Going faster than the speed of light is possible. It is crossing/achieving the speed of light that is impossible. Objects traveling faster than the speed of light can never slow down to the speed of light.
Additionally, all of the above only applies to the speed of light in a vacuum. In other mediums, objects can travel faster than the speed of light in that medium, e.g. electrons in water can travel faster than light in water (http://en.wikipedia.org/wiki/Cherenkov_radiation for more info).
The giant distances you speak of have little influence on the result, and if anything makes the scenario less probable.
Your question presumes an instantaneous acceleration and subsequent deceleration, of a fairly massive pair of scissors.
It presumes that a giant holder would be strong enough to initially impart such an acceleration, and that the scissors would not break due to the high stresses involved with either change in velocity. Knowing that muscular contractions are fairly inefficient, perhaps 3-5 times the energy applied to the scissors, would be generated as heat.
If we think of the energy required to move such a massive pair of scissors close to light speeds, changing momentum, and overcoming real world air resistance, I imagine that the scissors (and its holder) would not survive the local presence of such a high amount of energy, without having to absorb some of it. They would instantly disintegrate into pure energy.
Your scenario would be more probable if both the people and the scissors were instead infinitesimally small. Even then, it is still unlikely that any matter could break the speed of light, and remain in its initial state.
To the poster just above...agreed. If he is wondering whether the tips of the scissors, due to the large lever arm, could ever travel faster than the speed of light (in vacuum), then absolutely not. This would require the acceleration of matter from below to above the speed of light, which is not possible (requires infinite energy). See my earlier post about the speed of the point where the scissors cross.
As for the post two above this post, true enough, objects traveling faster than the speed of light (in vacuum, of course) couldn't "slow down" to the speed of light (particles known as tachyons). Whether such particles, if they existed, could ever interact with our universe remains an open question.
Mr E-man wrote:
the reality of it wrote:If you close a normal pair of scissors in an instant then it would break the speed of light.
No, it would equal the speed of light. At the speed of light time stands still, meaning that the scissors would go directly from open to closed without anything in between.
So to answer the original question, no, going faster than light is impossible.
That is completely incorrect. Cerenkov radiation goes faster than the speed of light
Lardy wrote:
Mr E-man wrote:No, it would equal the speed of light. At the speed of light time stands still, meaning that the scissors would go directly from open to closed without anything in between.
So to answer the original question, no, going faster than light is impossible.
That is completely incorrect. Cerenkov radiation goes faster than the speed of light
We've already been there. The term "speed of light" traditionally means the speed of light in vacuum: 2.9979x10^8 m/s (and away from strong gravity, for that matter). We all know that light travels significantly slower than this in a medium because of retardation effects associated with interacting with the medium, but that is a separate issue and isn't the point of the post. Incidentally, light can be slowed down to a relative crawl when interacting with a Bose condensate, here's a link to an old article on the topic:
http://www.news.harvard.edu/gazette/1999/02.18/light.htmlLardy wrote:
That is completely incorrect. Cerenkov radiation goes faster than the speed of light
Oh, and by the way, Cerenkov radiation (which is light, after all) travels at the speed of light in whatever medium it is in. It is the charged particles that generate the Cerenkov radiation that are traveling through the medium faster than light travels in that medium. Cerenkov radiation is the light shockwave in the medium. The important point here is that a medium is required.
Perhaps you can simply elaborate. I don't see:- how the point where the scissors cross qualifies as a phase velocity. We speak of a pair of scissors closing -- not electromagnetic waves traveling through a uniform medium, or matter waves in quantum mechanics. What would the equation be for the movement of this crossing point, as a function of the scissor tip velocity?- presuming phase velocity is correct, if having a phase velocity which exceeds the speed of light is what the original poster means by giant people "breaking the speed of light" by closing a giant pair of scissors
lucKY2b wrote:
To the poster just above...agreed. If he is wondering whether the tips of the scissors, due to the large lever arm, could ever travel faster than the speed of light (in vacuum), then absolutely not. This would require the acceleration of matter from below to above the speed of light, which is not possible (requires infinite energy). See my earlier post about the speed of the point where the scissors cross.
As for the post two above this post, true enough, objects traveling faster than the speed of light (in vacuum, of course) couldn't "slow down" to the speed of light (particles known as tachyons). Whether such particles, if they existed, could ever interact with our universe remains an open question.
Mr E-man wrote:
gobbly gook wrote:I was going to leave your comment alone until you became pretentious. By your post, It's obvious you know nothing about relativity other than what you read in some "wow, isn't physics cool" book you found at a used book store.
