First-ever model simulation of the structuring of the observable universe

Apr 12, 2012

A team of researchers from the Laboratoire Univers et Theorie (France) coordinated by Jean-Michel Alimi has performed the first-ever computer model simulation of the structuring of the entire observable universe, from the Big Bang to the present day.

The simulation has made it possible to follow the evolution of 550 billion . This is the first of three runs which are part of an exceptional project called Deus: full run, carried out using GENCI’s new supercomputer CURIE at the CEA's Très Grand Centre de Calcul (TGCC). This simulation, along with the two additional runs expected by late May 2012, will provide outstanding support for future projects dedicated to the observation and mapping of the universe. These simulations will shed light on the nature of dark energy and its effects on cosmic structure formation, and hence on the distribution of and galaxies in the universe.

After several years' research, six scientists of the cosmology group at LUTH have performed the first-ever computer of the structuring of the entire observable universe, from the Big Bang to the present day. This first simulation of the standard model of the universe with a cosmological constant will be followed by two additional runs focusing on the cosmological evolution of models with dark energy, the mysterious component introduced to account for the accelerated expansion of the universe. What imprint does dark energy leave on cosmic structures? And inversely, how can the nature of dark energy be inferred from observing the distribution of matter in the universe? These are two fundamental questions that the project Deus : full universe run will seek to answer.

Simulation of the standard cosmological model has already allowed researchers to discover a number of important properties concerning the distribution of matter in the universe. As an example, they have succeeded in estimating the total number of galaxy clusters with a mass larger than a hundred thousand billion solar masses. These clusters currently amount to 144 millions. The researchers have found that the first galaxy cluster of this type formed when the universe was only 2 billion years old and the most massive cluster in the observable universe today weighs 15 quadrillion (or 15 thousand trillion) solar masses. The data generated by the run has also allowed the scientists to evaluate spatial distribution of dark matter density fluctuations in the universe. These fluctuations have the same origin as those found in the Cosmic Microwave Background radiation, resulting from the Big-Bang and observed by the WMAP and Planck satellites. These measurements were obtained in a simulation covering the entire evolutionary history of the universe with previously unattained precision and on a much wider range of scales, from a few millionths to the size of the entire observable universe. This also revealed with unprecedented accuracy the imprint of the primordial plasma's acoustic oscillations on the distribution of dark matter (“Baryon Acoustic Oscillations”). This simulation already seems like a gold mine of new results for the cosmology community.

The implementation of this exceptional project would not have been possible without the powerful resources made available to the researchers by the Grand Equipement National de Calcul Intensif (GENCI), whose new supercomputer CURIE is equipped with more than 92,000 CPUs and can perform 2 million billion operations per second (2 PFlop/s). The CURIE supercomputer is housed and operated by the CEA at the Très Grand Centre de Calcul, at Bruyères-le-Châtel (Essonne). Designed by Bull, it is one of the world's five most powerful supercomputers.

The implementation of Deus : full universe run represents a new stage in the development of supercomputing. The first simulation in the project has largely outperformed the most advanced cosmological simulations carried out over the past few years by a number of international collaborations at the largest supercomputing facilities around the world. The entire project will use more than 30 million hours (about 3500 years) of computing time on virtually all CPUs of CURIE. More than 150 PBytes of data (the equivalent of 30 million DVDs) are generated throughout the computing runs. Thanks to an advanced and innovative data reduction process developed by the researchers, the amount of useful stored data can now be reduced to 1 PBytes.

In the standard cosmological model with a cosmological constant, it is now possible to go through the distribution of dark matter and galaxies across the cosmos over a distance equivalent to 90 billion light-years and follow their evolution throughout the entire history of the universe.

The results of these voyages across the full , from the present day back to the for the three cosmological models, are expected by late May 2012. These results will improve current understanding of the influence of on the structure of the universe. They will also provide exceptional support for the development and interpretation of present and future cosmic catalogues from major observational projects, especially those launched by international space agencies. These include the EUCLID mission, which has been selected by ESA, the European Space Agency.

Explore further: How the hummingbird achieves its aerobatic feats

add to favorites email to friend print save as pdf

Related Stories

'Dark energy' targeted in European space mission

Oct 04, 2011

So-called dark energy, believed to play a role in the accelerated expansion of the Universe, will be studied in a major science mission to be launched later this decade, the European Space Agency (ESA) said ...

