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The Hangout

Calvin19 Jul 17, 2007, 6:09 PM

This is keeping me up nights...

So, my girlfriend is an astronomer, a real one. it doesnt suck cause she is up late looking up, and i am up all night climbing up then looking down, right?

anyway... I had this question for her... she knows all this light theory, relativity stuff, that i kinda understand, but i dont really.

It seems that i am not as smart as i thought i was, and its freaking me out.

SOOOO>>>>>

I grasp the theory of relativity from a time standpoint, but i cannot quite see how it relates to energy and mass. is it the same thing all of the sudden?

i had an argument, related to deep space travel. it cam about from talking about moonshot speeds, orbit trajectories, etc, but thats besides the point.

I was told, by her, that the reason faster than or = to light speed travel is impossible, is that it would require infinate energy to accelerate to that speed.

since something like that had never been tested (at least in a aplicable sort of way) then there is no way to prove it, therefor it could be possible. I was told that it is ignorant to think that.

so... what am i missing?

my reply to her...

1- 80 years ago faster than sound travel was thought to be impossible.

2- assuming that math is the only proof einstein has for this, then theoreticaly,
-it would take less energy to accelerate from ZERO to 100,000km/sec, than it would take to accelerate from 100,000km/sec to 200,000km/sec.

this i dont understand. and she could not answer that.

i guess, im asking for a bridge between relativity and macro acceleration, not speed.

my brain hurts.

sorry i rambled there for awhile. I know there has to be smart BASE hopers out there somewhere.

i just dont like the idea of believeing in something i dont understand.

im personaly still kinda skeptical that a ship can't travel at 300,001km/sec. we just need enough fuel, right?

"what do ya know? Gallileo was right after all"

stitch Jul 17, 2007, 6:39 PM

Re: [Calvin19] This is keeping me up nights...

You could pose the question to the good Doctor 460. Although his answer would probably give your already fragile brain matter an embulism. Pirate

Pirate

Tongue

Calvin19 Jul 17, 2007, 6:59 PM

Re: [stitch] This is keeping me up nights...

I like 460. i wonder if i have ever met him.

Jingleballs Jul 18, 2007, 12:20 AM

Re: [Calvin19] This is keeping me up nights...

Calvin19 wrote:

I grasp the theory of relativity from a time standpoint, but i cannot quite see how it relates to energy and mass.

so... what am i missing?

Get yourself down to your local library and look for a classic book (actually, a three-volume set) called "The Feynman Lectures on Physics". It will be a bit more work to read than a popular science text, which will just be a lot of arm waving with no equations, but it will give it to you straight without covering anything up.

You want to get to the section titled "A Really Sexy Equation", in which Feynman derives the famous Einstein equation, E=mc^2. This comes out of thought experiments relating to observers in relative frames of reference, exactly the same way time dilation does.

I'm sure you could find much of the same stuff explained on Wikipedia and elsewhere, too. But if you really want to understand, and are willing to do a few hours of work, the Feynman book is hard to beat.

stitch Jul 18, 2007, 12:40 AM

Re: [Calvin19] This is keeping me up nights...

Calvin19 wrote:

I like 460. i wonder if i have ever met him.

He holds a Phd. in physics which most will agree makes him an authority on the subject. He also seems to have a way of conveying information, without the "message" going over most peoples heads. That's just an observation though.

inzite Jul 18, 2007, 1:06 AM

Re: [Calvin19] This is keeping me up nights...

Calvin19 wrote:

-it would take less energy to accelerate from ZERO to 100,000km/sec, than it would take to accelerate from 100,000km/sec to 200,000km/sec.

this i dont understand. and she could not answer that.

The issue here, if I remember correctly (it's been a long time), is that as a particle's speed increases, so does its mass.

Imagine a proton. At rest it has a mass of 1.67262158e-27 kg. Imagine we accelerate it to 0.1 C (one-tenth the speed of light). This requires a set amount of energy. At 0.1 C the proton's mass has increased by a factor of 1.005 and now has a mass of 1.6809846879e-27 kg. So it will now take MORE energy to accelerate it another 0.1 C.

The real kicker here is that the particle's mass DOES NOT INCREASE LINEARLY. At 0.5 C the particle's mass will have increased by a factor of 1.1547, and at 0.9 C the particle's mass will have increased by a factor of 2.2942. This mass will continue to increase towards infinity as the particle's speed approaches infinity.

As such, it would take an infinite amount of energy to accelerate even a single proton to light speed. We can get damned close to light speed (some studies have measured cosmic rays emitted by galaxy collisions at above 0.999 C), but we'll never quite get there.

Of course, the relativistic factor at low speeds is so small it can usually be ignored. For example, even at 100,000 km/hr, mass increases by a factor of only 1.0000000042926314. Which is why for most day-to-day calculations, Newton's laws can be used as a damned-close approximation of what's really happening. And that's why at low speeds, the energy required to go from 50 km/hr to 100 km/hr is ALMOST exactly the same as the energy needed to go from 0 km/hr to 50 km/hr. However, at near light speed, this factor becomes VERY important.

Calvin19 Jul 18, 2007, 5:54 AM

Re: [inzite] This is keeping me up nights...

Yesterday i was given a astronomical physics book by my GF, she told me it would explain it.

I actualy got that exact explanation. thank you...

ok... i understand it now, for the most part at least.

