First of all, are you a child asking this simple question?
If not, and you are an adult, maybe you were sleeping in elementary class at the back row =)
If you are, I will gladly answer your question.
Airplanes usually have jet engines that produce hot air as by-products of burning jet fuel. The jet propulsion system pushing the airplane forward leaves a trail of hot air. When hot air comes in contact with cold air, it produces air droplets. These droplets is what we see as white streaks in the sky trailing an airplane...
An example is when you blow your breath to the cold winter air and you can see steam...
Generally these are made by aeroplanes. The local pressure differences caused by the plane's wings may cause air moisture to condense into fog (or cloud) as they pass through it. These streaks are known as vapour trails.
Some weathered rocks have rust streaks due to the iron content in the rocks. When rocks that have ferrous iron are weathered there will be rust streaks present.
No. The sun is the bright yellow thing in the sky. The moon is the big white thing in the sky.
Snow?
Yes
ribbon
You can see them on the ground if you are looking for them and you are amazingly lucky. Meteors can be seen as white streaks in the sky from dusk to dawn at night.
white
Cirrus (Ci): The ice-crystal cloud is a feathery white cloud that is the highest in the sky. It has a wispy looking tail that streaks across the sky and is called a fallstreak. - Kidzworld dot com
Some possible rocks that can have white streaks include quartz, marble, and gypsum. White streaks can also be found in other minerals and rocks that contain light-colored minerals such as feldspar or calcite. The presence of white streaks in a rock can be indicative of certain mineral compositions.
We don't no
Most commonly it's when your skin loses pigment. It causes white streaks that usually stay for life.
Because the colour of the sky reflects on the rainbow which makes it blue DAH DAH
rain, shooting stars, meteors, birds, clouds
Chlorine
white with green streaks
NORTHAN LIGHTS
Sometimes when the sky and storm are many in the sky, the sky will look a kind of white.