Space Shuttle Atlantis on the launchpad. Credit: Mike Deep for Universe Today.
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It was the ultimate experience for a space enthusiast. Universe Today photographer Michael Deep had the opportunity to get up close and personal with the last shuttle that will ever sit on a launchpad and head to space. Enjoy some unique views of space shuttle Atlantis before she goes down into history as the final shuttle to launch to space.
And stay tuned all week for great photos and articles to chronicle the final shuttle launch: Universe Today photographers Alan Walters, Mike Deep, and David Gonzales as well as writers Ken Kremer and Jason Rhian are on location at Kennedy Space Center to provide full coverage.
Sunrise at launchpad 39A. Credit: Mike Deep for Universe Today.A view of Atlantis from the gantry. Credit: Mike Deep for Universe Today.A view of the walkway to enter the shuttle. Credit: Mike Deep for Universe Today.Atlantis on the launchpad. Credit: Mike Deep for Universe TodayUnique view of shuttle Atlantis on the pad. Credit: Mike Deep for Universe Today.The shuttle's SRBs get the stack off the ground. Credit: Mike Deep for Universe TodayThe view from the top of launchpad 39A at KSC. Credit: Mike Deep for Universe Today.Atlantis. Credit: Mike Deep for Universe Today. Looking down at Atlantis from the gantry. Credit: Mike Deep for Universe Today. A wide-angle view of Atlantis on the launchpad. Credit: Mike Deep for Universe Today.
The final Shuttle Crew jets into the Kennedy Space Center on Independence Day, 2011. From Left: Shuttle Commander Chris Ferguson, Pilot Doug Hurley and Mission Specialists Sandy Magnus and Rex Walheim. Credit: Ken Kremer
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The four astronauts who will fly the Grand Finale of NASA’s space shuttle program arrived at the Florida launch site on Independence Day on a wave of T-38 training jets. The veteran crew flew into the Kennedy Space Center (KSC) from Ellington Field in Houston, Texas and touched down at the shuttle landing strip at about 2:30 p.m. EDT.
Blast off of Space Shuttle Atlantis on the STS-135 mission is slated for July 8 at 11.26 a.m. with Shuttle Commander Chris Ferguson at the helm. He is joined by Pilot Doug Hurley and Mission Specialists Sandy Magnus and Rex Walheim.
Upon landing in the sweltering Florida heat, the astronauts were welcomed by Space Shuttle Launch Director Mike Leinbach as well as other NASA/KSC officials and a large crowd of media. Many waved US flags in honor of the July 4th Independence Day holiday.
Shuttle Commander Chris Ferguson addresses the media about the STS-135 mission. Credit: Ken Kremer
“I think I speak for the whole crew in that we are delighted to be here after a very arduous nine month training flow and we’re thrilled to finally be here in Florida for launch week,” said Ferguson. “This is a day that’s decidedly American, a day where we kind of reflect on our independence and all the wonderful things that we really have as part of being the United States of America. I think it’s wonderful you’ve all come out to join us.”
“We have a very event-filled mission ahead of us, we have 12 days, we’ll be very, very busy,” Ferguson added. “When it’s all over, we’ll be very proud to put the right-hand bookend on the space shuttle program.”
The quartet will spend the next few days completing final prelaunch training to prepare for their planned 12 day flight bound for the International Space Station.
The primary cargo is the Raffaello Multipurpose Logistics module built in Italy and jam packed with some five tons of spare parts, science gear, food, water, clothing and more that will be transferred to the station by the station and shuttle crews and are absolutely essential to keep the orbiting outpost operating over the next year.
About 2000 journalists and photographers are expected to cover Atlantis’s launch, the largest media gathering for a shuttle launch since the Return to Flight in 2005 – that’s about twice the media here for the last launch of Endeavour in April.
The countdown clock begins ticking at 1 p.m. EDT on Tuesday, July 5
Shuttle Launch Director Mike Leinbach greets Commander Ferguson. Credit: Ken KremerDoug Hurley and Sandy Magnus speak to reporters at the shuttle landing strip. Credit: Ken KremerSTS-135 crew jets to Florida on T-38 training jets for planned July 8 blastoff. Shuttle Commander Chris Ferguson flew this jet accompanied by Sandy Magnus. Credit: Ken KremerSTS 135 crew arrives in Florida at the Shuttle Landing Facility. Credit: Ken Kremer
Supernova 1994D. The supernova is the bright point in the lower-left. It is a type Ia thermonuclear supernova like those described by Howell. The supernova is on the edge of galaxy NGC 4526, depicted in the center of the image. Credit: NASA/Hubble Space Telescope
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It’s called a Type Ia supernovae and it shines with the luminosity of a billion suns. For all intents and purposes, once they explode they’re dead… But it ain’t so. They might have a core of ash, but they come back to life by sucking matter from a companion star. Zombies? You bet. Zombie stars… And they can be used to measure dark energy.
