The Most Important Questions In Science

> One where the ratio of a circle's circumference and diameter is not equal to pi

You don't need a different universe for that. You just have to be in Indiana.

http://en.wikipedia.org/wiki/Indiana_Pi_Bill

1) We perceive time as such because the future determines the past but not vice-versa (H(t|t-1)>0 and H(t-1|t)=0 in terms of entropy) -- thus our brain can at a given moment contain relatively complete information about past moments, but necessarily limited information about future moments. I think relativity gives a pretty good picture of the nature of time; it is a partial order. Quantum mechanics treats time very differently though, so there is almost certainly more to say. I think this is a good question to be asking.

2) There's something inside a block hole?

It's funny that you should use those two examples in your last question. The first one is true or false depending on the logic you use, and the second is physically false.

The first statement -- that (p or not p) is always true -- is true in Boolean logic but not always true in Constructive logic; in fact this is what separates these two forms of logic. My very rough understanding is that boolean logic best describes situations in which propositions like p are taken to mean "p is true", whereas in constructive logic p is taken to mean "p is provable".

The second statement -- that the ratio of a circle's circumference and diameter is equal to pi -- is false under general relativity. In fact, if you were to measure the circumference and diameter of a big circle around the sun, their ratio would be a little off due to the sun's gravity (I forget in which direction).

You ask whether the laws of logic are true in every possible universe. It depends entirely on what you mean by every possible universe. To really consider one possible universe, though (say the one where everything is made of cheese), we have to be able to reason about it. So if the laws of logic are not true in it (maybe the cheese is also not cheese), we can't really consider it to begin with. So yes, the laws of logic are true in every possible universe, though for a rather boring reason.

Why you perceive time the way you do is easy enough. At any "point" in time your brain (or any physical system for that matter) is influenced by the points before it. Play around with cellular automata and it kind of gives you a sense of how time can be viewed as a dimension similar to space.

>Are the laws of logic always true in every possible universe? Could there exist a universe where p|^p is not always true? One where the ratio of a circle's circumference and diameter is not equal to pi? I guess these things would be impossible to imagine, but is logic just a description of reality, or is reality an implementation of logical axioms?

The laws of logic are true in all possible universes (according to logic.) Can you imagine a universe where 1+1=3? Where someone has one object, and puts it next to another object and suddenly he has three objects? It just makes no sense. The "laws" of logic are not laws in the sense that things like physical laws are laws.

My way about time is: Past and future is like reflections from current moment. Both are changed at will and alter everything at whim. Everything is altered so you don't have so much "Déjà vu", your perception of solidity is altered.

In a moment you have sister, in a moment you don't, but your whole past/future and recollections about that is altered and you have no way of preserving previous state.

Without alterations you would go mad realizing that everything is at the same time.

There must be sensible explanation of what I am trying to day, but I yet to find one.

Might be like looking at busy bazaar from every possible angle at the same time in same viewpoint, or focus down to small opening at one viewpoint how bread is sitting on shelf.

I disagree. Questions like how the human brain works and how we can think abstractly, and how/why humans are so much more intelligent than other animals. There isn't really anything philosophical about it.

"Can science help us comprehend what makes us human?". Now that's a strictly philosophical question.

This idea that science and philosophy are separate things needs to be killed. Philosophy isn't limited to navel-gazing about imaginary things. The scientific method is something that was determined through the application of philosophy throughout the ages. It's the application of logic and the reasoning around how best to determine robust results - this was achieved through 'applied' philosophy. Science and the scientific method relies deeply on philosophy - science could be described as being the business end of philosophy.

And the highest qualification you can get in science is a PhD - a doctorate of philosophy.

http://en.wikipedia.org/wiki/Philosophy_of_science

It's a fascinating question, but I don't see why it is one of the "10 most important questions in science".

>modern humans are the first species that intentionally deprives itself of sleep for long periods of time.

Is that correct? It feels wrong. Plenty of species will endure all kinds of stresses when it comes to survival.

From the article: >Was Freud right about his theory that dreams are some sort of expression of repressed desires?

This one is easy. No. Dogs dream.

more important than "where do we put our carbon". that's an engineering problem, at best.

None of these questions rank anywhere near the top10, at least not in the exact sciences.

Actual top10 problems:

http://en.wikipedia.org/wiki/Millennium_Prize_Problems

(they require knowing more than a little bit of science to even understand the question)

Still the argument "they have their ships therefore they don't need our Earth" is more than shaky. I concur with Hawking: we can definitely imagine aliens who wouldn't blink an eye before they won't care for life of humans, the same way we eat other animals or simply destroy them as the side effect of doing something for us more important.

Almost. Wanderlust. The ebb and flow of disaster and recovery. A pond overflows, a forest burns, a volcano erupts, a comet hits Earth. We always send out the scouting parties and come back. There is no immediate economic logic, just the 1 billion old instinct to check out the next habitat. By Tyma's cold logic, there is no point in tourism, yet we spend 10% of our global resources for an utterly useless activity. Why?

Any life form that can (a) divorce its intelligence from its physical substrate, and (b) forge a sustainable energy relationship with one or more stars, has the capacity to be very, very long-lived. I think if there exist aliens that we are capable of finding, they will be in the form of slow-moving, slow-spreading "Space Ents", beings who are perfectly content to send SYN/ACK messages with 500,000 year ping times. Play out natural selection in the ginormous sandbox that is Universe, and I think that's the only inevitable outcome (barring FTL).

I do not see why there couldn't be a Roadside Picnic - Stalker like encounter: http://en.wikipedia.org/wiki/Roadside_Picnic

True we would not be important, but at least we would know we are not alone.

In order to observe something you have to bounce photons off of it, which changes its behavior...little over-simplified, but I believe that's the gist.

From what I understand, there are two phenomena at play, often mixed together. The observer might interfere when it tries to measure (the observer effect, which is true to any system), but there's also an inherent uncertainty on the way waves are measured (the uncertainty principle).

The observer effect is well-understood, there's nothing magical about it. For example, a multimeter acts a (very small) resistor, affecting the circuit it's measuring. Sometimes the error you introduce can be ignored, but get unmanageable when you try to measure really small systems, where things are more easily disturbed.

The uncertainty principle, on the other hand, is something else. There's a video that I think explains the uncertainty principle well, with a practical example (it's explaining why there's a limit to how many pulses you can send down a fiber optic and still be able to measure on the other side): http://youtu.be/0OOmSyaoAt0?t=7m28s

The observer becomes entangled with the quantum system.

This is still an open question, and a really good one.

The predictive power of quantum theory is amazing; it gives excellent numerical predictions as to the outcome of experiments. But as to how we interpret that, especially the question of what a measurement is, is not at all addressed by the theory, and remains a point of intense discussion and study.