Physics‎ > ‎

Book reviews.

posted Jan 9, 2018, 11:04 AM by Upali Salpadoru   [ updated Aug 15, 2019, 11:05 PM ]

1. A briefer History of Time.

by Stephen Hawking


Comment:- The Universe in a nutshell.


             Richard Feynman has said “ We are lucky to live in an age in which we are discovering the fundamental laws of nature”.....Our goal in writing this book is to share some of the excitement.

Chapter 1. Thinking about the universe.

         The nearest star other than the sun is ‘Alpha (Proxima) Centauri’ which is about 4 light years away. Fastest space ship would take 10,000 years to reach it.

Did the universe have a beginning, and if so what happened before then? What is the nature of time?....Can we go back in time?

Chapter 2. Our evolving picture of the universe.

         Discusses the findings and views of great astronomers from Ancient Greece to Sir Isaac Newton. “ We had given up not only the idea that the Earth is the centre of the universe but even the idea that our sun. The change in worldview represented a profound transition in human thought; the beginning of our modern scientific understanding of the universe.

Chapter 3.  The nature of a scientific theory.

         Any physical theory is always provisional. You can never prove it…...You can disprove a theory by finding a single observation that disagree with the predictions of the theory.

          Today scientists describe the universe in terms of two basic theories.

  1. The general theory of relativity describes the force of gravity and the structure on scales from few miles to 10 23  miles

  2. quantum mechanics.  Deals with millionth of millions of an inch.

Chapter 4. Newton’s Universe.

             This chapter explains the laws of Newton. ...Both Aristotle and Newton believed in absolute time….In the 20th  C . physicists realised that they had to change their ideas about space and time. .. They discovered that ..time between events ,like the distance depends on the observer. They also discovered that time was not completely separate and independent of space. ...although our common sense notions work well when dealing with things such as apples or planets, ….they don’t work at all for things moving at or near the speed of light.

Chapter 5. Relativity.

             The fact that light travels at a finite speed was first discovered by Ole Christensen Roemer in 1676. His value was 140,000. Miles / second while the modern value is 186,000. Miles /sec.

In 1865 Maxwell’s equations predicted that there could be waves in the electromagnetic field. The speed of these was that of the speed of light.

                 In 1887 Michelson and  Morley found that the speed of light does not change with the speed of the earth.In 1905 Einstein’s theory of relativity threw some light on this.

Chapter 6. Curved space.

Chapter 7. The expanding Universe.

             What force could be responsible for this? We are not sure yet. We now have a good idea of its behaviour.

Chapter 8. The big bang , black holes and the evolution of the universe.

              When the universe began the density of the universe and the curvature of space time would have been infinite. The theory of general relativity predicts that there is a point in the universe where the theory fails.         Such a point is what mathematicians call a ‘singularity.’ When a theory predicts a singularity it is a sign to modify the theory.

Chapter 9 Quantum Gravity.

               Quantum mecanics introduces an element of unpredictability. Einstein objected to this strongly. Thogh he was awarded the Nobel Prize for the contribution to quantum theory.” God does not play dice”.

Chapter 10. Worm holes and time travel.

                "There was a young lady of wight

Who traveled much faster than light

She departed one day

In a relative way

And arrived on the previous night."