Why are Type Ia supernovae findings important? Right now they’re instrumental in helping researchers like Andy Howell, adjunct professor of physics at UCSB and staff scientist at Las Cumbres Observatory Global Telescope Network (LCOGT), take a closer look at the mysteries of dark energy. “We only discovered this about 20 years ago by using Type Ia supernovae, thermonuclear supernovae, as standard or ‘calibrated’ candles,” said Howell. “These stars are tools for measuring dark energy. They’re all about the same brightness, so we can use them to figure out distances in the universe.”
As a rule, white dwarf stars which end their lives as Type Ia supernovae have approximately the same mass. These findings were so regular that they are considered a base rule of physics, but rules are usually made to be broken. In this case there’s a new class of Type Ia supernovae – one that goes beyond the typical mass. These stars that go beyond their limits have scientists confused as to their nature. We know they are part of a binary system… But shouldn’t only the white dwarf be the one to explode?
D. Andrew Howell Credit: Katrina MarcinowskiHowell presented a hypothesis to understand this new class of objects. “One idea is that two white dwarfs could have merged together; the binary system could be two white dwarf stars,” he said. “Then, over time, they spiral into each other and merge. When they merge, they blow up. This may be one way to explain what is going on.” Now astrophysicists utilize Type Ia supernovae to track universal expansion. “What we’ve found is that the universe hasn’t been expanding at the same rate,” said Howell. “And it hasn’t been slowing down as everyone thought it would be, due to gravity. Instead, it has been speeding up. There’s a force that counteracts gravity and we don’t know what it is. We call it dark energy.”
Once upon a time, Albert Einstein introduced the cosmological constant to help justify his theory of relativity, but it only applied to a static state. It didn’t take long before Edwin Hubble corrected him and Einstein later referred to his failure to predict the expansion of the universe as the “biggest blunder” of his life. But it wasn’t. “It turns out that this cosmological constant was actually one of his greatest successes,” said Howell. “This is because it’s what we need now to explain the data.”
We could argue all day about dark energy and its properties, along with whether or not it constitutes three-quarters of our known universe. However, it is Howell’s theory that it just might be a property of space. “Space itself has some energy associated with it,” said Howell. “That’s what the results seem to indicate, that dark energy is distributed everywhere in space. It looks like it’s a property of the vacuum, but we’re not completely sure. We’re trying to figure out how sure are we of that – and if we can improve Type Ia supernovae as standard candles we can make our measurements better.”
Unlike historic supernova observations, today’s technology allows even the backyard astronomer to make discoveries and report them. Take the latest M51 findings for example… It’s not just the eyes of the expert on the skies. Thanks to advances in cameras and equipment, we’re looking further away – and more accurately – than ever before. “Now we have huge digital cameras on our telescopes, and really big telescopes,” said Howell, “We’ve been able to survey large parts of the sky, regularly. We find supernovae daily.”
“The next decade holds real promise of making serious progress in the understanding of nearly every aspect of supernovae Ia, from their explosion physics, to their progenitors, to their use as standard candles,” writes Howell in Nature Communications. “And with this knowledge may come the key to unlocking the darkest secrets of dark energy.”
As we dig through the ditches and burn through the witches… 😉
And if you’re interested in looking back, here’s an archive to all the past Carnivals of Space. If you’ve got a space-related blog, you should really join the carnival. Just email an entry to [email protected], and the next host will link to it. It will help get awareness out there about your writing, help you meet others in the space community – and community is what blogging is all about. And if you really want to help out, sign up to be a host. Send an email to the above address.
