## Wednesday, April 15, 2015

### Subject: Time Dilation Explained

Albert Einstein supposedly once said, “You do not really understand something unless you can explain it to your grandmother.”  I think I understand Time Dilation, and I think it can be explained relatively simply.  And I don't need to use complex mathematics (which mainly help prove and compute Time Dilation) or incongruous, fantastical examples, like somehow viewing a clock on a space ship that is a kazillion miles away moving at a kazillion miles per hour while at the same time they are looking at the clock on their kitchen wall on Earth.

I'd like to explain Time Dilation in a somewhat different way.

First, it is very important to understand that Time Dilation has only to do with the movement of an object or person relative to the speed of light or to a stationary object.  It has absolutely nothing to do with the movement of a moving object or person relative to another moving object or person.

Second, instead of two people using different clocks that the other person cannot possibly see, let's use a single natural clock -- a pulsar that both can see.  We just need to pick a pulsar that pulses at an easy-to-use rate -- say one pulse every 10 seconds.  Using such a "clock,"

1 pulse every 10 seconds = 6 pulses per minute.
6 pulses per minute = 360 pulses per hour, or
8,640 pulses per day, or
3,153,600 pulses per year, or
31,536,000 pulses in TEN years, or
31,553,280 pulses when you include 2 leap year days.

Next, let's assume that, on January 1, 2500, a pair of astronomers who also happen to be 25-year-old twins, decide to perform a Time Dilation experiment.  The two astronomer's names are Homebody Jones and Traveler Jones.

The experiment will involve Traveler Jones and his wife taking a space ship on a journey to Alpa Centauri.  Alpha Centauri is 4.3 light years away from Earth, and it is one of the nearest stars to our Solar System.  Homebody Jones will wait back home on Earth.

Since there is no way for either party to see what is happening with the other party via some magical TV signal, Time Dilation will be measured by counting pulses from that distant pulsar.  On Earth, Homebody Jones can observe the pulsar's pulses occurring at the rate of 1 pulse every 10 seconds as described above.

The planned route to and back from Alpha Centauri is within the plane of the rotating beam from the pulsar, and the route will be at a right angle to the oncoming beam from the pulsar, so there will be no effect on pulse counts caused by the speed of light.

The experiment is expected to take 10 years, Earth time.  From the point of view of the two people traveling on the space ship, however, things are soon very different.  They have determined that, aboard the space ship, Traveler Jones will have to travel very close to the speed of light before the effects of Time Dilation will enable him to observe the same pulsar pulsing at an average of 1 pulse every 1 second.

As the space ship begins to accelerate, the number of pulses per minute from the pulsar appears increases due to Time Dilation.  Traveler and his wife record the pulses as arriving more and more quickly until the ship reaches its cruising speed where the pulses are recorded as arriving at a rate of slightly more than 1 pulse per second (to compensate for the time spent accelerating).

Life and time aboard the space ship, however, will seem to be ticking along normally.  The two passengers feel no effects from the slowing down of time aboard the ship.  They still go to bed at 11 p.m. as measured by the clock aboard the space ship, they still get up at 7 a.m., Traveler Jones still has to shave every morning, they eat breakfast at 7:45 a.m., etc.  To them, it doesn't seem like time is slowing down, it appears that everything outside of their space ship is going faster.  They can see that the pulses from the pulsar are coming at a faster rate.  They can also see that planets orbiting distant stars are orbiting at a faster rate.

One month into their voyage, as measured by clocks aboard the space ship, Mrs. Traveler Jones unexpectedly (or maybe according to plan) becomes pregnant.

When they reach a point just beyond Alpha Centauri where they calculated they would need to turn around, they decelerate down to a stop.  When they've done that, they also see that the pulses from the pulsar have slowed down and are once again arriving at 1 every 10 seconds.

Then they accelerate again to return to earth.  Very soon, the pulses from the pulsar are again reaching the space ship at the rate of just slightly more than one per second (in order to compensate for the acceleration and deceleration).

On the voyage home, Mrs. Traveler Jones has a baby boy right on schedule, at the end of a nine month gestation period as measured by her "body clock" and by all the various kinds of clocks aboard the space ship.

Then, on January 1, 2501, according to the clocks aboard the space ship, they arrive back on earth.  Traveler is now 26 years old and his son is 2 months old.

They meet Homebody Jones and find that on Earth it is January 1, 2510.  From Traveler's point of view, he and his wife traveled forward in time nine years.  Only one year passed for them while, from Homebody's point of view, Traveler and wife were gone for ten years.  During that time, Homebody aged 10 years.  He is now 35 years old -- nine years older than his twin brother.

