Was that a ‘Super Sun’ we saw last week?

Beautiful Sunset!
Beautiful Sunset!

Houston, TX – A viewer’s email from last week prompts today’s blog:

Hi Mr. Billingsley: This evening (July 2, Thursday) the sun setting looked like a super moon as it got close to the horizon. It looked very large in relation to what it normally looks like when it sets. Why would this be? Is it based on the calendar so it happens at certain times in the year? It’s as if somehow it was closer to Earth than normal, which would be my guess.I appreciate any insight you may have. Thanks for always providing entertaining weather on the news!

Ken L., NW Houston

Thanks for the note, Ken! Believe it or not, the sun right now (and every July) is farther away from us than all year long. Or, technically, we’re farther away from the sun since we do the orbiting. This is called aphelion, as opposed to January’s closer distance, known as perihelion. Here’s an illustration from Time and Date:

Perihelion vs Aphelion

So you can see that in July we’re actually farther from the sun by an extra 3.1 million miles! It’s actually in January that you should be seeing a bigger sun on the horizon!

So What Made Ken’s Setting Sun Bigger?

The truth is, it’s not. The setting sun (and rising sun) seems bigger to our brain because it’s farther away from us than when the sun is right overhead (the zenith). But it’s the same size sun in both locations! Our brain creates the optical illusion to account for the distance. The moon rise does the same thing (if you’ve seen a moon rise you know what I mean). NASA shows us how this works. Look at the two yellow lines and you will think the one farther away is longer:

The farther away line looks bigger, but it's not!

But when you draw straight lines to connect the sides, the lines are the same length:

Look at that!

Here are the two photos side by side:

Side by side

So it’s easy to see here that even though the sun is the same size whether right above you or far away, it’s your brain pulling a fast one on you!


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About the Author:

KPRC 2's chief meteorologist with three decades of experience forecasting Houston's weather.