Do You Know
Questions & Answers on General Knowledge.
How does one prove that the earth is round?
There are many possibilities, so I'll suggest an intriguing method that is familiar to surveyors. While the overly simple technique I suggest isn't particularly practical, it is closely related to surveying techniques that are practical. Take a very long string, say about 20 miles long, and attach one end of the string to a post. Now draw the string taut and walk all the way around the post while holding on to the other end of the string. If you measure the distance you walked while completing one full trip around the post, you would expect it to be related to the length of the string by a factor of 2 times pi because you learn in grade school that the circumference of a circle is 2 times pi times the radius of that circle. However, that relationship is only true if you're working on a flat surface. Since the earth is curved, the circumference of the circle around which you walk will be somewhat less than 2 times pi times the radius of the circle. That result is enough to prove that you're on a curved surface. You can see this effect by performing the experiment I just suggested on the surface of a basketball. Take a short length of string and use it, together with a pin and a pencil, to draw a circle on the surface of the ball. If you measure the circumference of that circle and compare it to 2 times pi times the length of the string, the circle's circumference will be a bit shorter than expected. As with the earth, the basketball is a curved surface. The larger the circle you try to draw in this manner, the greater the discrepancy between 2 times pi times the radius and the actual circumference of the circle.
Will ice cubes made out of heavy water (water that is rich in the heavy isotopes of hydrogen) sink to the bottom of a glass of water?
How are incandescent light bulbs made?
In plain English that a child can understand, how does a magnet work?
If you fire a bullet horizontally and drop an identical bull at the same moment, will they both hit the ground at the same time?
How does an operational amplifier work?
Why do we say a graduating lawyer has “passed the bar”?
How was art important during the Middle Ages?
How long did the peace last after World War I?
What is an avalanche?
What is a googol?
Were microwaves invented for the microwave oven?
Which is the longestrunning musical?
What were the trenches?
What's a rip tide?
Why do different sunglasses appear darker than others?
When light hits an object, how do we recognize the color?
How many moons does Venus have?
How much of Earth is covered with land and water?
Is the cheetah a big cat?
Who were the Wright brothers?
How can light "travel" through a vacuum when there were no "particles" in the vacuum on which it could "transmit" its charge?
Do regular magnets lose their magnetism or do they stay magnetized always? What about electric magnets, like the ones used in wrecking yards?
How do submarine pilots know where they are going when they are underwater?
How are measuring units related to the human body?
Who invented the first computer?
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