“OK, Albert. Go on hit me with the weird stuff from your relativity theory”
You’ve got the idea that movement is relative from our last conversation?
“That bit’s fine.”
Good. The rest of the theory is based on the simple idea that the speed of light in space is constant. It doesn’t matter how fast the source of light is moving, or the speed of someone looking at that beam of light. Also nothing can go faster than the speed of light.
"If I came out of the headlights of a car that was flying through space at half the speed of light, I'd end up going one and a half times faster than you, wouldn't I?"
Unfortunately not, but a good question. Light from the headlights of a car isn't travelling at the speed of light plus the car's speed, but simply at the speed of light.
“How can that happen?”
It’s simple enough really you just have to change a few other rules to make sure that the speed of light is always the same. If the speed of light is always going to be the same, it just means that time slows down as you get faster. The good news is you stay younger longer. The bad news is you get squashed and get heavier and heavier. I’m afraid this next part will sound more like something out of Alice in Wonderland than science so I hope you are ready for this. And you people reading out there, if you are a bit sensitive it might be better to read on with your eyes closed.
“So basically you invented the idea that clocks slow down just to make your theory about the speed of light work?”
Well not exactly, I just started imagining how the universe would work if the speed of light was constant. The rest, slowing down clocks and even E=Mc2 followed from that.
“OK Albert, start by explaining to me why fixing the speed of light makes you convinced that clocks can change speed.”
Imagine someone leaning out of a train travelling at 100 miles per hour and another person standing beside the track. Both of them throw an apple in the direction the train is moving. Which apple will be moving faster?
“The one from the train. It’s starting at 100 miles per hour so it must be moving faster than the one thrown from a standing start.”
Exactly. So change the apple for a torch. Does the light leave the torch faster if the torch is moving?
“I would think so, but you just told me I’m wrong.”
Yes, you are wrong. Even stranger is that to the person on the train and the person beside the track the same beam of light will appear to be going the same speed.
“How can that be true? If I am following a beam of light at half its speed it will move away from me at only half the speed of light.”
Unless time slows down, of course. There is a fairly simple formula that tells you how much time must slow down to make sure that the speed of light will always be the same no matter how fast you are moving.
“Of course, why didn’t I think of that? Albert are you crazy? Why would time slow down?”
To make the universe work properly, time has to slow down as you speed up.
“So why had no-one noticed this slowing down of speeding clocks before you?”
Because it doesn’t happen until you are going very fast.
“How fast is very fast?”
A reasonable fraction of the speed of light, which is something no human has ever done except in their imagination.
“What’s the fastest speed a human has ever travelled at?”
The fastest humans are astronauts. They have to reach a speed of more than 25,000 miles per hour to escape the earth’s gravity. But that’s a tiny fraction of the speed of light, only 0.004%.
“So go on explain what happens at almost the speed of light.”
If you could buy a ticket for a space ship going at 99% of the speed of light, time would go seven times slower than on Earth. If you tried just to spend your sleeping hours whizzing around the moon at 99% of the speed of light, you would face a slight problem. Everything in your body would, from an Earth point of view, slow down. From your point of view, if you could see what was happening on Earth, it would be like watching a video on fast forward. So if you go to sleep on your spaceship for eight hours sleep on Monday evening and came back to Earth the next morning it wouldn't be Tuesday but Thursday morning.
“Is that like time travel?”
It is a sort of time travel but it only lets you go into the future, you can't go back in time with this trick. If you slow down even a bit the effects gets much less. At 10% of the speed of light, a mere 67 million miles per hour, you’d gain less than two days if you spent a whole year travelling. At the end of the day it is easier, cheaper and more effective just to lie about your age like everyone else does than use relativity to stay young.
“How fast is time travelling for us then?”
We are travelling at the speed of light, so for us it is passing normally but compared to earth our clocks are ticking infinitely slowly.
“Infinitely slowly?”
Well when we started out, earth was back in 1223 BC and it’s now 1905 the year I published my theory of special relativity. Does it feel like we’ve been travelling for three thousand years?