I made two statements in my original post:
1) If an object were to move at the speed of light, the motion would be invisible. It would appear to go directly from A to B (from the relatively stationary bystander's perspective).
2) It is impossible for matter to reach the speed of light.
I would appreciate it if you could try to contribute by explaining to me why those statements are so wrong. This is a summary of the current argument:
"x=y"
"no it doesn't"
"oh, okay"
Point well taken.
Ahh, as far as point one goes, it was my understanding that traveling at the speed of light (or near the speed of light) slows down time for the traveler, but not the observer - during hypothetical interstellar travel, the people traveling only age a few years, while centuries go by at their home planet.
Furthermore, light certainly doesn't travel instantaneously - there is a measurable time that it takes to get from one place to another.
I also neglected to mention the heat generated by the friction of the scissor blades sliding against each other, and around its axle, would surely exceed the melting and boiling temperature of the scissors, if not completely overcoming molecular and sub-atomic particle bonds.
rekrunner wrote:
The giant distances you speak of have little influence on the result, and if anything makes the scenario less probable.
Your question presumes an instantaneous acceleration and subsequent deceleration, of a fairly massive pair of scissors.
It presumes that a giant holder would be strong enough to initially impart such an acceleration, and that the scissors would not break due to the high stresses involved with either change in velocity. Knowing that muscular contractions are fairly inefficient, perhaps 3-5 times the energy applied to the scissors, would be generated as heat.
If we think of the energy required to move such a massive pair of scissors close to light speeds, changing momentum, and overcoming real world air resistance, I imagine that the scissors (and its holder) would not survive the local presence of such a high amount of energy, without having to absorb some of it. They would instantly disintegrate into pure energy.
Your scenario would be more probable if both the people and the scissors were instead infinitesimally small. Even then, it is still unlikely that any matter could break the speed of light, and remain in its initial state.
I'm still trying to imagine aspects of this problem.
Presuming the scissors don't instantly melt of explode into pure, massless energy before reaching warp speeds, what happens when the scissors stop? Usually scissors are stopped by the two handles bumping into each other.
Think of a giant particle accelerator used to accelerate small particles in different directions so scientists can watch the collision, and observe new particles coming in and out of existence for a scant few instants in time.
Now imagine the mass behind the handles of a 1000 mile long pair of scissors, colliding into each other at near light speed, at light speed, or god forbid, above light speed. I bet we have something much more spectacular than barely observable newly formed particles popping in and out of existence.
It's stuff like this that keeps me coming back to these board. I actually learn a thing or two...
Mr FAT CAT. wrote:
Really relative to the universe we are the ones who are moving at the speed of light, not light.
so would a fair question be can we slow down an object slower than the speed of light, given we are traveling at the speed of light along with every object on earth?
The individual blades can't move faster than the speed of light, but they can approach each other faster than the speed of light. Say they were both moving at 0.75c--then the distance between them would close at 1.5c.
Einstein showed us that adding velocities doesn't quite work like that, because time is not universally constant. At low speeds, we presume time is constant, and velocities are additive, because the error is negligible, and the math is much simpler. However at near-light speeds, the relative position and motion of the observer becomes significant. For example, a stationary observer in the middle would measure different velocities (would he measure a closing speed of 1.5c? I honestly don't know.), than an observer fixed to one of the scissor tips, who surely would not measure the closing at greater than c.
Ticktock wrote:
The individual blades can't move faster than the speed of light, but they can approach each other faster than the speed of light. Say they were both moving at 0.75c--then the distance between them would close at 1.5c.
For more discussion on the scissor question, here is a good link. It addresses both a) why the scissors won't react faster than the speed of light, and, in the caveat, b) why the point of contact between then blades can exceed the speed of light (albeit we should recognize that it is probably a slightly different scenario than what the OP had intended.)
http://www.phys.ncku.edu.tw/mirrors/physicsfaq/Relativity/SR/scissors.html
There's a lot of fun stuff in the parent directory. Enjoy!
Aaah! The scissors cannot be perfectly rigid -- good point.
Special Relativity learn it.
The reason we appear to remain stagnant as the universe expands around us is because we have mass.
Think of it like this, inorder to give energy to mass you must induce an acceleration, on a large enough scale we call this gravity. Mass distorts the fabric of space, and thus creates an uneven expansion, this could be viewed like a contour line which around mass produces a steeper pitch which is similar to the effect of mass on space. The larger the mass, the steeper the pitch and thus the stronger the attraction, or acceleration.