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[dreiche2]

I was also wondering why a particle does not apply a force on itself.  In fundamental quantum mechanics we were calculating what happens to a particle in a potential field, but the particle itself was not affecting the potential for some reason.  I now realize that this is probably not the whole picture, because there should be bosons involved somewhere.

Yeah that reminds me, if problems crop up with specifically infinities and zeroes and whatever in physics, it's probably more a sign of that our understanding of nature is incomplete or wrong, rather than the maths.

For example, I seem to remember that classically, there is a problem with point like particles like electrons because all the charge would be concentrated in a point, and if you were to compute the energies classically you would get infinite numbers (or something along those lines). However, the solution was not to fix the maths, but to fix classical physics, because in quantum mechanics, if I recall correctly, the problem goes away because of the uncertainty relation / things being wavelike.

[DreamThorn]

I have just had an interesting thought:

If you have a bunch of photons, in each of their frames of reference, all the others are moving at c.  If two photons are moving in the same direction, it works out, because time stands still in a photon's frame of reference due to time-dilation (I think).  If they are moving in opposite directions I get different results.  I guess this is where space-dilation comes in.

I think I shouldn't be surprised that I make a mess of relativity, since it has been so many years since I last used it.  I should spend some time reacquainting myself.

I have to thank the people who showed me how much I have forgotten and/or mangled my knowledge of physics.  This new attitude of mine should help with this year's classes.

[Shoku]

Fake-edit: Ok got beaten on the twin paradox, no wonder with my incredibly long post, but:

The twins paradox stops being a paradox when acceleration (the change in direction) is taken into account.  Acceleration speeds up the relatively traveling twin's time-flow (because of the direction of the acceleration), so they will be the same age when they get back together.

No. The one on earth will be older overall.

Anyway...

Anyway. I believe I asked this in one of the physics-related threads that popped up sometime in the past on this forums, but I don't recall getting a meaningfull answer.
So, is anyone able to explain to me the twins paradox? The guy who taught me physics relegated me to some book that I've never picked up, and I still can't wrap my head around it. Apparently it's somehow resolved during the actual acceleration, or maybe the reversing of movement direction that the ship would have to do at some point, to get back to the point of origin.
I can take some algebra, somewhat less of calculus, if you need to use it, but qualitative explanation would be enough.

Spoiler (click to show/hide)

Yeah, the twin paradox is a mean one because it seems to go against the whole spirit of relativity. To recapitulate, twin A stays on earth, twin B travels with his spaceship with nearly light speed to another planet, turns around, and comes back with nearly light speed. Now, apparently the theory says that the twin on earth will overall have aged more than the twin on the space ship.

From the viewpoint of earth this seems to make sense because from there it looked like time in the space ship was going slower throughout the journey because of time dilation. But, haven't we just just established that everything is relative? Because then, from the ship's point of view it was the earth that travelled away with almost c and then came back, so it should be the clocks on earth that should be going slower, i.e. people on earth should have stayed younger, not the other way around.

So that's the apparent paradox. Now, the short solution, and it definitely makes sense, is to say that the frame of references are not symmetrical in this case, because one was undergoing acceleration, namely the twin on the spaceship as he turned around at the distant planet. Movement is relative, but acceleration is not: When I pass an object in my spaceship, I can't say if it's me that is 'really' moving while the object is stationary, or the other way around; that's all relative. However, when I accelerate towards an object, yes, it will still look as if the object accelerates towards me from my point of view, however, only one of us, namely me, will experience an inertial force, pushing me back into my seat. So acceleration is not just a matter of definition.

Thus, in the case of the twin paradox, the short solution is to say that the frames are not symmetrical or equivalent, and because one experiences acceleration, special relativity does not necessarily tell you what is actually happening from his point of view.

It gets more complicated if you actually do want to describe what exactly happens. I didn't remember too much either, so I just had a quick look at wikipedia, and while wikepedia is not always reliable with science explanations, the article on the twin paradox seems reasonable, and I recognize one of the explanations from uni.

So here are two options of explaining what happens to the twin on the spaceship:

The first one is to think about what actually happened during the de- and acceleration at the distant planet. According to general relativity, experiencing acceleration and experiencing a gravitational pull are equivalent (or rather, the forces themselves might be equivalent). And we know that in a strong gravitational field, time will go slower (think of the astronaut approaching the event horizon of a black hole).

