STRATIFIED CHARGE INTERNAL COMBUSTION ENGINE

Google Patent wrote on the page as Abstract ideas about stratified charge engine. Google Patent

An internal combustion engine is disclosed having a cylinder and a reciprocating piston which, together with the cylinder head, define the boundaries of a combustion chamber.
A movable septum is supported by the cylinder head adjacent the combustion chamber for selectively dividing the combustion chamber into a first and second combustion chamber. The movable septum may be formed by a cylindrical plate or by a flat or curved plate which makes nominal contact with the walls of the cylinder and the face of the reciprocating piston to divide the combustion chamber.
The fuel supply system provides a rich-fuel mixture through a rich mixture intake valve to the first combustion chamber, and a lean-fuel mixture through a lean mixture intake valve to the second combustion chamber.
The movable septum tracks the movement of the reciprocating piston during the compression stroke to maintain the division between the first and second combustion chambers. However, just prior to the power stroke, the actuator retracts the movable septum from the combustion chamber, and the spark plug ignites the rich air-fuel mixture which then ignites the lean air-fuel mixture to complete the power stroke. During the exhaust stroke of the reciprocating piston, the movable septum is maintained in a retracted position. As a result, effective stratification is achieved between the first and second combustion chambers.

Lecture Note:

STRATIFIED CHARGE ENGINE

Internal combustion engines or popularly known as IC Engines are life line of human society which mostly served as a mobile, portable energy generator and extensively used in the transportation around the world.
There are many types of IC Engines, but among them two types known as petrol or SI engines and diesel or CI engines are well established. Most of the automotive vehicles run on either of the engines. Despite their wide popularity and extensive uses, they are not fault free. Both SI Engines and CI Engines have their own demerits and limitations.

Limitations of SI Engines (Petrol Engines)

Although petrol engines have very good full load power characteristics, but they show very poor performances when run on part load. Petrol engines have high degree of air utilisation and high speed and flexibility but they can not be used for high compression ratio due to knocking and detonation. Limitations of CI or Diesel Engines: On the other hand, Diesel engines show very good part load characteristics but very poor air utilisation, and produces unburnt particulate matters in their exhaust. They also show low smoke limited power and higher weight to power ratio. The use of very high compression ratio for better starting and good combustion a wide range of engine operation is one of the most important compulsion in diesel engines. High compression ratio creates additional problems of high maintenance cost and high losses in diesel engine operation. For an automotive engine both part load efficiency and power at full load are very important issues as 90% of their operating cycle, the engines work under part load conditions and maximum power output at full load controls the speed, acceleration and other vital characteristics of the vehicle performance. Both the Petrol and Diesel engines fail to meet the both of the requirements as petrol engines show good efficiency at full load but very poor at part load conditions, where as diesel engines show remarkable performance at part load but fail to achieve good efficiency at full load conditions. Therefore, there is a need to develop an engine which can combines the advantages of both petrol and diesel engines and at the same time avoids their disadvantages as far as possible.

Working Procedures:

Stratified charged engine is an attempt in this direction. It is an engine which is at mid way between the homogeneous charge SI engines and heterogeneous charge CI engines. Charge Stratification means providing different fuel-air mixture strengths at various places inside the combustion chamber. It provides a relatively rich mixture at and in the vicinity of spark plug, where as a leaner mixture in the rest of the combustion chamber. Hence, we can say that fuel-air mixture in a stratified charge engine is distributed in layers or stratas of different mixture strengths across the combustion chamber and burns overall a leaner fuel-air mixture although it provides a rich fuel-air mixture at and around spark plug.

THERMODYNAMICS - THEORY

Curves in Thermodynamics:

Thermodynamics can be understood with the help of the curves, where each curve represents a specific process. 
In general curves are plotted in a coordinate system where X axis and Y axis represent thermodynamic variables, often two conjugate variables. 
The state of a thermodynamic system can be fully specified by the values of any two conjugate thermodynamic properties. 
Therefore, in a coordinate plane where 
X and Y axes are replaced by any two conjugate thermodymanic properties, each point will represent an unique thermodynamic equilibrium states. Hence, curves joining any arbitrary two points on this plane will represent a thermodynamic processes. 


