Archive for the ‘Technology’ Category

What are different types of watches?


Watches are broadly of 2 types – mechanical or quartz.

watch types

The easiest way to identify a quartz or mechanical watch is to look at the movement of second hand. Quartz watch will have second hand which jumps every second where as in a mechanical watch, the second hand moves continuously.

Mechanical watches don’t have batteries so they need regular winding to make them work. Obviously, in modern world such action is bit awkward. So there is a different watch type, called automatic. They are also mechanical watches but they are powered by normal hand movement as part of your standard day to day life.

AccuracyExtremely accurateCan gain/lose few seconds every day.

Feature Quartz Mechanical
Identification Second hand jumps or digital display. Second hand moves continuously and analog display.
Popularity 85-90% of all watches in the world are quartz. Only 10-15% of world’s watches are mechanical.
Power source Battery (some are rechargeable via light) Stores energy in springs via manual winding or normal hand movement (automatic).
Maintenance Don’t require any maintenance (other than battery replacement if necessary) Besides winding, these watches require servicing in every few years.
Like for like cost Cheaper Expensive
FeaturesAlso called “complications” in watch industry terms Can offer lots of features like multiple times, alarm, stopwatch etc. They can offer similar features too but such watches tend to be too expensive.
Manufacturing Automated via tools Some manual craftsmanship is often required.
Longevity Can last 10-20 years. With proper servicing, can last 50-100 years.
Accuracy Very accurate Can gain/lose few seconds every day.


The world of watches is very fascinating. Read about it on the internet in your spare time.

What are common analog world time watches?


In modern times, you can download apps in your smart phones to show time anywhere in world. This is somewhat negated the necessity of having a traditional watch which can show times in multiple zones around the world. But don’t ever think that such watchmakers are losing money! A lot of people still prefer elegant and prestigious looking of branded watches on their wrists! In this post, I shall list some very common world time analog watches. Typical characteristics of world time watches:

  1. Should be able to show at least dual times at once.
  2. Seeing time for any time zone should not be overly complex.
  3. There should be a mechanism to swap primary and secondary time quickly.
  4. Should be able to cater for all time zones (including half hour GMT offsets like India – which is GMT+5:30)
  5. Accurate (should be radio controlled or able to pick signal up via GPS – not all watches have these facilities)
  6. Solar powered is preferred so that you don’t have to change battery.
  7. Affordable (you should not have to sell your kidney to buy one)

We shall see in this post how difficult it is to achieve all those parameters within budget. Please bear in mind that there are probably over hundred models of such analog world time watches. Some of them are very expensive. Not all of them offer half hour GMT offset. A quick way to figure that out is to look at dials and see if Delhi is featured. It should feature between Karachi and Dhaka. If Delhi is missing, that means the watch cannot show half hour GMT offsets! This means, in those watches, the minute hand for second time will be always synchronized with primary time. Even some very expensive watches have these problem! Some watches can only show GMT/UTC as a second time. You can’t set second time zone as any city in the world. Ok, enough talking, now let’s see some watches. Note: Prices shown are RRP on July 2014. Specific models may be retired anytime although other models in same series usually available in market for a long time. If you can find deals, often you can buy them at cheaper prices. The list is not in any particular order.  

Citizen eco-drive World Time AT 9010-52L [£379] w01   This is a typical world time watches. It does feature Delhi so covers all time zones. The smaller dial shows secondary time in 24-hr format (this is common for many of such watches).  The main dial shows time in 12-hr format but a separate dial (at upper left) indicates whether it is AM/PM via a 24-hr needle. The watch allows you to check time at any shown city by pressing couple of buttons. It also allows to swap primary and secondary cities by pressing 2 buttons at once.

Seiko Astron SAST003 [£1995] w02 This watch picks up GPS signal (as long as it can see sky) and automatically adjusts the time! This one is solar powered too. Mind that, there is a difference between radio controlled time and GPS controlled. Radio signals are emitted from only few places (typically USA, Germany, Japan etc.) and from the world and watch needs to be within 1500 km of that zone. However, a GPS signal can be picked from anywhere in the world – as long as access to sky is available. All satellites have atomic clocks in them – the signal that is picked up by this watch. So, in theory, this watch never needs time adjustment.