I read about super-luminal jets, event horizon, etc. it is interesting stuff...

but where is this light speed limit relative to? earth is hauling ass around the sun, and our solar system is hauling ass around the millky way, is the speed we can reach relative to earth toward one star faster than the speed we can reach toward another?

UPS Jul 18, 2007, 7:00 AM

Re: [inzite] This is keeping me up nights...

inzite wrote:

As such, it would take an infinite amount of energy to accelerate even a single proton to light speed. We can get damned close to light speed (some studies have measured cosmic rays emitted by galaxy collisions at above 0.999 C), but we'll never quite get there.

We'll get there, we only need to wait until all the petrol lobeyist have died. From that point, if we're still alive after the global warming, it should be a good 500-1000 years before we reach that peak point of technologie where this could be possible, or even closer if some sort of alien comes to earth Smile

Smile

.

But don't worry about this Calvin, you have to remember that you and I won't be alive to see it Wink

Wink

avenfoto Jul 18, 2007, 8:05 AM

Re: [Calvin19] This is keeping me up nights...

all this, yet you cant understand that a pregnant girl, was never innocent, because at some point she agreed to take the d without contraception.

GreenMachine Jul 18, 2007, 10:01 AM

Re: [avenfoto] This is keeping me up nights...

(...to be read in Samuel L's voice from Pulp)

So by that rational a girl who takes the D
WITH contraception would still innocent? Tongue

Tongue

460 Jul 18, 2007, 10:51 AM

Re: [Calvin19] This is keeping me up nights...

Light speed is constant relative to anything that's not light-like. this was first noticed in the equations of electrodynamics which govern all forms of light, from x-rays, visible light, to radio waves.

Now let's say you've (I'll refer to you as driver) accelerated to 99.99% of the speed of light in your hot new Ferrari and then you turn on your headlights. You may ask "how fast is the light departing from me?" It actually departs from you at the speed of light from your point of view. the kicker to relativity is that there is no preferred frame. So the dude you just stole the Ferrari from (referred to as sucker) is watching you carefully as you speed away from the scene at 99.99% of the speed of light. So "sucker" notices that "driver" turns on the headlights and through some technique sucker is able to observe the speed of the light emitted by driver's headlights. In his frame, the light sucker observes from driver's headlights goes at the speed of light such that in sucker's frame of reference, the light only slowly departs from the driver. But in driver's frame, the light departs from the driver at the speed of light. Now speed is distance traveled per unit time. The only way to ensure the constant speed of light in all these different frames of reference is to alter distances and alter time. In other words, space-time has been altered and it's speed dependent. It's a mindblowing and mindnumbing concept. To alter space and time (after some math and one key sacrosanct physics law) implicates matter and energy to form E=m*c^2.

From Lise Meitner, Atomic Pioneer by Deborah Crawford:

"The Lise sat in the audience and Einstein took the podium. He began speaking of new and startling concepts, but his ideas were delivered in such a diffident manner that Lise though, it must be that he was simply sharing with the audience his views of the nature of motion, but that nothing could possible be done to prove them; he was, she felt, the epitome of the pure scientist, the man whose research is done only in the spirit of inquiry, without any practicalapplication in mind... Herr Einstein looked out over his audience with a somehow say, faraway gaze; and spoke of the utterly new idea that all motion in the universe was relative EXCEPT the speed of light, which was 186,272 miles per second Sensing a stir of double and dissatisfaction from the assemblage - which must have consisted of nine-tenths of the best scientific brains in the world at the time - he case around for example to illustrate his theory. Had not each of us at one time or another been on a train that was sitting in the station while another train went by, and had trouble believing that we were not actually in motino? Or if we were on the moving train, what would be our 'true' speed if we were walking backward through the cars at a certain number of miles per hour, whie the train was rushing forward at another rate; the earth was turning on its axis at a third rate, and going around the sun at yet a fourth! The answer had to be a relative one....

Grudging laughter throughout the hall. Einstein turned to the blackboard and picked up a piece of chalk. His heavy, dark brown hair like an unruly bush up his head, he said, 'One should thing of matter as condensed energy. The faster matter travels the shorter it becomes. If we could get a piece of matter to travel so fast that a part of it would disappear, the resulting amount of energy would be nothing short of fantastic.' He looked at them with his absent-minded, couldn't- matter-less expression. 'Since the velocity of light is a huge quantity, a small amount of mass - multiplied by the square of the velocity - is equivalent to a very large amount of energy. Thus, if m stands for matter, E for energy, and the speed of light c-' There was not a sound in the great hall except the squeak of chalk as Einstein scrawled on the blackboard, for thie first time, the equation, ' E=mc^2.' The he said, 'Thank you, gentlemen ... Ladies ..." with a little bow in Lise's direction, and made his way off the platform. The applause was patchy and full of murmuring voices."

wwarped Jul 18, 2007, 3:03 PM

Re: [Calvin19] This is keeping me up nights...

Calvin19 wrote:

1- 80 years ago faster than sound travel was thought to be impossible.

they were right then, and they are right now! it can't be done.
you should realize the air molecules can't get out of the way. geeeshhh.

and yes, I am serious.

any James T. Kirk fan will recognize the name (spelling aside) of "Kobiashi Maru." it was a no-win scenario. James could not handle that, so he changed the rules.

you live in CO, right? ever watch a snowplow? that is what an aircraft does. as the molecules pile up, they heat up. this literally changes their chemical composition. behind this "shock wave," the aircraft is flying SLOWER than the speed of sound. (it's as if after collecting 2 foot of snow in front of the plow, the snow starts melting. this melting would let the former snow skirt AROUND the plow.)

maybe to achieve faster than light travel, we need a different model... change the rules.

maybe it's NOT possible.

