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Cosmic Expansion, The Eiffel Tower Grows, & Sleep Tracker Truths
The Point by Modern Sciences - December 3, 2025
Don Smith
December 03, 2025
By The Modern Sciences Team | December 3, 2025 |
Say “hello” to December, Cultivators of Curiosity!
Welcome to the 48th volume of The Point by Modern Sciences!
In this edition, we traverse the scales of magnitude—from the vast expansion of the cosmos to the physics of a Parisian landmark, and finally, to the biology on your wrist. We examine how the latest data from the James Webb Space Telescope is settling a major debate in physics, uncover the thermal phenomenon that causes the Eiffel Tower to change size with the seasons, and breakdown the actual efficacy of the technology monitoring your rest. Read on to discover how our understanding of the universe, our engineering, and our health is becoming more precise.
SPACE
New Data from James Webb Space Telescope Settles Disagreement on Universe's Expansion Rate
New advanced telescope measurements have refined the Hubble constant to 70.4 km/s/Mpc, reducing previous discrepancies about the universe’s expansion rate. This result supports the current Standard Model and suggests that the earlier mismatch was not evidence of new physics. Enhanced precision and clarity from the James Webb telescope were key in resolving long-standing uncertainties in cosmology.
The Point:
A refined cosmic measurement: New results from JWST and Hubble reveal a Hubble constant of 70.4 km/s/Mpc, narrowing the gap between early- and late-universe estimates and reducing tension with the Standard Model.
Sharper tools, more precise answers: JWST's improved sensitivity allowed astronomers to measure stellar brightness through cosmic dust with unprecedented precision, improving distance calculations based on supernovae.
Implications for dark universe puzzles: The updated measurement suggests no need for new physics in the Hubble constant debate, redirecting attention away from it as a source of insight into dark matter or energy.
ENGINEERING
The Eiffel Tower gets bigger every summer – here’s why
The Eiffel Tower is not a static structure—it actually grows taller in the summer heat. Due to a scientific phenomenon called thermal expansion, the iconic Paris landmark can increase in height by up to 15 cm on the hottest days. Discover the science behind how its iron framework expands and even leans away from the sun, effectively turning it into a giant thermometer.
The Point:
Material and Structural Design: The Eiffel Tower was constructed from puddled iron, a material selected for its high stress resistance and low density, which enabled the creation of its iconic and wind-resistant triangular lattice structure. This design maximized height while minimizing weight, making it an engineering feat of its time.
Principle of Thermal Expansion: The tower's height varies due to thermal expansion, where materials expand as temperature increases because of greater atomic agitation. The extent of this vertical growth is determined by the tower's height, the temperature fluctuation, and puddled iron's specific coefficient of expansion, which is approximately 12x10⁻⁶ per degree Celsius.
Observed Physical Changes: This expansion results in a measurable height increase of up to 15 centimeters during peak summer heat compared to cold winter days. Additionally, differential heating from solar radiation causes one side to expand more, inducing a slight but observable lean in the tower away from the sun's position.
TECH
How do sleep trackers work, and are they worth it? A sleep scientist breaks it down
How accurate is your smartwatch's sleep tracker really? This article examines the science behind wearable sleep tracking, from the sensors employed (such as accelerometers and PPG) to how their data aligns with gold-standard laboratory studies. Discover how these devices measure sleep stages and learn just how reliable that nightly report on your wrist actually is.
The Point:
Wearables offer convenience with trade-offs: Consumer sleep trackers use movement and heart rate sensors to estimate sleep and stages, offering accessible data but lacking the precision of gold-standard polysomnography.
Validation studies show mixed accuracy: While most devices detect sleep with over 90% accuracy, they are less reliable in identifying wakefulness and sleep stages, with stage accuracy ranging from 53% to 60%.
Useful for trends, not diagnostics: Sleep trackers can support healthy routines and long-term awareness, but they are not substitutes for clinical evaluation and may worsen anxiety for some users.