Archive for the ‘X-treme physics’ Category

Most likely, the most coveted gadget in Back to the Future II was Marty’s (pink) hoverboard. This is probably why in 2014 the so called HUVr Tech company played a major prank on gullible consumers and, under the motto “The Future has Arrived”, released a commercial where Tony Hawk himself, as well as other celebrities, explained how well their new hoverboard actually worked. The disappointment among eager consumers was so huge that Hawk and the others had to apologize to the public later for their participation in the “joke”.

This is also probably why Hendo Hoverboards talked Hawk into trying their own hoverboard when they went to Kickstarter for funds.

hendo

After the HUVr Tech fiasco, their proposal was probably received with skepticism and it was less than likely that someone would back the 10000 USD to purchase one of their first platforms. However, their Hawk video actually looks more realistic: the hover is almost touching the floor and its not that stable, either.

It’s not like they are going to explain how they do it, but taking into account the platform motion and how the floor looks, the secret beneath might be Lenz’s Law. One might have actually watched a popular science-fair trick: drop a magnet inside a copper tube and its fall will slow down considerably or even stop.

neodymium-magnet-copper-pipe

Lenz’s law states that an induced electromotive force always gives rise to a current whose magnetic field opposes the original change in magnetic flux. The idea is basically that when the magnet falls into the conductor, it generates a current and, hence, a magnetic field, that is bound to oppose the fall of the magnet.

lenz

The only requirement for this effect is that the conductor must be non-magnetic, that is every metal except iron and steel. The best choice to obtain a strong current would be silver, but for obvious reasons one has to do with copper or aluminium (in this order).

Hard core physicians may find a more detailed explanation on how Lenz’s law works on a plane in here.  Unfortunately, a magnet falling slowly through a pipe is not evidence enough than a board will be able to keep your average person on air, right? The trick might be to arrange magnetic fields properly and feed them enough power. And to have a metallic non magnetic floor, too.

Even if they manage to develop this as a product, there are strong limitations to its use, plus its mobility seems to be severely restricted. However, if you have 10000 USD to spare and want to give it a go, here’s their kickstarter. You are on your own, though!

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This was the formal weapon of a Jedi Knight. Not as clumsy or random as a blaster. More skill than simple sight was required for its use. An elegant weapon. It was a symbol as well. Anyone can use a blaster or a fusioncutter—but to use a lightsaber well was a mark of someone a cut above the ordinary.” (Obi Wan Kenobi)

What’s the coolest thing about being a jedi? Guys, I don’t know about you, but I’d totally forego levitation and mind tricks if I could have a light saber.

In fact, there are dozens of flicks out there on the web of everyday people fighting with light sabers. Too bad it works just like in the movies: with post-production. The idea is simple: one gets a stick and fights the usual way. Afterwards, when everything is filmed and digitally stored, here comes a program to replace the stick in every frame with the laser beam. In fact, there are dozens of tutorials on the web about how to manipulate your video using, for example, After Effects.

Although post-processing results are nifty, the downside of it is that combatants can’t actually watch the laser blade until much time later, in a computer. In order to get real time feedback, Augmented Reality may come in handy. In this case, as long as sabers have a recognizable landmark attached, we have a camera equipped processing unit fast enough to process more than 16 frames per second and landmarks are within the field of view of the camera, we are in for a light fight. Optimally, we would need glasses to be able to see what the computer generates. Otherwise we are limited to watching ourselves in a big screen or projection. More frequently than not, though, the camera won’t be able to track your blade unless you are moving frustratingly slow. Kinect Star Wars, for example, works fine, but you will be fighting with a virtual avatar, so you won’t get freaky pics like this one:

lightsaberrealtime

Apparently, it looks like the best way to fight with a light saber would be indeed to build a real light saber. How Stuff Works already proposed some ideas to this respect, but nothing solid. Not as solid as what Harvard Professor of Physics Mikhail Lukin and MIT Professor of Physics Vladan Vuletic, working with colleagues at the Harvard-MIT Center for Ultracold Atoms, have produced, at least.

These guys have created a medium in which photons behave like they have mass, bonding together into a molecule. And, if light gain mass …

Don’t get your hopes too high, though. These “light molecules” are not going to be sold in IKEA anytime soon. As researchers described in a Sept. 25 paper in Nature, in order to merge photons into a molecule, they began by pumping rubidium atoms into a vacuum chamber, then used lasers to cool the cloud of atoms to just a few degrees above absolute zero. Finally, using extremely weak laser pulses, they fired single photons into the cloud of atoms.

Apparently, the photon’s energy excites atoms along its path, and slows dramatically. Like when Jack B Quick speeding ticketed photons, too. As photons move through the cloud, that energy is handed off from atom to atom. Due to the Rydberg blockade, when an atom is excited, nearby atoms cannot be excited to the same degree. This basically means that two photons moving in the cloud at the same time push and pull each other in order to deliver their energy from one atom to the next (right! as if they had mass). All in all, they tend to exit the medium together, all molecule-like.

