The astronomical phenomenon that defies the shadows
On certain dates of the year, the Sun reaches its highest point in the sky, aligning perfectly over specific regions of the Earth. This event, called Shadowless Day or solar zenith, causes vertical objects such as poles, buildings or even people to stop casting shadows for a few minutes. A unique show that combines science and natural beauty.
How does this phenomenon occur?
The Shadowless Day occurs when the sun’s rays fall perpendicularly on the Earth’s surface. This is only possible in areas located between the tropics of Cancer and Capricorn, thanks to the inclination of the Earth’s axis (23.5°). At these latitudes, the Sun reaches its zenith position twice a year, creating an optical effect where shadows seem to evaporate.
Mexico, due to its privileged geographical location, is one of the countries where this event can be clearly seen. Cities like Mérida, Cancún or Mexico City itself become perfect settings to observe this astronomical phenomenon.
2025 calendar: key dates not to miss
In 2025, Shadowless Day can be observed on different dates depending on location:
- Mexico City: mid-May and between July-August (dates similar to 2024: May 17 and July 25)
- Regions near the Tropic of Cancer: dates vary between May and August, with greater intensity
Best places for observation
The cities with the best visibility are those closest to the Tropic of Cancer, where the phenomenon manifests itself most clearly:
- Mérida, Yucatán
- Cancun, Quintana Roo
- Tuxtla Gutiérrez, Chiapas
- Villahermosa, Tabasco
These locations offer ideal conditions to witness the exact moment when the Sun is positioned at its highest point, completely eliminating vertical shadows.
Preparations to observe the solar zenith
To fully enjoy this astronomical event, experts recommend:
- Find a clear place without vertical obstacles
- Verify the exact time of the phenomenon for each location
- Protect yourself adequately from solar radiation
- Use simple vertical objects (such as a stick) to better appreciate the disappearance of the shadow
This phenomenon is not only a visual spectacle, but also a practical demonstration of the Earth’s movements and its relationship with our closest star.
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