The curves those are used most: 

In thermodynamics, p-v diagrams, 
T-s diagrams, h-s diagrams are the important diagrams. h-s diagrams of water is also known as Mollier Chart. Curves play a crucial role in studying Thermodynamics.

In thernodynamics all the possible types of processes which are reversible can be represented by a mathemetical relation hence, can be plotted in different thermodynamic planes. It can be represented by a relation pvⁿ = constant and called polytropic process.






In the second law analysis, it is useful to plot the process on diagrams for which has one coordinate is entropy. The two diagrams commonly used in second law analysis are temperature-entropy (T-s) and enthalpy-entropy (h-s) diagrams. For some pure substance, like water, the entropy is tabulated with other properties.

The T-s Diagrams and its importance

On a P-v diagram, the area under the process curve is equal, in magnitude, to the work done during a quasi-equilibrium expansion or compression process of a closed system. On a T-s diagram, the area under an internally reversible process curve is equal, in magnitude, to the heat transferred between the system and its surroundings. That is,

The T-s diagram of a Carnot cycle is shown on the above figure. The area under process curve 1-2 (area 1-2-B-A-1) equals the heat input from a source (Q_H). The area under process curve 3-4 (area 4-3-B-A-4) equals the heat rejected to a sink (Q_L). The area enclosed by the 4 processes (area 1-2-3-4-1) equals the net heat gained during the cycle, which is also the net work output.

IC ENGINES: A CONCEPTUAL ANALYSIS

• INTRODUCTION: 

The idea of engines come from heat engines. Expanding steam was the working substance of the primitive kind of Steam Engines. But, locomotion was tough using steam engines as it needed continuous supply of water and coal as fuel. People started to think about a compact engines, light and portable and combustion will be the basis of heat generation. If heat generation could be taken place inside the cylinder, then it will be easier to design a compact engine which could be used to run a locomotive vehicle.

This semester, I am teaching IC Engines and Compressors. The text book is selected as IC Engines by Sharma and Mathur published by Dhanpat Rai Publications. The course is designed by MTU (Mahamaya Technical University, Noida and Gautam Budh Technical University) and it is taught in 5th semester. Although it is a 50 marks paper, still it is a subject which every Mechanical Engineering students must know. It is completely based on the principles of thermodynamics.

The course starts with defining IC Engines, introducing the components used in IC engines, different terms and processes related with IC engines, general working procedures of an IC engine and at last describing the classification of IC engines. Then the thermodynamic analysis of the engine operations along with Air-standard thermodynamic cycles are studied. If any one wants to know the subject deeply, then he should know very basic concepts of thermodynamics. 

• PRE-REQUISITE KNOWLEDGE:

As air-standard cycles are one of the basic models based on which engines are practically run and is a highly simplified or even oversimplified version of the original engine operation and due to this, the experimental values of the engine efficiencies are much below the value predicted by the air standard cycles. The large amount of deviations of actual cycles from the theoretical air standard cycles are due to assumptions taken during air standard cycle analysis.

• DESCRIPTION OF THE IC ENGINE:

While describing IC engines, one should start with the engine cylinder which acts as the combustion chamber which has a variable volume due to a piston which can slide inside the cylinder. 

One end of the cylinder is sealed off by cylinder head which provides the space for clearance volume and it also housed the inlet and exhaust valves. 

The other end of the cylinder is covered by the piston which can slide along the principal axis of the cylinder. 

Inside the cylinder air-fuel mixture is sucked into and then compressed it in case of SI engines, where as in CI engine only air is sucked into the cylinder. 

The piston is connected to a link known as Connecting rod by a pin named Gudgeon or Piston or Wrist pin. 

