Hourglass and computer: what they have in common

1. Step 1. Hourglass — uses — Gravity flow. Sand pours through under gravity.
2. Step 2. Gravity flow — is used in — Water filter. Water seeps through by gravity.
3. Step 3. Water filter — is made of — Silica (sand). Slow filters are layers of sand and gravel.
4. Step 4. Silica (sand) — is material for — Internet. The backbones are silica optical fibre.
5. Step 5. Internet — has part — Computer. The Internet links billions of computers.

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