Annoying Questions I'd Like Answered...

[tussock]

The reality of why Tussock is wrong is because nobody measures time like that because it's useless and not indicative of anything; time objectively passes in the universe while you travel at c, even if no time passes for you. It deserves the same kind of groaning and eye-rolling you'd give a bad pun, because that's basically all it is; a pun on how we conceptualize time.

Only it's not. It's fundamental to understanding all sorts of the more complex parts of relativity that most people are never taught. Could you travel at (very near) c, time absolutely (almost) does not pass for any part of the universe, because the outside universe's clocks are (all but) time dilated all the way to zero.

Remember, from your reference frame, it's the rest of the universe that's travelling so fast (and smashing into you with unfortunately large quantities of energy). It's their clocks that are objectively slow. And that's just as true for you as your clock being slow is for them.

Yes, when you assume everyone's taking little trips, returning home again, and only accelerating in a couple short bursts, it's easier to assume simultaneity isn't a lie and measure everything from home base. But it's still a lie.

[name_here]

As I recall, saying FTL implies time travel is not strictly an accurate way of putting it. Basically, FTL, causality, and relativity cannot coexist, only two of the three things can exist. If relativity is accurate, then moving faster than light is actually and specifically time travel, because relative to an observer on Earth a radio message from Mars was actually sent when it arrives or something like that. Basically, the part of the light cones referred to as being in the past does not simply contain information from the past, it actually is in the past. So, if you send a message with no propogation time and get a response via the same mechanism, the response wasn't sent when you sent your message, it was sent ten minutes ago. This goes into proper crazy-town when you reply to that message, because you have now replied to a response to a message that was created before you ever sent the first one and causality goes all to hell. At least, that's what I gathered from the long article explaining this.

[CatharzGodfoot]

"I have travelled 10 light years instantly but it aged the universe 10 years" is a very weird to say "I have spent 10 years travelling 10 light years, but no time has passed for me." I don't know if you can call it incorrect, but I'm not jumping to call it correct either. It doesn't exactly seem right to say you travelled a finite distance infinitely fast only to discover that time has passed for your destination (and everything else) since you left for it.

No. Let me put it in simple terms. The limit of y/x as x -> ∞ is 0. The limit of y/x as x -> C is y/C. In a vacuum, we know C is about 3*10^8 m/s.


So let's compare these two quantities: y/x as x->∞ m/s and y/(3*10^8) m/s.

Let's say you want to go, I don't know, 3*10^8 meters (one light second in a vacuum). The first equation is (3*10^8 m)/x as x->∞ m/s, or immeasurably little time. The second is ( 3*10^8 m)/( 3*10^8 m/s), or 1 second.

Let's change the distance it just so that we can make a rudimentary trend line.. How about we go with 9*10^15 meters this time.

First equation: (9*10^15 m)/x as x->∞ m/s. That's odd, the answer is still immeasurably close to no time at all.
Second equation: (9*10^15 m)/( 3*10^8 m/s). 3*10^7 seconds, or about a year. Wow, I guess there is a pretty big difference between infinity and a finite quantity like C!

Nothing about that is a response at all. I suspect you actually have no idea at all why Tussock said the speed of light is infinite, let alone why it might be wrong (or more appropriately: strange or misleading). That, or you're just being snarky with the simple explanation and not realizing it totally misses the point.

So, let's start off by explaining what Tussock meant: as you approach the speed of light, time dilation kicks in and time passes slower for you but not for everyone else. At the speed of light itself, the effect is complete and time stops. If you turn on your stopwatch, engage your lightspeed engine, reach your destination, turn off your lightspeed engine, and stop the stopwatch, it will read 0.00... seconds. Because for you, you arrived at exactly the same instant you left. Or to use condescendingly elementary math: the limit of d/t as t->0 is infinity, so when you naively look at your mile odometer and your stopwatch, you appear to have been travelling at infinite speeds.

Now, if you had a prearrarranged departure time, and your destination turns on the stopwatch at this prearranged departure time in order to time you, and you are 10 light-seconds away, their stopwatch will read 10 seconds when you arrive. Because the speed of light is 1 light-second per second, and something moving at the speed of light towards them will cover 10 light-seconds in 10 seconds.

The reality of why Tussock is wrong is because nobody measures time like that because it's useless and not indicative of anything; time objectively passes in the universe while you travel at c, even if no time passes for you. It deserves the same kind of groaning and eye-rolling you'd give a bad pun, because that's basically all it is; a pun on how we conceptualize time.