This connecting rod has unequal ends. The smaller end is connected to piston by gudgeon pin and the bigger end is connected to the eccentric on the Crank. 

It is joined to the eccentric by a pin named Crank pin. Piston, Connecting Rod and Crank constitute a "Slider-Crank Mechanism" which translates a linear "to and fro motion" of the piston into "rotational motion" of the crank. 

Here, connecting rod is the element that bears the whole load, hence it fails quite frequently. 

Crank is mounted on a crank shaft and crank shaft operates two valve mechanism through poppet valve, rocket arm and cams. 

These valve mechanisms are responsible for the opening and closing of inlet as well as exhaust valves. 

This valves are regulated by cams. Cams are mounted on a cam shaft which is geared with crankshaft by a step down gear mechanism so that for every two revolutions of crankshaft rotation the camshaft makes one rotation. So, the complete thermodynamic cycle of two crankshaft rotation crankshaft makes only one cycle. The idea behind this step down mechanism, is valves are needed to open and close once in a complete thermodynamic cycle and a cam profile can be designed easily. 

A flywheel is mounted on the crankshaft, so that it can absorb and store energy during power stroke or expansion stroke and releases energy to power suction, compression and exhaust stroke.

In SI engine, after the end of compression stroke, the pressure and temperature of the air-fuel mixture becomes sufficiently high to sustain the ignition process after ignition takes place. After the compression pressure becomes 10 to 12 bar and temperature becomes 300^o C to 500^o C. It is still below the temperature at which spontaneous auto-ignition generally starts. If the temperature after compression is above the temperature at which auto ignition starts, then auto ignition will start during the last phases of compression stroke and it will create an explosion known as knocking and detonation.

Then theoretical basis of an IC engines are discussed. While analyzing any phenomena, the best way is to make an idealized modelling of the phenomena by considering certain assumptions which would reduce the complexity of the phenomena and make a oversimplified model and then add the complexity one by one. 

Similarly, here we oversimplified the model of IC engine operation by considering the working substance an ideal gas like air and study some reversible thermodynamic cycles those resemble with the processes those occurs inside an IC engine. 

As those cycles are considered having air as working substance and hence, they are called Air-Standard cycles. But, as Air-Standard Cycle are the idealized version of the real life working principle of an IC engines, its analysis can not be used to gauge the performances of the engine with closest accuracy.

 
Thermodynamic Air-standard cycles like Otto, Diesel, Dual, Stirling and Ericsson cycles are discussed. 

Derivation of total work done, Efficiency, Mean Effective Pressure and graphs in p-v and T-s diagrams are studied.

 
In the air standard cycles, working substance is assumed to be perfect gas like pure air, but in actual cycles the working substance is different and it is the mixture of air and fuels. In air standard cycle it is assumed that specific heats are constant where as in reality, specific heats are functions of temperature and it increases with the increase of temperature. 

Moreover, in air standard cycle, it is assumed that working substance is chemically non-reactive and there is no chemical changes inside the engine cylinder, but in reality, inside the cylinder combustion process takes place and the chemical composition of the working substance rapidly changes during the combustion process which alters the composition as well as number of moles of the working substances also got changed.

The combined effect of both the phenomena is to reduce the temperature and pressure after the end of compression stroke as well as it reduces the maximum cycle temperature and pressure after the end of combustion. 

While expanding adiabatically during the power stroke, the temperature and pressure after expansion is higher than the predicted value according to air standard cycle and as a result it increases the value of rejected heat into the thermal sink. 

Therefore, the actual cycle efficiency is much lower than the air standard cycle efficiency. Moreover, there are several other losses during the actual cycle due to various other design limitations. The major losses are 

• (i) burning time losses, 
• (ii) losses due to incomplete combustion, 
• (iii) Direct heat losses due to colder cylinder and heat carried away by coolants, 
• (iv) pumping losses, 
• (v) friction losses due to rubbing of parts, 
• (vi) blow down losses during exhaust.

