Why nothing can go faster than the speed of light
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It appears that these patent clerks with no scientific credibility are some of the few great things the patent office has bestowed upon us.
This is the person who jumped to mind first.
I don't particularly care about "karma", so what bothers me is not that the original commenter didn't get enough points, but rather what people in the community think it's important in a conversation.
Oh meh a new website someone wrote. Nothing new... Holy cow it says it was written by a woman upvote! Well done her! Amazing!
This attitude (and your response to it) goes a long way to explaining why computerland is such a sausage party.
> There's no reverse sexism at play here, just good old
> fashioned regular sexism, where a commenter assumed that
> the author of something insightful was a man.
> This attitude (and your response to it) goes a long way
> to explaining why computerland is such a sausage party.
I honestly cannot wait for the many articles explaining how to make one in pure CSS.
Why would you say that? We're all adults here.
And do we need more men in 'relationship advice'? Only if they want to be there.
I really wish this ridiculous and unhelpful "There's no women in tech because of evil men" meme would die.
Um... in what way is it not a sexist assumption?
> I really wish this ridiculous and unhelpful "There's no women in tech because of evil men" meme would die.
Evil? No. Sexist: a thousand times yes. The culture of technology, and especially startups, is quite frankly vile in this regard.
Is it the sole cause of "no women in tech"? Almost certainly not -- but I find the rampant sexism plenty objectionable in its own right, regardless of (speculated) effects on diversity.
Because it's statistics. 99%+ of relationship advice columns are by females.
Is it sexist to give women lower rates for car insurance? Is it sexist to give men different rates for life insurance? I would say absolutely not. Women are safer in cars, and men die younger. Those are facts. (FWIW The interfering EU are due to vote on 'sexism' within insurance shortly)
(If a culture or community does allow this to happen, then any slight tendencies will be artificially magnified and reinforced into an unnaturally lopsided distribution.)
Side notes: I put 'statistical' in scare quotes above, as it's all to easy to pull self-justifying statistics out of your ass, as you did.
People should grow the hell up and stop being offended by everything.
It's an adult's place to speak up when they think something is wrong. And I'm sorry, but some things are worth being offended over.
http://www.aip.org/statistics/trends/highlite/women3/faculty...
[1] It was noted by many, while discussing demographics of Wikipedia, that women are less willing than men to contribute to the intellectual commons, particularly on sites which are not walled gardens. If this fact generalizes, we would expect women Physics PhD's to be underrepresented among people writing about physics.
Judge things on their merit. Seeing posts upvoted simply because they're made by females is sad.
And it will only perpetuate the problem or even make it worse, because it makes it harder for women to get the recognition they deserve.
You might say that the recognition they deserve is equal recognition. I would agree. IFF they were currently getting equal recognition, then everything you say about giving them extra recognition would be true. It would be condescending, belittling and sarcastic.
The problem is though that they don't get equal recognition. So until the day they do, you can put that "condescending, belittling and sarcastic" attitude right back where you found it.
This debate reminds me of the failed 'Women only shortlists" debacle in the UK under the Labour government, where they put forward only Women candidates, in order to get more women MPs. Regardless of their merit to actually do the job.
Hence in my opinion; recognition is the currency of hackers, and thus while it is the unfortunate case that in many areas women are under-recognised... it is particularly egregious when this happens in the technology arena.
Giving someone that puts thought, time and effort into a response a tiny bit of karma - and then having the 'correction' which involves neither time, nor effort, nor thought 10x the amount of karma indicates a couple of things:
(1) Hacker News will rapidly descend into one line reply chaos where it is nigh impossible to have an interesting discussion
(2) Hacker news does not value time effort and thought
(3) Hacker news greatly rewards the absence of time, effort and thought
How can any of those be good? (#2) is the antithesis of reasoned debate, (#3) is actively rewarding anti-intellectualism. (#1) indicates that HN is either just a poorly implemented version of Slashdot (which would be sad) or it is going to descend into diggery (which is horrifying).
Put some thought into it and you might see why we have a problem with that.
> [...] and then someone writes a one line 'toss off' reply, and rakes in the free karma. This is the utmost BS.
I should hope that the HN community doesn't impulsively ascribe so much value and pride into winning some system of karmic points. I don't. I think it's a non-issue. And because of the HN interface being so sleek and minimal, we can at least afford to have a few one-liners here and there without wasting a significant amount of screen space.
