am i right to think that when fitting the brake pipes i have to take special care of having each pipe exactly the same length as the other? it does
matter right? i mean, if one pipe going to the front left is only 50 cm and the one going on the front right is 75cm, the front left wheel should
brake harder than the other one right?
sorry, forgot my a-level physics.
They will be different lenths any way as master cylinder is on the right so pipe would be longer going to left, thats right or im going mad to
Wrong. Makes no appreciable difference.
Pressure is the same in a hydraulic system throughout as the liquid cannot compress hence transmits the same force evenly.
ok so heres another quetion, it will make no appreciable difference if the pipes are different lengths so does this mean that hydraulic pressure can be transmitted at infinite speed??
What?? my brain hurts 
I suppose in theory yes. If all systems such as the pipes, the fluid and pistons worked exactly as they were supposed to.
However in the real world things are never perfect and therefore it will not be infinite. For example, You will never bleed all of the out of the
lines.
Andy
Yeah, the perfect hydraulic system is essentially a rigid mechanical connection, so should be as instantaneous as a solid linkage or [unstretchable]
cable.
But that's now making my brain hurt!! Theoretically a long rod or perfect hydraulic system could transmit information instantaneously, i.e.
faster than the speed of light??? Sounds like it would break laws of physics, but i guess it wouldn't cos that's silly... oh well.
Liam
[Edited on 16/5/06 by Liam]
Im not sure if im right in thinking, there are forces experienced by the fluid from the wall - skin friction. at the start of the brake line, say d=0,
only a tiny fraction of the fluid (i.e. that in direct contact with the hose is slowed), but as you progress down the line, where d is increasing, the
proportion of the free stream fluid is decreasing with respect to the fluid experiencing the skin friction. this is where the the ideal values differ
from the real values, and is about boundary layers.
I think
neither energy, information or matter can exceed the speed of light. If you get a metal bar 2 miles long, when you whack one end the other end will not move instantly, a ripple of compression will move (very fast) to the other end, but the speed of light will never be breached. The same as hydraulic fluid, it doesnt noticably compress but in fact, it does fractionally.
Ah, but as the speed of light isn't a constant and has been proved to vary over the surface of this planet, if you measure the speed of light in
a 'slow' place and whacked the metal bar somewhere else it could exceed the speed of light.
(ok, so this is mickey mouse physics as it wouldn't exceed the speed of light where you are)
You have to take account of reaction time, ie see speed camera -- duh--- brake
or if you're like me.
See speed camera one week at night while on the opposite side of the road over taking a car then realise the reason the road suddenly gets lit up is
because its becoming a duel carriage way. Jump on the brakes to find out one caliper is sticking and the car is trying to turn left into the car
you're overtaking.....
"OH-MY-GOD"
7 days later think.....
"isn't there a speed camera around h"
[FLASH]
BRAKE SPEEDO? Whats it SAY BRA
[FLASH]
10 days later i found out exactly what my speedo said.
(this was a few years ago)
I'm not getting into this one!!!
I feel a headache coming on
Just don't worry about it.
There's more important things in life.
quote:
Originally posted by MikeR
Ah, but as the speed of light isn't a constant and has been proved to vary over the surface of this planet, if you measure the speed of light in a 'slow' place and whacked the metal bar somewhere else it could exceed the speed of light.
(ok, so this is mickey mouse physics as it wouldn't exceed the speed of light where you are)
quote:
Originally posted by JoelP
neither energy, information or matter can exceed the speed of light. If you get a metal bar 2 miles long, when you whack one end the other end will not move instantly, a ripple of compression will move (very fast) to the other end, but the speed of light will never be breached. The same as hydraulic fluid, it doesnt noticably compress but in fact, it does fractionally.
lol, bet superman could do it!
i must confess, ive never actually tested that one myself
[Edited on 16/5/06 by JoelP]
talk about wandering off the subject!!
quote:
Originally posted by JoelP
quote:
Originally posted by MikeR
Ah, but as the speed of light isn't a constant and has been proved to vary over the surface of this planet, if you measure the speed of light in a 'slow' place and whacked the metal bar somewhere else it could exceed the speed of light.