So, we have first idealized the engine operations and oversimplified it to have an idealized version, but its prediction will not be accurate, but we shall get an upper limit of the efficiencies of IC engines. Now, to get more accurate analysis, we shall modified the simplistic assumptions we have considered during the air standard cycles analysis.

The most important assumption of the air standard cycle is the choosing pure air as our working substance, which is in reality a mixture of air with fuel, which has been mixed homogeneously in the carburettor and then supplied into the engine cylinder which acts as combustion chamber. Therefore, we first substitute air with the air fuel mixture in the air standard cycles and it is hence called "Fuel Air Cycles".

Due to the replacement of working substance by air fuel mixture in stead of pure air, our two key assumptions have been changed too. First of all, fuel-air mixture doesn't show a constant specific heats in stead specific heats are functions of temperature, linearly at low temperatures, non linearly at high temperatures.

C_p = aT² + bT + k

C_v = cT² + dT + k'

STRATIFIED CHARGE INTERNAL COMBUSTION ENGINE

Internal combustion engines or popularly known as IC Engines are life line of human society which mostly served as a mobile, portable energy generator and extensively used in the transportation around the world. 

There are many types of IC Engines, but among them two types known as petrol or SI engines and diesel or CI engines are well established. Most of the automotive vehicles run on either of the engines. Despite their wide popularity and extensive uses, they are not fault free. 

Both SI Engines and CI Engines have their own demerits and limitations. 


Limitations of SI Engines (Petrol Engines) 

Although petrol engines have very good full load power characteristics, but they show very poor performances when run on part load. 

Petrol engines have high degree of air utilisation and high speed and flexibility but they can not be used for high compression ratio due to knocking and detonation. 

Limitations of CI or Diesel Engines: 

On the other hand, Diesel engines show very good part load characteristics but very poor air utilisation, and produces unburnt particulate matters in their exhaust. They also show low smoke limited power and higher weight to power ratio. 

The use of very high compression ratio for better starting and good combustion a wide range of engine operation is one of the most important compulsion in diesel engines. High compression ratio creates additional problems of high maintenance cost and high losses in diesel engine operation. 

For an automotive engine both part load efficiency and power at full load are very important issues as 90% of their operating cycle, the engines work under part load conditions and maximum power output at full load controls the speed, acceleration and other vital characteristics of the vehicle performance. 

Both the Petrol and Diesel engines fail to meet the both of the requirements as petrol engines show good efficiency at full load but very poor at part load conditions, where as diesel engines show remarkable performance at part load but fail to achieve good efficiency at full load conditions. 

Therefore, there is a need to develop an engine which can combines the advantages of both petrol and diesel engines and at the same time avoids their disadvantages as far as possible. 

Working Procedures: 

Stratified charged engine is an attempt in this direction. It is an engine which is at mid way between the homogeneous charge SI engines and heterogeneous charge CI engines. 

Charge Stratification means providing different fuel-air mixture strengths at various places inside the combustion chamber. 

It provides a relatively rich mixture at and in the vicinity of spark plug, where as a leaner mixture in the rest of the combustion chamber. 

Hence, we can say that fuel-air mixture in a stratified charge engine is distributed in layers or stratas of different mixture strengths across the combustion chamber and burns overall a leaner fuel-air mixture although it provides a rich fuel-air mixture at and around spark plug. 

THE IMPORTANCE OF MANUFACTURING ENGINEERING

If we carefully think about human civilization, one shall notice an wonderful fact about human beings. The thing that made us different from other hominids is the skill to manufacture tools. We just triumphed due to our ability to make primitive tools out of stone and metals during the dawn of the civilizations. Since then much time has passed and we have entered into a Machine Era and man has been still continuously engaged in converting the natural resources into useful products by adding value to them through machining and other engineering activities applying on the raw materials. Manufacturing is the sub branch of Engineering which involves the conversion of raw materials into finished products.

