Posted on by Matt Williams

What is the Multiverse Theory?

Could our Universe be part of a wider Multiverse? And could these other Universes support life? Credit: Jaime Salcido/EAGLE Collaboration

If you’re a fan of science fiction or fantasy then chances are, at some point, you’ve read a book, seen a movie, or watched a series that explored the concept of multiple universes. The idea being that within this thing we call time and space, there are other dimensions where reality differs from our own, sometimes slightly, sometimes radically. Interestingly enough, this idea is not restricted to fiction and fantasy.

In science, this is known as the Multiverse Theory, which states that there may be multiple or even an infinite number of universes (including the universe we consistently experience) that together comprise everything that exists: the entirety of space, time, matter, and energy as well as the physical laws and constants that describe them. In this context, multiple universes are often referred to as parallel universes because they exist alongside our own.

The term was coined in 1895 by the American philosopher and psychologist William James. However, the scientific basis of it arose from the study of cosmological forces like black holes and problems arising out of the Big Bang theory. For example, within black holes it is believed that a singularity exists – a point at which all physical laws cease – and where it becomes impossible to predict physical behavior.

Beyond this point, it is possible that there may be an entirely new set of physical laws, or just slightly different versions of the ones that we know, and that a different universe might exist. Theories like cosmic inflation support this idea, stating that countless universes emerged from the same primordial vacuum after the Big Bang, and that the universe as we know it is just what is observable to us.

Max Tegmark’s taxonomy of universes sums up the different theories on multiple universes. IN this model, there are four levels that classify all major schools on thought on the subject.

In Level One, different universes are arranged one on top of the other in what is called Hubble Volumes, all having the same physical laws and constants. Though each will likely differ from our own in terms of distribution of matter, there will eventually be Hubble volumes with similar, and even identical, configurations to our own.

In Level Two, universes with different physical constants exist and the multiverse as a whole is stretching and will continue to do so forever, but some regions of space stop stretching and form distinct bubbles, like gas pockets in a loaf of rising bread.

In Level Three, known as the Many Worlds Interpretation of Quantum Mechanics, observations cannot be predicted absolutely but a range of possible observations exist, each one corresponding to a different universe. Level Four, aka.the Ultimate Ensemble devised by Tegmark himself, considers as equally real all universes that can be defined by mathematical structures. In other words, universes with the same or different constants may exist.

We have written many articles about multiverse for Universe Today. Here’s an article about searching life in the multiverse, and here’s an article about parallel universe.

If you’d like more info on the Multiverse, check out some Recent Innovations about the Concept of Universe, and here’s a link to an article about the Size of the Universe.

We’ve also recorded an entire episode of Astronomy Cast all about Multiverses. Listen here, Episode 166: Multiverses.

Sources:
http://en.wikipedia.org/wiki/Multiverse
http://www.sciencedaily.com/releases/2010/01/100112165249.htm
http://www.astronomy.pomona.edu/Projects/moderncosmo/Sean%27s%20mutliverse.html
http://en.wikipedia.org/wiki/William_James
http://en.wikipedia.org/wiki/Big_Bang
http://en.wikipedia.org/wiki/Inflation_%28cosmology%29

Posted on by Matt Williams

Cosmology

Planck Time
The Universe. So far, no duplicates found@

[/caption]

Ever wonder why we are here, how and why the universe that we inhabit came to be, and what our place is in it? If so, than in addition to philosophy, religion, and esotericism, you might be interested in the field of Cosmology. This is, in the strictest sense, the study of the universe in its totality, as it is today, and what humanity’s place is in it. Although a relatively recent invention from a purely scientific point of view, it has a long history which embraces several fields over the course of many thousand years and countless cultures.

In western science, the earliest recorded examples of cosmology are to be found in ancient Babylon (circa 1900 – 1200 BCE), and India (1500 -1200 BCE). In the former case, the creation myth recovered in the EnûmaEliš held that the world existed in a “plurality of heavens and earths” that were round in shape and revolved around the “cult place of the deity”. This account bears a strong resemblance to the Biblical account of creation as found in Genesis. In the latter case, Brahman priests espoused a theory in which the universe was timeless, cycling between expansion and total collapse, and coexisted with an infinite number of other universes, mirroring modern cosmology.