(ok, so this is mickey mouse physics as it wouldn't exceed the speed of light where you are)
true enough, but the real speed of light is that in free space
This reminds me of alevel physics when myself and a mate used to talk nonsense for hours!
quote:
am i right to think that when fitting the brake pipes i have to take special care of having each pipe exactly the same length as the other? it does matter right? i mean, if one pipe going to the front left is only 50 cm and the one going on the front right is 75cm, the front left wheel should brake harder than the other one right?
ok had that in my head as thought B. was starting to dig out my school books to see what you just answered.
how did you guys get from car brakes to discussing the speed of light?!
great forum. never seen one like it!priceless
thanks!
easy - we started out on simple engineering, added complex physics covering levers, added distance and E=MC2
pah ..... now, can someone explain to me why a cat can survive a fall from seven story building but not 6?
i find the whole thing about the speed of light being a fundamental constant very fasciating! a good example is if a space ship was travelling at half
the speed of light away from a light source, the light from the source would still be travelling past it at the speed of light, not one and a half the
speed of light!
the thing that changes is the time that is passing, ie the time is going slower for the spaceship than the light source in comparision.
[Edited on 16/5/06 by trogdor]
LOL
What better place to have a ramble about relativity?!
Ok sorry forget it...
Liam
Its hard to measure the speed of light: you'd need a VERY accurate stopwatch
Did you know that as a travelling object approaches the speed of light, it gets longer in the vector direction in which it is travelling?
No-one actually gives a stuff, its just Physicists theorising.
Ed.
quote:
Did you know that as a travelling object approaches the speed of light, it gets longer in the vector direction in which it is travelling?
you see this is where i find it all b*ll*cks.
in my non physics head the speed of light is just a number. So if i'm going at a smidgen slower than the speed of light and i stick my arm out of
the side of the seven and fire a gun ...... the bullet is going to go ...
amost speed of light + speed of bullet.
it suddenly 'stopping' accelerating due to the speed of light - hows that? the bullet doesn't know to slow down cause of some
theoretical thingy.
makes no sense to me!
plus what if i move my hand? its going almost speed of light + how fast i can move my hand. can i suddenly not see it?
google the michaelson-morley experiment, thats a good start. It seems an odd law because its very different to everyday life, sadly, we have to
take these things into account as our cars get faster and speedos less accurate
either how stuff works or wikipedia has a good introduction to relativity i think. I say introduction, but it very quickly gets mindbending
Liam
the simple way i think of it is that using the simple equation:
speed = distance / time
if u fire a bullet while u are travelling close to the speed of light it can't go faster than this so to keep the equation balanced the time it
takes to travel a set distance will decrease.
this effect does happen while we are moving i beleive but is so minute that it would never register. light does travel at 300,000,000 metres per
second after all!
oh to answer mikeR about the bullet not accelerating, it does the time passing while it accerlates will slow down. ie a second for the bullet will
last a longer time to an observer not moving!
physics is a very weird subject once u get to extremes. also just to hurt every ones head somemore light is a wave and a particle at the same time!
[Edited on 16/5/06 by trogdor]
[Edited on 16/5/06 by trogdor]
aye, wave packets, synch that one,
back to bullets?
its strange how little we know about the world around us, in physics there is one set of equations and ideas for very big things such as galaxies etc
and a completley different set up when u get really small down to molecules and atoms etc. they don't know enough to combine the two.
its the same in oceanography, we know such and such happens, but we don't know why.
Yep, it's what makes our world so great and why we should make the most of every minute on it!!
to true, was one of the reasons i decided to do oceanography, we know so little about the oceans its untrue.
The equations are the same, just the variable affects are different. As you approach the speed of light time itself slows down, so that the bullet
will travel faster than you are but only because time has slowed. To a stationary observer the bullet sppeds away just as you would expect, but since
it's technically impossable to reach the speed of light, does it really matter? You'd need all the energy in the universe and more to
achieve that speed, due to having an infinite mass at v=c. Also, as you achieve the speed of light/cross an event horizon ( there's a phrase to
confuse the masses!) you become infinitely long in an infinitely long space of time. Discuss.
its wierd that if u had enough space u could travel to the future! admitty u would be so far away from where the time u would want to get to would
be....... unless u went halfway then came back!
blackholes are strange too, physics as we know it completley breakes down and is meaningless.
