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Sreeshan · 2024-03-06T13:06:17.142Z

About: • Around 14 billion years ago, the Universe began from a very small region that was extremely hot and dense • Then there was a giant explosion, which is known as the Big Bang • This caused the universe to expand from a single point, cooling as it does so, to form the universe today • Each point expands away from the others • This is seen from galaxies moving away from each other, and the further away they are the faster they move • As a result of the initial explosion, the Universe continues to expand • An analogy of this is points drawn on a balloon where the balloon represents space and the points as galaxies • When the balloon is deflated, all the points are close together and an equal distance apart • As the balloon expands, all the points become further apart by the same amount • This is because the space itself has expanded between the galaxies • Therefore, the density of galaxies falls as the Universe expands Evidence for the Big Bang: • Since there is more evidence supporting the Big Bang theory than the Steady State theory, it is the currently accepted model for the origin of the Universe • The main pieces of evidence for the Big Bang are • Galactic red-shift • Cosmic Microwave Background (CMB) radiation Evidence from CMB Radiation: • The discovery of the CMB (Cosmic Microwave Background) led to the Big Bang theory becoming the currently accepted model • The CMB is a type of electromagnetic radiation which is a remnant from the early stages of the Universe • It has a wavelength of around 1 mm making it a microwave, hence the name Cosmic Microwave Background • In 1964, Astronomers discovered radiation in the microwave region of the electromagnetic spectrum coming from all directions and at a generally uniform temperature of 2.73 K • They were unable to do this any earlier since microwaves are absorbed by the atmosphere • Around this time, space flight was developed which enabled astronomers to send telescopes into orbit above the atmosphere • According to the Big Bang theory, the early Universe was an extremely hot and dense environment • As a result of this, it must have emitted thermal radiation • The radiation is in the microwave region • This is because, over the past 14 billion years or so, the radiation initially from the Big Bang has become redshifted as the Universe has expanded • Initially, this would have been high-energy radiation, toward the gamma end of the spectrum • As the Universe expanded, the wavelength of the radiation increased • Over time, it has increased so much that it is now in the microwave region of the spectrum • The CMB radiation is very uniform and has the exact profile expected to be emitted from a hot body that has cooled down over a very long time • This phenomenon is something that other theories (such as the Steady State Theory) cannot explain Red-Shift: • By observing the light spectrums from supernovae in other galaxies there is evidence to suggest that distant galaxies are receding (moving further apart) even faster than nearby galaxies • These observations were first made in 1998 • The light spectrums show that light from distant galaxies is redshifted, which is evidence that the universe is expanding • As a result, astronomers have concluded that: • All galaxies are moving away from the Earth • Galaxies are moving away from each other • This is what is expected after an explosion • Matter is first densely packed and as it explodes it, it moves out in all directions getting further and further from the source of the explosion • Some matter will be lighter and travel at a greater speed, further from the source of the explosion • Some matter will be heavier and travel at a slower speed, closer to the source of the explosion • If someone were to travel back in time and compare the separation distance of the galaxies: • It would be seen that galaxies would become closer and closer together until the entire universe was a single point • If the galaxies were originally all grouped at a single point and were then exploded a similar effect would be observed • The galaxies that are the furthest are moving the fastest - their distance is proportional to their speed • The closer galaxies are moving slower

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Sreeshan

Mar 06, 2024

Edited: Mar 06, 2024

The Big Bang Theory

in Sreeshan

About:

Around 14 billion years ago, the Universe began from a very small region that was extremely hot and dense
Then there was a giant explosion, which is known as the Big Bang
This caused the universe to expand from a single point, cooling as it does so, to form the universe today
Each point expands away from the others
- This is seen from galaxies moving away from each other, and the further away they are the faster they move
As a result of the initial explosion, the Universe continues to expand
An analogy of this is points drawn on a balloon where the balloon represents space and the points as galaxies
When the balloon is deflated, all the points are close together and an equal distance apart
As the balloon expands, all the points become further apart by the same amount
This is because the space itself has expanded between the galaxies
- Therefore, the density of galaxies falls as the Universe expands

Evidence for the Big Bang:

Evidence from CMB Radiation:

Red-Shift:

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