Expansion of Universe accelerating


Ask Ethan: Does Dark Energy Mean We’re Losing Information About The Universe?

“The universe’s expansion means our visible horizon is retreating; things faraway are vanishing continuously. (Albeit slowly, right now.) This would seem to imply we are losing information about the universe. So why is it the idea of losing information in a black hole’s event horizon is so controversial, if we’re constantly losing information to another horizon?”

As you look to greater and greater distances, you’re looking back in time in the Universe. But thanks to dark energy, what we can see and access today isn’t always going to be accessible. As galaxies grow more distant with the accelerated expansion of the Universe, they eventually recede faster than the speed of light. At present, 97% of the galaxies in the Universe aren’t reachable by us, even at the speed of light. But that isn’t the same as losing information. As a galaxy crosses over the horizon, its information never disappears from the Universe connected to us entirely. Instead, it gets imprinted on the cosmic horizon, the same way that information falling into a black hole gets imprinted on its event horizon. But there’s a fundamental difference between a black hole’s decaying horizon to the cosmic horizon’s eternal persistence, and that makes all the difference.

Come learn why even with dark energy, we don’t lose information about the Universe, but why the black hole information paradox is real!


How long has the Universe been accelerating?

“The Universe has been accelerating for the past six billion years, and if we had come along sooner than that, we might never have considered an option beyond the three possibilities our intuition would have led us to. Instead, we get to perceive and draw conclusions about the Universe exactly as it is, and that’s perhaps the greatest reward of all.”

One of the biggest surprises in our understanding of the Universe came at the end of the 20th century, when we discovered that the Universe wasn’t just expanding, but that the expansion was accelerating. That means the fate of our Universe is a cold, lonely and isolated one, but it’s a fate that we wouldn’t have uncovered if we were born when the Universe was just half its current age. By understanding the Universe’s expansion history and determining what the different components are that it’s made of, we can figure out exactly how long the Universe has been accelerating. We find that dark energy rose to prominence some 7.8 billion years ago, and the Universe has been accelerating for the last 6 billion years. As the acceleration continues, more and more galaxies become unreachable from our perspective, even at the speed of light; that number’s already up to 97% of the galaxies in our visible Universe.

[O]ne trillion, trillion, trillion years from now, the accelerating expansion of the universe will have disintegrated the fabric of matter itself, terminating the possibility of embodiment. Every star in the universe will have burnt out, plunging the cosmos into a state of absolute darkness and leaving behind nothing but spent husks of collapsed matter. All free matter, whether on planetary surfaces or in interstellar space, will have decayed, eradicating any remnants of life…. [T]he stellar corpses littering the empty universe will evaporate into a brief hailstorm of elementary particles. Atoms themselves will cease to exist. Only the implacable gravitational expansion will continue, driven by the currently inexplicable force called ‘dark energy’, which will keep pushing the extinguished universe deeper and deeper into an eternal and unfathomable blackness.
—  Ray Brassier, Nihil Unbound 