That means, as in terms of travelling at constant speed, the situation for both twins is equivalent, and both would observe time dilation in the respective other frame of reference. However, at the mid point of the journey, the spacefaring twin will experience an additional period of acceleration, which means that from his point of view the clocks in the outside world will go faster. And apparently the math gives you that this period of faster clocks on earth is more than enough to make up for the slower clocks on earth during the legs to and from the distant planet, yielding an overall net effect of more time having passed on earth once the twin arrives back home.

The other explanation just uses special relativity, and I remember that one from uni. I think I didn't find it very convincing back then, but having read about it again now on wikipedia, it kind of makes sense. I'm just going to comment on what is written there.

Basically, the argument goes that the space twin arrives at the planet in one inertial frame of references, then de- and accelerates, and then travels back in another frame of reference. So he switches inertial frames (so far no argument to be had here). Now, the argument is that whatever happens during that acceleration (again, which SR doesn't describe per se), you ignore that for now, but you only compare the initial condition, i.e. the first frame of reference, and the outcome of the acceleration, i.e. the second frame of reference (you could assume an instant switch of velocities). You apparently then find than the simultaneity planes have shifted..

uh haha that sounds like bollocks, but I think it actually makes sense (and my theoretical physics prof thought so as well). So: The point is that for any frame of reference, you can draw a Minkowski diagram and see which events at what locations are happening simultaneously in your frame of reference. For example, as the space twin is just about the reach the point of instant re-acceleration, from his point of view his twin on earth is about to lift a cup of coffee at his 25th birthday. Then the space twin changes velocities arbitrarily fast. If we draw again a Minkowski diagram to find out what events are simultaneous in the new frame of reference to the "now" of the space twin (which, for him, is almost the same now as before), we will find that the corresponding events on earth happen much much later on their timescale (e.g., years). So the earth twin might just celebrate his 30th birthday now.

Thus, with these considerations, we could conclude that whatever happened during acceleration (which we cannot describe with SR), apparently the outcome was a shift in time on earth. And if we were to accelerate more smoothly instead of almost instantly, one would expect that during this time the clocks on earth would go faster from our point of view. Which is the same conclusion we draw in the other solution, but now without appealing to gravity and general relativity.

So. For me the second explanation kind of makes sense, but my feeling would be that a full explanation always would involve general relativity.

Hope that made some sense.

You don't seem to see light shooting about at variable rates so how about we say it's relative to light? The absence of light is obviously not going to suddenly stop time dilation and frame of reference distortion but even if it did you'd never be able to find spots all the stars (and CMBR) avoided sending light at.

There are two ways I've seen it described. The first (and possible older and largely discarded,) is that it's matter is really what's set this asymptote and that without any matter light and those things move much faster. Personally I've just figured it's there to make inflation theory work but maybe it's got other justifications.

The other is that space itself grows. With this you can say that galaxies are basically not moving at all (aside from the occasional situation where nearby galaxies aren't distributed evenly so gravity tugs them in a particular direction.) Considering how we've been talking about conditions where distance itself changes rather than just position this shouldn't be all that much to wrap your head around.

So, in essence, accelerating in space accelerates you in time? If yes, then the plot of Gene Rodenberry's Andromeda makes sense. If your ship is sucked into a black hole (and doesn't fall apart), orbiting it at a significant fraction of c, you will effectively enter stasis. I guess I can't hope to explain time compression with just the ambient energy theory (which isn't too different from aether, but still different). I'll go study them particles. We still have to see if it actually works that way though. As mythbusters would say, we have the small-scale results, time to move up to full-scale! (I'd love to see 40th century equivalent of Mythbusters, btw. "Today on Mythbusters, we test the myth that a hypernova can destroy a black hole!")

Btw. Black holes. If it wasn't for all the random atomic crap orbiting them, they'd be perfect for catapulting off into space with the gravity slingshot. Or not. I suspect the gravity gradient would become too steep near the thing's surface, and the ship would be quite effectively torn apart when its bow starts to weigh twenty million times more than its aft.

Also, something strikes me as odd. What exactly prevents you from continuously accelerating if the lightspeed is a limit only for an outside observer? Sure, for the observer your acceleration quickly approaches zero as you approach lightspeed, but if you keep accelerating, to you it should seem that you keep going faster and faster.