Lastly, I would like to point out that my comment at least was not a derisive or snide one but one of an observation/correction which I thought was worth the trouble pointing out. But, again, I do regret not supplementing my comment with more substance.
You also seem to be labouring under the misconception that the quality of a reply is proportional to its length. However, a short, pithy remark that cuts to the heart of an issue is far more valuable than a long-winded argument that makes the same point.
Why? I don't see why it should be relevant at all!
(I am aware that singular 'they' is grammatical. Doesn't stop it from sounding really awkward when the referent is a specific individual.)
I'm not offended by people incorrectly using gender pronouns, it is just really awkward to write something without knowing the gender of the person you are talking about.
http://en.wikipedia.org/wiki/Gender-neutral_pronoun#Historic...
In particular:
>The singular "they" is widely used and accepted in Britain, Australia, and North America in conversation and, often, in at least informal writing as well. It is important to note that this is not recognized by the SATs and other standardized tests.
I do boggle that "they" isn't technically acceptable for cases where gender isn't known, though. "He/she" seems like insanity, both in writing and in speaking, when "they" sits there waiting to be used. It's extremely rare that context isn't sufficient to determine if it's plural or not. Heck, Japanese essentially does without plurals entirely, and that's a functioning language.
Correction:
"Someone replies to it only to nitpick"
/humour
should be
"but rather that people..."
or
"...think is important in a conversation"
For the record, I agree, but enjoy irony.
http://www.reddit.com/r/askscience/comments/flzut/i_have_som...
More of her best-of comments would be most welcome. And, MORE THREADS LIKE THIS PLEASE.
> For right now, if you just believe that four-velocities can never stretch or shrink because that's just the way it is
In other words, nothing can go faster than the speed of light because that's the way it is? The author needs to explain why the magnitude of this four-velocity vector is the speed of light! I was hooked after the first few paragraphs, but then felt like it dead-ended in a circular argument.
Someone else wrote my favorite answer: "Basically, the way to think of it is not that light is the fastest thing, but rather that there is a speed, c, which the geometry of space and time demands is the fastest possible speed.
One can also work out that anything without mass must travel at this fastest possible speed c. Light is one of those things, therefore light travels at c. It's only an accident of history that we call c "the speed of light": that's the context we discovered c's existence in.
As for why it's the speed it is, well, it's the speed in our universe. It's actually much more natural to say c=1 and all speeds are then unitless numbers between 0 and 1. From this point of view c is 300 Mm/s because of how we chose to define the meter and the second." http://www.reddit.com/r/askscience/comments/fjwkh/why_exactl...
> The meter is the length of the path travelled by light in vacuum during a time interval of 1/299 792 458 of a second.
So I guess that means a meter is 30.66331898849836976219 cesium-133 transition periods.
Hope you can help me with a couple: why is there even a limit? how do we know there is an insuperable barrier nothing can cross for sure?
We have models that describe the world very well, but those models are never the whole truth (and even it were, we couldn't be sure of it).
Special and General Relativity are experimentally very well tested, and these theories predict that a particle that has a speed < c can never acquire a speed > c. There are solutions for speeds larger than c, but those solutions are quite weird, and can't interact with "normal" particles.
But the mere scientific approach of observing facts, modeling and verifying means that one can never be sure that something can't be - only in the limits of the models can we be sure that a thing can't be.
C and pi are similar also: c would be different, if the universe's geometry where scaled differently, even if meters and seconds were unchanged in transition to the alternate universe (assuming one can formalize what I am saying in a sensible way). Likewise, pi (circumference divided by diameter) would take a different value (or not even be a constant) in an alternate (non-Euclidean) geometry (assuming that a circle could still be defined there, which is more obviously possible than the c/spacetime hypothetical)
The only reasonable answer to the original question is: we don't know. The whole schizofrenic theory of something that can be waves and particles doesn't make sense right now but that's the best we can come up with. Nothing can go faster than light because our equations tell us so but we don't know the mechanisms, exactly as we don't know what is creating gravity, for instance. Physics is full of deep mysteries still.