“No, but…”
Well there you have it. We could travel the entire universe in no time. We can travel as fast as imagination. You can imagine yourself anywhere in the blink of an eye.
“If we went faster than the speed of light would time go backwards?”
We'll never know because nothing can go faster than the speed of light.
“Why not?”
Because as you get near to the speed of light your mass increases very rapidly. At half the speed of light, a space ship would have a mass 15% more than parked in a space dock. At 99% of the speed of light the mass would have increased sevenfold. At 99.99999% of the speed of light the mass would have increased by over two thousand times. As the mass of a space ship increased it would need more and more energy to accelerate. If it ever reached the speed of light, its mass would be infinite and it would require an infinite amount of energy to accelerate it to a speed greater than the speed of light. Since that would take more energy than is in the whole universe, it can't happen.
“Talking about energy, where does E=Mc2 fit in?”
There are some other laws of the universe about conserving energy or momentum that I needed to tweak to work with relativity. These formula were worked out for moving objects but it turned that at rest, there was one part of the formula still needed. That leftover bit was E=Mc2 which showed that mass and energy are related to each other.
“Tweak? The atomic bomb exists because you worked out how to tweak a mathematical formula. Is there anything else you are going to tell me changes?”
The other thing that changes as you approach the speed of light is your length. In fact everything you try to measure in the direction you are travelling, including distances, shrinks. Everything travelling with you shrinks by the same amount, so you could never measure this shrinkage because anything you tried to measure yourself with would also have shrunk. But someone else travelling slower than you, in relative terms of course, would see you as squashed. Since squashing sounds a little unscientific, scientists call this squashing the Fitzgerald Contraction, named after an Irishman George Francis Fitzgerald who invented it in 1889 more than fifteen years before I worked out special relativity in 1905.
“So Fitzgerald discovered relativity before you?”
No he was trying to explain how ether could exist even if we couldn’t detect it in experiments. He was changing the rules of physics to make old theories work, I was changing them to make my new theory work.
“So what’s to say you are right and he is wrong?”
I kept the strangest fact about relativity until now. When scientists have tested some of these crazy relativity ideas, like time slowing down, they have turned out to be true. Perhaps we’ll talk about that next time, just to prove to you that even though I may be dead I’m not dead crazy.
Enjoyed it? Then Digg it.
[Note. The limericks used here are attributed to that famous author Anonymous, if anyone knows their origin I will give their creator(s) the belated fame they deserve.]
This is the story of a great journey that started with a great thought. One day in 1895 a boy looked into a mirror and wondered what the universe would look like if he could travel on a beam of light. That sixteen year old boy was Albert Einstein and that one thought started him on the road to discover his Theory of Relativity. The great man has been reinvented as Albert 2.0 to come back and blog about a journey through space on a beam of light and explain the science behind everything from atoms, blackholes to global warming. If you've just joined and want to start at the beginning use the index on the left. If you're bored try these links below just for fun.
UNSCRAMBLE EINSTEIN'S BRAIN
PRACTISE SAVING THE WORLD FROM ASTEROIDS
ALIEN CONTACT CALCULATOR
HEAR THE REAL EINSTEIN TALK ABOUT E=Mc2.
Saturday, July 7, 2007
Relatively Weird. How to get younger, thinner and fatter all at the same time.
Labels: Fitzgerald, Relativity, Time, Time Travel
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So we know about the Cosmos (and our local bit of it) from photons (cris-crossing?) the Cosmos. What I'm contemplating now are several notions, wondering whether they have meaning. E.g. Is the Cosmos in a web of timeless information about itself. (Except for Black Holes, which I call css (Cosmic singularities -- both singular and plural, because I tend to feel nausious when I try to imagine being near one) ,
So is there an element of timelessness in the Cosmos? Does time have any meaning to a photon? A beam of photon says it came from a Hydrogen atom that was traveling away from my location at 0.16x the speed of light as it crosses my frame of measurement. Is that the same batch, beam, bunch of photons that left he H atom all those time intervals ago? If time has not passed for it, then is it telling me something that has not experienced time?
