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Comment by Symmetry | Hacker News Reader

A rather depressing interview. I enjoyed a lot of the explanations of Physics in *The Emperor's New Mind", but even there I could see big holes in his arguments about consciousness. For example, he talks about how its impossible to make an algorithm tile a grid in a certain way, but I had a screensaver which in fact did what he was saying was impossible. Here I just feel sort of sad and lost.

I think my least favorite line was probably this: "The trouble is, what can you do with it? Nothing. You want a physical theory that describes the world that we see around us." If you're going to use that to reject theories about the reality of the wave function, astronomers in the Renaissance would have been equally justified in rejecting the heliocentric system on account of it being at odds with what they saw around them, or Greek astronomers rejecting the notion that the world was round.

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> astronomers in the Renaissance would have been equally justified in rejecting the heliocentric system on account of it being at odds with what they saw around them

False. Sights observed through a telescope were also part of "what they saw around them." A true theory accounts for all the evidence (and if it's not ultimately reducible to or based on something you can get from the five senses, it's not evidence).

Telescopes don't show you that (contrary to what your inner ear is telling you) its the Earth that moves rather than the sun. At best they tell you that Jupiter has things orbiting it.

Also, astronomers in the Renaissance didn't have telescopes, so the moons of Jupiter weren't part of what they saw around them anyway.

I hate to point this out to someone with the username "planetguy", but Galileo certainly had telescopes, definitely lived in the Renaissance, and discovered four moons of Jupiter.

And as someone with the username "planetguy" I hate to be corrected, but you're right. My defense is that I am planetguy, not historyguy. :)

Historical brainfart.

Telescopes show that Venus displays phases like the moon while Mars and Jupiter don't, which is important evidence for heliocentrism and the order of the planets relative to Earth.

Telescopes also show that Jupiter's satellites experience eclipses, which isn't direct heliocentric evidence, but does tell you that Jupiter and its moons shine by reflected sunlight rather than intrinsic luminosity.

Telescopes also show sunspots, leading towards the discovery that the Sun is an active body, and to some notion of its size and mass. Telescopes can also show Venus transiting the Sun giving you a great idea of their sizes, which happened in 1639. http://en.wikipedia.org/wiki/Transit_of_Venus#First_scientif...

The switch to heliocentrism didn't happen overnight or as the result of a single observation or event, but telescopes brought in many different streams of evidence for it.

Telescopes also show that Mars does loops as it pans across our sky

That can be seen with the naked eye.

What did tell us that the Earth moves rather than the sun?

Nothing. Movement is relative, based on your chosen point of origin.

But, I guess your question was, how did we learn about the structure of the solar system, planets and orbits and all...

By observing the planets, you can map out their path, and you can see that they are not orbiting earth. The only sensible explanation is that all the planets, including Earth, must be orbiting the Sun.

Kepler then further observed that the orbits are elliptical, and then postulated Kepler's laws (that planets orbit the sun in an ellipse, with the sun in one of the focuses).

> he talks about how its impossible to make an algorithm tile a grid in a certain way.

My guess, is that here he is talking about undecidability which appears quite often in mathematical problems, maybe something like this http://en.wikipedia.org/wiki/Wang_tile or http://www.nd.edu/~svandend/Tilings.pdf (pdf).

Uh. That's what evidence is for. If you have new evidence arguing for a different theory, then you present that evidence and have it tested. It gets added to the pool of "what we see around us".

That's why Penrose is unable to argue against QM the way he argues against string theory: there's experimental evidence and he can't gainsay that.

By the way, if you're looking for a good book to read on philosophy and the history of science, give David Harriman's book a shot. It's called "The Logical Leap: Induction in Physics."

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