Earth is a tiny, fragile exception in the cosmos. For humans and the other things living on our planet, practically the entire cosmos is a hostile and merciless environment. Our planet, Earth, is an oasis not only in space, but in time. It may feel permanent, but the entire planet is a fleeting thing in the lifespan of the universe. For nearly two-thirds of the time since the universe began, Earth did not even exist.
Nor will it last forever in its current state. It might even expand large enough to swallow Earth itself. After all, humans have only just begun deciphering the cosmos. While the distant future is difficult to accurately predict, the distant past is slightly less so. By studying the radioactive decay of isotopes on Earth and in asteroids, scientists have learned that our planet and the solar system formed around 4.
The universe, on the other hand, appears to be about Scientists arrived at that number by measuring the ages of the oldest stars and the rate at which the universe expands. They also measured the expansion by observing the Doppler shift in light from galaxies, almost all of which are traveling away from us and from each other. In the distant future, the galaxies will be so far away that their light will not be visible from Earth.
Put another way, the matter, energy and everything in the universe including space itself was more compact last Saturday than it is today. The same can be said about any time in the past — last year, a million years ago, a billion years ago. A bit farther back in time, everything was in the same spot.
Or really the entire universe not just the matter in it was one spot. Don't spend too much time considering a mission to visit the spot where the universe was born, though, as a person cannot visit the place where the Big Bang happened.
It's not that the universe was a dark, empty space and an explosion happened in it from which all matter sprang forth. Time, too, began with the big bang. Space itself expanded from a single point to the enormous cosmos as the universe expanded over time. The universe contains all the energy and matter there is. Much of the observable matter in the universe takes the form of individual atoms of hydrogen, which is the simplest atomic element, made of only a proton and an electron if the atom also contains a neutron, it is instead called deuterium.
As the early universe inflated, there are some theories that say that different "pockets" broke away and formed different universes. These different places could be expanding at different rates, include other types of matter, and have different physical laws than our own universe.
Livio pointed out there could be galaxies in these other universes — if they exist — but we have no way right now of knowing for sure. So the number of galaxies could even be greater than billion, when considering other universes. In our own cosmos, Livio said, astronomers will be better able to refine the number upon the launch of the James Webb Space Telescope for which his institute will manage the mission operations and science.
Hubble is able to peer back at galaxies that formed about million years after the Big Bang. After James Webb launches in , astronomers anticipate they can look as far back as million years after the Big Bang. While it is interesting to count the number of galaxies in our universe, astronomers are more interested in how galaxies reveal how the universe was formed. According to NASA, galaxies are a representation of how matter in the universe was organized — at least, on the large scale. Scientists are also interested in particle types and quantum mechanics, on the small side of the spectrum.
Because Webb can look back to the early days of the universe, its information will help scientists better understand the structures of the galaxies around us today. Webb will also allow scientists to gather data on the types of stars that existed in these very early galaxies," NASA said of Webb's mission. These studies will also reveal details about merging galaxies and shed light on the process of galaxy formation itself. Scientists are also interested in the role that dark matter plays in the assembly of galaxies.
While some of the universe is visible in forms such as galaxies or stars, dark matter is what makes up most of the universe — about 80 percent of it. While dark matter is invisible in wavelengths of light or through emissions of energy, studies of galaxies dating back to the s indicated there was far more mass present in them than what was visible with the naked eye. The visible matter we see collects inside this scaffolding in the form of stars and galaxies. The way dark matter 'clumps' together is that small objects form first, and are drawn together to form larger ones.
Webb's powerful mirrors will allow scientists to look at galaxy formation — including the role of dark matter — up close. The sun seems impossibly big, but in the great scheme of things, it's a pinprick, one of about billion stars in the Milky Way galaxy, which you can see on a clear night as a pale, white mist stretched across the sky. And it gets worse. There are maybe billion galaxies detectable by our telescopes, so if each star was the size of a single grain of sand, just the Milky Way has enough stars to fill a 30 foot by 30 foot stretch of beach three feet deep with sand.
And the entire Earth doesn't have enough beaches to represent the stars in the overall universe. Such a beach would continue for literally hundreds of millions of miles. Holy Stephen Hawking, that is a lot of stars. But he and other physicists now believe in a reality that is unimaginably bigger still. I mean, first of all, the billion galaxies within range of our telescopes are probably a minuscule fraction of the total. Space itself is expanding at an accelerating pace. String theory would provide the landscape of all permitted laws of physics, and cosmic inflation would provide the mechanism to generate actual universes to populate that landscape.