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Those who can remember sitting through elementary science class might recall learning that with all matter, light is absorbed and converted into energy. In the case of plants, this process is known as photosynthesis. However, they are by no means the only species or objects that do this. In truth, all objects, living or inorganic are capable of absorbing light. In all cases, absorption depends on the electromagnetic frequency of the light being transmitted (i.e. the color) and the nature of the atoms of the object. If they are complementary, light will be absorbed; if they are not, then the light will be reflected or transmitted. In most cases, these processes occur simultaneously and to varying degrees, since light is usually transmitted at various frequencies. Therefore most objects will selectively absorb light while also transmitting and/or reflecting some of it. Wherever absorption occurs, heat energy is generated.
As already noted, absorption depends upon the state of an objects electrons. All electrons are known to vibrate at specific frequencies, what is commonly known as their natural frequency. When light, in the form of photons, interacts with an atom with the same natural frequency, the electrons of that atom will become excited and set into a natural vibrational motion. During this vibration, the electrons of the atom interact with neighboring atoms in such a way as to convert this vibrational energy into thermal energy. Subsequently, the light energy is not to be seen again, hence why absorption is differentiated from reflection and transmission. And since different atoms and molecules have different natural frequencies of vibration, they will selectively absorb different frequencies of visible light.
By relying on this method, physicists are able to determine the properties and material composition of an object by seeing which frequencies of light it is able to absorb. Whereas some materials are opaque to some wavelengths of light, they transparent to others. Wood, for example, is opaque to all forms of visible light. Glass and water, on the other hand, are opaque to ultraviolet light, but transparent to visible light.
Ultimately, absorption of electromagnetic radiation requires the generation of the opposite field, in other words, the field which has the opposite coefficient in the same mode. A good demonstration of this is color. If a material or matter absorbs light of certain wavelengths (or colors) of the spectrum, an observer will not see these colors in the reflected light. On the other hand if certain wavelengths of colors are reflected from the material, an observer will see them and see the material in those colors. For example, the leaves of green plants contain a pigment called chlorophyll, which absorbs the blue and red colors of the spectrum and reflects the green. Leaves therefore appear green, whereas reflected light often appears to the naked eye to be refracted into several colors of the spectrum (i.e. a rainbow effect).
We have written many articles about the absorption of light for Universe Today. Here’s an article about absorption spectra, and here’s an article about absorption spectroscopy.
The explosion in the sciences that took place in the 17th and 18th centuries revolutionized not only the way we think of our world, but of time and space itself. Much of this is owed to individuals like Sir Isaac Newton, a man whose theories came to form the basis of modern physics. Though much of his theories would later come to be challenged with the discovery of relativity and quantum mechanics, they were nonetheless extremely influential because they gave later generations a framework. It is to him, for example, that we are indebted for the notions of Absolute Time and Absolute Space, and how the two were thought to be separate aspects of objective reality.
In his magnum opus, PhilosophiæNaturalis Principia Mathematica (Mathematical Principles for Natural Philosophy), Newton laid the groundwork for the concept of Absolute Space thusly:
“Absolute space, in its own nature, without regard to anything external, remains always similar and immovable. Relative space is some movable dimension or measure of the absolute spaces; which our senses determine by its position to bodies: and which is vulgarly taken for immovable space … Absolute motion is the translation of a body from one absolute place into another: and relative motion, the translation from one relative place into another.”
In other words, Absolute Space is the study of space as an absolute, unmoving reference point for what inertial systems (i.e. planets and other objects) exist within it. Thus, every object has an absolute state of motion relative to absolute space, so that an object must be either in a state of absolute rest, or moving at some absolute speed.
These views were controversial even in Newton’s own time. However, it was with the advent of modern physics and the Theory of Special Relativity, that much of the basis for Newtonian physics would come to be shattered. In essence, special relativity proposed that time and space are not independent realities but different expressions of the same thing. In this model, time and motion are dependent on the observer and there is no fixed point of reference, only relative forms of motion which are determined by comparing them to other points of reference.
However, it would be fair to say that it was Newton’s own definitions of space and time as independent phenomena that allowed for the development of physics as we know it today. By giving physicists clear definitions to work with and challenge, later generations of scientists like Einstein were able to express clearly how space was not absolute since it itself was always in motion, and how one could not divorce space from time.
We have written many articles about absolute space for Universe Today. Here’s an article about what is space, and here’s an article about how cold space is.
