For Questions That Don't Merit Their Own Thread

[Grand Ship Builder]

Can a Tesla drive on Mars, since it uses electricity rather than oxygen and gasoline? And can you live on Mars, unprotected, inside a Tesla, for at least a hour?

[steve_v]

11 minutes ago, Grand Ship Builder said:

Can a Tesla drive on Mars, since it uses electricity rather than oxygen and gasoline?

Not for long, I expect. While an electric motor doesn't need oxygen, the low pressure and temperature will wreak havoc on everything else. Tyres will explode, lubricants and other fluids will boil, bearings will vacuum-weld, computer components not radiation hardened will fail.
Few things designed for earth-normal conditions work properly in space, and the atmosphere on Mars is so thin as to make little difference.
Designing a vehicle to operate on Mars is not a simple task.

11 minutes ago, Grand Ship Builder said:

can you live on Mars, unprotected, inside a Tesla, for at least a hour?

No. It has no environmental systems at all. Not sure which will kill you first, decompression or hypoxia, but either way it will be quick.

Edited October 8, 2017 by steve_v

[Toonu]

Can we teleport quantum information faster than light? (Not the case of quatum communication with Alice and Bob where they need to communicate at speed of light what to change) Just change one qubit theoretically at midnight and see the changed state instantly 2 LY away at the same time or few mintes after(after measurment of state). When we let them know the time of it and tell the to measure it before that time and after it.

Edited October 8, 2017 by Toonu

[Green Baron]

I want to add to that question:

Is it necessary for quantum entanglement that the two (or more ?) carriers of states were created together from the same source and must not interfere with the surrounding ?

Like, please excuse the naive words, a stick broken in two unequal halves, the halves given to persons that travel to distant places, and if the one looks in his hand he immediately knows if his colleague 2ly away has the short or the long one ?

Does a readout of the state of one "end" of the entanglement destroy the entanglement ?

 

Edited October 8, 2017 by Green Baron

[p1t1o]

19 hours ago, Toonu said:

Can we teleport quantum information faster than light? (Not the case of quatum communication with Alice and Bob where they need to communicate at speed of light what to change) Just change one qubit theoretically at midnight and see the changed state instantly 2 LY away at the same time or few mintes after(after measurment of state). When we let them know the time of it and tell the to measure it before that time and after it.

 

I cannot reproduce the maths that explains it, but if I understand the current state of the art, although "spooky action at a distance" is a real thing, no information can be passed faster than light using quantum entanglement. 

The why of it goes very deep into quantum weirdness and there may still be incomplete or competing theorems in the area, so 100% proof either way on this matter may not currently exist.

However, one thing from the above example stands out - the communication only works if first, information is passed about when to take the measurements. The transmission of information in this manner via entangled qubits is only possible after a prior piece of information is received first, necessarily via other means, necessarily light-speed-limited. Ergo, FTL communication in the described manner certainly is impossible. 

No, apparently there are no clever tricks you can use to get around it. Like giving the receiver a timetable in advance so that they always know when to "check their messages" - this is not FTL communication because there is no way to know when the message is received, and no way to know when it was sent, it is indistinguishable from writing down all messages in advance, and telling the receiver to only read them at the prescribed time.

[Terwin]

IANAPP but I think the biggest problem is that before you measure a particle, you do not know what the outcome will be.

You could use entanglement to generate a shared secret such as 'Measure spin type A from these 3 photons in turn and look up the result-set on this chart to determine which encryption key we will be using for our next message' works fine, and I believe it s currently in use for experimental 'quantum encryption'(probably using a lot more than 3 photons)

But what you cannot do is say 'At 3pm, I will measure this photon, and if I want you to follow plan 1 I will measure Spin Type A, and if I want you to use plan 2 I will measure Spin type B' because you can only measure one spin type before the entanglement is broken.  As each spin type has a 50% chance of being each value if you test the wrong spin type, you cannot tell which one was measured without being able to measure the particle multiple times without collapsing it's wave function(and measuring is *how* you collapse the wave function).  I believe that due to something called 'non duplication' you cannot make half a dozen copies and measure half of them looking at spin type A and half looking at spin type B(which ever type ends up having different results is the one that was not measured) 

 So with only a single measurement being possible, the distant parties cannot know which result will happen for any given measurement, nor can they tell which measurement the other party made.  Thus no information can be transferred.

[Toonu]

4 hours ago, Terwin said:

IANAPP but I think the biggest problem is that before you measure a particle, you do not know what the outcome will be.

You could use entanglement to generate a shared secret such as 'Measure spin type A from these 3 photons in turn and look up the result-set on this chart to determine which encryption key we will be using for our next message' works fine, and I believe it s currently in use for experimental 'quantum encryption'(probably using a lot more than 3 photons)

But what you cannot do is say 'At 3pm, I will measure this photon, and if I want you to follow plan 1 I will measure Spin Type A, and if I want you to use plan 2 I will measure Spin type B' because you can only measure one spin type before the entanglement is broken.  As each spin type has a 50% chance of being each value if you test the wrong spin type, you cannot tell which one was measured without being able to measure the particle multiple times without collapsing it's wave function(and measuring is *how* you collapse the wave function).  I believe that due to something called 'non duplication' you cannot make half a dozen copies and measure half of them looking at spin type A and half looking at spin type B(which ever type ends up having different results is the one that was not measured) 

 So with only a single measurement being possible, the distant parties cannot know which result will happen for any given measurement, nor can they tell which measurement the other party made.  Thus no information can be transferred.

