BRAINDUMP
WHY CAN TIGERS SWIM?
Amazing answers to your curious questions
Most mammals can swim, including lions, leopards and cheetahs. Being able to swim is quite different from being able to swim well, though. Most of the big cats tend to avoid water as they are adapted to hunt on land.
Tigers, on the other hand, live in lush tropical jungles with lots of wide rivers. The other big cat that swims well is the jaguar – another forest dweller. Prey animals in forest environments don’t form nice convenient herds, so tigers have to go looking for their food. Tigers can have territories as large as 37 square miles, and being able to swim across rivers is a big evolutionary advantage. Tigers can swim rivers as wide as 4.3 miles across and might swim up to 18 miles per day as they patrol their territory.
DOES ANTIGRAVITY REALLY EXIST?
Antigravity is defined as an area which is free from gravity. If it existed, antigravity could make objects weightless or be used to propel spacecraft. Creating antigravity would mean shielding an area or a device from gravitational forces. According to general relativity, where gravity is the result of the geometry of space-time, this would simply be impossible. According to quantum theory, hypothetical particles called gravitons transmit gravitational forces. But given that we do not even know if these particles exist, destroying or controlling them seems more or less impossible. For now, scientists are dubious that antigravity will ever exist other than in the imaginations of science-fiction fans.
HOW THICK MUST GLASS BE TO BECOME OPAQUE?
Glass absorbs different amounts of light at different wavelengths. For ultraviolet light, it’s already virtually opaque, but even for the visible part of the spectrum glass isn’t perfectly transparent. An ordinary three-millimetre sheet of window glass lets about 91 per cent of light pass. With six millimetres you’d only get 91 per cent of that 91 per cent – in other words, 83 per cent – and so on. If you were able to make a sheet of glass a metre thick without introducing any impurities or imperfections, the amount of light making it all the way to the other side would be just 0.002 per cent, which is enough to make full daylight as dim as a moonlit night. However, it still wouldn’t be totally opaque.