There would be an infinity if the universe didn't do this

Our universe BIG BANG - The beginning of everything

From: Franziska Konitzer, Stefan Geier

Status: 02/18/2021

In the beginning there was the Big Bang: Our universe is said to have emerged from an infinitely tiny point around 13.82 billion years ago. Our cosmos, all space and all time have only existed since that point - right?

The universe is infinitely large and has it always been there? No. Although scientists at the beginning of the 20th century actually assumed such a static universe, they have since found out: The universe is expanding, it is expanding. But that also means that it must have started expanding at some point, a long time ago. This beginning, this beginning of everything, is what scientists call the Big Bang.

Discovered: The expansion of the universe

Edwin Hubble discovered that distant galaxies are all moving away from us. It was the first indication of the expansion of the universe.

Idealized: The universe as a Guglhupf

The perfect model universe: the Guglhupf, in this case with amaretto raisins

To visualize the expansion of the universe, one can simply imagine the universe as a yeast cake. The individual galaxies would correspond to the raisins baked in them. The cake rises in the oven. Everything moves away from each other, not just the raisins.

Imagination: Everything moves away from everything

"You can imagine it in a similar way in the universe. The yeast cake model also applies, a yeast cake in which raisins are distributed. I sit on a raisin and the cake is baked. Then all the other raisins move away from me path."

Jochen Weller, Ludwig Maximilians University in Munich

DIY: Instructions for an expanding universe

  • If you don't like raisins in yeast cake, you can also visualize the expanding universe as an alternative. Ingredients required for this: a balloon, a pen and some breath.
  • Draw dots on the balloon when it is deflated. You can save yourself this step if you have a balloon that has already been punctured.
  • Blow.
  • You will see: All points on the balloon move away from each other. There is also no center point on the surface of the balloon that would not move.
  • It is similar with the galaxies in the universe. They are all moving away from each other. There is no center of the universe.
  • The balloon is of course a simplification. Its points expand on a two-dimensional surface, while three-dimensional galaxies expand in our cosmos. Strictly speaking, it is four-dimensional space-time itself that is expanding.
  • This is where the balloon analogy reaches its limits.

Old light. Through the billions of years to almost back to the Big Bang

The Hubble eXtreme Deep Field shows galaxies, some of whose light has traveled through the universe for more than 13 billion years.

When everything is moving away from each other faster and faster, one can legitimately ask: Where does everything come from? Astronomers and cosmologists can undertake such time travel with light. You work with telescopes such as the Hubble Space Telescope. They can use it to collect old light, old enough that researchers can use it to look almost all the way back to the beginning. Light is fast. To be more precise, light is the fastest that we know so far. It travels through space at around 300,000 kilometers per second. If you were to switch on a large lamp on the moon that is visible on earth, it would take a good second before we see its light. Our sun shines a little further away, the light needs about eight minutes from it to us. So your light is eight minutes 'old' when it hits the retina in our eyes. So the further away the place from which we can collect light, the older it is. If a telescope is good enough, you can use it to snap up light particles that are almost as old as the universe itself.

Oldest light. When was the big bang?

The cosmic microwave background is very homogeneous. The color differences indicate temperature fluctuations of a few millionths of a degree.

Even the best telescopes in the world cannot see all the way back to the Big Bang. Because at the very beginning the universe was far too dense and far too hot for light to spread through it. It probably took around 400,000 years for our cosmos to expand and cool down to such an extent that it could become transparent to light. The radiation that was released at this point fills our universe to this day. It is the cosmic microwave background radiation.

Most recently, the Planck Space Telescope precisely measured this microwave background for the entire sky and, so to speak, took a "baby photo" of the universe. But what happened in the first 400,000 years directly after the Big Bang cannot be directly revealed by cosmic microwave background radiation. It is therefore a baby photo of the universe and a curtain before the Big Bang at the same time.

However, with the help of the data from the Planck space telescope, scientists were able to determine more precisely when the Big Bang probably took place: around 13.82 billion years ago.

Microwave background: Planck and the secrets of the big bang

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The legacy of Planck

After the big bang: What did the universe look like shortly after the Big Bang?

"Strictly speaking, we don't see anything because it's too hot to really see something. We feel that it's very hot. If we were to ask ourselves what we can feel, it might be somewhere hotter, somewhere less hot ... Do I feel something like this that is accumulating, or that more matter is accumulating somewhere than elsewhere? Amazingly, the answer is: No, we don't, but everything would be the same regardless of where I put my arm out being hot."

Anna Ijjas, Max Planck Institute for Gravitational Physics, Hanover

But: What really happened during the Big Bang?

Symbol for the beginning of time with the Big Bang: A pointer is attached to the clock tower of the Jakobikirche in Lübeck.

The short answer to the question of what happened in the Big Bang is: Nobody knows. And: Nobody can know. Of course, one can extrapolate and mentally rewind the expanding universe. It gets smaller and hotter, you raise the curtain of the cosmic microwave background, you can't see anything and then it gets much smaller and even hotter. Too small, too hot for atoms to stick together. The universe is filled with an unimaginably hot, sizzling soup. The popular big bang theory just got that far. But what happened at time zero can no longer be described by the Big Bang theory. Strictly speaking, the Big Bang theory is a story that only begins after the actual Big Bang.

