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3 minutes ago, kerbiloid said:

Though the closed system is like a material point. Never happens irl.

That law works at just about any scale.

A closed life-support system is impossible without at least energy input for example, and for any complex system entropy will increase within that system(parts wearing out and breaking down for example).

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10 minutes ago, Terwin said:

A closed life-support system is impossible without at least energy input for example, and for any complex system entropy will increase within that system(parts wearing out and breaking down for example).

That point is clear. (Even if forget that any system looking closed irl always is one of parts of a greater closed system and interacts with them).

Just one thought haunts me.
If the entropy always grows, then Big Bang should be the state of the Universe with the least entropy ever.
Why then our world looks so chaotic. Why it doesn't look like a perfect crystal. What went wrong with the ideal symmetry.

Edited by kerbiloid
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1 hour ago, kerbiloid said:

That point is clear. (Even if forget that any system looking closed irl always is one of parts of a greater closed system and interacts with them).

Just one thought haunts me.
If the entropy always grows, then Big Bang should be the state of the Universe with the least entropy ever.
Why then our world looks so chaotic. Why it doesn't look like a perfect crystal. What went wrong with the ideal symmetry.

If all energy(and matter if it can exist at that energy level) was at one point and in one coherent state then that sounds incredibly ordered(or low entropy) to me.

One form of entropy is reduction of order(for example a set of marbles lined up and sorted by size and color has less entropy than the same set of marbles dumped on the floor), so reducing the original ideal symmetry is just one more form of increasing entropy(I am not a high-energy physicist so I will not pretend to be able to say how entropy increased during those first few fractions of a second, I can only say that it did because otherwise the entire universe would still be contained in something similar to a high-energy point source)

 

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Why do passenger cars usually have a "pushed-in" area on the doors, between the wheels, marked with a red arrow on the picture below? Or, as one might say, "pushed-out" wheel covers relative to the rest of the car's body? Is that good for aerodynamics, or some other weird technical reason, or perhaps just an artistic design trend?

0kf6Gh7.png

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3 hours ago, TheDestroyer111 said:

just an artistic design trend?

This. 

A weak argument could be made that there is less material, ergo less weight, more fuel efficient and cheaper to build, but the main reason is styling.   There are still plenty of cars made that have 'flat sides'.

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15 hours ago, Gargamel said:

This. 

A weak argument could be made that there is less material, ergo less weight, more fuel efficient and cheaper to build, but the main reason is styling.   There are still plenty of cars made that have 'flat sides'.

Yes I say flat is far more common as it also give an wider cabin, more sport like cars like the one shown uses push in but sport cars tend to be wide in the first place 
I say its artistic  as it looks good 

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10 minutes ago, NSEP said:

Can you collect and store gamma ray energy with a regular magnet just by putting it in deep space?

Gamma rays are high energy photons, I don't think they will be influenced by a magnetic field.  Are you maybe thinking of cosmic rays?  The solar wind is made up of charged particles, protons, electrons and alpha particles and makes up most of the radiation in the Van Allen belts.    

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1 hour ago, KG3 said:

Gamma rays are high energy photons, I don't think they will be influenced by a magnetic field.  Are you maybe thinking of cosmic rays?  The solar wind is made up of charged particles, protons, electrons and alpha particles and makes up most of the radiation in the Van Allen belts.    

Yes, i meant charged particles. I always mix them up.

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On 10/16/2018 at 1:25 PM, TheDestroyer111 said:

Why do passenger cars usually have a "pushed-in" area on the doors, between the wheels, marked with a red arrow on the picture below? Or, as one might say, "pushed-out" wheel covers relative to the rest of the car's body? Is that good for aerodynamics, or some other weird technical reason, or perhaps just an artistic design trend?

0kf6Gh7.png

The original reason for contour lines on cars is to increase the rigidity of the panels. If the panel is stamped metal, stamping it makes it stronger by work-hardening it. At the same time, making curved or creased panels makes them stronger by increasing the (not sure of the correct terminology here) bending moment? Cross-section?  In the same way that angle iron or an I-beam is stronger than a flat strap of metal of the same thickness.  

(Modern) Vehicles that use plastic panels for lightness have most of their strength in the (unibody) frame and underpinnings, so any molding would be for looks.

Of course a dollar bill (or other  paper money) has no resistance to bending while flat, but fold it lengthwise like an accordion and it will support a load

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8 hours ago, NSEP said:

Can you collect and store gamma ray energy with a regular magnet just by putting it in deep space?

[...]

Yes, i meant charged particles. I always mix them up.

You need something separate for storage, but MHD generator can generate power from solar wind. Solar panel will give you way more power, though.

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Is it possible to launch rocket to orbit horizontally by having a rocket strapped to an aperture on rails several kilometers long where the aperture is accelerated along these rails by using solid boosters before essentially "throwing the entire rocket" at the end of the rails where the rocket boosts itself horizontally to leave the atmosphere and readjusting for orbit circularization once it's out of atmosphere. Think an aircraft catapult on steroid

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1 hour ago, ARS said:

Is it possible to launch rocket to orbit horizontally by having a rocket strapped to an aperture on rails several kilometers long where the aperture is accelerated along these rails by using solid boosters before essentially "throwing the entire rocket" at the end of the rails where the rocket boosts itself horizontally to leave the atmosphere and readjusting for orbit circularization once it's out of atmosphere. Think an aircraft catapult on steroid


It's possible.  It's about the stupidest and most useless way to launch a rocket, but it is possible.

