It's unclear what you mean by "interaction."

Any exchange of energy.

imagine taking a positively charged probe and flying an electron past it. The electromagnetic interaction between electron and probe will be present the entire time the electron is flying past it (and according to Coulomb's law, it's always present, just screened sometimes). So the interaction is demonstrably not instantaneous in this case

I would think the interaction between the electron and the field would be photon-per-photon instead of smooth and continuous. By instantaneous interaction I mean that an interaction itself takes an infinite small amount of time. More explicitly, once they meet, no time passes between the start and the end of the transfer of energy between the photon and the electron.

Physical properties of particles are invariant with regards to effects of time dilation or other relativistic effects. The muons do not need some internal clock to know when to decay. The chance of it decaying is constant per unit of time but of course only when measured in its own reference frame. If the muon moves at relativistic speeds, it will seem as if it takes longer to decay for a stationary observer, but from the viewpoint of the muon, the chance of decaying per unit of time has not changed. I would think this is pretty basic physics but perhaps I am missing something?

I'll keep an eye on the thread in case you reply.

But over an average of many observations, the path of a particle is seen to be able to be obstructed and prevent the interaction from occuring where it would have had there not been an obstruction, i.e. shadows cast by objects blocking light sources.

In between two interactions, the particle does not interact*, once it interacts it is with the closest particle that happens to be in its path. The real question is: what happens during the time that we experience to pass as an observer in between two interactions. Is that electron really present in the space during the time when it travels from point A to point B? There is no way to tell, since verifying whether the electron is present requires an interaction with the electron.

Also, radiation is proven to take time to traverse space, i.e. when communicating with a satellite.

Time is observed to pass between the interactions with the earth and satellite antennas. However, a photon travelling between the antennas has not experienced any passing of time as photons travel with the speed of light. The question is: have the photons travelled in the space between the antennas, or did the photons jump from one antenna to the other, somehow "knowing" that there is no obstacle in their path? If this seems strange, then realize that in the double slit experiment, something similar happens: a photon somehow "sees" whether there is one or there are two slits, and continues its path like a wave (two slits) or a particle (one slit) after passing the slits. It can not be explained how a single photon can "know" the presence of the two slits, which can be multiple wavelengths apart from each other.

Gravity does interact with particles at any point in their path. Photons are bend around stars, for instance. However, gravity does not collapse the waveform, and this being the case, interactions of a particle with gravity can not be used to glean for instance path information of a photon in a double slit experiment. The interaction between particle and gravity therefore must be fundamentally different from interaction between two elementary particles. I can therefore make the prediction that gravity is not the result of particle or field interaction, but actually the result of a different, not yet understood phenomena. Also, I herewith predict that the Higgs boson is not responsible for giving mass to particles.

*Except for interactions with virtual particles, but since these interactions are impossible to observe without another interaction, the interpretation of space and time being emergent holds.

Thanks for the very interesting comments.

@1 (decay of elementary particles): I note that it can not be predicted for a single elementary particle when it will decay. The amount of time that the particle has existed does not help to more accurately the moment it will decay, i.e., it is martingale with respect to the amount of time passed. Just with heads or tails: five times heads in a row makes no predictions of what side comes up next. Therefore, I believe that experiencing passage of time by an elementary particle is not required for it to be able to decay. At any moment in time, the chance of it decaying is equal.

@2 (philosophical remark): The axioms make indeed the same predictions about the universe we see. You can therefore also see the axioms as a means of showing that an interesting alternate interpretation of space and time exists, one where these concepts are emergent instead of fundamental. What it does predict, however, is that a deeper fundamental reality must exist, and that we have been looking at space and time in the wrong way all along, just as the article suggests.

One of the things the article says is that space and time may not be fundamental properties of nature, but properties that emerge (i.e., are the result of) a more fundamental reality.

Warning: IANAP. But with some axioms, it is possible to reach the same conclusion.

Imagine a simple experiment with an electron source and a detector. An electron is emitted in the direction of a detector. The experiment is set up such that while travelling towards the detector, the electron does not interact. More precisely, in between the emitter and the detector, the electron does not exchange any energy. Then, the electron hits the detector and becomes detected (interaction two).

Has the electron physically travelled in the space between the electron source and the detector? May it be assumed that in between the interaction with the emitter and its subsequent interaction with the detector the electron is physically present?

Obviously, it is impossible to establish that the electron is present between the emitter and the detector without actually interacting with the electron. It is therefore herewith observed that any assumptions about physical presence of the electron in between the source and the detector can not be experimentally verified. More generally, it is observed that the assumption of physical presence of any elementary particle in between two interactions can not be falsified.

Equally impossible to falsify is the assumption that in between the emitter and the detector, the electron in the experiment was not physically present. This assumption implies that (in the reference frame of the observer) the electron disappeared at the emitter and reappeared at the detector, and did not take up any physical space at any time in between. In between interactions, the representation of the electron disappeared and became unobservable. For as far as an observer can tell, the electron disappeared from the universe completely in between interactions.

Since obviously, properties about the electron are preserved in between interactions, the electron must still somehow being represented – i.e., the representation of the electron has clearly not disappeared from the universe.

The notion “observable universe” is therefore being introduced to make the distinction between interactions which can be observed, and the herewith theorized part of the universe that is apparently capable of at least holding a representation of an elementary particle and which can not be observed.

Observable universe: The part of the universe in which an interaction manifests itself.

