By the calendar, Spring in the Northern Hemisphere began on 21 March. At our house, we heard the first robins singing on 27 February. Snow is still possible in Colorado for a few more months, but the air temperatures are, on average, getting warmer. The trees are leafing out.

On the GLOBE web site, you can see some reports of budburst. These reports should creep northward in the Spring in the Northern Hemisphere. Similarly, you might also look for how far north the Rubythroated Hummingbirds have gone (also see www.rubythroat.org). Most importantly, look for other signs of Spring’s arrival (or Autumn’s arrival) at your home or school. From my time working in the tropics, the biggest changes seem to have to do with rainfall.

Want to see the seasons from space? A recent issue of EOS, which is published by the American Geophysical Union, points to a web site — bluemarble.nasa.gov, where you can do just that.

I found it most interesting to compare the winter image to the summer image. Looking at where I live, in the west-central United States, the ground appears brownish when there is no snow. This fits with what I saw outside. The grasses were dormant, and the trees had lost their leaves. In the summer, the same area is green, because the satellite, like us, “sees” the leafed-out trees and green grasses. How do things change where you live? How does it compare to what the satellite image shows?

These images are from the Terra MODIS (MODerate-resolution Imaging Spectroradiometer), and they have a resolution of 500 meters. This is big enough to see a big lake, but not a football field. Before the images could be produced, the effects of clouds, dust, haze, and even the air between the satellite and the surface had to be removed.

Happy Earth Day!

You don’t have to find dinosaur tracks to practice a little science.  Just look outside and see if you can explain what you are seeing.  Don’t make it too hard.  And don’t worry about observing something for the first time.  If it is your first time, you can solve your own mystery.  Here’s an example.

My husband and I take a walk around sunrise every day.  There are mountains to the west of where we live.

One morning a few months ago, we noticed five crows flying from the foothills toward the Sun.

Then we noticed that it happened almost every day.

Our question:  “Why do crows fly from the west toward the Sun every morning?”

In this case, we talked to a person who knew a lot about birds.  He said that crows roost in the mountains at night, and then fly east into the city during the day.

Do you have any ideas about why the crows would fly into the city during the day?

We noticed this behavior during the winter.   We will be watching to see if the crows do this during the summer as well.