 Casio Edifice EQS-500DB-1A2 [£226]

w03 This one is also solar powered.  

Patek Phillippe 5110 Worldtime [£18000]

025110ORROSE Yes, you read the price right! More of a glamor statement than utility watch. The clever design here is at middle ring, which rotates counter clockwise. In the above image, the home time is Paris (indicated by Paris being at 12 o’clock position. The time at home is 10:09. As per dial, it is 12:09 at Moscow and 00:09 at Anchorage. Note that, this watch can’t show half hour offset zones – in spite of hefty price tag!  

Rolex GMT Master II [£5500]

w05   Another glamorous watch! On a quick glance, it does not feel like it can show world time. In fact, it is just a dual time watch. You can see the main home time screen. The outer bezel rotates manually. The blue hand with triangular pointer  is GMT hand. You can set this hand to show any other city’s time.  But here as well, as you only have an hour hand for dual time, the minutes hand is same for both home and secondary time zone – which in turn means this watch too can’t show half hour GMT offsets. I think now it is fair to say that spending more does not automatically mean having more functionality!

Casio SPF60 [£75] w06   This is also not a true world time watch but a dual time watch. The analog and digital times can be set independently. However, alarm/calendar works only on the basis of digital time. The watch also provides reading for barometer (with last few hours trend), altimeter and a thermometer.

Citizen Eco drive Skyhawk AT [£350]

w07   This watch can show 3 times at once. The main one, GMT/UTC in upper middle and another one for selected city (showing TYO in above image). The home time can be set against any of world’s main cities. In above image, it was set for NYC. However, the GMT/UTC will always show UTC (in 24-hr mode) and you can’t set it to show any other time.

Casio AQ-S810W-1AVEF [£55] w08 Even though you can’t immediately recognize it, this is actually a world time watch! There is only one analog dial though. The second time is displayed digitally (not shown in above image). The digital time can be set for any of world’s main cities. However, you can easily toggle between home (analog) and secondary (digital) time zones. For example, if you set your analog hands for LON and digital for DEL and then you went to Delhi, then you can easily toggle analog hands to show Delhi time and digital one showing London time. This is a solar watch and also available with steel band.

 Nomos Glasute Tangomat GMT [£3100] w09 Another watch which, in spite of high price tag, can’t show true world times. The smaller window shows home/second city but because there is no secondary minute hand, it can’t show half hour GMT offset times. The main dial shows time for selected city (at 9’o clock position).

Ball World time GM2020D-LCJ-BK [£2400] w10 Another watch where Delhi is missing!

Vacheron Constantin Patrimony World Time [£26000] w11 This is another status symbol! This has got 37 world time zones (including half hour offsets which are marked in red). You can rotate the city name dials. In the above image, the home town is set for Geneva (because it points to black triangle at traditional 6-o’clock position). You can now read time at any of world’s cities in 24-hr format.

Blancpain Villeret [£9500]


As you can see in the dial, this one can show half hour GMT offsets. This is an automatic watch with 8 days of power reserve.   There are many other similar watches at varying price range. By now you must have got some good idea of what to look at world time watches. My advice: For functional and affordable watches, stick with Casio, Citizen or Seiko. For glamor statements, buy whatever your bank balance permits.

Why do smart phones freeze (or hang or lock up)?


Old Nokia phones (also known as dumb phones or features) almost never froze! I had a Nokia phone which froze only once (worked fine after restart) in 7 years of use! That is pretty impressive.

However, most smart phones often freeze. Some freeze quite often while some other freeze only occasionally.

Let us understand why it happens.

All smart phones are mini computers inside. They have an Operating System (OS) which interacts with the phone hardware. Users interact with the phone via application layers.

The core of OS is known as “kernel”. This is low level assembly language core which translates users’ requests (via apps) so that hardware can process it. For example, when you dial a number (via dialler app) the request is sent to kernel which instructs the hardware to perform the phone dialing operation. Both Android and iOS runs on highly customized flavors of Unix OS inside them.

The old dumb phones also had similar concept but there was a big difference. Those phones were only allowed to perform few predefined tasks like dialing a number, receiving phone calls and sending texts (along with alarm, calendar etc.).

