The Sirens Song - Doppler Effect - Redshift and Blueshift.

---

Ride the Wave(s),

Previously I touched on the expansion of the universe and thought it would be a good idea to expand on the underlying mechanics that allowed us to reach that conclusion.

Red-shift and blue-shift is a phenomenon where light changes as objects in space move closer or farther away from us. For example when a police car drives past a stationary observer and the siren appears to increase and decrease in pitch. This is the Doppler Effect and can be applied to light as well.

Visible light is a spectrum of colors and when an object moves away from us the light is shifted to the red end of the spectrum. If an object moves closer the light moves to the blue end of the spectrum as its wavelengths get shorter and more compacted.

This effect was first theorized by Christian Andreas Doppler and is called the Doppler effect. Since light is a wavelength this means the wavelengths can stretch or squish together depending on the position of objects relative to one another. However we don't notice it during our daily lives because light travels much faster than the speed of sound.

Proof of Expansion,

American astronomer Edwin Hubble was the first to describe the red-shift phenomenon and tie it to an expanding universe. His observations, showed that nearly all galaxies he observed are moving away.

"This phenomenon was observed as a red-shift of a galaxy's spectrum. This red-shift appeared to be larger for faint, presumably further, galaxies. Hence, the farther a galaxy, the faster it is receding from Earth." - Quote from NASA.

The galaxies are moving away from Earth because the fabric of space itself is expanding. While galaxies themselves are on the move, with some moving closer together and some further apart. There is an overall phenomenon of red-shift happening as the universe gets bigger.

Not just Light,

The terms red-shift and blue-shift can be applied to any part of the electromagnetic spectrum, including Infrared, Radio waves, X-rays and Gamma rays.

If radio waves are pushed into the ultraviolet part of the spectrum they are said to be red-shifted, as in shifted toward the lower frequencies.

The red-shift of an object is measured by examining the absorption or emission lines in its spectrum. These lines are unique for each element and always have the same spacing.

When an object in space moves toward or away from us, the lines can be found at different wavelengths than where they would be if the object were not moving.

Red-shift is the change in the wavelength of the light compared against the wavelength that the light would have if the source was not moving.

Different ways to Shift,

At least three types of red-shift occur in the universe. From the universe's expansion. From the movement of galaxies relative to one other and from gravitational red-shift. Which happens when light is shifted due to the sheer bulk of matter inside of a galaxy.

This latter red-shift was the most difficult to track down of the three. however in 2011 scientists were able to identify it on a universal scale.

Astronomers did an analysis of a large data-set known as the Sloan Digital Sky Survey, and found that gravitational red-shift does happen, perfectly in line with Einstein's theory of general relativity.

The first detection of gravitational red-shift came after scientists detected it occurring in gamma-ray light emanating from an Earth-based lab.

We talked a lot about red-shift in this post, but the inverse is true for blue-shift. It's just the phenomenon of waves being compressed together increasing the perceived wavelength by us relative to the original wave.

While not being as common in the galactic playground it is definitely something to 'watch out for' as it represents an object accelerating as it approaches us.

Perhaps an alien visitor accelerating hard at the beginning of a very long journey?

Thanks for taking the time to read through this dearest readers. I hope you have a fantastic day, much love. <3

Sourcing and further information here and here

---