Greg Egan actually tackles this question with a great amount of rigor (he's also a mathematician) and clarity in his short stories and novels. Highly recommended.

Yup, let's assume that 'teleportation' is just instantaneous destruction followed by accurate re-production of the cell in question. So you feel that the destruction of the physical cell matter makes a difference - let's mix it up then.

What happens if 99% of the cells are transported by normal means, and 1% are teleported (i.e. destroyed and recreated.) Still the same person, right?
What happens with escalating percentages? Do you stop being the same person at the 50% mark? The 20% mark?

So let's say a doctor puts you into an induced coma, freezes you, manually moves each of your cells individually across the room, then reassembles them while preserving all connectivity between cells. They then thaw you out and restart your heart. Are you the same person?

What if, instead of moving each cell across the room, the cells were transported to another location via a hypothetical teleporter - and a doctor at the other end re-assembled you according to the same process. Would you then be the same person? What is the real difference between the two methods of re-assembly?

Final scenario. You slide one meter to the right on a rolling office chair. All your cells have been translated in one spatial axis by one meter. Are you still the same person? How can you be sure?

Thank you for sharing your position in such a clear, non-combative, and well-reasoned way. By your definition, which is a fair one, I would be an agnostic. However, I would choose, for clarity's sake, to call myself an atheist - and here is why.

You define an 'agnostic' as someone who holds no opinion on the divine. While this differs with the common dictionary definition, I believe it is a good definition in its own right. Yet, your position seems to be one where you seem to prefer to be accepting of those who profess a religion. Personally, I see this as an opinion on the divine in and of itself - the opinion that it is reasonable for someone other than yourself to hold a belief in the divine.

In a hypothetical world, let's say there are those who believe that their world is supported on the back of a turtle, those who believe that can be no cosmic turtle, and those who profess that it is impossible to know either way. Let's say that the inhabitants have in fact no way of obtaining evidence for or against the existence of anything beyond their planet's atmosphere. Those who say that it is impossible to know are in fact correct, but there is really no reason for them to respect the opinions of members the other two schools of thought! That would be tantamount to neither agreeing nor disagreeing when presented with an argument that had no evidence or basis. A reasonable person would disagree! If this were not the case, we would be smiling and nodding at every person who made an unwarranted argument.

You may ask, "What is the harm in being non-judgmental when presented with an unwarranted argument or claim?" Well, I propose that in the extreme case, you'd end up having to agree that any given claim was at least possible. "Four-leaf clovers bring me luck" - might be true! This is pretty much unfalsifiable. "Twinkies double your odds of getting cancer." - You'd have to give this claim credence, until someone funded a double-blind study - which probably won't ever happen. Et-cetera, et-cetera.

Sorry for my rambling argument - but I hope you can catch my drift. What I want to say is that, just because we cannot falsify a theory, does not mean we should give it any credence - we should treat the unknown as what it is - unknown. And because pretty much all human thought, reason, and action functions on the basis of evidence or simply past experience, something that is unknown and unknowable should in my opinion simply be classified as non-existent.

(Sorry for my poor argumentation, but when I say non-existent here, I don't mean it as a hard statement, but rather that we should prune the idea from our ontology - in the same way that we don't say that there "might or might not be invisible rubber-duckies in space" or that there "might or might not be a monolith on Europa" etc.)

Sure, everything is a "belief" just like everything is a "theory," but that's just playing with semantics. I agree that you CAN'T verify ANY empirical fact beyond a shadow of a doubt, but that doesn't mean you imagine everything will lose its mass tomorrow and you'll just float off into space, right? (Among a multitude of other possible scenarios)

You're not making the distinction between reasonable belief and unfounded or poorly founded belief. Reasonable belief follows a chain of reasoning that is at least based on empirical observation and extends some level of trust to other people to make reports about empirical tests to us. I.e. we observe that people with such-and-such traits are generally not liars, and people who publish fake papers are found out at a rate of X%, therefore we have a certain level of confidence that what we read is actually what was observed by these people. A chain of trust, which is != to a chain of blind trust.

tl;dr It is reasonable to believe that on average, scientists, unlike shamans, perform empirical tests before making claims.

Parent is modded +5 Insightful?! Since when did Slashdot moderators develop an anti-science bent?

Please tell us how it is a better idea to trust an unsigned site at the other end of an unencrypted connection MORE than a self-signed site at the end of a SSL connection. If sites with self-signed certs trigger a warning on browsers, then every site served in the clear should as well. A good compromise would be not to display the lock icon for sites with self-signed certs.

This is the first time I've really wished I had mod points! Nice post.

I wrote a simple prototype for this back in the '90s, and submitted a marginally upgraded version as coursework circa 2002. On hindsight it's not a terribly useful system, it defends against shoulder surfing and not much else. My feeling back then was that a scheme such as this would be useful for ATMs, but given the sophisticated camera + card scanner attacks being employed today, I doubt it'd be much use.

Meta-irony for the win.

I'm currently teaching myself linear algebra with the aid of Khan's videos, and I couldn't be happier with the quality of the material.

The fact that his work is steadily garnering more attention is a good thing in my view, since it increases the likelihood of more excellent videos being made available for free as a result of donations, grants, etc.

Seems very much like the radio chess sets that saw some popularity in the late '80s.

No. Think about it - in space, to "slow something down" means the same thing as "speeding something up," that is, changing an object's velocity (commonly known as acceleration.)

As such, you'd have to spend energy to accelerate toward your target, and when you were about to reach it, decelerate (i.e. accelerate in the opposite direction) in order not to go past it.

Another way to think about it is that in your inertial frame, you are always resting. So there is no kinetic energy to "absorb" to slow down since you aren't actually moving, from your point of view. Of course, that small planetoid in front appears to be moving towards you at a large rate, but good luck "absorbing" the kinetic energy from that impact :)

Bah, 65TB? Wait till they discover what's in /dev/rand! I wish the cryptanalysts good luck!

Like how inflammable is more than... flammable?