Calvin19 Jul 18, 2007, 5:36 PM

Re: [wwarped] This is keeping me up nights...

totaly agreed... but nothing is in the way out there besides that bastard einstein Tongue

Tongue

nicknitro71 Jul 19, 2007, 7:43 AM

Re: [Calvin19] This is keeping me up nights...

Matt,

The key is not to try to go at the speed of light or ever near it, even a single proton will have a hell of a hard time going near those speeds.

There are ways around it…read up on wormholes…and on super string theory that in a nutshell suggests that wormholes are rips of the fabric of the universe that happens constantly. Read Brian Greene’s The Elegant Universe, there is no math and it’s meant as a best seller not a text book, but it’s well written and Brian is a very passionate guy. I am not saying the string theory is correct or it will be the theory of everything but nonetheless it suggests some cool stuff.

STR and GR are easy to understand with a little effort because they deal with a classical universe and our thoughts are classical as well. They also started as classical thoughts not as discrepancies on unexplainable empirical results.

If you think GR and STR are mind-blowing wait until you get your hands dirty with Quantum Mechanics…that’s a totally different ballgame! Truth to be told none will ever understand the metaphysics of QM because we cannot use our thoughts in any other way than classical. Even Einstein himself fell short on QM…determinism just does not apply to QM and all the classical physics makes non-sense predictions about QM phenomena. Einstein truly did not believe in the various non-classical interpretation of QM (read up on his conversation with Bohr). In the famous EPR paradox (another must read) he showed that according to QM “certain aspects” of a “certain reality” seem to happen immediately breaking the gospel of the universal speed limit. However Bell’s inequalities have been shown to happen both theoretically and empirically (read up on those as the math is very easy).

We have kind of gained control of three of the four forces, we use electromagnetism constantly, the week nuclear force in many branches of science and medicine, and the strong nuclear force to convert energy and destroy things here and there. We still have very little clues about quantum gravity, how to convert it from other forces, how to unify it with the other three, and how to use it in the form of anti-gravity.

And that is the last frontier of physics: The full understanding of gravity and what it’s made of. Once we reach that milestone using it to rip the fabric of the universe, to collapse the universe, to fuck things up so we can be on the other side of the universe in a heart beat will be just a matter of time.

So Matt, there are ways around it, the problem is they are not that easy for humans to grasp, even the very “gifted” ones again because we are classical animals.

460 Jul 19, 2007, 8:33 AM

Re: [nicknitro71] This is keeping me up nights...

quantum mechanics simplifies the problems significantly by reducing the number of potential solutions to the equations of motion.

hard to intuit but mathematically simpler.

d123 Jul 19, 2007, 6:30 PM

Re: [Calvin19] This is keeping me up nights...

Accidentally a few days ago, while baking my mindwarp, I found a this:

a good visual explanation of the 10th dimension theory

I've really enjoyed the coincidence a lot... BIG TIME !

nicknitro71 Jul 20, 2007, 6:31 AM

Re: [d123] This is keeping me up nights...

When dealing only with massless forces, superstring suggests 26 spacetime dimensions!

More than 10 dimensions are needed to encompass the fabric of the universe/s.

Read up Flatland by Edwin Abbott Abbott, absolutely brilliant.

460 Jul 20, 2007, 7:29 AM

Re: [nicknitro71] This is keeping me up nights...

i have flatland on my desk here at work.

Calvin19 Jul 20, 2007, 6:56 PM

Re: [nicknitro71] This is keeping me up nights...

hokay... so i think i semi-grasp the idea of exponential increase in mass as a function of C, but i have another weird question for you guys...

so, Earth is hauling ass around the sun, and the sun is really hauling ass around the milky way, as i understand relativity, there is a problem with that.

for the same reason NASA and other people launch to the east, if we launched a Spacecraft WITH the orbit direction of earth, would that few km/sec count for the relativity? or is that purly a point of reference, say we have two reference points moving at different speeds, can we travel fater than light compared to one of them? of course we can... so is the max relative speed of the 'everything' 1.99999_ C? or is it faster due to the relativity thing? if a trolly car (credit a book I read Angelic

Angelic

) leaves the milky way at .999C, and there is another galaxy on a colision course with the milky way with a closing speed of .5C, and those weird aliens launched a trolly car at our spaceship at .9999_C from their refrerence point, they would be 2.49999_C~ right?

did i miss something. ??

my brain hurts again.

nicknitro71 Jul 20, 2007, 7:52 PM

Re: [Calvin19] This is keeping me up nights...

You are missing a couple of things Wink

Wink

don't we all?

Fist relativity is taken into consideration even for orbiting satellites for instance...the clock in an orbiting satellite ticks faster than a one on earth because of weaker gravity however because of its orbiting speed a satellite also clock ticks slower than a one on earth...overall it ticks faster...so for some every day applications SR and GR are needed.

As for your second question you must consider spacetime as a whole not as independent dimensions...that's where your problems are coming from.

