Series Part 0
Part 02
Series of Physics
The First 3 minutes
The 4% Universe
The Big Bang (Lemaitre), the expansion (Einstein), the WIMP (Lee, Weinberg, Turner)
1927 - 1985
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This part will cover the expansion of the universe, dark matter, and Dark Energy.
I want to start with a substantially relevant quote from a reference book:
"You couldn’t know how the universe began because the evidence was out of reach, just as it had been for Aristotle, Ptolemy, and Copernicus.” [1].
All that we are trying to achieve here is to apply the Aya’a of the Qiran:
قل سيروا في الأرض فانظروا كيف بدأ الخلق" “
We will never know what was before the Big Bang if we accept the model! We have no tools or access to such knowledge. Even the Universe doesn’t carry the print to know. Allah swt has made this completely dark to us. We only see his creation from the point of Planck time (t = 10⁻⁴³ seconds) on! No mathematical equation has a value smaller than this. Math breaks up and forms infinities! سبحان الله العظيم
So, we go back to what we can study and understand.
The introduction of the Big Bang theory was made by Georges Lemaître of Belgium, who proposed the "primeval atom", the universe began from a single dense point (1927), and is considered the father of the Big Bang theory, which we mentioned in the previous chapter of this theory.
The expansion of the Universe:
The expansion of the Universe was confirmed in the 30s of the last centuries, after it was predicted by Einstein in his Special Theory of Relativity, through measurements carried out with the Hubble telescope using what is known as the “Redshift”. Here is what it means:
- Visible light comes in a spectrum of colors — from violet at one end to red at the other. Each color corresponds to a specific wavelength:
- Violet ~380 nm (shortest)
- Blue ~450 nm
- Green ~520 nm
- Yellow ~580 nm
- Red ~700 nm (longest)
Shorter wavelength = higher frequency = more energetic. Longer wavelength = lower frequency = less energetic
The Doppler Effect:
In 1842, a physicist named Christian Doppler discovered that the frequency of the wavelength is related to the distance between an observer and the light source. This was called the Doppler Effect.
To feel the Doppler effect, imagine an ambulance racing toward you:
Siren sounds High-pitched
- → Sound waves compressed
- → Shorter wavelength
When an ambulance races away from you:
Siren sounds low-pitched
- → Sound waves stretched
- → Longer wavelength
The same thing happens with light.
When a light source moves away from you:
Light waves get STRETCHED
- → Wavelength gets LONGER
- → Shifts toward the RED end of the spectrum
- → Called REDSHIFT
When a light source moves toward you:
Light waves get compressed
- → Wavelength gets SHORTER
- → Shifts toward the BLUE end of the spectrum
- → Called BLUESHIFT
Every element in the universe — hydrogen, helium, sodium, calcium — absorbs and emits light at specific, known wavelengths. These are called spectral lines — a unique fingerprint for each element.
Laboratory hydrogen spectral line: 656 nm (red)
Distant galaxy hydrogen spectral line: 720 nm
- → Shifted to a longer wavelength
- → Galaxy is moving AWAY from us
- → Redshifted
The amount of Shift tells exactly how fast the object is moving away:
z = (observed wavelength − original wavelength) / original wavelength
Where z is called the redshift parameter.
Z = 0 Not moving relative to us
Z = 0.1 Moving away at 10% speed of light
z = 1 Moving away — wavelength doubled
z = 7 Very distant early universe galaxy
z = 1089 The CMB[2] — from recombination 380,000 years after the Big Bang
Hubble's Great Discovery (1929)
Edwin Hubble measured the redshift of dozens of galaxies and found something stunning:
Every galaxy is redshifted, and every single one is moving away from us.
And more importantly:
The further the galaxy, the greater the redshift and the faster it is receding.
This relationship — known as Hubble's Law:
v = H₀ · d
"Velocity equals Hubble constant times distance."[3]
In plain English: A galaxy twice as far away recedes twice as fast. A galaxy ten times further recedes ten times faster.
The galaxies are not moving through space like rockets. Rather:
Space itself is expanding and carrying the galaxies with it.
