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Post by drfisher on Oct 11, 2004 9:33:08 GMT -5
EricDraven you are confusing speed with acceleration. G Force is caused by acceleration not speed.
It is impossible to travel at light speed. This is because E=MCsquared. Where E=Energy required, M=Mass and C=the speed of light.
If we plot speed vs mass and energy on a chart, we will see that we require infinite energy to travel at the speed of light and this would create infinite mass. As we travel faster, we get heavier.
This goes some way to explain how we can manipulate time. Various factors affect time and time is not definite it can be (and has been) bent.
For example an atomic clock away from the gravitational pull of the earth lost time compared to an identical atomic clock. This was a genuine experiment.
By travelling at the speed of light physisits theorise that the mass will cause time to slow down for the occupant enabling him/her to travel into the future (as time has passed more slowly for him/her relative to earth.)
There is however no way to get back unless you subscribe to wormhole theory.
The only evidence to support wormholes so far is black hole theory in that a black hole is the edge of space in which nothing exists. A wormhole would be like a black hole with an exit.
The Donnie Darko film bypasses a lot of theory (as films are supposed to do) by telling us that wormholes exist and as this is a film, we the viewers are to assume that this is in fact real (in the film.)
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Post by ProvidencePortal on Oct 11, 2004 12:13:08 GMT -5
That's a good summary of what already was capably summarized by other posters in this thread -- thanks drfisher.
And I think from a film structure-POV, yours is a worthwhile point about the assumptions Darko makes for the audience. I believe -- and have read others that say so, and they said it first -- that the movie is successful as a narrative in large part because it doesn't require us to delve into the whys of parallel universes or time travel. Instead, it sets the stage with key assumptions that allow the audience to dispense with scientific stumblers; they can instead launch pretty directly into the storyline.
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Post by Madridarko on Oct 14, 2004 23:11:18 GMT -5
I can say that I admire the way that you were able to word your ideas, for I find it hard. I see that many people tried to somehow post near or somewhat near ideas to yours, but were not able to describe it overall as well as you did. You should maybe try and iterprate their ideas to see if you could make it clearer for others to understand them. That is if you want to of coarse.
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Post by lalalalasparco on Oct 16, 2004 17:09:10 GMT -5
some theries say that if you were travleing light speed time would stop.. or be non exsistance...
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Post by drfisher on Oct 19, 2004 16:08:47 GMT -5
If anyone would like me to explain anything then please ask and I will do so. I do this at University for my classmates when they cannot understand something.
My background for those that are interested. Degree in Pharmacology and currently studying a Nursing degree. I study physics for fun. (I know I'm a nerd)
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Post by Madridarko on Oct 22, 2004 20:02:20 GMT -5
Sometimes, I feel like if I am just so young and I feel like the baby of this site. Everyone else is like 20-40some, I am 14! but I still enjoy this website much, and all I really have to do is place the age belittlement factor to the side as if not in existance. I rember when taking some physics class I was having the hardest of all times to cope with the actuall theory that times is not a property of space and instead it is a property of matter itself. Also that the closer you are to the speed of light, time will slow down as part of property of the matter. I don't know at what time is it that I finally understood it, but it just hit me like if the answere was always infront of me. I mean I understood the experiment with the atomic clocks and how they were some millionth of a second off from each other, but couldn't understand why.
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Post by josh on Oct 22, 2004 22:59:44 GMT -5
In many instances the "knowing" the right answer is different than the "understanding" of the right answer. Having learned several languages it is often the fact that something "sounds" right vs something is right. If you are able to appreciate the subtle nuances of a movie like Donnie Darko and the complexities of time travel, you should have a good future.
See Carl Sagan's version of time travel as a good explaination of time/speed relationships.