I know I wallow in verbage, but for me it's satisfying to keep trying to put things together. Lots of people say the Higgs is the mystery; to me it is time. And time for me to go to lunch. Bye.
Modern physicists speculate past-time may be possible if you were approaching a strong gravitational pull such as a black hole. The black hole's gravity would pull everything in (imagine a big tornado in space) including the fabric of space and time.
If you had a vehicle strong enough to escape it's gravity, you could cut across the top of the black hole, while everything else is being pulled in (including time).
Cutting straight across the top, while time and all else is going in, would effectively bring you into what was the past.
ahh the guy that said that this was bull.... I pitty you, the more I know about realtivity and quantum mechanic's the more y want to know .. it's amazing to scrach the surface of how the universe work's ..
Guess Albert 2.0 cannot spell
Practise is indeed the correct verb. Practice is a noun in those
parts of the world where grammer
still counts.
There are seven of them and they could be released every 5 days.
Vertner Vergon
Mass is velocity invariant. That is the consensus among the advanced physicists today.
In fact none of the weird things that Al claims happen.
The PROOF is in a book entitled
THE DIAGNOSIS OF SPECIAL RELATIVITY.
Also in this book is an explanation of what happens when a beam is emitted from a moving emitter.
You can read more about it in
http//www.exeterpublishing.com
Take for example your explanation of time dilation, where according to you processes on earth as viewed from a relativistically moving spaceship appear to be running at a faster rate than usual. This is utter non-sense, as either observers in the earth or spaceship reference frame can see the other one moving. The key point is we are talking about relative motion. This is usually explained with the standard argument that if you are on a train standing in a station and another train moves past your window you can not with out looking at some external reference tell if it is you moving or the other train. This give rise to the famous twin paradox (one of the twins does in fact age less, however this is because one can not do this experiment with only two inertial frames, as one of the twins has to turn around, breaking the symmetry).
As pointed out above you do not get more massive when moving fast. E=mc^2 is telling us that mass and energy are equivalent, hence how can I say a spaceship gets more massive as it moves faster so it requires more energy to continue increasing it's speed, when mass and energy are effectively the same thing?
If you are interested in special relativity recommend reading any modern physics book such as Serway [1] or Krane [2].
Regards,
Sebastian
[1] http://www.amazon.com/Modern-Physics-Saunders-Golden-Sunburst/dp/0030196825
[2] http://www.amazon.com/Modern-Physics-Kenneth-S-Krane/dp/0471828726
As the great man himself is reputed to have said “Everything should be made as simple as possible but no simpler”.
In reducing relativity to these few introductory pages errors of simplification are inevitable. For more advanced readers including some commentators it should be noted that the notion of mass in relativity and relativistic mass (the mass that is deemed to increase with velocity) in particular is most certainly not a simple concept, but as T. R. Sandin has written in the American Journal of Physics:
“The concept of relativistic mass brings a consistency and simplicity to the teaching of special relativity to introductory students.”
With respect to comments disagreeing that for the photons the earth’s history would be seen to be happening on fast forward, I humbly offer that it is their understanding of relativity and the direction of this journey that is at fault. The counter-claim that events on earth would appear to pass more slowly would be true ONLY if our photons were moving away from the earth. When moving towards the earth, as we are in this thought experiment, the relativistic Doppler effect makes images of events on earth appear to proceed faster - an effect relevant to the mathematics of the twin paradox. Sadly if we were traveling with our photons at the speed of light, then light arriving from earth would be infinitely blue-shifted as we approach rendering it invisible!
In relation to the symmetry and relativity of the situation some of the commentators may wish to ponder the fact that for an object with mass to travel at the speed of light is deemed to be impossible even when the concept of relativistic mass is replaced by considerations of momentum. Hence for a photon monitoring events on earth it is impossible for symmetry to apply as the earth cannot be moving at the speed of light and the photon stationary. It also means that no observer could travel on a light beam rendering this entire imaginary journey impossible but the beauty of imagination and thought experiments is that they make the impossible possible.
