Answers to last issue's Do You Know?

1. What is the meaning of Universal Time (UT)?

All time and space on earth is measured by two reference lines: Longitude based on the Greenwich Meridian (0 Longitude) and the latitude based on the Equator (0 Latitude). To simplify timekeeping, modern nations divide earth into 24 north-south zones of standard time.
Although Greenwich is in the UK, the position of the Greenwich Meridian was agreed to at an international conference in Washington, DC, USA in 1884 where it was also decided that a Universal Day begins at 00:00 at that longitude. This imaginary line runs from North Pole to South Pole as established through the telescope at the Royal Observatory in Greenwich at that time. In 1928, the International Astronomical Union recommended that the time known as Greenwich Mean Time (GMT) be referred to as Universal Time (UT). Prior to 1925, in astronomical and nautical almanacs, a day of Greenwich Mean Time began at noon.
It was also determined at the Washington Prime Meridian conference in 1884 that the International Date Line be drawn at 180 degrees, that is, 12 hours ahead of GMT. This means that the date changes across this date line.
This was required because of the advent of aeroplanes because of which people were able to easily travel between different time zones. The date line was chosen as that longitude that passed through the most amount of water and the least amount of land. This is important: suppose the meridian cuts through your town. Then as you go from east to west of the line, say to school or for shopping you are going from today to yesterday and back! It would be inconvenient and cause chaos!
At 00:00 UT on any day, the sun rises along a line that runs from about 650km east of Kerguelen Island in the Indian Ocean to about 640km east of Amsterdam Island, through the Nicobar Islands, up along the Burma-Thailand border, through China, along the China-Outer Mongolia border, along the China-Russia border, through Siberia and out into the Arctic Ocean just north of the Poluostrov peninsula. India time is set to UT + 5:30.
The International Date Line is not a straight line. It detours eastward through the Bering Strait to avoid dividing Siberia and then deviates around the Aleutian Islands in Alaska and some of New Zealand to follow the time zone boundaries of those places.

2. Did plant-eating dinosaurs eat grass?
Textbooks have long taught that grasses did not become common until long after the dinosaurs died at the end of the Cretaceous period, 65 million years ago. Depicting dinosaurs munching on grass was considered by experts to be foolish. It was thought to be as wrong as showing prehistoric humans hunting dinosaurs with spears since humans appeared on the planet long after dinosaurs went extinct.
But fossilised dinosaur dung from India was examined under a microscope to see what it contained. This would help us decide what the dinosaurs ate. The study showed that the last massive plant-eating dinosaurs munched at least five different types of grass.
The key evidence is tiny silica crystals called phytoliths which grow inside plant cells. They survive intact even after digestion. Indian palaeontologists discovered phytoliths in fossil dung, and called in an expert to identify them. The sample shown in the photo is about one tenth of a mm in size.
It was soon recognised that some of the phytoliths had distinctive shapes found only in grasses. The grasses the dinosaurs ate were herbaceous forest plants perhaps up to several metres tall.
Dated at 65 to 70 million years old, the tiny crystals are about the same age as the oldest previous evidence of grass fossil pollen found in India, South America, and north Africa. However, all grass pollen looks the same, so researchers thought it came from a very primitive grass or an early relative.
Phytoliths differ among grasses, and the five types found in the fossil dung came from more highly evolved types, indicating that grasses had diversified significantly before 70 million years ago, maybe even more than 100 million years ago.
The only dinosaur bones found near the fossil dung are those of massive, long-necked plant-eaters called titanosaurs, so it is believed that the droppings are theirs.
Young titanosaurs needed massive amounts of food because they grew rapidly to adult size. They had small heads with long necks and they probably gulped down large amounts of foliage, grinding it up with stomach stones rather than chewing it.
And they were not fussy eaters. Grass was only a small part of their diet, which included other flowering plants, cycads and conifers. But their taste for grass adds to evidence that they did not spend all their time with heads browsing in the trees, like modern giraffes.

