SR...

Kilarin · Post by **Kilarin** » Mon Feb 13, 2006 7:00 am

roid wrote:TIME ITSELF has mass

Really? I didn't even realize it was Catholic!

snoopy · Post by **snoopy** » Mon Feb 13, 2006 7:36 am

I think I have special relativity down fairly well. Bettina, the way I understood the slow motion thing (and the simultanaity) thing was by looking at it from an information standpoint. For the observer, something doesn't happen until he see's it happen. So, imagine that instead of things being in a constant stream, it comes in pulses, kinda like packets in online games. If the person is moving away from the observer, the following will happen: Lets say that the first packet is sent with the guy 1 mile away from the observer. It takes x amount of time for the signal to get to the observer. Then, the second packet is sent t seconds later, relative to the moving guy, with the guy 2 miles away from observer. It takes 2x times for the packet to arrive (Double the time, because the distance it has to travel is doubled.) So, according to the guy transmitting, there was t time between the packets. According to the observer, there was t+x time between the packets. Take that basic concept and make it into a constant stream of data, and the information comes in slow motion. (Note that both people see each other moving in slow motion... that one takes a but to grasp, too) If they where moving toward each other, they would both see each other moving in fast motion. The one that gave me the toughest time was the ladder through the barn one. I'll post a link when I get home.

snoopy · Post by **snoopy** » Mon Feb 13, 2006 7:45 am

It is also interesting to note that we do see time dialation on the earth. If you put an atomic clock on the top of a tall building, and another at ground level, after a year they will be a few nano seconds off from each other.

My question is this: If everything is relative to everything, how can you ever generate a time difference? Lets say I go on a hypothetical trip to alpha prime and back. So, I doo all this acceleration to get free from the sun, so my time slows down, but I see the opposite- you accelerating away from me, so for my your time slows down. Then I'm zoming along at .99 c - so my time is poking along for you, but for me you are zooming along at .99c, too - so your time is poking along for me. Then, I slow down, turn around, and come back home. When I get home, will our clocks not read exactly the same? According to me, everything happened to you, and your time slowed down. According to you, everything happened to me, and time slowed down for me. So, the acceleration and speed that occured between the two of us couldn't affect our clocks. The only thing that could have slowed my clock more than your clock was Alpha Prime's gravitational field, so my clock would be slower, but only due to the fact that I was more greatly affected by AP's gravitational field than you observers on the earth. (I think that's delving into general relativity, but without general relativity, all of the effects of special relativity wash themselves out when you try to actually get back into the same reference frame.)

Bet51987 · Post by **Bet51987** » Mon Feb 13, 2006 2:17 pm

snoopy wrote:It is also interesting to note that we do see time dialation on the earth. If you put an atomic clock on the top of a tall building, and another at ground level, after a year they will be a few nano seconds off from each other.

My question is this: If everything is relative to everything, how can you ever generate a time difference? Lets say I go on a hypothetical trip to alpha prime and back. So, I doo all this acceleration to get free from the sun, so my time slows down, but I see the opposite- you accelerating away from me, so for my your time slows down. Then I'm zoming along at .99 c - so my time is poking along for you, but for me you are zooming along at .99c, too - so your time is poking along for me. Then, I slow down, turn around, and come back home. When I get home, will our clocks not read exactly the same? According to me, everything happened to you, and your time slowed down. According to you, everything happened to me, and time slowed down for me. So, the acceleration and speed that occured between the two of us couldn't affect our clocks. The only thing that could have slowed my clock more than your clock was Alpha Prime's gravitational field, so my clock would be slower, but only due to the fact that I was more greatly affected by AP's gravitational field than you observers on the earth. (I think that's delving into general relativity, but without general relativity, all of the effects of special relativity wash themselves out when you try to actually get back into the same reference frame.)

The clocks will not read the same. Yours will read much slower and since you were traveling close to (c) the time dilation could be very big...like years.

The earth was in a stationary reference frame and yours was not. Its only when one clock is in accelerated motion with respect to the other that time dilation occurs for that clock.

Bettina

Bet51987 · Post by **Bet51987** » Mon Feb 13, 2006 2:37 pm

Diedel wrote:Ooooh, Bettina is discovering the marvels of physics ...

How about some practical application?