Cosmic coincidence

Sep 05, 2011

Cosmologists tend not to get all that excited about the universe being 74% dark energy and 26% conventional energy and matter (albeit most of the matter is dark and mysterious as well). Instead they get excited ...

Cosmological simulations key to understanding the universe

Feb 17, 2009

Tiziana Di Matteo, associate professor of physics at Carnegie Mellon University is harnessing the power of supercomputing to recreate how galaxies are born, how they develop over time and, ultimately, how they collapse.

Cosmologists 'see' the cosmic dawn

Feb 11, 2009

(PhysOrg.com) -- The images, produced by scientists at Durham University's Institute for Computational Cosmology, show the "Cosmic Dawn" - the formation of the first big galaxies in the Universe.

Recommended for you

How the hummingbird achieves its aerobatic feats

4 hours ago

(Phys.org) —The sight of a tiny hummingbird hovering in front of a flower and then darting to another with lightning speed amazes and delights. But it also leaves watchers with a persistent question: How ...

New terahertz device could strengthen security

Nov 21, 2014

We are all familiar with the hassles that accompany air travel. We shuffle through long lines, remove our shoes, and carry liquids in regulation-sized tubes. And even after all the effort, we still wonder if these procedures ...

CERN makes public first data of LHC experiments

Nov 21, 2014

CERN today launched its Open Data Portal where data from real collision events, produced by experiments at the Large Hadron Collider (LHC) will for the first time be made openly available to all. It is expected ...

User comments : 44

Adjust slider to filter visible comments by rank

Display comments: newest first

Tachyon8491
1.9 / 5 (9) Apr 12, 2012
This is great - wonderful perspective on cosmological ontogeny. Now if only we knew what was before the Unified Field was...
Musashi
1.7 / 5 (3) Apr 12, 2012
There's as much a "before" as there's an "outside".
Musashi
2.3 / 5 (6) Apr 12, 2012
DEUS is "god" in Portuguese. What a coinkidink.
Vendicar_Decarian
2.3 / 5 (3) Apr 12, 2012
Looks like the universe is inside a black hole.
Snicker.
Deesky
2.6 / 5 (5) Apr 12, 2012
This is good stuff. When the simulations reproduce the visible universe trough time with good accuracy, they can then tweak various parameters to see what effect they would have on the development of the universe. This in turn may lead to insights about the nature of dark matter and even more puzzling, dark energy. It might tell us new things to look out for in astronomical surveys - a kind of a vitreous cycle.
kaasinees
3.7 / 5 (6) Apr 12, 2012
DEUS is "god" in Portuguese. What a coinkidink.

Its walloon for two.
Deathclock
3 / 5 (4) Apr 12, 2012
Looks like the universe is inside a black hole.
Snicker.


Could be, google "universe in black hole"... you'll find papers that have been published in arXiv by astrophysicists about the topic.
nuge
3 / 5 (2) Apr 13, 2012
I wonder if there are simulated intelligent lifeforms somewhere inside that simulation that are capable of building a simulation of their simulated universe. Wait, maybe that's what we are. Wait, maybe it's simulations ALL THE WAY DOWN FOR INFINITY.

Okay, I think I need to lie down for a while...
kevinrtrs
1.9 / 5 (15) Apr 13, 2012
It's great that it's possible to simulate the existing paradigm.
I still maintain it might be a good idea to model only the observed universe and cut out the assumptions [about origins] made within the current [or any other] model and see where that leads.
As it stands now any results obtained from this simulation will have to be taken with lots of salt and it will probably be contradicted by actual observations time and time again.
antialias_physorg
5 / 5 (4) Apr 13, 2012
DEUS is "god" in Portuguese

It's a word play on stage-play term "deus ex machina" (which is latin)
bewertow
3.4 / 5 (5) Apr 13, 2012
It's great that it's possible to simulate the existing paradigm.
I still maintain it might be a good idea to model only the observed universe and cut out the assumptions [about origins] made within the current [or any other] model and see where that leads.
As it stands now any results obtained from this simulation will have to be taken with lots of salt and it will probably be contradicted by actual observations time and time again.