Sorry if I understand it wrong, IANAPP too :D.

If I understand, photons are changing states until we measure the state and then stay at that state, until not looking? (Correct me if wrong, I want to learn more about this)

So even when we don't want to send information, just test it for example with probe sent away with internal clock to measure state of photon, we measure it too at same time, it is same state or not, even faster than light?

)Sorry if I'm dumb :D)

 

[Grand Ship Builder]

Do any other chemicals have a triple point like water?

Edited October 9, 2017 by Grand Ship Builder

[Terwin]

1 hour ago, Toonu said:

Sorry if I understand it wrong, IANAPP too :D.

If I understand, photons are changing states until we measure the state and then stay at that state, until not looking? (Correct me if wrong, I want to learn more about this)

So even when we don't want to send information, just test it for example with probe sent away with internal clock to measure state of photon, we measure it too at same time, it is same state or not, even faster than light?

)Sorry if I'm dumb :D)

 

No worries, it is very weird behavior.

You entangle a pair of photons so that they could have either Spin A(1) or Spin A(2), but whichever they have will be the same, then you send one off to the far side of the galaxy in a probe that will measure Spin A at a pre-set time.

Until either you or your probe measure state A, it will be in a superposition of both A(1) and A(2).  

There are things that can be done to prove that neither particle is in A(1) or A(2), but I am not sure I understand most of them.

But as soon as you measure your photon, or the probe measures it's photon, they both collapse into the same state and will stay that way unless or until something puts them back into a super-positional state(like measuring something else about it)

Here, listen to someone who actually knows what they are talking about:

 

Edited October 9, 2017 by Terwin

[IncongruousGoat]

2 hours ago, Grand Ship Builder said:

Do any other chemicals have a triple point like water?

Yep, all of them(more or less). It's got to do with the way melting and boiling points are affected by  pressure. For any substance, you can shift the melting and boiling points closer together or farther apart by changing the ambient pressure, which means there'll be a pressure at which the boiling and melting points are the same, i.e. the triple point.

There are funky edge cases when you deal with things that have strange phases (Helium-4's triple point, for example, is between the H-I liquid, the H-II superfluid, and helium gas), but by and large everything has a triple point.

Edited October 9, 2017 by IncongruousGoat

[Racescort666]

4 hours ago, IncongruousGoat said:

There are funky edge cases when you deal with things that have strange phases (Helium-4's triple point, for example, is between the H-I liquid, the H-II superfluid, and helium gas)

@Grand Ship Builder, phases described as "solid, liquid, and gas" doesn't necessarily give credit considering the complexity of the matter. @IncongruousGoat mentioned helium liquid phases but there are also the many phases of water ice, 17 according to wikipedia. 

In fact, many alloys also have phase diagrams based on temperature and composition, take this iron-carbon phase diagram for instance: 

It's basically just steel but it shows how the iron/carbide crystals form in the grain structure, this is really important for steel manufacturing and is essential to the strength of steel. In this case, the 0.76% triple point is noteworthy because it is the percentage of carbon that forms eutectoid steel. Carbon dissolves very readily into gamma phase iron and as it is cooled and converts to alpha phase, the alpha phase and carbide form alternating layers. This makes the steel very hard yet still maintain some of its flexibility.

[kerbiloid]

Let me add more drama to the "immediate distant communication" subthread.

If we have two universes — or two distant areas of the same universe separated by googols of light years — in other words absolutely not connected at all.

Living in one of them, we know that another one has mathematical "bit", and obviously it is same as our bits.

That means, we know all about their binary maths, so about their linear algebra, etc.
In fact we know all about their mathematics, as it is same everywhere.

As originally we presumed that we are Jon Snow know nothing about them, this means that studying our own universe we get information about inaccessible places far beyond any light speed limits, and even physically inaccessible at all.
I.e. we get information about them with FTL ludicrous speed _{(thanks, Spaceballs)}.

The only thing we can't say exactly are numerical values of coefficients translating their maths to their physx, compared to ours.

(This btw means that all possibly existing universes are a connected system, multiverse or so.)

Edited October 10, 2017 by kerbiloid

[shynung]

Suppose that you have a reusable rocket stage in orbit with a known engine ISP and remaining deltaV in its tanks, calculated from its previous payload of known mass. You want to attach a new payload of a given mass to this stage without refueling it. How do you calculate the combined stack's deltaV capacity?

[kerbiloid]

You should additionally know any of your rocket current masses: either total, or dry, or fuel.
After calculating from it both dry and fuel masses, add your new payload to the dry mass and recalculate delta-V.