Have you ever read the book QED? It's Feynman's best effort to explain Quantum Electrodynamics to a layman. In the book, he takes a genuine question about the nature of things (how does light work?) and answers it by "bringing up paper and arrows!" (I encourage you to read the book to see what I mean). Feynman disliked "explaining" nature with inaccurate and irresponsible metaphors. But arrows are the way it really is!
On a margin note, the best book I've read about explaining modern physics to the layman is this: http://www.amazon.com/Evolution-Physics-Albert-Einstein/dp/0...
Bringing in arrows where they don't belong, or in the magnet case "rubber bands", is cheating the asker. I'm not familiar enough with GR to know if arrows are a useful representation like they are with complex amplitudes.
* My understanding before: light has a constant speed and nothing can exceed that speed, but up until that limit everything can travel at a variety of speeds.
* My understanding after: everything travels through space-time at a constant speed. Light is "special" only in that it travels exclusively through space and not at all through time.
For me the easiest answer is to understand that from the point of view of the person travelling near the speed of light the beam of light moves away from them at the speed of light. So after ~1 second they are 300,000Km apart.
On the other hand, from the point of view of a 'stationary' observer, the light and the spaceship emitting it are moving at almost exactly the same speed. So after ~1 second they are maybe 1 meter apart.
How can this be? Our minds naturally want to reject this as nonsense. But the thing the gripping hand is holding that makes this true is that to the stationary observer and the person travelling near the speed of light time is moving at different rates.
The person who is moving ~1m slower than the speed of light is experiencing time enormously much slower than the person 'standing still'. The time difference is 300,000,000 times (sic).
Our brains reject this, because we think of time as an absolute rock solid constant, when in fact even with our primitive understanding and slow speeds we can demonstrate experimentally that time is in fact flexible, and it does slow down the faster you get.
A primary insight to general relativity is that it makes no sense to define location (or motion) except relative to an observer. This means there's no "true" position or motion, simply an infinite set of equivalently meaningful but disagreeing ways to observe them.
(For interest's sake, acceleration is the lowest order local phenomenon. An object does not need an external observer to measure it's own acceleration due to the appearance of locally measurable "forces".)
So the answer is to excise "in reality" and then state that both answers are equally meaningful and correct.
The problem I have with light as a unit of reference is that 'perception' is not the same as 'reality' in the physical world.
From the perspective of an Earthbound observer, the photon emitted by the ship will travel from 600kkm away to 300kkm away in one second. (Actually the observer cannot see the photon until another second elapses and it collides with him on Earth.) This observer will see the ship and the photon moving almost together, the ship slower by whatever infinitesimal fraction of c.
From the perspective of a shipborne observer, the photon emitted by the ship will travel from 0 kkm (away from the ship) to 300kkm away also in one second. How do we reconcile this with the knowledge that the Earthborne observer sees the ship and the photon staying together? Length contracts in the direction of travel. So the shipborne observer's meters are very short. The small distance perceived by the Earthbound observer is perceived as a 300kkm distance by the shipborne observer. http://en.wikipedia.org/wiki/Length_contraction
In general, this is how you resolve paradoxes in relativity: work it out from the perspective of each observer and understand that there is no central objective reality. You will find that you made an assumption that does not hold true across both observers.
http://en.wikipedia.org/wiki/Ladder_paradox
If you can wrap your mind around the Ladder Paradox, you're well on your way to understanding space-time transformations in relativity. The key to the ladder paradox is that there is no such thing as an objective standard of "simultaneous". Simultaneity is specific to each observer; two observers perceive the simultaneity of two events differently.
From the astronauts points of view only 1/300,000,000th of a second will have passed. They are going to smack into the planet and won't even know what hit them. The resulting explosion will make Tunguska look like amateur hour with a whoopee cushion.
Your astronaut toggling the lights in their spaceship is experiencing time at a wildly different rate than the 'stationary' observer. We can't just say "well duh, just look at the watch or clock" because those are also slowed down by exactly the amount that the astronaut is slowed down.
How can this be? Answer, as the grandparent said: time is passing differently for the person on the spaceship than it is for the person outside. It is passing in such a way that, for each of them, the speed of light is exactly c.
(edit: corrected 300km to 300k km)
http://en.wikipedia.org/wiki/Frame-dragging
It causes satellites around earth to move a few feet each year.