I was going to make a big argument about how, if something is taking a measurable amount of time from any frame of reference, it can't be infinite. But you (and Tussock) are right. I'm wrong. The speed of me walking to the kitchen in a relativistic universe is going to be non-finite, because there a non-finite number of different frames of reference that the walk could be observed from.

My concept of infinite speed (which is probably just wrong), is that, if your destination is a light year away, you should arrive exactly one light year after the light you observed upon departure left the destination. That is, you still can't see faster than light, but you can move fast enough that, if you moved at infinite speed to your destination and then back to your origin, you would arrive at almost exactly the same time that you departed.

[DSMatticus]

The speed of me walking to the kitchen in a relativistic universe is going to be non-finite, because there a non-finite number of different frames of reference that the walk could be observed from.

Well, no. It's going to be finite in all reference frames. That's essentially definitional. It will always be finite in all reference frames until you walk to your kitchen at the speed of light, and even then your speed is finite in all reference frames it's just that your watch stops while you are performing that finite-speed motion. No relative velocity being higher than c is a sticking point of special relativity, and c is definitely finite.

What Tussock is doing is he is defining velocity as change in distance with respect to (personal) time. And it turns out that that is some f=ma classical physics shit that makes a good approximation for daily human life but is totally wrong. The reality is that velocity doesn't measure your movement through space with respect to time; it measures your movement through space and time together. Thinking that you can use your personal watch to measure velocity is naive; that's just not what velocity is in special relativity. It's the four-vector of your movement through the three dimensions of space and the one dimension of time. And its magnitude always, always equals the speed of light (which is why your movement through time stops when your movement through the three dimensions of space is c).

[tussock]

(which is why your movement through time stops when your movement through the three dimensions of space is c)

Nearly there, but there is no movement through space. I'm no more moving past the stars than they are moving past me. While they're moving past me it's their clocks that are stopped, not mine. You're assuming a privileged frame of reference which doesn't exist.

Because it's not the speed of the travelling twin that leaves him younger, it's his acceleration at a distance. Special relativity is just a simplified math trick that works out for a non-accelerating reference frame for your privileged observer (as Newtonian maths works out when all speeds remain << c), but it doesn't work that well for even lightly accelerating reference frames (like the gravity well we're sitting in), nor explain who really ends up younger, because it's not real for everyone except when everyone is in it.


You want different ways to show light speed is infinite? One's called General Relativity. If you know all about 4-vector space-time and the matrix math of it, you should also know what a distant object's clock is set to when you pop up to (nearly) the speed of light: it's already ahead by (nearly) 1 lyr/yr, and you're (nearly) already there because that distance (nearly) all went away when you accelerated like that.

Time (nearly) doesn't pass at home until you pop back down to stopped again. If that's not infinite speed, what is? Time (nearly) doesn't pass for anyone as you travel, only as you speed up and slow down at the ends.

Objects at a distance really are in your future, just as you really are in their future. You and they don't disagree about that, it's just counter-intuitive because the false concept of simultaneity keeps getting in everyone's way.

[DSMatticus]

Wow. Tussock, you are just terrible. I'll get the "you're still dumb and here's why" out of the way, then respond to one of the most infuriating stupidities you've dropped so far because I feel the need to correct it, even if it is unrelated.

Time (nearly) doesn't pass at home until you pop back down to stopped again. If that's not infinite speed, what is?

Definitionally, when the magnitude of your four-vector is equal to infinity. The magnitude of your four-vector is not infinity in this case. You are doing exactly the same thing I just accused you of earlier; you are trying to use an individual's clock to measure velocity, when that is an inherently flawed premise you are bringing from classical physics into a discussion about special relativity.

Nearly there, but there is no movement through space. I'm no more moving past the stars than they are moving past me. While they're moving past me it's their clocks that are stopped, not mine.

You are combining Newtonian concepts of space and time with special relativity to create a heap of stupid. Exactly like everything else you have done, and exactly what I just called you on. Just with space instead of velocity this time. God damnit.

I want to start off by saying: neither space nor motion is the property of an individual object. 10 meters to your left is not something that actually exists, and moving 10m/s to your left is not something that actually exists. Those are both simplifications which are only possible because when you say them, there is a commonly understood reference frame (the static environment around us). Space and motion are equally relative things.

