RECENT ARTICLES

A "retrocausal" rewrite of physics, in which influences from the future can affect the past, could solve some quantum quandaries—saving Einstein's view of reality along the way.

Figuring out if A causes B should help to write the rulebook for quantum physics.

Finding the universe's wavefunction could be the key to understanding the emergence of reality.

Tests of a rival to quantum theory, taking place in the belly of the Gran Sasso d'Italia mountain, could reveal how the fuzzy subatomic realm of possibilities comes into sharp macroscopic focus.

Combining gravity with the process that transforms the fuzzy uncertainty of the quantum realm into the definite classical world we see around us could lead to a theory of quantum gravity.

FQXI ARTICLE

October 23, 2016

The Quantum PlayStation

How the PS3 is helping physicists develop a theory of quantum gravity

FQXi Awardees: Gaurav Khanna

July 18, 2010

GAURAV KHANNA

University of Massachusetts at Dartmouth

When students learn the standard story about the birth of our universe, they are usually told not to ask what came

Khanna, at the University of Massachusetts, Dartmouth, is using a network of PS3 consoles and a $15,000 grant from the Foundational Questions Institute to model this bouncing universe. He has been inspired by attempts to unite two of the most successful theories in physics: quantum mechanics, which rules the subatomic world, and general relativity, which describes situations where gravity reigns. So far, physicists have been frustrated in their attempts to find a theory that meshes the two together. Such a theory is needed if we want to understand what happens when immense gravitational forces are concentrated into microscopic volumes of spacetime, such as in black holes or at the birth of our universe.

One candidate for finding the answer is loop quantum cosmology. This theory rejects the assumption of general relativity that spacetime is made up of a continuous fabric; instead it says that spacetime is built up of discrete blocks, rather like a digital image. You may see a smooth picture, but when you zoom in you reveal individual pixels. Luckily, a pixelated universe is easy to simulate. “Computers can handle discrete objects and manipulate them very effectively and very fast,” says Khanna. “After all that’s their forte.”

In this model, our universe did not begin in an infinitely small big bang singularity, because it is impossible to squash spacetime down below some small, but finite value. Instead, the universe bounced out from a tiny volume, which in turn, was the remnant of a prior crunched-down cosmos.

But why use the PS3 to model the origins of this universe? One advantage of the PS3 is that at the time that Khanna began the project it was an open platform, which could run Linux, making scientific programming relatively easy. By hooking together a number of consoles—each with the power to accommodate fast-paced action games—Khanna has created a supercomputer equivalent to nearly 200 normal desktop computers. Not only is the PS3 supercomputer 10 times more cost effective, but it is also 10 times more power efficient, using far less electricity. In fact, SONY were so impressed by Khanna’s enterprising idea that some of their R&D division even helped Khanna get the project up and running.

Gaming Supercomputer

Khanna’s gaming supercomputer has already proved a success at simulating the behavior of black holes. For instance, his team has been able to predict the distinct signatures that should show up when black holes swallow stars. Just like a ringing bell, these black holes should set off vibrations in spacetime—known as “gravitational waves”—as they chow down. Khanna’s simulations have characterized the frequency, duration, and other properties of these waves and this information will help observational efforts, such as those to be made by the Laser Interferometer Gravitational-Wave Observatory (LIGO), to find direct evidence of black holes.

THE GRAVITY GRID

The PS3 network is the equivalent of 200 normal

desktop computers.

Size also matters in these simulations. According to loop quantum cosmology, the pixels of spacetime are unthinkably tiny when compared with observable objects. “You might want to model a planet but your building blocks are 10

Despite these difficulties, preliminary simulations have already shown that some drastic changes were needed in the loop quantum cosmology because the modeled universe did not match the features we see in the real universe around us. “The first equations we tested didn’t work, especially for cosmology and black holes,” said

Bojowald and his colleagues hope that their revised equations will fare better in Khanna’s next round of tests. If so, their refined theory could provide the blueprints for simulating conditions before our universe existed. But if not, loop quantum cosmologists will just have to keep trying to move farther up the PS3 leaderboard.

Comment on this Article

Please read the important Introduction that governs your participation in this community. Inappropriate language will not be tolerated and posts containing such language will be deleted. Otherwise, this is a free speech Forum and all are welcome!

function ValidatePostText_main () {
form = document.addPostForm_main;
if (form.postText_main.value == '') {
alert ("The post contains no text");
return false;
}
else {
return true;
}
}

**Your name:**
(optional)

**Important:** In order to combat spam, please select the letter in this menu between 'T' and 'V':
A
B
C
D
E
F
G
H
I
J
K
L
M
N
O
P
Q
R
S
T
U
V
W
X
Y
Z

Recent Comments

read all article comments

Please read the important Introduction that governs your participation in this community. Inappropriate language will not be tolerated and posts containing such language will be deleted. Otherwise, this is a free speech Forum and all are welcome!