The next great contribution came from the Greeks and Arabs. The Greeks were the first to stumble onto the concept of a universe that was made up of two elements: tiny seeds (known as atoms) and void. They also suggested, and gravitated between, both a geocentric and heliocentric model. The Arabs further elaborated on this while in Europe, scholars stuck with a model that was a combination of classical theory and Biblical canon, reflecting the state of knowledge in medieval Europe. This remained in effect until Copernicus and Galileo came onto the scene, reintroducing the west to a heliocentric universe while scientists like Kepler and Sir Isaac Newton refined it with their discovery of elliptical orbits and gravity.

The 20th century was a boon for cosmology. Beginning with Einstein, scientists now believed in an infinitely expanding universe based on the rules of relativity. Edwin Hubble then demonstrated the scale of the universe by proving that “spiral nebulae” observed in the night sky were actually other galaxies. By showing how they were red-shifted, he also demonstrated that they were moving away, proving that the universe really was expanding. This in turn, led to the Big Bang theory which put a starting point to the universe and a possible end (echoes of the Braham expansion/collapse model).

Today, the field of cosmology is thriving thanks to ongoing research, debate and continuous discovery, thanks in no small part to ongoing efforts to explore the known universe.

We have written many articles about cosmology for Universe Today. Here’s an article about the galaxy, and here are some interesting facts about stars.

If you’d like more info on cosmology, the best place to look is NASA’s Official Website. I also recommend you check out the website for the Hubble Space Telescope.

We’ve recorded many episodes of Astronomy Cast, including one about Hubble. Check it out, Episode 88: The Hubble Space Telescope.

Sources:
http://en.wikipedia.org/wiki/Cosmology#cite_note-5
http://en.wikipedia.org/wiki/En%C3%BBma_Eli%C5%A1
http://en.wikipedia.org/wiki/Timeline_of_cosmology
http://www.newscientist.com/article/dn9988-instant-expert-cosmology.html
http://en.wikipedia.org/wiki/Geocentric_model
http://en.wikipedia.org/wiki/Heliocentrism
http://en.wikipedia.org/wiki/Red_shift

Posted on by Tega Jessa

What Galaxy Do We Live In?

Artist's impression of The Milky Way Galaxy. Based on current estimates and exoplanet data, it is believed that there could be tens of billions of habitable planets out there. Credit: NASA

If you are not an astronomy enthusiast you not have thought much about what galaxy do we live in. So depending on that the answer may surprise you. If you know anything about galaxies you know that they are groupings of stars that number in the hundreds of billions. The most famous is the Milky Way. It is from this galaxy that we even have the term. The simple point is that the Earth is part of the Milky Way even though if we see it in the sky it looks like we are observing it from the outside. Why is that? To understand you need to know exactly where we live in neighborhood of the Milky Way Galaxy.

As we are part of the solar system Earth pretty much follows the path of the sun as it goes through its own orbit around the galaxy. The Milky Way is a spiral galaxy type so it has arms sort of like an octopus. The Sun is located near the outward tip of the Sagittarius arm of the Milky Way. This makes Earth about 28,000 light years from the galactic core of our home galaxy.

The Solar System also has a galactic year that it follows. It takes around 200 million to 250 million years for the solar system to orbit the Sun. Another indicator of our position is where the galactic equator. While our star system is considered to be on the outskirts of the Milky Way this is only an estimate. It is believed that the Milky Way is larger than first estimated. There is also suspicion that our galaxy is in the process of absorbing other smaller galaxies. However, there is not enough empirical evidence available to support the claim.

So what would be so important about knowing what part of the galaxy we live in? One reason is space exploration. Some time in the future mankind may find a way to achieve faster than light space travel. This can provide a new set of challenges for engineers and astronomers to tackle. For example how would an astronaut keep from getting lost in space? Detailed mapping and computer programming in the future could help galactic wayfarers know where they are going and more importantly how to get home.

The other reason is that it never hurts to know our place in the scheme of things. Just thinking of the challenge of finding earth if we were so far way helps us to understand how truly vast the universe is.

