3rd From Sol

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Solstices and Sunshine In North America

01 Wednesday Dec 2021

Posted by Paul Kiser in Astronomy, Daylight Saving Time, Science, solar, Space, United States

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Earth tilt, life on earth, seasons, solar heating, solstices, summer solstice, winter solstice

We know that solstices are different. It’s colder around the winter solstice and warmer around the summer solstice. We also know that the days are shorter and the Sun is lower in the sky during the winter¹ and that in the summer the days are longer and the Sun is higher in the sky.

[¹In higher latitudes both north and south.]

Afternoon Sun at the Winter Solstice (2019 Reno, Nevada)

People with a high school education probably know that the seasons have to do with the tilt of the Earth’s axis and its orbit around the Sun. And every year, people living north of 30° north latitude or south of 30° south latitude also experience the differences between the summer and winter solstice.

But what does it look like?

Solstices From the Sun’s Perspective

Most of humanity has experienced the solstices from one perspective: standing on the Earth. Astronauts have been able to see Earth from a different perspective, but even they don’t have an immediate comparison of the summer and winter solstices because there is a six-month time lag between them.

Fortunately, we can use a globe and a flashlight to help us visualize the difference between the summer and winter solstice from the Sun’s perspective. Using San Francisco, California, USA as our focal point, we can see how the angle of the Sun’s radiation differs between June and December in the northern hemisphere.

Solstices Sunrise

I’ve used my son’s Kylo Ren figurine standing on the San Francisco Bay area to mark the place on the globe. It should be noted that at this scale, Kylo Ren would be twice the height of the orbit of the International Space Station (ISS).

In Images 1a and 1b, it may not be obvious what is different between the winter and summer solstices; however, in the winter, the Sun is directly over South America as the Sun rises in San Francisco. In the summer, the Sun has yet to reach the South American coast.

What is apparent is that at sunrise in San Francisco, the Sun’s angle is from the east in the summer, and in the winter, the Sun’s angle is from the southeast. 

Image 1a –                       Winter Solstice Sunrise

Image 1b –                   Summer Solstice Sunrise

 

 

 

 

 

 

 

 

[NOTE:  A flashlight does not accurately demonstrate the Sun’s light on the Earth. The light of the Sun reaches farther around the curvature of the Earth. Also, the camera is slightly to the right of the light source in these images.]

High Noon

At the point when the Sun is highest in the sky, the difference in solstices is more apparent. In the summer, the Sun is nearly directly overhead but in the winter the Sun is low in the southern sky for North America. [SEE: Images 2a & 2b]

During the winter, people in the United States may find that the Sun is directly in their eyes when facing south. We tend to connect the wearing of sunglasses in the summer, but for people driving in a southerly direction during the winter, the glaring Sun may necessitate sunglasses.

Image 2a –                          Winter Solstice Noon PST

Image 2b –                     Summer Solstice 1 pm PDT

 

 

 

 

 

 

 

 

Arc In Daylight

The visual that may be best at showing the difference in the solstices is the arc of daylight experienced by a person in winter and summer. The path a person follows in San Francisco during the winter is less than two-thirds the length of the path during summer.

Most of North America crosses the fringe of the solar exposure in the winter while the summer offers a day that is two to three hours longer than on the equator. All this may seem obvious but the differences in the solstices is something that is easier to see modeled than experienced as a passenger on Earth.

Image 3a-b                                                                                        Solstices Arc of Daylight for San Francisco, California

Ten Reasons There is Life on Earth

21 Wednesday Mar 2018

Posted by Paul Kiser in All Rights Reserved, Astronomy, Exploration, Global warming, Green, History, Life, NASA, Nevada, Reno, Science, Space, US Space Program, Water, Weather

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axial tilt, conditions for life, Earth, exoplanets, Goldilocks Zone, habitability, habitable planets, life, life on earth, Milky Way galaxy, Moon, planet, planets, Sun, temperature, water

As scientists are finding more planets orbiting other stars it is becoming more of a reality that we are not alone in the universe. We may never be able to contact or observe life on other planets, but no one can deny the possibility that life might take root these islands in space. Still, it is important to remember that life on Earth is due to special circumstances.

Ten Factors Required For Life On Earth

A planet orbiting a star does not necessarily result in the development of life. On our planet, we have at least ten factors that allowed life to develop.

1. Not Too Close to Other Stars (Location, location, location)

If our solar system was located near the center of the Milky Way Galaxy, life probably would not have been able to develop on Earth. Stars are dangerous. They do bad things including spitting out radiation that destroys the basic structures of complex life. A planet in a solar system with other stars in the neighborhood is asking for trouble.

