Ok let me start a thread on parallel universe

1. A parallel universe, also known as a parallel dimension, alternate universe, or alternate reality, is a hypothetical self-contained plane of existence, co-existing with one's own. The sum of all potential parallel universes that constitute reality is often called a multiverse

2 .The term "parallel universe" is more general, without implying a relationship, or lack of relationship, with our own universe. A universe where the very laws of nature are different – for example, one in which there are no Laws of Motion – would in general count as a parallel

3. In 1884, Edwin A. Abbott wrote the seminal novel exploring this concept called Flatland: A Romance of Many Dimensions. It describes a world of two dimensions inhabited by living squares, triangles, and circles, called Flatland, as well as Pointland (0 dimensions)

4. Lineland (1 dimension)& Spaceland (three dimensions) & finally posits the possibilities of even greater dimensions. Isaac Asimovin his foreword to the Signet Classics 1984 edition, described Flatland as The best introduction one can find into the manner of perceiving dimension

5. Our universe may live in one bubble that is sitting in a network of bubble universes in space. Sample image looks like below

6. Parallel universe theories suggest their are infinite Earth's out there, just a bit different from ours like below

7. The Universe, as far as the most powerful telescopes can see (even in theory), is vast, huge and massive. Including photons and neutrinos, it contains some 10^90 particles, clumped and clustered together into hundreds-of-billions-to-trillions of galaxies

8. Each one of those galaxies comes with around a trillion stars inside (on average), and they’re strewn across the cosmos in a sphere some 92 billion light years in diameter, from our perspective.

9. But, despite what our intuition might tell us, that doesn’t mean we’re at the center of a finite Universe. In fact, the evidence indicates something quite to the contrary

10The reason the Universe appears finite in size to us the reason we can’t see anything that’s more than a specific distance away isn’t because the Universe actually finite in sizebut is rather because the Universe has only existed in its present state for a finite amount of time

11  If you learn nothing else about the Big Bang, it should be this: the Universe was not constant in space or in time, but rather has evolved from a more uniform, hotter, denser state to a clumpier, cooler and more diffuse state today.

12. This has given us a rich Universe, replete with many generations of stars, an ultra-cold background of leftover radiation, galaxies expanding away from us ever-more-rapidly the more distant they are, with a limit to how far back we can see.

13. Inflation isn’t like a ball — which is a classical field — but is rather like a wave that spreads out over time, like a quantum field.

14. In 1954, a young Princeton University doctoral candidate named Hugh Everett III came up with a radical idea: That there exist parallel universes, exactly like our ­universe. These universes are all related to ours; indeed, they branch off from ours

15. our universe is branched off of others. Within these parallel universes, our wars have had different outcomes than the ones we know. Species that are extinct in our universe have evolved and adapted in others. In other universes, we humans may have become extinct.

16. This thought boggles the mind and yet, it is still comprehensible. Notions of parallel universes or dimensions that resemble our own have appeared in works of science fiction and have been used as explanations for metaphysics.

17. But why would a young up-and-coming physicist possibly risk his future career by posing a theory about parallel universes?

18. With his Many-Worlds theory, Everett was attempting to answer a rather sticky question related to quantum physics: Why does quantum matter behave erratically? The quantum level is the smallest one science has detected so far.

19. The study of quantum physics began in 1900, when the physicist Max Planck first introduced the concept to the scientific world. Planck's study of radiation yielded some unusual findings that contradicted classical physical laws.

20. Heisenberg Uncertainty Principle
In fairly short order, physicists studying the quantum level noticed some peculiar things about this tiny world. For one, the particles that exist on this level have a way of taking different forms arbitrarily.

21. For example, scientists have observed photons -- tiny packets of light -- acting as particles and waves. Even a single photon exhibits this shape-shifting [source: Brown University]. Imagine if you looked and acted like a solid human being

22. when a friend glanced at you, but when he looked back again, you'd taken a gaseous form.
This has come to be known as the Heisenberg Uncertainty Principle. The physicist Werner Heisenberg suggested that just by observing quantum matter, we affect the behavior of that matter

23 Thus, we can never be fully certain of the nature of a quantum object or its attributes, like velocity and location.This idea is supported by the Copenhagen interpretation of quantum mechanics.

24. Posed by the Danish physicist Niels Bohr, this interpretation says that all quantum particles don't exist in one state or the other, but in all of its possible states at once. The sum total of possible states of a quantum object is called its wave function.

25. The state of an object existing in all of its possible states at once is called its superposition.
According to Bohr, when we observe a quantum object, we affect its behavior. Observation breaks an object's superposition and essentially forces the object to choose one state

26. This theory accounts for why physicists have taken opposite measurements from the same quantum object: The object "chose" different states during different measurements.

27. Bohr's interpretation was widely accepted, and still is by much of the quantum community. But lately, Everett's Many-Worlds theory has been getting some serious attention. Read the next page to find out how the Many-Worlds interpretation works.

28. Many Worlds Theory
Young Hugh Everett agreed with much of what the highly respected physicist Niels Bohr had suggested about the quantum world. He agreed with the idea of superposition as well as with the notion of wave functions.But Everett disagreed with Bohr in one thing

29. To Everett, measuring a quantum object does not force it into one comprehensible state or another. Instead, a measurement taken of a quantum object causes an actual split in the universe. The universe is literally duplicated,

30. splitting into one universe for each possible outcome from the measurement. For example, say an object's wave function is both a particle and a wave. When a physicist measures the particle, there are two possible outcomes: It will either be measured as a particle or a wave.

31. This distinction makes Everett's Many-Worlds theory a competitor of the Copenhagen interpretation as an explanation for quantum mechanics.

Parallel universe Part 1 thread is completed since it's huge topic iam planning to include many parts in upcoming threads ,I hope this thread is useful for all thank you ..