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6 hours ago, ARS said:

Is it possible to launch rocket to orbit horizontally by having a rocket strapped to an aperture on rails several kilometers long where the aperture is accelerated along these rails by using solid boosters before essentially "throwing the entire rocket" at the end of the rails where the rocket boosts itself horizontally to leave the atmosphere and readjusting for orbit circularization once it's out of atmosphere. Think an aircraft catapult on steroid

Too much time in lower atmosphere, it takes a colossal amount of energy to go fast at low altitude. 

Drag is proportional to the square of velocity.

Atmospheric density has a complex relationship with altitude, but it is still an (inverse) exponential function.

These combine to make drag at high speed and low altitude extremely high.

The good news is, that this means you can reduce drag significantly by increasing altitude, which is why we dont launch rockets horizontally.

 

Hypothetical spaceplanes are a different matter for a variety of reasons., discussed at length in other threads.

 

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20 minutes ago, p1t1o said:

How small do you have to write, before it becomes digital media?

What is the maximum physical size of a "bit" before it becomes a "dot"?

Err ... is this a philosopher's thought about the real life representations of logical units :unsure: ?

I mean, handwriting is size independent analogue, storing characters on any computer takes place in digital format, regardless of size (well, less then 5*5 pixels makes no sense). A dot (pixel or fragment) can have many bits to describe it .... but you know all this so i just stay unsure what you mean ...

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On 10/18/2018 at 8:21 PM, StrandedonEarth said:

The original reason for contour lines on cars is to increase the rigidity of the panels. If the panel is stamped metal, stamping it makes it stronger by work-hardening it. At the same time, making curved or creased panels makes them stronger by increasing the (not sure of the correct terminology here) bending moment? Cross-section?  In the same way that angle iron or an I-beam is stronger than a flat strap of metal of the same thickness.  

(Modern) Vehicles that use plastic panels for lightness have most of their strength in the (unibody) frame and underpinnings, so any molding would be for looks.

Of course a dollar bill (or other  paper money) has no resistance to bending while flat, but fold it lengthwise like an accordion and it will support a load

Your explanation sounds more like this 
GP-AK150MAG-L.jpg

Here you have ribs to increase the stiffness of an flat plate, any dent could cause jams, however its just the plate. 
On car doors you use internal structures for stiffness, especially regarding side collisions, modern car doors are far thicker than old cars, this also include deformation zones to absorb impacts. 
 

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I guess I will post this here.  In the movie First Man, the scene where Neil Armstrong was flying the X-15 they showed the altimeter on the aircrafts instrument panel.  It displayed an altitude on over 100,000 feet it I recall correctly.  If an altimeter works by measuring barometric pressure at what altitude does it stop working?  Same with pitot tubes.  Is there an altitude that pitot tubes stop reading air speed because there just isn't enough air?

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There is no hard limit for an altimeter. It just gets more and more inexact because the change in pressure with an altitude step gets ever smaller. Still, for use in aircraft, it is far more exact then GPS. A radar could be equally or better, but needs a lot of energy. Also, the barometric pressure height is the same for all participants if they all set their instruments to the same base value. Which avoids controversy about the occupation of the same spot at the same time ;-) (*)

For a pitot tube the same holds in principle, though here the difference between a static and a dynamic pressure is used. Correction for compressibility of air (speed), pressure (height) and temperature are applied.

In every day aviation life a limit plays no role.

 

(*) Edit: I just read (on stackexchange) that the ISA standard atmosphere definition and the derived mode of computation and calibration will probably render the reading of a normal altimeter useless at an altitude of 80-100.000 feet. So, that might be your number.

Edited by Green Baron
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On 10/19/2018 at 10:57 PM, p1t1o said:

How small do you have to write, before it becomes digital media?

Digital media is about telling how to recreate the thing, not the thing itself. Digital videos contains encoded images. Digital images contains encoded pixel color and brightness information. Digital sound contains encoded amplitude level information. Digital text contains encoded character information.

Contrast with analog methods of reproduction, like magnetic tapes or vinyl disks or analog optical discs or analog broadcasting. They contain direct changes that translated directly to what the things were. If parts of it were missing, there's no way at all to recover what the missing parts are. Digital encoding allows full or partial recovery, depending on the encoding used.

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If we replace the fragment grooves on frag grenade casing with diamonds to make it sprays diamond fragments everywhere when it explodes, does it make the grenade more effective in dealing with armored infantry?

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43 minutes ago, ARS said:

If we replace the fragment grooves on frag grenade casing with diamonds to make it sprays diamond fragments everywhere when it explodes, does it make the grenade more effective in dealing with armored infantry?


Probably not.  For all it's hardness, diamonds are extremely brittle - the explosion alone would probably turn them into dust from the shock.

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5 hours ago, ARS said:

If we replace the fragment grooves on frag grenade casing with diamonds to make it sprays diamond fragments everywhere when it explodes, does it make the grenade more effective in dealing with armored infantry?

Life is not a videogame. As far as I know, grenades have no problem dealing with "armoured" infantry. Consider what todays armour looks like, what threats it is designed for and what its limitations are.

 

 

On 10/19/2018 at 5:25 PM, Green Baron said:

Err ... is this a philosopher's thought about the real life representations of logical units :unsure: ?

I mean, handwriting is size independent analogue, storing characters on any computer takes place in digital format, regardless of size (well, less then 5*5 pixels makes no sense). A dot (pixel or fragment) can have many bits to describe it .... but you know all this so i just stay unsure what you mean ...

Was a practical, physical question. With possibly a bit of a crossover into semantics. The answer is probably meaningless, but I thought it was an interesting question.

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