***

k = exp(RemainingDeltaV/ISP);

/*  Mtotal/Mdry = (Mdry+Mfuel)/Mdry = 1 + Mfuel / Mdry = k;  */

***

• Given: current total mass Mtotal (say, trying to rotate your ship and measuring its angular moment, (upd.) or making quick prograde-retrogade burn and measuring T/W).

Mdry = Mtotal / k;
Mfuel = Mtotal - Mdry;

• Given: current fuel mass Mfuel (say, from sensors or calculating its spent part).

Mdry = Mfuel / (k - 1);

• Given: dry mass Mdry (from the flight plan specification).

Mfuel = Mdry(k - 1);

***

All cases:

NewDeltaV = ISP * ln((Mdry + Mfuel + Mnew) / (Mdry + Mnew))
= ISP * ln(1 + Mfuel / (Mdry + Mnew));

Edited October 10, 2017 by kerbiloid

[p1t1o]

1 hour ago, shynung said:

Suppose that you have a reusable rocket stage in orbit with a known engine ISP and remaining deltaV in its tanks, calculated from its previous payload of known mass. You want to attach a new payload of a given mass to this stage without refueling it. How do you calculate the combined stack's deltaV capacity?

There is a quick+easy way to get rough figures, but if you want accuracy you google "rocket impulse calculator" because there a log term in there that is tricky to do by hand

http://www.quantumg.net/rocketeq.html

*edit*

ninj'd by someone with the actual maths!

 

Edited October 10, 2017 by p1t1o

[Grand Ship Builder]

I want a cinnamon roll.

[kerbiloid]

There are at least two proper threads for your wish

Though, they are out of cinnamon rolls. Only cinnawon yaws and cinnamon pitches.

[p1t1o]

1 hour ago, kerbiloid said:

Though, they are out of cinnamon rolls. Only cinnawon yaws and cinnamon pitches.

They have Dutch Rolls , but Im not sure if they have cinnamon in them.

[SaturnianBlue]

Though not a question, I don't really think his would be worthy of a thread, so I put it here.

I was reading this paragraph from an Astronomy Now article of KIC 8462852, when something just made so much sense to me.

"Based on the strong ultraviolet dip, the researchers determined the blocking particles must be bigger than interstellar dust, small grains that could be located anywhere between Earth and the star. Such small particles could not remain in orbit around the star because pressure from its starlight would drive them farther into space. Dust that orbits a star, called circumstellar dust, is not so small it would fly away, but also not big enough to uniformly block light in all wavelengths. This is currently considered the best explanation, although others are possible."

Of course! Astronomers can find out was is blocking out light by finding which wavelengths are passing through, because that allows them to know the size of the individual bits!

Edited October 11, 2017 by SaturnianBlue

[Green Baron]

11 hours ago, SaturnianBlue said:

*snip*

Hi,

i linked the paper astronomy now cites from in the *sigh* "Megastructure" thread on KIC8472whatsoever :-)

https://forum.kerbalspaceprogram.com/index.php?/topic/123078-astronomers-may-have-found-giant-alien-megastructures-orbiting-a-star-in-the-milky-way/&page=16

 

Edited October 12, 2017 by Green Baron

[raxo2222]

What would happen if I fired 1 kW or even 1 MW laser into glass fiber or prism?

I don't think total internal reflection is 100% efficient.... would it heat up and melt?

[p1t1o]

2 hours ago, raxo2222 said:

What would happen if I fired 1 kW or even 1 MW laser into glass fiber or prism?

I don't think total internal reflection is 100% efficient.... would it heat up and melt?

Yup, with sufficient power that is exactly what would happen, its less about the refraction, more just about travelling through a medium that is not perfectly transparent - a percentage of the energy is absorbed, to a greater or lesser degree depending on the frequency and properties of the medium. And as with most things, there will be examples at either extreme.

[Terwin]

17 hours ago, raxo2222 said:

What would happen if I fired 1 kW or even 1 MW laser into glass fiber or prism?

I don't think total internal reflection is 100% efficient.... would it heat up and melt?

Search youtube for 'fiber optic fuses'

Basically an imperfection in the cable heats up, damaging the cable further, then it propagates back to the beam source as the heat damages bits of cable further and further up-stream.

[Toonu]

I saw fire extinguisher, which extinguish the fire by sound a long time ago. Have anyone any news on it? If development is still ongoing or not?

[Codraroll]

So, Google Maps has updated with some pretty high-res images of the Gale Crater on Mars, where the Curiosity rover is currently rolling around. However, despite my best efforts, and a pretty good map that shows the exact route of the rover, I have been unable to locate the thing itself. My best guess is a shadow that seems to have roughly the right size, position, and shape, but without pareidolia goggles it looks a lot like a regular rock. Is it possible to check whether those images were taken before the rover even arrived (it makes perfect sense that pre-landing images were taken aplenty - they wouldn't send the rover there without plenty of things for it to have a closer look at), or if they are taken later, where its exact location is? It should be big enough to be clearly visible at that level of imagery, and be a pretty cool landmark to look at.

Thanks in advance! Eventual imagery showing any of the other Mars landers would also be very welcome!