Quantum Mechanics demystified, a try
Have you ever pondered how do they deduce what’s the distance to some star or galaxy is. They say it can be told from redshift of the light from that source. What’s the redshift method based on, I wonder.
Basic assumption is that a star, galaxy or any cosmological object is spreading frequencies of electromagnetic radiation in wide continuous spectrum. Radiation is caused by heat produced in fusion reactions, fusion being mostly that of hydrogen turning to helium.
Key for understanding redshift’s logic is that certain frequencies are absorbed from above radiation e.g. by hydrogen and helium atoms on the way. Frequencies are ones that make electrons jump to higher energy levels on those atoms. These frequencies have been determined in lab experiments. When this radiation is targeted to a prism, the spectrum produced has darker lines on spots for those missing frequencies. These are called absorption lines.
But now, when the radiation is traveling towards us, the universe is spreading out at the same time. This makes the wave length appear longer to us when perceived. Speed of radiation remains constant c, but as we travel further away from the source all the time, peaks and troughs of radiation get further away. I.e. wave length increases, turning the radiation to shift a bit to the red side of the spectrum. Originally blue light turns first green and then further to other colours towards red.
If the universe would spread in a steady speed, the amount of red shift would always be the same. Just as the sound of ambulance’s siren moving away from you remains the same.
However, if the ambulance would be accelerating, the sound would become lower and lower, as the wave length increases.
Exactly the same happens with our universe spreading in accelerating speed. Radiation frequency from far away cosmological objects gets lower the longer the radiation has been on the way.
Thus, by routing star’s radiation through prism and noting the frequencies of absorption lines, we can see amount of redshift. By knowing the acceleration, we then can calculate how long the radiation has been on the way together with the distance of the object.
How then acceleration of the spreading of the universe is determined?
Take a note of the absorption line frequencies at one time. Then do it again after some time, say a year or so. You would see the absorption lines have red shifted more. Acceleration can the be calculated based on the frequency change, delta time and speed of light.