There was a true story of a man caught passing a red traffic light. In trial he told the judge that he had been travelling so fast that the red light had appeared green to him. The judge knew a thing or two about physics, so he made a little calculation and fined the guy for speeding: He would have needed to cruise at one third of the speed of light to achieve that effect ... hrch hrch hrch ...

No, I haven't just discovered physics. I've been a member of a science forum for over a year now. Its always been a hobby of mine. Its just lately resurfaced because I fell in love with Einstein. I mean if I was born during his time and at his age, I would have married him. He was the most facinating person I have ever read about, and I've downloaded tons of his material to study.

My other hero is a girl whose works I've also been following. Her name is Lisa Randall, and in 2007 she is going to surprise us, I hope, with another spatial dimension. I can't wait.

http://msnbc.msn.com/id/10510773/site/newsweek/

Bettina

snoopy · Post by **snoopy** » Mon Feb 13, 2006 3:40 pm

Bet51987 wrote:The clocks will not read the same. Yours will read much slower and since you were traveling close to (c) the time dilation could be very big...like years.

The earth was in a stationary reference frame and yours was not. Its only when one clock is in accelerated motion with respect to the other that time dilation occurs for that clock.

Bettina

Are you sure? Reverse the viewpoints. I'm standing still, and everything else is moving at close to c, as far as I'm concerned. So, why arn't your clocks slowed down?

El Ka Bong · Post by **El Ka Bong** » Mon Feb 13, 2006 3:59 pm

There's Superluminal Communication:

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

And, spura luminal communication !

http://www.theodynamics.com/theoII/chapter3.html

... just to stir in my 2 bits...

Bet51987 · Post by **Bet51987** » Mon Feb 13, 2006 5:00 pm

snoopy wrote:
Bet51987 wrote:The clocks will not read the same. Yours will read much slower and since you were traveling close to (c) the time dilation could be very big...like years.

The earth was in a stationary reference frame and yours was not. Its only when one clock is in accelerated motion with respect to the other that time dilation occurs for that clock.

Bettina
Are you sure? Reverse the viewpoints. I'm standing still, and everything else is moving at close to c, as far as I'm concerned. So, why arn't your clocks slowed down?

It has to do with who is accelerating in reference to the other. If I had a clock on earth, and you had one in a space ship, they would both be the same before you took off. Then, I see you blast off to alpha prime. Since you are doing the accelerating, and I am the initial observer, your clock will run slower to me. To you...it is running normally. When you return and we match up the clocks, yours will be behind mine.

Now....calling me an initial observer only works if I disallow earths gravity...which is negligable anyway.

However, if both of us left in separate rocket ships in different directions, then there is no initial observer and both our clocks are slow with respect to each other....

Bettina

Maybe Suncho can come in with a better explanation...

snoopy · Post by **snoopy** » Mon Feb 13, 2006 5:44 pm

Bet51987 wrote:If I had a clock on earth, and you had one in a space ship, they would both be the same before you took off. Then, I see you blast off to alpha prime. Since you are doing the accelerating, and I am the initial observer, your clock will run slower to me. To you...it is running normally. When you return and we match up the clocks, yours will be behind mine.

My point is that acceleration is relative, too. Any "fixed reference" is nothing more than a random point that we pick in order to mathematically ease the calculations. Let me tease you with this one: I mentioned that clocks at the top and bottom of buildings run at different rates- the fact of the matter is that the clocks at the bottom of the tower run slower than clocks at the top. From the perspective that you are looking at things, the one at the top of the tower is both travelling faster and accelerating more, so it should be the one that runs slower.

the key to the clocks not differing (other than due to gravitational effects) lies in the distance dialation. From your perspective, my time slows, but the distance remains constant. From my perspective, my time marches on same as ever, but the distance I have to travel grows.

fliptw · Post by **fliptw** » Mon Feb 13, 2006 5:46 pm

Superman is flying to the other side of the galaxy from earth. Using his super vision, he spies Supergirl's watch, and keeps an eye on it, as he speeds towards his destination he notices that the faster he gets, Supergirl's watch speeds up, but his watch remains constant.

Supergirl back on earth, and using her supervision, keeps an eye on supermans' watch, and notices it slow down as he moves faster away from her.