Although researchers themselves make references to light sabers, the real application domain of this effect would be quantum computing. Thus far, photons are optimal to carry quantum information, but since they don’t interact with each other, processing is kind of tricky.

In any case, if I had to choose between a quantum computer and a light saber, I’d be counting with my fingers for a long, long time.

Source: Harvard Gazette

It’s been a while since scifi showed us space ships with FTL (Faster than light) propulsion so we could get out of the solar system and into any potentially interesting place within our life spans. Given that Proxima Centauri, our best candidate for insterstellar travelling in distance ranking is 4.24 light years away, FTL ships might be our only option. However, how would we keep contact with people on that ship once their cell phones have no network coverage?

This question poses a double problem. First, we need a transmission medium (and possibly repeaters all the way back to ol’ Earth). This is obviously a problem itself if space is yet not colonized, but even if it were, all waveforms in the electromagnetic spectrum travel at light speed, which, in this particular case, might turn out to be quite slow. For example, Mars is usually ranging from 35 million miles away from Earth at it’s nearest to about 340 million miles at its furthest, so an electromagnetic based communication between Mars rovers and NASA may take from 3 to 30 minutes depending on the day. It’s only too good that those robots don’t need to be teleoperated, right?

Obviously, we need FTL communications too, but it’s easier said than done. In fact, scifi has come with a nice heads up for this kind of communication loosely adapting a phenomenon called quantum entanglement to its own needs. For example, in the Mass Effect game franchise from Bioware, EDI explains to Shepard how the Normandy communicates with the galaxy like this:

Despite all the maths, the basic idea under quantum entanglement is fairly simple: if you manage to get two quantums entangled, the actions of one will always reflect the other, despite the distance between them. Just imagine that you could separate yourself from your own shadow, but, still, it would do exactly what you do. If we manage to load that shadow inside a FTL ship and send it to the other side of the galaxy, whenever you raise your hand at home, your shadow would do the same over there, so, voila, instant information transmission or quantum teleportation, whatever you fancy most.

peter-pan

A non-entangled shadow doesn’t work …

Too bad reality doesn’t quite work that way. Indeed, some processes may produce two entangled quantum bits (qubits), meaning that they must present opposite states at all times. Think, for example, of a coin entangled with another one. If we toss ours and it goes heads, somewhere the entangled coin will go tails at the same time. If that coin is light years away, our toss information will have travelled faster than light. Since we know already that digital communications are long sequences of ones and zeroes, we could certainly work with this, but there’s a fundamental flaw in this approach: in order to send information, we must be able to control which side the coin falls every time. Imagine, for example, that we want to send an 8 to the other side, which is equal to 1000 in binary code. We need to toss the coin four times and get one tail and three heads, so the other coin will get the opposite result. The key issue here is that we NEED to toss, there’s no way we can simply set the coin one way or the other due to quantum mechanics: the state of an entangled qubit is always opposite to the other, but we don’t know which state it is until we measure it. Besides, it might be a good time to note that the first entangled quantum state is erased in the process …

Needless to say this communication concept is awfully similar to the famous Ansible in Ender’s game, Le Guin’s novels and even Stargate ancient communication stones, where two pieces of the same material are tangled to react similarly despite their physical distance.
Quantum entanglement has been labelled as teleportation -and used to justify exactly what you’re thinking about in Agents of Shield-, since it sorts of rebuild the quantum structure of a body in a different place, but reset the state of the original set (and, hence, it’s not cloning). Unfortunately, it only works with simple particles yielding only a few quantum states.

In fact, quantum teleportation works (limitedly): an international team led by the Austrian physicist Anton Zeilinger has successfully transmitted quantum states between the two Canary Islands of La Palma and Tenerife, over a distance of 143 km. The key for quantum communication thus far seems to be enabling a conventional communication channel to send in parallel information about the local quantum state, i.e. FTL received data patiently waits in storage 4.24 years to be decoded on Proxima centauri. Obviously, this method is not providing FTL communication any time soon 😦

Quotes


[1] “Light thinks it travels faster than anything but it is wrong. No matter how fast light travels, it finds the darkness has always got there first, and is waiting for it.” Terry Pratchett
[2] “The only things known to go faster than ordinary light is monarchy, according to the philosopher Ly Tin Weedle. He reasoned like this: you can’t have more than one king, and tradition demands that there is no gap between kings, so when a king dies the succession must therefore pass to the heir *instantaneously*. Presumably, he said, there must be some elementary particles — kingons, or possibly queons — that do this job, but of course succession sometimes fails if, in mid-flight, they strike an anti-particle, or republicon. His ambitious plans to use his discovery to send messages, involving the careful torturing of a small king in order to modulate the signal, were never fully expanded because, at that point, the bar closed.” Terry Pratchett