NEW THEORY OF GRAVITY MIGHT EXPLAIN DARK MATTER A new theory of gravity might explain the curious motions of stars in galaxies. Emergent gravity, as the new theory is called, predicts the exact same deviation of motions that is usually explained by inserting dark matter in the theory. Prof. Erik Verlinde, renowned expert in string theory at the University of Amsterdam and the Delta Institute for Theoretical Physics, published a new research paper today in which he expands his groundbreaking views on the nature of gravity. In 2010, Erik Verlinde surprised the world with a completely new theory of gravity. According to Verlinde, gravity is not a fundamental force of nature, but an emergent phenomenon. In the same way that temperature arises from the movement of microscopic particles, gravity emerges from the changes of fundamental bits of information, stored in the very structure of spacetime. Newton’s Law from Information In his 2010 article [http://link.springer.com/article/10.1007/JHEP04%282011%29029], Verlinde showed how Newton’s famous second law, which describes how apples fall from trees and satellites stay in orbit, can be derived from these underlying microscopic building blocks. Extending his previous work and work done by others, Verlinde now shows how to understand the curious behaviour of stars in galaxies without adding the puzzling dark matter. Puzzling Star Velocities The outer regions of galaxies, like our own Milky Way, rotate much faster around the centre than can be accounted for by the quantity of ordinary matter like stars, planets and interstellar gasses. Something else has to produce the required amount of gravitational force, and so dark matter entered the scene. Dark matter seems to dominate our universe: more than 80% of all matter must have a dark nature. Hitherto, the alleged dark matter particles have never been observed, despite many efforts to detect them. No Need for Dark Matter According to Erik Verlinde, there is no need to add a mysterious dark matter particle to the theory. In a new paper, which appeared today on the ArXiv preprint server, Verlinde shows how his theory of gravity accurately predicts the velocities by which the stars rotate around the center of the Milky Way, as well as the motion of stars inside other galaxies. “We have evidence that this new view of gravity actually agrees with the observations, “ says Verlinde. “At large scales, it seems, gravity just doesn’t behave the way Einstein’s theory predicts.” At first glance, Verlinde’s theory has features similar to modified theories of gravity like MOND (modified Newtonian Dynamics, Mordehai Milgrom (1983)). However, where MOND tunes the theory to match the observations, Verlinde’s theory starts from first principles. “A totally different starting point,” according to Verlinde. Adapting the Holographic Principle One of the ingredients in Verlinde’s theory is an adaptation of the holographic principle, introduced by his tutor Gerard ‘t Hooft (Nobel Prize 1999, Utrecht University) and Leonard Susskind (Stanford University). According to the holographic principle, all the information in the entire universe can be described on a giant imaginary sphere around it. Verlinde now shows that this idea is not quite correct: part of the information in our universe is contained in space itself. Information in the Bulk This extra information is required to describe that other dark component of the universe: the dark energy, which is held responsible for the accelerated expansion of the universe. Investigating the effects of this additional information on ordinary matter, Verlinde comes to a stunning conclusion. Whereas ordinary gravity can be encoded using the information on the imaginary sphere around the universe only – as he showed in his 2010 work – the result of the additional information in the bulk of space is a force that nicely matches the one so far attributed to dark matter. On the Brink of a Scientific Revolution Gravity is in dire need of new approaches like the one by Verlinde, since it doesn’t combine well with quantum physics. Both theories, the crown jewels of 20th century physics, cannot be true at the same time. The problems arise in extreme conditions: near black holes, or during the Big Bang. Verlinde: “Many theoretical physicists like me are working on a revision of the theory, and some major advancements have been made. We might be standing on the brink of a new scientific revolution that will radically change our views on the very nature of space, time and gravity.”

Lambda-CDM, accelerated expansion of the universe. The time-line in this schematic diagram extends from the Big Bang/inflation era 13.7 Gyr ago to the present cosmological time.


Could a new type of supernova eliminate dark energy?

“Imagine you had a box of candles that you thought were all identical to one another: you could light them up, put them all at different distances, and immediately, just from measuring the brightness you saw, know how far away they are. That’s the idea behind a standard candle in astronomy, and why type Ia supernovae are so powerful.

But now, imagine that these candle flames aren’t all the same brightness! Suddenly, some are a little brighter and some are a little dimmer; you have two classes of candles, and while you might have more of the brighter ones close by, you might have more of the dimmer ones far away. That’s what we think we’ve just discovered with supernovae: there are actually two separate classes of them, where one’s a little brighter in the blue/UV, and one’s a little brighter in the red/IR, and the light curves they follow are slightly different. This might mean that, at high redshifts (large distances), the supernovae themselves are actually intrinsically fainter, and not that they’re farther away.”

Back in the 1990s, scientists were quite surprised to find that when they measured the brightness and redshifts of distant supernovae, they appeared fainter than one would expect, leading us to conclude that the Universe was expanding at an accelerating rate to push them farther away. But a 2015 study put forth a possibility that many scientists dreaded: that perhaps these distant supernovae were intrinsically different from the ones we had observed nearby. Would that potentially eliminate the need for dark energy altogether? Or would it simply change ever-so-slightly the amount and properties of dark energy we required to explain modern cosmology? A full analysis shows that dark energy is here to stay, regardless of the supernova data.

The universe is expanding at an accelerating rate, or is it?

Five years ago, the Nobel Prize in Physics was awarded to three astronomers for their discovery, in the late 1990s, that the universe is expanding at an accelerating pace.

Their conclusions were based on analysis of Type Ia supernovae – the spectacular thermonuclear explosion of dying stars – picked up by the Hubble space telescope and large ground-based telescopes. It led to the widespread acceptance of the idea that the universe is dominated by a mysterious substance named ‘dark energy’ that drives this accelerating expansion.

Now, a team of scientists led by Professor Subir Sarkar of Oxford University’s Department of Physics has cast doubt on this standard cosmological concept. Making use of a vastly increased data set – a catalogue of 740 Type Ia supernovae, more than ten times the original sample size – the researchers have found that the evidence for acceleration may be flimsier than previously thought, with the data being consistent with a constant rate of expansion.