And your opinion is important because you are such an expert on cosmology.
Tachyon8491
3.1 / 5 (13) Apr 13, 2012
There is a cult of ignorance in the United States, and there has always been. The strain of anti-intellectualism has been a constant thread winding its way through our political and cultural life, nurtured by the false notion that democracy means that "my ignorance is just as good as your knowledge.
Isaac Asimov

We may add: "Never attribute to malintent what you can attribute to stupidity..."

Oh well, we keep trying - it's just such a pity that it takes a minimal threshold of psychospiritual calibre where, what is intended, is interpreted according to its intentions.
hemitite
1 / 5 (3) Apr 13, 2012
And those Americans - they know nothing of cheese and don't make their own breadcrumbs! The refuse to except out superior intellect and culture, maintained and expanded it the teeth of our demographic decline!
Terriva
2.5 / 5 (2) Apr 13, 2012
First-ever model simulation of the structuring of the observable universe
Millennium simulation was first or at least previous?
Bowler_4007
1 / 5 (1) Apr 13, 2012
90 billion light years? if we can see 13.7 billion light years in any direction then the diameter of the observable universe would be 27.4 billion light years, so are they looking ahead by 31.3 billion years? or are they assuming the universe may be larger than what we can see?
hemitite
not rated yet Apr 13, 2012
"...or are they assuming the universe may be larger than what we can see?"

I believe that this is the case, although I have now idea how one would estimate our universe's actual size.
nkalanaga
3.6 / 5 (5) Apr 13, 2012
The universe is certainly larger than we can see. First, the objects at the "edge", 13 billion years/lightyears away, have been moving since then, so are actually much farther way in distance than they appear. One rough estimate I saw was that objects that look 13 billion LYs away are actually about 40 billion today.

Second, there is no reason to believe that space ends at the visible edge, it's just that light hasn't had time to reach us from more distance objects.
Russkiycremepuff
1 / 5 (1) Apr 13, 2012
It's been established already in a few threads that the universe continues to expand, thusly the red and blue shifts enable us to calculate presumed distances. From that presumption, we can deduce that the expansion continues. It's a nice piece of circular logic.
The assumption that as the universe expands flat as it unrolls like a sheet of linoleum, could it also be assumed that "things" would fall off the edge as once thought about the Earth? Amusing thought.
Bowler_4007
1 / 5 (1) Apr 13, 2012
The universe is certainly larger than we can see. First, the objects at the "edge", 13 billion years/lightyears away, have been moving since then, so are actually much farther way in distance than they appear. One rough estimate I saw was that objects that look 13 billion LYs away are actually about 40 billion today.

Second, there is no reason to believe that space ends at the visible edge, it's just that light hasn't had time to reach us from more distance objects.

I only spoke of the universe having a finite size because the article assumes it does, I personally am in fact open to either, it intrigues me because if it is finite in then what if anything is outside the universe, on the other hand if the universe is infinite then it fair to assume there would be infinite amounts of matter/anti-matter and all other stuff (known and unknown to science) that exists within the universe, if course the puzzle there would how is that possible (aside from it being a natural law)?
Bowler_4007
1 / 5 (1) Apr 13, 2012
I find both possibilities absolutely fascinating but I personally hope the universe is infinite because I reckon humans would stand a better chance of a good long survival in that case
Russkiycremepuff
1 / 5 (2) Apr 13, 2012
Sometime ago in a Phys.org thread, someone mentioned that every black hole in the universe is there to recycle matter and energy, and that when each black hole has swallowed all the matter and energy in its vicinity, by then it has grown so large that it can attract others toward it and feed off them. Eventually, all matter and energy in each galaxy will be consumed in this way and all black holes will have grown so large that they can cross intergalactic space and join with each other. In this way, billions of black holes are attracted by way of gravitational forces and, after what may seem like an eternity, all of them combine into one monster of a black hole. Then the process of another Big Bang eventually begins, with all matter and energy within this one super black hole. This makes good sense to me, given that the black holes should not repel each other, but attract, flow and become one. So basically, you could say that there is a universe within a black hole.
Deathclock
1.5 / 5 (2) Apr 14, 2012
It's been established already in a few threads that the universe continues to expand, thusly the red and blue shifts enable us to calculate presumed distances. From that presumption, we can deduce that the expansion continues. It's a nice piece of circular logic.
The assumption that as the universe expands flat as it unrolls like a sheet of linoleum, could it also be assumed that "things" would fall off the edge as once thought about the Earth? Amusing thought.