If you only have 100 bucks you can spend it all in time or all in space or a fraction in time and the rest in space. You cannot spend 100 bucks in space and 100 bucks in time. Light spends 99% of its money in space, we slow humans spend 99% of our money in time.

Calvin19 Jul 20, 2007, 7:58 PM

Re: [nicknitro71] This is keeping me up nights...

I definatly did not grasp that metaphor...

hmm...

ok... so, Space is curved by gravity, i dont think i have grasped how that effects relativity in travel. I assume because light is also effected by gravity, that is the kicker.

blah. again.

this is why im a pilot. i just control shit on earth.

nicknitro71 Jul 20, 2007, 8:04 PM

Re: [Calvin19] This is keeping me up nights...

In reply to:

Space is curved by gravity, i dont think i have grasped how that effects relativity in travel

and that's the problem...it's not space that's curved...it's SPACETIME

And yes even light curves around the weakest of the forces...

virgin-burner Jul 21, 2007, 3:14 AM

Re: [Calvin19] This is keeping me up nights...

Calvin19 wrote:

I definatly did not grasp that metaphor...

hmm...

ok... so, Space is curved by gravity, i dont think i have grasped how that effects relativity in travel. I assume because light is also effected by gravity, that is the kicker.

blah. again.

this is why im a pilot. i just control shit on earth.

if you'd understand that, i probably wouldnt want to fly with you.. no pun intended, maybe you lack just a little of imagination, as these concepts need a little out off the box thinking..

mfnren Jul 22, 2007, 12:17 AM

Re: [virgin-burner] This is keeping me up nights...

so as an aside, I just saw a gravity map of the earth the other day. some of you have probably seen this but.. gravity is not constant over the surface of the earth, areas like the rockies, especially colorado and the himalayas have stronger gravity than say florida.

stitch Jul 22, 2007, 6:47 AM

Re: [nicknitro71] This is keeping me up nights...

nicknitro71 wrote:

In reply to:

Space is curved by gravity, i dont think i have grasped how that effects relativity in travel

and that's the problem...it's not space that's curved...it's SPACETIME

And yes even light curves around the weakest of the forces...

That's DEEP.

nicknitro71 Jul 22, 2007, 7:29 AM

Re: [mfnren] This is keeping me up nights...

In reply to:

especially colorado and the himalayas have ~~stronger~~ WEAKER gravity than say florida.

Wink

NSEMN8R Jul 23, 2007, 9:22 AM

Re: [nicknitro71] This is keeping me up nights...

Fuckin Nerds.

460 Jul 23, 2007, 9:28 AM

Re: [Calvin19] This is keeping me up nights...

ignore gravity via general relativity. it's outside the scope of the original question. the concept of bending space time doesn't really provide any intuition to the lay person.

ignore string theory too. it's the only game in town in high energy physics but it's just a hypothesis right now. the math is too difficult to obtain significant physical insite. grand unified theories are outside of the general scope of the issue.

light speed is constant in whatever frame that it's observed in. that constancy drives unusual consequences such as time dilation, length contraction, increased mass with increased speed, and the relation between energy and mass.

460 Jul 23, 2007, 9:30 AM

Re: [NSEMN8R] This is keeping me up nights...

the biggest nerd of all, A. Einstein, got more ass than a toilet seat. No kidding.

NSEMN8R Jul 23, 2007, 12:26 PM

Re: [460] This is keeping me up nights...

I've heard that before.

I'm just jealous because you guys are smarter than me.

UPS Jul 23, 2007, 12:37 PM

Re: [460] This is keeping me up nights...

A thing that I wanted to be sure of. When someone says planet ''x'' is 20 light years from planet ''y'', is it true that if you had a strong enough telescope to see the ground on planet ''Y'' from planet ''X'', you would not see the present, but things that happened 20 years ago on that planet ?

460 Jul 23, 2007, 12:48 PM

Re: [UPS] This is keeping me up nights...

that's exactly the meaning. 20 light years means you are seeing what happened 20 years ago.

460 Jul 23, 2007, 1:03 PM

Re: [NSEMN8R] This is keeping me up nights...

smarter - not necessarily. i learned those things simply because i was interested in those subjects.

Calvin19 Jul 23, 2007, 11:04 PM

Re: [460] This is keeping me up nights...

460 wrote:

smarter - not necessarily. i learned those things simply because i was interested in those subjects.

im not smart, but this stuff fascinates me. i cant even spell. dont care to either.

A beautiful Universe is a crazy book.

stitch Jul 24, 2007, 6:22 AM

Re: [Calvin19] This is keeping me up nights...

The urge to flick every tower I see, is keeping me up nights.

azdiver Jul 24, 2007, 9:09 PM

Re: [Calvin19] This is keeping me up nights...

is she saying its imposable for everything to the speed of light or just aircraft, or spacecrafts? particle accelerators can get a particle to the speed of light, this is whats used for creating antimatter.

Calvin19 Jul 24, 2007, 9:31 PM

Re: [azdiver] This is keeping me up nights...

i think that particle acc. cannot get a particle to the speed of light, only
.999_ of it.

mfnren Jul 24, 2007, 11:18 PM

Re: [nicknitro71] This is keeping me up nights...

not according to the map I saw. More density=more gravity. Check it biotches..
http://www.space.com/...9.+Click+to+enlarge.
although it doesn't correspond with surface features in many places.

nicknitro71 Jul 25, 2007, 9:05 AM

Re: [mfnren] This is keeping me up nights...