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Post by Bigboy on Oct 23, 2004 8:44:50 GMT -5
While you are right that EricDraven mixed up acceleration with velocity, there are also some fundamental mistakes in your post also; While you are correct that force and acceleration are linked - force causes acceleration, not the other way around (Newtons first law). Not so - the equation E=Mc 2 does not lead to this conclustion. You can graph this equation, but c is the speed of light in a vacuum - which is constant at 3x10 8m/s. Plotting speed against mass and energy here is meaningless, because the equation describes the relationship between mass and energy (so you could calculate the energy released by a match, by comparing the mass of the match before you burn it to the mass of the resulting ashes, by applying the difference in mass to the equation). E=Mc 2 does not describe a relationship between velocity and mass. The first thing to get your head round is that space-time is four dimensional - time is absolutely equivalent to the 3 physical dimensions we are familliar with as far as relativity is concerned. Ok - now for the rubber sheet analogy Imagine space-time as a rubber sheet, and a mass (like a planet) is a bowling ball on that sheet. It is clear that the bowling ball 'warps' the sheet - that mass warps space-time. You were correct about the clock experiment - time is experiences at a slower subjective rate inside a gravity well - the deeper the well (the more space-time is warped or curved) the slower subjective time gets (relative to outside the gravity well). At a singularity (a point of space-time that is warped to an infinite degree [I'm not sure if the term 'infinite' here is entirely correct but it's as good as any]) time essentially stops (from the point of view outside the black hole). There are four solutions to relativity that result in a singularity: -The singularity at the big bang -The big crunch. -A black hole - a point of finite (but large) mass in an infinitely small volume. This results in an infinite density (for this explenation this can be considered equivalent to an infinite mass in a non zero volume) and thus warps space time to an infinite extent - a singularity. nb The big crunch is probably equivalent to a super-duper massive black hole. The fourth solution invloves a non zero mass travelling at the speed of light - the reason for this is that a mass travelling at speed warps space-time more than a stationary mass. This extra warp effectively increases the mass of the moving object. As the object approaches the speed of light it warps space to such an extent that if the speed of light was attained the mass of the object would indeed effectively become infinite and a singularity would result. However you are correct that because the effective mass of the object increases to an infinite number as it approaches the speed of light, it is impossible to get there because there is not enough energy in the universe to accelerate such a large mass. If you were to graph the speed of an object against the relative 'rate' of time experienced by the moving object (compared to that experienced at a stationary point in space), then at the speed of light the curve would hit zero. The idea that at faster than light travel you go backwards in time comes from the supposition that by continuing the curve past light speed, it results in a negative number for the 'relative rate of time' .
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Post by Madridarko on Oct 23, 2004 19:34:27 GMT -5
Bigboy, but when you are in a ship of a sort or car or train, whatever median of transportation, when there is an acceleration there will be a force that will push you back because of that acceleration. aka inertia, (Newtons first law, sometimes refferred to law of inertia). Your body wants to resist the change in motion or speed. So you can say that the force of inertia is itself a direct product of the acceleration, and also a direct product of the force that causes the accelaration. Of coarse inertia doesn't neccesaraly happen when there is a change of speed, it can be a change in direction. Like the Centripital/Centrafugal force that an object in a circular motion/path is under.
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Post by Bigboy on Oct 24, 2004 8:53:21 GMT -5
I think the point here is that a body MUST experience a net force to be accelerated. In your example of a train, you are accelerated because of a reaction force applied to you by the train seat. The force is applied because you and the train are moving at different velocities - the fact that the train is accelerating at the time is irrelevent.
Also your use of the word inertia is incorrect: Inertia is the propensity of a body in motion to travel at a constant velocity until a force is applied to it. (Basically a colloquial word referring to Newtons 1st Law as you say). But by this definition inertia is a property of a body not an action on it (so inertia cannot 'happen' it just is), and is not another term for acceleration.
It would probably be a good idea to define acceleration too - it is a continuous graduated change in velocity - not speed as is sometimes stated. Velocity is a vector and has direction and magnitute. Speed is the magnitude of velocity.
So you are correct that an accelerating body can be changing direction without changing speed, because by definition it's velocity is changing.