They compare the results of counting pulses from the pulsar, and both counts are exactly the same.  F
rom Traveler Jones's point of view:

1 pulse (on average) every second = 60 pulses per minute.
60 pulses per minute = 3,600 pulses per hour, or
86,400 pulses per day for 365 days, plus
17,280 pulses to compensate for 2 leap year days equals

31,553,280 pulses counted during the ONE year trip.

There were 31,553,280 pulses measured by both devices during the experiment.  From his perspective, it took Traveler just 1 year to record that number of pulses.  From Homebody's point of view, it took 10 years to record the same number of pulses.  Neither twin counted more pulses than the other.  And that means,

No one was ever ahead of or behind the other in time.

The experiment confirmed "time dilation."  Time slows down for a person who is traveling very fast.  But the person doing the traveling sees and feels no effects on himself or his ship.  To people on Earth, it would appear that time had slowed down for the traveler.  It took 90 months for them to have a baby.  For Traveler Jones, it would appear that time had sped up on Earth and in the rest of the universe, as evidenced by the increase in the rate the pulses from the pulsar were received.

For a longer explanation that includes WHY time slowed down, go to my Time Dilation web page by clicking on the link HERE.

Ed

1. I'll begin by answering this question: "What causes Time Dilation?"
The switching and conversion of standards, simple as that.

If you set a STANDARD, then it follows that you MEASURE EVERYTHING TO THAT STANDARD.

You have various standards:
·Pulsar Beat
·Spin of the Earth around the Sun
·Tick of the clock on the ship
·Tick of the clock on Earth
And you switch them around and interchange them.

If you set your standard to be a "Pulsar Beat" (PU-Pulsar Unit), then you have to measure
everything else to that beat and not the other way around.

"Time Dilation will be measured by counting pulses from that distant pulsar".

"Homebody Jones can observe the pulsar's pulses occurring at the rate of 1 pulse
every 10 seconds as described above."
No he can't, since the pulsar's pulses are the STANDARD what he can see is his clock ticking
ten times for every Pulsar Unit.

"Traveler Jones will have to travel very close to the speed of light before the effects of
Time Dilation will enable him to observe the same pulsar pulsing at an average of 1 pulse every
1 second."

Again: No he wont, since the pulsar's pulses are the STANDARD what he can see is his clock ticking
one time for every Pulsar Unit.

"As the space ship begins to accelerate, the number of pulses per minute from the pulsar increases
due to Time Dilation. Traveler and his wife record the pulses as arriving more and more quickly
until the ship reaches its cruising speed where the pulses are recorded as arriving at a rate of
slightly more than 1 pulse per second"

Again: No they wont, since the pulsar's pulses are the STANDARD what they are recording is the clock's tick
decreasing for every PU until it clicks once per PU.

"Life and time aboard the space ship, however, will seem to be ticking along normally."
It would only seem that way if you switch the STANDARD from Pulsar Units to the clock on the ship; if you were to keep the same PU STANDARD things would seem to slow down.

"They can see that the pulses from the pulsar are coming at a faster rate."
They will not, since the pulses ARE THE STANDARD, they don't have a rate.

"They can also see that planets orbiting distant stars are orbiting at a faster rate."
Not with relation to the PU STANDARD; to that STANDARD they orbit at the same rate. "

"Then, on January 1, 2501, *according to the clocks aboard the space ship*, they arrive back on Earth. Traveler is now 26 years old and his son is 2 months old."
So you have switched the STANDARD, now you are using the clocks on the space ship as the standard.
So Traveler is now 26 years old AND SO IN HIS BROTHER according to the clocks aboard the space ship.

"They meet Homebody Jones and find that *on Earth* it is January 1, 2510."
So you have switched the STANDARD, now you are using the clocks on Earth as the standard.

"Only one year passed for them while, from Homebody's point of view, Traveler and wife were gone for
ten years. During that time, Homebody aged 10 years. He is now 35 years old -- nine years older than his twin brother."
Oh my! You changed the STANDARD once again, on this occasion to a Year: one orbit of the Earth around the Sun.
You are saying that the Earth went around once for the Traveler and 10 for the Homeboy?

You said: "They can also see that planets orbiting distant stars are orbiting at a faster rate."
that means that they both counted the same number of spins the Earth did around the Sun; therefore
they both aged the same number of Years.

