Temat 13: Albert Einstein

Albert Einstein (b. 1879 Ulm, d. 1955 Princeton) was one of the greatest physicists ever. (The ‘s’ in his name is pronounced ‘sh’.)
In 1905, he published three important papers: one about Brownian motion, one about special relativity and one about the idea of light quanta.
The first paper showed definitely that matter is made of molecules and atoms;
the second showed the invariance of the speed of light;
and the third paper was one of the starting points of quantum theory.
Each paper was worth a Nobel Prize, but he was awarded the prize only for the last one.
Also in 1905, he proved the famous formula E₀ = mc² (published in early 1906), after a few others also had proposed it.
Although Einstein was one of the founders of quantumtheory, he later turned against it. His famous discussions with his friend Niels Bohr nevertheless helped to clarify quantum theory in its most counter-intuitive aspects.
Later, he explained the Einstein–de Haas effect which proves that magnetism is due to motion inside materials. After many other discoveries, in 1915 and 1916 Einstein published his highest achievement: the general theory of relativity, one of the most beautiful and remarkable works of science. In the remaining forty years of his life, he searched for the unified theory of motion, without success.
Being Jewish and famous, Einstein was a favourite target of attacks and discrimination by theNational Socialist movement; therefore, in 1933 he emigrated from Germany to the USA; since that time, he stopped contact with Germans, except for a few friends, among them Max Planck. Until his death, Einstein kept his Swiss passport in his bedroom. He was not only a great physicist, but also a great thinker; his collection of thoughts about topics outside physics are well worth reading. But his family life was disastrous, and he made each of his family members unhappy.
Anyone interested in emulating Einstein should know first of all that he published many papers.* He was both ambitious and hard-working.
Moreover, many of his papers werewrong; he would then correct themin subsequent papers, and then do so again.
This happened so frequently that hemade fun of himself about it. Einstein indeed realized the well-known definition of a genius as a person who makes the largest possible number of mistakes in the shortest possible time.

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* All his papers and letters are now freely available online, at einsteinpapers.press.princeton.edu .


Check your knowledge: Special relativity
1. Which of the following has not been observed to change due to motion?
- Time
- Length
- Speed of light in a vacuum
2. An astronaut takes a long space journey at close to light speed. The astronaut's twin sister remained on Earth. On a return to Earth, what is the astronaut's age compared to her earthbound twin?
- Older
- The same
- Younger
3. As it approaches the speed of light, what will happen to the length of a spacecraft as observed by a passenger inside? - It will increase
- It will remain constant
- It will decrease
4. A spacecraft of length 780 meters is travelling at a constant speed of 0,95 c . The spacecraft travels at this speed for 10 years, as measured by a clock on the Earth.
Calculate the time elapsed, in years, as measured by a clock in the spacecraft.
- 2.23 years
- 3.12 years
- 32.0 years
5. A spacecraft of length 780 meters is travelling at a constant speed of 0,95 c. The spacecraft travels at this speed for 10 years, as measured by a clock on the Earth. If the spacecraft passes Earth at this speed what length would an observer on Earth measure for the spacecraft?
- 174 m
- 244 m
- 2500 m
6. Imagine a train travelling at 100 m/s with a passenger who throws a ball ahead of the train at 5 m/s . What is the resultant velocity of the ball?
- 5 m/s
- 100 m/s
- 105 m/s
7. Imagine a train is travelling at 2,9 x 108 m/s . A passenger shines a torch from the front of the train. What speed does the passenger see the light from the torch move at?
- 0,1 x 108 m/s
- 3 x 108 m/s
- 5,9 x 108 m/s
8. Imagine a train is travelling at 2,9 x 108 m/s . A passenger shines a torch from the front of the train. A stationary observer on the train platform measures the speed of light from the torch. How fast does the light appear to move according to the stationary observer?
- 0,1 x 108 m/s
- 3 x 108 m/s
- 5,9 x 108 m/s