Well there are other ways to make time funky. At the edge of a black hole we basically see things freeze in place but it's obviously still mostly empty space until the center- the edge is just the point of no return for any light.

-

Well it's the time dilation and space distortion again. It always looks like you're not moving at all if you use light as the measure. Once you're at .99c you can keep chasing after it if you want. To outside observers you just get really heavy and have really slow time but for you distances stretch and contract so you don't have things wizzing by at what looks like 500c.

Antimatter does not have negative mass. It as opposite electric charges. Antimatter electrons have positive charges, antimatter protons have negative charges. The same holds true at the quark level.

I have no idea where people got the idea that it has negative mass.

You're thinking of Exotic Matter, which actually does have negative mass, but has yet to be discovered anywhere.

I was waiting for someone to say this. Yeah, this thread seems to be 90% made up using the fantasy of many theorist who themselves are becoming discredited over time mainly because their assumptions are never completely explanatory. Someone was able to disprove part of Hawking's theory on Hawking Radiation (that it emits 100% of the particles absorbed, which would explain black hole dissapation and conservation of mass) and showed some mass/energy is permanently lost.. Hawking protested this by saying in other timeline for other universes, it exists... Basically a made up theory to cover a new hole that can't be truly explained. Science about particles becomes dangerously siding on erreonuous qualities when we live off assumptions. That's why if you do not work at a particle accelerator, I don't find you 100% credible.


Edit: Just because we assume the speed of light is the limit, it doesn't mean it is. Think: We call it the limit because light is the fastest thing we have seen. It is the only thing we can see. So, technically there could be ways of faster travel, an unlimited amount, but we cannot see it or detect it unless it abides by the effects of light, otherwise, it'd move so fast, it would literally be invisible.

I thought it was that they realize that the particles leaving a black hole didn't keep any of the qualities they entered it with so that was how information was lost. But then again it's the freaking Discovery channel that taught me that so I could have easily gone on not knowing much about what was really said.

-

Nope. We have a variety of machines for detecting other super-fast quantum-y particle-things. Plus there's linear accelerators launching electrons to show us that you just can't push things enough to make them go faster than c.

Yeah, this is kinda odd. I'd imagine that for a pilot travelling at C, length contraction would kick in to compensate for the limit. So you'd see sprite planets. (correction: you would if you could) Fun.

I think an Alcubierre drive (or stutter warp) is the best way to travel. Hack the universe to allow you to instantly jump a short distance, then repeat as fast as possible. That way you get the ludicrous speed, but still get to enjoy the scenery.

Yay, that stuffs getting through.
-
Isn't it impossible to get out of those things?

One more interesting question I-haven't-thought-about-earlier-but-that-is-probably-covered-already: If you fire a laser, then accelerate to lightspeed, what do you see of the laser? Presuming you can somehow see the laser, of course.

Anywhere below light speed itself the laser seems to do what it always does. If you've got some cloud of little particles sending some of the light back at you (but somehow not punching holes in your and/or your ship- they'd be hitting it at practically light speed after all,) then you see it the same as ever.

However there's one very important point that makes me a total liar there. The energy of photons is based on their wavelength, or color. With just doppler effect type changes any light you're moving toward will end up shorter wavelength. In this case t means that you, say, red laser beam will come back to you as gamma rays or somesuch. Near-regardless of which energy it ends up as though I suggest not looking directly at it, what with retinas having such a low boiling point and all.

But that would mean, essentially, that l light accelerates along with you, no? Or it would mean that light has an effectively infinite (not necessarily actually infinite) speed, and we only see it going as fast as it does due to relativity?

Light's speed is constant (per medium) so there's no acceleration involved. If you're in a vacuum and you generate a photon it's moving at c from its very first moment till its last. That is of course in your reference frame because the photon's reference frame is at light speed so it doesn't have any moments giving yet another reason why they cannot accelerate.

And so, lightspeed is always c,
Because that's what we'll always see.

I would never expect physics to do a double-roundhouse and pack a rhyming pun.

It does it pretty often when you get one of those fellows that's going to have his name remembered and used by average folk in the public.

If they weren't puns I'd probably remember a bunch of them.


-

Boy, page 3 was a doozy. This will double in pages before I get to the seventh one if posts keep growing at this rate. Or maybe mine will grow so much faster time dilation kicks in and I see new posts coming in more slowly. Or length contraction will just make them nice and small for me.