In conclusion:
They both aged the same amount of Pulsar beats
They both aged the same amount of spins of the Earth around the Sun
They both aged the same amount of "ticks of the clock" on the ship
They both aged the same amount of "ticks of the clock" on Earth

2. In conclusion:
They both aged the same amount of Pulsar beats
They both aged the same amount of spins of the Earth around the Sun
They both aged the same amount of "ticks of the clock" on the ship
They both aged the same amount of "ticks of the clock" on Earth

The clocks are the "measuring sticks" of the standard.

I'll use an analogy:
You have a measuring stick that is one meter long, when you get it wet it shrinks.
That's pretty straight forward because you measure it to the Meter (Standard).

Making the measuring stick the Standard would mean that Space would expand every time the stick gets wet, since more sticks can be place in the same space as the dry stick.
That Space Expansion is as absurd as Time Dilation.

3. Clapton,

Thanks for the comment, but I'm not sure that I follow what you are trying to say.

When measuring "Time Dilation," you are measuring one speed of time against another. If you want to use earth time as the "standard," you will see that Traveler Jones deviated from that "standard."

You wrote:

They both aged the same amount of Pulsar beats
They both aged the same amount of spins of the Earth around the Sun
They both aged the same amount of "ticks of the clock" on the ship
They both aged the same amount of "ticks of the clock" on Earth

That is NOT quite true. It would be "true" (sort of) if it were phrased this way:

They both witnessed the same amount of Pulsar beats
They both witnessed the same amount of spins of the Earth around the Sun
They both witnessed the same amount of "ticks of the clock" on the ship
They both witnessed the same amount of "ticks of the clock" on Earth

They did NOT AGE the same amount. Traveler's BODY aged far less than Homebody's BODY. Plus, the amount of "ticks of the clock" on the ship differed greatly from the amount of "ticks of the clock" on Earth.

I didn't change any "standard." If you want to use Earth time as "the standard," then Traveler's time rate deviated from the standard due to his high rate of travel speed. If you want to use the space ship's time as the "standard," then the "standard" was repeatedly changing as the space ship sped up, cruised and then slowed down. I.e., there was no "standard," there was only an average.

I think what you are saying is that both were the same age based upon the number of orbits the earth made around the sun. True. But, Traveler's BODY is 9 years younger at the end of traveler's trip. His AGE based upon the "normal" age of a human being changed from the "standard."

Maybe the "standard" could be the "average" human life span, but that kind of misses the point.

It's kind of hard to explain in terms using a "standard," and I expect that as soon as I press ENTER I'll think of a better way to explain. But, I hope you understand what I'm trying to explain.

Ed

1. In the recent movie "Interstellar," they didn't use twins. They used a father and daughter. The father was about 30 years old when he went on the high-speed voyage into space. His daughter was about 5 (if I remember correctly).

When the father returned after what he considered to be five years in space, his daughter was an elderly woman about 70 years old.

They both "witnessed" the same number of orbits of the Earth around the Sun, but the father looked and felt (and considered himself to be) 35 years younger than his daughter. His daughter considered her father to have been gone for SIXTY years.

The father experienced "Time Dilation" and his BODY aged at a MUCH slower rate. Time SLOWED DOWN for him, even though the Earth was still going around the Sun at the same "standard" rate.

Where is the change in what "standard"?

Ed

4. "They did NOT AGE the same amount."
What do you mean by "Aging" and how do you measure it?

If you use the Pulsar beats, then they both aged the same number of pulsar beats so they both have the same Pulsar Beat Age.

An example: I bought a couple of Bentley cars 25 years ago, I had atomic clocks installed as extras on both of them.
One of them was stored in a vacuum sealed garage and was never taken out for a spin.
The other one I drove every day, parked it outside under the sun/rain/snow.

Today I placed them side by side, BOTH CLOCKS MARK THE SAME TIME.
Needless to say, the Stationary Bentley LOOKS like it did on the very first day, the Traveler Bentley LOOKS weathered.

So, do they both have the same age, or is the Traveler Bentley older than the Stationary Bentley?

"I didn't change any "standard." If you want to use Earth time as "the standard," then Traveler's time rate deviated from the standard due to his high rate of travel speed."

Lets repeat that with the Pulsar Beat as the standard; this is where you go wrong: "then Traveler's time rate deviated from the standard due to his high rate of travel speed."

No it did not, because THE TRAVELER'S TIME RATE IS THE PULSAR BEAT, the only thing that deviated (from being static) are the clicks of the clock in his ship (the shrinking measuring stick).

