Physics We Can All Understand

By ATS John Skieswanne

The Uncertainty Principle.

In the quantum model, once you reach the subatomic level, nothing is certain anymore. In fact, one of the major pillars of the Quantum Model (QM, for short) is actually named the “Uncertainty Principle”.

When we measure the position of “large” objects, their position doesn’t get much disturbed. This applies for galaxies, for stellar objects, and for small objects such as watches and T-shirts and tennis balls. This even works for most atoms. But one thing Werner Heisenberg discovered in 1927: there is a lower limit to this process. Past a certain point, there is no way to know for sure where a subatomic particle is located anymore. At such a small scale, we can only say these particles have a probable position.
Here’s an analogy to illustrate Heisenberg’s argument:

Imagine an electron (the target particle) as a lonely pin on a very, very dark bowling lane. You can’t see the pin, you can only guess where it is. Since you don’t know yet the position of the pin on the lane, you may think of the pin as being smudged all over the lane as a probability amplitude – meaning it can be nearly everywhere inside this wave-like function of possibilities, but at some places more likely than others:

Heisenberg pointed out that to figure out where the electron (our bowling pin) is, you have to send some kind of signal onto it, like a light or something (you can’t know its position if you don’t detect it in the first place).
Now light rays are made of particles, called photons.
Imagine you have a bowling ball – a glow-in-the-dark bowling ball. This ball represents the photon – the particle of light. Now imagine you throw the bowling ball onto the lane, at the pin somewhere in the dark. Luckily, you hit the pin with the very first shot – and at the point of impact, you see your bowling ball deviate. Now, you know where the pin is, right? – It is located at the point where your bowling ball got deviated.
Think again.
Because of the impact itself, the pin has been kicked back at some other, random direction. Thus although its position may be known at the moment of impact, its momentum (and momentum direction) is not known with certainty anymore.


Thus, Heisenberg concluded that at the subatomic level, no machines can accurately pinpoint the exact position of a particle without compromising its momentum, and vice-versa. That’s basically because the target particles are so small, that any measurements, such as those performed by sending a photon at them, would upset their state (by distributing energy to them).

That is why in the Quantum Model the properties (such as position, momentum, etc) of a particle are represented using probabilities. Since we just don’t know, we assign this probability wave function to a particle. Once you know one property of the particle for certain, then you may say that you “collapsed the particle’s wave function” – this basically means that you’ve eliminated all other possibilities but one (for this specific property) down to zero.

A common mistake, especially in New Age, is to confuse “subatomic measurement” with “human eye”. These are two different kind of “observations”. In physics, “observation” really means “measurement” – not necessarily organic, visual or spiritual, but actually physical.

You can stare in the dark for eons – this will not change the wave functions of the particles there. To collapse the wave function you actually have to send something at it, you have to interfere with it in some way, otherwise it can’t “know” if you’re measuring it or not in the first place. Additionally, Heisenberg’s Uncertainty vanishes astronomically as soon as the target object becomes large enough to sustain measurement without getting kicked to some random direction. So far, galaxies, planets and even humans do not receive that much of a kick from the Reception of One Photon. Accordingly, these larger objects are dominated by very tangible laws (“classical” laws of physics) discovered by Newton and Einstein ages ago.

John Skieswanne


The Special Theory of Relativity (part 2).

We used to think that Light could slow down. It was a natural assumption: if the Earth was to move at 30 kilometres per seconds away from, say, the star Regulus, and if Light normally travels at 299,792.458 kilometres per seconds, then wouldn’t it mean that light from Regulus should arrive slower to us, at (299,792.458 – 30) 299,762.458 kilometres per second?
Albert Michelson decided to put this to the test. In 1887 he devised a light speed detector – the most accurate light speed detector in his time – which got called the “Michelson-Morley Experiment”. But, to his great surprise, the speed of light remained the same – regardless of Earth’s motion. It goes without saying that Michelson was rather perplexed by the constancy of Light’s speed.

Luckily, Albert Einstein was already working on his Special Theory of Relativity. It so happened that his theory explained (and still does) Michelson’s failure.
The truth is, light speed remains the same, no matter the speed of the moving object. Since the speed of light is defined as the time interval it takes for Light to cross a distance interval, then the new moving frame changes the definition of “distance” and “time” so in the end, light ends up traveling the same amount of space-time intervals even when something moves.
Here’s an analogy to explain Einstein’s argument:

Imagine two very powerful light bulbs. One is blue and is placed on a space station some 1,200,000 kilometres from Earth. The other is red and it is placed on Earth. Suddenly, both emit a burst of their powerful light simultaneously at the same time.
Now imagine that you are on a spaceship. I’d personally favour a popular space-ship from a TV series featuring a certain captain Kirk, but any other spaceship will do.
Imagine you are parked just in-between the space station and the Earth. If you don’t move relative to that position, you’ll receive both blue and red light pulses simultaneously:

But what would happen if you decided to move and fly right at the space station, at the speed of, say, 1/2 c (1/2 the speed of light)?
Well, obviously, the space station’s blue light pulse (the one you’re going at) would reach you before the Earth’s red light pulse (from which you’re flying away). The two events won’t be simultaneous anymore. Yet, this means that the two lights will come at you at different speed, right? But Michelson proved that light speed remained the same no matter what.
Einstein had to resolve this paradox.
Einstein speculated that when an object moves, it moves space-time along it – it generates it own space-time intervals frame (its own “Minkowski space”). Thus although the blue light does reach you first, it nevertheless traveled 3 of your moving space-time intervals. And although the red light does reach you last, it also traveled 3 of your space-time intervals. Since one space-time interval is here equal to 299,792.458 km (for space) and 1 second (for time), then, technically, both light rays covered 599584.916 km of warped space and 2 seconds of warped time before reaching you. In other words, they both traveled at exactly the speed of light (relative to you)!


On another note: Einstein also pointed out that you, in the moving ship, won’t notice anything abnormal. Since you’re not moving relative to your own frame’s space-time intervals, then you see your ship as if it was perfectly stationary (that is, if such a thing was possible).

If you were to fire up your thrusters on an asteroid, who would move? You away from the asteroid, or the asteroid away from you? Einstein specifies that it makes no difference. “There are no preferred frame of reference”, he would say. Everything carries its own space-time frame. If two objects have no motion relative to each other, aka they move in the same direction at the same speed, then they share the same space-time frame. If two objects move relative to each other, they no longer share the same space-time frame. Since Einstein’s law concerns object which moves relative to each other, it doesn’t matter who’s making the move.

The relative movement between the two is the focus of Einstein’s Special Relativity. Hence the name.




3 Responses to “Physics We Can All Understand”

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