Ask a physicist anything. (3)

[Wiccan_Child]

Would that not violate general relativity?

General Relativity can take a hike .

 

[Nabobalis]

General Relativity can take a hike .

Well not before I learn it this year

You might want to look at the Quantum Mechanics and God thread if your bored and want to debunk a 9 minutes video.​

 

[Chesterton]

Do you have any objection to the idea of computational irreducibility, i.e., that it is not possible to even approximate a system state without a full simulation of all the events occurring in the system? I suspect you might, but I'd like to hear what it is. It seems like common sense to me.

 

[Wiccan_Child]

Well not before I learn it this year

Hah, just ask your lecturers how they reconcile the contradictions between GR and QM! The size of a black hole's singularity is different in both models. Physicists generally err on the side of QM, since it's prettier.

And, my reply was a bit glib; AV1611VET is infamous for his 'Science can take a hike', which you will probably see if you stick around

You might want to look at the Quantum Mechanics and God thread if your bored and want to debunk a 9 minutes video.

I have a thread like that over in Exploring Christianity. It's fun stuff, I'll check it out.

 

[Wiccan_Child]

Do you have any objection to the idea of computational irreducibility, i.e., that it is not possible to even approximate a system state without a full simulation of all the events occurring in the system? I suspect you might, but I'd like to hear what it is. It seems like common sense to me.

I object to it because we can, quite readily, approximate a system without fully simulating all events occurring therein. For example, we can model fluid dynamics on an aerofoil on a computer, without having to model the full quantum mechanical nature of each subatomic particle. That's not a full simulation of all events occurring in the system, yet the model nonetheless approximates to a high degree of accuracy the real-life system.

My iPad, sitting on my lap, can perform this model just fine: it approximates fluids as an aggregate of Newtonian atoms, rather than quantum fuzzy things. The model is a Newtonian iterative model which, ipso facto, generates vortices, local stagnation, pressure differentials, etc. It's an approximate model of a real-world system which, therefore, refutes computational irreducibility.

EDIT: I've had a read of Wiki's article on it, and I might have got the wrong end of the stick entirely. Watch this space...

 

[pgp_protector]

Side note, just got a new toy

Going off line now (not really, but I do got to check it out & go have some fun)

 

[Nabobalis]

Hah, just ask your lecturers how they reconcile the contradictions between GR and QM! The size of a black hole's singularity is different in both models. Physicists generally err on the side of QM, since it's prettier.

And, my reply was a bit glib; AV1611VET is infamous for his 'Science can take a hike', which you will probably see if you stick around

I have a thread like that over in Exploring Christianity. It's fun stuff, I'll check it out.​

Well I plan to ask since we do relativistic quantum mechanics too

I wish that my last year was how my first 3 years should of been. We seem to learn all the actual/real physics in my final year

Side note, just got a new toy

Going off line now

(not really, but I do got to check it out & go have some fun)

What is that?​

 

[pgp_protector]

What is that?

A prototyping board for developing software / hardware based on the PIC Microprocessors (single chip computers)

 

[gattaca]

I object to it because we can, quite readily, approximate a system without fully simulating all events occurring therein. For example, we can model fluid dynamics on an aerofoil on a computer, without having to model the full quantum mechanical nature of each subatomic particle. That's not a full simulation of all events occurring in the system, yet the model nonetheless approximates to a high degree of accuracy the real-life system.

My iPad, sitting on my lap, can perform this model just fine: it approximates fluids as an aggregate of Newtonian atoms, rather than quantum fuzzy things. The model is a Newtonian iterative model which, ipso facto, generates vortices, local stagnation, pressure differentials, etc. It's an approximate model of a real-world system which, therefore, refutes computational irreducibility.

EDIT: I've had a read of Wiki's article on it, and I might have got the wrong end of the stick entirely. Watch this space...

Computational irreducibility
is this, the reason, why weather forecast, are so accurate?

How accurate are the weather forecasts?