Tried to find a better source but this will do for now:
http://articles.cnn.com/2004-10-20/tech/warped.space_1_black...
-- We figured out a few things about electric and magnetic fields. In particular, a changing electric field creates a magnetic field and a changing magnetic field creates an electric field. So if you setup a changing electric field in a specific way, you can setup a cycle between the two field types. Now, these fields hold energy and by virtue of this cycle, become capable of carrying away this energy - what we call "light" - just as waves on water carry energy away from the starting point at a certain speed. The strange thing about E and B though is that this "speed" is a constant that is independent of the reference frame you choose to monitor it. In other words, this wave would move at the same speed relative to you no matter how you happened to be moving and you can therefore never "catch up" with it. Therefore no "thing" (matter) can move faster than light. --
In physics, recursive "why"s always lead to "that's the way it is" tautologies. For instance, if atoms are mostly empty space, why don't we fall through the floor? Pauli figured out that no two fermions with same spin state can occupy the same space. Why can't fermions do that? They are spin-1/2 particles and their wave function amplitudes cancel out if you account for the fact that fundamental particles of the same type are indistinguishable. Why does the combined wave function cancel out? .. 'cos that's what seems to agree with experiment - i.e. because you don't see people falling through floors.
Progress seems to be about trying to extend this "explanation chain" by one step more. So string theory can step in and add "because vibrating strings, which is what we're made of, behave like this" .. and then it stops at some point again.
Second, several people have complained that RRC avoided the underlying question by saying "the arrow is always the same length". I think they may not be giving that answer the credit it deserves. Her claim isn't that the speed of light is the longest possible arrow (which I agree wouldn't help at all), but rather that every object's arrow has exactly this same length. That shifts the speed of light from being an arbitrary constraint to being simply a label for this universal fact. The question "Why is every arrow the same length?" is still valid, but there's much less reason to worry about it: no known process can change that length, just as no known process can change the rest mass of an electron.
I found these answers to be more informative: http://physics.stackexchange.com/questions/2230/why-and-how-...
WHY can't the arrow stretch? That is the crucial question; that is the original question. The original question was not "is there/why is there a tradeoff between space and time." The question was "Why can't the arrow stretch, why can't we go faster than light allows?"
"you change your direction of motion through spacetime, but not your speed of motion through spacetime."
This is article a long-winded way of restating the question, and leaves the reader thinking they know the answer when they simply have a different understanding of the same problem.
It's worth thinking a bit about what a satisfying answer might be like for you. Maybe there just isn't a way to understand or think about the question that's satisfying.
Again, of course, this brings us to the question of why the universe is this way: why it is Einsteinian rather than Newtonian. But that question really belongs to the realm of metaphysics, not that of physics.
The universe is Einsteinian because otherwise e could not equal mc2.
And if that were the case then stars could not shine, and a TON of other things would not work. Atoms could not exist either.
The reason is that as you go faster you have more energy (obviously) and since you have more energy your mass increases. Since your mass increases you need even more energy to increase your speed (since now you weigh more).
Take that to the limit and you find that as you reach the speed of light your mass goes to infinity.
So it's necessary that it's impossible to exceed the speed of light - for example if you had two objects each traveling at 51% of the speed of light (relative to third placed in between them). Then relative to each other they are going faster than light - which means they have more than infinite energy.
Can't do that.
So relativity is necessary if you want mass to be interchangeable with energy.
http://en.wikipedia.org/wiki/Velocity-addition_formula
Surely you must read up on modern physics a little bit, sir!
I was explaining why that is necessary if you want e=mc2
For example if you had two objects each traveling at 51% of the speed of light (relative to third placed in between them). You only gave them a certain amount of energy, but if speeds were additive and you compared them then it would appear that their comparative speed was greater than the speed of light!
And that would imply an infinite amount of energy, which would be a problem.
Even if they were each traveling at 49% of the speed of light, so there are no issues of infinity, it takes a lot less energy to accelerate two object to 49% of the speed of light than it does to accelerate one to 98% of the speed of light (because it's a lot heavier when it's going that fast, so it contains far more energy), so you would have issues with conservation of energy.
Because of all that, speeds are not additive, and they get adjusted in a way that keeps conservation of energy exactly correct.
Therefor relativity is necessary if you want mass to be interchangeable with energy.
