Question

Discussion Question 1:

Discuss the differences between the Einstein’s Theory of Relativity and Classical Physics Theory (i.e. Galileo and Newton, etc.)

Discussion Question 2:

Discuss the wave-particle duality of light and its implications. What are possible industrial applications?

Answer 1

(1.)

Both Albert Einstein and Sir Issac Newton are regarded as the forefathers of physics, but both held different theories that are fundamentally different from the other. So in the grand scheme of things.. who was more correct… Einstein or Newton.

Here, we battle it out, but ultimately, the choice is up to you!

So let’s start with Newton! In the world of Newtonian physics, everything looks the same to everyone else in the universe, irrespective of your location and speed. I don’t know about the rest of you, but this seems like a very logical concept, probably because this is how we all view every day life. When I used to play cricket, I had no doubt that my view of the cricket ball hurtling through the air looked the same as someone driving down the road watching the ball (points of view taken into consideration of course). What I’m getting at here is that they didn’t see the ball stretching, moving slowly, and blue shifting.

Really then, the world in Newtonian physics makes sense to us in every day life. I know if I was to tell a group of 11 year old school children that a 1 meter ruler actually appear to be a different length when I’m holding it versus when I’m running with it, they’re likely to think I’m kidding (or crazy). Why? Because we can’t show it. If I did that little experiment with the students, it would still look exactly the same size. And considering that it’s only something like .000000000000000088.. meters longer to the outside observer, I can’t blame anyone for not believing me. Even while traveling on an aeroplane it would only be .00000000000029 meters longer! The point I’m making here is that Newton making the assumption that the universe is exactly the same for everyone else, irrespective of location or speed, was a completely logical assumption. So much so that suggesting anything more at the time would have been completely dismissed–they would have thought he was crazy.

This is where Einstein enters the picture… at the right place, but most importantly, at the right time. There were many scientists with many ideas at the time, incomplete ideas. Einstein managed to unify many different theories into several papers, five of which were published in the same year. This is not to take away from his brilliance, it’s just the nature of science. Einstein managed to combine many different ideas (that were not his own) with an idea of his own and, in so doing, completely change the world.

This is no small task.

A good example of this is the Theories of Relativity and the Lorentz Transformation. Although, in many cases, Einstein gets credit for this, it was first published by Joseph Larmor in 1897, proposed by Hendrik Lorentz in 1895, and eventually modified by Henri Poincare in 1905 but accredited to Lorentz by Poincare. But although Einstein may not have come up with the equation, he did tie it all together in his Special Relativity paper.

Unlike in a Newtonian world, the universe is not quite a constant, for the most part anyway. Taking a look at the Lorentz Transformation using time as our variable:

t’=t/sqrt(1-((v^2)/(c^2)))

In this equation we see that Time and Velocity are variables because neither of them have a constant physical value, like the speed of light “c”. Here we can see that the speed of light MUST be a constant in the universe. This agrees with Newtonian physics, the speed of light being a constant, with time and length being different, this bit obviously doesn’t agree with Newton.

So in the end in the battle between Newton and Einstein, who is right? In every day life, they both are. The speeds at which life goes by are so slow that it has only been in recent history that we have been able to detect the differences. Newton viewed space-time as being flat, unchanging and very boring, but that is not at all the case in Einstein’s world. To Einstein, space-time is very dynamic, changing depending gravity and velocity.

"Galilean relativity" is a principle in physics - that any experiment conducted within a closed box travelling at a constant speed must yield the same results irrespective of the speed it is travelling. There is no special frame of reference which is at rest, as motion is relative.

This was of massive importance at the time, because it explained why experiments on earth yield the same results as if the earth was stationary, even if the earth is whizzing around the Sun. Without this principle, the heliocentric universe model doesn't work.

Einsteinian relativity (special relativity) adheres to this principle. Indeed it was one of the two "assumptions" that Einstein made to develop SR, the other being the constancy of light speed in all inertial frames.

Galilean relativity makes no statement directly concerning time. It does indirectly, because experiments can concern time, and the results should always be the same in every inertial frame. SR shows that if you also assume the constancy of light speed, then you have to treat time in a particular manner when converting results between different reference frames, but this is a long way downstream (about 400 years) of Galileo's principle of relativity.

(2.)

Wave-particle duality, possession by physical entities (such as light and electrons) of both wavelike and particle-like characteristics. On the basis of experimental evidence, German physicist Albert Einstein first showed (1905) that light, which had been considered a form of electromagnetic waves, must also be thought of as particle-like, localized in packets of discrete energy. The observations of the Compton effect(1922) by American physicist Arthur Holly Compton could be explained only if light had a wave-particle duality. French physicist Louis de Broglie proposed (1924) that electrons and other discrete bits of matter, which until then had been conceived only as material particles, also have wave properties such as wavelength and frequency. Later (1927) the wave nature of electrons was experimentally established by American physicists Clinton Davissonand Lester Germer and independently by English physicist George Paget Thomson. An understanding of the complementary relation between the wave aspects and the particle aspects of the same phenomenon was announced by Danish physicist Niels Bohr in 1928 (seecomplementarity principle).

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Although it is difficult to draw a line separating wave–particle duality from the rest of quantum mechanics, it is nevertheless possible to list some applications of this basic idea.

• Wave–particle duality is exploited in electron microscopy, where the small wavelengths associated with the electron can be used to view objects much smaller than what is visible using visible light.
• Similarly, neutron diffraction uses neutrons with a wavelength of about 0.1 nm, the typical spacing of atoms in a solid, to determine the structure of solids.
• Photos are now able to show this dual nature, which may lead to new ways of examining and recording this behaviour.