Posted on by Steve Nerlich

Astronomy Without A Telescope – Home Made Quark-Gluon Soup

The most powerful operational heavy-ion collider in the world, the Relativistic Heavy Ion Collider (RHIC) recently recorded the highest ever temperature created in an Earth-based laboratory of 4 trillion Kelvin. Achieved at the almost speed of light collision of gold ions, this resulted in the temporary existence of quark-gluon soup – something first seen at about ten to the power of minus twelve of the first second after the big bang.

And sure, the Large Hadron Collider (LHC) may one day soon be the most powerful heavy-ion collider in the world (although it will spend most of its time investigating proton to proton collisions). And sure, maybe it’s going to generate a spectacular 574 TeV when it collides its first lead ions. But you have to win the game before you get the trophy.

To give credit where it’s due, the LHC is already the most powerful particle collider in the world – having achieved proton collision energies of 2.36 TeV in late 2009. And it should eventually achieve proton collision energies of 14 TeV, but that will come well after its scheduled maintenance shutdown in 2012, ahead of achieving its full design capabilities from 2013. It has already circulated a beam of lead ions – but we are yet to see an LHC heavy ion collision take place.

So, for the moment it’s still RHIC putting out all the fun stuff. In early March 2010, it produced the largest ever negatively charged nucleus – which is anti-matter, since you can only build matter nuclei from protons and/or neutrons which will only ever have a positive or a neutral charge.

This antimatter nucleus carried an anti-strange quark – which is crying out for a new name… mundane quark, conventional quark? And since the only matter nuclei containing strange quarks are hypernuclei, RHIC in fact created an antihypernucleus. Wonderful.

Then there’s the whole quark-gluon soup story. Early experiments at RHIC reveal that this superhot plasma behaves like a liquid with a very low viscosity— and may be what the universe was made of in its very early moments.  There was some expectation that melted protons and neutrons would be so hot that surely you would get a gas – but like the early universe, with everything condensed into a tiny volume, you get a super-heated liquid (i.e. soup).

An aerial view of the Relativistic Heavy Ion Collider (RHIC) in Upton, NY. The Alternating Gradient Synchrotron (AGS) built in the 1960s now works as a pre-accelerating injector for the larger RHIC.

The LHC hopes to deliver the Higgs, maybe a dark matter particle and certainly anti-matter and micro black holes by the nano-spoonful. And after that, there’s talk of building the Very Large Hadron Collider, which promises to be bigger, more powerful and more expensive.

But if that project doesn’t fly, we can still ramp up the existing colliders. Ramping up a particle collider is an issue of luminosity, where the desired outcome is a more concentrated and focused particle beam – with an increased energy density achieved by cramming more particles into a cross section of the beam you are sending around the particle accelerator. Both RHIC and the LHC have plans to undertake an upgrade to achieve an increase of their respective luminosities by up to a factor of 10. If successful, we can look forward to RHIC II and the Super Large Hadron Collider coming online sometime after 2020. Fun.

Posted on by Jean Tate

Big Bang Timeline

A fraction of a second after the big bang, the universe underwent inflation - but what does that mean? credit: NASA/WMAP
Time line of the Universe (Credit: NASA/WMAP Science Team)

The Big Bang timeline is basically just a list of relative times at which the major events in the history of the universe occurred, per the collection of theories, models, and hypotheses which together form what is called the Big Bang theory.

The start – when time began, when t = 0 – is not actually part of the Big Bang timeline (!), contrary to popular belief. That’s because the two theories of physics which are at the heart of the Big Bang theory – General Relativity (GR) and the Standard Model (of particle physics; SM for short) – are mutually incompatible, and that incompatibility becomes so intolerable that saying anything about what happened in the first Planck second (approx 10-43 second) is meaningless.

In fact, the closer to the Planck regime – when GR and the SM are utterly incompatible – the less reliable are our descriptions … but the relative times are nonetheless pretty good.

Actually, that’s not quite true … what is relatively certain are temperatures; forces, matter, and radiation interact in very distinct ways, depending on the temperature (and pressure, or density), but converting from temperature back to time depends on various parameters which are not so well pinned down. However, once the average mass-energy density of the universe, today, is estimated, the clock can be wound back with some confidence (it’s ~six hydrogen atoms per cubic meter, or about 7 x 10-27 kg/m3).

Around 10-35 seconds leptons and baryons were created (the strong force became a distinct force), and inflation caused the universe to expand so much that the part which later became our observable universe was both flat (no curvature, in the GR sense) and incredibly smooth (with only tiny variations in density due to quantum effects).

At around 10-11 seconds the electromagnetic and weak force became distinct.

And by about a microsecond the universe underwent another phase change … it was no longer a quark-gluon plasma, but hadrons formed (protons and neutrons).

