Naked Science Forum
Non Life Sciences => Physics, Astronomy & Cosmology => Topic started by: ankur.jain on 01/02/2016 02:23:57
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Hi,
Although, I used to be a student of science but there is one thing that still haunts me i.e. Time travel.
I understand that the time is just a unit that as human we introduced which is "he duration of 9 192 631 770 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the caesium 133 atom". I completely accept that this phenomenon can be dependent on a number of environmental variables and other fields which when changed would impact the period and gravity is one of those.
From above I understand that if a person on earth using an atomic clock matched to the other atomic clock with another person in space then eventually the atomic clock in space will slow down in relation to the one on earth hence 81 years on earth could be 80 years in space. Having said that I couldn't understand that is it possible that, if the person on earth takes 81 years to complete something then at the same speed the person in space will complete the same in 80 years? or will it be 81 years in space?
I reckon it should be 80 years in space considering time is relative and 80years in space will be equal to 81 years on earth. Similarly the span that the person has lived will be exactly the same on both sides with the only difference that their measuring scales are acting different because of gravity or may be other reasons.
If my assumption is true than I really fail to visualize the concept of time dilation.
Please help me in understanding this and visualize the time dilation.
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As I understand this, the faster one travels, the slower time passes.
For instance, lets say you wanted to travel to a star that is 1000 light years away. We'll call it "VULCAN"...
If you hop in your space ship and accelerate to, lets say 99.99999 percent of the speed of light, YOU would arrive at Vulcan in a very short time period of maybe a month or something like that according to YOUR watch.
However, if someone here on earth was watching your space ship zip through space with a telescope, they'd have to sit there and watch you for a bit over 1000 years.
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However, if someone here on earth was watching your space ship zip through space with a telescope, they'd have to sit there and watch you for a bit over 1000 years.
If what you say is true, that a person on Earth would only have to watch you travel for a bit over 1000 years, then why do you need time dilation? I mean when you arrive on Volcan which is 1000 light years away, then the light of your arrival would be coming from 1000 years in Earths past. Even if you could instanteneously teleported to Volcan, a person on Earth would have to watch Volcan for 1000 years to see you arrive.
This is not explaining clock rate (time dilation), just the slow speed of light. It seems like an illusion.
If Earth saw you arrive in just over 1000 years, then according to Earth you arrived not long after your departure, as anything it sees of Volcan is 1000 years in the past.
The light of your journey was stretched because of the limited speed of light. Not because of time dilation.
Sorry I'm struggling to understand the claim of time dilation in what is called relativistic space flight. And my doubts are centred around the statement you just made.
I have been trying to clarify this in another post as well.
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HAHAHA.. Relativity gives me a headache too...
Your trip to Vulcan will take ~1000 years to anyone observing your spaceship, except you. Since your spaceship is moving so fast, time for you slows down.
If Earth called Vulcan on the sub-space instant communication system (probably made by Verizon [;D]) and said you just left 5 minutes ago and your space ship was traveling very near the speed of light, Vulcan would have to wait ~1000 years for you to get there.. But to you, the trip would only take a very short time.
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If you hop in your space ship and accelerate to, lets say 99.99999 percent of the speed of light, YOU would arrive at Vulcan in a very short time period of maybe a month or something like that according to YOUR watch.
However, if someone here on earth was watching your space ship zip through space with a telescope, they'd have to sit there and watch you for a bit over 1000 years.
This is what my comment refers to. The claim that someone on "Earth" would watch you through a telescope for only a bit over 1000 years.
Not how long the trip seems to you although that's relevant. But making the statement that Earth watching you through a telescope take a bit over 1000 years means that when "Earth" watches you arrive, it is actually light that has taken 1000 years to get to Earth from Volcan. So according to the "Earth" telescope watcher you arrived 1000 years before they saw you arrive.
All the rest is meaningless until this is adequately explained.
If that statement is true then you have travelled 1000 light years in your quoted 50 years by both you and the telescope on Earth. It just took Earth a further 1000 years to confirm the fact, because that is how long it takes light to get to Earth from Volcan.
Where is the time dilation?
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I shouldn't have posted the example in the way I did.. That was a poor way of trying to convey the information.
So lets modify and add a few things to make it easier.
Ship leaves earth at the speed of light and goes to a planet 1000 light years away... Observer watches it travel through space. 500 years later, the ship is at the half way mark, but the observer on earth wouldn't see it at the half way mark until 1000 years has past because, as you infer, it takes another 500 years for the image of the ship to come back to earth. So, 1000 years passes and the earth observer sees the ship at the 1/2 way point.. The ship however, has already reached its destination. If the ship headed back immediately, by the time the observer saw the ship reach its destination, the ship would be arriving back on Earth.
And now I need an aspirin. LOL
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Chance means you either have nearly endless opportunities as to what the future holds .. either that or there is no future until it happens.
