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Typically, I despise the use of "emergence" as an explanation.  It's usually just a hand-wavey excuse for not knowing whats going on.

In this case…I've got to think about it some more.

The experiment involves the creation of a toy universe consisting of a pair of entangled photons and an observer that can measure their state in one of two ways. In the first, the observer measures the evolution of the system by becoming entangled with it. In the second, a god-like observer measures the evolution against an external clock which is entirely independent of the toy universe.

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Quantum Experiment Shows How Time ‘Emerges’ from Entanglement
When the new ideas of quantum mechanics spread through science like wildfire in the first half of the 20th century, one …

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Superman with a possibly skewed moral sense.

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It's also less dense than water so it would float if you could find a big enough bathtub.

Hyperion is the largest non-spherical moon in the Solar System.

It’s also less dense than water so it would float if you could find a big enough bathtub.

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Goblin shark.

Goblin shark.

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Klingon cover of an Earth classic.

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 Constructed from high-resolution MRO data.

Simulation of the rim of Mojave crater on Mars.  Constructed from high-resolution MRO data.

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Reshared post from +Brian Koberlein

Problematic

Newton’s law of gravity takes a bit of calculus to really wrap your head around it, but the basic relation is very simple.  Every pair of masses in the universe experiences a mutual gravitational attraction, each feeling the pull of the other’s gravitational field.  The force of attraction is mutual, which leads to some interesting consequences.  For example, when you step on the scale in the morning, you are weighing yourself in the Earth’s gravitational field.  You are also weighing the Earth in your gravitational field.  Your weight is also the Earth’s weight in your gravity.

The strength of that attraction depends on the size of the two masses and the distance between them, following a relation known as the inverse square law.  Suppose two masses feel a force of 100 Newtons between them.  If you double their distance of separation, then they would feel a force of only 25 Newtons, a fourth of their initial force.  It’s a remarkably simple relationship.

But there’s a gravitational force between every pair of masses in the universe, which is where things can get complicated.  In order to calculate the motion of an object in general, you would need to determine the gravitational attraction from all the other masses in the area, and you need to determine how those masses are gravitationally affected by the object.  There are lots of ways to simplify things a bit.  After all, the largest and closest masses will have the greatest effect on an object, so usually you can ignore the gravity of distant objects.  When calculating the motion of the Moon, for example, you don’t have to worry about the gravity of the Andromeda galaxy.

But even with simplifications there is still a problem.  While we have a simple general solution for the motion of two masses acting under their own gravity, we don’t have a general solution for three masses.  We just can’t determine the exact motion for three masses moving in general ways.  This is known as the 3-body problem, and it is problematic.

This doesn’t mean we can’t predict the motion of three or more massed acting under gravity.  We can actually predict motions quite well, just not exactly.  For 3-body systems like the Sun, Earth and Moon we can describe the motion very precisely.  We’ve also found some interesting exact solutions to the 3-body problem for specific cases, such as three equal masses moving along a common orbit as seen in the figure below (http://goo.gl/AN2x6h).  

We can find specific solutions for three or more masses, but we can’t find a complete general solution.  Instead we find approximate solutions, or determine solutions computationally.  Normally this isn’t too much of a problem, but there are cases where the future motion of an object is extremely sensitive to its current position.  This can be particularly true for the case of a small mass in a complex gravitational field.  

Of course Newton’s gravity is an approximation of Einstein’s general relativity, but in general relativity it gets worse.  We can calculate the motion of an object in the gravitational field of another (such as the motion of Mercury in the Sun’s gravitational field), but the general 2-body solution can’t be done in general.  If we want to calculate the motion of two orbiting neutron stars, for example, we must do it computationally.  That means there are no general exact solutions in GR.  

Sometimes in astrophysics a simple idea can be quite problematic.

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Even though science is the best method we have of understanding the world around us, it isn't good enough…yet.

Another link on the subject that I share quite often is:  http://contriving.net/link/scienceflaws

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How science goes wrong
A SIMPLE idea underpins science: “trust, but verify”. Results should always be subject to challenge from experiment. That simple but powerful idea has generated…

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