A force that changes the direction of motion of an object is referred to as a centripetal force (cetrafugal force is another overused and misused term - there is no such thing as centrifugal force. This is related to the other misinterpretaion that bodied actively resist changes in velocity, and is usually down to personal experience - like on a rollercoaster or other fairground rides, it feels like you are pushing into the seat, when in fact it is the seat that is pushing you.)
I realise that a lot of this post is repeating what you said (or at least what you intended to express), but these terms and ideas have specific difinitions and I felt that needed to be clarified.
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Post by Madridarko on Oct 24, 2004 15:51:17 GMT -5
Thank you for clarifying two points in my posting that I was not causios enought to avoid. The first about inertia not happening, but just being, for it is a property of mass not an actual thing that happens. In the Centripital/Centrifugal mistake, I remeber something about one of them being commonly missused, but I could not specifically remember which one, so I decided to writte both of them down at the moment.
I think either did not read well or understood your comment of the train accelaration irrelevent, but that force that the seat applies to you happens when there is a change in velocity, accelaration, and not if the train is going at a constant velocity. Because you are in touch somehow at all times with the train, by means of feet to the ground or back to the seat, once the train is moving, you will be both at the same velocity. Unless the trains accelerates.
I know I am wrong in my previosly posted definition of acceleration, but what I really meant to say is that because Velocity is speed + direction, making it a vector, is that if there is a change in speed or direction or both, there will be a change in velocity, making a change in acceleration.
In Regards to your comment of
like on a rollercoaster or other fairground rides, it feels like you are pushing into the seat, when in fact it is the seat that is pushing you.
It is of my knowledge that this phenomena is what is commenly refferred to as an increase in G-force. Which I belive was debated over in the begenning of this thread.
So what you are saiying is that bodies do not resist change in velocity, but only direction? Please explain what this comment of yours meant to say, for I did not clearly recieve your interpretation of this.
This is related to the other misinterpretaion that bodied actively resist changes in velocity.
Overall, I belive that it is what I was refferring to, but as I mentioned before, I seem to lack that elequency in expressing my ideas and I oftenly read back my own comments to wonder what exctactly was it that I was thinking of or trieng to explain.
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Post by Bigboy on Oct 24, 2004 18:53:38 GMT -5
I know what you mean about reading back your posts - I think my train explanation was pretty poor! I understand what you are saying about the force being transferred through the train (I actually think we are making similar arguments from different standpoints), but there would be no acceleration at all without an originating driving force. G is acceleration due to gravity at sea level (approximately 9.8m/s 2) G-Force is a subjective term that refers to the force experienced by a body when it is accelerated (this acceleration expressed in multiples of G). So if you are on a rollercoaster and you go around a corner and you experience a 'G-Force' of 2G, you experience a sensation of being pushed into the seat as if gravity had doubled (Hence G-Force as in 'gravity' force). However what is actually happening is that the seat is applying a force to you sufficient to accelerate you at 2G (19.6m/s 2) G-Force another expression of the (fictional) centrafugal force. The term G-Force is often used because the physiological affects on a soft body (like a human) and subjective experience are the same whether the seat is applying a force to you, or you are applying a force to the seat. With this description you could say that the experience of G-Force is due to the acceleration you are undergoing - in which case the description in the original post is kind of right. I think we are just defining Newtons first law in different ways here. My comment that was trying to say that on a rollercoaster it only feels like you are resisting acceleration because you are being squished into your seat! But thinking about it, I suppose you could argue that the Mass of a body as its propensity to resist acceleration. Overall MD, I think we have a similar understanding of these ideas, but we express them in slightly different ways.
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Post by gretchen on Oct 25, 2004 16:30:49 GMT -5
*sigh* you guys are just too smart for me
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Post by Madridarko on Oct 25, 2004 19:05:04 GMT -5
Gretchen, how did you get in! Anyways, I guess you are right in saying that we are trieng to prove the same thing from different points of view. So it wouldn't really make sense to keep on arguing and correcting each other. The weired thing is that drfisher gave up on the topic a long time ago.
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Post by Bigboy on Oct 26, 2004 10:05:06 GMT -5
Agreed! ;D
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