The Universe's First Light: Cosmic Microwave Background Radiation

If a light source moves away from an observer, then the light waves are stretched; if light waves stretch, then their wavelength increases toward the red end of the spectrum; if we observe this increase (Red Shift) in distant galaxies, then those galaxies must be moving away from us.

If the expansion of the universe is uniform, then more space is created between distant objects than nearby ones; if more space is created per unit of time, then the recession speed must be higher; if observations confirm this linear relationship, then Hubble's Law is correct.

If the universe is currently expanding, then it must have been smaller in the past; if we trace this expansion back to the beginning, then the universe originated from a single point of infinite density; if the event was the start of space and time rather than an explosion in space, then it is defined as a rapid expansion.

If a scientist identified Cepheid variables in distant nebulae to calculate distance and matched them with redshift data, then he proved galaxies are moving away; if Edwin Hubble is the astronomer credited with these 1929 findings, then his name completes the statement.

If the Doppler Effect applies to light, then the direction of motion affects wavelength; if motion away stretches waves (Red Shift), then motion toward the observer compresses waves; if compressed waves have shorter wavelengths associated with blue light, then the galaxy is moving toward us.

If the early universe was extremely hot and dense, then it would emit high-energy radiation; if the universe expanded and cooled, then that radiation would stretch into longer wavelengths; if we detect a uniform 2.7K glow in the microwave range across the sky, then it represents the cooled "afterglow" of the Big Bang.

If the universe is expanding, then the space between galaxies is stretching; if the space itself stretches, then the light waves traveling through that space are stretched as well (Cosmological Redshift); if this differs from "peculiar motion" through space, then the statement that it is just like a car on a road is false.

If the Big Bang occurred, then we should see expansion (Redshift); if the early universe was hot, then we should see a cooled glow (CMB); if fusion occurred in the first few minutes, then light elements should be prevalent; since water on Mars and tectonic plates relate to planetary evolution, they are not evidence for the Big Bang.

If the early universe was a plasma of free electrons and protons, then photons were constantly scattered and trapped; if the universe cooled enough for electrons to bind to protons (forming neutral hydrogen), then photons could finally travel freely; if this event allowed the first light to escape, then it is known as Recombination.

If an ambulance siren changes pitch as it passes you, then you are experiencing a wave frequency shift due to motion; if this principle applies to all waves including light and sound, and was described by Christian Doppler, then it is the Doppler Effect.

If the Big Bang model is correct, then the intense heat of the first few minutes would allow for nuclear fusion; if calculations based on this heat predict a 3:1 ratio of Hydrogen to Helium, and if our observations of the oldest stars match this ratio, then the Big Bang Theory is strongly supported.

If the universe is expanding in all directions, then the distance between almost all galaxies is increasing; if increasing distance results in Red Shift, then most galaxies should show Red Shift; if only a few nearby galaxies (like Andromeda) show Blue Shift due to local gravity, then the statement that "most" show Blue Shift is false.

If we measure the observed wavelength of a spectral line and subtract the laboratory (rest) wavelength, then we find the change; if we divide this change by the rest wavelength, then we get the value 'z'; if this 'z' value represents the extent of the stretch, then it is the formal calculation for redshift.

If space is expanding, then galaxies will move further apart; if the volume of the universe increases while mass remains constant, then the average density must decrease; if expansion continues or accelerates, then distant galaxies will eventually move so far that their light can no longer reach us.

If there is a proportional relationship between a galaxy's distance and its recession speed, then there must be a value that represents that slope; if v=H0​×d, then H0​ is that value; if this was named after the discoverer of expansion, then it is the Hubble Constant.

If a photon is traveling through a medium (space) that is expanding, then the photon's path is lengthened; if the physical length of the wave is pulled apart by the expansion of the fabric of space, then the wavelength must increase; if increased wavelength equals lower frequency, then the light shifts toward the red.

If the Big Bang was the origin of space itself, then there was no "outside" or "center" for it to happen in; if every point in the universe was part of the initial singularity, then the expansion is happening everywhere at once; therefore, the idea of a specific "center point" in pre-existing space is a misconception.

If COBE and WMAP provided early maps of the CMB, then scientists needed a higher resolution mission to study the fluctuations; if the European Space Agency launched the Planck mission in 2009 for this specific purpose, then Planck is the correct high-precision instrument for mapping the CMB.

If light has a finite speed (c), then it takes time to travel across space; if a galaxy is 1 billion light-years away, then the light we see today left that galaxy 1 billion years ago; if we are seeing the galaxy as it existed then, then this concept is defined as look-back time.

If shorter wavelengths are on the left (blue) and longer wavelengths are on the right (red) of a standard spectrum, then a rightward shift indicates an increase in wavelength; if an increase in wavelength is the definition of a Red Shift, then the term is Red Shift.