It's not possable to travel forwards in time, however, if you achieved the speed of light time technically stops/slows infiintely. So by the time
you come back/slow down again, you have aged less than everyone else, hence you are in someone elses past, but your present. Wierd hey?
Agreed about the black holes though. They have event horizons, which screw all manner of things up! Such as space, time, distance, mass.......
Basically destroys all known physical laws! Good fun eh?
if i was being pedantic i would say were are all travelling forward in time! but anyways that is true u would not atcually travel through time! it
just sounds cool! there was that experiment with a jumbo jet and two atomic clocks that were scronized and then one of them was flown around the
world. because the jet had been travelling, time would be running slower compared to the one that was stationary.
when the clock got back it was found to be few milliseconds out showing this time dilation effect.
Robert, unless you are building an F1 car don't worry about brake line length. You will never notice the difference. Make sure both sides have
the same length flex-hose though.
This whole speed of light thing sounds a lot like sailing off the edge of the earth to me. In 300years people are going to laugh at us because we
think that something magical happens at a specific speed . There is still light in front of you while you are travelling above light speed so its
not going to get dark or anything. Just like if the pilot farts when he is super sonic the gunner still hears it.
So what about the lady near me that has slowed down light? Does that mean this magic stuff happens sooner?
Cheers.
Back to the serius stuff for Mike, The reason cats die in falls from between 3rd and 6th floor but not above is that they stop panicing and get into
flight mode with all paws spread out this increases aewrodynamic drag and reduces terminal velocity sufficiently for a rough but safeish landing. It
doesn't always apply to overweight or skinny cats. Amazing animals really!
Caber
or another one :
a bullet wich is fired 90degrees with the ground.. will reach the ground in the same amount of time if it just where hold on the same high and if let
to fall.
Offcourse like many pysics rulez this one is only in the vacuum environment (space)
Fired parallel to the ground, surely ??
Who said you can't travel forwards in time???
I'm doing it right now (without any special equipment)
I like to use the rate of 1 second per second, I find it less confusing that way.
cheers
Bob
parallel to the ground is one rule, no air is the second...
The bullit will be moving but also falling because of the graveti..
the only thing wich depends on the bullet speed is the distance wich it travels..
sow in fact it still coud kill someone you just need speed sow you donīt need time, when you donīt need time.. the heigh loss isnīt a point because
you already reached your goal.
think about it.
if it where shot/let fall from 5meteres from the ground and it took him 1sec to reach the ground.
if the bullet travels 2500meters/second
you could shoot someone at 100meters
with only a heigh loss of :
2500/100 =>25
1 / 25 = > 0.04seconds
5/0.04=> 0.008meters 8 milimeters! accurency with that bullit speed...
now you know wy the sniper rifle has that tremendous bullit speed
thanxs of this rule tennis is also sow great!!
Tks
quote:
Originally posted by MikeR
pah ..... now, can someone explain to me why a cat can survive a fall from seven story building but not 6?
quote:
Originally posted by tks
parallel to the ground is one rule, no air is the second...
The bullit will be moving but also falling because of the graveti..
quote:
Originally posted by tks
or another one :
a bullet wich is fired 90degrees with the ground.. will reach the ground in the same amount of time if it just where hold on the same high and if let to fall.
Offcourse like many pysics rulez this one is only in the vacuum environment (space)
Will it matter?
Scientist's answer: Yes
Engineer's answer: No
A Reading from the Book of Armaments, Chapter 4, Verses 16 to 20:
Then did he raise on high the Holy Hand Grenade of Antioch, saying, "Bless this, O Lord, that with it thou mayst blow thine enemies to tiny bits,
in thy mercy." And the people did rejoice and did feast upon the lambs and toads and tree-sloths and fruit-bats and orangutans and breakfast
cereals ... Now did the Lord say, "First thou pullest the Holy Pin. Then thou must count to three. Three shall be the number of the counting and
the number of the counting shall be three. Four shalt thou not count, neither shalt thou count two, excepting that thou then proceedeth to three. Five
is right out. Once the number three, being the number of the counting, be reached, then lobbest thou the Holy Hand Grenade in the direction of thine
foe, who, being naughty in my sight, shall snuff it."
-- Monty Python, "Monty Python and the Holy Grail"
[Edited on 17/5/06 by britishtrident]
Monty Python, a quote for all occasions
No sure it is politically correct these days but it either had to be that or the bit from the Ian Drury song "Ain't Half Been Some Clever
B*****ds"about Einstien saying atoms were the littlest.
