“The Unravelling of Space-Time”

[pood]

Looks to be a interesting series here, divided into nine parts, at Quanta, called “The Unravelling of Space-Time.” The interactive intro page to which the link takes you is inventive, especially at the end where you can manipulate an entire concluding paragraph to fall down a black hole, but still rather annoying for all that. Just because you can do something, doesn’t mean you should. Wisdom from Jurassic Park

However, the page is participatory, a nice intro the first essay.

The first essay, the only one I’ve read so far, is on John Wheeler and his participatory universe. Wheeler seemed to be taking us very close to abandoning metaphysical naturalism in favor of metaphysical idealism, and the latter has always intrigued me as a live possibility. An extract from the essay:

In 1977, Wheeler gave a talk emphasizing that “no elementary phenomenon is a phenomenon until it is an observed phenomenon.” Afterward, the physicist Paul Dirac asked, “The formation of the solar system is a phenomenon. Is it only a phenomenon when it is observed?” Wheeler responded: “Yes.”

How much this is like old Schopenhauer, who lived before relativity, quantum physics, modern science, et al, and yet was motivated to write:

The existence of this whole world remains ever dependent upon the first eye that opened, even if it were that of an insect

Toward the end, it recounts how Wheeler agonized over how it is, in a participatory universe, that there is any consensus reality at all. And I couldn’t help wonder whether he was even moving beyond potential metaphysical idealism to potential metaphysical solipsism.

But even before Wheeler, special relativity was telling us we all have our own private space-time. That there is any superficial consensus about it is because in the main we share the same reference frame.

Anyhow, even though Wheeler was a scientist I put this in the philosophy forum, which is perfectly OK because IMO science and philosophy and inextricably intertwined. I’ll read all the essays as time permits and hopefully others will, too, and offer comments. To me, this is so much more interesting than mere politics, though unfortunately politics is probably more important for everyday life, especially now.

 

[Spacetime Inhabitant]

Who is the observer?
How does one observe quarks?

 

[bilby]

Who is the observer?
How does one observe quarks?

Just go to Barambah. It's near Gympie, just north of Brisbane.

 

[aupmanyav]

Who is the observer?
How does one observe quarks?

Quarks. There is none other.

 

[steve_bank]

Schrodinger came up with his cat problem to illustrate the ridiculous ways QM can be interpreted..

Or the old 'if a tree falls in the woods and there is no one there to heat it does it make a sound?'.

I heard that as a kid.

Experimentally in a a particle experiment the instrumentation is the observer. We interpreter the interaction of the test apparatus and the particle.

The Brookhaven site has descriptions of the RHIC collider and how particles are detected in a collision experiment.

 

[pood]

Schrodinger came up with his cat problem to illustrate the ridiculous ways QM can be interpreted..

Yes, it was intended as a reductio, but did it really do what he intended?

 

[Elixir]

Yes, it was intended as a reductio, but did it really do what he intended?

As long as you don't open the box ...

 

[pood]

Schroedinger apparently intended the cat as a reductio of Copenhagen QM, which is that quantum particles are in superposition until measured. The cat set-up scales up QM to the macro level, suggesting the cat was both alive and dead until measured. He felt that was absurd, but in 1952 he broached the idea that the cat was both alive and dead in different universes. Hugh Everett presented his worked-out thesis of this notion five years later.

 

[Jarhyn]

Schrodinger came up with his cat problem to illustrate the ridiculous ways QM can be interpreted..

Or the old 'if a tree falls in the woods and there is no one there to heat it does it make a sound?'.

I heard that as a kid.

Experimentally in a a particle experiment the instrumentation is the observer. We interpreter the interaction of the test apparatus and the particle.

The Brookhaven site has descriptions of the RHIC collider and how particles are detected in a collision experiment.

Test apparatus and particles: pulling information about "a particle" inevitably requires a change in the particle to generate that information except in very rare cases such as time crystals, and that's less "not changing" and more "changing back again completely after the interaction"

 

[steve_bank]

That is the problem with QM measurements.

Put a thermometer into a glass of water. You do not resume the water you measure the temperature of thermometer, water, and glass. There are very small low mass thermal sensors to minimize the disturbance created by the sensor. Analogy to quantum measurements.

Energy from the water is lost to heat up the tmermometr.

Put a thermometer into a large lake and the mass f the thermometer is insignificant. Macro Newtonian measurements.

Whether something exists until measured or observed to me is semantics.

Flip a coin in the air in a dark room. Periodically flash a light while it is in the air and there is a probability of it being in a certain orientation.

When it settles on the floor the wave function has collapsed from a 50/50 probability of heads or tails to an actual observable heads or tails. At no time does the coin not exist in a measurable state.

 

[pood]

That is the problem with QM measurements.

Put a thermometer into a glass of water. You do not resume the water you measure the temperature of thermometer, water, and glass. There are very small low mass thermal sensors to minimize the disturbance created by the sensor. Analogy to quantum measurements.

Energy from the water is lost to heat up the tmermometr.

Put a thermometer into a large lake and the mass f the thermometer is insignificant. Macro Newtonian measurements.

Whether something exists until measured or observed to me is semantics.

Flip a coin in the air in a dark room. Periodically flash a light while it is in the air and there is a probability of it being in a certain orientation.

When it settles on the floor the wave function has collapsed from a 50/50 probability of heads or tails to an actual observable heads or tails. At no time does the coin not exist in a measurable state.

The coin toss is not the same in quantum as in classical. In classical, you could predict the outcome of the toss if you had knowledge of all the variables, a practical impossibility but possible in principle. In QM this not possible even in principle.

 

[steve_bank]

.A coin toss is the same principle. A wave function can be derived to model the toss.

The way I remember it put is as you go from quantum to Newtonian scale the density of states is such that it appears continuous. Like a piece of copper. What we seen as a Newtonian scale block of metal is the superposition of all the instantaneous states of each atom in the block.

The problem with QM is the relative energies. In electronics it usually easy to s reduce the interaction of apparatus and what is being measured such that the effect is inconsequential.and quantfy the effect of a measurement apparatus.

Put6v a battery at exactly 10 volts acrostwo resistors in series each at exactly 1 ohm and the voltage across each resistor will be exact 5 volts. Put a meter across a resistor to measure the voltage an it will not read exactly 5 volts. The meter reads the voltage due to the subsystem inclusive of the circuit and measure mt apparatus. The input resistance of the meter becomes part of the circuit.

Does what we perceive as a particle in an experiment a a manifestation of the measurement or does the particle exist as we model it?