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Brian Oxley
Works at ThoughtWorks
Attended Rice University
Lives in Houston, TX
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Brian Oxley

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Insanely cool.
 
Black holes - bigger on the inside

Guess what: black holes are bigger inside than they look - and they get bigger as they get older! 

For example, take the big black hole in the center of our galaxy, called Sagittarius A*.  It's about 2 million kilometers across.  That's pretty big - but the orbit of Mercury is 60 times bigger.  This black hole is old, roughly a billion years old.  And here's the cool part:  it's been growing on the inside  all this time!  

How is this possible?  Well, since spacetime is severely warped in a black hole, its volume can be bigger than you'd guess from outside.  And it keeps growing.  Since we understand general relativity quite well, we can calculate how this works!  But nobody thought of doing it until last year, when Marios Christodoulou and my friend Carlo Rovelli did it.   

How big is the black hole at the center of our galaxy?  On the inside, it can hold a million solar systems!  Its volume is about 10^34 cubic kilometers!   And it's growing at a rate of about 10^25 cubic kilometers per year!

Or suppose you have an ordinary star that turns into a black hole.  This black hole will last a long time before it evaporates due to Hawking radiation.  Christodolou and Rovelli estimate how big its volume will get before this happens.  And it gets really big: bigger than the current-day observable universe!

Before you get too excited, remember: people falling into the black hole will not have time to do anything fun inside.  They will hit the singularity in a short time.  Very very roughly speaking, the problem is not the shortage of space inside the black hole, it's the shortage of time.  

If you fall into the black hole at the center of our galaxy, it will be about 1 minute, at most, before you hit the singularity.   You will not get to see most of the space inside the black hole!   The singularity is not in the 'middle' of the black hole - it's in your future.  You will only have time to see the 'edge' of space inside the black hole. 

The 'middle regions' can only be seen by people who fell in much earlier.  And they can't see the 'edge', where you are!

And now for the serious part. 

The hard part of this problem is defining the volume inside a black hole. 

If you choose a moment in time, the black hole's event horizon at that moment is a sphere.  There are infinitely many ways to extend this sphere to a solid ball.  In other words: there are many ways to choose a slice of space inside the black hole whose boundary is your chosen sphere. 

The slice can bend forwards in time, or backwards in time.  We can choose a wiggly slice or a smooth one.  Each slice has its own volume.  

How do you choose one, so you can calculate its volume? Christodoulou and Rovelli choose the one with the largest volume. This may sound like it's cheating.  But it's not.

Think of a simpler problem one dimension down.  You have a loop of wire.  You ask me: "What's the area of the surface whose boundary is this loop?" 

I say: "That's a meaningless question!  Which surface?  There are lots!"  

You say: "Pick the best one!"

So, it's up to me.   I take some soapy water and make a soap film whose boundary is that loop.  That's the surface I use.   If the loop of wire is not too crazy in its shape, this surface is uniquely defined.   In some sense it's the "least wiggly" surface I could choose.

This surface minimizes the area.  A more wiggly surface would have more area.

Christodoulou and Rovelli are doing the same thing.  But spacetime is different than space!   If you choose a wiggly 3-dimensional spatial surface in spacetime, it will have less volume than a flatter surface with the same boundary!  

So, the way to pick the flattest, nicest spatial surface inside our black hole is to pick the one that maximizes the volume. 

If you tried to minimize the volume, you could get it as close to zero as you wanted.  And this would have nothing to do with black holes!   This would be true even in your living room.

Puzzle: why?

Here's the paper:

• Marios Christodoulou and Carlo Rovelli, How big is a black hole?, http://arxiv.org/abs/1411.2854.