Einstein can't be classed as witless.
He claimed atoms were the littlest.
When you did a bit of splittemness,
Frighten everybody shitless.
[Edited on 17/5/06 by britishtrident]
quote:
Originally posted by caber
Back to the serius stuff for Mike, The reason cats die in falls from between 3rd and 6th floor but not above is that they stop panicing and get into flight mode with all paws spread out this increases aewrodynamic drag and reduces terminal velocity sufficiently for a rough but safeish landing. It doesn't always apply to overweight or skinny cats. Amazing animals really!
Caber
looks like i failed!
thats got to be theoretical rubbish as how can a plane fire a gun / rocket when its going x hundred miles per hour.
(i know nothing - just doesn't make sense to me, if i'm in a car doing 30mph and i throw a tennis ball it hits its target at 30mph + what
ever i can add to it! if you don't believe me, pop round to nuneaton and we'll test out my theory )
quote:
Originally posted by chris mason
theoretically if you fired a bullet from a gun while travelling at the speed of light, YOU WOULD BLOW YOUR HAND OFF!!!!!
(don't try this, not as if anyone has the capabilities anyway)
as you pull the trigger the bullet would accelerate and attempt to leave the barrel at say 1000m per sec, but as your travelling at a speed far faster than that, the bullet will remain in the gun and explode as it comes back down the barrel.
only breifed the answers to the original post so apologies if someone has already said this.
Chris
No ..........
because you're saying that the friction on the ball will slow it down and as i've got a motor overcoming the friction i'll keep
going.
I agree,
the bullet will leave my gun at speed of light + 500mph (approx). It will travel at speed of light + 500mph - friction for a while until i catch up to
it.
It will not explode in the gun unless the friction is so high it never leaves the gun. This is different to what i read your original answer to
say.
(i realise i'm coming across very 'angry' here, i'm just rushing to get out to watch the footy, had a crap day and got a stinking
cold. Not angry at all, just really curious about this)
ok, you're spitting is a good way of proving your argument (no i'm not trying it!)
although i stand by tennis ball argument as well.
I think you're theory is more thought out and demonstrates the issues but .....
if we do it in a vacum!!!!!!!!!! aha...... my bullet will break the speed of light!
And to whomever suggested that no one has built a car faster than the speed of sound - you've never seen my car run. Neither have i but my point
is still valid!
what would happen if u fired a gun while travelling just below or at the speed of light is that it would travel away from u as it normally would, just
the time passing for it would be slower than time passing for u. this compensates for not breaking the speed of light, it would be travelling at the
speed of light too.
i think this is correct, or it could be aload of crap, i really should ask my housemate who does physics at degree level but hes out getting wasted!
what about if you had a 100 tonne weight in your 1 tonne car that was going just less than the speed of light, you then threw this behind you -
therefore using newtonion motion propelling you forward ..... would you exceed the speed of light?
What if you farted at the same time? Would it still smell?
u would acclerate, but ur speed wouldn't increase as time would slow down. about the smell i don't know, i guess u would travel so fast u would leave it behind v quickly!
iīm confinced its true.
why? the speed wich has the bullet makes it go away from you.
but the same speed increases the error it has made (in fact it amplifies the angle los)
again its only true if you fire it parallel to the ground, in reality you fire it slightly upwards to compensate the loss of heigh.
due to its speed then the compensate angle is amplified (the heigh above parrallel ground/start level)
in fact you should change the question and ask your self wy would the bullit be longer in the air??
Regards,
Tks
the bullet thing is correct. As you say, what would make it stay up longer. In fact, i suspect it holds true even in air.
If you jump up in a train carriage why doesn't the back wall smack into you instead of you landing back in the same place, if the earth orbits the sun at 18.5 miles (30 kilometres) per second why don't we all get speeding tickets. What's all this got to do with brakes from the first question, which I thought was a p!sstake anyway, if you thought that the brakes weren't going to work properly if the pipes were different lengths you'd never trust them again. I have an added worry as the rear wheels on my car are larger than the fronts so will the back end go faster and I'll end up spinning round on the spot like a top. Don't build a car is my only advice to robertst, the mental effort will cause you nothing but pain and anguish and you will probably end up in a mentalist institution with rubber cutlery, walls and underwear.
this firing a gun at the speed of light - the point being misses is relativity.
all speed mesurements are made with regards to some reference.
the person, gun and bullet in the gun are travelling at the speed of light.
as far as the person is concenred, the speed of the bullet, when fired is measured with the person as the reference so as far as the person is
concerned the bullet goes away as normal, no laws are violated. It is related to the post jumping in a moving carriage.