The study is published in the Nature journal Scientific Reports.

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[O]ne trillion, trillion, trillion years from now, the accelerating expansion of the universe will have disintegrated the fabric of matter itself, terminating the possibility of embodiment. Every star in the universe will have burnt out, plunging the cosmos into a state of absolute darkness and leaving behind nothing but spent husks of collapsed matter. All free matter, whether on planetary surfaces or in interstellar space, will have decayed, eradicating any remnants of life…. [T]he stellar corpses littering the empty universe will evaporate into a brief hailstorm of elementary particles. Atoms themselves will cease to exist. Only the implacable gravitational expansion will continue, driven by the currently inexplicable force called ‘dark energy’, which will keep pushing the extinguished universe deeper and deeper into an eternal and unfathomable blackness.
—  Ray Brassier, from ‘Nihil Unbound’
Why Type Ia Supernovae Continue to Burn Bright

Three years after its explosion, a type Ia supernova continues to shine more brightly than expected, new research finds. The observations, made with the Hubble Space Telescope and published today in The Astrophysical Journal, suggest that powerful explosions like this one produce a heavy form of cobalt that gives the heat from nuclear decay an energy boost.

The work could help researchers pinpoint the parents of type Ia supernovae and reveal the mechanics behind these events. These particular types of stellar explosions are frequently used to measure distances to faraway galaxies, and have grown more important to the field in recent decades, after they were used to demonstrate that expansion of the universe is accelerating. But researchers still have many questions about the phenomenon.

“We still do not know exactly what type of star system explodes as a type Ia supernova or how the explosion takes place,“ said lead author Or Graur, a research associate in the American Museum of Natural History’s Department of Astrophysics and a postdoctoral researcher at New York University. "A lot of research has gone into these two questions, but the answers are still elusive.”

Current research suggests that type Ia supernovae begin in binary star systems, where two stars orbit one another, and where at least one star is a white dwarf. The explosion is the result of a thermonuclear chain reaction, which produces vast quantities of heavy elements. The light that researchers see when a type Ia supernova explodes comes from the radioactive decay of these elements, notably when an isotope of nickel (56Ni) decays into an isotope of cobalt (56Co) and then into a stable isotope of iron (56Fe).

Read the full story on the Museum blog. 


Ask Ethan: Could dark energy recycle the Universe?

“If eternal inflation is correct, could dark energy be a precursor to a return to that original state?”

Our Universe began with a period of cosmic inflation: where energy intrinsic to space itself caused an extremely rapid, exponential expansion. This stretched the Universe flat, gave it the same properties, temperature and spectrum of fluctuations everywhere, and then gave rise to the hot Big Bang. And our Universe is ending in a blaze of dark energy, driving the Universe apart with an extremely slow (but accelerating) exponential expansion, that will stretch the Universe flat, and give it the same properties and temperature everywhere. Would it be possible that these two phenomena aren’t only related, but that dark energy could result in the Universe recycling itself, creating a new hot Big Bang after a long enough period of time? Realistically, there are two possible ways for this to happen, although the data presently don’t favor either one.

Amid a backdrop of far-off galaxies, the majestic dusty spiral, NGC 3370, looms in the foreground in this NASA Hubble Space Telescope image. Recent observations taken with the Advanced Camera for Surveys show intricate spiral arm structure spotted with hot areas of new star formation. But this galaxy is more than just a pretty face. Nearly 10 years earlier NGC 3370, in the constellation Leo, hosted a bright exploding star.

In November 1994, the light of a supernova in nearby NGC 3370 reached Earth. This stellar outburst briefly outshone all of the tens of billions of other stars in its galaxy. Although supernovae are common, with one exploding every few seconds somewhere in the universe, this one was special. Designated SN 1994ae, this supernova was one of the nearest and best observed supernovae since the advent of modern, digital detectors. It resides 98 million light-years (30 megaparsecs) from Earth. The supernova was also a member of a special subclass of supernovae, the type Ia, the best tool astronomers have to chart the growth rate of the expanding universe.

Recently, astronomers have compared nearby type Ia supernovae to more distant ones, determining that the universe is now accelerating in its expansion and is filled with mysterious “dark energy.” Such measurements are akin to measuring the size of your room by stepping it off with your feet. However, a careful measurement of the length of your foot (to convert your measurements into inches or centimeters) is still needed to know the true size of your room. Similarly, astronomers must calibrate the true brightness of type Ia supernovae to measure the true size and expansion rate of the universe.