Ren,

It's a typo. Gravity is inversionally proportional with the altitude. At sea level there is more gravity than on top of Mt. Everest. In a geostationary orbit there is less gravity than on Mt. Everest. In the center of the earth there is more gravity then at sea level. In empty space there is no gravity because spacetime is not curved by any massive objects.

azdiver,

Don't confuse physics with science fiction!

Calvin19 Jul 25, 2007, 10:29 AM

Re: [nicknitro71] This is keeping me up nights...

wait... in the center of the earth there WOULD be more gravity, but it would all cancel out right? so if there would be a space in the center of earth (science fiction Tongue

Tongue

) a person would feel 0 G, right?

because everything has gravity, the spaceship in orbit is being pulled toward the planet by the planet, but the planet is also being pulled toward the spaceship.

my mass x your mass divided by the gravitational constant, etc...

azdiver Jul 25, 2007, 6:09 PM

Re: [Calvin19] This is keeping me up nights...

>wait... in the center of the earth there WOULD be more gravity, but it would all cancel out right? so if there would be a space in the center of earth (science fictionTongue) a person would feel 0 G, right?

>because everything has gravity, the spaceship in orbit is being pulled toward the planet by the planet, but the planet is also being pulled toward the spaceship.

>my mass x your mass divided by the gravitational constant, etc...

i think your theory is kind of that of a blackhole, center has the largest amount of gravity, so in theory you would be pullverized down to the smallest piont, thats if you could get there without it pulling you into a trillion pieces first. just my thoughts though

mfnren Jul 25, 2007, 7:19 PM

Re: [nicknitro71] This is keeping me up nights...

Assuming that gravity is pulling equally across the surface of the earth...
Higher density areas below the surface of the earth create stonger gravity, if that area happens to be under a mountain range, gravity could be stonger on top of a mountain than an area with weaker gravity at sea level.

Calvin19 Jul 25, 2007, 7:56 PM

Re: [azdiver] This is keeping me up nights...

i just checked myself with some CU professor, i was 'correct'

in theory, if there WAS a sphere in the exact gravitational center of earth, and an object could be inside that sphere, in the center of it, it would have equal gravitational forces in infinate directions, meaning it would 'apear' to be at 0 gravity.

science fiction stuff.

Calvin19 Aug 26, 2007, 9:03 PM

Re: [Calvin19] This is keeping me up nights...

HOKAY...

so, a spaceship is approaching the speed of light, say, at .999 C.

its mass is increasing, as is the mass of its fuel, in egual proportions. therefore, as i understand, the spaceships' engine is also producing more power, my imagination is using a simple inertial displacement rocket motor.

so, the observer on the spaceship is STILL experiencing normal acceleration? but the observer outside is only seeing the spacecraft increase in mass?

Calvin19 Sep 20, 2007, 1:14 AM

Re: [Calvin19] This is keeping me up nights...

but not really producing more power, because as the fuel is pushed backwards, it is loseing speed relative to the observer, therfor also losing mass. so the engine, relative to the observer on the departure point, loses powere as it gains speed.

nevermind.

bodyguard Sep 20, 2007, 6:54 AM

Re: [Calvin19] This is keeping me up nights...

so just to be a smart ass ,i could tell someone on another planet 20 light years away to check out with there telescope ,the exact spot i had sex and they could watch ....hmmm interesting maybe these geeks are getting into something,or i am just sick.

Ghetto Sep 20, 2007, 9:26 AM

Re: [bodyguard] This is keeping me up nights...

if you had sex, and then hopped on a spaceship that traveled twice the speed of light and went to that planet of yours 20 light years away, you could watch yourself having sex. You'd be pretty bored on that planet alone for 10 years, though. just make sure you bring the girl so you can watch yourself again in 20 years after you return to earth Crazy

Crazy

besides... if your mass increases as you approach the speed of light, you could have tubby whale sex for the whole ride! or does that not apply for volume...

Cool

Cool

Cool

Tongue

Blush

Wink

Unimpressed

Unsure

Calvin19 Sep 20, 2007, 9:38 AM

Re: [Ghetto] This is keeping me up nights...

I saw that there were 2 replies and i got all excited for a smart answer.

Smart ass i guess works just fine for now.

crwper Sep 25, 2007, 1:12 PM

Re: [Calvin19] This is keeping me up nights...

I've been thinking about this a bit, so I'll throw my two cents in here.

First, I've been thinking it might be helpful to focus on what's actually postulated by special relativity (SR) rather than the results. SR is an extension of a much older idea, namely, Galilean invariance (GI). GI states that the laws of mechanics are the same in any inertial (non-accelerating) reference frame. Specifically, Galileo postulated that if you were standing inside a ship traveling at constant speed, there is no experiment you could do that would tell you if the ship is moving or not. What Einstein did was to state that the same principle applies to all the laws of physics, and not just the laws of mechanics.

On the surface, this sounds like pretty much the same thing. But there are some interesting consequences. For example, the laws of electrodynamics tell us that the speed of light can be calculated from a few empirical parameters. That means that no matter what your point of view, all the light around you should appear to be going the same speed: c.

This has many consequences, including time dilation: If you are moving relative to another observer, you will always see his clock moving slower than yours. The effect is reciprocal--he sees your clock moving slower, too. One very important thing to remember about SR is that what you see depends very much on where you are seeing it from. That's the 'relativity' part.

