Notes on "Blood Vessels Length" Research Riddle

Introduction

• Fun fact: Combined length of human blood vessels is claimed to be 100,000 km, enough to wrap around the Earth twice.
• Used frequently in various mediums without verification of its origin.

Research Journey

• Initial Search:
  • Numerous sources (books, blogs, educational notes) cite the number.
  • No explicit original source found, just perpetuated as a truism.
• Discrepancies Noted:
  • Inconsistent claims about what the number represents (capillaries, veins + arteries, all vessels).
• Importance of Accuracy:
  • Critical for fact-checking and credibility.
  • Personal motivation to uncover the true origin.

Deep Dive into Sources

• Search Attempts:
  • Google and PUBMED searches were inconclusive.
  • Consulted authors of biology textbooks citing the number without original sources.
• Historical Search:
  • Identification of old books: "Vital Circuits" by Steven Vogel and "Looking at the Body" by David Suzuki.
  • Contacted Dr. Suzuki, who couldn’t recall the source from his 30-year-old book.
  • Vogel’s book listed many references without specific attribution.

Discovery of Original Source

• Breakthrough:
  • Found 1959 Scientific American article referencing August Krogh’s 1922 book.
  • Krogh, a Nobel laureate, estimated the length using assumptions prevalent at the time.
• Evaluation of Krogh’s Work:
  • Krogh’s assumptions on capillary density deemed inaccurate by today’s standards.
  • Based on idealized human body metrics.

Updated Scientific Understanding

• New Findings:
  • Recent scientific paper estimates actual length of human capillaries to be 9,000 - 19,000 km.
  • Misleading original figure persists due to its memorable nature.

Reflections on Research and Information Dissemination

• Challenges of Accuracy:
  • Confirmation bias and repetition of incorrect data can perpetuate misinformation.
  • Significant effort required to verify facts and trace original sources.
• Importance for Science Communication:
  • Maintaining credibility and accuracy in educational content.
  • Efforts by organizations like kurzgesagt to provide verified and accurate scientific stories.

Conclusion

• Lessons Learned:
  • Importance of persistence and thoroughness in research.
  • Encouragement to challenge common wisdom and follow evidence meticulously.
• Call to Action:
  • Support organizations committed to factual content.
  • Explore unconventional career paths that positively impact the world.

Additional Note

• Sponsor Mention: 80,000 Hours – free career advice for impactful work.
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