We have written many articles about the Milky Way galaxy for Universe Today. Here are some facts about the Milky Way, and here’s an article about the closest galaxy to the Milky Way.

If you’d like more info on galaxies, check out Hubblesite’s News Releases on Galaxies, and here’s NASA’s Science Page on Galaxies.

We’ve also recorded an episode of Astronomy Cast about galaxies. Listen here, Episode 97: Galaxies.

Sources: SEDS, Daily Galaxy

Posted on by Nancy Atkinson

How Common are Solar Systems Like Ours?

Solar system montage. Credit: NASA

On the whole, we’d like to think we’re special, but we also hope we aren’t alone in the Universe. Astronomers have been trying to figure out just how common solar systems like ours are across the cosmos, and during one moment of epiphany one scientist figured out how to make the calculations. It took a worldwide collaboration of astronomers to do the work, but they concluded that about 10 – 15 percent of stars in the universe host systems of planets like our own, with several gas giant planets in the outer part of the solar system.

“Now we know our place in the universe,” said Ohio State University astronomer Scott Gaudi. “Solar systems like our own are not rare, but we’re not in the majority, either.”

The find comes from a collaboration headquartered at Ohio State called the Microlensing Follow-Up Network (MicroFUN), which searches the sky for extrasolar planets.

MicroFUN astronomers use gravitational microlensing — which occurs when one star happens to cross in front of another as seen from Earth. The nearer star magnifies the light from the more distant star like a lens. If planets are orbiting the lens star, they boost the magnification briefly as they pass by.

During his talk at the American Astronomical Society meeting in Washington, DC today, Gaudi said, “Planetary microlensing basically is looking for planets you can’t see around stars you can’t see.”

This method is especially good at detecting giant planets in the outer reaches of solar systems — planets analogous to our own Jupiter.

This latest MicroFUN result is the culmination of 10 years’ work — and one sudden epiphany, explained Gaudi and Andrew Gould, professor of astronomy at Ohio State.

Ten years ago, Gaudi wrote his doctoral thesis on a method for calculating the likelihood that extrasolar planets exist. At the time, he concluded that less than 45 percent of stars could harbor a configuration similar to our own solar system.

Then, in December of 2009, Gould was examining a newly discovered planet with Cheongho Han of the Institute for Astrophysics at Chungbuk National University in Korea. The two were reviewing the range of properties among extrasolar planets discovered so far, when Gould saw a pattern.

“Basically, I realized that the answer was in Scott’s thesis from 10 years ago,” Gould said. “Using the last four years of MicroFUN data, we could add a few robust assumptions to his calculations, and we could now say how common planet systems are in the universe.”

The find boils down to a statistical analysis: in the last four years, the MicroFUN survey has discovered only one solar system like our own — a system with two gas giants resembling Jupiter and Saturn, which astronomers discovered in 2006 and reported in the journal Science in 2008.

“We’ve only found this one system, and we should have found about eight by now — if every star had a solar system like Earth’s,” Gaudi said.

The slow rate of discovery makes sense if only a small number of systems — around 10 percent — are like ours, they determined.

“While it is true that this initial determination is based on just one solar system and our final number could change a lot, this study shows that we can begin to make this measurement with the experiments we are doing today,” Gaudi added.

As to the possibility of life as we know it existing elsewhere in the universe, scientists will now be able to make a rough guess based on how many solar systems are like our own.

Our solar system may be a minority, but Gould said that the outcome of the study is actually positive.

“With billions of stars out there, even narrowing the odds to 10 percent leaves a few hundred million systems that might be like ours,” he said.

At the AAS conference today, Gaudi was awarded the Helen B. Warner Prize for Astronomy.

Source: AAS, EurekAlert

Posted on by John Carl Villanueva

Structure of the Universe

Galaxy cluster Abell 85, seen by Chandra, left, and a model of the growth of cosmic structure when the Universe was 0.9 billion, 3.2 billion and 13.7 billion years old (now). Credit: Chandra

[/caption]The large-scale structure of the Universe is made up of voids and filaments, that can be broken down into superclusters, clusters, galaxy groups, and subsequently into galaxies. At a relatively smaller scale, we know that galaxies are made up of stars and their constituents, our own Solar System being one of them.