[Sean Mirrsen]

Very nice answering style, Shoku. If you won't mind, an alteration of the "laser drag race" thought experiment. Presuming you accelerate to lightspeed, and a laser (make it an UV one) gets fired alongside you at the exact moment you pass it, what will happen? The laser's light ends up being of shorter wavelength, due to length contraction along your vector, or anything else (though you or any onboard equipment wouldn't perceive it as such, since you'd be length-contracted as well), but will you see a "tip" of the laser? Since it can't change its velocity relative to the laser, and you and the laser "tip" both move at the same speed and along the same vector, it'd "make sense" for light to effectively remain stationary relative to you.

What I'm thinking of this relativistic stuff, is that even if it's right, it fails to describe a basic concept. The speed of light may be a constant, but as a value, a limit, not as a property of light. If you, by some virtue, accelerate to lightspeed, then any light you generate or reflect - and only that light - will keep its lightspeed properties relative to you, much like you can still hear stuff being said in a supersonic jet (or shouted, as the case may be in military jets where soundproofing the cockpit is a secondary concern). Furthermore, it should only be able to keep it up for as long as it remain affected by you. So if, for example, a starship is built that somehow doesn't fall apart and/or disintegrate at lightspeed from collisions with background radiation and microparticles, a flashlight will be useable anywhere within the ship's hull, and anywhere outside the ship where onboard Applied Phlebotinum keeps raging space at bay. There, that's my understanding of it. Sort of an on-the-fly created viewpoint, but oh well.

Also, length contraction could also be a perception-based effect. With light moving at a constant speed, moving towards this light decreases the time difference between the arrivals of the light reflected from the "front" of the object and the "back" of the object.

Spoiler: Obligatory colorful metaphor (click to show/hide)

I don't know if you abroad people still know the rhytmic sounds of a railway car - two pairs of thunks, every time the car crosses from one railway section to the next. When the thunks become faster, it's not necessarily the sections becoming smaller - it may be just the train accelerating.

[dreiche2]

Very nice answering style, Shoku. If you won't mind, an alteration of the "laser drag race" thought experiment. Presuming you accelerate to lightspeed, and a laser (make it an UV one) gets fired alongside you at the exact moment you pass it, what will happen? The laser's light ends up being of shorter wavelength, due to length contraction along your vector, or anything else (though you or any onboard equipment wouldn't perceive it as such, since you'd be length-contracted as well), but will you see a "tip" of the laser? Since it can't change its velocity relative to the laser, and you and the laser "tip" both move at the same speed and along the same vector, it'd "make sense" for light to effectively remain stationary relative to you.

 

I can't tell whether you still don't understand what the special theory of relativity says, or if you just question what it says while happily ignoring experimental evidence.
 
So I ask you now, in the situation you described: What will be the speed of the 'tip' of the laser beam relative to you according to special relativity, ignoring for a second whether you think it's right or wrong?

You don't seem to see light shooting about at variable rates so how about we say it's relative to light? The absence of light is obviously not going to suddenly stop time dilation and frame of reference distortion but even if it did you'd never be able to find spots all the stars (and CMBR) avoided sending light at.

There are two ways I've seen it described. The first (and possible older and largely discarded,) is that it's matter is really what's set this asymptote and that without any matter light and those things move much faster. Personally I've just figured it's there to make inflation theory work but maybe it's got other justifications.

The other is that space itself grows. With this you can say that galaxies are basically not moving at all (aside from the occasional situation where nearby galaxies aren't distributed evenly so gravity tugs them in a particular direction.) Considering how we've been talking about conditions where distance itself changes rather than just position this shouldn't be all that much to wrap your head around.

I don't understand. Are you talking about the twin pardox?

EDIT for Sean: And I assume you mean you accelerate to *almost* c, otherwise my question of what special relativity says is of course pointless.

[Sean Mirrsen]

I mean accelerate to c, not as in relativity says, but absolutely, relative to you. If you have an onboard accelerometer, its readings are not affected by relativity as it applies to an outside observer. If its readings over time add up to ~300.000 km/s, you're at lightspeed, whatever outside observers say about it. This will require VERY unconventional drives though, since by any system you can't accelerate to more velocity than whatever you're using to accelerate travels at.

