Why Doesn't The North Star Move in the Sky?

Have you ever wondered why the so called North Star (sometimes called Pole Star) doesn't move in the sky? Well actually this is one of the most often asked questions in astronomy.

The answer actually is very simple. The so called North Star does not move as it is above the North Pole and the axis of Earth's rotation. Thus the rotation of our planet causes the movement of the stars in the sky except for the North Star.

The interesting thing is that stars also move a little, also the axis of rotation of planet Earth also shifts slowly. Thus the role of the "North Star" changes among stars throughout time.

The picture shows star movement in the sky:

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So Was Einstein Really an Atheist?

I've seen both theists and atheists using Einstein's believe or disbelief in god in their arguments. So was Einstein an atheist or a theist himself?


The answer to this question could be found in Einstein's books and interviews. In the book "Albert Einstein, The Human Side" by Helen Dukas and Banesh Hoffman, he denied believing in personal god: "It was, of course, a lie what you read about my religious convictions, a lie which is being systematically repeated. I do not believe in a personal God and I have never denied this but have expressed it clearly."

However, Einstein wasn't an atheist either, as he also said: "I believe in Spinoza's God who reveals himself in the orderly harmony of what exists, not in a God who concerns himself with fates and actions of human beings."

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So it seems that Einstein was somewhere in between atheism and theism. Perhaps his views are best describe as pantheism. This is confirmed by another great quote from a book by G. S. Viereck called “Glimpses of the Great”: "I'm not an atheist and I don't think I can call myself a pantheist. We are in the position of a little child entering a huge library filled with books in many languages. The child knows someone must have written those books. It does not know how. It does not understand the languages in which they are written. The child dimly suspects a mysterious order in the arrangements of the books, but doesn't know what it is. That, it seems to me, is the attitude of even the most intelligent human being toward God."

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So Can Electrons be at Two Places at Once?

One of the strangest things that you can hear about quantum mechanics is that microscopic particles in some instances can be in more than one place at a time. But how can this be true?

To understand this let's look at the most important experiment in quantum mechanics - the double slit experiment.  The idea of this experiment is simple. You send particles and waves through a double-slit device and observe the results on the screen. Naturally waves and particles, which are not microscopic behave differently. However, if you send a bunch of microscopic particles, like electrons through the double-slit device you get a very surprising result - electrons behave like waves. Even if you send them one at a time, they still create an interference pattern, which is typical for waves, which,of course, pass both slits at a time.

The result of the double-slit experiment using simple particles:

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One of the explanations for this is that electrons somehow exist in two places at a time, that is the same electron passes both slits at the same time. Of course there are scientists who don't believe in this idea. But guess what, you can't check which slit the electron passes, as if you  try to detect it, the interference pattern on the screen disappears, that is the electron then simply passes through one of this slits.

The result of the double-slit experiment using microscopic particles:

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In quantum mechanics, the electron is said to be in a superposition, that is it is at many places at the same time and until you observe the electron, you can't tell where it is exactly. However, this is just the mathematical way of explaining what we can observe experimentally. Nobody really knows in the electron actually is at more than one place at the same time.

Naturally scientists are wondering if it is possible to put a non-microscopic object in a superposition. One of the most ambitions experiments by scientists at the Max Planck institute in Germany, will try to put a glass sphere, which is 40 nanometres in diameter, into a superposition. By using a sensitive laser to "bounce" photons of the sphere, they will try to put it in a quantum superposition, that is it will be in more than place at once. If the experiment is successful it will be the most sensitive test of quantum theory yet.

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So What is This Quantum Entanglement ?

These days we can constantly hear term "quantum entanglement". But what really is quantum entanglement? 

Stanford Encyclopaedia of Philosophy gives the following definition: "Quantum entanglement is a physical resource, like energy, associated with the peculiar nonclassical correlations that are possible between separated quantum systems. Entanglement can be measured, transformed, and purified."

In human language quantum entanglement means an inescapable relationship between quantum systems, such that if one part of the system is measured for some quantity (for example spin or polarization), other part instantaneously changes to give the same result.  

Another example of QE:

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Perhaps the best example of quantum entanglement would be the original mind experiment by Albert Einstein, which introduced quantum entanglement. Let's imagine two photons were entangled and then shot off in different directions, each traveling at the speed of light, and you were to observe and measure the spin of one of the photons. Would the other photon “know” instantaneously and change its spin accordingly? Einstein argued that it wouldn't happen, as it would violate special theory of relativity, as it would be a form of faster-than-light communication.

Back in the early 1980s science became advanced enough to test the famous Einstein's thought experiment. French physicist Alain Aspect conducted a series of experiments which tested the nature of entangled photon pairs and how they might share information. What he found was amazing! In fact, the measurement of one photon did affect the state of its entangled partner, instantaneously!  

Today scientists keep on experimenting with quantum entanglement. In May of 2010, Chinese scientists successfully achieved quantum teleportation of information over a distance of 10 miles. In January of 2011, physicists S. Jay Olson and Timothy Ralph of Australia’s University of Queensland produced the mathematics to support the quantum teleportation of information through time, from the past to the future.

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So How do We Know that Earth Really Rotates?

Everyone knows that Earth rotates around its axis. But have you ever wondered is there some kind of simple proof of this? The answer is yes. The famous experiment performed by Jean Foucault proved the rotation of Earth. But let's start at the beginning.

There were ideas that the Earth might be rotating around its axis since the days of Nicolaus Copernicus (1473 - 1543). However, even though it was a rational idea, backed up by great arguments in the works of Copernicus, it wasn’t experimentally proven. Thus many people in the middle ages and later epochs weren’t aware of the fact that our planet is rotating around its axis. After all, it’s really hard to believe such a thing, as we can’t feel the Earth’s rotation.

Foucalt's Pendulum in Paris:

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It was Jean Foucault (1819 - 1868) a brilliant French physicist, who finally proved Earth’s rotation experimentally, more than 300 years after the works of Copernicus. Foucault built a 28 kg brass-coated lead bob with a 67 meter long wire from the dome of the Panthéon, Paris, which basically worked as a huge pendulum. The idea of the experiment is very simple – as the pendulum swings, it’s clear that Earth rotates, due to the movement of the ground below the pendulum (which, to us looks like the movement of the plane of the pendulum, as we rotate with together with Earth).

This simple, yet very hard to construct, experiment, finally proved that Earth really rotates. Furthermore, it proved the rotation of our planet in a very simple way, so that even simple people, who knew nothing about science, could easily be convinced. That is why this experiment is one of the most important experiments throughout history.


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