Friday, June 29, 2012

It's hot out there

Photo via Imgur
I used to live in Boulder, Colorado.  Its a gorgeous place.  It seems that every summer now I worry about my friends there and whether or not this will be the year that their houses burn down.  The heat and dry wind seem to be a perfect combination to spread fire.  As you can see from the picture above, there are fires in the mountains above town (not to mention several of my friends and I have lived up in those mountains).  Sparks can easily blow down on to town and start a blaze.  This is just not a good situation.  The video below is a time lapse of this fire developing.


Things look much more dire in Colorado Springs.  I guess it's pretty hot in Arizona too.

via VeryDemotivational
Stay cool out there.

Somebody that I used to Know


There's a haunting little tune by a group called Gotye that has been performed a bajillion bands called "Somebody the I used to know."  One of the most popular covers and a favorite of mine is the video below.

However, a new version just appeared by a guitarist named Mike Dawes.  He performs all the parts himself as a solo instrumental piece.


His skill is apparent from the start, but as the song evolves he starts adding the more interesting little embellishments.  As readers of Digital Diner have read about in the past, I'm attracted to Michael Hedges-type fingerstyle guitar playing.  I think this performance is worth a listen.  Enjoy!


Wednesday, June 27, 2012

Form Follows Purpose

When I lived in Colorado, I used to drive by a little town called Bailey where they had a hot dog shaped building.  I always thought it must be interesting to produce hot dogs in a hot dog shaped building.  I mean someone had to have the idea that they would be able to sell more hot dogs if their building was shaped like one.  Furthermore they had to keep thinking that was a good idea long enough to design and build the building.  In fact, it had to be so compelling that they were willing to overlook the probability that they might have trouble reselling the building later, or that it would make it very difficult to change to a burger joint if the market needs changed.  Its impressive on many levels.

I was reminded of that little building when I saw a whole collection of buildings that represent what is made/sold from within the building.  I particularly liked these:

You probably wont be surprised to find that Longaberger Company, Newark, OH makes baskets.

The public library in Kansas City has a parking lot that looks as if it is made of giant books.

To see all ten buildings, check out the article here:  10 Buildings Shaped Like What They Sell 

Tuesday, June 26, 2012

How do you pronounce Uranus?


I've wondered about this and I'm sure you have too. It's just one more example of how we here at Digital Diner get to the bottom of the issues you care about. 




Thursday, June 21, 2012

New Cooling Technology

When building new faster computers these days, there are two main problems: getting enough power in to the CPU and getting enough heat out.  The folks at Sandia Labs have a solution to the latter problem. They have build a spinning  heatsink that, rather than connecting directly to the CPU as most heatsinks do today, spins just a thousandth of an inch above the CPU.  This creates something called an air bearing that is almost as efficient for transmitting heat as a direct connection.  This system can suck heat out of a CPU 30 times more efficiently than a standard heatsink.  Now that is a cool invention (see what I did there?).


via Gizmodo

Fun with a Slinky


Long long ago, I worked for a company called WaveFrame that build high-end digital audio workstations.  These were basically complete digital studios in a box.  Now days, most of the fancy functions that would run you a quarter million dollars in our device are available on a laptop computer, but at the time it was pretty exciting stuff.  One of the interesting features that the AudioFrame had was a sampler that allowed you to record a sound and then play it back at different pitches on a keyboard.   Almost by accident I found that if you record the sound of an outstretched slinky connected to our office ceiling and then pitch shift it down several octaves (these sorts of things happened in my office during those days, and the AudioFrame was particularly good smoothly pitch-shifting a long way) it turned into a rather fantastically indescribably metallic sound effect.  This sound ended up being included in our sound library.  Our product was used widely in Hollywood, and to this day (25 years later), I still occasionally think I can hear that sound in science fiction movies.  I feel like yelling out in the theater, "Don't be scared!  Its just a Slinky!!" I never do though.

All this is just to say what you already knew.  A Slinky is a wonderful and versatile gadget.  We already know that.  Here on Digital Diner, we've reported on things that can be done with a Slinky in the past.  The video below revisits one of the features of these fine toys to illustrate a feature of physics.  Enjoy.