The conversion of natural resources into raw materials is normally taken care of by two sub branches of engineering viz. Mining and Metallurgy Engineering. The value addition to the raw materials by shaping and transforming it to final products generally involves several distinct processes like castings, forming, forging, machining, joining, assembling and finishing to obtain a completely finished product.

Understanding Manufacturing Engineering largely based upon three engineering activities and they are Designing,  Production and Development of new more efficient techniques.

At the Design stage, engineering design mainly concentrates on the optimization of engineering activities to achieve most economical way to manufacture a goods from raw materials. It also chooses the raw materials and impart the requisite engineering properties of materials like hardness, strength, elasticity, toughness by applying various heat treatment to them.

During the production stages, the selection of the important process parameters to minimize the idle time and cost, and maximizing the production and its quality is very important.

The New Technologies must be implemented to adapt to the changing scenarios of the markets and demands to make the sales competitive and sustainable.

ELEMENTS OF C PROGRAMMING

Q) Write a C programme to check a odd or even number

A) c program to check odd or even:

We will determine whether a number is odd or even by using different methods all are provided with a code in c language. As you have study in mathematics that in decimal number system even numbers are divisible by 2 while odd are not so we may use modulus operator(%) which returns remainder, For example 4%3 gives 1 ( remainder when four is divided by three). Even numbers are of the form 2*p and odd are of the form (2*p+1) where p is is an integer. C program to check odd or even using modulus operator

#include<stdio.h>
main()
{
int n;
printf("Enter an integer\n");
scanf("%d",&n);
if ( n%2 == 0 )
printf("Even\n");
else
printf("Odd\n");
return 0;
}

We can use bitwise AND (&) operator to check
odd or even, as an example consider binary of 7
(0111) when we perform 7 & 1 the result will be
one and you may observe that the least
significant bit of every odd number is 1, so
( odd_number & 1 ) will be one always and also
( even_number & 1 ) is zero.
C program to check odd or even using bitwise
operator

#include<stdio.h>
main()
{
int n;
printf("Enter an integer\n");
scanf("%d",&n);
if ( n & 1 == 1 )
printf("Odd\n");
else
printf("Even\n");
return 0;
}

Find odd or even using conditional operator

#include<stdio.h>
main()
{
int n;
printf("Input an integer\n");
scanf("%d",&n);
n%2 == 0 ? printf("Even\n") : printf("Odd\n");
return 0;
}

C program to check odd or even without using
bitwise or modulus operator

#include<stdio.h>
main()
{
int n;
printf("Enter an integer\n");
scanf("%d",&n);
if ( (n/2)*2 == n )
printf("Even\n");
else
printf("Odd\n");
return 0;
}

In c programming language when we divide two
integers we get an integer result, For example
the result of 7/3 will be 2.So we can take
advantage of this and may use it to find whether
the number is odd or even. Consider an integer
n we can first divide by 2 and then multiply it by
2 if the result is the original number then the
number is even otherwise the number is odd.
For example 11/2 = 5, 5*2 = 10 ( which is not
equal to eleven), now consider 12/2 = 6 and 6 *2
= 12 ( same as original number). These are some
logic which may help you in finding if a number
is odd or not.

Q) Write a C program to check whether input
alphabet is a vowel or not.

A) This code checks whether an input alphabet
is a vowel or not. Both lower-case and upper-
case are checked.

