ICU2: The Heretic

How do we know our place in the universe?

Parallax.

Try this: Take a camera outside on the night of October 14. Locate the Big Dipper (if you live in the Northern Hemisphere) or the Southern Cross (if you live south of the equator).

Find the same constellation with your camera on the night of July 14 (when the Earth is on the exact opposite side of the sun from where it was on Oct. 14.)

Try to align your camera to the STARS exactly as you did before. Snap a photo.

Print negatives of both images onto transparent slides (negatives can be created in any decent editing program [like Photoshop]).

Now, if you place the slides side-by-side (left and right) and cross your eyes (so that the stars on the left are EXACTLY merged with the stars on the right), you will see an amazing effect...some of the stars will seem to levitate above the slides, while others will seem to recede into the distance. (If you have trouble seeing this effect, try the Magic Eye practice page to help you).

While this is a crude way of explaining how scientists know the various distances to the stars...it is essentially the same process scientists use to judge the distance to various stars.

BTW, I once purchased a set of 3-D glasses (the kind for watching 3-D movies) to help see this effect more clearly.

As a precaution, you should never use this cross-eyed method of staring at a pair of images for too long, or immediately before driving a motor vehicle. It can alter your regular depth-perception in potentially disastrous ways.

I personally have a lot of trouble seeing the effect anymore because I experience Nystagmus from Multiple Sclerosis. Most of the time the world looks to me like I stared cross-eyed at a Magic Eye picture for too long.

Author's Addendum: I was mistaken about the dates for doing this correctly, mainly because I was trying to do the math in my malfunctioning brain. The best pair of dates would be April 14 and October 14. Clearly, I'm trying to select dates when the weather will be most agreeable, AND THE EARTH IS AT THE MAXIMUM DISTANCE FROM THE PREVIOUS LOCATION to offer genuine perspective on nearby stars. But select dates 6 months apart that work best for you, keeping in mind the weather.