How different Linux distros are related?


If you are new to Linux, you may be confused with so many different Linux distros (i.e. flavors) available.

Following hierarchy chart will help you to understand the relationship between them.

This chart is prepared based on how each distro manages its software installation (similar to add/remove programs in Windows). Note that 2 most common flavors are Debian and Red Hat (RPM). Many popular Linux distros are derived from it.


Linux Tree

There can be separate classification based on front end (or user interface) where same distro can use different interfaces like Gnome etc.

If you have never used Linux before and want to test the experience, I suggest you try any of the following (in no particular order).

  • Ubuntu (or any of its flavors)
  • Mint (may have issues with AMD computers)
  • Fedora (easy to run from USB)

Why airbags are marked as SRS?


Airbags are Supplemental Restraint System (SRS) because they supplement the function of seat belts.

The seat belts are primary restraint system in case of an accident. So you must wear seat belts at all times. If seat belts are not worn, airbags may not be deployed in case of a collision.

Always wear seat belts!

Why rupee always falls against dollar, pound, euro?

Historically, Indian Rupee always fell against strong currencies like Dollar, Pound or Euro.

During mid of 2013, rupee had almost a free fall. It now equals 1 $ = 60 Rs or 1 £ = 93 Rs.
So why suddenly rupee fell so low?
One reason is better economic outlook in USA. Large scale investors are now expecting better return on their investment from USA. Thus, their funds are going towards USA and less amount is coming to India. For many day to day products, India needs foreign currency (in the form of $, £, € etc.) so less foreign currency coming to India means more demand for $ £ € to buy goods/raw materials from outer world.
Incidentally, weakening of rupee should make export much more attractive as same $ will now buy more Rs. However, there is a catch. To produce many of those exportable goods, businesses need to import raw materials from outside India, which requires foreign currency! Since such import is getting more expensive, resulting goods (manufactured in India) is also becoming expensive – thus eroding the benefit of weakening rupee for export.
Weakening rupee also sometimes prompt foreign importers (who buy exported goods from India) demanding a re-negotiation on price (as they claim weakening rupee will benefit Indian exporters also we have just seen that may be the case always).
Non residents Indians (NRI) are happy because if they send foreign currency to India now they will get much better return (i.e. more Rs for every $ sent). However, such fun is only possible if they don’t want to take money out of India at a later date. If NRIs send money to India and invests in a scheme in India, when they convert money later from Rs to $/£/€, chances are – due to rupee weakening even more, they will get a very poor return.
So, in short, weakening rupee is not a good news for investors especially those who want to invest foreign currency in India and then want to convert that to their native foreign currency once their investment is matured. If rupee falls further between the time they invested and investment matured and considering rate of return and inflation, they may even get same/lower than what they originally invested in $/£/€ terms!
In theory, Reserve Bank of India (RBI) can intervene by imposing a temporary limit of foreign currency going out of India but that will irk lots of common public and goes against free market economy principle (which India has adopted since 1990s).

How bitcoin works?


Bitcoin is a virtual currency. In real currency, you have notes and coins which you can exchange for goods or services.

Bitcoin is a string of characters like 31uEbMgunupShBVTewXjtqbBv5MndwfXhb, (the real bitcoin is different, but lets assume it for the sake of argument).

There is an algorithm (not secret) which validates whether a bitcoin string is valid or not and whether it has been used previously (in other transactions or not). This transaction ledger is known as blockchain (analogous to a bank account or credit card statement).

You must have bought goods with your credit card. When placing order online, the merchandiser establishes a connection with the bank to validate your card is valid and has enough credit to spend.

In a similar fashion, for each bitcoin transaction, a bitcoin bank (some designated computer servers) validates the bitcoin string you are using and ensures it has not been used before.

So how bitcoins are generated? One needs a massive amount of processing power (thus multiple computers connected together) to generate a new bitcoin (i.e. to generate a string which is valid as per bitcoin algorithm). This process is called mining. The bitcoin algorithm suggests that only 21 million strings can be generated which will be a valid bitcoin. So far 50% of those have already been generated. The rest 50% is expected to be generated in next 5-10 years.

Just like you stash cash in your wallet, bitcoins are stored in a digital wallet. If not careful, your cash may be stolen and someone can use it on for their own purchase. In a similar fashion, if you don’t guard your digital wallet, someone can steal your bitcoins! Bitcoin wallets have addresses (like your Paypal address is your email etc.) like this one – 1JArS6jzE3AJ9sZ3aFij1BmTcpFGgN86hA. When transacting with bitcoin, one must send a bitcoins to receiver’s valid wallet address. However, to prevent someone stealing your coins, there is a safeguard concept called private key. You can say this is like a real key to your chest. If someone has the key, he/she can open your chest and get all your money (i.e. bitcoins) out.