And if I read all the pro-relativity posts around here right, according to SR the speed of light relative to you will remain the same ~300.000 km/s, whatever speed you travel at. Regardless of the reference frame from which it originated. Which doesn't make sense. I mean, imagine standing still (relatively, anyway) while someone flies past you at C (ok, almost C), firing a laser backwards. Depending on what you use, SR or common sense/logic, the laser will either keep flying at C, but turned into space-ray as its waves flatten, or simply fail to exist as soon as it leaves the barrel, because it will not have any velocity vector, and will dissolve in every direction like waves in a pond. I tend to think it's the latter, and the laser will also quite simply fail to fire because unless shielded, ambient energy flow will disrupt the laser's operation. Indeed, at lightspeed, all of space will immediately turn into an equivalent of penetrating space-ray radiation because of ambient energy.

[dreiche2]

I mean accelerate to c, not as in relativity says, but absolutely, relative to you. If you have an onboard accelerometer, its readings are not affected by relativity as it applies to an outside observer. If its readings over time add up to ~300.000 km/s, you're at lightspeed, whatever outside observers say about it.

Even classically, you cannot measure your own 'absolute' velocity. That's not Einstein, that's Galileo! Your accelerometer can't tell you your 'absolute' velocity either because you don't know what your 'absolute' starting velocity was.

This will require VERY unconventional drives though, since by any system you can't accelerate to more velocity than whatever you're using to accelerate travels at.

Uhm, what?

And if I read all the pro-relativity posts around here right, according to SR the speed of light relative to you will remain the same ~300.000 km/s, whatever speed you travel at.
Regardless of the reference frame from which it originated. Which doesn't make sense. [...]

Evidence. Science starts from evidence, not from what seems or doesn't seem like a nice idea to you.

You just predicted that any light source moving relative to the observer with v will emit electromagnetic radiation at a relative velocity of c-v (if radiating backwards). If that would be true then people would measure photons travelling with less than c all over the place.

E.g., what about pions moving at 0.99975c, emitting light at 1.0 c nevertheless? Or binary stars? The whole universe around us is moving!

So, how come in all those years no scientist ever measured light with velocity different from c? Conspiracy? Or are they all just too dumb?

[Sean Mirrsen]

I can answer both with "waves in the ocean", i.e. the old aether theory.

Now that I think of it, can you link me to the schematics of the/an accelerator? Magnetic field being part of the equation (figuratively, I don't do equations), I'd very much like to take a look and see how it works.

[dreiche2]

I can answer both with "waves in the ocean", i.e. the old aether theory.

No you can't. That's not what your theory says, according to your example. Light in aether would predict a light speed of c constant relative to the aether. As with sound and air. Sound waves always travel with the same speed relative to the frame of reference in which the air is stationary. No matter if the sound source moves relative to the air or not.

In your example, if the observer was stationary with respect to the aether, then the light beam would travel at c relative to it, no matter what the velocity of the travelling laser was. Relative to the laser at almost c, the light would travel at about 2c (shot backwards) or about 0 (shot forwards), which is exactly not what you just described.

Now that I think of it, can you link me to the schematics of the/an accelerator? Magnetic field being part of the equation (figuratively, I don't do equations), I'd very much like to take a look and see how it works.

Nah, you'd have to look it up yourself. However, note that the link refers to 'neutral' pions, so in this case the particles had no charge and thus don't care much about magnetic fields (most likely, the pions themselves are the result of a collision of other particles, which themselves had charge and thus could be accelerated with electromagnetic fields).

[Ampersand]

The speed of light in a vacuum will remain constant relative to the observer regardless of the observers speed due to the effects of Time Dilation. It doesn't matter what makes sense to you, we know this to be the cause due to rigorous experimentation.

http://en.wikipedia.org/wiki/Time_dilation

The laser would propagate as a motionless laser would if fired from a moving ship traveling at speeds approaching C, because relative to the ship, the light of the laser is still traveling at ~300,000 km/s.

Light does not need a starting velocity vector to launch from because it is massless. While it would be massively red-shifted, it would still propagate away from the ship at C, and a motionless observer would see it as traveling at C.

There is a reason traveling at C is impossible, and a reason why time compression takes place at speeds approaching C that causes C to be an relative constant.

The first is Mass-Energy equivalence. I'm not sure if anyone's gone over this yet so, I'll detail it in brief.

