Hot Big - Bang Model

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What is a Big - Bang Model?

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A cosmology model is the standard Hot Big Bang model. It was written for an upper-level university course in modern physics that required almost no mathematics.

One can recall that when Einstein finished developing the General Theory of Relativity in 1915, the theory's prediction of an expanding universe clashed with established philosophical principles of the time. As a result, Einstein introduced the cosmological constant as a fudge factor to cause the universe to be static. When Hubble discovered that the universe was expanding in 1929, Einstein promptly abandoned the cosmological constant, calling it "my greatest error."


Cosmology is the study of large-scale natural phenomena. Traditionally, “large scales” cover a spectrum of around 1–8000 Mpc, encompassing everything from our local group of galaxies to the farthest light we can detect. Insofar as they determine relative distances, ages, structure, and gravitational properties of local patches of the universe, as well as valuable knowledge on elementary particle physics and gravity, phenomena occurring within a galaxy (ours or another) and interacting with galactic media, stars, supernovae, black holes, gamma-ray bursts, and so on, they are also part of cosmology.

The steady-state model of cosmology, however, retained a vestige of the concept of a static universe until the early 1960s. This model, championed by Sir Fred Hoyle and others, proposed that, as the universe was expanding, matter was being produced everywhere in the universe, resulting in a constant total density of matter in the universe. The process that produced this matter was never discovered.

When more information about the universe's large-scale structure became available, the steady-state model became more difficult to apply.

One of the most important of these was discovered in 1965 by AT&T Bell Labs' Penzias and Wilson, who discovered all-pervasive isotropic microwave radiation that corresponded to what would be released by a body with a temperature of -270 0C. This radiation is commonly referred to as cosmic microwave background radiation and is considered to be a legacy of the big bang.

A big bang occurred about 15 billion years ago when the universe's size was zero and the temperature was infinite. The universe began to grow at a near-light speed after that.

The sequence of events in this model are given below:

Time t = 0 (about 15 billion years ago)

Radius r =0

T = Infinite temperature

Density = mass per volume = Infinite

t = 0.01  second

T =100,0.00,000,000 0C

Radiation is the most common form of energy.

 t = 2 seconds

T = 10,000,000,000 0C

100 million kg per cubic meter is the density.

Pairs of protons and antiprotons, as well as neutrons and antineutrons, begin to develop.

t= 3 minutes 

T = 1,000,000,000 0C.

Hydrogen and helium are formed when protons and neutrons collide.

t= 10,000 years 

T = 10,000 degrees Fahrenheit.

0.000,000,000,000,000,01 kg per cubic meter is the density.

The bulk of the energy is now in the form of mass rather than radiation.

The process of condensation into stars begins. Below is a photograph of a star birthplace taken by the Hubble space telescope.

t = 15 billion years (now)

The temperature is -270 degrees Fahrenheit. (The temperature in this graph comes from the Penzias and Wilson experiment described earlier.)

10–27 kg per cubic meter is the density.

According to the Traditional Hot Big Bang model, each part of the universe's mass-energy is gravitationally attracted to the rest of the universe's mass-energy, slowing the rate of expansion.

A key concern was whether the decrease in the rate of expansion is significant enough to cause the expansion to come to a halt and reverse at some stage.

If this is the case, the Big Crunch will occur when the universe's size is reduced to zero, with infinite density and temperature. Such a universe is referred to as closed. The geometry of spacetime in this case is identical to that of a sphere's surface.

If not, the universe will continue to expand indefinitely. Such a universe is referred to as free. The geometry is similar to that of a saddle's surface in this case. The data on the universe's long-term destiny is too close to call. To put it another way, the universe's geometry is nearly smooth. The Bang-Bang-Bang cosmology is a variant of the Big Bang cosmology. The Big Crunch will occur if the world is closed. The circumstances of the Big Crunch, on the other hand, are similar to those of the Big Bang. As a result, the conclusion of one universe cycle heralds the start of the next.

Huston Smith had an interview with the Dalai Lama in the early 1960s. The Dalai Lama inquired about the state of scientific cosmological theories at the time. The Steady State model, the Big Bang model, and the Bang-Bang-Bang model were all represented by Smith. The Dalai Lama said that the last one was the most accurate of the three.

FAQ (Frequently Asked Questions)

Q1. Explain the Evidence of Big Bang.

Ans. Many pieces of observational data that are consistent with the Big Bang provide support for the Big Bang. Since scientific theories are not confirmed, none of these can be used to confirm the Big Bang. Many of these facts are in agreement with the Big Bang and other cosmological theories, but when taken together, they prove that the Big Bang is the best current model for the Universe. There are some of my observations:

Olbers' paradox is the night sky's darkness.

The Hubble Law is a relationship between linear distance and redshift. The data is now excellent.

Homogeneity is a collection of data that shows our position in the Universe is not special.

Isotropy - very clear evidence that the sky appears the same in all directions.

Q2. Is the Universe Big or Infinite?

Ans. According to observations, the Universe's radius of curvature is greater than 70 billion light-years. However, the observations allow for either a positive or negative curvature, and this spectrum includes a flat Universe with an infinite curvature radius. Even though it is curved, the volume of the negatively curved space is infinite. As a result, we realize that the volume of the visible Universe is more than 20 times greater than the volume of the Universe. We can only see a small portion of an object with a broad radius of curvature, so it appears smooth. Flat Euclidean space is the simplest mathematical model for computing the observed properties of the Universe. While this model is infinite, we do know that the Universe is enormous.