Until recently, astronomers estimated that the Big Bang occurred between 12 and 14 billion years ago.

But recent studies have put the universe at 13.8 billion years old, with an uncertainty of only 1%.

The uncertainty here comes due to the expansion and expansion of the universe, in addition to the results of some discoveries regarding the existence of stars older than the universe itself.

Scientists came to this number after more than a century of debate about the age of the universe, including a period when many talked about the universe being infinitely old.

But how do scientists estimate the age of the vast, extended and mysterious universe in the first place?

According to Live Science, we can determine the age of the universe to some extent by analyzing light and other types of radiation that travel from deep space.

The better the level of telescopes used in monitoring light and radiation, the better the scientists' answer about the age of the universe, and of course it becomes more accurate.

According to the NASA website, astronomers estimate the age of the universe in two different ways:

  • The first: by searching for the oldest stars, as the simplest and most direct way to measure the age of the universe is by looking closely at the things in it, which are the stars.

  • The second method is to measure the expansion rate of the universe and extrapolate back to the Big Bang, much as crime investigators can trace the origin of a bullet through holes in a wall.

Scientists believe that the light of the microwave background radiation appeared 400 thousand years after the Big Bang (NASA)

2020 data

Currently, the universe is believed to be around 13.8 billion years old.

These results were identified by a number of scientists who announced their findings in 2020 after re-evaluating data from the European Space Agency's Planck Spacecraft and analyzing data from the Atacama Cosmology Telescope. in Chile.

The new figure reached for the age of the universe in 2020 is about 100 million years older than the previous estimate, which was determined by data transmitted by the Planck spacecraft in 2013.

The new data was made based on the spacecraft's and telescope's survey of the "cosmic microwave background radiation," a faint glow of light that fills the universe and is believed to be a remnant of light from the Big Bang.

Scientists combined that data with existing models to measure how quickly different types of matter and celestial bodies appeared after the universe began to form, and then scientists were able to estimate the period back to the occurrence of the Big Bang.

Scientists believe that the microwave background radiation light appeared 400,000 years after the Big Bang, and that it contains accurate indications of how the first stars and galaxies were formed, so by measuring how far this diffused light is, scientists get an estimate of how old the universe is.

Not discovered until the mid-1960s, the cosmic microwave background radiation is electromagnetic radiation that permeates the entire universe with the same intensity and distribution, and no specific or tangible source can be identified.

Cosmic rays can be seen at a distance of 13.8 billion light-years in all directions from Earth (NASA)

cosmic background

When we watch the sky with a light telescope, we see vast distances between stars and galaxies dominated by blackness, and this is what scientists call the cosmic background.

But when we use a radio telescope that can see radio waves, it will depict a faint light that fills that background.

These rays do not change from place to place, but are spread evenly throughout the universe.

Cosmic rays can be seen at a distance of 13.8 billion light-years in all directions from Earth;

Which prompted scientists to determine that this is the true age of the universe.

However, it is not an indication of the true extent of the universe, since space has been expanding since the beginning of the universe, and it is expanding faster than the speed of light, so cosmic rays are just the farthest point in time we can see.

Regarding the age of the most recent universe, which is 13.8 billion years, Simon Ayoola, a research scientist in the Center for Computational Astrophysics at the Flatiron Institute in New York City, led a team of scientists who re-examined the maps of the cosmic microwave background radiation using the Atacama telescope, This is according to their study published in the "Journal of Cosmology and Astroparticle Physics" in December 2020.

"Although these maps cover a smaller area than those produced by Planck's team, the improved resolution allows for more accurate measurements," says Ayola.

Ayoola and his colleagues made a scientific breakthrough by being able to observe the cosmic microwave background radiation on an ever smaller scale, and using the highly sensitive Atacama Telescope, they were able to see many details of what happened in the early universe.

By comparing these high-resolution maps with current predictions for the age of the universe, the team came up with an age of 13.8 billion years.

The oldest stars

Big Think states that the universe cannot be younger than its oldest stars;

Therefore, scientists measure the ages of the first stars that formed in the universe as a guide to knowing the age of the universe itself.

The life cycle of a star depends on its mass and how quickly it consumes its nuclear fuel.

The greater the size of the star, the faster it burns its fuel reserves, while small stars consume their fuel in a longer period, as the largest stars burn and explode after only a few million years, and a star of mass such as the sun can continue to fuse hydrogen for about 10 billion years.

But if the star is very small with a mass of no more than a tenth of that of the Sun, it can continue to fuse hydrogen for hundreds of billions of years, longer than the current age of the universe of 13.8 billion years.

To find out the age of the universe, scientists study globular star clusters, a dense stellar group consisting of about a million stars that all formed at about the same time.

By determining the masses of these stars, scientists can estimate when the globular cluster was formed.

The scientists concluded that the oldest globular clusters contain stars that have a mass less than the sun by 0.7, which indicates that they are between 11 and 18 billion years old.

The expansion rate of the universe is known as the Hubble constant and is estimated at 46,200 miles (74,351.508 km) per hour per million light-years (NASA)

The expansion of the universe and the Hubble constant

According to the Inverse website, the expansion rate of the universe is known as the Hubble Constant, which is estimated at 46,200 miles (74,351,508 kilometers) per hour per million light-years.

The American astronomer Edwin Hubble first calculated the "Hubble constant" in the 1920s, after discovering that many galaxies were moving away from Earth.

Hubble also noticed that the further away a galaxy is, the faster it is moving away.

Based on his observations, the Hubble Law was reached, which showed a correlation between how far an object is and the speed at which it recedes.

Using this law, scientists were able to estimate the expansion rate of the universe.

Scientists were then able to use the Hubble constant to estimate the age of the universe by going all the way back to the Big Bang.

This extrapolation is based on the current density and composition of the universe, which indicates the history of the expansion of the universe.

And in 2012, NASA's Wilkinson Microwave Anisotropy Probe used that data to estimate the age of the universe at about 13.772 billion years, with 59 million years plus or minus.

A year later, the Planck spacecraft estimated the age of the universe at 13.82 billion years.