The analogy: imagine dots drawn on a balloon. As you inflate the balloon:
Every dot moves away from every other dot
No dot is at the center
No dot is moving across the balloon surface
The rubber itself is expanding
- → Carrying all dots apart
This is exactly what the universe is doing. The redshift is not a Doppler effect in the traditional sense; it is the stretching of space itself, stretching the wavelength of light as it travels through expanding space.
ما أصدق كتاب الله تعالى "وَالسَّمَاءَ بَنَيْنَاهَا بِأَيْدٍ وَإِنَّا لَمُوسِعُونَ" الذاريات 47.
Gravity and Gravitational Effect:
We have mentioned before that Gravity was not explained, even in Newton’s theory. However, it was always dealt with as a “Force”, a very weak force, the weakest force of the four that were a result of the Big Bang explosion. Until Einstein’s Special Relativity theory, in which he showed in his famous equation that Gravity is a geometric property rather than a force, a curvature of spacetime, as we have discussed in the previous paragraphs. He showed that it is simply the action of different masses as they bend the huge fabric of spacetime.
The Einstein field equations, introduced in 1916 and forming the core of Einstein's general theory of relativity, specify how the geometry of space and time is influenced by the matter and radiation present.
Richard Panek wrote, “General relativity had been around for nearly half a century; Einstein had arrived at the equations in late 1915. Whereas Newton imagined gravity as a force that acts across space, Einstein’s equations cast gravity as a property that belongs to space. In Newton’s physics, space was passive, a vessel for a mysterious force between masses. In Einstein’s physics, space was active, collaborating with matter to produce what we perceive as gravity’s effects. The Princeton physicist John Archibald Wheeler offered possibly the pithiest description of this co-dependence: “Matter tells space how to curve. Space tells matter how to move.”[4]
So, it is now accepted that gravity is a geometric property of spacetime rather than a force. It is the deflection that masses create in the time-space fabric of the universe when they are in the presence of others.
The analogy begins by considering space-time as a rubber sheet that can be deformed. In any region distant from massive cosmic objects such as stars, space-time is uncurved, that is, the rubber sheet is flat. If one were to probe space-time in that region by sending out a ray of light or a test body, both the ray and the body would travel in perfectly straight lines, like a child’s marble rolling across a rubber sheet.
*Figure 1. 
However, the presence of a massive body curves space-time, as if a bowling ball were placed on a rubber sheet, creating a cuplike depression. In the analogy, a marble placed near a depression rolls down the slope toward the bowling ball as if pulled by a force. In addition, if the marble is given a sideways push, it will describe an orbit around the bowling ball, as if a steady pull toward the ball is swinging the marble into a closed path”.[5]
Dark Matter:
The story of the discovery of Black Matter and Energy relates directly to the progress in understanding the gravitational nature on both small and colossal scales, from lifting a ball off the ground to the elliptic rotation of galaxy clusters, and to the findings of the Redshift phenomenon, as mentioned before.
A significant contributor to this area of research was Vera Rubin of Pennsylvania, USA (1928-2016), who was inspired by Fritz Zwicky's (1933) research. She began her research as a physicist when she noticed a discrepancy in the rotation speeds of some solar systems in the Milky Way, and, specifically, in the Andromeda galaxy.[6]. What interested her was the continuation of the concept of homogeneity and isotropy across the universe! After 25 years, she noted that “Once again Rubin found that galaxies exhibited not just the recessional motion of the expansion but peculiar motions.” Galaxies were supposed to be slower as they get farther from the edges of the visible universe, or, in her case, from the far edge of the galaxy, Andromeda, as the gravitational force gets weaker for the lower mass, they become subjected to. But they were not! This tells her that something is “missing”, or rather, something is present.
She was able to study the phenomenon known as a “Supernova,” the death/explosion of a very distant star, and measure it using its luminosity and redshift.
Thirty years later, exploring the idea of the universe's rotation, she conducted a study of the rotational velocities of 21 galaxies at the edge of the visible universe and compared them with what they should be based on calculated mass, velocity, distance, rotation, and gravitational effects.