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Ärstotzka
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Re: Ask a Physicist Anything!

Postby Ärstotzka » Fri Aug 28, 2015 1:57 am

What did China's stock market crash into?
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Re: Ask a Physicist Anything!

Postby kudayta » Fri Aug 28, 2015 3:25 am

Ärstotzka wrote:What did China's stock market crash into?


The Abyss.

In all seriousness, I may be better equipped to answer this question than UA. What's happening in China right now is a depression in their equity market(s). What happened is that for years, people had been investing in various Chinese companies, often with borrowed money (buying on spec). When it came time to pay, it was realized that virtually no one had enough cash on hand to cover the margin call (this is when a broker demands you pay up for the stock you bought), the stock prices plummeted. It was just a string of debt all the way down. The initial phase of this phenomena is called a "bubble", the prices rise sharply based on the collective confidence in a stock or stock market. The bubbles tend to pop though, and this is a crash.

There is a lower limit to all of this though, which many people in economics tend to overlook. Economics is just applied psychology (psych is just applied biology, which is applied chemistry, which is applied physics). At the end of the day, what matters is if China can grow (or obtain) enough food, put roofs over the heads of its citizens, and protect them from foreign or domestic organized violence. The property markets in China are doing fine, it's just their equity (stock) markets that are crashing. They'll be fine, though it'll be a rough few years for them.
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Re: Ask a Physicist Anything!

Postby trickser » Fri Aug 28, 2015 2:11 pm

I have a question I would like to get rid of, but can't on my own and a physicist would be the right adress, so I give it a shot.

Can a rigid body rotate around 2 axis simultaniously?

Imagine a symmetric gyroscope, rotating around one axis of symmetry, then imagine the rotation axis rotates around an orthogonal axis going through the bodies center.

As I see no contradiction in the geometric description I just gave, I assume a state of the body can exist which can be described as rotating around 2 axis simultaniously, just I dont know how the dynamics would work out. Will the rotations stay seperate, merge, chaoticly oscillate?

There are phenomenons of gyroscopes called nutation and precession, for not symmetric gyros and for gyros within forcefields. Thoses might be related but thoses are not what I am asking about per se.
Last edited by trickser on Fri Aug 28, 2015 2:25 pm, edited 2 times in total.
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Re: Ask a Physicist Anything!

Postby xander » Fri Aug 28, 2015 2:13 pm

kudayta wrote:--==<snip>==-

While that is certainly part of the issue, there is also a healthy dose of the-Chinese-government-was-propping-things-up-for-far-too-long. Investors got used to bailouts and came to expect them. When they stopped last week, investors panicked. On the bright side, I doubt that the crash has much (if any) effect on the average Chinese person. The Chinese stock market seems to have even less to do with the Chinese economy than the US markets have to do with the US economy.

xander
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Re: Ask a Physicist Anything!

Postby UNITEDAIR » Fri Aug 28, 2015 4:12 pm

Ars: Kud is right. I'm not a political theorist or economist.
I would like this thread to not decent into political anything really. That crap is for another time/post.
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Re: Ask a Physicist Anything!

Postby UNITEDAIR » Fri Aug 28, 2015 4:55 pm

Trickser :
Rotation along 2 axis simultaneously for a 3-d object presents no problem if it rotates along axis with the smallest and largest moment of inertia.
Rotation along the axis of intermediate moment of inertia will be unstable and cause the axis it to oscillate or 'flip', but that only happens for non 3-symmetric objects (non spherical things, see tennis racket theorem and some cool videos on the international space station).

Other than that, yes things can rotate along 1, 2, or even 3 axis of rotation. Rotation on all 3 axis simultaneously results in a so called Gimbal lock.
That occurs when 2 of the axis line up and 'lock' it resulting in one less degree of freedom, it can be freed up with another fourth rotation axis.

Nutation and precession, as I understand it, is slight imbalances in torque...slight imbalances on the top etc, asymmetric around it's axis of rotation...sometimes inherit in the 'top' system itself, it's not a perfect abstract solid etc. You can't really escape it.
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Re: Ask a Physicist Anything!

Postby MAXtheMASTER » Fri Aug 28, 2015 9:36 pm

Can life emerge based on non-baryonic matter?
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Re: Ask a Physicist Anything!

Postby kudayta » Sat Aug 29, 2015 12:36 am

MAXtheMASTER wrote:Can life emerge based on non-baryonic matter?


Now this is a good question. The answer is of course, we don't know. But if there is a 'dark chemistry', then this could produce self replicating molecules, which could in turn be subject to a proto-selection process. Which could lead to 'dark life'.
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Re: Ask a Physicist Anything!

Postby UNITEDAIR » Sat Aug 29, 2015 12:49 am

Max:
Hmm hard to say, I don't think so. Here's why:
To our readers: Baryonic matter is matter composed from 3 quarks. Proton and Neutrons are baryonic matter.