According to Feynman time travel into the past. in a way occur on single particles.
The possibility of time travel remains open.
Chapter 11. The Forces of nature and the unification of physics.
In quantum mechanics , the forces are supposed to be carried out by particles.
matter particle, such as an e- emits a force carrying particle. the recoil from this emission changes the velocity of the natter particle.the force carrying particle then collides with another matter particle.
Each force is transmitted by its own type of force carrying particle. If the mass of f particle is high it will be difficult to exchange them over large distances.
1.gravitational force..... particle = 'graviton'
every particle feels this .... weakest of four.....always attractive....exerts over very long distances.
2.electromagnetic force- particle = photon.
interacts with electrons and quarks not with neutrinos.
this 10 40 times stronger than gravity. there is repulsion as well as attraction.
3. weak nuclear force
responsible for radioactivity. ih 1967 Abdus salam and Weinberg proposed theories that unified this interaction with the electromagnetic force.
4.Strong nuclear force .... paticle= gluon
binds protons and neutrons together.
2. Storm in a tea cup-
The physics of everyday life.
By Helen Czerski.
Laws of physics have been explained in a very simple way without using technical terms.
Chapter 1.Popcorn and rockets :- Gas laws
Pop corn bursts due to steam pressure building up inside the grain due to heat. ( For this to occur the seed cover has to be watertight
Sperm whales never breathe from their lungs when they make deep dives
 In 1650 Otto von Guericke performed the ‘Magdeburg sphere’ experiment. His experiment inspired Robert Boyle and Robert Hooke to carry out experiments on gas pressure.
Chapter 2.  What goes up must come down:- Gravity.
How does a seed know gravity for the root to grow down and the shoot to grow up
Inside the seed there are specialized cells called ‘statocytes.’ inside each one there are specialised starch grains that are more dense than the rest of t cell.and they settle towards t bottom.of t cells.protein networks can sense where they are and so the seed and later y plant knows which way is up
Fresh eggs sink in and lie flat in cold water, a week old egg but stand up on the pointy end   , if the egg floats it has been around for some time.

       T blue region of a candle flame =1,400 c. yellow= 1000 c

Chapter 3,:- Small is beautiful

                       Surface tension and viscosity

In the world of small ‘Gravity’ is still present, but other forces start to matter more.  In 1665 Robert Hooke published ‘Micrographia’  ...Here he had not just shown the way to the world of thre the existence of atoms was confirmed.

Much later R Feymabn declared that  ‘ “There’s plenty of room at the bottom”.

      Why does spilled coffee on a table leave a ring pattern?

Evaporation is happening at the edges more than from the middle  of the stain…. Liquid coffee from the middle must flow to the edges  The coffee can’t evaporate.

Why we don’t get a layer of cream on top of milk now?

Fat in milk 1-10 microns. They are less dense than water. Gravity pulls water a bit harder around  than them.  How fast it rises depend on viscosity.  Larger globules rise faster….

Homogenisation is the art of breaking up these fat globules by squeezing them at high pressure through fine tubes.

Foam is not the best stuff for pulling dirt. Foaming agents are now added just to satisfy the consumers

Uses of capillary force

Cotton absorbing water  Water rising in tall trees   Lot of opportunities for microfluidity.

Blood and urine testing with a piece of paper ….known as ‘lab- on a chip’. Paper is cheap easy to get rid of safely.  Can take a photo with a phone, send it to a distant  doctor for diagnosis. Small is beautiful.

Chapter 4. :-A moment in time.  March to equilibrium

Doing the same thing quickly and slowly gives u different results.

In ketchup, viscosity helps t spices sinking down. People prefer a thick sauce. If u try pushing slowly it behaves like a solid.But once u force it to move quickly it behaves like a liquid.

Xanthan gum 0.5% gives this property. It is a long chain of linked sugars.

They get untangled on shaking.and retangle quickly.

Snail slime has a similar property that helps them to cling on to a ceiling. The mucus is shear-thinning.

In 2011 an quake shook the sandy soil so fast that it turned into a liquid. Rapidly shaking sand and water could not support the buildings.

Avg reaction time for a human is ¼ s. a blink is ⅓ second.

Chapter 5 Making Waves,
Ocean waves coming from a particular direction but lashes on an island shore always parallel to the beach.
The source of the tsunami was in the east of Sri :Lanka, but the tides rushed from right round the island.

Chapter 6 Why don't ducks get cold feet.
This is due to the counter current method of blood flow.
Chapter 7 Spoons, spirals and sputnik.
Chapter 8 When opposites attract.
Bees get electrically charged by losing electrons, during flight. (It flaps wings about 200 times a second.) When it flies over a flower pollen gets attracted and sticks to the fur.
Chapter 9 A sense of perspective.