Archive for the ‘Science’ Category

What are different types of watches?

2014/07/23

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.

How a steam loco differs from diesel-electric loco?

2013/09/23

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.

 

What is heart attack?

2012/09/29

The blood circulation in our bodies provides nutrition and oxygen to all cells. The muscles in heart are responsible for contraction and expansion of the heart. When enough oxygen do not reach to heart muscles, the heart cannot function properly. This usually happens when there are blocks or restriction to blood vessels, which carries blood to heart muscles. If heart cannot function properly it cannot push blood to other parts of the body, which in turn causes other body parts to malfunction. For this reason if heart attack is not treated immediately it can cause death.

There are several reasons why blockage occurs in blood vessels to heart. It can be due to age, lifestyle (like eating fatty food and not having enough exercise), genetic issue or other medical problems.

During heart attack, patients usually feel pain in chest and subsequently in many other body parts.

Heart attack is different from “stroke”. In heart attack, there is reduced blood flow to heart. In stroke, there is reduced blood flow to brain. Since brain controls functions of body, stroke is often associated with paralysis as a consequence. Since brain is divided broadly between left and right sections, stroke in one part of brain can often impair functionality of other side of the body (i.e. paralysis).

Both heart attack and stroke should be treated immediately as any delay can be fatal.

 

Air-cooled vs water cooled engine

2012/08/01

Most likely your modern car has a water-cooled engine. When an internal combustion engine operates, it creates high amount of heat. Unless there is a mechanism to dissipate the heat, it will damage the engine components. In modern automobile engines, a coolant system is used to keep the engine cool. Usually a chemical coolant is used (although named water cooled, water is not used anymore now as coolant) within a sealed system (you rarely need to top up). The cooling system creates a jacket outside the engine. It also keep the engine in constant temperature. The proof is your car’s temperature gauge which usually stays halfway to H and C mark.

In air-cooled engine, air is used to cool the engine down. Thus, it does not require radiator and cooling system – which makes the whole engine a lot simpler. It uses radiator fins (easy to see in motorcycles) which are used to cool the engine. But there are drawbacks too. Unless there is steady flow of air, the engine may get overheat quickly. They are also very noisy as the radiators fins vibrate when engine is in operation.

Air-cooled engines are used mainly in motorcycles, some 3-wheels (like India’s Bajaj autorickshaws), some cars (classic VW Beetle, old Porsches etc.) and some propeller aircrafts.

For aircrafts, they are not a big problem. Unlike a car, an aircraft does not get stuck in traffic jams. Aircraft engines operate within their 80-100% RPM range most of the time and due to high speed cruising plenty of air pass over the radiator fins to keep them cool. This also explains why old propeller aircrafts with such engine sound so loud.

But problem might happen in air-cooled car engines! If the car is stuck in traffic or moving slowly over extended period of time, the engine may overheat (which may lead to seizure of engine).  On the other hand, they are quite good at cold weather condition as chance of overheating is lower.

 

Why auto stop start is modern cars?

2012/07/16

Many new cars of today feature auto stop start feature. This is also known as Intelligent Stop and Go and similar names.

Cars with this feature, turns of engine as soon as you stop and take your foot off the clutch. Then as soon as you press clutch again to engage the gear, it switches on the engine.

Manufacturers do this because they claim it saves fuel while waiting in traffic.  This also allows them to quote higher fuel economy figures and CO2 emission (on which most cars are taxed nowadays). This makes these cars statistically more attractive (because of lower fuel consumption and tax) to the buyers.

On the other hand, many drivers find it as a psychological challenge. It also requires a stronger (thus more expensive) battery and starter motor. So how much money is saved at the end (for drivers) is open to debate.

Fortunately, if you do not like this feature, it can usually be turned off via a switch on dashboard.

As of now, automatic cars do not have this feature but in future this may be offered in autos as well.

 

CERN, Higgs Boson and God particle

2012/07/04

Let’s first explain what is Higgs field. It is something which gives different masses to various sub atomic particles.

Now we explain this in detail.

Imagine a fighter plane moves and a jumbo jet are moving thru air (with similar powered engine). Which one will move easily? Obviously the fighter plane because it is lighter and more streamlined. The air provides more resistance to large and heavy objects. However, if there is no air i.e. they are both moving thru vacuum, they will both get no resistance and their shape will not dictate which one will move faster.

When Big Bang happened, all particles were mass-less and they were flying in all directions symmetrically at speed of light (because nothing was slowing them down). But within one trillionth of a second, a new field (which is Higgs field) was formed which gave mass to particles – some became heavier and some lighter, which broke the symmetry and particles started moving in different directions at different pace. So Higgs field here is analogous to the air (i.e. something which gives resistance) in the example in last paragraph.

Remember, classical physics depend heavily on gravity i.e. how to particles attract each other. However, if the particles have no mass, then gravitational theory falls apart. Simply speaking, it is the Higgs field which gives mass to particles, which in turn causes gravity to work and which in turn make theories of physics stick together.

So how Higgs field exactly give mass to particles? If I could explain that I would have probably received Nobel prize now. But at least I can give you another analogy.

Imagine you are waiting in airport lounge (i.e. among the masses) and you don’t know any of your co-passengers. Suddenly you discover 2 of your old friends and they started chatting with you after sitting nearby to you. Suddenly a well known film star entered the lounge. Many of the passengers instantly recognize her and suddenly a large group of people formed a crowed centering the celebrity. Thus, the celebrity is attracting more mass than you are attracting with your two friends. Thus Higgs field give mass to different particles – more mass to a celebrity particle and less mass to an average Joe particle.

