Telepresence Technologies

In a globally connected world, it's harder than ever to "be there" without actually being there. Voice Over Internet Protocol (VOIP) and video over internet allowed families to connect from far away over technologies like FaceTime and Skype (among many).

Telepresence is a set of technologies intending to increase that sense of being present in a remote (or even completely unreal) environment. As you can imagine, such a broad goal has created some very different ideas. 

Immersive Telepresence

Immersive telepresence technologies connect one or more people in a completely simulated world. Imagine any massively multiplayer online (MMO) game you've ever seen. Or Minecraft for examples of people working together toward a common goal in a completely virtual world.

Augmented Reality

You may have seen augmented reality technologies that work by mapping elements in a virtual world to a position in the real world. A see-through screen or camera captures live and virtual elements putting them together. 

Robotic Telepresence

iRobot, the company that gave you robotic vacuums and mops that navigate your home is also working on solutions to allow you to roam an open space remotely. Called the Ava 500, the robot is what you might currently expect from teleconference technology - picture and sound. Where this innovates is that the camera, screen, speaker, and microphone are mounted on a simple robot. This allows the visitor to roam, squeeze in for a better look, and do many other things that watching from a fixed camera angle simply doesn't allow.

Holographic Telepresence

Long a goal from science fiction movies and television, Cisco is featuring stage holograms very much like you've seen on television.

Could the Tower of Babel Actually Stand

This excellent question on Worldbuilding Stack Exchange asks if the tower of Babel, as it is described could actually stand.

I guess there are several questions to consider when trying to answer this.

Could Ancient People Have Drawn Straight Lines Tens of Kilometers in Length?

The Nazca lines were up to 370 meters long, and could achieve surprisingly complex patterns. One of the hypotheses for how they did this was by drawing in a valley and having construction managers spotting from higher elevation.

Could a Multi-Kilometer Structure be Kept Level?

Egyptians (almost a contemporary) had sight levels consisting of a plumb line and a triangle on a table. Look here for an example.

Wooden sticks, marked at a common desired height, with string run between them was the technique used to level the pyramid. The sticks were initially sighted with the sight level, and reviewed periodically by construction site managers.

Between the two base lengths given (2.6 km and 52.5 km), the curvature of the Earth would be between 2 and 53 meters. This curvature would foil the plumb lines, as gravity is curving with the Earth. However, the alignment and design of the pyramid also indicates that the curvature of the Earth was not unknown, and near contemporaries had calculated the circumference, and thus radius, of the Earth accurately, so it would be possible for building site managers to pre-calculate the curvature and account for this 2 to 53 meter curvature that would happen at these very large dimensions.

Are There Physical Limitations to Such a Large Height and Width?

There would be some side force, due to the curvature at the very largest dimensions. To calculate angle, get the arctan of the drop (53 meters) and half the base (26 km ~ 26,000 m) = 0.11 degrees. To find the percentage of all force that is transmitted as a side force, use the sine of this angle.

At the largest dimension (52.5 km) you mentioned, this side force would be about 0.19% of the weight is being transmitted as a moment trying to crack the structure apart.

Tensile strength of mud bricks (which is the type of strength that applies here) 1.5 MPa for mud bricks and 15 MPa for fired clay bricks (same as it's compressive strength). The density of mud brick is 1520 kg/m-cubed; for fired clay brick 2000 kg/m-cubed.

Geometery (whether this tower tapers as it gets higher or is straight up) plays a very important part in total load. For a straight up tower, the total pressure on the bottom tier is the density of your brick multiplied by the structure's height (in meters). P = rho * g * height * 0.2% (the amount of load being transferred)

So, at what height would this set-up fail? 390 kilometers for fired clay brick; 52 kilometers for mud brick.

Also, since brick is not a solid piece, some of this pressure would be absorbed by the bricks shifting in the mortar. And the case mentioned was for a vertical tower - the load could be greatly reduced by tapering the structure as it rose to the top.

How About Maximum Height?

The crushing strength of modern bricks are between 3.5 to 50 MPa. Mud bricks are 1.5 MPa and fired clay bricks are about 15 MPa. The equation, for a straight tower is still that the pressure on the bottom tier P = rho * g * h

For mud brick, the highest altitude before mud bricks start crumbling is 100 meters; for fired clay bricks 750 meters; for modern bricks 2.5 kilometers. This does not include a factor of safety - normally you'd cut these values by 4x to 5x for safety. Again, you could taper the structure to reach greater heights.

For comparsion, the ziggurat of Ur stands at 45 meters and the great pyramid stands at 139 meters.

How High is High Enough?

Per here, altitude sickness begins to set in at 2,500 meters height. Also, per the same site, the highest altitude a human can reach without a compressed air supply is only 8,000 meters.

How Much Height Can We Squeeze Out of Tapering?

The advantage of such an impossibly large base is that you can do a LOT of tapering. With the largest base of 52 km, reaching altitude sickness @ 2.5 km an extremely gentle 5 degree slope (an 85 degree taper). To reach the highest possible altitude for humans @ 8km is a not-terrible 17 degree slope (73 degree taper).

At such a shallow angle, you're not really building a structure (I guess you still are), but merely piling up a mountain. If you could effectively keep the pressure distributed, only 9% to 30% of the total force is being communicated down to the bottom layer. That would allow a height of 1,000 meters for mud brick; 4,400 meters for fired brick at a 10 degree incline; and 8 km for modern brick. You would still want a factor of safety for the structure. Then again, maybe not, because this thing is so shallow.

Effects of Wind

Wind adds a small amount of pressure to the stack. The density of wind is 1.225 kg/cubic meter. A 60 mile per hour wind would add 440 Pascals, and this is without including the effects of the shallow slope.

Breakdown Mode

At these very shallow slopes, the tower wouldn't fall down when it breaks. The failure mode would be more like erosion. Failure can be controlled the same way we control erosion with retention walls made of piled-up dirt, wood, or bronze.

So, I'm really surprised by this, but it's possible.

What’s New with Mars One?

Started in 2011 Mars One has been a science fiction fan's dream come true. As private endeavor, recruiting from the public, with an aggressive timeline, it has everything a dreamer of alien worlds could hope for.

But in the intervening years, Mars One has endured a great deal of criticism - about the feasibility of its plan, about it's down selection process of recruits, the projected cost of the endeavor, and the progress of fundraising efforts compared to it's timeline.

Mars One has presented an updated plan to collect funding and major spending milestones along the way.

Human Machine Interface Enables Vision

In June 2015 doctors at the Manchester Royal Eye Hospital implant a chip, called the Argus II developed by U.S. firm Second Sight to help relieve age-related macular degeneration (AMD).  The implant has been used previously to treat retinitis pigmentosa, a genetic disorder that causes gradual loss of sight.

The system works by means of a camera mounted on a pair of eye glasses, which transmits the captured image to the implant. The implant then stimulates the retina, passing along the information.

Extreme Close-up Images of Pluto

At 5.3 light hours distance from the sun, Pluto is thought of as a comet or errant ice ball. In fact, in 2006, Pluto was re-classified as not a planet at all, but a new category of celestial object called a dwarf planet.

Images are still being processed and studied from the New Horizons probe. Launched in 2006, the probe flew close to the dwarf planet in 2015. At that great distance, the last images from the flyby weren't received until 2016. The probe will continue flying into the cloud of ice and rock that surrounds the solar system like a halo.

The images received show mountains, valleys, eroded pits, cracks, and wavelike dunes across the plains. Conventional geology doesn't make sense on a world that should be frozen solid with neither tectonic forces to drive up mountains or drive apart plates, nor a wind to pile up dust or snow into neat dunes.