Einstein put forth the equation for Mass-Energy Equivalence, Energy (in joules) = mass (in kilograms) multiplied by (299,792,458 meters/second)²

The energy of a joule is defined as the work of one newton acting to move a mass of one kilogram one meter, or the work required to continuously produce one Watt over the course of one second. Lets do a little math here with that in mind. 1 gram = .001 kg.

0.001kg * C = 8.98755179 × 10^13 joules, or 89,875,517,900,000 joules.

In other words, if you could convert one gram of mass into energy with 100 percent efficiency (I.E. Matter/Antimatter annihilation) you would get 89.9 terajoules of energy out of the reaction. When we talk about Mass in this context, we are talking explicitly about the rest mass of the object.

The Einstein equation for determining the moving mass of an object (more recent physicists have made more accurate equations but this one will do,) is defined as  M (moving mass) = m (rest mass)/sqrt(1-(v^2/c^2))

If we begin by stating that the vehicle is motionless, then velocity v is 0. Zero divided by anything remains zero, and 1 minus zero is still one, thus the total mass M is still equal to the rest Mass. If we then asume that v is equal to C, then we get 1 minus 1, or zero, the square root of which is in fact still zero.

The rest mass is 10,000 kilograms. Divide anything by zero and one gets infinity. Therefore, the moving mass of an object with a mass of 10,000 kilograms, or one gram, or .000001 grams, is infinity. Why? It's difficult to explain briefly, but the measure of an objects mass is a direct measure of the objects energy content; as energy is added to the system in the form of motion, it's relativistic mass increases as well. You take the relativistic mass M from the above equation and plug it back into E= MC^2, to determine exactly how much energy was added to the system.

Lets do an easy one. 1 kilogram moving at 10,000,000 meters per second.

(1 kg  (kilogram))/sqrt(1-(10,000,000 m/s  (meters per second))^2/(c^2  (speed of light in vacuum squared))) =.... 1.0005568 kg.

We use the equation to determine the kinetic energy of the object, E= (1/2)M*V.
(1/2)*1kg*(10,000,000 m/s)^2 = 50,000,000,000,000 joules.

This is then confirmed by taking that .5568 grams and plugging it into the E=mc^2, where again we get 50,000,000,000 joules.

Thus the kinetic energy of the object directly adds to the mass of the object.


ERGO, (1. kg  (kilograms))/sqrt(1-(c  (speed of light in vacuum))^2/(c^2  (speed of light in vacuum squared))) = infinity kg

ERGO, Traveling at C is impossible, unless the object has no mass, in which case the mass is 0 * infinity, which is 0, which is why Photons ALWAYS travel at the speed of light.

My brain hurts now.

Your welcome.

[JoshuaFH]

I'm just posting here because I like reading about things I don't understand, and want an easy link to this thread.

[Shoku]

Also, something strikes me as odd. What exactly prevents you from continuously accelerating if the lightspeed is a limit only for an outside observer? Sure, for the observer your acceleration quickly approaches zero as you approach lightspeed, but if you keep accelerating, to you it should seem that you keep going faster and faster.

Nothing keeps you from accelerating. And if you calculate your speed based on stationary distance measurements and your accelerating time measurements, you will perceive that you continually accelerate towards infinite velocity. If you measure things like that, with separate reference frames, then the speed of light would seem essentially infinite (since you will never go faster than light). If however you use the same frame of reference for distance and time, you will find the speed of light is still c, and you are not moving faster than the speed of light relative to any single reference frame.

Light always looks like it's going the same speed so it's not going to seem infinitely fast, it's just going to seem like you weren't going quite as fast as you thought last time you checked. With length contraction you've got a really different game when it comes to how fast you think you're going.

Ok, all you cats talking about That Damn Cat and electrons:
I know that this is a step back from the stuff you have been laying on up here, but I have trouble with something basic that gets in the way of following the less basic. The problm I have is of there being two states, with no in-between. The here or there, one spin or the other, and there is no inbetween.

Isn't this the same as the earlier talk of continuous and non-continuous functions? That it must work for all points? how can it be here, there, and never inbetween? Is it just that "the math sez so" (which I'd regretfully accept), or is there some handle in reality that this can hang on?

Well with electrons you've got two spins in that you can't have two electrons with the same spin in the same orbital of an atom. Instead of 360 degrees this gives 720 degrees though I don't recall how you actually measure that.

A time machine that is actually being built relies on lasers bent into a loop. The light like this has the right properties to twist space-time, or so they say.