Please take a look at a very simple relativity homework solution to see if you misunderstand the math or the concepts of relativity (that happens to be the top result for "two spaceships approach each-other" on google)http://www.phy.duke.edu/courses/143/homework/hmwk3_solutions... [It's problem #2]
I'm trying to show why relativity is necessary, I'm not trying to explain relativity.
I'm giving an alternate universe where relativity does not exist and showing why that universe could not work. And because it does not work, relativity is necessary.
Please go back to the original question I am answering: Someone wanted to know why the world is Einsteinian not Newtonian.
"Increasing mass" inevitably leads to so-called "perpendicular mass" which must change and "proper" mass which must not change for equations of motion to stay correct.
This "perpendicular" mass is unphysical.
It's better to leave this concept.
Rest mass is invariant, but the real mass, i.e. the one that makes it harder to accelerate, and that gives inertia, is not.
"""
If you're moving through space, then you're not moving through time as fast as you would be if you were sitting still. Your clock will tick slower than the clock of a person who isn't moving.
"""
There is no such thing as "moving through space". There is only moving relative to another object. And BOTH of your clocks tick slower! Relative to each other.
And if you would stay, say for a minute in that speed and go check on the standing person, you will perceive that she is aging very fast.
And if she checked you YOU would be the one aging very slow, since she is standing still and you are moving fast.
You are still thinking in terms of absolute motion "you're moving". You are not moving, you can only compare your speed with someone else's.
But if he accelerates then things are quite different, and much more complicated.
I used to think about it as I explained in my previous comment. But now that ars is making these comments, it seems like I'm grasping something new.
This FIRST thing to remember is that you can only measure speed by comparing with something else. There is no such thing as the concept of "I am moving", but rather "relative to them I (or they, it's interchangeable) are/am moving".
Now when you compare speeds you can also compare clocks, and the same principle applies - you can only measure time by comparing to someone else.
Acceleration can be measured without reference to anything else. If you are in a box and accelerating you can measure it - it feels exactly like gravity.
He feels that gravity, they don't.
Despite the upvotes on reddit, this really is a topic that can only be done justice by good book or instructor. Any self-respecting library should have a copy of Relativity: The Special and General Theory by Einstein, it's written specifically for the layman. Come to think of it,... I should probably pick it up again myself.
Similarly, rotation rate isn't relative. Acceleration and rotation rate can both be measured against absolute states of no acceleration and no rotation (respectively). This is why our phones have accelerometers and gyroscopes which are entirely internal, but determining velocity, position, and direction require the external references provided by GPS and compass.
Therefore, you can measure acceleration with nothing but equipment (a simple spring-scale will suffice) in your car (reference frame), but you can only measure your speed relative to something outside of your car (traditionally, the road).
Newton's first law (inertia): an object in motion tends to stay in motion. This gives rise to the idea of an "inertial reference frame" which is the idealized reference of a hypothetical object in motion. In simplistic terms, if you pretend that the Universe is merely Newtonian in nature and contains a preferred reference frame then you could imagine that an inertial reference frame can be described by a velocity vector (a speed and a direction). If an object has zero speed relative to the inertial reference frame that will tend to continue to be true so long as no forces intervene.
If you induce an acceleration on an object you will change it's velocity. In it's initial inertial reference frame it will appear to be accelerating. In any other inertial reference frame it will also appear to be accelerating.
There is no such thing as an accelerating inertial reference frame precisely because such a frame is not inertial, it would imply that forces are being applied to the objects involved. The laws of physics make sense if you apply them within any inertial reference frame, but they don't make sense in accelerating reference frames (mass, energy, and forces become inconsistent and confused).
Does that make sense?
I think you're missing the point here. She's not trying to teach people the perfect semantics, she's trying to progressively teach them concepts that are tricky to understand and assimilate, step by step. And in a way they can relate to.
By the way, she addresses what you brought up in her first followup (with yet another compelling and easy to understand explanation).
And addressing something in a followup is no good - fix your initial post to be correct in the first place. Reddit allows you to edit your post.
And why is a follow up no good? She didn't follow up to fix anything. She followed up to follow up. (And mentioned it by, yes, editing her article).
In my opinion, she failed to properly do that and crossed the line between "helpfully simplifying" and "incorrect".
Can you point out exactly where she crossed the line in your opinion?