#include <stdio.h>
int main()
{
char ch;
printf("Enter a character\n");
scanf("%c", &ch);
if (ch == 'a' || ch == 'A' || ch == 'e' || ch == 'E' ||
ch == 'i' || ch == 'I' || ch =='o' || ch=='O' || ch ==
'u' || ch == 'U')
printf("%c is a vowel.\n", ch);
else
printf("%c is not a vowel.\n", ch);
return 0;
}

Check vowel using switch statement

#include <stdio.h>
int main()
{
char ch;
printf("Input a character\n");
scanf("%c", &ch);
switch(ch)
{
case 'a':
case 'A':
case 'e':
case 'E':
case 'i':
case 'I':
case 'o':
case 'O':
case 'u':
case 'U':
printf("%c is a vowel.\n", ch);
break;
default:
printf("%c is not a vowel.\n", ch);
}
return 0;
}
Function to check vowel
int check_vowel(char a)
{
if (a >= 'A' && a <= 'Z')
a = a + 'a' - 'A'; /* Converting to lower case or
use a = a + 32 */
if (a == 'a' || a == 'e' || a == 'i' || a == 'o' || a == 'u')
return 1;
return 0;
}
This function can also be used to check if a
character is a consonant or not, if it's not a
vowel then it will be a consonant, but make sure
that the character is an alphabet not a special
character.
Q) Write C program to perform addition,
subtraction, multiplication and division.
A) C program to perform basic arithmetic
operations which are addition, subtraction,
multiplication and division of two numbers.
Numbers are assumed to be integers and will be
entered by the user.
#include <stdio.h>
int main()
{
int first, second, add, subtract, multiply;
float divide;
printf("Enter two integers\n");
scanf("%d%d", &first, &second);
add = first + second;
subtract = first - second;
multiply = first * second;
divide = first / (float)second; //typecasting
printf("Sum = %d\n",add);
printf("Difference = %d\n",subtract);
printf("Multiplication = %d\n",multiply);
printf("Division = %.2f\n",divide);
return 0;
}
In c language when we divide two integers we
get integer result for example 5/2 evaluates to 2.
As a general rule integer/integer = integer and
float/integer = float or integer/float = float. So
we convert denominator to float in our program,
you may also write float in numerator. This
explicit conversion is known as typecasting.
Q) Write a C programme to check a Leap year.
A) C program to check leap year: c code to
check leap year, year will be entered by the
user.
#include <stdio.h>
int main()
{
int year;
printf("Enter a year to check if it is a leap year
\n");
scanf("%d", &year);
if ( year%400 == 0)
printf("%d is a leap year.\n", year);
else if ( year%100 == 0)
printf("%d is not a leap year.\n", year);
else if ( year%4 == 0 )
printf("%d is a leap year.\n", year);
else
printf("%d is not a leap year.\n", year);
return 0;
}

সময় কি এবং সময়ের অস্তিত্বের কারণ কি ?

এক সময় পদার্থ বিদ্যায় সময় কে আমাদের মস্তিস্কর উপজ বলে চিহ্নিত করা হত । তখনকার দিনে  বলা হতো সময় ঠিক করে বলতে গেলে এমন একটা জিনিস যা একসঙ্গে  সবকিছুকে ঘটতে দেয়না । এমন কি  আলবার্ট আইনস্টাইন বলেছিলেন  যে এই জগতে অতীত  এবং ভবিষ্যত এক মরিচিকা  ছাড়া আর কিছুই নয়, মানুষের ভ্রম মাত্র । কিন্তু  সত্যি করে বলতে গেলে  সময় কি আর কেন আমরা সময় কে উপলব্ধি করতে পারি তার কোনো সঠিক ব্যাখ্যা  নেই ।



তবে সম্প্রতি পদার্থ বিজ্ঞানীরা এটা বের করার চেষ্টা করছেন যে সত্যি সত্যি  বলতে গেলে কেন এই বিশাল বিশ্ব ব্রহ্মান্ড সময়ের উপর নির্ভরশীল । কেন আমরা সময়ের গতিকে পরিচালিত করতে পারিনা, কেন এই বিশ্ব ব্রহ্মান্ড সুচারু রূপে  চলতে গেলে সময়ের উপর নির্ভরশীল হয়ে পরে ? কেও কেও আবার বলছেন সময় বলে কিছু নেই যা অবিরত চলতে থাকে , বরঞ্চ এটা  বলা যেতে পারে কি সময় অনেকটা বালুকা দানার মতন । আবার কিছু মানুষ আছেন যারা বলে চলেছেন যে সময়ের একটি নয় বরঞ্চ দুটি দিক আছে ।

Once upon a time, physicists liked to dismiss those who dwelled too much on the passing of the seconds, days and years. They wrote off the apparent flow of time as a trick of the mind. They joked that time is what keeps everything from happening at once. Albert Einstein, who believed the distinction between the past and future is an illusion, declared that time is “what you measure with a clock”.