Now, when you ask yourself what was before the Big Bang, sometimes the answer scientists get is that the question doesn't make sense. Because in the Big Bang, not only the matter that fills our universe was created, but also space-time itself. Thus there was no "before" the Big Bang, since time itself only came into being with the Big Bang.

Shortly after the big bang: Quantum fluctuations and inflation theory provide an explanation

"If we look around, we see galaxies all over the sky. And the question is where they actually come from, what their origin is. The model is that there were regions in the early universe that had more mass than other regions that had less mass. These fluctuations at the smallest level of particles become huge as the universe expands. They form the seeds for galaxies and all the structures we see in the universe. And now we can see how the galaxies are distributed in the universe and whether this can be reconciled with the distribution that we know from the smallest scales in microphysics. And that works very, very well. "

Jochen Weller, Ludwig Maximilians University in Munich

Excursion! What has happened since the Big Bang: The universe in 3D

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A Flight Through the Universe, by the Sloan Digital Sky Survey

Reality? The big bang and its alternatives

  • The scenario that happened shortly after the Big Bang is described using so-called Big Bang theories.
  • The big bang theories start very shortly after the big bang and extend to the emergence of cosmic microwave background radiation, around 300,000 to 400,000 years after the big bang.
  • Scientists do not have older or younger observations. However, some hope is placed in gravitational waves, which should actually have been left over from the Big Bang. With the current technical possibilities, however, these gravitational waves cannot yet be measured.
  • Measurements of cosmic background radiation show that around 13.82 billion years have passed since then. The universe has been expanding ever since.
  • One component of the Big Bang theories is cosmic inflation: It describes that the universe grew exponentially, i.e. inflationary, at the very beginning. This inflation could have inflated and frozen quantum fluctuations. These fluctuations are then reflected as tiny temperature fluctuations in the cosmic microwave background. Nowadays they can be seen as large-scale structures in the universe, as huge, dark empty spaces, as brightly shining filaments and clusters of galaxies.
  • However, the Big Bang theory cannot explain everything. For example, we have known for several decades that the universe is not only expanding, but also that it is getting faster and faster. However, researchers do not know what is behind this. That's why they call it dark energy.
  • As long as one does not know the nature of dark energy, one cannot fully describe the development of the universe.
  • Another problem: With the Big Bang, two existing theories come into conflict, namely Einstein's theory of relativity and quantum physics. Viewed individually, both make predictions that have so far been consistently confirmed experimentally. However, these two theories are incompatible, they cannot be mathematically reconciled with one another. That's a problem when you need both at the same time, like with the Big Bang. There is currently no working theory of quantum gravity.
  • Since the Big Bang is currently not fully understood and common Big Bang theories are reaching their limits, alternative explanations and scenarios also have a right to exist.
  • Some of them are more, some less plausible.
  • For example, one bizarre theory plays with the idea that our universe might have popped out of a black hole. However, there is likely no way to prove or disprove this theory.
  • Another theory plays with the idea of ​​a big bounce instead of a big bang. Big impact instead of big bang, a constant cycle. Accordingly, the universe contracted before the Big Bang and then expanded again. The question of whether this has been going on forever, or whether this cycle has started at some point, cannot be answered by the Big Bounce theory either. In a way, it has only postponed the problem of the very beginning.
  • In addition, there is no evidence for this theory either. The Big Bounce Theory can at least score mathematically with scientists, since it does not require a theory of quantum gravity.
  • There are other suggestions as to how the Big Bang might have happened. There are theories that take into account the following factors: mirror verses, multiverses, chaotic inflation, plasma universes.
  • What all these theories have in common is that, although they could be mathematically possible, none of them has made verifiable predictions so far.
  • That is why most scientists today use the standard model of cosmology to understand the history and development of our cosmos, even if it cannot answer all open questions by far.

Behind the curtain: Notes on the Big Bang

Could gravitational waves perhaps provide clues about the Big Bang?

Gravitational waves: Beyond the baby photo of the big bang?

"Gravitational waves also arise in the Big Bang or in the phase of very rapid expansion. Gravitational waves are actually always created when matter is accelerated irregularly. Now, of course, one cannot imagine that something like the Big Bang, the most violent event in the history of the universe, no gravitational waves. Actually, there should be these gravitational waves as a background everywhere - as an afterglow of the big bang, similar to the cosmic background radiation, only in the cosmic gravitational waves. If we could discover this kind of gravitational waves, it would be like a book of the big bang in which we could read directly. That would then no longer be the baby photo of the universe. Rather, it would really be the embryonic stage that we could examine there.

Jochen Weller, Ludwig Maximilians University in Munich

Big Bang Theory: The best at the end - or at the very beginning?

The history of our universe had a beginning, we call it the Big Bang. We do not know its true nature and its origin and we probably cannot. But the theoretical description of everything that came after that, namely the Big Bang theory, is still the best we have at the moment.

question Curious? Should we report more often on this topic?