Describe what makes up our universe

At least not yet. And it may never have it. But that does not stop us from contemplating the past, a very young and primordial Universe. Since the beginning of the twentieth century we know that the Universe is expanding and something that expands, although infinite in principle, necessarily increases in size. So we can say that there are different types of infinite as, even though the Universe of the distant past can also be defined as infinite, it has been increasing in size.

The Universe of the distant past was smaller than it is today yet already contained everything that exists, has existed and will exist. Its energy density was much higher than it is today.

Everything that exists now existed before but was more concentrated, tighter, occupied a smaller volume. In this context of a very young Universe things that seem strange to us and that can normally no longer happen in the present time could occur: the transformation of matter into energy, and vice versa, was one of them.

Today matter only becomes energy under very special conditions: inside stars or in nuclear bombs to name a few better-known situations. However previously matter and energy were interchangeable, namely, when we are talking about the distant past it does not make sense to talk about one or the other of them seperately. Matter and energy are like two sides of the same coin.

This also applies to the present day, but in the present all, or almost all , of the "coins" have only one of their sides exposed, revealing only heads or only tails. In the past, it was as if all of them or almost all were in the air, heads or tails, undefined. This is how the very young Universe was. But we could also speak of an earlier period of which we know very little. It is possible that our Universe has always existed and that the expansion discovered in the twentieth century only represents the current dynamic phase of the Cosmos, in which the Universe expands so that one day it will contract.

It is a cyclical movement: when it is very small it will expand again, with the cycle continuing successively and eternally. In this case humanity would only witness one moment of expansion, one which will be repeated numerous times. The other hypothesis to be considered is one in which the Universe is not eternal but had a well-defined beginning.

According to this view, in which everything that is born must die, the Universe would also have a known or unknown "shelf life". However, the laws of physics are not prepared to deal with their own emergence and these unknowns about the origin of the Universe are waiting for an answer that we might never reach.

What we can confirm today as true is that in a certain moment - around 14 billion years ago - the Universe started to expand. And we call this moment the Big Bang. In its original formulation the expression Big Bang represented the instant that the Universe was born, a hypothesis conceived by George Gamow and his collaborators in the early s, and it explained the current Universe very well. However, it established cosmology as a powerful parallel with the myths of theological creation the most common in our culture is Genesis in the Bible, "Let there be Light!

Thus , although some scientists rejected this theory - and it is important to note that in a literal sense the name Big Bang is an obviously undignified name for a hypothesis about the Universe - the alternatives proposed also did not have complete solutions. Two things survive from this divergence: the term Big Bang, created by detractors to make light of Gamow's idea; and the dichotomy that haunts us to this day, that of the infinite and the finite.

In any case , it was at the beginning of the expansion where the "Higgs field", conceived in by Peter Higgs, stood out. And still within this analogy, the Higgs field designated values for each coin: Is it matter? The group determined that an unknown force — dubbed dark energy — was pushing against the universe in the apparent void of space and accelerating its momentum; the scientists' findings earned physicists Adam Riess, Brian Schmidt and Saul Perlmutter the Nobel Prize in Physics in Considering that dark energy makes up about three-quarters of the universe, understanding it is arguably the biggest challenge facing scientists today, astrophysicist Mario Livio, then with the Space Telescope Science Institute at Johns Hopkins University in Baltimore, Maryland, told Live Science sister site Space.

Originally published on Live Science. Mindy Weisberger is a Live Science senior writer covering a general beat that includes climate change, paleontology, weird animal behavior, and space. Mindy holds an M. Her videos about dinosaurs, astrophysics, biodiversity and evolution appear in museums and science centers worldwide, earning awards such as the CINE Golden Eagle and the Communicator Award of Excellence.

Existing space and ground-based telescopes have made substantial progress in studying the subsequent evolution of galaxies. But all this moving further and further backward in time might have left you a bit dizzy. Figure 4 summarizes the entire history of the observable universe from the beginning in a single diagram. The universe was very hot when it began to expand. We have fossil remnants of the very early universe in the form of neutrons, protons, electrons, and neutrinos, and the atomic nuclei that formed when the universe was 3—4 minutes old: deuterium, helium, and a small amount of lithium.

Dark matter also remains, but we do not yet know what form it is in. The universe gradually cooled; when it was about , years old, and at a temperature of about K, electrons combined with protons to form hydrogen atoms. At this point, as we saw, the universe became transparent to light, and astronomers have detected the CMB emitted at this time. During the next several hundred million years, small fluctuations in the density of the dark matter grew, forming gravitational traps that concentrated the ordinary matter, which began to form galaxies about — million years after the Big Bang.

By the time the universe was about a billion years old, it had entered its own renaissance: it was again blazing with radiation, but this time from newly formed stars, star clusters, and small galaxies.

Over the next several billion years, small galaxies merged to form the giants we see today. Clusters and superclusters of galaxies began to grow, and the universe eventually began to resemble what we see nearby. During the next 20 years, astronomers plan to build giant new telescopes both in space and on the ground to explore even further back in time. In , the James Webb Space Telescope, a 6. The predictions are that with this powerful instrument see Introduction to the Big Bang we should be able to look back far enough to analyze in detail the formation of the first galaxies.

Twenty-seven percent of the critical density of the universe is composed of dark matter. To explain so much dark matter, some physics theories predict that additional types of particles should exist.

One type has been given the name of WIMPs weakly interacting massive particles , and scientists are now conducting experiments to try to detect them in the laboratory.

Dark matter plays an essential role in forming galaxies. Since, by definition, these particles interact only very weakly if at all with radiation, they could have congregated while the universe was still very hot and filled with radiation.

They would thus have formed gravitational traps that quickly attracted and concentrated ordinary matter after the universe became transparent, and matter and radiation decoupled.

This rapid concentration of matter enabled galaxies to form by the time the universe was only — million years old. WIMPs weakly interacting massive particles are one of the candidates for the composition of dark matter. Skip to main content. The Big Bang. Clusters of galaxies emit lots of X-rays because they contain a large quantity of high-temperature gas.

By measuring the quantity of X-rays from a cluster, astronomers can work out both the temperature of the cluster gas and also the mass of the cluster. Theoretically, in a Universe where the density of matter is high, clusters of galaxies would continue to grow and so, on average, should contain more mass now than in the past.