But modern smart phones are expected to do a lot of things! As a result, it is often very difficult to predict what each app will request to kernel. There are just millions of instructions possible. When many apps send some instruction to kernel, it may get overloaded (takes too long to process which manifests as phone slow to respond) or just get confused (manifests as phone freezing). The freezing often happens due to kernel going into an infinite loop (and does not know how to come out of that) or just bogged down by too much work.

When you use heavy weight apps in lower end (or budget) smart phones, due to slow CPU and small amount of RAM, the hardware gets overloaded. So, those phones often become slow over times. When you install newer versions of apps, they usually take up more space and thus strains hardware even more!

Different manufactures try to handle this problem in different ways. Apple implements a strict control of what its apps are allowed to do and what hardware goes inside the phone. That’s why iOS is more restrictive and iOS users see less frequent freezing. Internally, iOS apps work in a sandbox mode. Each app gets a space in phone storage and it can’t access anything outside of its own sandbox. Once you delete the app, all its traces are gone. This is also the reason why users can’t access iOS file system (unless you jailbreak). Apple also doesn’t allow usage of external memory card which is often responsible for corrupt file systems and thus causing problems.

Android system (even though derived from Unix) is more like good old desktop Windows OS in its behavior. Apps can often access an equivalent of Windows registry style things. Various apps dump garbage in cache, which fills up phone’s internal storage (like hard disk) and phone becomes slower over time. Even if you install an app in SD card, it still leaves traces in internal storage space due to OS design. Android also allows access to file system (just like desktop PCs) which means users can fiddle with its system and may accidentally delete system files!

Microsoft has taken iOS like “sandbox” approach in its Windows phone system. So, in theory, Windows Phones are supposed to crash less! However, these still allow external SD cards so such issues will remain to some extent. Also, as Windows phones have less market share at present, it is difficult to predict if they are indeed superior to Android or iOS.

From empirical evidence, it can be stated that:

  • Apple phones crash the least. However, internet browsing is often unpredictable and quite often iOS browser just crashes but this does not usually lead to entire phone freezing up.
  • Blackberries and Android phones crash often. Lower end Android models crash more if you fiddle with them too much for the reason described in this article.
  • Less matured OS crashes more. For example, Windows phones OS have good architecture but it is still maturing so it may crash unexpectedly.
  • Poorly designed OS will crash often. This is why Nokia’s Symbian based smart phones were notorious for freezing!

If you are an Android user, make sure you clear cache often, manage your applications so that it does not store too much data in phone’s internal memory and refrain from heavy browsing or playing hardware heavy games. This should lead to less crash, especially in budget hardware Android models.

If you are an iOS user (iPhone or iPad), there is not much you can do to prevent freezing (if that happens at all). Sometimes one or two rogue apps may cause problem. In that case, simply get rid of those apps. Some apps when updated, tend to make use of newer features of latest OS. If your OS is older version, you may see apps crashing (but not entire device freezing up).

Windows phones are still maturing so nothing can be advised at this moment.

How a steam loco differs from diesel-electric loco?


A diesel-electric (DE) loco is a constant power machine. We know that, Power = Force x Velocity. This means, when hauling heavy loads (especially on an uphill), a DE loco can increase draw bar pull by reducing speed. This also shows why most shunting locos are DE locos as they need to haul heavy load but at low speed.


However, due to the way a steam loco is designed (i.e. its boiler, piston and other mechanisms), a steam loco behaves as a constant force machine up to cruising speed (usually around 25 MPH or 40 km/h). Beyond that, a steam loco behaves like a constant power machine like a DE loco.


This difference is crucial. For a steam loco to haul heavy load (or on an uphill), if it can’t deliver enough draw bar pull, it has no way to increase the force like a DE loco, because for steam loco, force is constant at low speed. So, a steam loco won’t be able to climb a slope like a DE loco. It will literally run out of puff under such circumstance. However, once a steam loco has crossed its cruising speed, it will have no problem pulling heavy trains as it behaves in same way as DE loco i.e. constant power loco.


There are obviously other differences between these two types of locos. A DE loco is more thermally efficient than a steam loco. The later requires far more maintenance than the former and needs more crews to operate them.


No wonder, due to these reasons, most of old steam locos have been replaced by DE locos in all but heritage routes. Please note that a pure electric loco will also behave similarly as of a DE loco.


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)

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.

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.

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.