This would mean that for each pocket universe, string theory would provide a particular set of physical laws. The smallest structures would determine the largest structures. Max Tegmark, a cosmologist at MIT, goes further. He envisions four kinds of multiverses that may exist, labeling them "Levels":.
All of these universes are immense beyond the imagination, but are any truly infinite in the literal meaning of the term, going on without end or limit? As Linde told me recently, "This is subtle. Suppose a bubble of a new vacuum is created in an eternally expanding universe — a standard picture in eternal chaotic inflation and the string theory landscape Level II. Then, from the outside, each such bubble looks like a finite bubble that grows infinitely in time.
But from the inside, it looks like an infinite open universe. Of course, 'looks like' means that someone is looking, but nobody can see an infinite universe. Tegmark's Level I is accepted by almost all cosmologists i. All this shows how far and how fast our knowledge of the cosmos has expanded: Generating multiple universes by eternal chaotic inflation, a theory developed in the last four decades, is now the standard model of cosmology. I asked Steven Weinberg, a founder of the Standard Model of particle physics now at the University of Texas at Austin, about other kinds of multiple universes.
Because the fundamental quanta in quantum mechanics is not the individual particle or billiard ball but is something called the 'wave function,' which describes all possibilities, it may be that the universe, the comprehensive universe, the whole thing, is some kind of quantum mechanical superposition of different possibilities.
The philosopher David Lewis proposed a similar theory of "modal realism" in which all possible worlds, astonishingly, are actual worlds. But to achieve such immensity and diversity, wouldn't there still have to be, at a deeper level, some rock-bottom, fundamental "universe-generating laws" to create all the multiple universes in the first place, each of which has its own different laws? Where is bedrock reality?
Not every cosmologist is a full convert to the multiverse. As cosmologist George Ellis told me, "I don't like the word 'multiverse. Moreover, he stresses the basic problem of other domains of space-time. Maybe we are seeing the same patch of space-time over and over again. Einstein's theory [of general relativity] allows this to happen because space-time not only is curved, but also it can have a different connectivity structure. So maybe we can go for several hundred million light-years [in one direction] and then suddenly we return from that side [to where we started from], just like Pac-Man did in those early computer games.
We would be seeing many images, maybe hundreds of images, of the same galaxy. Physicist Paul Davies, director of the Beyond Center for Fundamental Concepts in Science at Arizona State University, said he gives "two cheers [not the full three] for the multiverse," because "although there are good reasons for supposing that what we see may not be all that exists, the hypothesis falls far short of being a complete theory of existence.
You're going to need some laws of physics. All theories of the multiverse assume quantum physics to provide the element of spontaneity, to make the bangs happen. They assume pre-existing space and time. They assume the normal notion of causality, a whole host of pre-existing conditions. Davies then made his deep point. What about those meta-laws that generate all the universes in the first place? Where did they come from? Then what about the laws or meta-laws that impose diverse local laws upon each individual universe?
How do they work? What is the distribution mechanism? Davies dismissed the idea that "any universe you like is out there somewhere. I think such an idea is just ridiculous and it explains nothing. Having all possible universes is not an explanation, because by invoking everything, you explain nothing. Davies' critique of the multiverse goes deeper. To explain the universe, he rejects "outside explanations," he said. Then Davies makes his damning comparison. In fact, I think both explanations — multiverse and God — are pretty much equivalent.
Davies said he appreciates all the motivations and mathematics that drive inflation theory, along with the multiple universes that seem the compulsory consequences. But still, he said, he feels that an infinite number of universes does not make sense. Something's amiss. What's my take? Long out of childhood, but still feeling childlike in the presence of a multiverse, I try to assess the possibilities.
I like to categorize things, to discern scope and breadth. Here are seven possible mechanisms that could generate multiple universes. What's more, these seven mechanisms for generating multiple universes are not mutually exclusive. Several, or even all of them, could be true — and they could nest in various ways, one within others, others within one. In a multiverse, one cannot avoid infinity, and infinity does strange things. There are two types of possible infinities in a multiverse: Type I: A single universe may be infinite in size e.
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