A recent episode of the beautifully produced video series "Shelf Life," from the American Museum of Natural History in New York City, explores how an archive of night-sky photographs is giving astronomers the closest thing to a time machine. Visitors to the American Museum of Natural History (AMNH) have no shortage of amazing things to see, and yet many are not aware that AMNH is an active research institute, and even more activity takes place behind the scenes. The captivating series "Shelf Life" gives the public a peek behind the curtain.

The fifth episode in the series, "How to Time Travel to a Star," is a great one for space fans. It explores how astrophysicists at AMNH are working to digitize a huge volume of night sky photographs spanning decades. With this archive, astronomers can effectively look back in time. [Amazing Photos of Star Birth]

The Harvard plate collection (so-called because the images were taken on glass plates) is an almost nightly record of the sky going back to 1890, according to the video. Looking at these photos, scientists can observe how stars and other objects have changed.

"In astronomy, things either happen almost instantaneously, or over tens of thousands, millions of years," Ashley Pagnotta, a postdoctoral fellow at AMNH, said in the episode. "But one of the things that we're starting to learn is that the things that we previously thought were constant over 100 years, we're seeing changes over decades — essentially the length of a human lifetime."

Researchers have already used the plate collection to make new discoveries about astronomical objects. The episode goes on to discuss how astronomers are digitizing this archive of images and information, and updating it for modern astronomy.

The entire "Shelf Life" series is an exciting look into the heart of this amazing museum. The debut episode gave viewers a brief look at just a few of the 33 million artifacts, fossils and other objects that are part of the museum collection, but only a fraction of which can ever be on display to the public at one time.

The series also introduces viewers to the people who are preserving and archiving these objects, and using them for research. The series makes these jobs seem absolutely romantic.

Much like the museum itself, the episode "How to Time Travel to a Star" is a wonderful blend of past, present and future: It shows viewers how astronomical images were recorded prior to the invention of digital cameras, and then demonstrates how both historical and modern sky images can help scientists learn new things about the universe.

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