And for him/her to explain things in such a way is a MASSIVE disservice to you and makes it very hard to learn it correctly later.
And it's not even your clock that ticks slower - it's theirs.
And be careful saying "accelerate from each other", once you start including acceleration things become much more complicated.
Utterly inaccurate and incorrect as the Newton's second law? :)
http://en.wikipedia.org/wiki/Hawking_radiation
Put simply it works like this: light travels at a constant speed, but due to quantum uncertainty nothing is in one exact place, it 'teleports' around an average point. Thus, if it 'teleports' in the direction that the light was travelling it has moved faster than the speed of light.
It's a strict limit, not an average. It's just that the quantum world has strange definitions of location.
Yes, but those fluctuations average out very quickly.
That works in space; that does not work in time. You can't stop moving or change direction in time. You can put X and Y on that grid and have something meaningful, but you can't say it's X and T; that would imply the ability to freely move back in time or forward at your discretion, which is not true.
A simplified explanation of space and time's actual shape is that when you are at (3, 4) and you are moving through time (in the first coordinate, let's say), you've got lines that lead to (4, 4.1) and (4, 3.9) and so on, but the lines only go to a certain angle, which for simplicity's sake I'll say is the obvious 45 degree angle, which means you've got lines that go to (4, 3) and (4, 5), but nothing else below 3 or above 5. You can only move along those lines, and as there is no line to (4, -2) from your start position, there is no way to get there. The bound of those lines is the speed of light. The pictures of the "light cone" you may have seen are in some sense not merely a helpful picture but actually a true picture of the universe.
You can not move faster than the speed of light because you can only move between connected points in the universe, and to move faster than the speed of light is to bypass that restriction. The universe is literally not shaped that way. The shape of the universe forbids faster-than-light. You don't have any choices other than those lines and none of the lines go faster than light.
This is a grotesque simplification, but I think the core point is accurate. Exceeding the speed of light is impossible for reasons above and beyond the mere "exceeding the speed of sound" or other things were. To travel faster than the speed of light requires changing the shape of the universe. (And to the extent that certain theories permit it under some circumstances, such as the Alcubierre drive theory[1], I suspect that we'd find that even if we could implement one of these things the universe would still find a way not covered in those theories to shut it down, cosmic-censorship-style[2], or like [3]. I would also note that all "practical" FTL drives proposed to date have inevitably required the existence of at least one impossibility, such as stable negative mass, and it means little to prove that if I have one impossibility like stable negative mass I can have another like FTL.)
Also, because this is a grotesque simplification, please note that picking apart holes in my picture is not even remotely the same as picking apart holes in the theory of relativity, let alone picking apart holes in the Universe. In particular don't get caught up with things that may appear to be going backward; that's an illusion of this attempt to embed an explanation into Euclidean space, not a real problem with the physics.
[1]: http://en.wikipedia.org/wiki/Alcubierre_drive
[2]: http://en.wikipedia.org/wiki/Cosmic_censorship
[3]: http://books.google.com/books?id=_mo4AAAAIAAJ&pg=PA132&#... (reading pages 132 and 133)
"Scientists Make Radio Waves Travel Faster Than Light"
article:
http://www.universetoday.com/33752/device-makes-radio-waves-...
the paper it's based on:
http://arxiv.org/abs/physics/0405062
Anyone with a Physics background care to comment on the validity of this study?
I really wish Instapaper worked with reddit comments. Lots of good reading there.
Why maximum limit exist at all? How Universe without this limit will look like? How Universe with limit which is not equal to speed of light will look like?
Antropic principle inevitably pops up.
In order for e=mc2 you are required to have relativity. And a world without that could not exist.
If you are asking why the limit is this specific number then no one knows. But then again we don't know the reason for any of the constants.
Compared to yourself you are always standing still, and your clock always ticks at what you think is a normal rate. Other things may be moving relative to you though and THEIR clock might be slow.
(Unless you accelerate, in which case things get more complicated.)
The salient thing is that there are three disconnected classes of 4-vectors: timelike (massive particles), spacelike (tachyons), and lightlike (massless particles). Lorentz coordinate transforms can only take you between 4-vectors of a particular type: e.g. there's no inertial reference frame where timelike motion looks like tachyonic motion.