"If you want to use the space ship's time as the "standard," then the "standard" was repeatedly changing as the space ship sped up, cruised and then slowed down."

No, the STANDARD NEVER CHANGES, that is why it's a standard. If the standard is variable then It's everything else that changes WITH RELATION to the standard.

Using the measuring stick analogy: I have a foot long measuring stick and I use that as a my standard.
When it's dry and I measure my height: I am 6 sticks long.
When it's wet and I measure my height: I am 7 sticks long.

Conclusion: when the stick gets wet, we have space expansion (absurd).

1. "What do you mean by "Aging" and how do you measure it?"

Aging would be measured by bone density, the thickness of the enamel on your teeth, the elasticity of the skin, and other factors that change with age.

Let's use the "Interstellar" example instead. It's easier to visualize, and you do not start out with identical "cars" or nearly identical people.

The father was about 30 years old when he went on the high-speed voyage into space. His daughter was about 5 (if I remember correctly).

When the father returned after what he considered to be five years in space, his daughter was an elderly woman about 70 years old.

They both "witnessed" the same number of orbits of the Earth around the Sun (and the same number of pulsar pulses), but the father looked and felt (and considered himself to be) 35 years younger than his daughter. His daughter considered her father to have been gone for SIXTY years.

The father experienced "Time Dilation" and his BODY aged at a MUCH slower rate. Time SLOWED DOWN for him, even though the Earth was still going around the Sun at the same "standard" rate.

Where is the change in what "standard"?

Ed

2. Clapton,

Your Bentley analogy reminds me of the Woody Allen movie "Sleeper." In the movie, Allen is put into cryostasis for 200 years to await a cure for some medical problem.

When he awakes after 200 years, he can be considered to be 235 years old, even though he looks and feels 35.

Cryostasis is a form of Time Dilation. The atomic processes are slowed down by lowering the TEMPERATURE instead of by increasing the VELOCITY.

The problem with cryostasis is that you are ASLEEP during the passage of time, so you cannot SEE that time has slowed down for you.

Time Dilation based upon VELOCITY allows you to be awake while time slows down, so you can report on the effects.

A vacuum may preserve a car, but it has nothing to do with time dilation. Vacuum sealing prevents decay caused by interaction with oxygen. So, nothing will rust and nothing will rot. However, the battery will probably be dead, and the tires will probably be flat. There may be other effects of passing time in a vacuum. But, it's not a valid comparison.

Ed

3. Ed,
You have failed to realize that in your example there is no Time Dilation.
If they both counted the same amount of Pulsar Beats, then there is no Time Dilation.
Time Dilation would only occur if both had a different count.

·"From Traveler's point of view, he and his wife traveled forward in time nine years. Only one year passed for them"
The only way "one year has passed for them" is if the Earth would have gone around the Sun once, since he counted the Earth going around the Sun ten times then he is 35 years old, the same as his twin.
Time Dilation would have occurred if the Traveler would have seen the Earth go around the sun once while Homebody would had seen it go around ten times.

·"Aging would be measured by bone density, the thickness of the enamel on your teeth, the elasticity of the skin, and other factors that change with age."
So what would be the age of a six year old that has Progeria? After all, they have the bone density/thickness of the enamel on teeth/the elasticity of the skin of a sixty year old.
Would that kid be six or sixty? Have they experienced "Time Contraction"?

*Interstellar*
"They both "witnessed" the same number of orbits of the Earth around the Sun (and the same number of pulsar pulses), but the father *looked* and *felt* (and *considered* himself to be) 35 years younger than his daughter. His daughter *considered* her father to have been gone for SIXTY years."
This is a Black and White issue, *looked*, *felt* and *considered*, don't play any role.
If the Earth went around the Sun 5 times then they are 5 years older regardless of how they look, feel, or consider themselves.
If the Earth went around the Sun 60 times then they are 60 years older regardless of how they look, feel, or consider themselves.

Is the Bentley that was left in the vacuum sealed garage 1 day old because it looks and feels brand new?
Is the Bentley that was driven daily, and parked outside, 50 years old because it looks and feels weathered?
Or are both of them 25 years old because they were built 25 years ago?

4. Clapton wrote: "You have failed to realize that in your example there is no Time Dilation.
If they both counted the same amount of Pulsar Beats, then there is no Time Dilation.
Time Dilation would only occur if both had a different count."

No, you fail to understand what Time Dilation is all about. I explain very clearly in the text that "NO ONE IS EVER AHEAD OF OR BEHIND THE OTHER IN TIME." If they had a different count, then one would have to be ahead of or behind the other in time. They are counting the same number of pulses, but at a different speed. It takes Homebody what he considers to be 10 years to count the same number of pulses that Traveler counts in what he considers to be 1 year.