In recent years, however, physicists have been working around the clock to find out what makes the cosmos tick. Some suggest that there is not a continuous flow of time, but rather spacetime moments trickling like grains of sand through an hourglass. Others say that there should be two dimensions of time, not one (so called “hypertime” jettisons the pesky headache of time travel, which is allowed by current theory); or that time, not being fundamental, was born in the Big Bang and could grind to a halt in a few billion years; or, according to the British philosopher Julian Barbour, time does not exist because we dwell within a heap of moments, each an instant of frozen time.

Quite a few feel that an overhaul of what we mean by “time” could lead to the next great leap in physics. Among them is Lee Smolin, of the Perimeter Institute for Theoretical Physics in Canada. Smolin argues that science is blighted by what he says are unreal and inessential conceptions of time. He insists that “time is real” and that its reformulation could be central to finding the long-sought after “theory of everything”.

In Time Reborn, he offers an entertaining, head-spinning and, yes, timely blend of philosophy, science, and speculation to put the Now back into physics.

The problem with time dates back centuries. The physical laws outlined by greatest figure of the Scientific Revolution, Isaac Newton, are indifferent to the direction of time and suggest the future is determined by the past. Thus, as the French mathematician Pierre-Simon Laplacefamously pointed out, we may regard the present state of the universe as the effect of its past and the cause of its future. And if our future’s already written, then the things that are most valuable about being human are illusions, along with time itself.

Ever since Newton, physicists have been developing ever more exact laws describing the behaviours of the world. These laws don’t change. They are more real than time. They are timeless truths. “If laws are outside of time, then they’re inexplicable,” says Smolin. “If we want to understand law then law must evolve, law must change, law must be subject to time. Law then emerges from time and is subject to time rather than the reverse.”

He cites heavyweights such as the Briton Paul Dirac and the American philosopher Charles Sanders Peirce who have also suggested that the laws of physics evolve. In an earlier book, Smolin outlined one somewhat hairy scheme to explain how this may occur: universes reproduce inside black holes and, as in Darwin’s natural selection, those with parameters for spawning new black holes have offspring; those that do not fizzle out. The laws become fine-tuned, changes accumulating each time a baby cosmos is born. This daisy chain of descendant universes unfolds in time, and Smolin believes that this is real time.

Guided by an insight from Newton's great rival, Gottfried Leibnitz, Smolin’s picture of the cosmos violates Einstein's relativity because it requires an absolute time, preferred global time. To make time real, he also puts forward a weird idea, “the principle of precedence”, that repeated measurements of a certain phenomenon yield the same outcomes not because it obeys a law of nature but simply because the phenomenon is a habit. This would allow new measurements to yield new outcomes, not predictable from knowledge of the past.Thus the future becomes open once more.

A few years ago, Smolin triggered much heated debate with The Trouble with Physics in which he argued that attempts to explain the fundamentals of the universe by the dominant paradigm of so-called string theory, which comes in many flavours, remain untested “because they make no clean predictions or because the predictions they do make are not testable”. The problem is that the ideas in Time Reborn feel just as wildly speculative, if not more so.

Still, his maverick meditations serve as a reminder that it’s hard to find a consensus on the future of physics at an exciting time when it feels like everything could be altered in an eye-blink by the findings from extraordinary experiments under way to probe the puzzles of dark matter, dark energy, antimatter and more. That is the physicists’ ultimate arrow of time, pointing from today’s understanding towards the next great mystery.