Suncho · Post by **Suncho** » Mon Feb 13, 2006 6:46 pm

Superman flies around the earth backwards and time starts going backwards. Explain that one!

I have no idea about any of this sutff guys. General relativity is beyond my scope. But I'm curious to read about it. I'm not really up on my tensor math though.

While four-dimensional pythagorean theorum makes sense to me, this does not. I know that something interesting they say in general relativity is that free fall is an inertial state because space is curved and you're moving in a straight line through curved space.

roid · Post by **roid** » Mon Feb 13, 2006 7:24 pm

damnit Suncho, now we're gonna have to learn this stuff ourselves.

Bet51987 · Post by **Bet51987** » Mon Feb 13, 2006 7:29 pm

snoopy wrote:
Bet51987 wrote:If I had a clock on earth, and you had one in a space ship, they would both be the same before you took off. Then, I see you blast off to alpha prime. Since you are doing the accelerating, and I am the initial observer, your clock will run slower to me. To you...it is running normally. When you return and we match up the clocks, yours will be behind mine.
My point is that acceleration is relative, too. Any "fixed reference" is nothing more than a random point that we pick in order to mathematically ease the calculations. Let me tease you with this one: I mentioned that clocks at the top and bottom of buildings run at different rates- the fact of the matter is that the clocks at the bottom of the tower run slower than clocks at the top. From the perspective that you are looking at things, the one at the top of the tower is both travelling faster and accelerating more, so it should be the one that runs slower.

the key to the clocks not differing (other than due to gravitational effects) lies in the distance dialation. From your perspective, my time slows, but the distance remains constant. From my perspective, my time marches on same as ever, but the distance I have to travel grows.

The clocks in the tower are more about GR than SR. If one clock is at the base of a tower and the other is on top of it, the one on top will run faster. It has nothing to do with time dilation which states that your motion thru time and your motion thru space must always equal the speed of light.

In GR, which deals with the forces of gravity, Einstein proved that time will move slower near a massive body. So the farther you are away from the earths core, the faster your clock ticks. The exact opposite of the rocket in space.

It has something to do with field theory that I haven't yet looked at....but am going to.

Your right, in that its all relative. Many of Einsteins theorys could never be proven until the discovery (invention?) of the atomic clocks which could measure to the billionths of a second and confirm what he predicted.

God, I love him.

Bettina

Kilarin · Post by **Kilarin** » Mon Feb 13, 2006 7:38 pm

This is an excellent site with a lot of cool little animations that explain relativity.

http://www.phys.unsw.edu.au/einsteinlight/

The question of how can both clocks be running slow in a symetrical experiment is addressed on this page
You might also want to explore the fun of the twin paradox

Relativity all makes sense, but it is a bizzare and very counter intuitive sense. It's quite difficult to twist your brain around and I find it confuses me all over again every time I go back to it.

Just remember, Einstein's theory of Relativity boils down to:

All things are relative.
All my relatives are things.
My relatives took all my things.

Bet51987 · Post by **Bet51987** » Mon Feb 13, 2006 7:41 pm

fliptw wrote:Superman is flying to the other side of the galaxy from earth. Using his super vision, he spies Supergirl's watch, and keeps an eye on it, as he speeds towards his destination he notices that the faster he gets, Supergirl's watch speeds up, but his watch remains constant.

Supergirl back on earth, and using her supervision, keeps an eye on supermans' watch, and notices it slow down as he moves faster away from her.

Exactly. Then he comes back and finds her an old maid and leaves her. I like it better if she flew off and he stayed.

Bettina

Bet51987 · Post by **Bet51987** » Mon Feb 13, 2006 7:45 pm

If you really are interested in learning SR, this is the best book I ever read....

Bettina

Kilarin · Post by **Kilarin** » Mon Feb 13, 2006 11:08 pm

By the way, a little hint on something I figured out when linking to Amazon. You don't NEED all of that garbage after the ISBN.

http://www.amazon.com/gp/product/0375727205/
goes to the same page as:
http://www.amazon.com/gp/product/037572 ... oding=UTF8

The rest of it is tracking info, display preferences, etc. And all unecessary. I was having problems with long links getting wrapped in email messages and started playing with what I could cut out and still get to the right book and discovered you can cut out ALL of it after the isbn.