If I am in a Reddit mood, I will go to Reddit. If I'm more in a HN mood, I will come here.
For myself, I don't visit Reddit unless there's something interesting linked to from elsewhere, such as HN. Thus, I appreciate this being posted to HN.
Your reasoning is flawed. The value of HN is its community and the discussions it's capable of spawninf. There are sites for discussing an ampler spectrum of subjects (like, for instance, the nature of the universe and laws of physics) and sites for discussing news that interest specifically to hackers (according to the definition implied in the "Hackers and Painters" book).
I, obviously, have an unpopular opinion.
You mean, like when its name was changed from "Startup News" to "Hacker News," maybe?
This article, though, isn't one of them.
There are two space ships which are built like these russian matroshkas. One smaller space ship is in the hangar of a bigger one. The bigger one starts from the earth and accelerates to the speed of light (or just until 0.999c). Now, the smaller ship starts and can again accelerate from the bigger ship point of view until 0.999c. So, if there is just a simple velocity measure instrument, which is measuring acceleration by F = m*a, and we know the relative space ship mass "m" as it was relative to the earth, then knowing how much force our engine produces we can compute the acceleration. And hence our velocity measurement device will add small "a" to the current velocity by every thrust of the engine.
So given that type of measurement, our smaller space ship can accelerate to the speed of 2c relative to the earth. HOWEVER, due to the relativistic effects the people living on the earth would never ever realize that this ship was moving with 2c, since they are measuring speed by looking how far the ship went in the certain amount of time. And due to the time dilation they will never realize that this ship was actually much farther away then it looks like.
So, regarding to this experiment, we can travel faster then the light. However, this is only due to the definition of the speed.
A counter argument would be that the mass "m" is also changing. However, one could argue that the mass is represented by the amount of particles per volume unit and hence remain constant if volume remain constant. Ok, another guy could argue again that the size of the volume shrinks, but I could then argue that if size of the volume shrinks, then the density of the particles per volume unit from the earth point of view would increase and could end up in a singularity or just black hole, so big bang ?:confused:
This kind of experiment fits well into my experience of the world, where I just cannot accept some of the constraints we get from the nature :) Yes, you cannot travel faster then the speed of light, BUT this is only because I stay at the earth and measure your speed by looking how fast you come back. But this pure guy who is traveling could measure the speed as I've proposed and would then realize that, in deed he was faster then the "earth's speed of light" :)
I never claimed that speeds are additive. I've just claimed that it fully depends on what you define as a speed. If you define the speed the classical way (space unit per time), then due to the relativistic effects, it will never work out for you.
However, and this is the point, if you define the speed as just some counter running in front of you which add a value on every engine thrust, then it will work out for you that you are traveling faster, then the "earth's" speed of light!!!
Imagine just another experiment. You are waking up at a space ship and there is nothing around you where you can fix your view to see if you are moving or not. So, the speed-counter on this ship shows you 0.9c (here c is "earth's c"). No, you press the accelerate button and accelerates to additional 0.2c. There is nothing which would stop you accelerating, because in your frame you can assume that you are at rest! So, adding now the new velocity amount to your previous you get 1.1c, HOWEVER, this the "earth's c" ,so the speed of light as it is measured on the earth!!! In your frame, since you have no clue if you was moving or not, you should assume that you have now only 0.2c or just 0c, since you cannot measure the speed in the classical way anymore (there is no other point to fix on).
So, this is the way how to understand the relativistic effects. There is no "super-dooper" spaghetti-monster hand, which will for some reason stop you accelerating. No, this is just because everybody around you will never be able to measure your real speed, because they can only measure the speed relative to their frame.
Matter is form of electromagnetic wave, thus matter cannot travel faster that speed of electromagnetic wave in medium ("vacuum").
Everything that is not a form of electromagnetic wave, OR disconnected from electromagnetic medium, will be not bound to speed of light.
Imagine water and water waves. Water waves will never travel faster than speed of wave in water.
BUT, you can freeze water and push it faster than water wave just because it is not a part of water anymore.
I hope, super-cold vacuum (below 0K) or matter in cocoon of super-cold vacuum will be able to travel faster than speed of light.
PS.
Of course, I cannot even imagine, how we can freeze vacuum, because we cannot even interact with it.