It's not circular logic you just don't know what the hell you are talking about and don't understand the evidence that we have that leads all modern cosmologists and astrophysicists to the same conclusion...
Deathclock
4 / 5 (4) Apr 14, 2012
Also, some of you are confusing the Hubble volume for the size of the universe...
CardacianNeverid
4.3 / 5 (6) Apr 14, 2012
The assumption that as the universe expands flat as it unrolls like a sheet of linoleum, could it also be assumed that "things" would fall off the edge as once thought about the Earth? -RusskiPirouetteTard

Only if you're a total retard.
Benni
1 / 5 (1) Apr 14, 2012
"If we are to have in the universe an average density of matter which differs from zero, however small that difference, then the universe cannot be quasi-Euclidean. On the contrary, the results of calculation indicate that if matter be distributed uniformly, the universe would necessarily be spherical (or elliptical). Since in reality the detailed distribution of matter is not uniform, the real universe will deviate in individual parts from the spherical, that is the universe will be quasi-spherical, but it will be necessarily finite. In fact the theory supplies us with a simple connection between the space-expanse of the universe & the average density of matter in it."

Albert Einstein: Relativity - Section 30; 1916, 1924
Part III: Considerations on the Universe as a Whole

See also Mach's principle which was the basis for Einstein's comcept of a "closed universe".

Benni
1 / 5 (1) Apr 14, 2012
Footnote to above by Einstein:

"The results of calculation indicate that if matter be distributed uniformly, the universe would necessarily be spherical. I must not fail to mention that a theoretical argument can be adduced in favor of the hypothesis of a finite universe. The general theory of relativity teaches that the inertia of a given body is greater as there are more ponderable masses in proximity to it & the other bodies in the universe, ever since Newton's time, gravity has reduced to interactions between two bodies (Albert Einstein 1954)
nkalanaga
not rated yet Apr 14, 2012
A closed universe can still be "infinite". The surface of a sphere, such as the Earth, is closed, but it has no edges. In the case of the Earth it's easy to see when one has completed a circuit, because the origin looks the same when you return. In the case of the universe, the travel time would be so great, the origin would have changed too much to be recognized. So, you would have a limited volume, but be unable to find the limits.
TheGhostofOtto1923
3 / 5 (2) Apr 14, 2012
The assumption that as the universe expands flat as it unrolls like a sheet of linoleum, could it also be assumed that "things" would fall off the edge as once thought about the Earth? -RusskiPirouetteTard...This makes good sense to me, given that the black holes should not repel each other, but attract, flow and become one. So basically, you could say that there is a universe within a black hole.
Ritchie hasnt heard that galaxies are moving away from each other with increasing speed. Therefore it would not matter whether they remained galaxy-shaped, or shrank into a singularity, they would still have the same mass and would continue to exert the same gravitational force on one another as they do at present.

Of course this makes no sense to ritchie because he thinks that something with the ominous name of black hole should possess extraordinary powers to suck.

By the way ritchie how does a black hole flow? Or was this only poetic license on your part?
Shootist
1 / 5 (2) Apr 14, 2012
It would be nice if the "full size" illustrations were actually full size.
Shootist
2.3 / 5 (3) Apr 14, 2012
DEUS is "god" in Portuguese

It's a word play on stage-play term "deus ex machina" (which is latin)


Meaning God in the Machine which puts us right back where we started. The "coinkidink"
antialias_physorg
5 / 5 (3) Apr 14, 2012
Meaning God in the Machine

It means a 'god (emerging) from the machine'
Deus ex machina was a stage device (used in Greek theater and later notably by Shakespeare) where some entity (usually a god or king) would step in at the last minute and set everything right (Robin Hood would be another example).
The god would emerge from a trap door or other, similar mechanical device (hence the "ex machina"). Today that has fallen out of favor because it's sort of a cheat - basically the happenings in the entire play become pointless as the end would have been achieved even without it by the god.

It's a synonym for "sudden, unmodtivated, powerful event". This is what they were going for with their simulation: Emergence of what we see today (the universe) without putting the cause explicitly in the play (i.e. without explicitly coding for the appearance of galaxies and whatnot in the simulation).
Benni
1 / 5 (1) Apr 15, 2012
A closed universe can still be "infinite". The surface of a sphere, such as the Earth, is closed, but it has no edges.

