Give me the splendid silent sun with all his beams full-dazzling!
Sol and the Earth (and all the other planets) are the same age. They were formed simultaneously when a cloud of hydrogen molecules collapsed about 4.5 billion years ago. Most of the matter collected into the centre to form the sun, while the rest was squeezed into an orbiting disk out of which the planets, moons and asteroids gradually formed. Because both star and disk moved in an anti-clockwise direction all the planets still orbit Sol anti-clockwise and all but two – Venus and Uranus – spin in the same direction. It's thought that collisions with asteroids reversed the direction of these two planets' spin.
It is an improbable coincidence that the sun and the moon, so totally different from one another in terms of their size and distance from the earth, appear to be exactly the same size – but this is exactly what makes a total eclipse of the sun possible. This happens because of the matching proportions: the sun is 400 times bigger than Luna (the astronomical name for the Moon) but also 400 times further from the Earth.
In 1999, after an eclipse over England, doctors at eye hospitals treating people who had looked at the sun could tell when during the eclipse the patient had looked at the sun – the sickle-shaped swelling on their retina was the same as the uncovered part of the sun they'd looked at.
Isaac Newton once gazed for as long as he could bear at the sun's reflection in a mirror, repeatedly turning to a dark corner of his room to see what spots and colours floated in the darkness as an after-image. After this he shut himself up in a darkened room to wait for full sight to return. It took three days.
The Sun, or 'Sol', makes up 99.8% of the mass of the solar system; all the planets and asteroids added together only account for 0.2%. Its surface is 3,000 times cooler than its centre which is 16.7 million degrees Celsius. This is the temperature of an exploding hydrogen bomb; it is hot enough to sustain the thermonuclear reactions that convert hydrogen atoms into helium, thus powering Sol. In this way Sol consumes about 5 billion kilograms (5 million tons) of its nuclear hydrogen fuel every second. This amount of energy per second is equivalent to 35 million times the annual electricity consumption of North America.
Sol is 1.3 million times bigger than the Earth by volume (109 times by diameter) and at 93 million miles distance, its rays take just eight-and-a-bit minutes to reach us. Despite these mind-boggling figures, Sol is an average-to-small star, known as a yellow dwarf, only half way through its life. Close neighbour Betelgeuse (one of the constellation Orion's 'shoulders') is 700 times bigger by diameter and 14,000 times brighter. Sol is only one of 100 billion stars in the Milky Way, which is itself just one of an estimated 125 million galaxies in the observable universe.
The sun is an almost perfect black body, which sounds strange until you know that a 'black body' is defined as something that absorbs any radiation that falls onto it. In other words, the sun doesn't reflect. However, it still emits electromagnetic radiation. The hotter the black body, the shorter the wavelength of light emitted (in the same way that metal, when heated, goes from red hot to white hot).
A difficulty is a light. An insurmountable difficulty is a sun.
The Chinese for a solar eclipse is Ri Shi or 'sun-eat'.
On average, it takes about 100,000 years for a photon to travel from the sun's core to the surface. High-energy photons are created in fusion reactions at the core, but within a few millimetres they get absorbed by solar plasma and then re-emitted in a random direction – in effect, the light bounces around inside the sun as it gradually works its way towards the surface, and it may take anything from 10,000 to 170,000 years for an individual photon to escape. When it does so, however, it zooms away at 300,000,000 meters per second, reaching the Earth in about 8 minutes and 19 seconds.
The sun has been around the centre of the galaxy twenty times so far.
The Earth reaches 'perihelion', its closest point to the sun in its yearly orbit, in January. This is mid-winter in the northern hemisphere, but the seasons have nothing to do with Earth's elliptical orbit. The difference between aphelion, when it's furthest away, and perihelion, is only about 5 million kilometres (3.3%), which is too small to have a noticeable effect.
The seasons occur because Earth's axis is tilted to its orbital plane by an angle of approximately 23.5°. Thus, at any given time during summer or winter, one part of the planet is more directly exposed to the rays of the sun. This exposure alternates as Earth revolves in its orbit. Therefore, at any given time, regardless of season, the northern and southern hemispheres experience opposite seasons.
The first person to reason that the tropics were not hotter because they are nearer the sun, but because a smaller area is lit by an equal amount of light compared to other latitudes, was the Elizabethan scientist George Best, who was killed in a duel in 1584.
If you could fold
a piece of paper 51 times, its thickness would exceed the distance from here to the Sun.
The Sun’s core is so hot that a piece of it the size of a pinhead would give off enough heat to kill a person 160km away.
Truth is like the sun. You can shut it out for a time, but it ain't going away.
The ancient city of Alexandria was built so that the sun shone down the main road on Alexander the Great’s birthday