[citation needed]

Discovery channel mentions it. Wormholes are a pain what with tidal forces tearing you to shreds but if you do it with something with energy but no mass gravity won't enter the equation.

With the relativity explanation of the tug of gravity just having come from the bends in space-time anyway it seems like there's something wrong with it but it's not like I'll ever see the math or high-end explanation of what's going on so
back to pounding square peg metaphors till they fit into the round holes in my other metaphors.

Anyway they talk about it with the sort of realization that they can't feasibly get enough lasers to do much with it large scale.

But isn't lightspeed relative? Relative to yourself, you wouldn't gain mass as you accelerated, and unless your propulsion system is somehow exempt from relativity, its properties would increase just as well.

Heavier engines don't necessarily produce more thrust.

At the risk of being pre-ninjaed on another item:

Btw. Black holes. If it wasn't for all the random atomic crap orbiting them, they'd be perfect for catapulting off into space with the gravity slingshot. Or not. I suspect the gravity gradient would become too steep near the thing's surface, and the ship would be quite effectively torn apart when its bow starts to weigh twenty million times more than its aft.

That's where the size of the black hole matters.

IIRC (and calculate correctly, also), the bigger the black hole, the further out is its point of no-return but the gradient is less extreme at this point.  So you can (the doomed space-junk and radiation in the accretion disk and polar flares aside) get quite close without the problem of spaghettification.  But you're going to have various other issues to deal with, like the relativistic 'doppler' aging the extremities of the ship differently, meaning you could go into the hold for a few minutes and arrive back a month later, in the right eventualities.

(Imagining designing a ship's systems to be hardened against these problems?  The optical and/or electronic communication lines would need to be able to send/receive signals at vastly different frequencies/baud from the nominal design as required, for a start...)

Gravity goes by distance squared so if you try to go anywhere near the middle you'll run into the same issue. If you're trying some strange oblique angle maybe but I don't know how useful it would be with how time acts at the event horizon.

What I am trying to get at with the divide by zero is that the universe divides by zero occasionally.  If we wish to do proper physics, we need a system that allows us to calculate the effects of such cases.

So, no matter how much you tell me of how dividing by zero doesn't work in real, imaginary, extended or hyperreal numbers, I will still be trying to do it.

So far, handling zero as if it is actually an unknown infinitesimal value has never failed me.  And the multiplicative inverse of such a zero would be a specific but unknown infinite value.  So 1/0 = 1*inf and inf/0 = inf^2 and 5/inf = 5*0.  I would like to know what you think of such a system.

Why would you even say this if you've taken calculus?

Accelerating to and reaching lightspeed is not impossible, nor does it require infinite energy. Simply because we cannot see it happen due to some weird scientific rule, doesn't mean it won't. Even talking within relativity, if you just keep accelerating, you will go faster. Contracting length, extending time, and elusive light don't mean a thing. Within the brilliantly built system, they all cancel out. I don't know what the maths say about it, but accelerating so that you appear to travel at lightspeed to an outside observer may be impossible. But with everything relative, you and your ship will remain relative to yourselves. The planets and stars will move past you faster than light, so they will do everything to appear moving slower than light. Within space as it is, you are still moving faster than light would, and as soon as you decelerate you'll see that you have, indeed, been moving faster than light, as evident from your position. It's a simple bastardization of the principle, but it works. Star Trek warp drives contract and expand space, but it may be that space just warps itself relative to you.

Think about it - if thruster fuel gains mass as the ship speeds up, won't it mean its combustion will produce greater thrust? The ship's hull will increase in mass while keeping its volume, therefore it'll become denser and more resilient. Within logic, if sufficiently warped, it all works out.

Damn, you haven't gotten it.

The problem with your fuel thing is, well, picture two parts hydrogen and one part oxygen. More mass doesn't mean more molecules and the H2O you form will keep a lot of the mass so it was never full energy conversion anyway.

For matter anti-matter interactions you could see it producing more energy but thermodynamics has got you there. If you think about it the energy from whatever type of engine you're using is some specific amount. If it made you go forward at all then you can't have as much energy added to your fuel (as mass.) If the only thing burning your fuel did was make the rest of your fuel heavier then your fuel would just get more effective at that as you burnt it so that would work but you don't want it doing that. You want it pushing the ship around which means not just making your fuel heavier but also the ship and all other contents.