By understanding the hierarchical structure of things, we are able to gain a clearer visualization of the roles each individual component plays and how they fit into the larger picture. For example, if we go down to the world of the very small, we know that molecules can be chopped down into atoms; atoms into protons, electrons, and neutrons; then the protons and neutrons into quarks and so on.

But what about the very large? What is the large-scale structure of the universe? What exactly are superclusters and filaments and voids? Let’s start by looking at galaxy groupings and move on to even larger structures.

Although there are some galaxies that are found to stray away by their lonesome, most of them are actually bundled into groups and clusters. Groups are smaller, usually made up of less than 50 galaxies and can have diameters up to 6 million light-years. In fact, the group in which our Milky Way is a member of is made up of only a little over 40 galaxies.

Generally speaking, clusters are bunches of 50 to 1,000 galaxies that can have diameters of up to 2-10 megaparsecs. One very peculiar property of clusters is that the velocities of their galaxies are supposed to be too high for gravity alone to keep them bunched together … and yet they are.

The idea that dark matter exists starts at this scale of structure. Dark matter is believed to provide the gravitational force that keeps them all bunched up.

A great number of groups, clusters and individual galaxies can come together to form the next larger structure – superclusters. Superclusters are among the largest structures ever to be discovered in the universe.

The largest single structure to be identified is the Sloan Great Wall, a vast sheet of galaxies that span a length of 500 million light-years, a width of 200 million light-years and a thickness of only 15 million light-years.

Due to the limitations of today’s measuring devices, there is a maximum level to which we can zoom out. At that level, we see a universe made up of mainly two components. There are the threadlike structures known as filaments that are made up of isolated galaxies, groups, clusters and superclusters. And then there are vast empty bubbles of empty space called voids.

You can read more about structure of the universe here in Universe Today. Want to read about the cosmic void: could we be in the middle of it? We’ve also written about probing the large scale structure of the universe.

There’s more about it at NASA. Here are a couple of sources there:

Here are two episodes at Astronomy Cast that you might want to check out as well:

Sources: NASA WMAP, NASA: Sheets and Voids

Posted on by John Carl Villanueva

What is the Big Freeze?

Dark, cold stars from the young Universe could still be here today (University of Utah)

[/caption]The Big Freeze, which is also known as the Heat Death, is one of the possible scenarios predicted by scientists in which the Universe may end. It is a direct consequence of an ever expanding universe. The most telling evidences, such as those that indicate an increasing rate of expansion in regions farthest from us, support this theory. As such, it is the most widely accepted model pertaining to our universe’s ultimate fate.

The term Heat Death comes from the idea that, in an isolated system (the Universe being a very big example), the entropy will continuously increase until it reaches a maximum value. The moment that happens, heat in the system will be evenly distributed, allowing no room for usable energy (or heat) to exist – hence the term ‘heat death’. That means, mechanical motion within the system will no longer be possible.

This kind of ending is a stark contrast to what other scientists believe will be the Universe’s alternative ultimate fate, known as the Big Crunch. The Big Crunch, if it does happen, will be characterized by a collapse of unimaginably gargantuan proportions and will eventually culminate into an immensely massive black hole. The Big Freeze, on the other hand, will happen with less fanfare since everything will wind down to a cold silent halt.

To determine which ending is most possible, scientists need to gather data regarding the density, composition, and even the shape of the Universe.

For example, if the density is found to be lower than what is known as the critical density, then a continuous expansion will ensue. If the density is equal to the critical density, then the Universe will expand forever but at a decreasing rate. Finally, if the density is found to be greater than the critical density, the Universe will eventually stop expanding and then collapse.

It is therefore clear that, for a Big Freeze to occur, the density must be less than the critical density.

Accurate measurements made by the WMAP (Wilkinson Microwave Anisotropy Probe), which picks up cosmic microwave background radiation (CMBR), indicate a density that is much less than the critical density. This is very consistent with observations at the outer regions of the Universe; that being, increasing outward velocities of galaxies as they are further from us.