So when you say "x is moving with respect to y is the same as y moving with respect to x", that's correct, but you apparently don't understand why; the reason why is because motion is inherently relative and choosing a reference frame is something physicists do to make physics tractable. The reality is that motion is a two-argument operator, i.e. velocity(x,y)=50. Both objects are moving. With respect to eachother. Choosing to observe the motion from the perspective of one is a simplification, but both objects are "in motion" because motion takes two to tango.

Space is the exact same way. When someone is moving through space, they are not moving through an objective thing which objectively exists. What they are actually doing is contracting or expanding the space (spacetime, really) between them and some other object. I.e. distance(x,y,t=0) =/= distance(x,y,t=1). Space also takes two to tango. There's a reason spacetime doesn't really make sense outside the context of the universe/big bang; because spacetime is just a description of the relationships between the particles of the universe as they currently stand.

What you just said, in all it's stupid glory, is that "velocity can't change the relationship (space) between two objects because velocity can only be measured by how it changes the relationship between two objects."

You and I are 100% done. That is a level of incomprehensibility I am not equipped to tackle.

[MGuy]

I just wanna say that this conversation has blown my mind wide open.

[...You Lost Me]

Agreed.

[Korgan0]

I think a fairly decent argument against the existence of an omnipotent, omniscient, omnibenevolent God is that there's no way that kind of being would have made the universe this confusing.

[DSMatticus]

I think a fairly decent argument against the existence of an omnipotent, omniscient, omnibenevolent God is that there's no way that kind of being would have made the universe this confusing.

An all-knowing god is incompatible with an unknowable universe, and I think special relativity makes it clear enough that nobody could possibly have any idea what the hell is going on in this mess.

[tussock]

If that's not infinite speed, what is?

Definitionally, when the magnitude of your four-vector is equal to infinity.

Shwa? You mean, when things start infinitely distant from each other in space-time? Why? infinity/0 is no more defined mathematically than 1/0.

As far as I can tell, people considering speed want to measure a distance (most simply in a co-moving reference frame like us and nearby stars, or us and Andromeda), and they want to know how long it'll take them to get there. That's what they mean by speed when travelling to work in the morning, the distance to work divided by the time it takes them to get there.

Work with me, man. I was asked for a Barney explanation for why Star-Trek comms don't work and it's not that easy to get away from the page-long math before your terms get all muddy. I started with "time and distance are the same thing", so you can't shoot a signal 2 light years in zero time because 2 light years away is totally also 2 years away. That's true enough.

Then I chucked in the bit about infinite speed. Which is also true enough, if you consider a distant star and travel there with a clock on board. You argue that's a pointless way to measure things to do the math, but it's something people totally want to know anyway, because relativistic rockets would totally get people to Andromeda in their lifetime if it weren't for the radiation. Just a long, long way in the future of us non-accelerating folk.

[Korgan0]

If that's not infinite speed, what is?

Definitionally, when the magnitude of your four-vector is equal to infinity.

Shwa? You mean, when things start infinitely distant from each other in space-time? Why? infinity/0 is no more defined mathematically than 1/0.

As far as I can tell, people considering speed want to measure a distance (most simply in a co-moving reference frame like us and nearby stars, or us and Andromeda), and they want to know how long it'll take them to get there. That's what they mean by speed when travelling to work in the morning, the distance to work divided by the time it takes them to get there.

Work with me, man. I was asked for a Barney explanation for why Star-Trek comms don't work and it's not that easy to get away from the page-long math before your terms get all muddy. I started with "time and distance are the same thing", so you can't shoot a signal 2 light years in zero time because 2 light years away is totally also 2 years away. That's true enough.

Then I chucked in the bit about infinite speed. Which is also true enough, if you consider a distant star and travel there with a clock on board. You argue that's a pointless way to measure things to do the math, but it's something people totally want to know anyway, because relativistic rockets would totally get people to Andromeda in their lifetime if it weren't for the radiation. Just a long, long way in the future of us non-accelerating folk.

I really have no idea what's going on this discussion, but it sounds like that after having your points disproved, you're claiming that from the beginning you deliberately simplified your terms and arguments in order to explain stuff to a layman. In that case, you should probably be aware that the layman doesn't know what "matrix math" is. Secondly, you would have saved a lot of time if you'd said that in the beginning, before getting into a metaphorical fistfight with DSMatticus.

