and you see your hands and feel your feet on the ground, does that prove your body in the dream really exists? Most would say your dream body is "not real" and your waking body is. But there is no difference between touch you feel in a dream, and touch you feel while you are awake. If you believe your dream body does not really exist, why do you believe your waking body really exists? If you had a dream every night that began in the same location as the last dream ended, would that prove your dream body exists?

Good luck with your journey! I hope something I wrote here will be useful to you. I pray for nothing more than your liberation this lifetime!