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- The Big Bang

The Big Bang Theory

There are a lot of misconceptions about the Big Bang Theory. The first one is in its name. The term "big bang" actually came about as a pejorative term while physicists were describing it. The "big bang" was more like a rapid expansion and not an "explosion". What was expanding? Space-time itself. The second misconception is that the Universe "began" at the Big Bang. This isn't entirely true. Much like a balloon doesn't "begin" to exist when you start blowing air in it, the Universe didn't begin to exist when it started expanding. In both cases, the thing expanding existed prior to its expansion.

There are a myriad of evidences for the Big Bang Theory; here are the big four:

  • Ubiquity of the Primordial Elements
  • The Doppler Effect
  • The Hubble Constant
  • Cosmic Microwave Background Radiation
Remember, scientific theories are arrived at via observed evidence. The evidences listed above are some of the initial oddities that astronomers observed while looking out into the stars, and also the ramifications of gravity in the Theory of Relativity led to the formulation of the Big Bang Theory. Some previous knowledge about electromagnetic radiation (light) is needed before fully understanding these evidences.

Electromagnetic Radiation

Electromagnetic radiation is all around us. We use it to see, and we use it to power our computers. The quantum nature of electromagnetism is represented by the photon. Photons act as both particles and waves. The wave qualities of the photons is what helps us understand the evidences of the Big Bang. Photons themselves travel at 3 x 108 meters / second, but since it's a wave, it also has a frequency. The frequency depends on how much energy is put into producing the photon, much like a sound wave. Sound waves all travel at the speed of sound, but due to different frequencies, we get to hear different notes (ex. the note "A" is generally 440 Hz or one of its multiples like 880 Hz, 220 Hz, etc.). For example, the Visible Light portion of the electromagnetic frequency falls between the values of 7 x 10-7 meters and 4 x 10-7 meters. These frequencies include all of the colors of the rainbow - 7 x 10-7 representing red and 4 x 10-7 representing violet. Red light has less energy than violet light - thus red has a longer frequency than violet. The frequency immediately before (longer) the red frequency is called "infrared", and the frequency directly after (shorter) violet is called "ultraviolet".

Electromagnetic Spectrum (in meters)
Gamma Radiation: 10-14
X-ray Radiation: 10-10
Ultraviolet Radiation: 10-8
Visible Light: 10-7
Infared Radation: 10-6
Microwave Radiation: 10-2
Radiowave Radiation (includes AM, FM, TV signals, etc.): 100 and above

The distinction between X-rays and Gamma rays depends on the source emitting the radiation. For example, nuclear exlposions will emit Gamma radiation, however high energy electrons will emit X-ray radiation, even though they might have the same frequency. This is one of the reasons why Hawking Radiation is described as X-rays and not Gamma rays.

Big Bang Evidences