When t = 1 second (more or less), nuclear reactions produced light nuclides, such as deuterium and helium-3 (before this time the universe was too hot for them to form) – Big Bang nucleosynthesis.

The earliest part of the universe we can still see, directly, happened when the electrons and protons (and other nuclei) combined to form hydrogen atoms; this is the recombination era, and we see it today as the cosmic microwave background … and gravity took over as the dominant force (before this it was electromagnetism – the universe was ‘radiation dominated’ – and before that, at the time of nucleosynthesis, the strong and weak forces ruled).

The rest, as they say, is history … the Dark Ages (during which the first stars were formed), the era of recombination (when stars and quasars ionized the diffuse hydrogen), galaxy formation, … and then about 13.4 billion years later we observed the skies and worked out the timeline!

There’s a lot of good material on the web on the Big Bang timeline; here are some: John Baez (who’s always worth reading) has a brief timeline, in terms of temperature; there’s a more extensive one from the University of Wisconsin-Madison, and perhaps the best, A Brief History of the Universe (University of Cambridge).

Want to explore more? Here are some of the many Universe Today articles on the Big Bang timeline: Cosmologists Look Back to Cosmic Dawn, A Star as Old as the Universe, and Book Review: The Mystery of the Mission Antimatter.

Astronomy Cast has several episodes for you to explore, to learn more about the Big Bang timeline; here are a few: The Big Bang and Cosmic Microwave Background, Inflation, and this 2009 Questions Show.

Sources:
http://en.wikipedia.org/wiki/Timeline_of_the_Big_Bang
http://www.damtp.cam.ac.uk/research/gr/public/bb_history.html

Posted on by John Carl Villanueva

What is the Oscillating Universe Theory?

The Oscillating Universe Theory is a cosmological model that combines both the Big Bang and the Big Crunch as part of a cyclical event. That is, if this theory holds true, then the Universe in which we live in exists between a Big Bang and a Big Crunch.

In other words, our universe can be the first of a possible series of universes or it can be the nth universe in the series.

As we know, in the Big Bang Theory, the Universe is believed to be expanding from a very hot, very dense, and very small entity. In fact, if we extrapolate back to the moment of the Big Bang, we are able to reach a point of singularity characterized by infinitely high energy and density, as well as zero volume.

This description would only mean one thing – all the laws of physics will be thrown out of the window. This is understandably unacceptable to physicists. To make matters worse, some cosmologists even believe that the Universe will eventually reach a maximum point of expansion and that once this happens, it will then collapse into itself.

This will essentially lead to the same conditions as when we extrapolate back to the moment of the Big Bang. To remedy this dilemma, some scientists are proposing that perhaps the Universe will not reach the point of singularity after all.

Instead, because of repulsive forces brought about by quantum effects of gravity, the Universe will bounce back to an expanding one. An expansion (Big Bang) following a collapse (Big Crunch) such as this is aptly called a Big Bounce. The bounce marks the end of the previous universe and the beginning of the next.

The probability of a Big Bounce, or even a Big Crunch for that matter, is however becoming negligible. The most recent measurements of the CMBR or cosmic microwave background radiation shows that the Universe will continue on expanding and will most likely end in what is known as a Big Freeze or Heat Death.

CMBR readings are currently being gathered by a very accurate measuring device known as the WMAP or Wilkinson Microwave Anisotropy Probe. It is the same device that has measured with sharp precision the age of our universe. It is therefore highly unlikely that future findings will deviate largely from what has been discovered regarding the Universe’s expansion now.

There is however one mysterious entity whose deeper understanding of may change the possibilities. This entity, known as dark energy, is believed to be responsible for pushing the galaxies farther apart and subsequently the universe’s accelerated expansion. Unless its actual properties are very dissimilar from what it is showing now, we may have to shelve the Oscillating Universe Theory.

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

Physics World 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:

Sources:
PBS.org
Wikipedia

Posted on by John Carl Villanueva

The Big Crunch: The End of Our Universe?

The Big Crunch is one of the scenarios predicted by scientists in which the Universe may end. Just like many others, it is based on Einstein’s Theory of General Relativity. That is, if the Big Bang describes how the Universe most possibly began, the Big Crunch describes how it will end as a consequence of that beginning.

It tells us that the Universe’s expansion, which is due to the Big Bang, will not continue forever. Instead, at a certain point in time, it will stop expanding and collapse into itself, pulling everything with it until it eventually turns into the biggest black hole ever. Well, we all know how everything is squeezed when in that hole. Hence the name Big Crunch.

For scientists to predict with certainty the possibility of a Big Crunch, they will have to determine certain properties of the Universe. One of them is its density. It is believed that if the density is larger than a certain value, known as the critical density, an eventual collapse is highly possible.

You see, initially, scientists believed that there were only two factors that greatly influenced this expansion: the gravitational force of attraction between all the galaxies (which is proportional to the density) and their outward momentum due to the Big Bang.