Through these observations as well as the density measurements, more scientists are inclined to believe that the most possible ending is that of a Big Freeze.

Articles on the big freeze are so hot. It’s a good thing we’ve got a nice collection of them here in Universe Today. Here are two of them:

Here are links from NASA about the big freeze:

Tired eyes? Let your ears help you learn for a change. Here are some episodes from Astronomy Cast that just might suit your taste:

Sources:
http://burro.astr.cwru.edu/stu/advanced/cosmos_death.html
http://map.gsfc.nasa.gov/universe/uni_fate.html

Posted on by John Carl Villanueva

Center of the Universe

Where is the center of the Universe? One of the confusing aspects of the whole Big Bang idea is the notion that the Universe doesn’t have a center. You see, if we associate the Big Bang with just about any typical explosion, then we can be tempted to pinpoint the source of the explosion to be the center.

For example, if a firecracker explodes and we take a snapshot of it, then the outermost debris would mark the boundaries of the whole explosion. Looking at the directions of each debris, whether outermost or not, would give us an idea as to where the explosion first started and, subsequently, the center.

Furthermore, if there was a point of origin (the center) of the Big Bang similar to typical explosions, then that point and all regions near it would be comparatively warmer than all others. That is, as you move further from the center of a typical explosion, you would expect to measure cooler temperatures.

However, when scientists point their detectors to all directions, the readings they obtain indicate that the Universe, in general, is homogeneous. No large region is relatively warmer than the rest. Of course, each star is hotter than the regions away from it.

But if we look at many galaxies, and thus including the stars that comprise them, a homogeneous overall picture is painted. If that were so, then that center or point of origin of the explosion cannot exist.

The favorite analogy used by lecturers to simplify the concept of a universe having no center is that of the behavior of dots on the surface of an expanding balloon; for as we know, the Universe is expanding. If we imagine the dots to be galaxies, we can visualize the Universe’s expansion by observing how the dots are brought away from one another as air is slowly blown into the balloon.

For us to get a near accurate analogy, it is important that the observation be limited to the surface alone. If we try to interpret the expansion as being manifested by the whole balloon, we will be tempted into interpreting the geometric center of the balloon as the center of the expanding Universe.

Going back, if we just focus on the surface, you’ll notice that each and every dot will drift farther away from adjacent ones and that no single dot will appear as the center. Also, if you picture yourself as an ant at the center of a single dot, all the other dots will move away from you as if you were the center, just like in our universe.

We’ve got a few articles that touch on the center of the universe here in Universe Today. Here are two of them:

NASA also has some more:

Tired eyes? Let your ears help you learn for a change. Here are some episodes from Astronomy Cast that just might suit your taste:

Source: NASA Spitzer

Posted on by Fraser Cain

A Portal to Another Universe?

In episode 56 of Astronomy Cast, I noted that hoping that a black hole will lead to another dimension is sort of like a frog thinking that a blender will take him to another realm.

Astronomy Cast listener Isaac Windham animated the sequence, just to really drive the point home…

And here’s the transcript from the show, so you’ll all get the reference. Thanks Isaac!

Fraser: Why do people think we might live in a black hole? That seems kind of crazy to me.

Pamela: It’s a lot of science fiction. There’s this idea in science fiction that you can fly into a black hole and emerge in a completely different part of our universe, in an alternate universe… and so from these fiction writings, the idea has gotten into the zeitgeist that you fly into a black hole and you fly into a different universe – which means a universe can be inside of a black hole.

The problem is real black holes just lead to death.

Fraser: I guess that’s the question – it’s like a frog asking if I hop into that blender, will it lead me to another universe?

Pamela: Exactly

Fraser: No, no it won’t – a universe of pain.

Pamela: It will lead to death, and yeah – where death leads to is a personal question not based in facts and not addressable in this show.

Fraser: Right, so it’s almost like it’s become a kind of philosophical question and it goes back to that extra-dimensional conversation we had in a well-received episode we did back in the day. I guess it’s kind of like it’s different – could it be so different that it’s not really a devastating matter crusher? Could it be a bold new universe we could explore? (Says the frog hopping into his blender.