So sure you might be getting more thrust as you reached those high speeds but your ship's mass has to by definition grow fast enough that you don't get anything extra from it, and you're losing a lot of the energy as heat and light anyway so you've got all kinds of losses going on.

And even the changing reference thing doesn't work because light clearly got there before you did and if it was easier to see light without it having to turn around to enter your eye you could watch it the whole time as it was constantly gaining distance from you.

But hey, if you want to nonsensically combine aspects from different frames of reference I guess you could make the math look like you traveled faster than light, so long as nobody was around to explain that it was wrong.

So the Lorentz transformations describe how to do coordinate changes in this 4D space, warping time and space in the process. Length contraction and time dilation are just special cases of the general transformation, much as you can think of special cases of Euclidean rotations. But you don't have to come up with time dilation, length contraction etc. separately to fix your theory in a patchwork like fashion. You start with a general type of transformation, and these different effects just fall out of it.

But there are so many different words! Surely the universe wouldn't take so much vocabulary to explain!

:b

This ain't no luminoferous(sp?) aether. It encompasses everything, not just light. It also emanates from pretty much everything. It's not aether, it's energy. On a different level, it's probably also inspired by "nature tolerates no void", applied to the very bottom of the universe's structure. Energy fills the void between elementary particles.

It's kind of telling when someone sets out to come up with a differing idea than the dominant scientific theory and they dig up the stuff that got thrown out being disproven by said major theory...
oh but it's just space friction that builds up in a non-uniform fashion without actually behaving like friction and not being in all the places it would need to be.

So basically you've taken ancient burnt out ideas to use to explain your um, "new" one that makes complete sense as long as you don't think about it.

Alright alright, I'll stop pressing down on it so hard. Here's the thing your model HAS to do to be worth it's words: predict something. If you can describe something that we haven't discovered yet that ought to be there based on your idea for how it works then you've placed yourself well ahead of most people that set out to do this.

We obviously won't get a chance to check any time soon if ever but if you have this in a way that makes sense (rather than just tacking it on because I asked for it,) then you've done a half-decent job.

And that's page six.

[eerr]

This thread is a great example why people stick to answering a single question at a time. Otherwise closure and coherency are poor.

[Shinziril]

Here's an explanation of time dilation.  Note that this starts with the assumption that the speed of light in vacuum is a constant in all inertial reference frames.  Showing that the speed of light in vacuum is truly constant in all inertial reference frames is done with other experiments. 
(Note: "inertial" means "not accelerating")

Let's postulate a "light clock".  It consists of a laser and photodetector at the bottom, and a mirror at the top some length l above the bottom.  This clock counts time by sending a pulse to the mirror and waiting for it to come back - this will be one "tick", which will be some fraction of a second (determined by the length l). 

There will actually be two clocks.  One clock will be arbitrarily defined to be stationary.  The other clock will be aboard a fast-moving spaceship, passing by the first clock at some constant velocity v.  Now, from the point of view of the first clock, the light "ticks" will be describing a longer path, as they are moving in a triangle (the light moves upwards a distance c*t, where t is a time interval, and the ship moves sideways a distance v*t, where v is the velocity of the ship).  This will create a right triangle with two short sides of length (c*t) and (v*t).  The hypotenuse, along which the light will be seen to be moving by observer 1, will have length sqrt( (c*t)^2 + (v*t)^2 ). 

Note that from the point of view of clock 1, the light in clock 2 is still moving at velocity c (since that is the assumption we made).  This means that the "ticks" of light clock 2 will be longer, since it is moving over a longer path.  Thus, the observer at clock 1 would say that clock 2 is "running slow". 

The interesting thing, and what often confuses people, is that from the point of view of an observer on the spaceship with clock 2 (who defines *himself* as stationary - this is arbitrary but important), light clock 1 is "running slow" (since it is moving backwards at velocity v relative to him).  People are confused because they do not think that these two things can both be true. 

They are *not* paradoxical.  The fact that observer 1 and observer 2 are in different "reference frames" - moving at different relative velocities - changes how they see the rest of the universe. 

Does this make sense?  Please ask if any clarification is required - I actually like explaining this stuff. 

[Ampersand]

Any paradox is resolved by understanding that there exists a universal reference frame against which everything in the universe is compared. The clock in the traveling ship is the one running slow, not compared to the stationary clock, but to the fabric of the universe itself.