The very nearest type Ia supernovae, such as SN 1994ae, can be used to calibrate distance measurements in the universe, because other, fainter stars of known brightness can be observed in the same galaxy. These stellar “standard candles” are the Cepheid variable stars, which vary regularly in brightness with periods that are directly related to their intrinsic brightness, and thus allow the distance to the galaxy—and the supernova—to be determined directly. However, only the Hubble Space Telescope, equipped with its new Advanced Camera for Surveys, has the capability to resolve these individual Cepheids.

Adam Riess, an astronomer at Space Telescope Science Institute in Baltimore, Md., observed NGC 3370 a dozen times over the course of a month and has seen many Cepheid variables. Already he and his colleagues can see that these Cepheids are the most distant yet observed with Hubble. Because of their need to observe this galaxy with great frequency to record the variation of the Cepheids, the total exposure time for this galaxy is extremely long (about one full day), and the combined image provides one of the deepest views taken by Hubble. As a result, thousands of distant galaxies in the background are easily discernable.

Object Name: NGC 3370

Image Type: Astronomical

Credit: NASA, The Hubble Heritage Team and A. Riess (STScI)

Time And Space

Since 1990, the Hubble Space Telescope has broadened our species’ collective understanding of the universe. For the past 24 years, this massive telescope has been regarded as one of the greatest scientific instruments we as humans have ever constructed. Hubble has contributed to our understanding of the universe in various ways, upending several key theories about the cosmos. Specifically, the Hubble Space Telescope proved vital with regards to the realization that the expansion of the universe is accelerating – not slowing down as was widely believed.

While Hubble continues to unveil the universe to us, plans for its successor are already underway. NASA has developed infrared-sensitive telescopes and instruments, such as the Wide Field Camera on Hubble which was fitted in 2009. This relatively new addition of infrared viewing capability is a small sample of what is on the horizon for astronomical study. The James Webb Space Telescope – set to launch in 2018 – will expand upon this technology and has a mission objective that includes observing the most distant objects in the universe. This task simply isn’t possible using standard cameras, as astronomers will have to rely upon infrared technology accordingly.

As part of Hubble’s 24th anniversary of being in service, we at Penny4NASA want to plug David Gaynes’ documentary, “Saving Hubble.”



Ask Ethan: Will The ‘Great Attractor’ Defeat Dark Energy?

“If we are only ultimately bound to [Andromeda], and everything else will eventually slip out of our visible universe, how can all the we all be heading to the great attractor (or whatever we’re all heading towards at the gravitational center of Laniakea)?”

When dark energy was discovered, and the expansion of the Universe was shown to be accelerating, there was concurrently another puzzle that received much less attention: the problem of the Great Attractor. Galaxies appear to move due to both the Hubble expansion and the local gravitational field, but the gravity from the galaxies we saw didn’t account for all the motion. There must have been an additional set of masses, revealed only in the 2010s with the identification of the supercluster Laniakea. All the galaxies in our local neighborhood are headed towards it, but are we moving fast enough to overcome the expansive pull of dark energy?

The answer looks to be no; come find out why on this week’s Ask Ethan!


How certain are we of the Universe’s ‘Big Freeze’ fate?

“In the end, all we can go off of is what we’ve measured, and admit that the possibilities of what’s uncertain could go in any number of directions. Dark energy appears consistent with a cosmological constant, and there’s no reason to doubt this simplest of models in describing it. But if dark energy gets stronger over time, or if that exponent turns out to be a positive number (even if it’s a small positive number), our Universe might end in a Big Rip instead, where the fabric of space gets torn apart. It’s possible that dark energy may change over time and reverse sign, leading to a Big Crunch instead. Or it’s possible that dark energy may increase in strength and undergo a phase transition, giving rise to a Big Bang once again, and restarting our “cyclical” Universe.”

The discovery of the accelerated expansion of the Universe – and of dark energy behind it – in 1998 was one of the biggest physics revolutions of our lifetime. By measuring these distant galaxies and how their distances and redshifts scale in the Universe, we were able to determine that despite everything we knew about matter and radiation, there was an additional force at play, and it caused distant galaxies to accelerate away from us. The data is now good enough to determine that dark energy is extremely close, if not identical, to the predictions of a cosmological constant. But there are still other theoretical possibilities that are admissible, even if they aren’t favored. Perhaps in the coming decades, we’ll find out that the ‘Big Freeze’ isn’t necessarily where we’re headed in the distant future?