The thing that puzzles me is what does an external observer see?
depends if he has his eyes open.
Perhaps the question should be, how fast can the observer move his head / eyes to watch me go past at the speed of light firing a gun!
The reason you cannot accelerate a body past the speed of light is that it's mass increases that faster it gets. As you appraoch the speed of light, a bodies mass tends toward infinity, requiring an infinite amount of energy to accelerate it any further. The bullet would not break the light speed barrier!
The faster you travel, the slower time goes as well. As proven in the 80s by taking an atomic clock on supersonic flight across the atlantic.
Astronaughts age slower than people on earth while they are in space travelling at umpteen 1000 mph.
Isnt physics fun
But they also recieve massive amounts of radiation, thus aging them a little faster than all on earth.
That's the funny thing about the speed of light. Since light can be proven to have a mass, how can it go at the speed of light, yet not aquire
infinite mass?
arrgghh - my brain hurts?
surely if an object falls at 9.8m/s and it goes faster than 9.8m/s nothing bad actually happens to it!
why is light different?
What about dark matter - where light can't penetrate? Is this because it is travelling FASTER than the speed of light...
I thought dark merely wasn't visible from earth. Doesn't mean light can't go there, just that we can't detect it.
Light is a VERY funny substance, it can be proved to be both a pure wave form and a discrete particle with a mass. Noramlly these two things are
mutually exclusive. But light has the properties of both, ie travels at the spped of light (impossable for any substance with a mass), but has
discrete energy levels, implying particles and therfore mass.
Aren't back holes made of dark matter...?
quote:
Originally posted by DIY Si
But they also recieve massive amounts of radiation, thus aging them a little faster than all on earth.
That's the funny thing about the speed of light. Since light can be proven to have a mass, how can it go at the speed of light, yet not aquire infinite mass?
black holes are made up from super compressed matter.
dark matter is found everywhere but doesnt interact with normal matter/light/etc so is kinda pointless except to will in some holes in theories.
the speed of pressure (going back to the first post) is the speed of sound in that material so in brake pipe would be ~1200m/s so the longer brake
pipe would mean one side would startbraking first but the time difference would be ~1/10000s.
Going back to the original question, even if you have an infinately long pipe the transfer of force down the pipe will travel at the speed of light, not faster. This is because the repulsion of adjacent molecules' outer electron shells (which provides the incompressible force) travels down the pipe at the speed of light: in effect, its like a giant mexican wave travelling at the speed of light.
No, not the speed of light: the speed of sound in the metal (much faster than the speed of sound in air, but much slower than the speed of light).
Easiest way to look at it is as a compression wave going down the pipe. It'll travel just as a sound wave would in air. Ie at the speed of sound, which will be much, much higher than it is in air.
you could probably make it exceed the speed of sound of a given material if you forced it, with similar effects to a sonic boom. Would be
interesting to see anyway.
Not sure how you'd get it to go that fast. You'd need a very rapidly moving piston to exceed the speed of sound in the fluid. And what would
happen inside the pipe? Or would the pipe just rupture due to the huge force?
Just as a thought, could you fire something at a very high speed into/through a tank of the fluid to get the effect? But how would you fire something
at such a high speed? Probably looking at 5~10+ times the speed of sound in air?
1stly you probably couldnt get the piston to go fast enough it would have to go over 1200m/s which is about 2700mph to break the speed of sound.
2ndly most m/cs the output is smaller than the piston so the fluid would go faster through the connection until it hit mach 1 then the connection
would become a chocked nozzle and the pressure would just increase so that the piston couldnt go any faster. the piston would be doing a few hundred
mph though. all assuming it didnt blow itself apart.
but, assuming your housing was strong enough and you could force the piston fast enough ..........
could it be done? To me it seems, obvious, yes. Just needs an incredibly fast strong piston.
now will someone interject with the correct physics to explain why i'm talking out of my arse as usual
easier to imagine knocking the steel bar rather than the brake fluids, then you can ignore fluid dynamics and stuff. So assuming you accelerated a
mass in a vacuum, maybe by electromagnetism, and smashed it into a long steel bar, its easy to imagine what would happen! The bar would crumple up,
hence proving that you cant send a signal up a bar of steel faster than the speed of wave propigation in steel.