Tuesday, June 19, 2012

Bedroom Disaster Area



Andy Smith was a seventh-grader in 1984.  He had a problem that many kids his age have encountered.  His room was a mess.  However, unlike other kids his age, he decided to take some drastic measures to help him out of this problem.  He wrote the president of the United States (Ronald Regan at that time) the following letter:

Today my mother declared my bedroom a disaster area. I would like to request federal funds to hire a crew to clean up my room.

Reagan replied with the following letter.
(Source: Reagan: A Life In Letters; Image: Ronald Reagan, via.)

Andy Smith
Irmo, South Carolina
May 11, 1984

Dear Andy:

I'm sorry to be so late in answering your letter but as you know I've been in China and found your letter here upon my return. 

Your application for disaster relief has been duly noted but I must point out one technical problem: the authority declaring the disaster is supposed to make the request. In this case your mother. 

However setting that aside I'll have to point out the larger problem of available funds. This has been a year of disasters, 539 hurricanes as of May 4th and several more since, numerous floods, forest fires, drought in Texas and a number of earthquakes. What I'm getting at is that funds are dangerously low. 

May I make a suggestion? This administration, believing that government has done many things that could better be done by volunteers at the local level, has sponsored a Private Sector Initiative program, calling upon people to practice voluntarism in the solving of a number of local problems. 

Your situation appears to be a natural. I'm sure your mother was fully justified in proclaiming your room a disaster. Therefore you are in an excellent position to launch another volunteer program to go along with the more than 3,000 already underway in our nation—congratulations.

Give my best regards to your mother.

Sincerely, 

Ronald Reagan


Young App Developers


The recent Apple World Wide Developer Conference was the first one to allow in kids as young as 13.  Apparently there are more and more kid developers putting apps on the app store and so Apple decided that they should be able to come to the conference to talk with other developers.  Of course, we've reported on this child developer trend before, but it seems that it is only getting stronger.

The Wall Street Journal has a nice article on the subject here.

Monday, June 18, 2012

Hybrid Car Wins the 24 Hours of Le Mans


I've always been fascinated with the 24 hour car race, Le Mans.  it is an endurance race that can only be won with a combination of speed, reliability and consistency.  When I was a kid, I used to love a rather silly Avalon Hill board game of Le Mans.  You would pick a car and roll the dice to move around the board based on the characteristics of the car you chose.  I know the rest of my family would sometimes complain that the game was dragging on, much like its namesake, but I always liked it.  Then there was the movie Le Mans staring Steve McQueen.  It was pretty intense as a movie for a youngster such as I was at the time, so I'm sure it left and impression as well.
I don't know if it was these experiences or just the excitement of a car race that goes on for 24 hours, but somehow Le Mans has always been interesting to me.  This year was the 80th running of Le Mans and unusually interesting because Audi hybrid vehicles finished first and second.  That is right, they were hybrids.  They aren't like you average Prius or anything, instead, they have a large diesel engine as the main source of power to the rear wheels, and a fly wheel which feeds a supplemental electric motor in the front.  This means that when they brake, the energy goes into the flywheel and when needed, this flywheel drives an electric motor that provides extra power to the front wheels.
Toyota also had a hybrid in the race that was very competitive until it was involved in a rather horrific crash.  Thankfully, the drivers were OK.
Rumor has it that both Audio and Porche are working on flywheel hybrid vehicles for consumers.

More info on
24 hours of Le Mans
Audi at Le Mans
Truth in 24 free movie about Le Mans



Arduinos in Space

It was pretty exciting recently when SpaceX (a private company) was able to build and launch a vehicle to bring supplies to the International Space Station.  Private companies have build spacecraft in the past, but this is the first time that they built and operated the entire project including the launch and recovery. Very nice.
It is really exciting to see how private industry is getting involved in space exploration.  How long do you think it will be until everyday hobbyists can get involved?  Well, that day may have come.



There is a new Kickstarter project to put Arduinos (those cool little development boards that we use to build a lot of projects here at Digital Diner) into a small satellite and send it up to space.  They are packing a set of Arduinos and a bunch of sensors into a 10cm cube called the ArduSat.  Hobbyists like you and I can pay a small fee to take control of the satellite for a week to run our own experiments using the Arduinos and sensors in outer space or just take pictures from some of the onboard cameras.  This is a very cool idea.  Take a look at their pitch in the video below.