Let us formulate the following two axioms:

Axiom 1: An interaction is instantaneous, i.e., it lasts for an infinitely small amount of time.
Axiom 2: An elementary particle only exists in the observable universe at the moment of its interaction.

Notice that axiom 1 and 2 are unfalsifiable. Consider the reverse of axiom 2:

Reverse of Axiom 2: An elementary particle physically exists in the observable universe in the time that passes (in the reference frame of an observer) between two interactions.

This axiom is equally unfalsifiable, since physical presence of an elementary particle can only be proven by interacting with it. The reverse of axiom 1, which would postulate that an interaction lasts a non-zero amount of time, is equally unfalsifiable.

Elementary particles have no internal structure and are considered point particles. In other words, an elementary particle does not take up any physical space. If we assume that everything in the observable universe consists of elementary particles, then it follows that all particles that exist in the universe do not take up any space. The aggregate volume of all elementary particles is zero.

Combined, axioms 1 and 2 state that in between two interactions, an elementary particle is not present in the observable universe. A particle only manifests itself the instant moment it interacts, becoming part of the observable universe for an infinitely small amount of time, in an infinitely small amount of space.
Two more unfalsifiable axioms are now introduced:

Axiom 3: From the reference frame of an elementary particle, no time passes during an interaction.
Axiom 4: From the reference frame of an elementary particle, no time passes in between two subsequent interactions.

Combined, axioms 3 and 4 state that elementary particles do not experience any passing of time. Notice that again, axioms 3 and 4, as well as their reverses, are unfalsifiable.

For every elementary particle, these axioms say that a particle only exists in the observable universe for an infinite small amount of time and only when it interacts. It follows then, that the observable universe is a succession of momentary interactions that themselves do not take up any space or time.

From here, it can be concluded that it is not possible to disprove that space and time do not exist. From the axioms, each of them impossible to disprove, it follows that space and time are emergent properties of a more fundamental reality.

But, again, IANAP, perhaps it shows, but I just like to think about these things and would welcome any feedback, even if it demonstrates the above is complete nonsense.

My idea of the perfect cable:

Four strands, two copper, two fiber.
The two fiber strands enable redundancy (ring topology all the way to the end-point);
The two copper strands for being able to provide power to devices.

That's it. That's all that's needed.

The math behind quantum physics and relativity is of secondary importance compared to the phenomena they predict and define. Einstein had the insight that everything must be relative, and the math followed from that. Mathematicians merely model nature based on existing insights. But it are these insights that create new science and discoveries, and not the math that models them.

The judge should complain to the law makers.

Quoting linked w3.org page:

Obl. xkcd

Against the .

Why is RGB used for filtering at all? Wouldn't it be better to use the inverse (i.e., CMY or no-red, no-green, no-blue) instead? Wouldn't that allow twice as much light to pass through? I must be missing something obvious, someone care to explain what I am missing here?

Wind, temperature changes and radiation from the sun pretty much define the weather on Mars. Any changes to the chemical composition on the rock surface will be due to these factors. Therefore don't expect anything exciting.

Let me guess. Inside of rock is chemically exactly the same as its surface. At least, that is what I would expect since the rocks eroded.

Why do people think getting rid of the mouse is a good idea but getting rid of the keyboard is not? If touchscreens are so marvelous lets ditch keyboards too!
There's actually quite a market for tablets, in case you haven't noticed.

Obviously W8 is a complete disaster but having a touch screen on a laptop can be nice when implemented correctly. Ergonomically, it makes a lot of sense actually. I compared the strain on my arm when swiping my fingers across the screen of my laptop and when using the mouse. When I rest my elbow in front of the laptop, the strain on my arm is even less then when using a mouse, because when using a mouse I have to retract my arm and can only support the weight of my arm with my hand. When touching my screen, I barely have to move my arm. I move my hand slightly forward and I am able to touch my screen anywhere. Another big bonus is the directness. Using a mouse goes like: looking-for-mouse; move-hand-to-mouse; moving-mouse-pointer-to-correct-screen-location, clicking-mouse-button. With a touch screen I can simply: move arm 10 centimeters forward; press whatever I want on the screen with my finger. It's just more convenient and faster.

But it would be a mistake to use the same UI which was designed for use by a mouse as a touch-screen UI. If a user interacts with the UI using the touch screen, UI elements like menus should be larger and behave differently than when they are accessed with a mouse. For example, scrolling a page could be a swipe on the screen, but using a mouse a swipe would be awkward. Specifically, the mouse paradigm where you move a little pointer on the screen and press a button must not be copied to the touch-screen paradigm, such that pressing a finger on the screen is equivalent for the OS a mouse-button press. Such an implementation would be disastrous. Instead, the UI should adapt to larger fingers, be less picky on where someone lands his fingers, and use larger, dynamically appearing GUI elements so users can see what they are doing, as their hand and fingers are now in front of the screen. And use swipe gestures. Lots.

I think laptops with touch screens are the future, but I suppose it will take some iterations before Microsoft and Apple understand the differences and optimize their GUIs for use by touch screen as input device. In the mean time, creating a single UI for both mouse and touch-screen input is plain dumb and a waste of effort.

This is brilliant. Hope my company adopts this as quickly as possible. I don't have time to read time wasting work-related mails at my job. In case you missed it it's the season and I have my hands full doing on-line shopping and hunting down coupon codes. I already hardly have any time left to read the frickin' news sites. And I guess if you think your mail is so important, just put a request at the bottom to consider forwarding it to the next member of the department or project team, so each person who receives it can make a balanced decision whether to bother a next person with your mail, that interferes with other priorities.