Paul · Post by **Paul** » Tue Feb 14, 2006 11:27 am

Lothar wrote:I believe the theory says no OBJECTS (ie, things with mass/energy) travel faster than light.

Forces are not objects. Gravitational force is instantaneous. One way to think of it is that it's a warping of the fabric of space-time. When an object is in a particular position, it has already warped that fabric. If the object moves, the whole gravity field moves at the same speed. It's not like the gravity closest to the object moves, and then the farther gravity moves -- the whole field moves together.

I believe the general theory is that information can't travel faster than light, whether in the form of objects or forces... so gravity won't travel faster than light, either.

However, the speed of light is itself a tricky concept... light slows down if you send it through glass, water, etc. Particles can go faster than the local speed of light. One way physicists test for high-speed particles is by looking for bursts of light called Cherenkov Radiation in water, which occur when a particle moves faster than the local speed of light.

Furthermore, there have been some studies showing certain gases actually propagate light faster than in a vacuum!

Suncho · Post by **Suncho** » Tue Feb 14, 2006 12:38 pm

Paul wrote: I believe the general theory is that information can't travel faster than light, whether in the form of objects or forces... so gravity won't travel faster than light, either.

General relativity also says that gravity is not a force, but a curvature in space. Just food for thought. =)

Paul · Post by **Paul** » Wed Feb 15, 2006 8:58 am

Suncho wrote:
Paul wrote: I believe the general theory is that information can't travel faster than light, whether in the form of objects or forces... so gravity won't travel faster than light, either.
General relativity also says that gravity is not a force, but a curvature in space. Just food for thought. =)

Point taken... but it's still information.

Capm · Post by **Capm** » Wed Feb 15, 2006 5:58 pm

Time for you runs slower than it was when you were at rest.

This is the problem with relativity - The passage of time is a Constant. Its really my only gripe with any of his works. If you are traveling 50mph, time is not moving slower than if you traveling at 5mph - you just get there faster. This sort of logic would rip the fabric of space-time apart with an object moving to fast. If this was true, then theoreticly you could move fast enough to make time litterally stop or even go backwards, which is absurd - as time only moves forward. (You don't want to get into temporal mechanics anyway - you think relativity is hard to grasp!)

And a curvature in space assumes that space is a 2d plane, which also is absurd, maybe more of a pinching effect or rather, a point of high density of the fabric of space at one point with a spheroid region surrounding where the fabric is stretched (being drawn from low density to high density) which normal logic would tell us should work the other way, which suggests that at some level the fabric of space itself does have definable matter/energy properties.

Suncho · Post by **Suncho** » Wed Feb 15, 2006 6:04 pm

Well actually no. Einstein's theory says you can only travel through three-dimensional space at speeds less than c.

Capm · Post by **Capm** » Wed Feb 15, 2006 6:12 pm

Einstein's theory is wrong.

Hence the debate - everyone is always like, but it was Einstein, he can't be wrong, he was a genius. So they can't let go of this theory and the debate continues because he must be right.

Even a genius can screw up.

Also, Things become easier and make more sense when you stop thinking of the speed of light as a constant when in fact it is a variable, and remember, light is made of particles (objects) and objects at rest stay at rest unless acted upon by an outside force, so what you really have is the (photon density)(force propelled by source) through (matter drag coeficient) = c (as a word problem I'm too lazy to write the formula)

Bet51987 · Post by **Bet51987** » Wed Feb 15, 2006 6:57 pm

Capm wrote:Einstein's theory is wrong.

Hence the debate - everyone is always like, but it was Einstein, he can't be wrong, he was a genius. So they can't let go of this theory and the debate continues because he must be right.

Even a genius can screw up.

Also, Things become easier and make more sense when you stop thinking of the speed of light as a constant when in fact it is a variable, and remember, light is made of particles (objects) and objects at rest stay at rest unless acted upon by an outside force, so what you really have is the (photon density)(force propelled by source) through (matter drag coeficient) = c (as a word problem I'm too lazy to write the formula)

Ummmm... To make a statement that light is not a constant is treading on thin ice. This theory has been tested countless times by physicists using atomic clocks, in all forms of experiments, and the consensus is that light is observed not only to be constant but non varying. Light is not just a particle. Its also a wave that adheres to the maxwell equation. Its called duality. If I'm wrong about this I would like to be corrected with a reputable link.