Clapton also wrote: "Time Dilation would have occurred if the Traveler would have seen the Earth go around the sun once while Homebody would had seen it go around ten times."

NO. Time dilation is not measured by how many times the Earth goes around the sun. It's measured by HOW FAST the earth APPEARS to be going around the sun. For Traveler it seems to go ten times faster than for Homebody.

The Progeria comment is just argumentative, and helps nothing.

Clapton also wrote: "If the Earth went around the Sun 60 times then they are 60 years older regardless of how they look, feel, or consider themselves."

That is where you fail to understand Time Dilation. YOU may consider them both to be 60 years older, but the father does NOT consider himself to be 60 years older because those 60 years went past at TWELVE TIMES NORMAL SPEED. Each year passed in ONE MONTH, during which he slept 30 times NOT 365, he had 30 bowel movements NOT 365, he ate 90 meals NOT 1,095 meals.

If you want to understand Time Dilation, you need to try to understand how scientists view it. You seem to be arguing that YOUR beliefs are correct, regardless of what anyone else sees, feels, or understands.

Ed

5. Ed,
My beliefs are irrelevant, this is a conceptual issue.

"They are counting the same number of pulses, but at a different speed."

No they are not, the pulses are the Standard to which everything else is measured to.
The pulses are always at the SAME SPEED, it's the other events that change speed with relation to the Pulses/Standard.

If you have a yardstick that you use to measure things with and it changes size:
A) Would you say that the Yardstick expanded or contracted with relation to the YARD (Standard)?
Or
B) Would you say that the YARD (Standard) expanded or contracted with relation to the Yardstick?

While both might be correct, B) has implications on everything else, not just the Yard and the yardstick.

"It takes Homebody what he considers to be 10 years to count the same number of pulses that Traveler counts in what he considers to be 1 year."
It's irrelevant what they consider. This is a fact!:
During the counts, did the Earth go around the Sun once or did the Earth go around the Sun ten times?

"Time dilation is not measured by how many times the Earth goes around the sun. It's measured by HOW FAST the earth APPEARS to be going around the sun. For Traveler it seems to go ten times faster than for Homebody."
If you are going to measure the speed with the pulses (standard) then it would not only APPEAR, IT WOULD BE THE SAME to both because the number of pulses is the same.

"YOU may consider them both to be 60 years older, but the father does NOT consider himself to be 60 years older"
Again, it's irrelevant what I consider. If the Earth went around the Sun 60 times then, by definition, he IS sixty years older.

"because those 60 years went past at TWELVE TIMES NORMAL SPEED."
If he used the Pulse as the Standard then those sixty years went past at NORMAL SPEED.
It's the events in the ship that SLOWED DOWN 12 TIMES the normal speed as measured by the Pulse Standard.
He only slept 30 times but his 'siestas' where 96 hours long by the STANDARD.

6. Clapton wrote: "My beliefs are irrelevant, this is a conceptual issue."

I agree it is a "conceptual issue," but your BELIEFS seem to make you unable to grasp the Time Dilation concept.

Albert Einstein explained time dilation by using two clocks: He wrote: If at the points A and B of K there are stationary clocks which, viewed in the stationary system, are synchronous; and if the clock at A is moved with the velocity v along the line AB to B, then on its arrival at B the two clocks no longer synchronize, but the clock moved from A to B lags behind the other which has remained at B by $\frac{1}{2}tv^2/c^2$(up to magnitudes of fourth and higher order), t being the time occupied in the journey from A to B."

Simply put, he said that Clock-A and Clock-B are a great distance apart, and they both show the same time. Example: 2 p.m. If Clock-A is moved at high velocity to be next to Clock-B, the two clocks will no longer show the same time. Clock-A will lag behind Clock-B. For example, if Clock-B shows the time when Clock-A arrived to be 3 p.m., Clock-A will show something less, depending upon the velocity at which it traveled. It would show 2:55 p.m. if it moved at one velocity, and it would show 2:30 p.m. if it moved at a much higher velocity.

You are arguing that Clock-B is correct and that is all that matters. Nothing else is important.

NO, WHAT IS MOST IMPORTANT IS THAT THE CLOCK THAT MOVED SHOWS LESS TIME HAS PASSED THAN THE CLOCK THAT DID NOT MOVE.