Its a pretty interesting project although I have a few questions about its viability.  First, Arduino's aren't the most CPU power per weight or per watt, so I wonder if they are the best choice for this.  Second, some of the sensors that they are using might not be very useful in space.  For example, in the video below they show some sensors connected to an Arduino.  I see there are several sensors from SparkFun that we are quite familiar with.  For example, they mention pressure and temperature sensors, but its not clear to me that either of those will work in space.  At the end of the video, they show an inertial measurement unit (IMU) running what appears to be a sensor fusion algorithm.  However, that algorithm may not work properly in a device that is making rotations around the earth every 90 minutes.  The magnetometer readings would likely be changing much too fast to be able to cancel out drift.  

  
I'm just guessing here, but I think they have a lot of work to do to make a reasonable platform for space.  Still I find the project very compelling and I'd love to see it fly.




See the Kickstarter project here.
Via Dvice

Hokey Pokey's Shakespearian Roots


OK, so maybe Shakespeare didn't write the the Hokey Pokey, but after seeing this, he certainly should have.  Jeff Brechlin apparently created this little gem as part of a contest.  Nicely done.

Via Shakespeare Tonight

Friday, June 15, 2012

9 Year Old Lunch Blogger


A few months ago, a 9 yr old in Ireland started taking pictures of her school lunches and commenting on them.  Martha Payne goes by the name Veg online, and her blog, Never Seconds, shows how unappetizing and unhealthy school lunches can be.  Apparently it struck a chord because within a few weeks she had a million viewers.  The attention got her written up in several places including a few that had some negative things to say about the school.  Well, the school administration did not appreciate this and decided to ban Martha from bringing her camera to school.  Apparently this was a bad idea, because when Martha announced to her blog that she was quitting the blog business, there was outrage and calls of censorship.  In less than a day apparently the school administration has changed their mind and reversed their decision.

It's an interesting story that you can read about here.  Be sure to read through the updates at the bottom of the story that bring you up to date on the latest as the story breaks.

Go get 'em Veg!

via Gizmodo

Thursday, June 14, 2012

When a Brain Scientist has a Stroke


Jill Bolte is a brain scientist who had the unusual experience of studying her own stroke as it happened. She watched as the individual functions of her brain shut down one by one.  Eventually she got to the point where she couldn't tell where she stopped and the rest of the world began.  The result transformed her for the rest of her life.  The experience clearly touched her deeply both scientifically and emotionally.

Some of the more scientific among you may be a little put off by her descriptions of "energies" etc, but if it bothers you, just think it as her way of describing her sensory input.  After all, our senses do sense energy.  Regardless, I think your left brain will find her insights intriguing and your right brain will find her talk moving.

Jill Bolte Taylor's stroke of insight

Thanks David

Wednesday, June 13, 2012

Thread and Nail Portraits


New York artist Kumi Yamashita is working on a project called Constellation that I find pretty fascinating.  It is a series of portraits made by wrapping a single thread around some nails to create dark and light areas that express an image.  The results are pretty fantastic.

The close view
The whole portrait

Tuesday, June 12, 2012

Chicken Waffle Ice Cream


On a recent trip I had chicken waffles for dinner.  It was quite yummy...Just the right amount of sweet and savory, crunch and soft.  Very good.  Well, I was surprised to find that someone is making this into an ice cream flavor.  I think that, if you successfully eat this, it should satisfy your food needs for the entire day.  Just think about it. It has Waffles (brunch), chicken (dinner) and ice cream (dessert).  I think you're pretty much set at that point.

Atomic Clocks and GPS


Ever wonder how an atomic clock keeps time so accurately?  Or how a GPS uses that time to calculate its position?  This video uses jello as a prop to explain exactly that.  There are a few details in there that are glossed over a bit, so I don't think I'll be building my own atomic clock based on this, but I have a better idea of how its done.  I had no idea that they've gotten the guts of those things down to such a small package.

Monday, June 11, 2012

Own Your Own Solar, Floating Resort Island


We have several friends who have just bought houses.  I don't think any of them considered the option of owning their own solar powered, self contained, floating island.  Take a look at the video below to experience it for yourself.


I like the little submerged observation bulb, although I mist say it is a little weird that nowhere in the whole design did I see two chairs that actually face each other to allow for conversation.  But maybe, after you are in your own serene island for long enough you just stare off into the distance and mumble abstract things to each other without ever looking anyone in the eye.  
No word on availability...