Please enter the text of your post, then click the "Submit New Post" button below. You may also optionally add file attachments below before submitting your edits.

HTML tags are not permitted in posts, and will automatically be stripped out. Links to other web sites are permitted. For instructions on how to add links, please read the link help page.

You may use superscript (10

^{100}) and subscript (A_{2}) using [sup]...[/sup] and [sub]...[/sub] tags.You may use bold (

**important**) and italics (*emphasize*) using [b]...[/b] and [i]...[/i] tags.You may also include LateX equations into your post.

Insert LaTeX Equation
[hide]

LaTeX equations may be displayed in FQXi Forum posts by including them within [equation]...[/equation] tags. You may type your equation directly into your post, or use the LaTeX Equation Preview feature below to see how your equation will render (this is recommended).

For more help on LaTeX, please see the LaTeX Project Home Page.

LaTeX Equation Preview

preview equation

clear equation

insert equation into post at cursor

LaTeX equations may be displayed in FQXi Forum posts by including them within [equation]...[/equation] tags. You may type your equation directly into your post, or use the LaTeX Equation Preview feature below to see how your equation will render (this is recommended).

For more help on LaTeX, please see the LaTeX Project Home Page.

LaTeX Equation Preview

preview equation

clear equation

insert equation into post at cursor

Attachments
[hide]

You may optionally attach up to two documents to your post. To add an attachment, use the following feature to browse your computer and select the file to attach. The maximum file size for attachments is 1MB.

Once you're done adding file attachments, click the "Submit New Post" button to add your post.

You may optionally attach up to two documents to your post. To add an attachment, use the following feature to browse your computer and select the file to attach. The maximum file size for attachments is 1MB.

Once you're done adding file attachments, click the "Submit New Post" button to add your post.

ANONYMOUS wrote on November 9, 2013

Baggott[Farewell to Reality: How Fairy-Tale Physics Has Betrayed The Search For Scientific Truth] and even more spot-on Unzicker-Jones[Bankrupting Physics: How Top Scientists Are Gambling Away Their Credibility] critiques shame physics’ shameless rock-star media-hype P.R. spin-doctoring veracity-abandoning touting sci-fi “show-biz” trending viral exacerbated by online social networks veritable diarrhea via proliferation of uncritical “pop-sci” science-writers where all is spectacle...

Baggott[Farewell to Reality: How Fairy-Tale Physics Has Betrayed The Search For Scientific Truth] and even more spot-on Unzicker-Jones[Bankrupting Physics: How Top Scientists Are Gambling Away Their Credibility] critiques shame physics’ shameless rock-star media-hype P.R. spin-doctoring veracity-abandoning touting sci-fi “show-biz” trending viral exacerbated by online social networks veritable diarrhea via proliferation of uncritical “pop-sci” science-writers where all is spectacle...

ANONYMOUS wrote on November 9, 2013

Baggott[Farewell to Reality: How Fairy-Tale Physics Has Betrayed The Search For Scientific Truth] and even more spot-on Unzicker-Jones[Bankrupting Physics: How Top Scientists Are Gambling Away Their Credibility] critiques shame physics’ shameless rock-star media-hype P.R. spin-doctoring veracity-abandoning touting sci-fi “show-biz” trending viral exacerbated by online social networks veritable diarrhea via proliferation of uncritical “pop-sci” science-writers where all is spectacle...

Baggott[Farewell to Reality: How Fairy-Tale Physics Has Betrayed The Search For Scientific Truth] and even more spot-on Unzicker-Jones[Bankrupting Physics: How Top Scientists Are Gambling Away Their Credibility] critiques shame physics’ shameless rock-star media-hype P.R. spin-doctoring veracity-abandoning touting sci-fi “show-biz” trending viral exacerbated by online social networks veritable diarrhea via proliferation of uncritical “pop-sci” science-writers where all is spectacle...

JOE BLOGS wrote on April 18, 2011

Holy Trinity equation.

1/3 APPLE+1/3 oRANGE+1/3 oRANGE= 1 APPLE/ORANGE

1+1=2

1 odd+ 1 Even= 2 ODD.

2+2=4

2 ODD+ 2 EVEN= 4 EVEN

Holy Trinity equation.

1/3 APPLE+1/3 oRANGE+1/3 oRANGE= 1 APPLE/ORANGE

1+1=2

1 odd+ 1 Even= 2 ODD.

2+2=4

2 ODD+ 2 EVEN= 4 EVEN

read all article comments

And select the letter between 'S' and 'U':