It EXPLAINS why clocks run slower on satellites than on earth. It EXPLAINS why muons traveling at high speed exist longer than muons traveling at slower speeds. It EXPLAINS why an atomic clock flown across the Atlantic on an airplane will show less time has passed than a clock that did NOT move.

You appear to be arguing that you do not want any explanations. The only thing you seem to care about is that the clock that did not move is the "CORRECT" time.

No one is arguing against your belief. I'm just trying to EXPLAIN the scientific concept of Time Dilation and why it happens. Time Dilation EXPLAINS things that happen in the universe. If you do not care about such things, then why argue with people who want to understand science?

Ed

5. Ed,

"Albert Einstein explained time dilation by using two clocks"

Precisely, and that is why YOUR narrative is wrong,

Albert Einstein explained time dilation by using two clocks, AND TWO CLOCKS ONLY.
He did not include any outside time reference because that would mean introducing ABSOLUTE TIME into the equation.

Pulsar Beats are ABSOLUTE TIME.
Years are ABSOLUTE TIME.
Days are ABSOLUTE TIME.
And seconds (as per the Earth standard) are ABSOLUTE TIME.

So, in order for YOUR narrative to be correct you have to eliminate any references to ABSOLUTE TIME, like Pulsar Beats, Years, Days, or Seconds.

In order for your narrative to be correct you would have to utilize "clock ticks", not seconds.

One clock measured more "clock ticks" than the other. I do not disagree.

If I have two synchronized atomic clocks side by side and shake one of the vigorously for one hour, I can guarantee that they will no longer be synchronized.

Q1: Have I caused time to dilate?

In short, Time Dilation is a tale about comparing measuring sticks without any standard present.
I have two identical measuring sticks, if one of them gets wet they are no longer the same size;
when I measure something with them I get different lengths.

Q2: Has the wetness caused space to dilate/contract?

Don't dismiss this question, this is a perfect analogy to Time Dilation.

Two simple questions, Ed.
Q1:_______________________.
Q2:_______________________.

6. Clapton wrote" "If I have two synchronized atomic clocks side by side and shake one of the vigorously for one hour, I can guarantee that they will no longer be synchronized.

Q1: Have I caused time to dilate?"

Answer: NO, of course not. Time dilation is the result of velocity or gravity. It has nothing to do with shaking something. Another fault with your "comparison" is that Time Dilation due to velocity will be the same every time you do it at the same speed. Shaking an atomic clock will produce UNPREDICTABLE RESULTS. Most likely, it will change nothing. But, if the time changes, it could go forward or backward. It is NOT a valid analogy.

Clapton also wrote: "In short, Time Dilation is a tale about comparing measuring sticks without any standard present.
I have two identical measuring sticks, if one of them gets wet they are no longer the same size; when I measure something with them I get different lengths.

Q2: Has the wetness caused space to dilate/contract?"

Answer; NO, of course not. If you want a "standard" in the clock example, the "standard" is the clock that did not move: Clock-B. Your analogy is meaningless, because TIME cannot be compared to a wet stick OR to a Bentley. Those are PHYSICAL OBJECTS. We are NOT talking about measuring physical objects when we talk about Time Dilation. We are talking about measuring TIME.

Using a pulsar to measure Time does NOT introduce an "absolute time" into Time Dilation. All it does is provide a way to measure time that BOTH twins can SEE. The use of clocks requires that Homebody can somehow magically see across trillions of miles of space that Traveler's clock is moving faster than his clock. They still each have their own clocks to use to tell what the "CURRENT" time is where they are. Instead of the clocks ticking at a different rate, they see the pulsar PULSING at a different rate. Traveler sees it pulsing ONCE per second. Homebody sees it pulsing TEN TIMES per second. So, NEITHER can be considered a "standard."

Ed

1. Oops. That last sentence should read: Traveler sees it pulsing TEN TIMES per second. Homebody sees it pulsing ONCE per second. So, NEITHER can be considered a "standard."

Ed

2. "Your analogy is meaningless, because TIME cannot be compared to a wet stick OR to a Bentley."
I'm comparing TIME to SPACE, and I'm comparing clock's with yardsticks.
We use clocks to "measure" TIME, and we use yardsticks to "measure" SPACE.
The analogy is perfectly valid: if "Time Dilation" is caused by slowed down clocks, then "Space Expansion" is caused by a shrunken yardstick.
It's the same thing.

