Why do rainbows curve

If we draw rays of sunlight that reflect at 42 degrees into your eyes then those rays start to look like they form a circular arc in the sky. So the reflection gives you the shape of the rainbow, while the refraction gives you the colours of the rainbow.

If you are standing on the ground, then the rainbow stops when it hits the ground. If you are lucky enough to look out on some rain from a plane, then instead of seeing just a part of the circle, you may be able to see a complete circular rainbow, like this:. Hello, curious kids! Ask an adult to send your question to us. They can:. Please tell us your name, age, and which city you live in. You can send an audio recording of your question too, if you want.

Get smart. Sign Up. Support science journalism. Knowledge awaits. See Subscription Options Already a subscriber? Create Account See Subscription Options. Continue reading with a Scientific American subscription. I think that is the same question as earlier ones about whether the curvature of the arc is connected with the Earth's curvature. The answer is still no. Follow-up on this answer. Learn more physics! Related Questions.

Still Curious? Thanks- notes like this help us keep things up-to-date. Mike W. Would a rainbow still appear to arc in the vacuum of outer space? Does our atmosphere or the curvature of the earth have anything to do with it? But how do the water droplets, our position, and the sun form a cone? If we need a 42 degree angle to see a rainbow, then how can we see a "double rainboow"?

Does a double refraction occur? And if so does it allow us to see a rainbow at 2 different angles? Hello Austin, Yes they do and it's a quite common thing. It has nothing to do with any roundness of the eye? Lets say all the right raindrops existed in a volume or area in front of you, from the ground to s of feet; and the sun light came in as it does to create rainbow; there can never be seen or made a wall of rainbow in the air?

Table salt is scooped off the top of the water table. Adrian Cooper, Queens Park. Table salt is found as rock deposits, then it is crushed and processed. Salt lakes are another source, where it is obtained through natural evaporation. During processing, iodine can be added, which helps to prevent cretinism, along with magnesium carbonate to make it free-running.

The locality of salt determines the colour; some is pink, for example, and is usually sold as more expensive gourmet salt. Some salts can be saltier than others and are used more sparingly, depending on taste. Helen Triggs, Katoomba. The sea. Michael Morton-Evans, Mosman The Dutch Salt industry of the 15 to 16th century developed to such a degree that it and the herring trade became the backbone of the Dutch economy. The sea salt and salt from springs that they used were so contaminated by impurities that the salt was often highly corrosive.

With the introduction of highly purified salt, it could be presented upon the table in salt cellars of great beauty, we recall Cellini's name in this regard. In brief then, a salt on the table was highly purified and non-corrosive. Steve Barrett, Glenbrook Maybe from where I live: the tablelands.

Bob Dengate, Bathurst. How does insect spray kill insects? Insects breathe through small perforations along their body, which are more easily blocked than a nose or mouth. Insecticides also generally contain additional substances, such as pyrethrins and cholesterinase inhibitors, which interfere with the insect's nervous system.

Other poisons may induce catastrophic changes to the insect's chemical balance, for example, by displacing potassium or calcium from body fluids. Peter R. Green, Marrickville. Most insect sprays contain neurotoxins poisons which act on nerve cells called pyrethrins, which come from the seeds of the pyrethrum plant. Spraying an insect with a pyrethrin will ususally cause paralysis, as the nerve cells stop working, which will immobilise and then kill the insect.

Although deadly to insects and fish , pyrethrins are fairly non-toxic to mammals and birds because their bodies can transform them into harmless substances. However, human contact with pyrethrins can trigger skin allergies or cause breathing difficulty if inhaled pyrethroids, made from chemicals rather than pyrethrum seeds, are less allergenic.

Also, industrial insecticides, such as those used in commerical pest control, are often extremely toxic to humans, so should be treated with more caution. Greg Turner, Surry Hills Insecticides work by stopping the reabsorbtion of the chemical which allows contact between neurons in the insect's brain. The neurons cannot stop firing, thus we see the uncontrollably twitching limbs of a poisoned insect.

In effect their brains are burnt out. These chemicals are known as anti-colinesterase agents. Dave Standfield, Kandos Many of the current insect sprays destroy the wax coating of the insect's respiratory system.

When applied directly, the insect suffocates and die instantly. Jaya Seethamraju, Gladesville They don't. The sprays are formulated to trigger a self-destruction response, which causes the insects to hang themselves. Matt Petersen, Randwick All contain poisons that interfere with the nervous system in varying ways, usually by prolonging or shutting down the activity of neurotransmitters.

Pyrethroids, alkaloids, nicotine and rotenone, based on the natural insecticides found in chrysanthemum, sabadilla, tobacco and derris root plants, all kill insects in this way. Paul Roberts, Lake Cathie. When does ancient history stop and become modern history? It's not that simple. The world then slipped into the Dark Ages, until about AD or until the beginning of the European Renaissance in the 14th century, depending on which historical authority you side with.