China · 78-139
Zhang Heng
Zhang Heng was astronomer, engineer, and mathematician. He worked on celestial models, instruments, calendar questions, and approximations involving pi.
Biographical and historical reference works document Zhang Heng’s role and the mathematical work summarized on this page.
3-5, 6-8, 9-12, College
The person and the work
Biography
Zhang Heng was astronomer, engineer, and mathematician associated with China. He worked on celestial models, instruments, calendar questions, and approximations involving pi.
He designed a seismoscope that converted ground motion into a directional mechanical signal. Together, these contributions connect fractions, ratios, and percentages, geometry and measurement, and trigonometry to the working problems, tools, and questions of the period.
Mathematical contribution
What this hero added or preserved
Core mathematical work
He worked on celestial models, instruments, calendar questions, and approximations involving pi.
Method, teaching, or application
He designed a seismoscope that converted ground motion into a directional mechanical signal.
Why this matters
The larger lesson
Zhang Heng shows that mathematics grows through proof, calculation, observation, design, teaching, or careful records. The lasting lesson is that fractions, ratios, and percentages, geometry and measurement, and trigonometry can turn a difficult question into a method another person can inspect and reuse.
Place the work in time
Timeline
- 78
Life and working period
Zhang Heng worked as astronomer, engineer, and mathematician in China.
- Legacy
Lasting mathematical connection
He designed a seismoscope that converted ground motion into a directional mechanical signal.
Key idea
Proportion preserves a relationship
Zhang Heng’s work connects quantities by ratio. Scaling both parts by the same factor keeps the relationship unchanged.
The ratio 5:7 scaled by 3 becomes 15:21.
Try it yourself
Scale a ratio
Scale the ratio 5:7 by a factor of 3.
- Multiply the first term by the scale factor.
- Multiply the second term by the same factor.
- Confirm that both ratios simplify to the same value.
Show the answer
The scaled ratio is 15:21.
Math at work
Engineers and architects use the same habits
Engineers and architects use fractions, ratios, and percentages to plan, compare, test, or communicate decisions. Zhang Heng’s work provides a historical example of that connection.
Keep curiosity alive
A little-known fact
He designed a seismoscope that converted ground motion into a directional mechanical signal.
Zhang Heng matters because of only one famous formula or anecdote.
The documented record is broader: He worked on celestial models, instruments, calendar questions, and approximations involving pi.
Keep exploring
Connected learning paths
Related math terms
- Ratio
- Proportion
- Percentage
- Angle
Practice these ideas
- Fractions & DecimalsWork with fractions, decimals, percentages, and conversions.
- Pre-AlgebraBridge arithmetic and algebra with integers, ratios, and equations.
- GeometryExplore shapes, angles, area, perimeter, volume, and classification.
- Advanced GeometryPractice coordinate geometry, transformations, vectors, and solids.
- TrigonometryUse angles, right triangles, radians, and trigonometric functions.