Chapter 1: Basics of Red Shift

Chapter 1: Basics of Red-Shift

Edwin Hubble is one of the most celebrated astronomers of all time due to two extremely influential discoveries he made. The first was the existence of other galaxies in the universe. Before Hubble’s discovery of other galaxies our universe had appeared a far smaller place with the most distant objects in the universe thought to be in our galaxy. With the discovery of other galaxies we learned that there are far more stars in the universe and vastly more space than we had ever imagined.

One interesting fact about distant galaxies is that all distant galaxies are red-shifted. The farther away a galaxy is, the more red-shifted it is. Only one galaxy is blue-shifted and that is the Andromeda Galaxy which is on a collision course with our own Milky Way Galaxy.

Observation: All Distant Galaxies in the Universe are Red-Shifted (URS)

In this paper an Observation is a fact, observed by science, which must be explained. The italicized abbreviations at the end of observations will be used for symbolic logic later in the paper.

Definition: Red-Shift (RS)

In this paper a Definition describes a concept with all the characteristics needed for it to be used logically throughout the paper. This is important because the logic in this paper requires a clear and unambiguous understanding of each concept. Additionally, intelligent readers without a mathematical background may understand the concepts described within this paper better than professional theoretical physicists who have their understanding in the concepts of theoretical physics embedded in a foundation of mathematics. Thus, it may be the case that friends of professional theoretical physicists may be required to explain the concepts within this paper to their friends which is why intelligent laypeople are the primary target audience of this paper.

The italicized abbreviations at the ends of definitions will be used for symbolic logic later in the paper.

Red-shift happens when the measured (observed) wavelength of a wave is longer than the wavelength of the wave when it was emitted. Inversely, a blue-shift happens when the measured wavelength of a wave is shorter than it was at the time it was emitted. Wavelength shifts can happen to all waves including sound and light.

[To Be Continued after Wave is Defined.]

Definition: Wave (W)

            A wave consists of energy passing through a medium. The speed at which a wave moves is determined by the type of wave and the medium it is traveling through. The primary determining factor is the medium. For example, the speed of sound through air is different than the speed of sound through liquid. Wave speed is one of the primary characteristics of a wave.

            The second primary characteristic of a wave is its wavelength. A wave is characterized by regions of high energy and low energy and the distance between the peaks (highest energy) and troughs (lowest energy) within that wave determine its wavelength. For example, a high-pitched sound has a short wavelength meaning that if you took a picture of the air compressions of a volume of air as a high-pitched sound wave was passing through that wave, you would see that the points of highest compression (peaks) would be close together compared to a picture of a lower-pitched wave.

             The observed wavelength/frequency of any wave gives us its characteristic feature. The wavelength of sound gives us its pitch with pitch rising as the wavelength decreases.

            Frequency is another term associated with waves and is effectively the inverse of wavelength. When a wave is observed or measured, it vibrates an object and the number of vibrations per second (or other unit of time) determine its observed characteristic. For example, with sounds our ears to not measure the wavelength of a sound wave. Rather, a sound wave vibrates our eardrum some number of times per second and that frequency of vibration is translated into pitch, the characteristic feature of sound.

            Observation of a wave frequency is a determined by the speed of the wave and the wavelength of the wave.

Math  

Frequency (f) is the observed (measured) number of peaks per second (p/s).

Wavelength (w) is the observed distance between 2 wave peaks (p/d).

Wave Speed (s) is the distance a peak moves in a second (d/s).

f = w*s

The frequency (number of peaks per second) is equal to the wavelength (distance between peaks) times the wave speed (distance the peaks travel every second).

            A “note” is the music term for some frequency of sound wave as observed by the ear. The more often a peak is observed, the higher the frequency. This means that a short sound wave moving through a medium that makes it go slow can sound the same as a long wavelength sound wave in a medium that makes it go fast.

            All that is measured by the ear is the frequency.

            Light is another type of wave and it is the one that most important to astronomy. It too has wavelength and frequency and the speed of light depends on the density of the object it is passing through. For example, light travels fastest in a vacuum (complete absence of matter) and slower in denser substances like light and glass.

            Light comes in packets of electro-magnetic energy called photons and photons can come in many different wavelengths as described by the electro-magnetic spectrum. The shortest wavelength photons are gamma rays. As the wavelengths of photons get higher they are categorized as X-Rays, Ultra Violate (UV) Rays, Visible Light, Infra-Red (IR), Microwave, and Radio Waves.

            The biological engineering in human eyes allow us to see visible light because the cones and rods within our eyes are agitated by certain wavelengths of photons and send neuron impulses to our brains in response to these agitations.

            The rainbow is an electro-magnetic spectrum of visible light. We can see from red to violate on a rainbow due to the engineering of our eyes but if we could see longer or shorter wavelengths then a rainbow might look much different.

            Red photons are the longest photons humans can see which is why it is at one end of the rainbow. Violate photons are the shortest wavelength we can see which is why it is at the other end of the rainbow. Notice that Infra-Red (IR) is the set of wavelengths that begins at the wavelength a little longer than the red we can see and Ultra-Violate (UV) set of wavelengths begins at the wavelength a little shorter than those we can see.