Friday, June 8, 2012

Correlation vs Causation


Earlier we posted about a study that showed a correlation between dark chocolate and several health benefits.  Despite what the headlines read, I want to point out that the study showed correlation, not proof of causation.  It does not necessarily mean that eating more dark chocolate will make you healthier any more than sunspots affect skirt lengths or ice cream causes murder (above).  That is preposterous!  Clearly, ice cream does not cause murder.  Murder causes ice cream.  No wait.  That doesn't sound right either.  I guess it's possible that they both correlate to something else, like warm weather.

I'd just like to remind everyone that correlation is not the same as, nor does it imply causation.  Although it is true that causation correlates strongly to correlation, but that really isn't important.

Thank you for your attention.  Now back to your regularly scheduled program.

from G+

Thursday, June 7, 2012

Tide Pools




This morning at 7am the low tide for the day was at -1.4 feet, so we decided to head out to the coast and explore some tide pools.   It was a perfect day for observing sea anemones, sea stars, sea urchins, seaweed, and we even found an abalone shell.  We had the place almost to ourselves until the school bus unloaded eager elementary school kids at 9:30am.   Not shown are the elephant seals that were taking advantage of resting near the tide pools.   More pictures below:

Wind Power


I just learned about a company making a new kind of wind turbine.  The company is called Makani Power and the wind turbines they build are unlike anything else I've ever seen.  They have a flying wing, tethered like a kite to the ground that flies in circles to generate power.  They use 90% less material, can operate over deep water and can access winds at higher altitudes than conventional wind turbines.
I'm thinking that, given global climate change, the fact that these are relatively portable to relocate as conditions change, is a huge plus.

Wednesday, June 6, 2012

Norwegian Tunnels

All the tunnels in Norway as logged by http://www.cycletourer.co.uk/
Some of the potential occupants of
Norweigan Tunnels
If you've ever driven along the coast of Norway, you know that in addition to beautiful fjords, stave churches and lovely people, Norway has a lot of tunnels.  There are over 900 tunnels for roadways.  That works out to approximately one tunnel for every 5500 citizens of Norway.  Lets compare that to the most tunnel-per-capita-state (Alaska) which has approximately one tunnel per 666,000 people - 100 times fewer! There are so many tunnels in Norway that people have created websites just to help cyclists understand what tunnels they are allowed to ride through and which they aren't.



This is what the Lærdal Tunnel looked like when we passed by in June 2000
As you might imagine, after building this many tunnels the Norwegians have gotten pretty good at it.  In fact, they have built the longest roadway tunnel in the world (24.5 km = ~15 mi).  It is the Lærdalstunnelen (Lærdal Tunnel) in Lærdal, Norway.  About 12 years ago, we drove past this tunnel as it was still under construction.  We didn't drive through when we were wandering around Norway last summer either.   However, a fellow named Andrew did drive through it, and posted a video of his experience on YouTube (isn't the web great?).  To make it more bearable, he sped up his film 800% to make it go by a bit more quickly.  I calculate his apparent speed at about 360mph, still, this is a really long tunnel.


Pretty exciting movie eh?  Yeah, well, I really think Andrew should have used the Hall of the Mountain King by Greig for the music, but otherwise... well, there it is... the longest automobile tunnel in the world.  Just one example fo the great stories we bring you here at Digital Diner.

Venus Transit at Digital Diner

I know you are probably tired of hearing about it, but this should be the last post on the subject for about 105 years, so bear with me.  We had a little bit of an impromptu star party yesterday to watch Venus transit across our own star, the Sun.  It was a bit cold and windy, but otherwise pretty good for viewing.  Several friends showed up to watch the skies with us.  We observed the transit several different ways.
Viewing with solar glasses
With solar glasses, Venus was visible, but quite small.  We had two types of solar glasses on hand, one with a traditional filters and the other with more of a blue blocking effect.  Most people liked the traditional ones better, but ultimately it seemed up to individual taste and both showed the action just fine.
A direct photo of Venus taken through solar glasses
The photo above was taken by holding a foil framed, solar glasses lens over the end of the camera lens while taking the shot.  Thank goodness for the immediate feedback of digital cameras.  It made it possible to play around with the manual settings to get the exposure right.