3. How do bees communicate to one another when they find a source of food?
Honey bees can perform learning tasks that go beyond simple conditioning. The bees that go in search of honey are called foragers. When they find honey, they must be able to communicate their findings so that all the bees in the hive can come and help them collect it.
It is not known exactly when the forager bees call for help, but it probably depends on the quality of nectar and/or pollen brought in.
There are two main hypotheses to explain how foragers recruit other workers: the "waggle dance" or "dance language" theory and the "odor plume" theory. The dance language theory is far more widely accepted.
It has long been known that successfully foraging Western honey bees perform a dance on their return to the hive, indicating that food is further away. The round dance is a short version of the waggle dance, indicating that food is nearby.
The forager, laden with nectar, dances on the comb in a circular pattern, occasionally crossing the circle in a zig-zag or waggle pattern. Aristotle in 330 BC, described this behaviour in his Historia Animalium. At that time, it was thought to attract the attention of other bees.
In 1947, Karl von Frisch correlated the runs and turns of the dance to the distance and direction of the food source from the hive. The orientation or direction of the dance is correlated to the relative position of the sun to the food source. The length of the waggle portion of the run is correlated to the distance from the hive. This was amazing and showed the ability of bees to compute directions and distances!
Also, the more vigorous the display is, the better the food.

4. Why do moths fly towards a bright light?
Moths frequently appear to circle artificial lights. One idea advanced to explain this behavior is that moths use a technique of celestial navigation called transverse orientation.
For instance, if you were flying in space and you want to travel in a certain, fixed direction, transverse orientation is the easiest. This means that you fix your sight on a bright star along the direction you want to fly. Then any time you are in doubt about the direction you are taking, you only have to check that you are still able to see that star directly ahead. You don't have to have the star in front. For example, by keeping the star to your right always, you are still travelling in a straight line.
Scientists believe that moths fly by maintaining a constant angular relationship to a bright celestial light, such as the Moon. This helps them fly in a straight line (or even in fixed curves). The moon is so far away, that even after travelling great distances, the change in angle between the moth and the moon is very small and gives a good indication of direction. So if the moth keeps the light source ahead of it, it can easily travel in a straight line.
The second factor is that of man-made lights. Human light sources have not existed for long compared to the millions of years that moths have. So this time-period has not been long enough to affect the evolution of moth navigation systems. When a moth encounters a much closer artificial light and uses it for navigation, the angle changes noticeably after only a short distance, in addition to being often below the horizon.
The moth instinctively attempts to correct its flight path by turning toward the light, since this is what it has learned over centuries. While this works fine when the light source is the moon, in the case of artificial lights, it causes moths to come plummeting downwards. As the moth gets closer and closer it seems to make a spiral flight path that gets closer and closer to the light source.

5. What bird can fly backwards?
Hummingbirds are birds of the family Trochilidae, and are native only to the Americas. They are known for their ability to hover in mid-air by rapidly flapping their wings 15-80 times per second (depending on the species). Capable of sustained hovering, hummingbirds also have the ability to fly backward, being the only group of birds able to do so.
Hummingbirds may also fly vertically and laterally. Their English name derives from the characteristic hum made by their wings. Hummingbirds do not spend all day flying, as the energy costs of this would be prohibitive; the majority of their activity consists simply of sitting or perching. Hummingbirds feed in many small meals, consuming many small invertebrates and up to five times their own body weight in nectar each day. They spend an average of 10-15% of their time feeding and 75-80% sitting and digesting.
With the exception of insects, hummingbirds while in flight have the highest metabolism of all animals, a necessity in order to support the rapid beating of their wings. Their heart rate can reach as high as 1,260 beats per minute, a rate once measured in a Blue-throated Hummingbird. They also typically consume more than their own weight in nectar each day, and to do so they must visit hundreds of flowers daily. At any given moment, they are only hours away from starving!
Hummingbird flight has been studied intensively from an aerodynamic perspective using wind tunnels and high-speed video cameras.