Sigma f x Classes

Stomach Acid: Human stomach acid is incredibly strong, with a pH of 1-2, and can dissolve a razor blade.
How Stomach Protects Itself: -
Despite its corrosive nature, the stomach doesn’t digest itself because of:
Mucous lining – A thick mucus layer shields stomach tissue from acid.
Bicarbonate secretion – Neutralizes acid near the stomach lining.
Rapid cell regeneration – Stomach cells renew every few days to repair damage.

The Visible Universe: Humans can only see about 5% of the universe. The rest is composed of dark matter and dark energy, which are invisible to us.
Only ~5% of the universe is "normal" matter (stars, planets, gas, etc.) the stuff we can see.
-27% is dark matter: An invisible mass that holds galaxies together (detected only by its gravity).
-68% is dark energy: A mysterious force accelerating the universe’s expansion.
Why Can’t We See It?
-Dark matter doesn’t emit, absorb, or reflect light (hence "dark").
-Dark energy is a property of space itself, not a tangible particle.

Evidence for the Invisible Universe:
-Galaxy rotation curves (stars orbit too fast for visible matter alone).
-Gravitational lensing (light bends around unseen mass).
-Cosmic microwave background (patterns reveal dark matter/dark energy’s role).

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