Primordial Radiation: High Energy Light Big Bang Quiz

If the early universe was extremely hot and dense, then it was filled with high-energy plasma. If the universe expanded and cooled over 13.8 billion years, then that original high-energy light would stretch into longer wavelengths. If those waves are now in the microwave range, then they represent the earliest light we can detect. Therefore, the CMB is the afterglow of the Big Bang.

If free electrons are present, then they scatter photons in every direction, preventing light from traveling long distances. If the universe was too hot for atoms to form, then electrons remained free. Therefore, light was "trapped" in a fog until the universe cooled enough for neutral atoms to form.

If the universe cooled to about 3000 Kelvin, then protons could finally capture electrons to form neutral Hydrogen atoms. If electrons are bound in atoms, then they no longer scatter photons. Therefore, light could finally travel freely through space, an event known as Recombination.

If the fabric of space itself is expanding, then any light traveling through it will have its wavelength stretched along with space. If stretching a wavelength moves it toward the red end of the spectrum, then it is a redshift. Therefore, this specific type is called Cosmological Redshift.

If the synthesis of heavy elements requires high density and temperature for a long time, then the conditions must last. If the Big Bang expansion was extremely rapid, then the temperature dropped below the fusion threshold within minutes. Therefore, only the lightest elements had time to form before the "cosmic furnace" turned off.

If Wien's Law states that peak wavelength is inversely proportional to temperature (λmax​∝1/T), then a decrease in temperature must result in an increase in wavelength. If the universe is cooling, then the light shifts toward the longer (colder) end of the spectrum. Therefore, the statement is false.

If the earliest light we detect (stretched to microwaves) originated as high-energy Gamma or X-rays, then the source must have been incredibly hot. If that heat was spread throughout all of space, then the matter must have been packed tightly together. Therefore, the spectrum proves a hot, dense beginning.

If Edwin Hubble observed that a galaxy's redshift is proportional to its distance, then the universe must be expanding uniformly. If this relationship is expressed as v=H0​d, then it is the foundational law of expansion. Therefore, it is Hubble's Law.

If the universe was a hot soup of subatomic particles, then collisions would eventually stick protons and neutrons together. If this occurred between 3 and 20 minutes after the Big Bang, then it created the first nuclei. Therefore, this is Big Bang Nucleosynthesis.

If a theory predicts a specific afterglow (CMB), a specific mix of light elements (H/He ratio), and an expanding universe (Redshift), then observing those three things confirms the theory. If Mars' water or the Milky Way's shape don't directly relate to the origin of the entire universe, then they are not primary evidence. Therefore, A, B, and D are correct.

If the radiation started at thousands of degrees during Recombination and is now only 2.7 degrees above absolute zero, then a massive amount of cooling has occurred. If cooling in space is caused by the stretching of light waves (expansion), then the universe must have grown significantly. Therefore, 2.7K is proof of vast expansion.

If the photons released during the early stages of the universe were high-energy, then they had very short wavelengths. If space has expanded by a factor of about 1100 since Recombination, then those wavelengths have increased 1100 times. Therefore, high-energy light has shifted into the low-energy microwave band.

If we trace the Big Bang back to t=0, then we reach a point of infinite density. If we reach 10−43 seconds (Planck time), then gravity and quantum mechanics conflict. Therefore, the Planck Era represents the theoretical limit of our current understanding.

If the CMB were perfectly smooth, then matter would never have clumped together. If there are tiny "hot" and "cold" spots (anisotropies), then these indicate regions of slightly higher or lower density. Therefore, gravity acted on these density differences to build galaxies.

If the temperature was trillions of degrees, then even protons and neutrons could not stay together. If protons are made of quarks and gluons, then those particles would roam free. If electrons were also present as fundamental particles, then A, B, and C are the correct constituents.

If expansion causes a redshift and cooling, then the opposite process (contraction) must cause a blueshift and heating. If the wavelengths are squeezed, then the energy of the photons increases. Therefore, the background radiation would get hotter.

If gravity is an attractive force, then the expansion of the universe should be slowing down. If observations of distant supernovas show that the expansion is actually speeding up, then an unknown "repulsive" energy must exist. Therefore, we call this Dark Energy.

If the universe is remarkably flat and uniform, then it must have smoothed itself out very early on. If a burst of exponential expansion occurred at t=10−36 seconds, then it explains these features. Therefore, this event is called Inflation.

If light was constantly bouncing (scattering) off electrons in the early plasma, then it couldn't travel. If Recombination happened, then the light scattered one "last" time before traveling to us. Therefore, looking at the CMB is like looking at the physical "surface" of the early universe.

If the Big Bang was the expansion of space itself, then it didn't happen in space. If every point in the universe was part of the initial hot state, then the expansion is happening everywhere at once. Therefore, there is no "center" to the Big Bang.