#spnetwork arXiv:1441.2854 #generalRelativity  
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The size of graphene quantum dots made from coal can be finely tuned in a single step for electronic and fluorescent properties, according to scientists at Rice. #Graphene   #Science   #Coal  
The size of graphene quantum dots made from coal can be finely tuned in a single step for electronic and fluorescent properties, according to scientists at Rice.
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Darker, emptier and simpler.
Astronomers have studied how dark matter in clusters of galaxies behaves when the clusters collide. The results show that dark matter interacts with itself even less than previously thought, and narrows down the options for what this mysterious substance might be.
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[A]greement to utilize Ellington Airport’s Spaceport as a future landing site for SNC’s Uncrewed Dream Chaser® spacecraft
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The dawn of DUNE.
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Amaze your friends!
 
metal is melted inside copper loop :)

The copper loop has a significant amount of AC electricity running through it, causing it to act like a really strong electromagnet. In the metal slug, eddy currents form due to the magnetic field the copper wire is causing (while the copper wire has high frequency AC flowing through it). The metal slug's electric resistance causes a portion of the electric energy to turn into heat, but the heat builds up until the metal slug becomes white hot and melts.  The metal that is melted can be several choices, including aluminum, see http://en.wikipedia.org/wiki/Induction_heating.
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Shocking.
“IT’S like coffee times ten,” raves one enthusiast. “I use it a couple of times a week and problems solve themselves. At the end of the day, I haven’t...
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What happens when healthy people see the cancer cells their body naturally kills?
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Physicists have overlooked an obvious place to search for shell-like structures constructed around stars by advanced civilizations to capture their energy.
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3,000 down, kazillions to go.
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For +Jeff Iverson​.
We all have cameras, and the sky's an easy target, so why not have a little fun? Ever since I got my first camera at age 12 I wanted to shoot time exposures of the night sky. That and a tripod are ...
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Wonderful!

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Fitting a triangle density to data. Matching the sample mean is trivial. Matching the median is not always possible, and the algebra is a little more complicated when it is possible.
Sometimes you only need a rough fit to some data and a triangular distribution will do. As the name implies, this is a distribution whose density function graph
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Have him in circles
334 people
Darcy McLerie's profile photo
Jan Popiel's profile photo
Donna Aker's profile photo
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paulo cesar sousa's profile photo
Brian Winquist's profile photo
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Education
  • Rice University
    Physics, Music, 1987 - 1991
  • Trinity University
    Physics, Music, 1985 - 1987
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binkley
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Best wife ever. Two wonderful sons. Full Moria armor set.
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Principal Consultant
Employment
  • ThoughtWorks
    Principal Consultant, present
  • Macquarie Offshore Services
    Sr. Manager, 2013 - 2015
    IT Manager
  • Macquarie Group Limited
    Sr. Manager, 2010 - 2013
    Java Architect
  • ThoughtWorks
    Open Sourcerer, 2003 - 2004
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    Sr. Associate, 2006 - 2010
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Houston, TX
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Makati, Philippines - Three Rivers, TX - Boston, MA - San Antonio, TX
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The Spectacular Too Big Failure of Dodd-Frank
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Not much unites the activist Left and activist Right, and not much ever has.

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Houstonians looking for a quicker way to Big Bend have another option, as Dallas-based Resort Air Services announced nonstop service between

One of our favorite places in the Philippines. The staff was excellent, lacked for nothing. The nearby national parks are grand. Well recommended. Do note this is a "green" resort. Hot water is solar-heated, which may provide a surprise for your morning shower. We look forward to staying here again.
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reviewed 3 months ago
Some of the best customer service I've had in a long time. They had similar products to what I wanted but not exactly. So they looked up the number of a competitor, wrote it down, and offered to call.
Quality: ExcellentAppeal: ExcellentService: Excellent
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The best, of course.
Appeal: ExcellentFacilities: ExcellentService: Excellent
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23 reviews
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Great environment, excellent staff, competitive pricing.
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First class traditional men's business clothing. You pay for quality.
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It really is Tex-Mex like your grandfather ate.
Food: ExcellentDecor: Very GoodService: Excellent
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