Creating a projection using a spotting scope
The resulting projection was a couple inches in
diameter and clearly showed
Venus (lower left) as well as signs of Sunspots

We created a projection by connecting an old spotting scope (thanks Opa!) to some cardboard and pointing it toward the Sun.  We aimed the light beam emerging from the scope toward a piece of white foam core about 3 feet away.  The result was a projection about 2 inches in diameter that clearly showed the Sun and Venus and hints of some Sunspots [aside: those of you who know me probably understand that I have a hard time keeping from typing "Sun SPOT"]  Because of the magnification, this method worked well even for those who don't have the eagle eyes required to pick Venus out with the solar glasses.

Glenn and his solar filtered telescope
Later, our friend Glenn showed up with a refractor telescope and white light solar filter.  This type of filter is made of Mylar and produces a much more white and blue image.  The telescope produced plenty of magnification, and a nice zoomable eyepiece allowed us to really get an eyeful.  


This view was really breathtaking.  It allowed us to clearly see Venus and also count over 20 sunspots! The detail was incredible.  We didn't have a hydrogen-alpha filter, so we weren't able to watch the dramatic prominences dance over the Sun's surface, but the view was still spectacular.

The Sun as seen through the mylar white light filter.
Venus is in the upper right.  Other dots are sunspots.

Close-up view of Venus and some sunspots

Overall, I think we can mark this off our life list.  We definitely saw Venus transit the Sun.  It is interesting that there are only 3 bodies in our solar system (Mercury, Venus and the Moon - not counting asteroids and comets) that can appear to transit the Sun from our perspective here on Earth.  Mercury is VERY small and unimpressive against the Sun.  We were able to see the other two in the last two weeks while we sat on the front porch of our own Digital Diner.  Awesome!

There is something really cool about looking up in the sky and seeing a planet dangling in front of the Sun.  It makes me think about the great distances, dramatic sizes and the laws of physics they obey that let us predict and observe such events.  I get a confirmation that the Sun really must be huge as I see it in comparison to an entire planet.  Venus really does exist.  It's not just something in text books or on TV.  It's something we can watch from our own yard.  There is so much to learn in the world of science that we often have to just believe things that we are taught, but it is always nice when you can independently confirm some facts from your own direct observations.  Things are as they should be.

Now, to play us out, the Venus Transit March by John Philip Sousa.  Press play on the video below and imagine Venus marching its way through 105 Earth years to the next Sun, Venus, Earth party.  See you in 2117!



PS Thanks to Glenn (for the awesome telescope), Inna, Yuri, Alex, Daniel and Igor for making it a party.





Tuesday, June 5, 2012

There's a Little Black Spot on the Sun Today



Please remember to take a look at the Venus Transit today.  Its the last chance this lifetime.  This may not be quite as dramatic as the eclipse we saw a couple weeks ago, but it is still worth checking out.  If you can't make it outside to see it yourself, you can still join in the festivities by watching a live webcast from some of the world's top observatories.  Check them out here


...as the song goes... "there's a little black spot on the sun today..." - The Police, King of Pain

Monday, June 4, 2012

Eulerian Video Magnification


SIGGRAPH is the anual meeting of the graphics industry.  This is the conference where people show off all the latest techniques for image processing and graphics rendering.  The video above grabbed my eye as something very interesting.  It is a bit technical, but essentially, they take video images and do some time-based analysis to find subtle motions in the video, especially those that are repeating (periodic in nature).  They then accentuate these parts of the video graphically.  In this manner they are able to do things like "see" a pulse in someone's face or wrist.  The videos of these make me a little queazy, but I must say the potential is pretty interesting. Imaging using cameras as sensors to notice structural issues in bridges or to confirm that a baby is breathing properly as it sleeps.  Very interesting stuff given that cameras and processing are getting so cheap.

If you'd like to dive into the geeky details, you can get the paper here.
(BTW, I believe the face that is being color distorted is actually my friend Steve Heller.  Nicely done Steve!)

Sunday, June 3, 2012

Quick! Fly to Hawaii!

Ok, so we were playing around with the real cool transit simulator at http://www.sunaeon.com/venustransit that shows the path Venus will take as viewed from different locations on the planet.  From here at Digital Diner, the path should be something like this:


 It is interesting to see that the path is NOT a straight line across the Sun.  OK, that makes sense.  After all, in addition to the elliptical orbit of Venus (which I believe has little effect on the curve) we are sitting on a planet that is spinning around and so our point of reference is continually changing.
The implication of this is that the shape of this curve will be different from different places on the globe.  In fact, if you were to watch from the north pole, you will find that Venus cuts a nearly straight path across the Sun as shown in the image below.