The arc of the horizon is the "edge".

So, you would have a limited volume, but be unable to find the limits.


One side of your comma contradicts the other immediately from your quote above.

Anything of finite volume can have a "start" point along its' arc & would be the same as the "end" point after you circumnavigate the sphere along that arc & return to the "start" point, you did not travel endlessly (infinitely) to return to the "start" point. I don't think Christopher Columbus imagined for a minute that he was about to set out on a voyage that would be endless requiring an "infinite" amount of time to return to Spain after circum-navigating the sphere.


Mayday
not rated yet Apr 15, 2012
What am I missing? Evidence seems to indicate that the Universe is the basically same out to 13 bly. So wouldn't one assume that from a vantage point 13bly distant that one would see pretty much what we're seeing -- a consistent/homogenous universe out to 13bly? What might lead someone to conclude that this wouldn't go on forever in every direction? The fact that this isn't commonly accepted tells me I'm missing something. What? (I guess I'm obviously no scientist, heh?)
Benni
1 / 5 (1) Apr 15, 2012
What am I missing?

Evidence seems to indicate that the Universe is the basically same out to 13 bly -- a consistent/homogenous universe out to 13bly?
.....and this is exactly what Einstein's General Theory of Relativity states......


What might lead someone to conclude that this wouldn't go on forever in every direction?.


You are "missing" the point of Einstein's Theory of Relativity that the universe is a "closed finite sphere", BECAUSE the universe is governed by laws of thermodynamics called Conservation of Energy. Conservation of energy (work) cannot occur if "energy" is not contained inside the walls of the engine into which fuel(energy) is injected.

For every action, there is an opposite & equal reaction, that is how all the engines in the universe work, be they rocket engines, diesel, ion propulsion, etc., same with galaxies, they are engines driven by an energy source. The Universe is basically a very large pressure containment vessel.
Deathclock
1 / 5 (1) Apr 16, 2012
One side of your comma contradicts the other immediately from your quote above.

Anything of finite volume can have a "start" point along its' arc & would be the same as the "end" point after you circumnavigate the sphere along that arc & return to the "start" point, you did not travel endlessly (infinitely) to return to the "start" point. I don't think Christopher Columbus imagined for a minute that he was about to set out on a voyage that would be endless requiring an "infinite" amount of time to return to Spain after circum-navigating the sphere.




The point is he COULD travel endlessly along a straight (from his perspective) trajectory if he chose to. If 4D space is curved in on itself then we could travel in a straight path (in 3D space, according to our perception) forever.
DaFranker
1 / 5 (1) Apr 16, 2012
What if information simply doesn't transmit towards non-existence? What if information always must be transmitted between two existences (AKA "particles", whatever particles may truly be)? Then, you can just travel in one direction infinitely, and simply become infinitely further away, without the universe per-se being infinite nor looping around in a 4D curvature. Information would never be lost and no conservation law violated, as everything would always be exchanged "inwards" when at the "edge" of the universe.

What's simpler, a complex manifold with loopey space, or natural lazy transmission? Which one corresponds more with empirically observed phenomena (osmosis, chemical bonds, etc.)? Occam's Razor time.
Benni
1 / 5 (1) Apr 17, 2012



The point is he COULD travel endlessly along a straight (from his perspective) trajectory if he chose to. If 4D space is curved in on itself then we could travel in a straight path (in 3D space, according to our perception) forever.


NO....it is never possible to travel endlessly in a "finite universe", there is not enough energy contained within the total mass of the universe to make "endless" travel possible, such a journey would require an "infinite source of energy". Once again, it all comes back to the laws of thermodynamics as dictated by Conservation of Energy, and this is what so many people are "missing" when they try to imagine the universe we live in as being somehow "infinite".

An object does not need to be round to supposedly "endlessly" travel along it's perimeter, it can be cubically shaped & do the same thing, you simply have to traverse the edges at 90 degree angles as opposed to following the more gradual arc of a sphere.

antialias_physorg
not rated yet Apr 17, 2012
NO....it is never possible to travel endlessly in a "finite universe", there is not enough energy contained within the total mass of the universe to make "endless" travel possible

Since you can only travel at a finite speed (speed of light) and the nuúniverse potentially expands at a much larger rate (expansion of space is not limited to the speed of light) then you can ver well travel forever and not hit a boundary.