The bitcoin addresses can be calculated from private key but not the other way round. So it is important that you do not lose your bitcoin private key!

Buying and selling bitcoin is similar to buying/selling any other currency. Its exchange rate also fluctuates like any real currency.

Why Microsoft created Windows 8 Metro interface?


There was nothing wrong as such in Windows 7. However, unless businesses can make working things obsolete via upgrade to newer versions they won’t make enough money!

So Microsoft introduced Windows 8. However, unlike previous versions of Windows, they tried to force new Metro interface which is more suitable for touch screen devices. Most users were unhappy and wanted to revert to Windows 7 like interface. But why Microsoft introduced it in first place?

Metro and legacy Windows applications are not compatible. An app designed for Metro interface won’t run in traditional Windows environment. Metro apps can only be downloaded via Windows Marketplace. Now this is a very crucial difference. In earlier Windows, you could download apps from literally millions of websites. However, in Metro interface, your only option is Windows market place. This is similar to Apple’s AppStore concept. Microsoft did at because they wanted to capture 30% of all app sales. They can only do it if those apps are sold using their own app store only.

The trouble for Microsoft started when consumers did not like Windows 8. In fact various statistics show PC sales have been slowed down because consumers shunned Windows 8. Now Microsoft is caught between devil and deep sea. Backtracking from their Metro interface means potential loss of profit in future and acceptant strategic failure. However, if they continue to force Windows 8 Metro interface to consumers they may face continued backlash.

This is also the reason why Microsoft does not offer any option to start Windows 8 straight into legacy desktop! Because they want consumers to adopt their new Metro interface. Some consumers are using third oath apps to make Windows 8 behave like Windows 7.

But now you know why Microsoft did not offer these simple options themselves!

Why museums don’t allow flash photography?


Not all museums prohibit flash photography. But some of them do. Some museums prohibit photography altogether but that is due to commercial reason.

So why flash photography is wrong?

There are several reasons behind this.

Some old artworks are made on perchments or some fragile materials which may fade quickly if exposed to strong lights. Thus frequent exposure to strong flash lights may accelerate the fading process.

Such artworks are often kept in dimly lit rooms. All the visitors eyes are accostommed in dim light. Now if suddenly flashes start going off then it becomes irritated to other visitors nearby. This is another reason i.e. to avoid disturbance to other visitors (it is similar to why you should not talk in loud voice inside museums).

Sometimes museum authories claim that flash interferes with their intruder detection sensor systems. However, not much detail is know if that is true.

How come bridge cameras can offer so much zoom?


Nowadays many compact cameras can offer 25x-30x zoom. But having similar kind of zoom is not possible in DSLR cameras where it is mostly limited to around 11x-15x.

The reason why compact/bridge cameras can offer this (at a reasonable price) is these cameras have much smaller sensors compared to DSLR cameras. Thus, these cameras need much smaller lenses to cover that sensor. If you notice lens specification of these cameras they are usually at 4-100 mm range. While in DSLR, these are 18-200 mm range. Since DSLRs have much bigger sensors, they need massive lenses to offer long zoom range. This makes the lenses heavy and expensive.

So even though you can get away with very long zoom in smaller cameras, the image quality will be much inferior compared to DSLR’s APS-C or full frame sensors.


Why DSLR cameras take better pictures?


We know that usually DSLR cameras take much better pictures than compact cameras. But why?

This is due to 3 main factors. Firstly DSLR cameras have much bigger sensor. Typically these are APS-C or full frame size. Compact cameras have much smaller sensors which capture less details. Secondly, DSLR cameras usually have much better quality lenses. Thirdly, DSLR cameras offer lots of manual adjustments which allows photographers to have much better exposure and composition.

There are some bridge cameras which use APS-C size sensors. If these cameras use good quality lenses, then theoretically images taken by these cameras will be comparable to those taken by DSLRs.

Why most US locomotives have single cab while European ones have dual cabs?


Most US locomotives have single cab. This creates a visibility problem when operating long hood forward mode (visibility is usually ok while operating short hood forward mode). However, it is quite rare for US locos to operate solo – they mostly work in pair (sometimes upto 3-4 units together as well). As a result, they rarely run as long hood forward mode in real life.

But in Europe, the overall weights of trains are lighter and thus often trains are pulled by just single locomotive. Here both forward/reverse operation is desired. Thus European locos need good visibility in both directions (otherwise they would need turntables which are now obsolete after steam loco era).

Countries which imported American locos (like common WDM style locos in India, licensed from ALCO) but often runs as single units, visibility is indeed a problem while running in long hood forward mode.

How cartograms are useful?


A cartogram is a map where geographical entities are represented not by their land area but by some other parameter.

For example, following cartogram world population by countries where land areas are not actual areas but proportional representation of population of the country.


World Population cartogram

It helps to see immediately which countries are over populated against their land areas.