Q and A with the experts: The science of a Blood Moon

On March 13, 2025, the Moon will glow in shades of red and orange as it passes through Earth’s shadow during a total lunar eclipse, commonly called a Blood Moon. We spoke with Dr. Roan Haggar, a postdoctoral fellow and outreach coordinator at the Waterloo Centre for Astrophysics (WCA) at the University of Waterloo, to uncover its science and what to watch for in the night sky.

Why does the Moon turn red during a total lunar eclipse?

The term “Blood Moon” might sound scary, but it's just light from the Sun. A lunar eclipse can occur during a full moon, when the Moon is fully illuminated by the light of the Sun. However, if the Sun, Earth and Moon are aligned, the Moon can move into the Earth's shadow. As the Moon passes through this shadow, its light dims as the Earth blocks direct sunlight. However, longer wavelengths of light filter through Earth's atmosphere, casting red and orange hues onto the Moon and giving it that red glow.

How rare is a total lunar eclipse?

The Earth and Moon have regular orbits, which is how we can predict when and where an eclipse will occur. While a partial lunar eclipse can happen once or twice a year, a total lunar eclipse only occurs roughly every two years.

What time will the lunar eclipse happen in Ontario?

The Waterloo Centre for Astrophysics is collaborating with the Royal Astronomical Society of Canada to celebrate the lunar eclipse with a viewing party in Parking Lot E on Seagram Drive starting at 11:30 pm on March 13th, 2025. The total lunar eclipse will begin at 11:57 pm with totality starting at approximately 2:26 am.

• Penumbral eclipse (11:57 pm): The Moon will enter Earth’s penumbral shadow, dimming the Moon’s brightness.
• Partial eclipse (1:09 am): The Moon will move into Earth’s umbra, and a dark shadow will cast on its surface.
• Totality begins (2:26 am): The Moon will move fully into Earth’s umbra and will appear reddish-orange.
• Totality ends (3:31 am): The red colour will fade as the Moon moves out of Earth’s umbra. The Earth’s shadow will still be visible on the moon.
• Partial eclipse ends (4:47 am): The Moon will exit Earth’s umbra and will slowly brighten as it moves out of the penumbra.  
• Penumbral eclipse ends (6:00 am): The eclipse will end, and the Moon will return to its regular brightness.

Can I look at a total lunar eclipse with my bare eyes?

Unlike solar eclipses, it’s safe to observe a total lunar eclipse with the naked eye. No special eye protection is required!