When it comes to measurements, the everyday kind that deal with things like air pressure, tire pressure, blood pressure, etc., there is no such thing as an absolute accuracy. And yet, as with most things, scientists are able to come up with a relatively accurate way of gauging these things by measuring them relative to other things. When it comes to air pressure (say for example, inside a tire), this takes the form of measuring it relative to ambient air temperature, or a perfect vacuum. The latter case, where zero pressure is referred against a total vacuum, is known as Absolute Pressure. The name may seem slightly ironic, but since the comparison is against an environment in which there is no air pressure to speak of.
In the larger context of pressure measurement, Absolute Pressure is part of the “zero reference” trinity. This includes Absolute Pressure (AP), Gauge Pressure, and Differential Pressure. As already noted, AP is zero referenced against a perfect vacuum. This is the method of choice when measuring quantities where absolute values must be determined. Gauge Pressure, on the other hand, is referenced against ambient air pressure, and is used for conventional purposes such as measuring tire and blood pressure. Differential Pressure is quite simply the difference between the two points.
Cases where AP are used include atmospheric pressures readings: where one is trying to determine air pressure (expressed in units of atm’s, where one is equal to 101,325 Pa), Mean Sea Level pressure (the air pressure at sea level; on average: 101.325 kPa), or the boiling point of water (which varies based on elevation and differences in air pressure). Another instance of AP being the method of choice is with the measurement of deep vacuum pressures (aka. outer space) where absolute readings are needed since scientists are dealing with a near-total vacuum. Altimeter pressure is another instance, where air pressure is used to determine the altitude of an aircraft and absolute values are needed to ensure both accuracy and safety.
To produce an absolute pressure sensor, manufacturer will seal a high vacuum behind the sensing diaphragm. If the connection of an absolute pressure transmitter is open to the air, it will read the actual barometric pressure (which is roughly 14.7 PSI). This is different from most gauges, such as those used to measure tire pressure, in that such gauges are calibrated to take into account ambient air pressure (i.e. registering 14.7 PSI as zero).
We have written many articles about absolute pressure for Universe Today. Here’s an article about Boyle’s Law, and here’s an article about air density.
The tour of this Delta IV Medium rocket, was extensive and highlighted how United Launch Alliance sends payloads to orbit. Photo Credit: Alan Walters/awaltersphoto.com
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CAPE CANAVERAL Fla. – Space Launch Complex 37 is where United Launch Alliance (ULA) Delta IV rockets send their payloads into orbit. It is an expansive complex with all the prerequisite requirements to launch rockets as well as birds, alligators and mosquitoes – lots of mosquitoes.
Universe Today was provided with a top to bottom tour of the Mobile Service Tower (MST) that is currently the home of the Delta IV medium rocket that will launch a GPS rocket to orbit on July 14. This structure in and of itself is impressive, standing as tall as a football field is long.
The very top of the Delta IV's payload fairing is visible in this image on Level 9 of the MST. This segment was added on June 27, after the Delta IV launch vehicle had been tested and verified ready for flight. Photo Credit: Alan Walters/awaltersphoto.com
When one reaches the ninth level, the ‘tip of the spear’ juts out from the floor. At the base, just peeking out from the deck below is the U.S. Air Force logo for the Global Positioning Wing. We would have to go down another level to see the remainder of the logo – it was that large.
As we traveled deck by deck, more and more of the rocket became visible. The simple act of taking the stairs or an elevator added a layer of understanding to the sheer size of these vehicles. Photo Credit: Alan Walters/awaltersphoto.com
It is at this level that where the fairing section is mated to the top of the rocket is plainly visible. A Boeing logo is also visible on the rocket’s hull. It turns out that while some of the more specialized missions have large decals produced for them – for missions such as this one (this rocket will carry the GPS 2F-2 satellite) a series of stencils are used.
Old Glory meets us on Level Seven. To the left and right of the rocket are large openings that allow the Delta IV Heavy's triple-body design to fit inside the MST. Photo Credit: Alan Walters/awaltersphoto.com
On some of the lower decks it wasn’t actually the rocket itself that was interesting – but rather what was not there that intrigued us. Two large circular holes are positioned to either side of the Delta IV medium rocket – this is to accommodate the triple-body design of the rocket’s far-larger cousin – the Delta IV Heavy. For now these portals are covered in mesh and blocked off by railings.
The view on Level Six was all about product-placement as ULA's logo was very visible on this deck. Photo Credit: Alan Walters/awaltersphoto.com
Nearer the base we come across products of Utah’s Alliant Techsystems (ATK) – two solid rocket motors are mounted to either side of the Delta IV and will provide the vehicle the extra needed push to get its payload out of Earth’s gravity well.
