Fall is upon us and so the seasons change.
But can you explain why the seasons change?
It is surprising how many people cannot accurately explain the reasons why our seasons change every year. In a famous short video Harvard graduates demonstrated how even very educated people often don’t understand basic science. When dozens of people after a Harvard graduation were asked to explain what causes the seasons many of them failed to identify the tilt of the Earth in its orbit as the cause of the seasons. Instead they demonstrated how lost they are in their own “Private Universes” when they attempted to provide various unscientific explanations for the seasons. For example: a large number tried to explain the heat of the summer and cold of the winter as being the result of the distance between the Earth and the Sun during various parts of Earth’s orbit.
Since the Earth is spinning this couldn’t possibly be correct. Wouldn’t the entire Earth, both North and South be the same distance from the Sun at any given time? Wouldn’t the daily spin of the Earth even out the heating for everyone? No, an explanation based on the distance from the sun fails to explain the uneven heating of the Earth and the reversal of the seasons between the Northern and Southern hemispheres.
In fact, it is the 23o tilt of the Earth that gives us our seasons. The tilt of the Earth compared to its orbit around the sun gives the Northern hemisphere a greater amount of sunlight in July and results in our Northern summer. At the same time, the smaller amount of daily sunlight
experienced by the Southern hemisphere during July results
in their Southern winter – at the same time as our Northern summer.
So remember what really causes the seasons the next time you notice the beautiful fall colors, the first snow of winter, the earliest bloom of spring, or the warmth of a summer’s evening. Ask your friends if they know what causes the seasons and discuss with them how neat it is that science can help us explain our world.
Did June 30th seem just a little longer than usual? Well, it actually was. It was exactly one second longer than a normal 24 hour day. If you were looking at the website for the National Institute of Standards and Technology (NIST) where the official time for the United States is kept on June 30 at around 7:00 p.m. (Eastern Standard Time or midnight GMT) you would have seen something very strange. As the time counted from 6:59 to 7:00 p.m. – just as it was about to change to 7:00 p.m. – an extra second occurred. The clock read 6:59:58 . . . 6:59:59 . . . 6:59:60 and then 7:00:00. One whole second was slipped in just before 7:00 p.m.!
Why did they do that? What’s going on? Did we slip into some sort of time warp?
Well, no. What they actually did was correct our clocks. It seems that our clocks gradually lose time because the Earth’s rotation is slowing down a little bit. This braking of the Earth’s rotation is mostly caused by the Moon as tidal friction slows down the spin of the Earth. Consequently our days get a tiny bit longer every day.
Atomic clocks are almost one million times more accurate at measuring time than the old fashioned method of measuring time using the Earth’s rotation. The variation in earth’s rotation can be caused by more than just the moon, however. Major Earthquakes, the melting of ice caps, and even gigantic building projects like the filling of China’s Three Gorges Dam can all change the speed of rotation of the Earth. Consequently, if official time keepers didn’t correct our clocks every now and then noon might eventually switch places with midnight. Also other things that require absolute precision in time keeping like stock markets and GPS could begin to have growing difficulties. However, a growing number of concerned scientists are beginning to complain that we should quit playing with time and just skip future leap seconds as we simply adjust over thousands of years to the natural slowing of the Earth.
I think our Beautiful blue planet may have been mis-named. With over 70% of the Earth’s surface covered by water maybe we should have called it the planet “Ocean” (or Oceanus)? Either way it would probably have been more accurate.
And as flat as the horizon may look in this picture of the Atlantic, these huge blue oceans are constantly moving as a result of wind, weather, heat, and gravity. Here you can see a part of the Rhode Island coastline at low tide.
Tides are the rising and falling of the water level in the ocean. Tides are caused by a complex interaction between the movement of the Earth and the gravity of the Sun and the Moon. The moon has the single greatest effect on the tides since it is so much closer than the Sun. As the water levels rise and fall, a lot of water gets moved around the planet causing enormous tidal currents. Many places, like New England, have semidiurnal tides. This means they get two high tides and two low tides a day. The typical tidal range in this area is about 3-4 feet which means at high tide most of these rocks will be covered by the ocean.
So if you plan to visit the sea shore, you better keep an eye on the tide or you might just end up getting all wet!
Did you know that there are over 1500 active volcanoes around the Earth? Many are located in the “Ring of Fire” surrounding the Pacific’s Rim. There are amazing pictures and videos of active volcanoes that you can see at VolcanoLive.com.
The Villarica Volcano (Pucon, Chile) 3/2015
You can also see the connection between Earthquakes and Volcanoes by looking at the Interactive Volcano and Earthquake Map.
Check it out!
On Friday, a 4.8 magnitude earthquake occurred in Nevada shaking buildings and roadways throughout Las Vegas. With another significant earthquake in the news this weekend, I thought I would add a further post about our shaking earth.
It’s interesting to see where earthquakes strike each day. A great website that plots all the latest earthquakes around the world can be found at http://earthquakestoday.info/.
The website has an excellent, up to date, zoom-able map that shows exactly where each large quake in the last 7 days has occurred. Take a look and see where the closest earthquake to you occurred.
If you really enjoy keeping track of our constantly shaking earth you can even download some interactive apps for your smartphone. These apps will keep you informed with all the latest information whenever a quake strikes anywhere around the world. I personally enjoy the app “My Earthquake Alerts”. (But you may have to be careful when setting the Magnitude Notification Setting because if you set it too low, your phone will be giving you alerts constantly.)
You may have noticed a lot of news reports about earthquakes lately. People forget that earthquakes are actually very common.
The USGS (United States Geological Survey) estimates that several million earthquakes occur around the world each year. Many go undetected because they hit remote areas or have very small magnitudes. We just had a noticeable earthquake about two weeks ago around 35 miles from where I live. It was only about a 4.2 on the Richter scale – so it didn’t cause any significant damage but it was noticeable. If you want to see an explanation of the Richter scale look here.
As more and more seismographs are installed in the world, more earthquakes can be and have been located. However, the number of large earthquakes (magnitude 6.0 and greater) has stayed relatively constant each year.
We strive to make learning science fun! Tom Hunt, ClubScientific’s Science Guru, will be posting here throughout the months a head. We hope you enjoy them! Stay tuned.