Research, Technology

How and why do galaxies disappear from view?

Despite the fact that humanity has been able to describethe physical laws that govern the universe, we are unable to understand and fully realize them. The Big Bang, about 13.8 billion years ago, marked the beginning of everything we know. But if the universe had a beginning, would it have an end? In about five billion years, the Sun will die, taking our planet with it. Around the same time (plus or minus a billion years), the Milky Way will collide with its nearest neighbor, the Andromeda galaxy. But what's next? Many years have passed since scientists proposed the expansion of the Universe: the farther away from us are other galaxies, the faster they seem to be moving away from us. This process lasts for about six billion years and occurs not because the galaxies are physically moving away from the Earth, but rather because the Universe is full of gravitationally bound objects. Over time, these galaxies will become completely unobservable, even if we move towards them at the speed of light.

Researchers believe that mysterious dark energy (which has not yet been detected) is responsible for the expansion of the Universe

If you follow the universe from its momentbirth, then moving forward in time, we will come to a single, consistent conclusion - our Universe has existed for 13.8 billion years and consists of 68% dark energy. 27% are dark matter and 4.9% are ordinary matter.


  • 1 Observations of the universe
  • 2 Gravity and the expansion of the universe
  • 3 Future of the Universe
  • 4 Secrets of dark energy

Universe Observations

In the late 1920s, the American astronomer EdwinHubble discovered that the universe is expanding. He came to this conclusion by observing galaxies and measuring the distance to those closest to us. After 70 years, scientists have come to the conclusion that the Universe is not just expanding - distant galaxies are moving away from us at great distances. at an ever-increasing rate. So, within the observable universeThere are about 2 trillion galaxies. 97% of them are beyond our reach. But there is something interesting - over time, new, previously unseen galaxies will open up to our gaze.

According to the General Theory of Relativity (GR), ourThe universe cannot remain static. The reason is simple: The universe is filled with an equal amount of matter and energy everywhere and in all directions and depends on three factors: the initial expansion rate, the amount of total matter and energy, and the ratio of different types of energy (matter, dark matter, neutrinos, radiation, dark energy and etc.). All these conditions, taken into account in the calculations, show both the past and the future of the Universe.

Thanks to dark energy, distant galaxies are already accelerating in their apparent speed of receding from us.

The Milky Way is amazingan awe inspiring spectacle for anyone and offers breathtaking views of the vast number of stars in our galaxy. However, there are trillions of other galaxies beyond its borders, and almost all of them are moving away from us.

Over the past few decades, astronomerswere able to determine what the universe looks like on an extragalactic scale. The way galaxies assemble into groups, clusters, and filaments has allowed researchers to understand the large-scale structure of the universe. And given observations of the CMB (cosmic microwave background), we are seeing a compelling picture of how the universe came to be as we know it.

Gravity and the expansion of the universe

The continued acceleration ensures that eacha galaxy not gravitationally bound to our own will eventually recede and become not only inaccessible but unobservable after a certain point in time. But as soon as the light leaves a distant cosmic source, the expanding universe stretches the wavelength of this light.

Redshift - a phenomenon associated with the removal of observable objects from us due to the expansion of the universe. Moving away, the light "turns red", and when approaching, it "shifts" to the purple side.

The redshift in the spectra of galaxies is explained by the Doppler effect, which scientifically substantiates the idea of ​​an expanding universe.

But what would we see if we looked ata galaxy whose light has not yet reached our eyes? The most distant object available for observation is 46 billion light-years from Earth. At the same time, any object that is located within 61 billion light years will someday become observable - the light from these objects already heading towards us. And despite the fact that the Universe is expanding, this light will someday reach the Earth.

It must also be taken into account that the speed of light is finite: the longer it takes the photons toto get from a distant galaxy to Earth, the more important is the expansion of the universe. Read more about what secrets dark energy hides here, don't miss it.

Do you want to always be aware of the latest news from the world of science and high technology? Subscribe to our channel in Telegram - so you definitely won't miss anything interesting!

Future of the Universe

According to the new model of the universe, its observed expansion may stop in 100 million years. When this happens, the end of the universe will mark the so-called Big squeeze - one of the possible scenarios for the future of the universe,in which expansion changes over time into contraction. This will cause the universe to collapse into a singularity - the point from which it was born almost 14 billion years ago.

When we look at the Universe, the farther we look, the deeper the past we look.

By measuring light sources at multiple distances,by detecting their redshift and then measuring their actual size compared to the apparent size, astronomers reconstruct the entire expansion history of the universe. But since it is determined by the different types of matter and energy present in it, scientists will have to thoroughly study all its contents. And this, as you know, is not an easy task.

Once this happens, astrophysicists will be able toapply the obtained data to the laws of gravity according to general relativity. This means that all galaxies that are not gravitationally bound to us will eventually disappear from our field of vision, receding at an ever-increasing rate due to the constant expansion of space. As a result, the space observed with telescopes will look much smaller than it does today.

Don't Miss: Physicists Rethink the Structure of the Universe. Dark energy no longer needed?

Since in a few hundred billion or,perhaps in trillions of years, all galaxies except the local group will be far away and disappear from sight forever. According to astrophysicist and science popularizer Lawrence Krauss, space will expand faster than the speed of light.

Secrets of dark energy

The most important link in the cosmological puzzle isdark energy, without which the observable universe is meaningless. Roughly speaking, dark energy is a growing trend of empty space that spontaneously creates even more empty space, thereby pushing away everything that is not bound by gravity.

Someday our universe will disappear. Fortunately, this will not happen soon, so do not worry.

Thus, by the year 3,000,000,000,000, astronomers will be able to observe only gravitationally bound "local group" of galaxies: The Milky Way and Andromeda, the Large and Small Magellanic Clouds and several other tiny galaxies, says astrophysicist and science popularizer Lawrence Krauss.

According to Krauss, the observable universe willappear neither expanding nor contracting, but relatively small and static. What's more, some undetectable event could have happened in the early universe. In addition, dark energy itself may change in the future, which means that the expansion of the Universe will probably slow down.