If instead of traveling on a beam of light we were on space ship traveling towards earth at close to the speed of light then concepts of relative movement do apply and our life on the space ship would also appear to pass in fast-forward mode as we approached.
Complicated? Yes, hence the need for potentially over-simplified introductions!
Hence your language I just quoted should be equivalent to "If you could buy a ticket for a space ship going at 99% of the speed of light, clock would go seven times slower than on Earth." Such a language that "clock" would go seven times slower than on earth" is impossible to understand. If it were possible, would you explain it?
The word "speed" is always relative. When Einstein imagined to travel at the speed of light, he did not say "relative to what". For instance, he should have said he is traveling at the speed of light relative to his friends, to the earth, to the sun, etc. Following the same logic, we could say that he is traveling at the speed of light relative to [ight] tself. As a matter of fact, every thing is traveling at the speed of light relative to light. You and me are traveling at the speed of light relative to light. Since we are already traveling so fast, as fast as light, has our time come to a stop? Has our clocks stopped functioning? Has our aging process stopped? No, nothing like what Einstein has said is happening. Hence, I think Einstein had a language problem and you, Albert 2.0 inherited the same problem.
I would like you to explaine how the "Proof of the Special Relativity Length Contraction Equation" discussed at http://www.physicsforums.com/blog.php?b=724
can be "proof" it looks more like a "spoof" to me.
If a partical of matter disappears at the point of exceeding the speed of light,it does not exceed the SOL it only tried to and the SOL remains an absolute.
Only by understanding the nature of the death of a universe, we will know the necessity for life in a universe.
MOTTO
We live within a sphere,so is it no wonder that space and time is curved.
The big bang theory is becoming to be known as the big bang fact,however we will always need our imagination.
MOTTO
"We live within a sphere so it is no wonder space and time are curved" - ??? I live in a box shaped house, is space and time square shaped here then??!! What are you talking about?!! You make a fool of yourself.
"however we will always need our imagination." - Way too much of it going where relativity is concerned!
In a way Einstein theory almost hit it but not quiet because he is limited by the speed of light. As I said out original mind is the fastest
If I had hit my head or something I could understand but I did not find a scrach or bump anywhere on my body, Can it be that time stopped in that tunnel.
I have written a paper that proves the point.
Disproving those assertions, develops new concepts.
If anyone wants a copy of the paper just request it and I will e-mail you a copy. (17pp)
vertvergon@gmail.com
www.qwarkz.com
Great blog. Thanks for going to all the effort. Question: Every example I've ever come across has the observer and the emitted light beam travelling in the same direction along the x-axis, necessitating the need for length contraction and the slowing of time for the physics to work. Does this imply that if the light beam were emitted in the opposite direction along the x-axis so that the observer were not 'chasing' the light beam, that measuring rods would have to expand and time to speed up to make the physics work, according to relativity? Keep up the good work. I enjoy reading a little bit every day. Jeff
Before discussing time, it would do well to define it.
Time is the comparison of motions to a standard --- nothing more.
The standard is the rotation of the Earth. A bullet goes 3000 feet a second, a car goes 60 miles in an hour, etc.
Atomic clocks tell time by a frequency. A clock in orbit is traveling tangentially to the receiver of its signal. Ives @ Stilwell proved that an emitter traveling transversely to an observer WILL EMMIT A REDUCED FREQUENCY.
That is the Doppler rate will will be (by coincidence)the same as Einstein's time dilation.
Einstein's dilation is wrong anyway because he has a clock IN APPROACH ticking time SLOWLY.
But an atomic clock in approach will "tick" FASTER (as per Doppler)
Theory cannot buck empiricism.
Does light really move? Maybe it just disturbs the fabric of space.A wave in the ocean ten miles away will evntually reach shore but the water where that wave was is still pretty much at the same place.Could it be similar for photons and lightwaves?