"Using a pulsar to measure Time does NOT introduce an "absolute time" into Time Dilation. All it does is provide a way to measure time that BOTH twins can SEE."
Ed, this is pretty straight forward: If you are using a Pulsar as YOUR reference to "measure" Time, then you are not using the clocks to "measure" Time, all you are doing is counting the clicks against the standard.
The pulsar becomes the Standard to which you measure everything else.
The Pulsar becomes the YARD to which you measure your yardsticks.

"The use of clocks requires that Homebody can somehow magically see across trillions of miles of space that Traveler's clock is moving faster than his clock."
All they have to do is compare the number of clock ticks, from both clocks, at the end of the journey.
In the same manner in which they would compare the length two yardsticks.

"Instead of the clocks ticking at a different rate, they see the pulsar PULSING at a different rate."
This is akin to saying:
"Instead of the yardsticks shrinking or expanding, they see the YARD shrinking or expanding".

This last sentence is the clue to where your narrative goes wrong by including Absolute Time.

You do realize that we never actually "measure" Time, in the same sense that we don't "count" (natural) numbers, or we don't "measure" a Yard?

We use the abstractions Time/Number/Yard to measure or count.

3. Clapton wrote: "The analogy is perfectly valid: if "Time Dilation" is caused by slowed down clocks, then "Space Expansion" is caused by a shrunken yardstick.
It's the same thing."

You are TOTALLY misunderstanding Time Dilation. Time Dilation is NOT "caused by slowed down clocks." That makes no sense whatsoever. Time Dilation is caused by VELOCITY.

And your yardstick analogy is another total misunderstanding.

I'll try explaining Time Dilation in a different way USING "STANDARDS" that you seem to require:

Homebody Jones has a clock in his house. It works the same way and keeps the same rate of time as virtually everyone else on Earth. That should qualify it as the "standard." It's the rate of time EVERYONE on Earth uses. It may be a different time in different Time Zones, but one hour is the same length in ALL Time Zones.

When Traveler Jones get up to 99.5% of the speed of light, the clock on his spaceship will APPEAR to him to be operating normally. HOWEVER, if he could somehow see Homebody's clock across trillions of miles of space, he would perceive the clock in Homebody's house as running TEN TIMES the speed of the clock on the spaceship. Homebody's clock would be ticking off an hour every time Traveler's clock clicks off only 6 minutes.

Likewise, if Homebody could somehow perceive the clock on Traveler's spaceship across trillions of miles of space, Homebody would perceive Traveler's clock as running SLOW. He would see Traveler's clock clicking off just one minute every ten minutes.

Since Homebody is using the "standard" time that everyone else on Earth is using, Traveler's time is clearly NON-standard. Traveler is experiencing "Time Dilation," i.e., Time has expanded or "slowed down" DUE TO HIS VELOCITY.

To double check their findings, both twins can look at a pulsar and count the pulses. Homebody would have the STANDARD VIEW that everyone else on Earth has: he would see the pulsar pulsing once per second. Everyone on earth would see the pulsar pulsing a the "standard" rate of once per second.

Due to the high velocity at which he is moving, Traveler, however, would be experiencing Time Dilation. So his view would be NON-STANDARD. When he looks at the pulsar, he would see it pulsing TEN TIMES PER SECOND. Traveler would see both Homebody's clock AND the pulsar ticking off time at TEN TIMES the "STANDARD" rate.

Neither twin will see anything wrong with their clocks. Everything around them will appear to be running normally. It is ONLY when they look at the other twin's clock that the see the EFFECT of Time Dilation, i.e., of Time slowing down due to Traveler's VELOCITY.

Ed

4. Oops. I wrote: "When he [Traveler] looks at the pulsar, he would see it pulsing TEN TIMES PER SECOND. Traveler would see both Homebody's clock AND the pulsar ticking off time at TEN TIMES the "STANDARD" rate."

I should have written, " When he looks at the pulsar, he would see it pulsing TEN TIMES PER SECOND. Traveler would see both Homebody's clock AND the pulsar ticking off time at TEN TIMES his "NON-STANDARD" rate."

Ed

5. I suppose I should also have pointed out that it is Traveler who is traveling at near-light velocity, so it is ONLY Traveler, his wife (who is with him), their spaceship and everything on the space ship that would experience Time Dilation -- the slowing down of time. His velocity will have absolutely NO effect on Homebody or anyone else on Earth or in the universe.

6. "You are TOTALLY misunderstanding Time Dilation. Time Dilation is NOT "caused by slowed down clocks." That makes no sense whatsoever.
Time Dilation is caused by VELOCITY."

