RECENT ARTICLES

Why do we remember the past and not the future? Untangling the connections between cause and effect, choice, and entropy.

Philosophers, physicists and neuroscientists discuss how our sense of time’s flow might arise through our interactions with external stimuli—despite suggestions from Einstein's relativity that our perception of the passage of time is an illusion.

A devilish new framework of thermodynamics that focuses on how we observe information could help illuminate our understanding of probability and rewrite quantum theory.

An unusual approach to unifying the laws of physics could solve Hawking's black-hole information paradox—and its predicted gravitational "memory effect" could be picked up by LIGO.

Objective reality, and the laws of physics themselves, emerge from our observations, according to a new framework that turns what we think of as fundamental on its head.

FQXI ARTICLE

October 22, 2019

Building a Better Black Hole

How little black holes could power starships in the future—and could have fine-tuned the laws of physics in our past.

FQXi Awardees: Louis Crane

January 29, 2010

COSMIC DOGSLEDDER

Louis Crane

Not that he doesn’t try. I recently spent a long evening on the phone with Crane, an FQXi Awardee and professor of mathematics at Kansas State University in Manhattan, Kansas. Crane was trying to elaborate on the implications of the Barrett-Crane Model of loop quantum gravity, developed with fellow physicist John Barrett. To do that, he had to explain some innovative ways of doing math that I had barely even heard of. "I wish you could see my hands," Crane told me at one point. "I think you could understand it better if you could see my hands."

I doubt it, especially after receiving an e-mail from one of Crane’s early collaborators, Lee Smolin of the Perimeter Institute for Theoretical Physics. I had asked Smolin for his impressions of Crane’s recent work. Smolin replied that he had found "lots in (Crane’s) last few papers that I don’t understand technically."

So at least I’m in good company.

Defying Categorification

"Louis Crane is a mathematician by training and he tends to think and present his ideas in a very mathematical way," says physicist Christopher Isham, whose work overlaps with Crane’s, "Only a tiny fraction of theoretical physicists are familiar at all with the branches of mathematics that he uses."

It’s been that way for Crane all of his life. A mathematical prodigy who took graduate-level courses at age 14, Crane studied at the University of Chicago under Saunders Mac Lane, one of the most influential American mathematicians of the 20th century. Mac Lane cofounded of a branch of math called "category theory."

It’s sort of like crossing

Alaska by dogsled. The

view is wonderful, but

there really aren’t that

many people to share

it with.

Alaska by dogsled. The

view is wonderful, but

there really aren’t that

many people to share

it with.

- Louis Crane

Learning category theory from one of its originators sent the young Crane off on some very unusual directions. While in high school, he set out to reconcile Mac Lane’s new mathematical concepts with theoretical physics. "I decided that I wanted to stop thinking about spacetime as a continuum," he says, then adds—and I can’t quite tell if he’s joking—"Everyone just assumed I’d get over it."

Crane was determined, though, to bridge the gap that he perceived between math and physics, so he has taken courses in both throughout his career. "Right now, I’m spending half of my time reading astrophysics and the other half thinking about category theory," he says. "Some people think I’m crazy."

A Desire for Collabor-ification

Crane’s need to find people that he can share his ideas with is one of the reasons that he applied for a grant from The Foundational Questions Institute. The $135,247 award that he has received will help him travel and collaborate in person with other physicists—something that Crane thinks is vital to his work. When he and Barrett were working on their quantum gravity model, for instance, they sent each other frustrating e-mail after e-mail. But when they got in a room together for five minutes, they figured it out quickly, Crane says. "I went to England this summer because there were two people I thought I could explain this to," he says, talking about his latest work. One was Barrett, and the other is Isham, with whom he also collaborates.

Isham acknowledges that it’s hard to judge the long-term significance of the work that he and Crane do. "If successful, (we) would have a major impact on the progression of quantum gravity studies," Isham says. "But to be honest, (we) are very much shooting in the dark. It is high-risk research!"

Despite that, Crane says he keeps pursuing his work because "it’s beautiful, and most other things are ugly." Besides, he adds, "We’re going to have to know the quantum theory of gravity if we’re ever going to build little black holes."

Sure, but, wait a minute. What was that?

Black Hole-ification

Of course, Crane continues, to do so, we’ll need armies of self-replicating space robots and focusing lasers the size of an asteroid. "I haven’t spent a lot of time on the engineering," Crane concedes. "It would be very tricky."

BUILD YOUR OWN BLACK HOLE?

Just as a spectrum of colors is produced by sunlight streaming through

a prism, this image from the Chandra X-Ray Observatory shows

the spectrum of a black hole.

Credit: NASA/CfA/J.McClintock & M.Garcia

And if it is possible, then a custom-built black hole might have already been created somewhere in the past—giving rise to our own cosmos, says Crane. He cites a theory by Smolin, which suggests that our universe is only one of many, and that new universes arise within black holes. Crane reasons that long ago, intelligent beings with the ability to make artificial black holes for spaceships might have littered their universe with them. A lot of black holes could mean a lot of daughter universes—possibly including our own.

I think it’s the only

thing imaginable that

would actually get us

to the stars.

thing imaginable that

would actually get us

to the stars.

- Louis Crane on artificial black holes

If all of this is true—and we’re piling up a lot of "ifs" here— then maybe, Crane says, he’s a link in the long chain that moves humanity toward fulfilling our purpose of creating more universes.

"Maybe that’s why I do it," he says. "Maybe that’s why I don’t quit."

Now that’s a concept that I have no problem understanding.

Read Louis Crane’s essay, “Stardrives and Spinoza” (pdf), which won first prize in FQXi’s essay contest 2009.

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;
var recaptcha = $("#g-recaptcha-response").val();
if (recaptcha === "") {
event.preventDefault();
alert("The reCaptcha Box below must be checked before you submit the form");
}
else if (form.postText_main.value == '') {
alert ("The post contains no text");
return false;
}
else {
return true;
}
}

**Your name:**
(optional)

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.

CHRISTIAN CORDA wrote on June 16, 2010

Dears Jody and Jason,

you can find the paper here:

http://arxiv.org/abs/0905.3298

Cheers,

Ch.

Dears Jody and Jason,

you can find the paper here:

http://arxiv.org/abs/0905.3298

Cheers,

Ch.

CHRISTIAN CORDA wrote on June 10, 2010

Dear Scott, dears all,

you could be interested that, together with my colleague Herman Mosquera Cuesta, I recently found an exact solution to Einstein field equation which remove black holes singularity at the classical level, i.e. WITHOUT quantum argumentations. In our work, we have also given a new integration of the famous Oppenheimer-Volkoff Equation for the gravitational collapse.

The paper has been accepted for publication in Mod. Phys. Lett.A.

You can find the...

Dear Scott, dears all,

you could be interested that, together with my colleague Herman Mosquera Cuesta, I recently found an exact solution to Einstein field equation which remove black holes singularity at the classical level, i.e. WITHOUT quantum argumentations. In our work, we have also given a new integration of the famous Oppenheimer-Volkoff Equation for the gravitational collapse.

The paper has been accepted for publication in Mod. Phys. Lett.A.

You can find the...

JODY FULFORD wrote on May 20, 2010

I would be interested as I have ideas along those lines as well. Tell me a little about it jodywysteria@yahoo.com

I would be interested as I have ideas along those lines as well. Tell me a little about it jodywysteria@yahoo.com

read all article comments