 

[Steffenfield]

Is it possible to compress a liquid somehow to the point where it becomes a solid matter?

If so, are there any examples or any reasons on how that could be a benefit to science?

 

[Umaro]

Nothing travels faster than light, but what about gravity? If the sun was to be removed instantly, would the planets instantly break off or would there be a delay until the gravity reached there?

 

[pgp_protector]

Nothing travels faster than light, but what about gravity? If the sun was to be removed instantly, would the planets instantly break off or would there be a delay until the gravity reached there?

From what I understand, the warping of space would propagate at the speed of light, so we'd see the sun vanish at the same time we feel it.

 

[Assyrian]

Would we feel it? Ignoring the cold of course. But wouldn't we simply keep travelling in a straight line instead of being pulled into an elliptical orbit, which we don't feel either.

 

[Wiccan_Child]

Is it possible to compress a liquid somehow to the point where it becomes a solid matter?

Yes. A substance can change state depending on its pressure and temperature: water freezes to ice when you lower the temperature, but it can also freeze to ice if you raise the pressure. A PT (pressure-temperature) graph for water is:

Temperature is on the bottom in Kelvin, pressure is on the side in Pascal. When water is at, say, 100K and 10[sup]3[/sup]Pa, it is in the 'S' portion of the graph, and is therefore a solid. 'L' is liquid, 'V' is vapour.

So, yes, liquids can be compressed into a solid.

If so, are there any examples or any reasons on how that could be a benefit to science?

Scientists generally use temperature to vary a substance's state, but pressure is also used. Determining whether another planet has liquid water requires us to know both its temperature and its pressure: a planet could be at a nice 20°C, but its crushing air pressure keeps the water as ice.

 

[Wiccan_Child]

Computational irreducibility
is this, the reason, why weather forecast, are so accurate?

How accurate are the weather forecasts?

In a sense. Weather forcasts are notoriously inaccurate because the system is chaotic: very small variations in initial conditions can mean the difference between calm weather and gale-force storms next week. So even if our data of current weather is very very accurate, any small error will quickly escalate and invalidate our model. The limitations of computation are why we can't model weather further than about a week away.

 

[Wiccan_Child]

Nothing travels faster than light, but what about gravity? If the sun was to be removed instantly, would the planets instantly break off or would there be a delay until the gravity reached there?

It's generally accepted that gravity waves travel at lightspeed. There's a large facility that has been built to detect gravity waves, with its first discovery just last month.

 

[Wiccan_Child]

Would we feel it? Ignoring the cold of course. But wouldn't we simply keep travelling in a straight line instead of being pulled into an elliptical orbit, which we don't feel either.

We'd be plunged into night, and the stars would start to move differently, but we wouldn't be pulled into space or anything like that. We move relatively quickly through space, but our acceleration around the Sun is quite small. But you're right, we'd probably move in a straight line (relative to our elliptical orbit). We might be captured by Jupiter, but I doubt it.

Incidentally, ingesting Tellurium gives you garlic breath

 

[Chesterton]

So, yes, liquids can be compressed into a solid.

Gases too, then? Because I read once that they think the pressure inside Jupiter is so great that as you move toward the core the gases become solid, or some kind of hybrid state of matter (or something like that).

 

[Wiccan_Child]

Gases too, then? Because I read once that they think the pressure inside Jupiter is so great that as you move toward the core the gases become solid, or some kind of hybrid state of matter (or something like that).

Pretty much. Look at that graph I posted above, and look up as you increase the pressure: you go from vapour to liquid to solid (by and large; at low temperatures, gases sublimate into solids, bypassing the liquid phase). I read that the carbon in Jupiter sunk to the core, and became a giant diamond under the pressure - a diamond bigger than the Earth. Try and find a woman who'd say no to that

 

[Soul Searcher]

Does that mean that the temp required to freeze water would be different at sea level compared to Mt. Everest due to air pressure differences?