Archive for the 'Weather & Sky' Category

Dec 21 2016

Solstice

Winter sunset at Kuznetsk Alatau, South Siberia (photo from Wikimedia Commons)

Winter sunset at Kuznetsk Alatau, South Siberia (photo from Wikimedia Commons)

By the time you read this, the winter solstice will have passed.

The sun paused it’s southward journey today at 5:44 AM Eastern Time and is already moving north.

Soon the days will be getting longer and the birds will begin to sing.

Listen for the song sparrow.  What day will he sing his first song?

 

(photo from Wikimedia Commons. click on the image to see the original)

One response so far

Dec 17 2016

Variably Icy

Icy path in Schenley Park, Feb 2015 (photo by Kate St. John)

Icy trail in Schenley Park, Feb 2015 (photo by Kate St. John)

Snow, sleet, rain, freezing rain.

From 5 degrees F on Thursday night to 53 degrees with freezing rain today, we’ve had it all.  And there’s more to come.  Tomorrow night will be 15 degrees.

This yo-yo weather reminds me of what we learned during the polar vortex in January 2014:  Climate change is making the jet stream wobble so we get shots of very cold air and then warm air soon after, as shown in drawing(c) below.

Jet stream Rossby waves (graphic from Wikimedia Commons)

Jet stream Rossby waves (graphic from Wikimedia Commons)

 

Be careful today!  It’s variably icy out there.

 

p.s. I’ve used an old photo of ice because it’s too icy to step outside this morning!

(photo by Kate St. John.  Drawing from Wikimedia Commons; click on the image to see the original)

3 responses so far

Dec 16 2016

Uh Oh! Blue Light Isn’t Better

 

Uh oh!  Blue light, though bright, isn’t better at night.

As cities switch from incandescent or mercury street lights to LEDs they’re saving electricity and money and providing more light.  But brighter isn’t better if it’s blue.

The video above shows how the color temperature of light matters to our eyes and sleep patterns.  Though the video doesn’t mention it, the color also matters to birds and animals.

It’s possible to buy yellow-toned LEDs but blue, because its bright, has been the default choice for city lights.  We didn’t know that color mattered when the world began switching to LEDs and the bulbs have such a long life it’ll be decades before it’s time to replace them.  Meanwhile humans, birds and animals will be coping with the change.

It makes me want to close my eyes.

 

(video by TOMO news on YouTube)

p.s. Here’s a really helpful video showing the difference between incandescent, compact fluorescent and LED light bulbs in home use (the A19 screw base).  You’ll also see the inside of an LED bulb. I was surprised to learn it’s a tiny computer.

4 responses so far

Dec 09 2016

In 4 Billion Years

Published by under Weather & Sky

 

If you’re planning to be here four billion years from now you’ll see an amazing slow-motion sky show when two galaxies collide — Andromeda and our own Milky Way.

What will the sky look like when that happens? (very amazing!)

Will it be dangerous for Earth?  (probably not)

How many years before this happens?

Billions and billions.

 

(video posted in June 2012 by SpaceRip on YouTube)

One response so far

Dec 02 2016

How We’ll See The Stars Again

In my blog two weeks ago, the night sky video Lost in Light made me wonder how we’ll ever see the stars again.

Since then I’ve learned that our outdoor lights waste money and energy, disrupt wildlife, and ruin our own sleep patterns.  What we can do?

The video above from McDonald Observatory shows a simple answer.  Use lampshades.

The quick demonstration below shows why.

 

Right now our cities and towns are switching out incandescent street lights for LEDs.  It’s the perfect time to put on lampshades.    You can shade your home lights, too.

 

p.s. Stay tuned for a future blog about blue light versus red spectrum LEDs.  Yes, the color matters.

(videos from McDonald Observatory and darksky.org)

4 responses so far

Nov 18 2016

We Cannot See The Stars

Published by under Weather & Sky

 

Have you ever seen the Milky Way?

That question would have been absurd 200 years ago because billions of stars were visible on every clear night.

But now with the prevalence of artificial outdoor light most of us cannot see the Milky Way and many children don’t know what it is.

Because of this, some ancient stories don’t make sense.  In Genesis Abraham worried that he had no heir but God reassured him, “Look up into the sky and count the stars if you can. So many shall your descendants be.”   Today we look at the sky and count 50 stars, not realizing that Abraham was overwhelmed.

So what are we missing?  Sriram Murali traveled in California recording time-lapse video of the night sky in places with high light pollution (San Jose) and almost no artificial light (Death Valley).

His video let’s us see the sky as our ancestors did.

Watch the stars come out.

