… and then seeing it again 10 years later is often a shock, but also sometimes a revelation. Things change, places are transformed, the new washes in–and if you look over a long enough period, you can see the planet change.

As an example, here’s a place that’s not far from my old work location from 2007:

Of course, this is California, so things change quickly. This is the same place 8 years later.

And this happens at larger scales as well. Here’s San Francisco in 1938:

And SF a 21 years later:

In the course of doing my research on various SRS Challenges, I’ve done a lot of looking for images at time X and then the same shot a few years later. But even after I’ve found them, the problem of comparing them is always problematic. I can sometimes put them up side-by-side, like this:

While that’s handy, it’s really hard to compare individual locations. I end up using two fingers to locate the same spots on both images, then flicking my eyes back and forth.

This leads me to ask you for help. Our Challenges this week are:

1. Is there any way I can make a web page that lets me have two pictures side-by-side and then have a slider that let’s me easily move a divider between one image and the other? (Here’s a mockup of what I’d like. In this illustration, you can click on the circle and drag the divider back and forth to see more of one image or the other.)

2. In this same vein, I’d like to see a nice time lapse of a place–ANY place. (You can probably find an aerial time lapse of any particular large city.) Can you find a worldwide tool that will let me see any place on the planet with a roughly 10 year timelapse view? I’m looking for something that will allow me to see this:

More particularly, can I get a time-lapse of other places? (Say, Antarctica, Tahiti, or the Canary Islands.)

So, class… we’re looking for tools this week. Can you locate these? (And are there other tools that can help us look at time-based images for comparison?)

And, if you manage to find a timelapse tool, what’s the most interesting place you’ve found?

As always, let us know HOW you found the answer (and, for this week), what’s the most interesting!

Search on!

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Addendum: Regular Reader Judith dropped me a note to say that there’s a bit more to the “floaters” story that I should have mentioned in our last Challenge. She wrote to me with a great comment:

“Floaters that appear gradually and are there all the time are nothing to worry about. However, if there is a sudden increase of floaters, it may be a medical emergency as this can be the sign of a retinal detachment.

Anyone who experiences an onrush of floaters should see an ophthalmologist immediately.”

Thanks, Judith. (I’m going to edit my original post to reflect this.)