To answer your last question, one thing you need to know is that an increase in mass is not an result of SR. The 'increase in mass' idea is almost right, but it's important to understand where it's wrong. You see, SR postulates that 'the laws of physics' are the same in all inertial reference frames. Notice it doesn't say anything about which laws of physics are correct, just that if they are correct, then they have to be correct in all inertial reference frames.

To make the laws of physics work, we need to replace the old-fashioned idea of momentum with a new one: relativistic momentum. You can look at this in a few ways, but for now let's look at it in the way that doesn't involve 4-dimensional vectors. Classical momentum is:

p = m v.

Relativistic momentum is:

p = a m v.

The parameter a (actually gamma, the Lorenz factor) is:

a = 1 / (1 - b^2) where b = v / c.

At very low speeds, this looks a lot like classical momentum. But as your speed, v, gets closer to c, a goes to infinity, and so does relativistic momentum.

What does all this mean for the rocket? Basically, a rocket works by pushing a certain mass of propellant out the back. Whatever momentum is imparted on the propellant, you get back as a reactive force that pushes the rocket forward, balancing the change in momentum of the propellant. The trouble is, with relativistic momentum you will find this contributing less and less to your speed as the Lorenz factor goes to infinity. You will never have enough momentum to exceed the speed of light (relative to any outside observer).

Michael

Ghetto Sep 25, 2007, 3:11 PM

Re: [crwper] This is keeping me up nights...

It would be really interesting, then, to see what effect this would have on any spinning parts that are a part of this spaceship.

The portion that was moving forward (relatively) would have more momentum than the portion that was moving backwards. Wouldn't that mean that a disc (spinning on the proper axis) would have a tendency to naturally speed up as it approached the speed of light?

If it didn't break apart from the forces (which it would as it approached the speed of light), it would make for a far better propulsion method than rockets would at near-light speeds Cool

Cool

Calvin19 Sep 25, 2007, 4:22 PM

Re: [Ghetto] This is keeping me up nights...

Ghetto wrote:

The portion that was moving forward (relatively) would have more momentum than the portion that was moving backwards. Wouldn't that mean that a disc (spinning on the proper axis) would have a tendency to naturally speed up as it approached the speed of light?

hmmm... that really just made me shivver... i have to be wrong, but at first glance in the last 2 posts, ghetto, what you just suggested, when put on a variable-radius flywheel, seems like the workings of what i can only describe as an perpetual-infinate-energy-machine

Calvin19 Sep 25, 2007, 5:12 PM

Re: [Calvin19] This is keeping me up nights...

nope, wont work. but its a funny idea. sigh...

Einstein, quit telling god what to do.

pocbase Sep 25, 2007, 10:41 PM

Re: [Calvin19] This is keeping me up nights...

can somebody please make me a real child like drawing of what you guys are on about.... thanks! Tongue

Tongue

Calvin19 Sep 25, 2007, 11:18 PM

Re: [pocbase] This is keeping me up nights...

pocbase wrote:

can somebody please make me a real child like drawing of what you guys are on about.... thanks! Tongue

Tongue

hahaha... i almost need one as well.

crwper Sep 26, 2007, 8:31 AM

Re: [Ghetto] This is keeping me up nights...

Won't work. For a simple reason why, imagine an observer inside the rocket, who will see a spinning, but otherwise stationary, disc. Relativity tells us that the disc should act normally from this vantage point, in spite of any velocity the rocket might have relative to an outside observer. Since it would be very surprising, indeed, if the disc began to accelerate on its own, this is excluded.

For a more detailed explanation, you'll need to take into account all the effects of relativity. To determine if the disc will accelerate, you need to add up all the forces acting on it. Note that the force required to increase the momentum of the disc is:

F = dp / dt.

Both the change in momentum and the change in time are sensitive to relativistic effects. In relation to classical momentum and time:

dp = a dp' and dt = a dt'

where dp' is the classical change in momentum, dt' is the classical change in time, and a is the Lorenz factor. Then the force becomes:

F = (a dp') / (a dt') = dp' / dt'.

But this is the 'classical' force. so the net force on the spinning disc will be the same regardless of its motion relative to an outside observer. Sadly, the disc will not spin up on its own.

Michael

Ghetto Sep 26, 2007, 9:32 AM

Re: [crwper] This is keeping me up nights...

Error: Undeclared Variable 'dp'

Press Alt+F4 to continue..

Ghetto Sep 26, 2007, 9:39 AM

Re: [crwper] This is keeping me up nights...

You're back! Wink

Wink

yea, i get it now, d is Delta. I'm still not sure where to find the letter 'p' in 'momentum', but what the heck.

So if dt changes proportionately with dp, how would that affect an observers' observation of the spaceship's speed? would it appear to be moving at all? If not, it sounds like achieving light speed would be a really good way to stand still for a long, long, long time...

yuri_base Sep 26, 2007, 9:55 AM

Re: [Ghetto] This is keeping me up nights...

This is keeping me up nights:

If you are lying on a spinning disk with your head at the center and your feet spinning at 0.999c, for your whole life, wouldn't your head be 80 years old while your legs are 3y.o. (with all ages in between)?

Can't stop thinking about this terrible, terrible scenario... lost all my sleep.