Fascinating, so if you are travelling at the speed of light and look over your shoulder I presume you see nothing?.
According to the saying "you can't find where you're going til you know where you've been" so you'll be lost, like me
reading this thread. And I thought the suspension geometry was hard!!!!
You would see backwards at just below the speed of light. The trick is remebering that time slows down as you approach the speed of light. So as you
approach the speed of light, light still ctaches you up, but very slowly. However, since time has slowed it would appear as normal. At the speed of
light, time should stand still, so you wouldn't be able to turn you're head round!
[Edited on 19/5/06 by DIY Si]
My head is spinning at the speed of light!!!!!!
Ok,
If nothing can exceed the speed of light, and given that black holes have such huge gravitational forces that light cannot escape (hence the name),
surely gravity itself is exceeding the speed of light.
ATB
Simon
It's not that gravity is reaching out to the light (and therefore going faster) it's that the light, being a wave-particle is drwan to the source of gravity. Light for example will "bend" round planets, so it's possable to see something behind the planet. Assuming it's a fair way off mind. Hence, balck holes have such a huge gravitational attraction that they bend the light so much it curves in towards the balck hole in a spiral which ends at the black hole itself. Whatever that is.
but i will now refer you to my previous statement. We have proved on this planet the speed of light varies. Gravity affects it and can slow or speed
it up (a very tiny amount).
SO, if the speed of light isn't constent how can some particles exceed when compared to somewhere else. Doesn't make sense to me.
But i'm soooo far out of my depth i've come out the other side!
Theory of relativity doesn't say that nothing can go faster than the speed of light. It only restricts information and any information carrier
from going faster than light speed. I think the best example I've heard is of a powerful laser aimed millions of miles away into space. The end
of the laser beam would be moving over the speed of light if you started waving the laser around frantically.
Also, speed of light is definitely NOT constant. People have slowed, stopped and restarted light. Its called "slow light". Also do a
search for "Fast light" too . It just seems wrong to me that things would drastically change at the speed of light. People thought
planes would explode at the speed of sound too.
FYI I have nfc what I am talking about. Just trivia I have picked up over the years. I forget who said it, but I like this quote:
"Why do people argue about how many stars there are? Because they will never be proven wrong!"
Applies to the whole light speed thing I think .
Cheers.
quote:
Originally posted by Liam
quote:
Originally posted by JoelP
neither energy, information or matter can exceed the speed of light. If you get a metal bar 2 miles long, when you whack one end the other end will not move instantly, a ripple of compression will move (very fast) to the other end, but the speed of light will never be breached. The same as hydraulic fluid, it doesnt noticably compress but in fact, it does fractionally.
Guess you're right of course. Just that i was thinking more along the lines of a metal rod extending to about the sun. Pull on one end and it'd take 8 minutes for the other end to move. Well yeah i guess it would. How interesting. (and that's ignoring pedantic details like the fact i would struggle to overcome the billions of tonnes of inertia of my metal rod and pull it at all, etc etc etc)
Liam
Some people just don't know how to have a theoretical conversation and try to spoil it with there bully fact boy tatics!
humph, i'm sulking now!
quote:
I think the best example I've heard is of a powerful laser aimed millions of miles away into space. The end of the laser beam would be moving over the speed of light if you started waving the laser around frantically
quote:
Originally posted by DIY Si
quote:
I think the best example I've heard is of a powerful laser aimed millions of miles away into space. The end of the laser beam would be moving over the speed of light if you started waving the laser around frantically
Sorry, but that's wrong. The end of the laser beam is moving forwards at the speed of light and so as you move it side ways the light leaving the laser at that time has just been pointed somewhere else. Only that light moves, not the entire beam. It's not solid remember. And even if it were it would still move with the speed of the compression wave down it, as one particle has to exert a force on the adjacent one, and so on, down the bar to make it move.