Now, just like any body that goes against gravity, e.g. when you throw something up, that body will eventually give in and come back down for as long as there is no other force pushing it up.

Thus, that the gravitational forces will win in the end, once seemed like a logical prediction. But that was until scientists discovered that the Universe was actually increasing its rate of expansion at regions farthest from us.

To explain this phenomena, scientists had to assume the presence of an unknown entity, which they dubbed ‘dark energy’. It is widely believed that this entity is pushing all galaxies farther apart. With dark energy, and what little is known about it, in the picture, there seems to be little room for the possibility of a Big Crunch.

Right now, measurements made by NASA’s Chandra X-ray observatory indicate that the strength of dark energy in the University is constant. Just for added information, an increasing dark energy strength would have supported the possibility of a Big Rip, another universe ending that predicted everything (including atoms) to be ripped apart.

Even with an unchanging dark energy strength, an ever expanding universe is still the most likely scenario. So unless data that contradicts these properties are collected, the Big Crunch will have to remain as a less favored theory.

Articles on the big crunch 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 crunch:

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:
NASA
Wikipedia

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 John Carl Villanueva

How Many Atoms Are There in the Universe?

A billion years after the big bang, hydrogen atoms were mysteriously torn apart into a soup of ions. Credit: NASA/ESA/A. Felid (STScI)).

It’s no secret that the universe is an extremely vast place. That which we can observe (aka. “the known Universe”) is estimated to span roughly  93 billion light years. That’s a pretty impressive number, especially when you consider its only what we’ve observed so far. And given the sheer volume of that space, one would expect that the amount of matter contained within would be similarly impressive.

But interestingly enough, it is when you look at that matter on the smallest of scales that the numbers become the most mind-boggling. For example, it is believed that between 120 to 300 sextillion (that’s 1.2 x 10²³ to 3.0 x 10²³) stars exist within our observable universe. But looking closer, at the atomic scale, the numbers get even more inconceivable.

At this level, it is estimated that the there are between 1078 to 1082 atoms in the known, observable universe. In layman’s terms, that works out to between ten quadrillion vigintillion and one-hundred thousand quadrillion vigintillion atoms.

And yet, those numbers don’t accurately reflect how much matter the universe may truly house. As stated already, this estimate accounts only for the observable universe which reaches 46 billion light years in any direction, and is based on where the expansion of space has taken the most distant objects observed.

The history of theA billion years after the big bang, hydrogen atoms were mysteriously torn apart into a soup of ions.universe starting the with the Big Bang. Image credit: grandunificationtheory.com
The history of the universe starting the with the Big Bang. Image credit: grandunificationtheory.com

While a German supercomputer recently ran a simulation and estimated that around 500 billion galaxies exist within range of observation, a more conservative estimate places the number at around 300 billion. Since the number of stars in a galaxy can run up to 400 billion, then the total number of stars may very well be around 1.2×1023  – or just over 100 sextillion.

On average, each star can weigh about 1035 grams. Thus, the total mass would be about 1058 grams (that’s 1.0 x 1052 metric tons). Since each gram of matter is known to have about 1024 protons, or about the same number of hydrogen atoms (since one hydrogen atom has only one proton), then the total number of hydrogen atoms would be roughly 1086 – aka. one-hundred thousand quadrillion vigintillion.

Within this observable universe, this matter is spread homogeneously throughout space, at least when averaged over distances longer than 300 million light-years. On smaller scales, however, matter is observed to form into the clumps of hierarchically-organized luminous matter that we are all familiar with.

In short, most atoms are condensed into stars, most stars are condensed into galaxies, most galaxies into clusters, most clusters into superclusters and, finally, into the largest-scale structures like the Great Wall of galaxies (aka. the Sloan Great Wall). On a smaller scale, these clumps are permeated by clouds of dust particles, gas clouds, asteroids, and other small clumps of stellar matter.

Representation of the timeline of the universe over 13.7 billion years, and the expansion in the universe that followed. Credit: NASA/WMAP Science Team.
Representation of the timeline of the universe over 13.7 billion years, and the expansion in the universe that followed. Credit: NASA/WMAP Science Team.

The observable matter of the Universe is also spread isotropically; meaning that no direction of observation seems different from any other and each region of the sky has roughly the same content. The Universe is also bathed in a wave of highly isotropic microwave radiation that corresponds to a thermal equilibrium of roughly 2.725 kelvin (just above Absolute Zero).

The hypothesis that the large-scale universe is homogeneous and isotropic is known as the cosmological principle. This states that physical laws act uniformly throughout the universe and should, therefore, produce no observable irregularities in the large scale structure. This theory has been backed up by astronomical observations which have helped to chart the evolution of the structure of the universe since it was initially laid down by the Big Bang.