Ghetto Sep 26, 2007, 10:27 AM

Re: [yuri_base] This is keeping me up nights...

I was wondering when you were going to show up Wink

Wink

yuri_base Sep 26, 2007, 12:09 PM

Re: [Ghetto] This is keeping me up nights...

Another thing that keeps me up is this:

What it'll be like to BASE jump on the moon?

Someday there will be cities inside huge inflated domes on the moon. Got air - can jump.

Now, with 1/6th of earth's gravity and full atmospheric pressure, will BASE lose its appeal?

You now only need a 40sq.ft. canopy to get the same wingloading as on Earth. The terminal velocity is now 50mph. Gear will be ridiculously small (imagine Trango 40), even harness will be made of much thinner materials as the opening shock at 50mph is much weaker. Getting into buildings will be much easier as you can hide your rig inside your vagina. Wingsuits will fly with ridiculous fallrates in the low teens - just land it in the pool. You can smoke a cigarette while proximity flying in and out of the windows.

But everything will be 6 times slower. You jump and sloooooowly start accelerating. After several seconds of freefall you can still high-five your buddy a couple of stories below. You can do 10 gainers before you pull your giant 200" PC on a 100ft jump.

Will moon BASE be as exciting as Earth BASE? I can't stop thinking about it, and that's keeping up nights.

pocbase Sep 26, 2007, 12:19 PM

Re: [yuri_base] This is keeping me up nights...

It would be funny to watch cops run after BASE jumpers and all of them are bouncing all over the show.

Calvin19 Sep 26, 2007, 12:46 PM

Re: [pocbase] This is keeping me up nights...

of course, in reality the pressure inside one of these domes will not be ~14psi. something like 6 or 7 PSI. much less air density.

and I would assume that the inflatable domes will not be very tall at all. something that you could easily jump from and land on your feet even in earth gravity.

now, BASE on mars, thats a different story. 10,000' cliffs, and much less gravity.

Ether Sep 26, 2007, 3:18 PM

Re: [yuri_base] This is keeping me up nights...

yuri_base wrote:

You can do 10 gainers before you pull your giant 200" PC on a 100ft jump.

It would be pretty silly to have a PC bigger than the canopy. You'd need some other extraction method - perhaps some sort of spring-loaded system, like that used for skydiving reserve PCs. Or if the canopy is small enough, just pull it out from the BOC directly and throw it -- only now the BOC _is_ the container!

yuri_base Oct 3, 2007, 12:27 PM

Re: [Calvin19] This is keeping me up nights...

To get some sleep, I tried to count the number of 6s in this "cliff"... but then lost sleep completely when it turned out to be 666.

6
66
666
6666
66666
666666
6666666
66666666
666666666
6666666666
66666666666
666666666666
6666666666666
66666666666666
666666666666666
6666666666666666
66666666666666666
666666666666666666
6666666666666666666
66666666666666666666
666666666666666666666
6666666666666666666666
66666666666666666666666
666666666666666666666666
6666666666666666666666666
66666666666666666666666666
666666666666666666666666666
6666666666666666666666666666
66666666666666666666666666666
666666666666666666666666666666
6666666666666666666666666666666
66666666666666666666666666666666
666666666666666666666666666666666
6666666666666666666666666666666666
66666666666666666666666666666666666
666666666666666666666666666666666666

Ghetto Oct 4, 2007, 1:37 PM

Re: [yuri_base] This is keeping me up nights...

I'm afraid I'm going to have to raise the bullshit flag on that one. You're a mathematician.. you knew without counting that the summation of 1-36 would equal 666.

The bigger problem is that you wasted all that time building a horribly underhung cliff Laugh

Laugh

edit: On second thought, it does look like a great sledding hill!

Calvin19 Oct 4, 2007, 2:10 PM

Re: [Ghetto] This is keeping me up nights...

SKIBASE!!!

1
11
111
1111
11111
111111
11111111
1111111111
1111111111111
111111111111111111
1111111111111111111
11111111111111111111
111111111111111111111
1111111111111111111111
11111111111111111111111
111111111111111111111111
1111111111111111111111111
11111111111111111111111111
111111111111111111111111111
1111111111111111111111111111
111111111111111111111111111111
11111111111111111111111111111111111
1111111111111111111111111111111111111111
111111111111111111111111111111111111111111111111111
111111111111111111111111111111111111111111111111111111111111111111111

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Re: [Calvin19] This is keeping me up nights...

You have too much free time.

Then again, so do I. Smile

Smile

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Calvin19 Oct 4, 2007, 3:41 PM

Re: [Bolas] This is keeping me up nights...

mine took about 50 seconds. you had to write up a code man.

i should be doing school...

bye.

tdog Oct 4, 2007, 4:52 PM

Re: [Bolas] This is keeping me up nights...

I decided to waste some time, copy your text into word, color it, and post it on my skydiving/base photo wall...

Here is the revised version.

Bolas Oct 4, 2007, 5:37 PM

Re: [tdog] This is keeping me up nights...

Nice!!!

The original was not even in color.

http://www.isporty.com/images/cms/blog/188.jpg

http://photo2text.com/ Smile

Smile

Calvin19 Oct 4, 2007, 6:09 PM

Re: [Bolas] This is keeping me up nights...

i kinda liked learning more about special and general relativity.

annibal Oct 6, 2007, 9:36 AM

Re: [Calvin19] This is keeping me up nights...

