Intentionally Lost: Size of the Sun

Saturday, June 9, 2012

Size of the Sun

Someone asked me about this photo:

(via NASA)

The question was: would the Sun really appear so large if you were standing on Venus? I knew the answer to that is no, but I have been guilty of wondering if it would appear that large if you were standing on Mercury. But again: the answer is no. So how big would the Sun be if you were on either planet? Below are some photos showing how the Sun would look from each one:

From Earth

From Venus

From Mercury (furthest; aphelion)

From Mercury (nearest; perihelion)

From Venus, the Sun would be a third larger (which really isn't that big a difference). Mercury follows are relatively more elliptical orbit, with the Sun appearing twice as big at its furthest and three times as big at its nearest. From Mercury the Sun is certainly much larger in the sky, but probably not nearly as big as you might have thought it would be.

So just how is it that the Sun is so big on those photos? I mean, the camera can't be really close to the Sun... because otherwise it wouldn't be able to also have Venus in that picture at the top of this post. So what if I was standing on a spaceship positioned at exactly where that photo was taken, in orbit above Venus looking toward the Sun? Why wouldn't the Sun appear exactly as big as it looks in that image?

And to that I answer: the Dolly Zoom- http://en.wikipedia.org/wiki/Dolly_zoom

The short of it is that as you zoom in on something: further objects grow larger at a faster rate than nearer objects, distorting the perspective. As you zoom in: your near object (Venus) only gets a little bigger, but your far object (the Sun) gets immensely bigger.

You've probably seen this before in the movies. One of the most prominent uses of the Dolly Zoom is in Hitchcock's Vertigo, but more recently there's a memorable effect in the first Lord of the Rings, where Frodo senses the Ringwraiths approaching along the forest path.

Since telescopes are just massive zoom lenses: the ever-distant sun can appear to loom massively about the planet. If you were to physically travel from Earth to Venus: you'd see Venus growing ever larger as you get close to it, but the Sun would pretty much stay the same size.

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Traveling Style

I prefer to travel solo as much as possible. It's not that I'm anti-social; it's just that I grew up an only child and so when I'm on holiday: I far prefer to do what I want to do. So I might join up with some others for a day, or perhaps meet up with friends here and there; but even if I'm traveling with friends, I'll still make efforts to break out on my own during the day.

Mountains are my dearest love, with beaches a close second. Combine the two and there's a dear winner. I also love to get off the beaten path, whether it means hopping marshrutka through the former Soviet Bloc, or just seeking out less-traveled areas of Western Europe.

I generally detest tour groups, though sometimes they're a necessary evil -- such as getting into attractions in Rome, or getting to protected areas such as glaciers or refuges.

When it comes to lodging: hostels and homestays are ideal; though I'll often splurge for a nicer stay at least once during the trip.

Disclaimer

I am first and foremost writing this for my own memory. Some entries are little more than travel logs which may only be interesting if you plan on going or have already been. Some are openings to the deepest workings of my mind: thoughts, rantings, and any variety of other scary mental products.

This write-up is geared toward everyone... and in doing so it could very well be safe for no one. The things that moms & grandparents may not want to know about may be exactly what my friends are prone to inquire about first. The whole way through, though, I'll at least try to keep it semi-clean, partially politically correct, and maybe even a tad entertaining.

Cheers!