Happy 15th Birthday Wen Xian!!!
May your wishes come true!!!
Ok. Its already Thursday again.. Yes, time flies again and again. Tomorrow will be Friday! And lessons tomorrow are super slack, PE, Maths, STARS, and USA!
Advantages of Friday, is that after that will be Saturday and Sunday, so we can rest.
On the other hand, the disadvantage, is that its also nearer to a new week again, which is the Monday, and then the cycle goes again and again...
There's no homework today, which means I'll be able to slack tonight! :D. Cool, like finally?
Ok I'm posting something about lightning and thunder cos its cool~
Lightning and Thunder
Lightning is the most spectacular element of a thunderstorm. In fact it is how thunderstorms got their name. Wait a minute, what does thunder have to do with lightning? Well, lightning causes thunder.
Lightning is a giant spark. A single stroke of lightning can heat the air around it to 30,000 degrees Celsius (54,000 degrees Farhenheit)! This extreme heating causes the air to expand at an explosive rate. The expansion creates a shock wave that turns into a booming sound wave, better known as thunder. Thus the name thunderstorm.
Lightning FormationThe sky is filled with electric charge. In a calm sky, the + and - charges are evenly interspersed thoughout the atmosphere. Therefore, a calm sky has a neutral charge.
Inside a thunderstorm, electric charge is spread out differently. A thunderstorm consists of ice crystals and hailstones. The ice crystals have a + charge, while the hailstones have a - charge. The ice crystals are pushed to the top of the thunderstorm cloud by an updraft. Meanwhile, the hailstones are pushed to the bottom of the thunderstorm by its downdraft. Thus, the thunderstorm's + and - charges are separated into two levels: the + charge at the top and the - charge at the bottom.
During a thunderstorm, the Earth's surface has a + charge. Because opposites attract, the - charge at the bottom of the thunder cloud wants to link up with the + charge of the Earth's surface.
Once the - charge at the bottom of the cloud gets large enough to overcome air resistance, a flow of - charge rushes toward the earth. This is known as a stepped leader. The + charges of the Earth are attracted to this stepped leader, so a flow of + charge moves into the air. When the stepped leader and the + charge from the earth meet, a strong electric current carries + charge up into the cloud. This electric current is known as the return stroke of lightning and is visible to the human eye.Sound Waves Vs. Light Waves
You see a flash of lightning across the night sky. Five seconds later, your hear the rumble of thunder. If lightning and thunder come from the same source, then why don't they occur at the same time?
Actually, they do occur at the same time. The time difference that you sense is due to the way sound and light travel. Light travels extremely fast (300,000,000 m/s). In fact, it is faster than anything else. Sound travels at a measly 343 m/s through air. Therefore we can see light in an instant, but it takes a while to hear thunder.
Sound has another disadvantage because it tends to bounce off molecules in the air. This makes the sound travel in all different directions. The further away the source of the sound is, the more the sound gets distorted.
Therefore, when you hear rumbling thunder, the lightning bolt was far away. When you hear a crack or boom of thunder, the lightning bolt is close to you (<100 m).