There are regions of space which are receeding from us at faster than light could traverse the distance (not because they are so fast but because the cumulative expansion of space in between adds more space than the light can bridge per second)

Once again, it all comes back to the laws of thermodynamics

Thermodynamics is for closed systems. A system in which space expands does not qualify as a closed system.
DaFranker
1 / 5 (1) Apr 17, 2012
NO....it is never possible to travel endlessly in a "finite universe", there is not enough energy contained within the total mass of the universe to make "endless" travel possible, such a journey would require an "infinite source of energy". Once again, it all comes back to the laws of thermodynamics as dictated by Conservation of Energy, and this is what so many people are "missing" when they try to imagine the universe we live in as being somehow "infinite".

Alright, bear with me for a moment. We (somehow) calculate the perfect, ultimate course through the universe such that our momentum is never degraded (we accelerate and decelerate through various forces that eventually even out perfectly). We launch through that course, and then let momentum carry us.

You're saying that we will not continue drifting for eternity, because eventually we'll hit a "wall" somewhere? And where is a source of energy required in any of this?
Benni
1 / 5 (1) Apr 17, 2012
NO....it is never possible to travel endlessly in a "finite universe", there is not enough energy contained within the total mass of the universe to make "endless" travel possible


Thermodynamics is for closed systems.

True enough, you just described Einstein's finite universe....

A system in which space expands does not qualify as a closed system.


And how do you know that? Einstein adamantly disagrees with you, read the quotes I posted above which come directly from his General Theory of Relativity.
Benni
1 / 5 (1) Apr 17, 2012

Alright, bear with me for a moment. We (somehow) calculate the perfect, ultimate course through the universe such that our momentum is never degraded (we accelerate and decelerate through various forces that eventually even out perfectly). We launch through that course, and then let momentum carry us.

You're saying that we will not continue drifting for eternity, because eventually we'll hit a "wall" somewhere? And where is a source of energy required in any of this?


Absolutely you will not continue drifting for eternity, because after your launch vehicle has transformed the finite mass of the universe to energy, your launch vehicle will transform its own mass into energy as the last available source of energy & your demise will be iminent, you won't just drift, you'll be destroyed.

Think of the Universe as the gas tank in your car, when the fuel is used up, the established momentum will take you only a short distance, if you don't refuel you'll go nowhere......
Benni
1 / 5 (1) Apr 17, 2012

You're saying that we will not continue drifting for eternity, because eventually we'll hit a "wall" somewhere? And where is a source of energy required in any of this?


Now, in addressing this point, about a "wall". Yes there is a wall. Assuming you can get to that wall you won't need infinite energy to do it, but it will be impenetrable or the universe cannot be "finite" as Einstein states in GR that it must be "finite".

If the wall of the universe can be penetrated it will collapse like the bursting of a balloon, because energy generated by stellar masses will have no walls against which to do "work" & fusion forces will cease, quickly. "work" can only be accomplished when mass to energy coversion occurs in a confined space.


DaFranker
1 / 5 (1) Apr 18, 2012
Benni, I think you missed the point of my posts. A finite amount of energy contained around a finite amount of matter DOES NOT logically require a "wall". All it requires is that no energy is lost or gained. In actual practice, walls technically VIOLATE the law of conservation in all observations and experiments, as the walls themselves influence the inner energy.

Walls cannot "exist" if they are not to disturb the inner system, or themselves "lose" energy outwards. Walls that have no existence likewise cannot hamper or prevent anything from going out, so they're not there, and there really are no walls. The very act of restricting our escape is a disturbance in itself.

The more likely alternative, supported by Occam's Razor, is that there is simply no energy sent where there is nothing to receive it. Nothing is then lost, even if there is no "restriction" on the "space" of the universe. Natural Lazy Interaction.
shockr
not rated yet Apr 19, 2012
DEUS is "god" in Portuguese

It's a word play on stage-play term "deus ex machina" (which is latin)


More so, it derives from the ancient Greek term as above which means 'God from Machine'. This is akin to the cavalry turning up at just the right moment to save the hero. A 'god' was lowered onto stage with machinery who would then save them from inevitable doom.

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.