Clocks at high velocity slow down, therefore PERCEIVED Time Dilation.
Yardsticks that are wet shrink, therefore PERCEIVED Space expansion.

■"When Traveler Jones get up to 99.5% of the speed of light, the clock on his spaceship will APPEAR to him to be operating normally. HOWEVER, if he could somehow see Homebody's clock across trillions of miles of space, he would perceive the clock in Homebody's house as running TEN TIMES the speed of the clock on the spaceship."

►In other words: "When Traveler Jones' yardstick gets wet, his yardstick will APPEAR to him to be of normal size. HOWEVER, if he could somehow see Homebody's yardstick (or compare it to the standard), he would perceive Homebody's yardstick as being LONGER than his own yardstick."

■"Likewise, if Homebody could somehow perceive the clock on Traveler's spaceship across trillions of miles of space, Homebody would perceive Traveler's clock as running SLOW. He would see Traveler's clock clicking off just one minute every ten minutes."

►In other words: "Likewise, if Homebody could somehow perceive the yardstick on the Traveler's spaceship across the field, Homebody would
perceive Traveler's yardstick as being shorter. He would see Traveler's yardstick fitting more times in the same space."

■"Since Homebody is using the "standard" time that everyone else on Earth is using, Traveler's time is clearly NON-standard. Traveler is experiencing "Time Dilation," i.e., Time has expanded or "slowed down" DUE TO HIS VELOCITY."
►In other words: "Since Homebody is using the "standard" YARD that everyone else on Earth is using, Traveler's YARD is clearly NON-standard. Traveler is experiencing "Space Expansion", i.e., Space has expanded DUE TO THE WETNESS."

AND SO ON AND SO FORTH...

7. Clayton wrote: "In other words: "When Traveler Jones' yardstick gets wet, his yardstick will APPEAR to him to be of normal size. HOWEVER, if he could somehow see Homebody's yardstick (or compare it to the standard), he would perceive Homebody's yardstick as being LONGER than his own yardstick."

You need to find a different analogy. Why would Traveler's yardstick appear to be normal if getting it wet somehow changes its size? And why would someone else's yardstick (wet or dry) seem longer? Your analogy makes no sense. On what planet do yardsticks become ten times longer when they get ten times as wet?

Time Dilation is a PROVEN FACT. It is dealt with every day when working with satellite communications.

Time slows down for Traveler Jones DUE TO HIS VELOCITY. The faster he goes, the more time will slow down. When he reaches the speed of light, time will STOP completely, because he will no longer be a material object, he will have turned into waves of energy moving through the universe forever.

There's a time dilation calculator at this link: http://keisan.casio.com/exec/system/1224059993

It is currently set to calculate 1 second at 200,000 kilometers per second (kps). When you click on EXECUTE it will show you that at that speed, 1 second for Traveler will be 1.32438 seconds for Homebody, and Traveler will be traveling at 66.7% of the speed of light.

The speed of light is 299,792 kps. If you enter a higher speed than that, the calculator will indicated an error.

If you enter a speed of 299,291 kps, it will show you that 1 second for Traveler at that speed will be 10 seconds for Homebody, and Traveler will be traveling at 99.5% of the speed of light.

I don't see any way to compare that to making a yardstick wet.

On my web page about Time Dilation, I show that the Time Dilation effect seems to be the result of electrons needing to travel further to complete an orbit around the nucleus. The faster you go, the further the electron needs to travel to complete an orbit. This has the effect of slowing down Tim for the object that is moving. It can be a space ship, it can be a person, or it can be a muon created by a collision with a cosmic ray in the upper atmosphere. The faster it is going, the slower time will pass for it. https://en.wikipedia.org/wiki/Time_dilation_of_moving_particles

You need to show how getting a yardstick wet changes its length depending upon how wet it is. When does the yardstick become of infinite length? When it is totally dry or when it is totally wet?

Ed

7. Hi Ed, as much I like the way you explained it, as a beginner I still have a problem explaining that the traveller knowing the pulsar getting faster cab def know that its space shuttle is moving, isn't that contradiction to the fact that we cannot ever surely say who is moving?

8. Anonymous,

Everything in the universe is moving. But, we can ALWAYS tell what is moving relative to something else. Mathematicians have problems telling WHO is moving, because they live in a fantasy world where there are one two objects, and they can't COMPUTE which one is moving. But in REALITY the universe is full of objects and we can easily compare our speed to those of other objects.

Plus, there is "cause and effect" (something else the mathematicians forget). We know the space shuttle is moving because we CAUSED it to move by burning tons of fuel.

Ed