What is the strongest force in the Universe?

“On the largest scales, the fundamental, tiny amount of energy inherent to space itself — less than one Joule of energy per cubic kilometer of space — is enough to overcome even the gravitational attraction between the most massive galaxies and clusters in the Universe. The result? An accelerated expansion, as the most distant galaxies and clusters move farther and farther away from one another at ever faster rates as time goes on. On the largest cosmic scales, even gravity doesn’t get its way.”

But what does it truly mean to be strong? We have four fundamental forces in the Universe: the strong, electromagnetic, weak and gravitational forces. You might think that, by virtue of its name, the strong force is the strongest one. And you’d be right, from a particular point of view: at the smallest distance scales, 10^-16 meters and below, no other force can overpower it.
But under the right circumstances, each of the forces can shine. Up until recently, on the largest scales, we thought that gravitation – by and large the weakest of the forces – was the only force that mattered. And yet, when we look on the very largest scales, many billions of light years in size, even gravitation doesn’t win the day.
There are four possible answers depending on how you look at the question. Come find out who’s the strongest of them all!


A perfect Universe: could it have been born completely uniform?

“If it weren’t for dark energy — if all we had was matter and radiation — then in enough time, we could form structure in the Universe no matter how small those initial fluctuations were. But that inevitability of an accelerated expansion gives our Universe a sense of urgency that we wouldn’t have had otherwise, and makes it absolutely necessary that the magnitude of the mean fluctuations be at least about 0.00001% of the average density in order to have a Universe with any notable bound structures at all. Make your fluctuations smaller than that, and you’ll have a Universe with nothing at all.”

Billions of years ago, before the Universe contained clusters, galaxies, stars or even neutral atoms, everything was uniform. Almost perfectly uniform, where the densest regions weren’t even 0.01% denser than average. Over billions of years, those overdense regions have attracted more and more matter and grown under the influence of gravity. By today, we have the incredible rich, clumpy, structured Universe we exist in. But what about a more perfect Universe, one that was totally uniform? Could that have given rise to us? And if not, what is the limiting factor? It’s a fascinating question, and one science can answer.

Come get the full story on the idea of a perfect Universe, and learn the most valuable cosmic lesson of all: sometimes our imperfections are necessary for the best outcomes of all.

anonymous asked:

Hey. I was wondering if you could answer a few questions about a project I'm doing for chemistry. So we got to chose a topic and it's basically a lab report that we must find that goes with our title, so my title is How Much Has The Universe Expanded Over Time and I'm not sure how to go about the materials needed for finding that as well as the procedural steps, control, independent, and dependent variables. Anything you have to say would be a big help.

Hmm since I don’t exactly know the specifics of your project my answers may not be too helpful. With that in mind, and judging by the title you’ve chosen, I would probably talk about the Hubble Constant. The Hubble Constant is the unit of measurement used to describe the rate of expansion of the universe. I’d also talk about the early universe expanding at a slower rate and the possibility that the expansion is accelerating in our present time.

There is a quite a lot of information you could cover in your lab report about the expansion of the universe. Also, since this is all heavy in astronomy and physics, I’m not exactly sure how much Chemistry you have to toss into it. Nevertheless, here are a few other resources related to what I’m talking about:

Hubble Law and the Expanding Universe
Universe Expansion
Evidence for an Accelerating Universe

Hope this helps! If you have any other questions please let me know.

Reality is a set of ideas that predicts the observations we make.

-Brian Schmidt, an Australian National University cosmology professor, speaking about “The Astronomical Revolution” on June 24, 2014, at the Euroscience Open Forum. Schmidt is a winner of the 2011 Nobel Prize for Physics based on his work uncovering the accelerating expansion of the universe.

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“They’re like, ‘Sir, there’s something in your bag.’

I said, ‘Yes, I think it’s this box.’

They said, ‘What’s in the box?’

I said, ‘a large gold medal,’ as one does.

So they opened it up and they said, ‘What’s it made out of?’

I said, ‘gold.’

And they’re like, ‘Uhhhh. Who gave this to you?’

‘The King of Sweden.’

‘Why did he give this to you?’

‘Because I helped discover the expansion rate of the universe was accelerating.’


Brian Schmidt, 2011 Nobel Prize winner in Physics, explaining his Nobel Prize to the TSA agents inspecting it on his flight to see his grandmother in Fargo.

Today, in conversations I will never have ….