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Space-Time Cloak Could Hide Actual Events
An anonymous reader writes "My first thought was, a hypothetical space-time invisibility cloak? That must be what hypothetical crime-fighting Einstein wears when he wades into the fray! Sadly, the researchers who thought up this trick to 'hide events' say that the metamaterials we have on hand will only allow for a nanoscale demonstration at best."
I will post my reply using my spacetime browser but you won't see it until several nanoseconds later!
When the foot seeks the place of the head, the line is crossed. Know your place. Keep your place. Be a shoe.
I tried the same thing, but I must have broken one of my many mirrors...
mwahaha! if i'm never a part of events intersecting the light cone i dont exist!
oh shiii-
Ice Cream has no bones.
all fine until the spacetime moderators show up.
rewriting history since 2109
Ooooo how do I get that type of mod points?
You are entitled to your own opinions, not your own facts.
Indeed, things usually take a turn for the worse when a pissed of Jean Claude Van Damme comes knocking on your door.
Maybe we just can't see the ones that get it right.
rewriting history since 2109
The seminal work on this was produced in the UK in the late 60's or early 70's, and shown on the PBS network in the USA, who frequently interrupted the program to beg for money: http://en.wikipedia.org/wiki/How_Not_to_Be_Seen
Schroedinger's Brexit: The UK is both in and out of the EU at the same time!
"A safe cracker would be able, for a brief time, to enter a scene, open the safe, remove its contents, close the door and exit the scene, whilst the record of a surveillance camera apparently showed that the safe door was closed all the time,"
So it's a way of hiding something in time, without anyone really knowing anything is being hidden.
I found another article about the article which makes more sense: http://physicsworld.com/cws/article/news/44320
There is a chicken and car analogy that should appeal to the crowd here:
An analogy, says McCall, is a chicken crossing a busy road. Once the chicken steps onto the road cars must stop to let it pass, but as soon as it leaves the other side the cars would accelerate to catch up with the traffic ahead. To an observer farther down the road, the stream of passing cars would display no evidence of having slowed down.
So, there is no magical disappearing of time or events or 4D cloaking of spacetime. That's just bullshit from some journalist who doesn't understand what spacetime or 4D means... Not more than a recorded tv program is cloaking space time.
I thought a safe cracker was one without tuna.
I'll believe it when I don't see it!
Even though it's a joke it's probably not far from the truth. A dry scientific explanation is never going to make front-page on the millions of blogs, while "INVISIBILITY CLOAK NOW MONTHS AWAY!" is a shoe-in (unfortunately). Of course, you also then get a subset of scientists overstating their case to garner exactly this response, which doesn't help matters at all.
Ahhh! So you spotted that massive plot hole in the Harry Potter films too ;).
Reply to articles not yet created. -1 Reply to articles on websites not yet created -10 Reply to articles on websites on an internet not yet created -existence Erasure from existence is one hell of a ban.
Why do you think after the second book they no longer care which house wins. Griffendorf keeps on getting a bunch of points taken away do to slipping accidents in the girls dorms.
If something is so important that you feel the need to post it on the internet... It probably isn't that important.
The first question I had is how they are going to speed light up beyond the speed of light? I know it's theoretically possible for that to happen around gravity wells from black holes as they drag actual space-time around the event horizon, but how would they do this with a piece of fabric regardless of the machinery embedded in it?
Light isnt sped up going around black holes, though it is red-shifted.
You have to get a post before the fr1st p0st!
WTF am I doing replying to an AC at 5 A.M on a Friday night?
Yes, in principle if photons had mass that could lead to something like dark matter.
However, in practice we know this isn't the case. First of all, if photons had mass (and quantum mechanics as we understand is roughly correct), this would modify a whole slew of predictions in all kinds of bizarre ways (down to fundamental things like the number of particles we observe and the stability of matter). Basically, the only way to match all our experimental data is with a massless photon.
Even beyond that, however, the measured distribution of dark matter (which we can infer based on things like galactic rotation, gravitational lensing, large-scale structure in the universe, etc.) does not match the measured distribution of photons (which we can calculate based on the positions of known light-emitters, like stars).
It's a neat idea, but appears not to be the case in our universe.
It's all relative. Actually it is sped up, but not in the way you think. They've found that if a gravity well is strong enough, it actually pulls spacetime around it. If you were to shine a beam of light while based on spacetime that is moving, you in essence create a beam of light that is moving faster than the speed of light, at least for an observer standing on spacetime that is not moving.
If photons did have mass then they wouldn't be traveling the speed of light. The speed of light would still be a constant, but light wouldn't actually travel at that speed. As far as an alternative to dark matter, I'm not really qualified to answer that. According to wikipedia the upper bound for the mass of a photon is 1 x 10^(-18) eV/c^2 which is miniscule. For reference an electron has a mass of about .5 MeV/c^2. Considering dark matter is supposed to take up 80% of all matter in the viewable universe, I'd have to guess no. Like I said though, I'm not a physicist so take this with a grain of salt.
No - photons cannot account for the "missing mass". It's called "dark matter" because we know that it (whatever it is) does not interact with the electromagnetic force.
Indirectly, we can experimentally confirm that photons have a rest mass of zero from the fact that unless EM is exactly inverse square then there would be an electric field inside a hollow conductor. (proving this is relatively straight forward for a perfect sphere - I understand that it can be proved for a general closed conductor but that's maths far beyond what I'm capable of)
http://personal.rhul.ac.uk/UHAP/027/PH2420/PH2420_files/notes/04.pdf (page 6)
Basically it's a galvanometer connected between an isolated conductor that is inside a closed conductor and the closed conductor. The conductor is then driven with a few kV at the resonant frequency of the galvanometer. Any deflection at all would indicate that EM isn't exactly inverse square and one possible explanation would be that photons do not propogate at c.
However, any result like this would be so disruptive to all known physics that pretty much every physicist would assume that there was a fault with the experiment.
Tim.
God said, "div D = rho, div B = 0, curl E = -@B/@t, curl H = J + @D/@t," and there was light.