The current consensus amongst scientists is that the vast majority of matter was created in this event, and that the expansion of the Universe since has not added new matter to the equation. Rather, it is believed that what has been taking place for the past 13.7 billion years has simply been an expansion or dispersion of the masses that were initially created. That is, no amount of matter that wasn’t there in the beginning has been added during this expansion.

However, Einstein’s  equivalence of mass and energy presents a slight complication to this theory. This is a consequence arising out of Special Relativity, in which the addition of energy to an object increases its mass incrementally. Between all the fusions and fissions, atoms are regularly converted from particles to energies and back again.

Atom density is greater at left (the beginning of the experiment) than 80 milliseconds after the simulated Big Bang. Credit: Chen-Lung Hung
Atom density is greater at left (the beginning of the experiment) than 80 milliseconds after the simulated Big Bang. Credit: Chen-Lung Hung

Nevertheless, observed on a large-scale, the overall matter density of the universe remains the same over time. The present density of the observable universe is estimated to be very low – roughly 9.9 × 10-30 grams per cubic centimeter. This mass-energy appears to consist of 68.3% dark energy, 26.8% dark matter and just 4.9% ordinary (luminous) matter. Thus the density of atoms is on the order of a single hydrogen atom for every four cubic meters of volume.

The properties of dark energy and dark matter are largely unknown, and could be uniformly distributed or organized in clumps like normal matter. However, it is believed that dark matter gravitates as ordinary matter does, and thus works to slow the expansion of the Universe. By contrast, dark energy accelerates its expansion.

Once again, this number is just a rough estimate. When used to estimate the total mass of the Universe, it often falls short of what other estimates predict. And in the end, what we see is just a smaller fraction of the whole.

We’ve got a many articles that are related to the amount of matter in the Universe here in Universe Today, like How Many Galaxies in the Universe, and How Many Stars are in the Milky Way?

NASA also has the following articles on the universe, like How many galaxies are there? and this article on the Stars in Our Galaxy.

We also have podcast episodes from Astronomy Cast on the subject of Galaxies and Variable Stars.

Posted on by Fraser Cain

Why are Distant Galaxies Moving Away Faster?

Question: Why are more distant galaxies moving away faster?

Answer: As you know, the Universe is expanding after the Big Bang. That means that every part of the Universe was once crammed into a tiny spot smaller than a grain of sand. Then it began expanding, and here we are, 13.7 billion years later with a growing Universe.

The expansive force of dark energy is actually accelerating the expansion even faster. But we won’t bring that in to make things even more complex.

As we look out into the Universe, we see galaxies moving away from us faster and faster. The more distant a galaxy is, the more quickly it’s moving away.

To understand why this is happening, go and get a balloon (or blow one up in your mind). Once you’ve got it blown up a little, draw a bunch of dots on the surface of the balloon; some close and others much further away. Then blow up the balloon more and watch how the dots expand away from each other.

From the perspective of any one dot on the surface of the balloon, the nearby dots aren’t expanding away too quickly, maybe just a few centimeters. But the dots on the other side of the balloon are quite far away. It took the same amount of time for all the dots to change their positions, so the more distant dots appeared to be moving faster.

That’s how it works with the Universe. Because space itself is expanding, the more further a galaxy is, the faster it seems to be receding.

Thanks to Cassandra for the question.

Posted on by Fraser Cain

How Can Galaxies Recede Faster than the Speed of Light?

Question: How Can Galaxies Move Away Faster Than Speed of Light?

Answer: Einstein’s Theory of Relativity says that the speed of light – 300,000 km/s – is the maximum speed that anything can travel in the Universe. It requires more and more energy to approach the speed of light. You could use up all the energy in the Universe and still not be traveling at light speed.

As you know, most of the galaxies in the Universe are expanding away from us because of the Big Bang, and the subsequent effects of dark energy, which is providing an additional accelerating force on the expansion of the Universe.

Galaxies, like our own Milky Way are carried along by the expansion of the Universe, and will move apart from every other galaxy, unless they’re close enough to hold together with gravity.

As you look at galaxies further and further away, they appear to be moving faster and faster away from us. And it is possible that they could eventually appear to be moving away from us faster than light. At that point, light leaving the distant galaxy would never reach us.

When that happens, the distant galaxy would just fade away as the last of the photons reached Earth, and then we would never know it was ever there.

This sounds like it breaks Einstein’s theories, but it doesn’t. The galaxies themselves aren’t actually moving very quickly through space, it’s the space itself which is expanding away, and the galaxy is being carried along with it. As long as the galaxy doesn’t try to move quickly through space, no physical laws are broken.

One sad side effect of this expansion is that most of the galaxies will have receded over this horizon in about 3 trillion years, and future cosmologists will never know there’s a great big Universe out there.

You can read more about this in an article I did called the End of Everything.