The speed of light has to do with the nature of reality, not the method of transportation.
We already know, that vacuum can generate particles, thus it is not completely empty:
http://scienceblog.com/40901/theoretical-breakthrough-genera...
You can find much more information about faster than speed traveling here: http://en.wikipedia.org/wiki/Faster_than_light_travel .
You seem to want to talk about theoretical ideas that have no evidence.
You quite misunderstood that article, it's not the vacuum that produces the particles, it is the massive energy they are beaming that produces them.
The stuff in the wikipedia article is just ideas that may work mathematically but have little bearing on the real world. At least for now. Maybe someday we'll figure them out, but for now it's just ideas.
Any theory describes real world to some degree.
> You seem to want to talk about theoretical ideas that have no evidence.
:-/ We can test my ideas in your laboratory, of course.
> You quite misunderstood that article, it's not the vacuum that produces the particles, it is the massive energy they are beaming that produces them.
Do you really read article? Of course, energy is necessary, because two vacuum particles will cannot escape each other and will annihilate. But you cannot produce particle using just energy.
> The stuff in the wikipedia article is just ideas that may work mathematically but have little bearing on the real world. At least for now. Maybe someday we'll figure them out, but for now it's just ideas.
Some far galaxies are traveling from us much faster than speed of light because of space expanding. Thus theory of relativity will work correctly for distances less than 1B of light years, but it is not correct for larger distances. Are you agree?
Yes you can.
And no I don't agree with your last sentence.
Do you know about Big Bang?
And why in the world do you think you can not produce particles using just energy? It happens all the time.
Brian Greene does a pretty good job of explaining all this in the Elegant Universe. If you're into this kind of thing, check it out.
You can only move relative to another object. You may even move fast relative to one object and slow relative to another, meaning your clock ticks at a different rate relative to each of those objects.
There is no absolute clock - you can only compare your clock with someone else's clock.
Look, I'm only a layman, but from what I understand, the speed of light is the absolute clock.
I was refuting the idea of the speed of light as some sort of master clock.
But yes, the actual speed of light always looks like the speed of light.
The 'what' in "So what looks like 90% of the speed of light to you, can look like 10% of the speed of light to someone else." is referring to something travelling slower than the speed of light. A train or bullet perhaps. In different reference frames it can be said that this train/bullet is travelling at different percentages of the speed of light.
That's why it gets weird.
EDIT: To illustrate this, lets say we're sitting on the earth watching an astronaut. Relative to our position, he is travelling at 1/2 the speed of light. Now, some joker decides to shine his laser pointer at the astronaut. From earth we see the laser beam^ blast past the astronaut at .5c (.5c + .5c = 1c, the speed the laser light is traveling).
NOW! from the astronauts perspective! Instead of seeing the laser pass him at .5c, he sees it pass him a nice proper 1c. weird, but it's how the universe works.
^reflecting off spacedust of course :P
But the speed of light can only be measured relative to YOU
That's still wrong, though. The speed of light is an absolute; it's not My Speed + the Speed of Light.
The person I was who originally responded to me (ars) was trying to say that motion in space is impossible because it's always relative -- apparently even to the speed of light. That's not true; motion is relative to the speed of light, period. And what I had been trying to express (however badly) was that the faster you move relative to the speed of light, the slower you move in time.
I think ars was just in a nitpicky mood and was fixating on the particular wording I chose.
You can only move relative to other objects.
No matter how fast you go, if you measure your speed (relative to something else of course) you would measure a speed lower than the speed of light.
Elsewise, from a greater distance you will be able (assuming you have the means) to escape the gravitational pull of the black hole as you would any other object of equivalent mass.
i.e., can you make your time slow down by coming to a full and complete "stop" in space, since I assume nothing in the universe is truly at rest?
No, and that is why in a nutshell why this explanation is actually doing a disservice.
If we take this and your statement further, we could just declare that all analogies are doing a disservice, and all pop science writers should be flogged.
Since gluons are never observed as free particles and we're all familiar with photons, we call it the speed of light.
May be you should consider the fact, that while you are not moving- let's assume that your are in space and way far from earth or any other thing-, your brain, heart and blood do. If they don't, you wouldn't exist. It's in my believe that we are living in a single dimension world, and it's not quite different than a dream; actually it's the same thing. Just think about it ;)