Higgs Boson is a new kind of particle which gives mass to sub-atomic particles. The scientists at CERN have found something which may be Higgs Boson. But they need to conduct lots of experiments to confirm it is really Higgs Boson.

Again I give you an analogy. Suppose you are clearing your loft and discovered an ancient flower vase. This can be very expensive but only an antique dealer can confirm whether it really worth hundreds or you can just throw it away. So scientists still need to verify if they really found the particle or it was something else.

Some media term this as “God particle”. This is because discovery of this particle will explain how particles get mass which is foundation of classical physics.

Why this discovery is important? Because this can open potentially unlimited new horizons. For example, because aircraft was invented you can how move between continents in a day or because of electricity can read this in your computer. Similar way, this discovery can lead to various benefits for mankind in the fields of science, medicine etc.

Let me take this opportunity to explain what CERN is doing with Large Hadron Collider. In simple terms, they are trying to knock two rocks and sifting the debris to discover what is the smallest particle they could find. They are also trying to create a mini Big Bang to discover what happened that very moment. In fact, most of particles of world today were formed within millisecond of Big Bang happening.

PS: This topic is indeed too difficult to explain in simple terms. But I tried my best. Please let me know if you find any error in the explanation.

Why passengers are not provided parachutes in commercial flights?

2012/07/01

It is a common question asked by many as people believe having a parachute for everyone will save lives if plane crashes!

However, even if parachutes are provided to all passengers, it is very unlikely than anyone will survive if a modern commercial airliner crashes.

Proper use of parachutes requires sufficient training, skill and nerve. If a plane crashes, there will huge panic on board and everyone will rush towards doors to deploy parachutes. Even in military aircrafts, it takes several minutes for every soldier to jump off with parachutes in an orderly manner.

Besides this, all passengers will have to sit wearing the parachutes all the time (you can’t really wear it like your coat). This will be very uncomfortable for long haul flights.

For parachutes to work, the aircraft must slow down to a required speed, otherwise parachuters might hits towards rear of the aircraft.

Leaving the aircraft in the sky often is more dangerous compared to staying inside. A novice passenger even with parachutes are very vulnerable.  It will be very cold outside and you may not be able to breath properly. An expert pilot might manage to land the plane safely even after major trouble.

Modern flights are quite safe although unfortunate incidents do happen, the probability of plane crashing is very low.  For the reasons cited above, providing parachutes to all passengers won’t server any real benefit and that is why they are not provided to passengers.

Some very small aircrafts (usually less than 8 seats) do have parachutes for all passengers. In fact, some small aircrafts have mechanism of having a parachute for the whole aircraft itself. Obviously, large aircrafts can’t have this because of their massive weight.

 

Why earth spins?

2012/06/30

We know that scientists told us the planets were formed when part of Sun was torn by another massive star passing by. As the parts which made earth (and other planets) were spinning, laws of conservation of angular momentum dictates that unless some external force stops the motion, it will continue to spin. Thus, as nothing is stopping earth from spinning (there is no friction in space), the earth continues to spin even after billions of years!

Good that earth spins otherwise we would not have been here 🙂

Even better news that for same reason earth will go on spinning in same way another few billion years.

PS: Strictly speaking, there is very very very slight friction in space because of cosmic particles. This is indeed causing earth’s rotation to slow down by miniscule amount. For this reason, a new second was added to universal time in June 2012.

How does day light saving work?

2012/05/30

If Daylight Saving Time (DST) is not in operation, then during the middle of year (May-Aug), the Sun will rise in UK around 05:00 will set around 19:00.

If we use DST, then clock will go 1 hour forward so that it will appear that Sun rises at 06:00 and sets at 20:00.

This means, you can switch on your lights in your house after 1 hour every evening (well, sort of).

So this will give you one extra hour of daylight every day. For most people it is a benefit.

However, if you have the habit of getting up very early, then you will have to switch on the light (if you get up at 05:00, till 06:00). That means, even though we are saving day light in the evening, we are losing day light in the morning.

As most of the people do their own entertainment in the evening (after finishing off work), it is argued that DST gives more daylight to most number of people. People are expected to spend more time outdoor and likely to buy stuffs till there is light, which indicates a more active economy.

Of course, same benefit can be achieved by re-adjusting opening and closing hours of business, say 09:00-17:00 instead of 08:00-16:00.

Ok, so if day light is saved by making clock fast forward, why not observe the same time thruout the year?

This will cause problem during winter. The Sun will appear at a later time – which will force children to go to school during dark hours in early morning. In fact, this is one argument often used in favor of turning clock back during winter. As clock goes back, the evenings will become darker sooner (e.g. at 16:00 eveything becomes dark when UK follows GMT during winter). That means, all the day light hours saved during summer are lost in winter! Supporters of dual time argues that during winter no body wants to be outside anyway so no harm if it becomes dark sooner. To some extent, it is true.

What is the best color for taxis?

2012/05/19

Usually taxis are yellow because yellow is the best color to spot easily from a distance.

For this reason, most taxis around the world are yellow. But some other colors are used too.

Usually you can hail taxis on road. For these cabs, it is best if they are yellow. But other private hire vehicles cannot often be hailed on road. So it hardly matters what color they are painted.

But sometimes main city cabs are not painted yellow. The reason might be historical or the civic authority did not bother to address the problem in a scientific way.

For example London cabs are usually black. In some other towns taxis are painted in white, blue, green or multiple shades.