Multiverse facts for kids

The multiverse is the idea that there are many, many universes, not just our own. It suggests that all of space, time, matter, energy, and even the physical laws that govern them, exist across these different universes. People call these other universes by many names, like 'parallel universes,' 'alternate universes,' or 'many worlds.' Imagine it like a giant quilt made of many different patches, where each patch is a universe.

When Did People First Think of the Multiverse?

The idea of many worlds is very old. Some people think the Greek philosopher Anaximander first talked about it around 600 BCE. However, we are not fully sure if he meant many worlds existing at the same time or one after another.

The first thinkers who definitely believed in countless worlds were the Ancient Greek Atomists. These included Leucippus and Democritus in the 400s BCE. Later, Epicurus and Lucretius also explored this idea. In the 200s BCE, the philosopher Chrysippus thought the world ended and restarted forever. This was like saying there were many universes over time. The idea of multiple universes became clearer in the Middle Ages.

In 1895, an American thinker named William James used the word "multiverse." But he used it in a different way than we do today. The idea of a multiverse in modern science first came up in 1895. This was during a discussion between scientists Ludwig Boltzmann and Ernst Zermelo.

In 1952, scientist Erwin Schrödinger gave a talk. He joked that what he was about to say might sound "crazy." He explained that when his math equations showed several different histories, they were "not alternatives, but all really happen at the same time." This idea of things existing in many states at once is called "superposition."

Searching for Proof of Other Universes

In the 1990s, the idea of the multiverse became very popular in science fiction. Because of this, scientists started talking about it more. They also wrote more articles about it in science magazines.

Around 2010, scientists like Stephen M. Feeney looked at data from a space probe called WMAP. They thought they found signs that our universe had crashed into other parallel universes long ago. But later, scientists looked at more data from WMAP and another probe called Planck. Planck had much clearer pictures. This new look did not find any strong proof of such a crash. Also, there was no sign that other universes were pulling on ours with gravity.

In 2015, an astrophysicist named Dr. Ranga-Ram Chary thought he might have found proof of other universes. He looked back in time to right after the Big Bang, when our universe began. He studied the cosmic radiation spectrum. This is like an echo from the early universe. He found a signal that was 4,500 times brighter than it should have been. This was based on how many protons and electrons scientists thought were in the early universe.

This super bright signal might mean that a parallel universe added some of its matter to our universe. If more protons and electrons had been added, more atoms would have formed. This would have made the signal much stronger. However, there is a 30% chance this signal is just noise. It could also be light from far-off galaxies or dust clouds near our own galaxy. So, scientists are still debating this finding.

Different Kinds of Possible Worlds

When we think about many possible universes, not all of them might actually exist. Some might happen many times. For example, over endless time, there could be countless universes. But only a few might have life like ours. And only one might have our exact history. Some scientists think that a universe with life like Earth's is very special. Most possible universes would never have life in the way we know it.

On the other hand, some scientists and popular stories imagine a multiverse where universes are very similar. In these, humans exist in many equally real universes. But each universe has a slightly different history.

There is a debate about how "real" these other worlds are. This is part of the "many-worlds interpretation" (MWI) of quantum mechanics. In another idea called Quantum Darwinism, you don't have to believe that all these different "branches" of the universe are equally real.

Images for kids

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  Schrödinger's cat in the many-worlds interpretation. Here, the universe splits into different possibilities.

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  An animation of a universe that cycles, meaning it expands and then shrinks back.

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  An idea of a twin universe, with the beginning of time in the middle.

See also

In Spanish: Multiverso para niños

• Beyond black holes
• Cosmogony
• Eternity
• Impossible world
• Measure problem (cosmology)
• Modal realism
• Parallel universes in fiction
• Philosophy of physics
• Philosophy of space and time
• Simulated reality
• Twin Earth thought experiment
• Ultimate fate of the universe