How Old is the Universe?

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Ingeniero, docente, aficionado a la ciencia y ciencia ficción

3 years ago

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Topics: Science, Astronomy, Cosmology, Information

Greetings to all. the universe is 13,700 million years old. but the answer to the question is not as easy as it seems, how do we know how old the universe is?

Until about 100 years ago, there was a firm belief that the universe was eternal, had always been there and always would be, its state was static. This belief led Einstein to incorporate in his equations of general relativity, the cosmological constant, as a mechanism to avoid the collapse of the universe due to gravity, predicted in the solution of his equations and thus guarantee its invariability, just as Observations seemed to indicate it.

However, four scientists, independently, would propose that the universe was not in a stationary state and that, on the contrary, it was expanding, its works, initially ignored, would be later claimed, going on to be consecrated as the currently accepted cosmological model .

Alexander Friedmann, who defined, based on the statements of General Relativity, the equations that allow describing the geometry of the universe and also predict the expansion of the same.

Georges Lemaître, who was the first to propose, based on experimental data from Vesto Slipher and Carl Wilhelm Wirtz, the expansion of the universe, in addition to the “Primitive Atom Hypothesis”, which would later be called the Big-Theory theory. Bang.

Howard P. Robertson who, together with Arthur Geoffrey Walker, based on general relativity, also proposed the theory of an expanding universe, in addition to predicting the redshift of light(1) from the objects that moved away from us, and develop a metric that coincides with the results also obtained by Friedman and Lemaître.

The cosmological model developed independently by these scientists is known as FLRW Model or Metric (Friedmann-Lemaître-Robertson-Walker) and describes an expanding, homogeneous and isotropic universe.

Later Edwin Hubble, after observing the so-called galactic nebulae and studying its spectrum and redshift, could determine that they were further away than previously believed and that they were moving away from us, which led him to indicate that they were galaxies equal to the Milky Way and not objects inside it.

Hubble’s observations allowed us to corroborate Lemaître’s Big-bang theory and put an end to the idea of a static universe, consistent with this, Hubble was able to calculate using the data obtained from his observations of the redshift of several galaxies, that the universe It was 2000 million years old. Of course Hubble was not right, this method was not entirely accurate, in addition the fossil and geological record dated the age of the earth in not less than 3000 million years, which was not consistent with their observations.

In 1998, a group of researchers from the Space Telescope Science Institute (STScI), headed by Adam Riess, studying the supernovas 1a(2), a type of supernova, with a well-known and predictable behavior, could determine that the universe was not only expanded, it was making it faster and faster, but I’ve talked about this before. The fact is that this discovery allowed us to redefine the composition of the universe and bring back the idea of Einstein’s cosmological constant, associating it with dark energy and turning this factor into an element to be considered in the calculation of the age of the universe.

Another very important discovery to date the age of the universe is the microwave background radiation, a type of fossil radiation, produced 400,000 years after the Big Bang, when the early universe had cooled enough for the hydrogen nuclei and helium could be combined with electrons to form atoms and the radiation of matter is decoupled, that event left a trace of perceptible photons in the radioelectric spectrum that lasts until now in the microwave band.

The estimated age of the universe is the result of one or several estimates according to different methodologies, depending on the procedure followed, the figure can change from hundreds, to billions of years. To date we have three more or less accurate estimates about the age of the universe, explain what each of them consists of:

Age Based on the data from the WMAP Probe

The WMAP probe (Wilkinson Microwave Anisotropy Probe), is a device launched by NASA in 2002, which is located in orbit around the Sun at the Lagrangean point L2 on Earth. The purpose of WMAP is to study the cosmic microwave background and its anisotropies, it is able to measure the temperature difference between any two points of space.

The bodies that emit radiation also release energy in the form of heat, consequently the cosmic microwave background being a residual radiation of the Big-bang, also has a signature of heat that is in all the inverse, this signature is about 2 ° K , which is why there is no absolute zero in the universe, in any part of the universe, however distant from any body that emits radiation, there will be a temperature of approximately 2 ° K.

This temperature is not the same everywhere, there are certain small fluctuations, these fluctuations are what are called anisotropies of the cosmic microwave background and is the main object of measurement of the WMAP.

The data of the WMAP, allows to date the universe in an age of about 13,700 million years, with an error of about 200 million years, this calculation is based on the estimation of the size of the universe at the moment of the decoupling of the radiation of the Matter, which can be calculated from the first spectral peak of the cosmic microwave background, knowing this information, and using the Friedman equations, we can calculate the age of the universe. Of course the value of this age is subject to the geometry of the universe that is chosen, having variations between one and another.

