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On today's Earth, a mysterious cube of no light has appeared, about the size of a house. It's confounding, because it appears to have the mass of stone, by the way it is difficult to move and the impression it makes in the sand. It appears black, but darker - as in it doesn't reflect visible light.

It is a little cool to the touch, and gives the viewer the impression of an optical illusion despite the temperature.

I would like to determine a cause for why it has appeared near the end of the story, that isn't too deus ex machina. Fiction and some hand-waving is fine, but I'd like an interesting and somewhat believable explanation.

EDIT (Additional Information): The background is that this is an object from outer space, which lands near Mecca and is soon an object of Islamic attention, similar to the rock of the dome, but absorbs light.

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    $\begingroup$ An object that reflects no light would tend to be warm as opposed to cold btw. $\endgroup$ – James May 8 '15 at 18:40
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    $\begingroup$ @James Why? It doesn't reflect visible light, but could be entirely reflecting infrared. The absorption of visible light wouldn't be much energy input. Even at room temperature it could feel cold just due to thermal conductivity, like room temperature metal or stone does. $\endgroup$ – Samuel May 8 '15 at 21:28
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    $\begingroup$ @Samuel Absorbing photons puts energy into the object, infra red or not. There actually is a clear precedent for this in the 2001 monolith. At one point the main character does a back of the envelop calculation and decides the object should melt right through his glove it'd be so hot, and yet it isn't hot at all. This leads the main character to assume that there is some unknown thing on the inside sucking the energy away rather than letting it dissipate into heat. $\endgroup$ – Cort Ammon May 8 '15 at 22:13
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    $\begingroup$ @CortAmmon Carbon nanotubes (vantablack) have ten times the thermal conductivity of copper. A block coated with them would cool via conduction with the ground, convection in the air (high surface area), and via infrared radiation (black body radiation). It would remain very near ambient air temperature. The high thermal conductivity would make it feel very cool to the touch. Arguably a better precedent than the fictional monolith. $\endgroup$ – Samuel May 8 '15 at 22:33
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    $\begingroup$ @James may be there is a freezer inside, haha. Why do u assume this object to be just solid body? Maybe it is a complicated device that consumes ebnergy so that to become cool. $\endgroup$ – Anixx May 9 '15 at 10:30
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Vertically aligned carbon nanotubes do an awesome job at soaking up light. Carbon is black to begin with, and by making them stick up like tiny fur, there isn't a flat surface to reflect off of.

And, actually, we've already made it.

As to how they got there? That's really hard to say without writing the whole backstory of the object. But if you want something incredibly black, this is it.

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  • $\begingroup$ +1 because this may be the answer, and I've edited the question to include more information. $\endgroup$ – Mikey May 8 '15 at 18:28
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    $\begingroup$ +1 My favorite part of hearing about that material on NPR (OPB represent) several years ago was when they played the sound clip from This is Spinal Tap. $\endgroup$ – Samuel May 8 '15 at 21:21
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Rex Kerr's answer is correct, but only part of the story. If the cube is expected to stay black for any length of time, it must incorporate some (mumble/handwavium/nanotechnology). The problem of dust has to be dealt with.

Outside of clean rooms, there is always a fairly remarkable amount of dust floating around, much of it silicon dioxide.* This will get trapped on the surface and become visible, degrading the apparent blackness. Apparently, the cube needs active nanotechnology to either swallow dust particles or repel them. Each has its problems. If the cube swallows the particles, what does it do with them? Discretely spit out the day's accumulation when it thinks no one is looking? And if it repels them, how? A sort of cheat might be to claim that only the sides remain dust-free, which would take much less energy/handwaving, while dust which accumulates on the flat top is simply not visible from the ground. If the entire cube is to remain black, the cube must either ingest dust or transport it to the edges and dump it over the side. This will require some very entertaining nanotech.

  • All gems will accumumulate dust during wear, and other than corundum-based (sapphire, ruby), topaz or diamond, with emerald a borderline case, any contact will cause microscopic scratches of the gem's surface, dulling it. Even the hard gems require occasional repolishing if they are worn often.

If the cube lands near Mecca and is slightly cool to the touch AT ALL TIMES, you have a problem. Summer near Mecca is hardly temperate, and the cube is presumably found outdoors, exposed to the sun. To feel cool, regardless of physical temperature, the cube (at least the surface) must have high thermal conductivity. A very high thermal capacity would help, too. This will mitigate the temperature rise during the day and facilitate energy release at night. So it's possible that the "slightly cool" label was applied when the cube was discovered, and was due to the contrast between the constant temperature and the hot surroundings, but it feels warm at night when it is warmer than the surroundings.

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Addressing the issue of the cubes purpose, it is a teaching aid.

It demonstrates some aspect of the universe which we could not learn about from the natural contents and events within our view.
The alien race which has been covertly guiding our species' education, has decided that our next assignment is to figure out this cube. It is a big step for them, since they have had to reveal their presence to some extent. From this point forward, we will know that they are out there guiding us; helping us to unravel the secrets of the universe.

As for what the cube is, and what it is made of, that will depend on the discovery you want it to reveal. For example, the cube might not be absorbing the light. Instead it might be converting the light into gravity, which is why it is difficult to move. Then your protagonist scientist tries to move it at night and finds that it is much easier. Further experiments might find the cube sinking into the ground when high powered spot lights are pointed its way. The big reveal would involve the firing of a laser at it, which is how we discover that it is not just turning light into mass. The laser escalates the cube's gravity well so much that loose items and people are pulled into it, slamming into the cube's wall.

Once the laser stops, the gravity may decrease with time or not.
It is up to you.

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It is obviously a device from the future that turns out to be a nexus location to multiple times. Stepping into it (when the door is finally found) transports a person to another time, but only for a limited amount of time. If they leave the device in the alternate time they must return to it before the deadline or be stranded because the device causes a molecular change that must be maintained for the person or items from one time period to travel back to their own time. Remaining too long in an alternate time makes traveling back to your original time fatal since the aforementioned change is one-way. Altering something a second time destroys it through quark decay.

So you can travel through time for quick visits as long as you return home between trips. Moving from one alternate time to another alternate time makes going home to your own time impossible immediately. No delay required. The closest you could get to your own time after that is within about 50 years before or after. Bummer.

Seems obvious now that you know, right?

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