Ok, so, if it is really straight at the north pole, it must be really curvy near the equator.  After all, at the equator, over the course of the day, your point of view will change by 8000 miles (the diameter of the Earth) that you will not move as you sit relatively still at the north pole.

After we looked at this, we decided to check the view from Hawaii.  Yowza!  Look at that!


It looks like it swerves away from the Sun just before it hits the fiery globe. However, it can't avoid our star and it eventually dives into the interior where it does a loop before being spit out.  What a cool path!  I especially like the fact that it spends a lot of time right near the edge of the Sun.  It makes me think that there will be plenty of opportunities to get interesting pictures like this one:


So, clearly, you should hop on an airplane and head to Hawaii to catch this event first hand.  Fortunately, if you can't make it to Hawaii in person, you can watch it live on the web.  Images will be streaming from NASA EDGE in Mauna Kea, Hawaii.  Take a look at the live feed on the day of the transit.


Venus Transit


Get out your solar glasses.  It's time for another astronomical event involving the Sun!


This Tuesday, June 5, in the afternoon pacific time, Venus will cut directly between us and the Sun.  Just like two weeks ago when the Moon passed in front of the Sun, but instead, this time, it will be the silhouette of Venus that we will see passing across the face of the Sun.  Even though Venus is 3.5 times the larger than the Moon in diameter, because Venus is so much farther away, the silhouette it casts on the Sun will be much smaller.  It is worth your while to catch this event, because its not scheduled to happen again until for another 117 years.  Because of the celestial mechanics involved, the particular event happens twice in rapid succession every 120 years.  The last transit was in 2004.

As always, PLEASE DO NOT LOOK DIRECTLY AT THE SUN!

Here at Digital Diner, the transit will start at 3:06pm and continue to 9:47pm (well after sunset).   The nearly full moon will be rising about an hour later. To find out the exact times of the transit at your location, check out the cool tool here.  It creates a view like the one below which animates the curved path of Venus across the Sun.  The tool requires Flash - sorry iPhone and iPad viewers.  This tool gives similar information.

Please install latest Flash Player to run SunAeon Venus Transit 2012


If you can't make it outside to see it yourself, you can still join in the festivities by watching a live webcast from some of the world's top observatories.  Check them out here

There are plenty more resources for this even out on the web.  Here are a few good ones:
A Great Site Dedicated to the Venus Transit.  More info than you can shake a stick at!
This site includes Info About the Transit Path at Your Location
Sky and Telescope - Your Viewing Guide to the Transit of Venus.
Science.NASA,gov - Venus Transit Info.
SpacePlace.NASA.gov - Venus Crosses the Sun
A Guide to Safely Viewing the Upcoming Transit


Safe Viewing!

Saturday, June 2, 2012

SteadyYo




Yoyo tricks are cool and all, but add some camera tricks and whoa... that's pretty slick.  These folks used some software to adjust the frame of their video to keep the yoyo fixed while some tricks were performed.  The results are pretty cool.


Pico Projector Movies




Perhaps you've seen those tiny little video projectors that are getting small enough to be embedded in cellphones?  They are called pico projectors and they are getting to be pretty interesting. Well, this is a use I hadn't really thought of.  These folks took the elements of a an action film and projected them onto the tables, walls and floors of their house to create a little movie of their own.  Cute idea.

Friday, June 1, 2012

Eat Dark Chocolate Everyday Live Longer.


Great News!  A new study published in the British Medical Journal shows a correlation between eating 100g of dark chocolate per day and lowered blood pressure and lowered cholesterol as well as lowered risk of fatal and non-fatal cardiovascular events.  Not that I needed much convincing, but this sounds great to me.

Read more here:  http://www.futurity.org/top-stories/eat-dark-chocolate-daily-to-protect-heart/

Don't dress like a zebra




OK, any parents out there who are taking their kids to the zoo - Please, please, don't dress your child like a little zebra.  I feel bad for the lion who clearly sees something that looks a lot like dessert but is blocked by the glass wall.
I was thinking of drawing analogies to a "glass ceiling," but I've decided it would be much more effective to ask you to stare at the dessert below and tell me how long it takes before you are trying to bite through the screen.

Image credit: Lotus Head from Johannesburg, Gauteng, South Africa