Age Based on Cosmological Parameters

Currently the accepted cosmological model is called ΛCDM by Lambda – Cold Dark Matter, this roughly describes the composition of the universe which would be composed of 70% dark energy, expressed by Λ, 26% dark matter it is a type of matter different from the baryonic one (everything that is formed by protons and neutrons) and that does not interact neither with this one nor with the photons, but with the gravity; and 4% baryonic matter. This model is the basis for calculating the age of the universe according to cosmological parameters.

From the Friedmann equations, we can deduce the zero time of the universe, for it is necessary to know the components of the density parameter (Ω) and the Hubble constant, consequently, the parameters necessary for the calculation of the age of the universe They are the following:

H0 or Hubble constant, which is a parameter of Hubble’s law, which defines the redshift of a galaxy’s light in relation to its distance of us.
ΩR or current radiation density.
ΩM or density of matter, dark and baryonic.
ΩΛ or vacuum density or cosmological constant – dark energy density.

Again using the data provided by the WMAP, for the amount of dark energy and matter, while using the value of the Hubble constant calculated from the data obtained from the observation of the Supernovas 1a, a value can be obtained approximate for the age of the universe of 13,600 million years.

Age Based on the CNO Cycle

The CNO cycle is one of the two fusion reactions, through which the stars transform hydrogen into helium, is the most common type of reaction in massive stars with temperatures above 15,000 ° K, in this cycle, the stars use as catalysts carbon, nitrogen and oxygen nuclei to fuse protons (hydrogen nuclei) in helium-4 nuclei.

Some studies show that this cycle is slower than previously thought, consequently, the age of the universe would be higher than expected, taking about 15,000 million years. However, these studies have been questioned.

Gravitational waves

On August 17, 2017, in an unprecedented event, LIGO(3) (Laser Interferometer Gravitational-Wave Observatory) detected an emission of gravitational waves and simultaneously the Fermi Gamma-ray Space Telescope, detected an emission of gamma rays that, coupled with the non-detection of gravitational waves by VIRGO (another interferometer similar to LIGO located in Italy) which places these emissions in a blind point of the latter device, allowed to interpolate the sector of the sky from where the gravitational waves had to come, this guide, to the scientists where to orient the telescopes to look for the source and 10 hours later in the Observatory of the Bells in Atacama Chile, the origin of the phenomenon was found in the galaxy NGC-4993 located at 140 millions of light years in the constellation of Hydra

The phenomenon corresponded to a Kilonova, the collision of two neutron stars, which was observed throughout the electromagnetic spectrum, this particular event and the opportunity to be confirmed visually, together with the data obtained from previous observations of gravitational waves, allowed to date the age of our universe between 11,900 and 15,700 million years. Age range that although it is quite large allows to confirm the estimations made by other methodologies, and opens the door to a new methodology to specify the age of our universe.

So, in short, we can say that the age of our universe, although we do not know it accurately, is around 13,700 million years ago, this has been estimated after studying the cosmic microwave background and the redshift of light emitted by type 1a supernovae, this under the assumption that the density of the universe Ω, is compatible with a plane geometry universe. To shorten the matter, it is estimated that our universe is 13,700 million years old.

Well, so far this publication, I hope you liked it, I am attentive to your comments and I thank you in advance for your support. Thanks for your attention.

Notes

Redshift of light: The redshift, refers to the light waves that are perceived have a wavelength that has shifted to the wavelength of the color red. As the object moves away its light waves will tend to shift to red, or at higher wavelengths, although with lower frequencies, such as infrared, microwaves and radio waves. On the other hand, if the object approaches, its sling length will become smaller and its frequency higher, with a shift to blue, ultraviolet, x-rays, etc.
Supernova 1a: A type 1a supernova, is produced when a white dwarf forms a binary system with another star, whose mass is being attracted to the white dwarf, forming an accretion disk, exceeding the limit of Chandrasekhar and the white dwarf collapse on itself producing an explosion whose brightness can be determined within a margin of error of between 10 and 20%, this predictability makes this type of supernovas ideal for determining intergalactic distances.
LIGO: is an observatory of gravitational waves that is located in Hanford Site (Washington) and Livingston (Louisiana), in opposite coasts of the United States, its purpose is the arrest of waves caused in the gravitational field, which are provoked for massive cosmic events such as; supernovas, fusions of black holes or neutron stars. These waves move at the speed of light. It consists of two laser interferometers located more than 3000 km away from each other, each consisting of two arms of 4 km, each of which circulates a laser that is reflected in mirrors, when a gravitational wave is detected one of the arms stretches while the other shrinks, this causes differences in the time that the lasers travel the arms, these variations of time are what allow the detection of the wave. On September 14, 2016, LIGO detected for the first time a gravitational wave that, according to the models, corresponded to the collision of two black holes, this confirmed the existence of this type of disturbances of the gravitational field, which had been predicted by the general relativity.