There once was a lady named Bright
who could travel much faster than light.
She took off one day, in a relative way,
And returned late the previous night.

Laugh

Laugh

There's relativity for ya.

yuri_base Jan 21, 2008, 10:18 AM

Re: [Ghetto] This is keeping me up nights...

While researching what causes this tiny jolt when you press the button on a laser rangefinder, like a recoil of a gun (you need to stop breathing and concentrate your supersensitive ninja senses to feel it), I bumped into the notion of jerk. Jerk is the rate of change in acceleration, or the third derivative of the displacement:

j = d^3r/dt^3

Moreover, yank is the analog of force with respect to jerk: mass times jerk.

A device which measures jerk is called a "jerkmeter."

A jerk system is a system whose behavior is described by a jerk equation.

When you press that button, heighten your senses and feel the jerk of radiation.

But what if the jerk is accelerating or decelerating - what is the rate of change in jerk called??? (d^4r/dt^4) This is keeping me up nights...

Ghetto, discuss.

Calvin19 Jan 21, 2008, 11:55 AM

Re: [yuri_base] This is keeping me up nights...

is there any more info on this 'jerk' from rangefinders? (I know your not talking about little rangefinders)

thats really cool. I want to know more. kinda like the reverse of solar-sailing?

yuri_base Jan 21, 2008, 12:07 PM

Re: [Calvin19] This is keeping me up nights...

Yes, it's like light-propelled rocket. Just install billions of powerful rangefinders on a spaceship and press all those little stopwatch buttons simultaneously for liftoff. Smile

Smile

Ghetto Jan 21, 2008, 12:17 PM

Re: [yuri_base] This is keeping me up nights...

that could become pretty expensive though, after hiring all the super-tiny ninjas to press all those buttons, no?

Ghetto Jan 21, 2008, 12:33 PM

Re: [yuri_base] This is keeping me up nights...

yuri_base wrote:

While researching what causes this tiny jolt when you press the button on a laser rangefinder, like a recoil of a gun (you need to stop breathing and concentrate your supersensitive ninja senses to feel it), I bumped into the notion of jerk. Jerk is the rate of change in acceleration, or the third derivative of the displacement:

j = d^3r/dt^3

Moreover, yank is the analog of force with respect to jerk: mass times jerk.

A device which measures jerk is called a "jerkmeter."

A jerk system is a system whose behavior is described by a jerk equation.

When you press that button, heighten your senses and feel the jerk of radiation.

But what if the jerk is accelerating or decelerating - what is the rate of change in jerk called??? (d^4r/dt^4) This is keeping me up nights...

Ghetto, discuss.

Why, that is such an interesting question!

First, I think there is a flaw in your Yank theory.. if yank is the analog of force with respect to jerk (mass times jerk), but an object's mass is dependent upon its velocity (theory of relativity), then this makes about as much sense as a two-second delay with track-pants.

Alas, back to your original question: what is the rate of change in jerk called?? Quite simple (the following is an excerpt from my third grade advanced-physics-for-tots thesis):

In reply to:

Higher derivatives of displacement are rarely necessary, and hence lack agreed-on names. The fourth derivative of position was considered in development of the Hubble Space Telescope's pointing control system, and called jounce. Many other suggestions have been made, such as jilt, jouse, jolt, and delta jerk. As more distinct terms that start with letters other than "j", the term snap has been proposed for the 4th derivative of position, with "crackle" and "pop" having been suggested - facetiously - as names for the 5th and 6th derivatives.

You see? Snap, Crackle, and Pop. the 4th, 5th and 6th derivatives. Now I dare you to find a name for the 7th... Wink

Wink

Calvin19 Jan 21, 2008, 12:46 PM

Re: [yuri_base] This is keeping me up nights...

dick

Tongue

Was there not a popular idea for not only a solar-propelled 'sailing ship', but a laser propelled sailing ship?

an earth based laser, 'aimed' at the sailing ship.

base736 Jan 21, 2008, 1:14 PM

Re: [Ghetto] This is keeping me up nights...

Ghetto wrote:

that could become pretty expensive though, after hiring all the super-tiny ninjas to press all those buttons, no?

Don't need the super-tiny ninjas if you're not using it as a rangefinder -- just the big button that you push. Learn to think like a manager.

Ghetto Jan 21, 2008, 2:04 PM

Re: [base736] This is keeping me up nights...

where's the fun without the ninjas?

yuri_base Jan 21, 2008, 4:57 PM

Re: [Ghetto] This is keeping me up nights...

In reply to:

Snap, Crackle, and Pop. the 4th, 5th and 6th derivatives. Now I dare you to find a name for the 7th...

You got it in the wrong order: it's Crackle, Snap and Pop. There's no 7th derivative - once it speeded up, accelerated, jerked, crackled, snapped and popped, there's nothing left to talk about.

Ghetto Jan 21, 2008, 5:38 PM

Re: [yuri_base] This is keeping me up nights...

Well then I guess we're done.. all of science has been discovered. Good work guys, let's go home...

Calvin19 Jan 21, 2008, 5:58 PM

Re: [Ghetto] This is keeping me up nights...

I'm still the little kid with no idea what is going on. your going to have to sit me down and explain this shit to me someday.

I still say all we need is more gas. then we can go the speed of light. Tongue

Tongue