). Some of the paradoxes are neat though. theres several reasons why thats all wrong unfortunately, but i cant be arsed to go into it. Too late in the day
but i get what you mean, the dot can move faster than light because it isnt a continous entity.
[Edited on 20/5/06 by JoelP]
Nope, still not true. The dot only appears once the newly aimed leaser has emmited light in that direction and it's arrived at that point. If
you want to look at it from an info carrying point of view, a laser IS an info carrying/emitting device. Just ask any tele comms techy. The dot can
not appear at the new point until the light has arrived, so it can't travel faster than the light making the dot.
For one i agree with someone - that makes perfect sense to me (but then again i like to think of myself as a techy )
quote:
Originally posted by DIY Si
Nope, still not true.
Imagine firing a water cannon at a wall 100m away.
The water is leaving the cannon at 50m/s. So it takes 2 seconds for the water to get to the wall.
You flip the cannon round to a wall 180 degrees away in less than a second. You leave a curved trail of water as you do the move, its not a straight
line moving round because you're moving so quickly.
The shape of the curve will depend on how quickly you move the cannon. Really quickly and the curve will all be at the cannon nozzel. Really slowly
and the curve will be 100m out.
the same is true of light the light, i've just used a different medium.
(folks, i know i've simplied a lot of physics there, but that works out in my head so PLEASE don't tell me i'm wrong).
The point is, the dot isn't a fixed entity (for want of a better word) All the dot is is this emitted light. It isn't a thing in it's own right, it's merely the light running into something and reflecting. Also as you wiggle the laser, the dot would take 100 years to follow your wiggles. (I think you already know this, but for any reading that didn't...) So, going on your thinking, yes the dot may appear to travel 200 light years, but it's a totally different dot caused by totally different photons hitting a different wall. And I may be wrong about this, but I thought light always carried information due to it being a discrete wavelength. Ie if nothing else it carries that info around. Could be wrong on that bit though.
assuming the wall goes all the way round, 100m away, then the 'splodge' would move 314m in one second.
i think we're both singing from the same sheet here si, we agree the dot isnt real or continous and that it (the dot, not the light) can appear
to move damned fast
I think we're arguing over a very minor point in all fairness. I hear what you're saying, just partly being awkward and partly just being
me. Just wasn't sure if you quite understood the thing about it being a different dot.
And about the water cannon, it'll take 3 secs for the water to move round not 1, since you forgot the 2 secs for it to get to the wall.
exactly, the nozel will move round in 1 second but it will take the point of water hitting hte wall 3 seconds.
hold on ....... have i just argued against my own point here?
sorry, both wrong! the original line of water will continue hitting the wall for two seconds before it starts to move! hence still only a
second. Think if you rotated it continously, it would have to keep up.
Yeah there's definately no problem with the 'dot' moving faster than the speed of light, and it definately can. As has been explained
its intuitive to consider the dot as one single entity moving, but it isn't at all. You're just spraying a load of separate photons out
into the universe at a big wall, all at the speed of light, and seeing [some of] them reflect back in a big mexican wave of photons. No single thing
is making the faster-than-light-speed journey along the wall that the dot seems to make. Seeing that dot appear to move faster than light is no more
amazing than the fact that you can simultaneously observe stars that are millions of light years apart by just looking into the sky.
Liam
Nope, still 3 sec 1 sec to move, 2 more for the water to hhit the wall at the new point.
im going to argue for the sake of it now
You're firing water at a wall and its taking two second to reach the wall. You spin it round, taking 1 second to travel the 180 degrees. At this
point, water is still hitting the original spot and will do for another second, and at the end of this second second , water will be halfway towards
the new spot. From now, its only one second til water hits the new spot, and if you wanted to be picky, you can imagine the splodge rushing all the
way round the wall, following the path of the nozzle but 2 seconds delayed, since its taken 2 seconds to reach every spot the nozzle aimed at.
We're still arqueing about the dot type thing really. Just the same as with the light. New point, new splodge.....
Er you're both correct but giving times for different events aren't you?...
DIY Si is saying the total time from the start of the movement of the nozzle to the splodge/dot arriving in the new position on the wall is 3 seconds.
That's correct.