[Username17]

In Special Relativity, everything is always moving at the same speed: the speed of light. Some part of that speed is moving through time, and some part of that speed is moving through space. Actual light moves 100% through space and 0% through time. An actually static object (which doesn't really exist as far as I know) moves 100% through time and 0% through space. Everything else is moving at some vector through space and time, and the more energy is behind it, the more it is angled through space and the less it is angled through time.

This is why the Relativity equations for time dilation and inertial energy and stuff look exactly like the Pythagorean Theorem. Because they are the Pythagorean Theorem. You're literally just breaking a single vector into its components of space and time.

Infinite Speed actually almost certainly does exist, and it is teleporting from one place to another place without passing through intermediate space or time. Quantum mechanics calls for particles to be doing that shit all the time (depending on which interpretation you use - some go to really inordinate lengths to explain away the teleportation with whole extra universes that things are falling out of and shit). It is not possible to accelerate things faster than the speed of light, because there is no amount of energy that you could give something that would convert more than "all" of an object's vector from time to space. Some versions of the math do support the existence of Tachyons, whose vector has some portion of negative time component and correspondingly large spatial components, but they would have to come into existence already at that point - you couldn't convert a non-tachyon object to a tachyon object with any amount of energy.

-Username17

[Avoraciopoctules]

It might be a bit of a long shot, but is anyone else familiar with authentication procedures you need to go through to use ArcGIS 10.0 Education Edition?

[Ted the Flayer]

My roommate and two of his friends (one male, one female) had a rather long conversation in the next room about how they all have rape fantasies.

... Should I be concerned, or VERY concerned? I don't really understand human sexuality AT ALL, but that doesn't sound like something normal people have...

[sabs]

Most people have rape fantasies. Either as the raper or the rapee. It's actually quite normal. And it's no indication that they are psychopaths. That being said, your roomates are ACTUAL psychopaths so.. maybe that should concern you more.

But mostly, you shouldn't be concerned at all. It's quite normal in human sexuality to have rape fantasies.

[Username17]

My roommate and two of his friends (one male, one female) had a rather long conversation in the next room about how they all have rape fantasies.

... Should I be concerned, or VERY concerned? I don't really understand human sexuality AT ALL, but that doesn't sound like something normal people have...

Rape fantasies are actually super common and not in themselves much to worry about. Really, it depends on the context and the content of the rape fantasy. Lots of people like thinking about controlling or being controlled by the person they are having sex with. As long as the people understand that these are only fantasies, and that the reality of raping or being raped would be "horrifying" rather than "sexy", it's just a normal expression of sexual desire.

Fantasizing about running around with a sword and killing bad guys is normal and healthy. Actually running around with a sword, killing people you don't like makes you a psychopath.

-Username17

[Ancient History]

Re: Fearful - Depends on whether they were talking about doing the raping or being raped.

Re: Concerned - Rape (and sexual dominance/submission in general) is a recognized and well-established sexual fantasy, and there are many legitimate routes for your roommates to indulge said fantasy without, y'know, tying you down and sodomizing you to death over a period of days.

[Ted the Flayer]

I mean, I can't say that I haven't done a little BDSM at times, but it was consenting by all parties involved and everyone respected the safe words. It doesn't feel like the same thing in my mind; thinking of actual rape gives me... unpleasant flashbacks. Then again, I don't really know people.

[Lago PARANOIA]

So why do/did the Scandinavian nations have a lower Gini coefficient than actual Bolsheviks/Maoists?

And also, how come the Scandinavian nations kick so much ass? Or rather, how did they get to that point, historically speaking?

[sabs]

Cause they're fucking Vikings?

[Lago PARANOIA]

I didn't know that Erik the Red championed an exhaustive system of universal healthcare a couple of decades before mainland Europe. And I was doubly surprised to learn that Hagar the Horrible had a progressive but counter-intuitive approach to criminal justice that ninjakicked recidivism in the nuts.

[Ted the Flayer]

Am I the only person slightly concerned that people are extolling the superiority of a culture that's nearly all blonde-haired, blue-eyed white people? Something doesn't sit right with that... (lol)

[Stahlseele]

The Vikings WERE superior in their Time.
Part of the Reason why Hitler said that Whites are superior.
Because he looked at the northern cultures and saw that it had been true for quite some time.

[Ted the Flayer]

I don't know, they ARE susceptible to crippling knee injuries...