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Extremely Rare Transit Of Venus Occuring Tuesday

BOSTON (CBS) - It's an astronomical event that nobody alive today will ever get to witness again, and it is going on this evening!

Venus will be marking a path across the sun as seen from Earth.

There is only one problem for those in Southern New England: cloud cover will prevent us from seeing it. Only those in extreme North New England have a chance at seeing this rare and fascinating event, while the rest of us are stuck under a layer of stratus.

And there is no wait until next time with this event. The next Transit of Venus across the sun visible from Earth will not occur until the year 2117.

So, had the weather cooperated, what would we have seen? Something not just visually stimulating, but also something with major historical relevance in the science community.

At 6:03 p.m. tonight, we could have put on our special welders glasses or used a special telescope with a solar filter and watched a small black circle move slowly across the sun.

It actually takes more than six hours for the complete transit to occur, not ending here in Boston until after midnight.

So, it was never really ideal viewing here in New England, seeing that our show would have been over at sunset anyhow.

But, many folks around the globe, including locations such as Australia and Hawaii, will be lucky enough to see the full show.

What is even more interesting about this event is its relevance in our history of attempting to better understand our place in the Solar System.

Galileo and Johannes Kepler were the first to observe and predict this transit back in the 1600's. Then, in 1663, mathematician Rev. James Gregory theorized that we could figure out how far the Earth was from the Sun by observing the transit of Venus.

While it was a bit too complex at the time, a few hundred years later in 1882, astronomers were able to calculate the distance within about 50,000 miles (92,702,000).

You can read a more complete history on NASA's site.

So, at 6:03pm tonight, take a second to look skyward. Just beyond those gray clouds, a once-in-a-lifetime event will be unfolding. Perhaps if you close your eyes you can imagine its beauty!

You can follow Terry on Twitter at @TerryWBZ.

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