Answers to Last Issue's Do You Know?
1. What is the Ring of Fire?
See separate article on this question.

2. India is a sovereign socialist secular democratic republic. What is the difference between democratic and republic?
Democracy is an abstract name for a system and republic is the more concrete result of that system, that is, it specifies the nature of that democracy. We will give examples below.
India is a democracy because its government is a representative one where power comes from the people (who elect the representatives in Parliament). It is also a republic because its head of state is an elected president, not a hereditary king. So it is both a democracy and a republic. Democracy emphasizes rule by the people, while republic emphasizes the rule of law and an elected head of state under a constitution. The constitution limits the majority's power and protects minority rights, a key feature of India's republicanism.
Democracy: The word comes from the Greek demos and kratos, meaning "rule by the people". It is a system where supreme power is vested in (resides with) the people (actually, all the adults in India!). How do they exercise this power? It can be directly or indirectly through a system of representation. This is what happens when we vote in the periodically held free and fair elections: we elect people who represent our view, and make decisions on our behalf, so the belief is that in a democracy, the power is actually with the people.
Republic: The word comes from the Latin res publica, meaning "public matter". It is a form of government where the head of state is an elected or nominated president. So, for example, the United Kingdom (Britain and Northern Ireland) is a democracy but not a republic because it has a king.
How is this President elected? The elected members of both houses of the Parliament at the Centre--Lok Sabha and Rajya Sabha--and the elected members of the State Legislative Assemblies (also the Union Territories) whom we have elected, together form an electoral college which elects the President.
The constitution limits the government's power and protects citizens' rights. It was adopted on 26 Jan, 1950, and that is why we celebrate Republic day!
So India's political system is a "democratic republic" because it combines these two principles. The power flows from the people (democracy), and the structure of the state includes an elected head of state and is bound by a constitution (republic).
The republic aspect ensures that the will of the majority cannot override fundamental rights, as the constitution provides a legal framework that protects all citizens. In particular, it assures the following:
. Absence of a privileged class: All public offices, including the highest ones, are open to every citizen without discrimination.
. Rule of Law and a Constitution: The government operates within the constraints of a written Constitution, which is the supreme law of the land. The Constitution safeguards individual rights and ensures checks and balances, protecting minorities from the potential "tyranny of the majority" that could occur in a pure (direct) democracy without constitutional limits.
. Sovereignty vested in the people: The state's authority is derived from the people, and no one holds public power as a proprietary (private) right.

3. We are familiar with cyclones. Do we also have tornadoes in India?
Yes, India also experiences tornadoes, although they are rare compared to other countries.
Tornadoes are a violently rotating column of air touching the ground, usually attached to the base of a thunderstorm. Tornadoes are nature"s most violent storms, arising from powerful thunderstorms. They can devastate a neighborhood in seconds.Winds of a tornado may reach 500 kilometers per hour. As it moves, it can damage a path more than a kilometer wide and 80 km long. Hail is very commonly found very close to the tornadoes.
Some tornadoes are clearly visible, while rain or nearby low-hanging clouds obscure others. Tornadoes develop extremely rapidly, and may dissipate just a quickly. Most tornadoes are on the ground for less than 15 minutes.
Before a tornado hits, the wind may die down and the air may become very still. A cloud of debris can mark the location of a tornado even if a funnel is not visible. Tornadoes generally occur near the trailing edge of a thunderstorm. It is not uncommon to see clear, sunlit skies behind a tornado. 
In India, they most often occur in the eastern states of West Bengal, Odisha, and Jharkhand during the pre-monsoon season (March to June), and have also been reported in the northwest region of the country.
Only about 12 tornadoes have been recorded in India over 30 years between 1976 and 2010. Most tornadoes in India are deadly, with an average of 80 people killed per tornado. The deadliest Indian tornado on record hit areas near Belda in W. Bengal on March 24, 1998, killing 250 people. The Bay of Bengal region is a hotspot for these storms, although states like Punjab, Haryana, and New Delhi have also recorded tornadoes. They most frequently occur during the pre-monsoon season, especially in March and April. 
Many tornadoes in India have been deadly, with significant property damage caused by strong winds. They are often associated with severe thunderstorms that develop when moist, low-level winds converge with dry, upper-level air. 

4. What is the most abundant element on Earth? In the Universe?
The most abundant element on Earth's crust (on the surface, which is what we see) is oxygen (about 46%)! This is because most of the minerals found in the Earth's crust are in the form of oxides, such as silica (sand) etc. By mass, the most abundant element is iron, which is in the core of the Earth.
The mass of the Earth is approximately 5.97×1024 kg. Roughly the core of the Earth is contained in half the radius of the Earth. By mass, it is composed mostly of iron (32.1%), oxygen (30.1%), silicon (15.1%), magnesium (13.9%), sulfur (2.9%), nickel (1.8%), calcium (1.5%), and aluminium (1.4%); with the remaining 1.2% consisting of trace amounts of other elements. What about in the entire Universe?
The abundance of chemical elements in the universe is dominated by the large amounts of hydrogen and helium which were produced during Big Bang nucleosynthesis when the Universe itself was formed. The remaining elements, making up only about 2% of the universe, were largely produced by the explosions of stars as supernovae and certain red giant stars.
Lithium, beryllium, and boron, despite their low atomic number, are rare because, although they are produced by nuclear fusion, they are destroyed by other reactions in the stars.
The elements from carbon to iron are relatively more abundant in the universe because of the ease of making them in supernovae. Elements of higher atomic numbers than iron (element 26) become progressively rarer in the universe, because they increasingly absorb stellar energy in their production. Also, elements with even atomic numbers are generally more common than odd ones in the periodic table, due to energy considerations too complicated to explain here. 
There are 80 known stable elements, and the lightest 16 comprise 99.9% of the ordinary matter of the universe. These 16 elements are the ones from hydrogen through sulphur.
Hydrogen and helium are estimated to make up roughly 74% and 24% of all baryonic matter in the universe respectively. Despite comprising only a very small fraction of the universe, the remaining "heavy elements" can greatly influence astronomical phenomena. Only about 2% (by mass) of the Milky Way galaxy's disk is composed of heavy elements.
Compiled from various sources