2. Our Sun is Special

Life on any planet requires a star, but not just any star will do. Size matters in the development of life. So do the qualities of the star. Our Sun is bigger than most, but still it is a relatively small, stable star and it’s been that way for over four and a half billion years. It will be stable for about another 5 billion years. It also has a treasure of heavy elements that are necessary for planet formation. Without planets, there is no life.

Life around stars of different sizes are possible, but our Sun seems to be about the perfect size for the development of life. In addition, our Sun is 85% brighter than the rest of the stars in the Milky Way, which has been vital in ‘powering’ our planet.

3. A Star’s Habitable Zone

Planet hunters and the media have made a major issue out of the concept of the ‘Goldilocks Zone.’ This is the area around a Sun where a planet is not too close, nor too far away. It is an important aspect of the potential for development of life on a planet, but it is only one factor of many. For Earth, we are resting in the orbit that is just right.

4. Moon

It’s hard to overstate the importance of the Moon for the development of life on Earth. First, the Moon was likely formed in a collision when a small planet-sized object hit Earth and tilted our axis (more on this later.) In addition, the Moon has slowed the Earth’s rotation down (more on this later,) and helped enhance the tidal movement of the Earth’s oceans. The Moon has played an important role in human activity, but just as an important role for all our planet’s species.

5. Size of the Planet

Again, size matters. If a planet is too big and the gravity will inhibit the formation of larger, more complex molecular organic structures. Too small and there can be no atmosphere. Earth is in the zone.

6. Axial Tilt

If Earth’s axis was perpendicular to the plane of the solar system the Sun would heat up the equator creating a zone too hot for most life forms. The poles would have minimal solar heating and would be extremely cold. In between would be the combat zone between hot and cold. Constant violent storms and wind would batter the mid-latitudes.

The tilt of the Earth causes solar heating to warm one hemisphere and allows the other to cool down. Every six months the warm/cool cycle swaps hemispheres. This creates storm systems in both hemispheres, but they act to distribute the warmth more evenly. The tilt of Earth’s axis is almost perfect for nurturing life.

7. Length of Day (spin)

We take the 24 hour day for granted. We shouldn’t. Last year Takanori Sasaki, a planetary scientist with Kyoto University, pointed out that the Earth originally spun so fast that its ‘day’ was only four hours long. Multicellular life didn’t develop on Earth until the day was 23 hours long. It’s is not clear at what point a planet’s rotation makes it habitable, but it seems obvious that a planet’s spin is a factor in the possibility of life formation.

8. Atmosphere

It may be obvious that an atmosphere is required for the development of life, but there are qualities to an atmosphere that are also required. The atmosphere cannot be too thick or too thin. It has to consist of an oxidizer, such as oxygen, to promote chemical reactions in cell structures. There is more to Earth’s air than just air.

9. Liquid Water

Water is necessary for all life that we are aware of, even though it is more important to some species than others. Liquid water is even more important to life than water vapor or ice. It is not an accident that the development of life happened on a planet where 71% of the surface is covered with liquid water.

10. Continent to Ocean Ratio

It’s not obvious, but life on Earth has been helped by the ratio of land to ocean. Land tends to have more temperature variance than the oceans between summer and winter. Land that is not covered in ice or vegetation absorbs much more heat in the summer. If most of our planet consisted of continents, the temperature change from summer to winter would be more dramatic, and less friendly to life.

Earth is Unique, Not Rare

Life on Earth was not an accident, nor is it divine. The conditions that led to the development of life here must exist on millions of planets, but there are an estimated 100 billion planets in the Milky Way Galaxy alone. We are unique, but we cannot be alone. Give life an opportunity and it will seize it.

Other Pages of This Blog

  • About Paul Kiser
  • Common Core: Are You a Good Switch or a Bad Switch?
  • Familius Interruptus: Lessons of a DNA Shocker
  • Moffat County, Colorado: The Story of Two Families
  • Rules on Comments
  • Six Things The United States Must Do
  • Why We Are Here: A 65-Year Historical Perspective of the United States

Paul’s Recent Blogs

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  • Road Less Traveled: How Craig, CO Was Orphaned
  • GOP Political Syndicate Seizes CO School District
  • DNA Shock +5 Years: What I Know & Lessons Learned
  • Solstices and Sunshine In North America
  • Blindsided: End of U.S. Solar Observation Capabilities?
  • Inspiration4: A Waste of Space Exploration

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