I should point out that life doesn't just include baryonic matter alone. The electron (a lepton, not a baryon) is responsible for all of chemistry.
A lepton is a fundamental particle that doesn't interact with the strong force (which Hadrons do!). There are two types of leptons: charged and uncharged. There are three charged: the electron, the muon, and the tau. Unlike the electron, the muon and tau are unstable and decay (in mere nano seconds and less) , so that will not make good life ingredients. The uncharged leptons are 3 flavors of neutrino, which are so light, are not charged, and generally don't interact with anything at all, even themselves, that also makes terrible life ingredients. But the electron is eternal (at least for 13 billion years) and charged! That's great! That comes in later handy.

On to Hadrons. A Hadron is a particle composed of quarks. Quarks are fundamental particles that can combine in ways to make larger crap. 2 quarks make a meson. Mesons are unstable and decay into electrons, neutrinos, and/or photons. 3 quarks are called baryons. All baryons are unstable except the proton. The neutron is unstable by itself but in the nucleus of an atom, it's stable. There are other quark (4,5,6+) combs. are also all unstable. And you cannot isolate a single quark. So yea, looks like only protons and neutrons mixed for us today. Protons are electrically charged. I mentioned earlier that so are electrons. Opposite too! Wonderful! Now the electrons can interact positively (attract) with the protons (nucleus of atom) and form complex structures shapes with other atoms too.

Everything above are called Fermions, which basically means they obey the Pauli - exclusion principle, which means they can't occupy the same space at the same time (same quantum state to be precise).

Everything else are called Bosons. While Fermions are the 'matter', bosons are the 'force' . The best known Boson is the Photon, also called Light. Photons transmit the electromagnetic force. Photons don't interact with themselves per say (they can occupy the same space and pass through each other, like a wave), they also don't 'persist' with other matter to create complex structures, they get absorbed or scattered etc... so hard to think of life from that. The other bosons are the same, such as the Higgs Boson.

Also depends on what you mean by life... if you mean, self replicating thingy... then sure lots of crap is that. I assume you mean a bit more complicated.
I don't really know, it's hard to imagine.
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Re: Ask a Physicist Anything!

Postby DTNC Vicious » Sat Aug 29, 2015 8:37 am

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Re: Ask a Physicist Anything!

Postby Laika » Sat Aug 29, 2015 10:17 am

How can we possibly get faster than light travel ? Why it may (or may not) be possible ?
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Re: Ask a Physicist Anything!

Postby Endless » Sat Aug 29, 2015 12:19 pm

Laika_rus wrote:How can we possibly get faster than light travel ? Why it may (or may not) be possible ?


We can't (right now). The human body can't take the pressure of traveling at that speed. Hell, we pass out at Mach 2.
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Re: Ask a Physicist Anything!

Postby kudayta » Sat Aug 29, 2015 1:32 pm

Endless wrote:
Laika_rus wrote:How can we possibly get faster than light travel ? Why it may (or may not) be possible ?


We can't (right now). The human body can't take the pressure of traveling at that speed. Hell, we pass out at Mach 2.


Not exactly, it's not the speed, but the acceleration that causes blackouts. If a vehicle were to slowly accelerate to the speed of sound and beyond, you'd not notice any ill effects.

Accelerating to the speed of light is impossible for even stranger reasons. From the point of view of people watching, the ship will gain in mass, and it will get harder and harder to accelerate as you approach the speed of light. Getting to the speed of light would require, again from the point of view of people watching, infinite mass. From the point of view of the passengers on the ship, the universe would appear to be squashed in the direction of travel and it would look like you could get to your destination before you even hit the speed of light. I'll let UA give a more detailed explanation of Lorentz contraction, I'm not nearly qualified to do that.
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Re: Ask a Physicist Anything!

Postby UNITEDAIR » Sat Aug 29, 2015 5:54 pm

Laika:
We can't. It is a true impossibility.
I have no idea what Endless means. And Kudayta is correct.
Einstein's Relativity explains all of this. It has been know for a long time that velocity is a relative concept. You'r standing still relative to the earth. Earth is moving relative to the sun, which is moving relative to the center of the Milkway. And all galaxies are moving relative to each other. There is no absolute frame, you can place your coordinate system where ever you want. Einstein postulated that the laws of physics are the same for all observers. This also includes the speed of light. Thus, for all observers, the speed of light is the same. This leads to some interesting stuff as kud describes. Acceleration frames of reference are even weirder, but you still can't catch up to light, it will always zoom away at light speed. Time and space always conspire to do this for anything with mass. If you have zero mass, then you are doomed to always travel at light speed the end. I can expand upon it further in technical detail if you want, but honestly it doesn't make much intuitive sense for me either.

Endless: Humans a perfectly capable of handling any velocity since your always standing still in your frame of reference. Acceleration isn't much of a problem. In fact, at a constant acceleration of 1G, you can cross the entire visible universe in 40ish years or so. Of course, it would take an equally large amount of time to deccelerate back to where you once was, not to mention people back on earth, it would be like 10^10 years or sometimes absurd.

Now if you want to bypass normal space travel, I assume you want wormholes or warp drives or someother way of bending space itself, which is totally theoretical and were not even sure it's even possible.
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Re: Ask a Physicist Anything!

Postby atomic oracle » Fri Sep 04, 2015 8:24 pm

If there are more servers than players will that upset the flow of space/time?

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