how high is up whay are the clouds white and why is the sun yellow??

Answer 1

WHY IS THE SUN YELLOW?

The sun is an intense ball of burning gases. It's a star and like the other stars we see in the sky it's actually white.

Because it's so much closer than the other stars it appears far more intense and it's this intensity which can make it appear yellow. What's actually happening is that the sunlight is striking the retinae in your eyes and being interpreted by the visual cortex as having a yellow colour to it.

If you were to look directly at the sun (don't because it's dangerous) it would appear to be almost white.


HOW HIGH ARE CLOUDS?

it depends on the type of cloud and can be anything up to about 20 kilometres (12 miles) high, higher in some cases. The very thin clouds wispy clouds such as cirrus and cirrostratus are usually above 6,000 metres. Mid level clouds including altostratus and altocumulus appear as fluffy balls and these are usually 2,000 to 6,000 metres high. The Low level coulds which we associate with rain are usually less than 2000 metres high, these types include nimbostratus and stratocumulus.

Some clouds develop vertically and can be anywhere from ground level to 30,000 metres high such as thunderclouds. These cloud types include cumulus and cumulonimbus.


WHY ARE CLOUDS WHITE?

Sunlight is all the colours of the visible spectrum and when sunlight hits the water droplets in the clouds the light is slightly refracted (bent) by the droplets. The light hits one droplet, is bent, leaves the droplet, hits another, is bent some more and so on. A lot of this light is relected right back out of the cloud and because it contains all the colours of the spectrum it appears to be white. It's this same reason that makes snow appear to be white when really it's translucent (colourless).

Answer 2

Why is the Sun yellow?

It isn't, really. The colour yellow is a purely human interpretation of a collection of radiation that hits the retinae of our eyes and gets processed by our visual cortex.

Why are clouds white?

Not all clouds are pure white, however, for those that are, it is due to their altitude and the reflection of sunlight.

For example, a cirrus cloud has an altitude of approximately 8km above sea level. At such extreme altitudes all high-level clouds are made up only of ice crystals, as the water vapor from which they are initially formed has frozen.

The ice crystals reflect sunlight. When flying above clouds during the day, they are always bright white. When we get dark clouds, they are so thick that they soak up most of the sunlight or reflect it upwards, and so things aren't as bright below. Storm clouds are the thickest clouds, and look the darkest from below, though they still look bright white from above.

Answer 3

OK... Trevor has already answered the bit about the clouds, so I won't repeat him. They are white simply because of the scattering of light by tiny droplets of water... You know, you can actually work out how big these droplets are by measuring the angular radius of a scattering 'ring' that sometimes appears around the sun...


The sun, like any other star, generates it's power by nuclear fusion in the core. There are many different mechanisms, all of which depend on the star's mass and age. The current fusion process dominant in the sun is known as the proton-proton cycle. This cycle effectively fuses hydrogen ions to make Helium. The reaction can continue with what's known as the 'triple alpha' process, where 3 Heliums are fused to make Carbon. This usually happens as a star approaches the end of its life.

Now, the sun is about 5Billion years old... In stellar terms, it's middle aged. It has another 5Billion years of fuel left inside.
When nuclei such as protons fuse, energy is released in the form of gamma rays. The gamma rays then traverse out from the stellar core towards the surface, scattering from other nuclei as they do so. This scattering causes them to loose energy until they turn to X-rays, then Ultra Violet, and then into the visible regions. You can image the gamma rays to be like bouncing balls - for every object the ball hits, it looses a small amount of energy until it can't bounce any more!

A star's 'colour' is governed largely by the surface temperature. For those of you who've heard of Blackbody Radiation, then you'll know exactly what I'm talking about... Every object emits electromagnetic radiation in relation to its temperature. The human body, for instance, is constant at a temperature of 37Celsius. We actually emit light in the form of Infrared - with a wavelength of around 10,000 nanometers. (that's one hundredth of a millimeter)
If we were somehow to get warmer, our emited wavelength would decrease; passing through the infra-red into the optical regions. This is why molten steal allways appears red-orange. The temperature is actually high enough to permit the detectable emision of visible light in the red and orange regions.
For an object to glow yellow, as in the case of the sun, it's peak emision corresponds to a temperature of 5780 Celcius; the temperature of the sun's surface, which in turn is a result of gamma rays loosing energy as they travel from the stellar core to the surface. You may be interested to know that the scattering effects in the sun are so strong, that light often takes millions of years to come out. That is, the light you see now, is mostly from gamma rays the sun produced a million years ago.

As time progresses, and the sun produces more helium, the triple alpha reaction will dominate. The sun's temperature will slowly increase with time. The habital zone where the Earth currently sits will move outward, eventually destroying all life here. After that, the sun will inflate, turning into a red-giant with a surface temperture of around 3000C. Then the core shrinks into an ultra hot glowing diamond a few time larger than Earth. A long, long time after that, the white-dwarf will cool down, and turn into a cold, lifeless body with the charred, dark remnands of it's orbiting planets.


Twilight

Answer 4

Not sure about the clouds but the sun is a ball of burning fire so the yellow we see are in fact the flames.