JoelP is saying the time the splodge/dot takes to move on the wall is just 1 second, matching the movement of the nozzle. Also correct. The
splodge/dot simply follows the hose 2 seconds later. For the first 2 of DIY Si's 3 seconds the splodge/dot doesn't go anywhere, then it
moves accross the wall in 1 second, 'magically' exceeding the speed-of-water, just as the laser dot appears to exceed the speed-of-light.
Liam
what he said really ^. We're both right. Which is nice, but on different things.
d'oh
Indeed. And it only took 3-4 pages for someone else to point it out.
Heh heh
Incidentally, the best laymans guide to getting your head round the counter-intuitive wierdness of special relativity I've ever found is
here...
HERE
Manages to show all the concepts very clearly with good diagrams and almost no maths at all!
Hmmmm now then, time to move onto general relativity.... I'll get me coat...
Liam
to make things even weirder, scientists have recently manged to teleport a laser across a room. which is pretty impressive!
also there is a pretty good thery going round that it may be possible to send photons back in time. which means info can be sent back in time.
I sent this post in on christmas day 2007
quote:
Originally posted by trogdor
to make things even weirder, scientists have recently manged to teleport a laser across a room. which is pretty impressive!
also there is a pretty good thery going round that it may be possible to send photons back in time. which means info can be sent back in time.
warp speed mr sulu!
It could become possible if someone figures out how to warp space time enough to create 'tunnels' in spacetime. Can't see it happening
anytime soon, as this would surely require an absolutely awesome amount of power? Ie more than a couple (?) of large stars create. But then in the
past it was considered impossable to go over 35 mph in a train as they thought the speed would suck the air out of your lungs and kill you, so who
knows what tomorrow brings? A apart from more bloody rain and another exciting day at work.
[Edited on 22/5/06 by DIY Si]
yeah its wierd to think when that guy builds this light time machine of his, if it works then messages will come from the future straight away. would
be interesting to see what is sent back!
yeah there is the whole idea of wormholes allowing "shortcuts" through space. it depends on the idea of space being curved tho.
if we are gonna talk about wormholes then we may as well mention parallel universes. they are really interesting! from the work done on string and M
theory which is based on parallel univeres there is apparently 11 diamentions, 10 space one time. instead of 3 space and one time! also from this work
they beleive gravity doesn't originate from this universe. It "leaks" in from a parallel universe, this would explain why its so weak!
quote:
Originally posted by trogdor
yeah its wierd to think when that guy builds this light time machine of his, if it works then messages will come from the future straight away. would be interesting to see what is sent back!
yeah there is the whole idea of wormholes allowing "shortcuts" through space. it depends on the idea of space being curved tho.
if we are gonna talk about wormholes then we may as well mention parallel universes. they are really interesting! from the work done on string and M theory which is based on parallel univeres there is apparently 11 diamentions, 10 space one time. instead of 3 space and one time! also from this work they beleive gravity doesn't originate from this universe. It "leaks" in from a parallel universe, this would explain why its so weak!
Now heres a puzzle:
Do the rules of maths exist and we discover them?
Or do we make up the rules to match what we observe?
If the latter why do they happen to work so well in explaining a lot of what goes on?
well the time travel that i had heard about requires u to build the machine first, as the messages are sent using the same machine in the future that
has been buillt. ie as soon as u switched it on, messages would appear that have been sent on the machine u had just switiched on.
but anyways yes all of this is just theories to explain all the things that we can't explain. i do find it all fasinating tho, especially
parallel universes. i watched the documentry on it again yesterday. was a good alternative to revision!
time is an interesting thing, especially as it can change without all this physics nonsense, the brain has a time perception area, this means that
time can pass quick, ie when u are enjoying urself. or real slow, like when sitting in lectures! so if its slow to u, what is it to everyone else?
time is just how u percieve it.
*ala malibu advert*
i just want to build a sports car
Time was invented by Man to explain growing old. It's a relative thing like size. A lifetime to any mammal would be the same as a lifetime to a human and include the same events, birth, death and the bit in between but the scale is different. When you're born, time begins and when you die, time ends. You may all have your own theories on this like Einstein did and like to think there are ways to beat the system, but I haven't heard of anyone who's done it yet and I won't be holding my breath till I do either.
if we were dogs, or cats, and had a 6 million year evolutionary period like humans, it is possible that, as their lifetime is around 15 human years, a day for us (cats or dogs) would be shorter than for humans.