 

(video by Sriram Murali)

10 responses so far

Nov 11 2016

Spring Tide In November

Spring tide Wimereux, France, Sept 2007 (photo from Wikimedia Commons)

Spring tide at Wimereux, France, Sept 2007 (photo from Wikimedia Commons)

Despite the fact that it’s autumn we’re going to have a spring tide next week.

In this case the word “spring” has nothing to do with the season.  Instead it means the ocean will be “springing up” in the highest high tide.

Spring tides occur a day or two after a full moon and are highest when the moon is closest to Earth at perigee.  On Monday the moon will be full and at its closest perigee since 1948.   Watch for nuisance flooding on Tuesday in low-lying coastal communities.

Perigee also makes the moon look larger, an effect called the supermoon.  Here are two photos of the full moon in 2007, perigee on the left on October 26, apogee (furthest) on the right on April 3.

Size comparison of full moon at perigee versus apogee (image from Wikimedia Commons)

Size comparison of full moon at perigee versus apogee (image from Wikimedia Commons)

The difference is about 30,000 miles.  Closer objects look larger.  (Duh!)

If you miss this supermoon you’ll have to wait 18 years for it to be this close again.

Read more about November’s supermoon and spring tide at earthsky.org.

 

(images from Wikimedia Commons. Click on each one to see its original.)

One response so far

Oct 29 2016

First Killing Frost?

Published by under Weather & Sky

Frosty leaves (photo by Dianne Machesney)

Frosty leaves (photo by Dianne Machesney)

In the olden days the first killing frost in Pittsburgh usually occurred by Halloween and we had to wear winter coats over our costumes while trick-or-treating.  … I always hated to cover my costume.

This year has been very warm, even hot.  Only ten days ago it felt like August and today the temperature is 5-10 degrees above normal.  When will we experience the first killing frost?

Some of you already have.  If you live east or north of Pittsburgh the growing season is shorter (bluer), as shown on the USDA Plant Hardiness Map below.  Bradford, Pennsylvania is three growing zones colder than Pittsburgh and the Monongahela and Ohio Valleys.  I’ll bet they’ve had a killing frost.

Pennsylvania within the USDA Plant Hardiness Map retrieved October 2016 (map from USDA)

Pennsylvania within the USDA Plant Hardiness Map retrieved October 2016 (map from USDA)

 

Here in Pittsburgh the weather forecast says we won’t dip near freezing for the next several days.  Today it’ll be 10 degrees above normal.

When do you think we’ll have our first killing frost?

 

(photo of frosty leaves by Dianne Machesney, excerpt from USDA Plant Hardiness map at USDA.gov)

2 responses so far

Oct 24 2016

The Days Are Getting Longer

Published by under Weather & Sky

Earth rotating on its axis (animation from Wikimedia Commons)

Earth rotating on its axis (animation from Wikimedia Commons)

 

The days are getting longer.  Really.

Though daylight is decreasing as we head into winter, the length of an Earth day is increasing overall. That’s because Earth’s rotation is slowing down due to tidal forces between Earth and moon, post-glacial rebound, and sea level rise.

The effect is too tiny to see.  It takes 100 years for the day to gain 1.4 milliseconds.  To put that in perspective, a day was 23 hours long for the dinosaurs and is close to 24 hours now.

The only way we can measure Earth’s rotation is by using an array of instruments stationed around the globe (VLBI) that precisely record their first sighting of certain quasars. We then crunch the data to arrive at the length of a day and add a second to our atomic clocks when necessary.

Want to learn how we measure a day?  See the video about quasars at this NASA link.

 

(*) Quasars emit radio waves so they aren’t actually seen, they’re heard.

(animation of earth’s rotation from Wikimedia Commons. Click on the image to see the original)

No responses yet

Oct 23 2016

Remnants Of An Explosion

Published by under Weather & Sky

Cygnus Loop Nebula in UV light (photo from NASA via Wikimedia Commons)

Cygnus Loop Nebula in UV light (photo from NASA/JPL-CalTech via Wikimedia Commons)

Something really big exploded 5,000 to 10,000 years ago and this is what’s left.

The Cyngus Loop or Veil Nebula is the dust and gas left over when a supernova exploded in the area of the Cygnus constellation.  The explosion was so bright that people could see it naked eye.

But they didn’t write about it.  The first written language was invented by the Sumerians 5,200 years ago, probably too late for anyone to mention a temporary bright spot in the sky.

Nowadays the remnants are too dim to see without a telescope and some sections such as the Witch’s Broom have been named separately.

The entire Veil, above, isn’t visible except in the ultraviolet range.  If we could see it we’d be impressed.  It’s six times the size of the full moon.

 

p.s. Many birds can see light in the ultraviolet range, so this is probably what the Veil looks like to them.

(ultraviolet image of the Cygnus Loop Nebula by NASA/JPL-CalTech via Wikimedia Commons. Click on the image to see the original)

One response so far

Next »