After descending several stories we were finally moving away from the white "top" section of the rocket. Photo Credit: Alan Walters/awaltersphoto.com
It is sometimes difficult to get experts that work on the machines to translate what they do into language that the general public can understand. It was obvious that the ULA representative that conducted the tour – was well aware of this. Making sure that we had the specific technical names and numbers of what we were looking at – but more accessible means of comprehending the numbers we were given.
A different angle of the previous level shows the Florida coastline stretching out in the distance. Photo Credit: Alan Walters/awaltersphoto.com
“Room with a view”
Alan Walters, a professional photojournalist that has covered the space program for the past few years has a keen eye and suggested on one of the middle levels that I work my way around the rocket to take in the scenery. To say that it takes your breath away does not give the landscape that stretches out in front of you justice. Florida’s Space Coast arches out for miles in front of you. An early-morning storm was blowing into the region the day of the tour – adding to the spectacle.
The Delta IV 4, 2 has two strap-on solid rocket boosters which help carry the rocket and its payload to orbit. Photo Credit: Alan Walters/awaltersphoto.comIf one looks to the right of this picture one can see the famous Cape Canaveral Lighthouse off in the distance. Photo Credit: Alan Walters/awaltersphoto.com
Assembly of NASA’s first Orion Crew Module is complete. Shown here is the first Orion/Multi-Purpose Crew Vehicle (MPCV) being hoisted into position in the Reverberant Acoustic Lab at Lockheed Martin’s Waterton Facility near Denver, Colorado where it will undergo ground tests simulating the harsh environment of deep space. Credit: Lockheed Martin
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Assembly of NASA’s first Orion Crew vehicle that could actually launch to space has been accomplished by prime contractor Lockheed Martin Corporation at the firm’s Waterton space systems facility located near Denver, Colorado, where the spacecraft is slated to begin a severe testing process that will help confirm crew safety.
Orion is NASA’s next generation spacecraft designed to send human crews to low Earth Orbit and beyond to multiple deep space destinations throughout our solar system including the Moon, Mars and Asteroids. Orion was recently recast as the MPCV or Multi Purpose Crew Vehicle in the NASA Authorization Act of 2010.
“The first Orion crew module built to spaceflight specifications is complete,” said Linda Singleton, a spokesperson for Lockheed Martin in an interview.
“Orion will soon be integrated with the launch abort system test article prior to undergoing acoustic, vibration and modal testing in Denver,” Singleton told me. “The testing process will last several months.”
Watch this cool and detailed animation of the testing process to be conducted at the Reverberant Acoustic Lab at Lockheed Martin’s Waterton Facility.
The video also shows how the Orion will be integrated and tested with the Launch Abort System (LAS) that would save the lives of the astronauts on board in the event of a spaceflight emergency.
With the Grand Finale of NASA’s Space Shuttle Program now just days away after the launch of shuttle Atlantis on the STS-135 mission, the US faces a gap with no capability to send humans to space and the International Space Station for a time period extending at least several years.
A replacement vehicle for the retiring shuttle – whether its the Orion or from a commercial provider like SpaceX – can’t come soon enough in order to maintain the viability of the International Space Station.
This Orion vehicle also known as the Ground Test Article, or GTA, will now be subjected to several months of rigorous flight like testing that simulates the harsh environments that astronauts would face during voyages to deep space.
NASA's Orion Multi Purpose Crew Vehicle
The Orion MPVC Multi Purpose Crew Vehicle ground test article (GTA) is shown at the Lockheed Martin Vertical Test Facility in Colorado. The GTA’s heat shield and thermal protection backshell was completed in preparation for environmental testing. Credit: NASA/Lockheed Martin
Thereafter, the Orion crew module will be transported in early 2012 to NASA’s Langley Research Center in Virginia where it will undergo water landing drop tests next year at the new Hydro Impact Basin facility.
“The NASA and Lockheed Martin teams hope to achieve Orion/MPCV initial crewed operations by 2016”, said Singleton. “We are aiming for an initial unmanned orbital test flight in 2013.”
A Delta IV Heavy booster rocket is the most likely candidate for the 2013 Orion orbital flight, but a final decision has not yet been announced by NASA.
