Thread: The sun

Ancient cultures knew about the sun. These were the Sumerians, Babylonians, Egyptians, Chinese and Greeks. Greeks knew the most. Aristarchus knew that the sun was the center of the solar system and that the earth revolved around it. Copernicus' heliocentrism was a revival of an ancient Greek concept.

Albert Einstein understood that energy and matter are the same thing. Nature stores energy in matter, so when the sun converts mass to energy, light and heat are given off. The sun shines by fusion, the fusing together of hydrogen nuclei to form helium.

The sun influences everything on earth. Its nuclear fire is the source of life itself. No wonder the ancients worshipped it. To them, the sun was a god.

The sun and the earth are connected. The sun causes the Northern Lights when the solar wind hits the top of our atmosphere.

The sun changes. Global warming and climate change are caused by variations in the sun's output. Earth's climate is linked to the sun.

Galileo observed sunspots in 1610. Sunspots are caused by the sun's magnetic field. They appear dark because they are cooler than the rest of the sun's surface. The sunspot cycle is eleven years.

The sun helps us and hurts us. Sunlight produces vitamin D. It is a factor in photosynthesis. We see things because sunlight bounces off them. But the sun can produce painful burns and fry our retinas if we are not careful.

The sun is 93 million miles away. This distance is known as an astronomical unit (AU). The sun's surface temperature is 11,000 degrees. The temperature at its core is 27 million degrees.

The photosphere is the sun's bright surface. The corona is its atmosphere, seen during a total eclipse. Rays from the corona stream into space.

The sun formed 4.6 billion years ago from a nebula of hydrogen gas. The nebula's gravity caused it to shrink and spin. It became a sphere as its core heated up. Stars and planets become spheres because spheres have the smallest surface areas of all geometrical shapes. All their parts are the same distance from their centers. Heat is "atoms in motion," and hydrogen atoms at the sun's core collide and fuse together, creating helium and giving off heat and light. Fusion depends on there being enough mass to get things started. There has to be enough pressure at the sun's core.

When a star's hydrogen is gone, it burns helium to create carbon and oxygen. Silicon and iron are next. If the star goes supernova, spewing its elements into space, extreme temperatures create the heaviest elements. There are 92 natural elements. Bottom line: the elements are created inside stars. The iodine in our thyroid glands and the iron in our blood came from supernova explosions.

The electromagnetic spectrum is the range of all waves of radiation by length.

The sun gives off different kinds of radiation. We are affected most by infrared, visible light and ultraviolet (UV).

Electromagnetic Spectrum -
1 Radio - Long wavelengths. Radio telescopes study these waves from stars and galaxies.
2 Microwave - Used in microwave ovens.
3 Infrared - We experience infrared as "heat." The sun's heat is in the form of long infrared waves. Infrared telescopes such as the James Webb Space Telescope use infrared light. Infra means "below."
4 Visible light - Composed of colors.
5 Ultraviolet - Short, high energy waves. Ultraviolet waves burn the skin and cause cancer. Our atmosphere protects us from UV light.
6 X-Rays - Used in medicine.
7 Gamma rays - From explosions throughout the galaxy.

Spectrum of Visible Light -
1 Red
2 Orange
3 Yellow
4 Green
5 Blue
6 Violet

The sun plays a role in both solar and lunar eclipses. A solar eclipse happens when the moon passes between the earth and sun. It happens at new moon. There will be a solar eclipse in Indonesia on March 9, 2016. There will be solar eclipses visible from the United States on August 21, 2017, and April 8, 2024. It is these three eclipses that spurred my recent interest in the sun. If I travel to Indonesia in 2016, and to western Kentucky in 2017, my chances of seeing at least one cloudless sky will be pretty good. I will be 78 in 2024, and will see that eclipse also if I am alive and ambulatory. Any one location averages a solar eclipse every 300 years. It is the exception that Kentucky and Tennessee are getting two seven years apart.

It is pure coincidence that the sun and moon appear to be the same size. The sun is 400 times larger than the moon but 400 times farther away. These are the only two disks we can see with the naked eye. A billion years ago, the moon was closer to earth and appeared much larger. A billion years in the future, the moon will be farther away and too small to cover the sun. The age of eclipses will be over. As far as we know, our solar eclipses are the only phenomena of their kind in the universe. People gaze in awe as the sun and moon line up with the spot they are standing on. Those who have seen a solar eclipse agree that it is the best visual experience in astronomy.

Five billion years hence, the sun will become a red giant. It will expand beyond Earth's orbit as life ceases to exist on the planet. The sun will give off a ring-shaped cloud of gas something like the Ring Nebula, that dying star in the constellation Lyra. The sun will then shrink to become a white dwarf and finally a black dwarf.

Ok....what do you care to discuss?

He's discovered a Black Dwarf. A....

Maybe he has hyperthermia?

maybe these posts aren't particularly for discussion but more a way of getting the posters thoughts together. they get feed-back on whether they are on the right track or not.

or not.