            All photons are made of the same “stuff” (oscillating electro-magnetic fields) and the main thing that makes visible light special to humans is the biological engineering of our eyeballs.

Definition: Emission Wavelength (EW)

            Each wave has a moment of emission. At this moment of emission the emission process determines the wavelength of the wave.

            For example, if you pluck a guitar string or strike a piano key the vibrating string creates a vibration in the air that corresponds to a “note” of some frequency. Once emitted, that compression wave with its frequency will travel through the air for some period of time before reaching the ear of someone listening.

            The characteristics of the medium influence the wavelength of the wave. For example, a musician will need to tune a guitar differently for environments of different humidity or elevation because the speed of sound changes based on the conditions of the air. A note might sound the same in different environments but the compression wave in the air will be moving faster or slower depending on the density of the air so the emission wavelength will have to be different in the different environments in order for the hearer to hear the same note due the speed of the wave. 

            The Wave Emission involves only that moment at which the wave was emitted. Each wave has an Emission Wavelength (EW).

Definition: Observed Frequency (OF)

            When a wave is observed (or measured) only its frequency can be measured. The wave’s energy is absorbed by the measuring device and the frequency of the wave is the only piece of information that the observer can directly measure. The wavelength of the wave can be calculated based on the speed of the wave and the frequency of the wave, but the Emission Wavelength (EW) of the wave is impossible to directly measure.

Definition: Red-Shift (RS) (Continued)

            Sometimes the frequency of a wave is measured and the Observed Frequency (OF) of that wave does not match the Emission Wavelength (EW) of the wave.

            It is possible for the circumstances at the moment of emission to modify the wave in a way that the observer measures an OF different from the EW.

            It is also possible for the circumstances at the moment of observation to cause the observer to measure an OF different from the EW.

            Finally, the circumstances of the medium of the wave can modify the wavelength of the wave-in-motion during the Travel Time of the wave.

            Whenever the OF does not match the EW, then a frequency shift has occurred.

            If the OF is less that the EW, that is called “Blue Shift” because if a photon is emitted (EW) in the “yellow” wavelength but appears (is observed to be) “Blue” that means that something has happened to shift the observed frequency (OF) into a higher frequency (shorter calculated wavelength) than it was at the time of emission (EW).

Definition of Red-Shift (RS)

            A Red-Shift happens when the Observed Frequency (OF) of a wave corresponds to a wavelength longer than the Emission Wavelength (EW). In the case of Red-Shift something has happened to shift the observed frequency (OF) into a lower frequency (longer calculated wavelength) than it was at the time of emission (EW).

           

Galactic Red-Shift (GRS) (Continued)

            The observation that all distant galaxies are red-shifted is fairly easy to make due the existence of emission and absorption lines in the electro-magnetic spectrum.

Emission and Absorption Lines

Each type of atom (element) has a fingerprint in the electro-magnetic spectrum caused by the configuration of the orbits of its electrons around the atomic nucleus. Each type of atom, when exposed to the entire electro-magnetic spectrum, will absorb only photons of specific wavelengths. For example, if you shine white light at neon gas the gas will absorb certain wavelengths of light leaving the rest to pass through. If you use a prism to separate the white light into a continuum of wavelengths (a rainbow) then you can find the dark lines in the spectrum where the neon has absorbed that wavelength of light.

Similarly, if you send an electric current through neon gas it will emit photons. The wavelengths of those photons will be the same as the absorption lines. The emission lines and the absorption lines are the same because each element both absorbs and emits light at specific frequencies.

            This is a highly simplified explanation for absorption and emission lines, but the important thing to understand is that astronomers can easily figure out some of the elements that stars and other luminous objects have in their outer layers using a characteristic set of lines on the electro-magnetic spectrum. The absorption and emission lines of each element have been extensively tested in laboratories and the Emission Wavelength (EW) of each element is known.

            Furthermore, astronomers can rather easily figure out how much the light from a distant object is red-shifted by comparing the known EW to the Observed Frequency (OF) and calculating the difference.

            Astronomers knew that all distant galaxies were red-shifted even before they knew galaxies existed due to the fact that Emission and Absorption lines are so easy to use to calculate red-shift. The fact of Galactic Red Shift (GRS) was never in doubt. In the case of all distant galaxies and most nearby galaxies, the OF of the lines of any element are longer than the known EW of that element meaning that the light emissions from all distant galaxies are red-shifted.

The Cause of Galactic Red Shift (GRS)

            If all distant galaxies are red-shifted (and they are), that means that something has happened at some point to make EW =/= OF. Red-shift is always caused by something. It is the task of Science to determine the cause of the red-shift.

By far the most common explanation for red-shift in astronomy is the Doppler Effect but that explanation came with an undesirable set of side effects including the destruction of the Copernican Principle. These concepts will be discussed in Chapter 2: The Doppler Universe.

 

Logic

1.      GRS

2.      If GRS then there must exist an Explanation for GRS (EGRS)

3.      EGRS