Meanwhile, another Orion crew module that was flown during the Pad Abort 1 test (PA-1) in 2010 is now on public display at the Kennedy Space Center Visitor Complex in Florida. The vehicle just arrived after a cross country trek from NASA’s Dryden Flight Research Center in California and making several public outreach stops along the way to Florida.
The Orion Pad Abort 1 Test crew module is moved to viewing location at the Rocket Garden at The Kennedy Space Center Visitor Complex. Credit: Lockheed Martin
The Orion PA-1 test article is on display until July 4 in the historic Rocket Garden at Kennedy in the shadow of a mighty Saturn 1B and alongside Mercury, Gemini and Apollo Era capsules and rockets. The mockup of the LAS is also still on display at the Kennedy Visitor Complex.
NASA's Exploration Systems Mission Directorate (ESMD) visits the Orion MPCV in Colorado. Doug Cooke, Associate Administrator for ESMD, and Dr. Laurie Leshin, Deputy Associate Administrator for ESMD, are pictured with Mark Kirasich, Deputy Program Manager for Orion MPCV. Credit: NASAOrion Cutaway diagram
The concept of accelerating expansion does get you wondering just how much it can accelerate. Theorists think there still might be a chance of a big crunch, a steady-as-she-goes expansion or a big rip. Or maybe just a little rip?
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One of a number of seemingly implausible features of dark energy is that its density is assumed to be constant over time. So, even though the universe expands over time, dark energy does not become diluted, unlike the rest of the contents of the universe.
As the universe expands, it seems that more dark energy appears out of nowhere to sustain the constant dark energy density of the universe. So, as times goes by, dark energy will become an increasingly dominant proportion of the observable universe – remembering that it is already estimated as being 73% of it.
An easy solution to this is to say that dark energy is a feature inherent in the fabric of space-time, so that as the universe expands and the expanse of space-time increases, so dark energy increases and its density remains constant. And this is fine, as long as we then acknowledge that it isn’t really energy – since our otherwise highly reliable three laws of thermodynamics don’t obviously permit energy to behave in such ways.
An easy solution to explain the uniform acceleration of the universe’s expansion is to propose that dark energy has the feature of negative pressure – where negative pressure is a feature inherent in expansion.
Applying this arcane logic to observation, the observed apparent flatness of the universe’s geometry suggests that the ratio of dark energy pressure to dark energy density is approximately 1, or more correctly -1, since we are dealing with a negative pressure. This relationship is known as the equation of state for dark energy.
In speculating about what might happen in the universe’s future, an easy solution is to assume that dark energy is just whatever it is – and that this ratio of pressure to density will be sustained at -1 indefinitely, whatever the heck that means.
But cosmologists are rarely happy to just leave things there and have speculated on what might happen if the equation of state does not stay at -1.
Three scenarios for a future driven by dark energy - its density declines over time, it stays the same or its density increases, tearing the contents of the universe to bits. If you are of the view that dark energy is just a mathematical artifact that grows as the expanse of space-time increases - then the cosmological constant option is for you.
If dark energy density decreased over time, the acceleration rate of universal expansion would decline and potentially cease if the pressure/density ratio reached -1/3. On the other hand, if dark energy density increased and the pressure/density ratio dropped below -1 (that is, towards -2, or -3 etc), then you get phantom energy scenarios. Phantom energy is a dark energy which has its density increasing over time. And let’s pause here to remember that the Phantom (ghost who walks) is a fictional character.
Anyhow, as the universe expands and we allow phantom energy density to increase, it potentially approaches infinite within a finite period of time, causing a Big Rip, as the universe becomes infinite in scale and all bound structures, all the way down to subatomic particles, are torn apart. At a pressure/density ratio of just -1.5, this scenario could unfold over a mere 22 billion years.
Frampton et al propose an alternative Little Rip scenario, where the pressure/density ratio is variable over time so that bound structures are still torn apart but the universe does not become infinite in scale.
This might support a cyclic universe model – since it gets you around problems with entropy. A hypothetical Big Bang – Big Crunch cyclic universe has an entropy problem since free energy is lost as everything becomes gravitationally bound – so that you just end up with one huge black hole at the end of the Crunch.
A Little Rip potentially gives you an entropy reboot, since everything is split apart and so can progress from scratch through the long process of being gravitationally bound all over again – generating new stars and galaxies in the process.