Bettina

Capm · Post by **Capm** » Wed Feb 15, 2006 7:20 pm

I wrote it wrong sorry
(photon density) factor in force propelled by (force source) through (matter drag coeficient) = c

force source = wave

The speed of light can be altered, therefore it isn't a constant. If you establish the parameters of the speed of light, you can use it as a controlled factor. You have to define the properties of the wave though.

But thats not the point - Time doesn't slow down is my point here. And the observer won't see things in slow motion or at a stop, he'll see them at the speed they happened - but he won't see them until AFTER they happened (time it takes for light reflected from things in question to reach observer's location.)

Bet51987 · Post by **Bet51987** » Wed Feb 15, 2006 8:14 pm

Capm wrote:I wrote it wrong sorry
(photon density) factor in force propelled by (force source) through (matter drag coeficient) = c

force source = wave

The speed of light can be altered, therefore it isn't a constant. If you establish the parameters of the speed of light, you can use it as a controlled factor. You have to define the properties of the wave though.

But thats not the point - Time doesn't slow down is my point here. And the observer won't see things in slow motion or at a stop, he'll see them at the speed they happened - but he won't see them until AFTER they happened (time it takes for light reflected from things in question to reach observer's location.)

The speed of light is constant in a vacuum even though it can be altered. Its direction, not its speed, is altered. However, some scientists say that minute variations in particles can "slow" but cancel out later so the entire wave is still travelling at a constant c.

I would like some links if you get a chance that explains your slow motion stuff. I like to read.

Bettina

Kilarin · Post by **Kilarin** » Wed Feb 15, 2006 11:00 pm

Einstein's theory is wrong.

Well, yes, it is. So is Newtons. At least in the sense that neither theory is complete.

BUT, other then that, are you serious or just trolling? If you are serious, then you need to do some reading. The experimental evidence is unbelievably solid for relativity. There are even particles that survive longer in the atmosphere because they are relativistically slowed. It's counter intuitive, but backed up with VERY solid experimental evidence. WAY to solid to simply dismiss because you don't like it.

Suncho · Post by **Suncho** » Thu Feb 16, 2006 2:46 am

Capm, I'm not going all googly-eyed over Einstein. I'm just trying to talk about what I know about his theories. Do you actually have something to say or are you just here to insult us? I'd be happy to have a look at an alternate theory. Do you have any references?

Suncho · Post by **Suncho** » Thu Feb 16, 2006 2:46 am

Double post.

Paul · Post by **Paul** » Thu Feb 16, 2006 11:52 am

Capm wrote:Time doesn't slow down is my point here. And the observer won't see things in slow motion or at a stop, he'll see them at the speed they happened - but he won't see them until AFTER they happened (time it takes for light reflected from things in question to reach observer's location.)

I found this link based on some research I remembered hearing about: http://www2.slac.stanford.edu/vvc/theor ... ivity.html.

Basically, there are some "muons" that decay very quickly that are generated when cosmic rays strike atoms in the upper atmosphere. They decay so quickly, in fact, that even at the high speeds they travel at, they should not reach the Earth's surface. However, due to relativistic time effects, they do reach the Earth's surface... they go so fast that time runs slower for them, and they can reach the surface before they decay.

Top Gun · Post by **Top Gun** » Thu Feb 16, 2006 1:51 pm

Paul wrote:
Capm wrote:Time doesn't slow down is my point here. And the observer won't see things in slow motion or at a stop, he'll see them at the speed they happened - but he won't see them until AFTER they happened (time it takes for light reflected from things in question to reach observer's location.)
I found this link based on some research I remembered hearing about: http://www2.slac.stanford.edu/vvc/theor ... ivity.html.

Basically, there are some "muons" that decay very quickly that are generated when cosmic rays strike atoms in the upper atmosphere. They decay so quickly, in fact, that even at the high speeds they travel at, they should not reach the Earth's surface. However, due to relativistic time effects, they do reach the Earth's surface... they go so fast that time runs slower for them, and they can reach the surface before they decay.

Yup. I had to do many a problem about those muons in my Modern Physics class last semester.

SR...

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