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If you hop in your space ship and accelerate to, lets say 99.99999 percent of the speed of light, YOU would arrive at Vulcan in a very short time period of maybe a month or something like that according to YOUR watch.
However, if someone here on earth was watching your space ship zip through space with a telescope, they'd have to sit there and watch you for a bit over 1000 years.
This is what my comment refers to. The claim that someone on "Earth" would watch you through a telescope for only a bit over 1000 years.
Not how long the trip seems to you although that's relevant. But making the statement that Earth watching you through a telescope take a bit over 1000 years means that when "Earth" watches you arrive, it is actually light that has taken 1000 years to get to Earth from Volcan. So according to the "Earth" telescope watcher you arrived 1000 years before they saw you arrive.
All the rest is meaningless until this is adequately explained.
If that statement is true then you have travelled 1000 light years in your quoted 50 years by both you and the telescope on Earth. It just took Earth a further 1000 years to confirm the fact, because that is how long it takes light to get to Earth from Volcan.
Where is the time dilation?
Consider the astronaut in the spaceship is not looking ahead to Volcan, the astronaut is looking out of the rear window with a telescope at the observer on Earth who is looking back with a telescope.
The spaceship reaches a half way point of 500 light years, it takes 500 ly's for the light of the spaceship to reach earth, it takes 500 ly's of the light from earth to reach the spaceship, the net difference is zero, both the spaceship and earth observe 500 lys.
Now at this point the astronaut changes their view and looks ahead to Volcan, on Volcan an observer looks through a telescope at the oncoming spaceship and the spaceship observes back, it takes 500 lys for the light to travel from the spaceship to Volcan, it takes 500 Ly's for the light to travel from Volcan to the spaceship, no net difference observed.
Ok?
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Hi,
Although, I used to be a student of science but there is one thing that still haunts me i.e. Time travel.
I understand that the time is just a unit that as human we introduced which is "he duration of 9 192 631 770 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the caesium 133 atom". I completely accept that this phenomenon can be dependent on a number of environmental variables and other fields which when changed would impact the period and gravity is one of those.
From above I understand that if a person on earth using an atomic clock matched to the other atomic clock with another person in space then eventually the atomic clock in space will slow down in relation to the one on earth hence 81 years on earth could be 80 years in space. Having said that I couldn't understand that is it possible that, if the person on earth takes 81 years to complete something then at the same speed the person in space will complete the same in 80 years? or will it be 81 years in space?
I reckon it should be 80 years in space considering time is relative and 80years in space will be equal to 81 years on earth. Similarly the span that the person has lived will be exactly the same on both sides with the only difference that their measuring scales are acting different because of gravity or may be other reasons.
If my assumption is true than I really fail to visualize the concept of time dilation.
Please help me in understanding this and visualize the time dilation.
There is gravitational time dilation and relativistic dilation I think, two sorts, it is said that a body in motion relative to an observer in an inertial reference frame that time slows down, to visualise this imagine a dripping tap, but when the tap moves the drip slows down.
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Ship leaves earth at the speed of light and goes to a planet 1000 light years away... Observer watches it travel through space. 500 years later, the ship is at the half way mark, but the observer on earth wouldn't see it at the half way mark until 1000 years has past because, as you infer, it takes another 500 years for the image of the ship to come back to earth. So, 1000 years passes and the earth observer sees the ship at the 1/2 way point.. The ship however, has already reached its destination.
OK now we have a new scenario to analyse.
You claim the ship is traveling at the speed of light which is not possible and doesn't fit into the math. So I will assume you meant at almost the speed of light.
You now claim that the Earth reference frame watches the ship uninterrupted for the whole journey of 1000 light years and according to your description the Earth reference frame now watches the ship travel for 2000 years to complete a journey of 1000 light years.
Now my math maybe a bit rusty but that says to me that the Earth frame only ever observes the ship traveling at half light speed.
Remember that the Lorenz transformation requires the Earth frame to witness the ship traveling at almost light speed. It has no place for allowing for the light to separately travel back within the relativity equations that I can find.
The solving of the lorenz transformation clearly gives an answer of a little over 1000 years observation time for Earth reference frame. Not travel time, "observation time".
The Earth frame can not both observe the ship traveling at almost the speed of light and take 2000 years to observe the ship arriving.
What is going on here?
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You claim the ship is traveling at the speed of light which is not possible and doesn't fit into the math. So I will assume you meant at almost the speed of light.
Thank you. Since I am not capable of running the complex mathematics involved, I'd prefer to keep things at a comprehension level rather than a technical level when possible. I do realize sometimes this is not practical.
You now claim that the Earth reference frame watches the ship uninterrupted for the whole journey of 1000 light years and according to your description the Earth reference frame now watches the ship travel for 2000 years to complete a journey of 1000 light years.
Now my math maybe a bit rusty but that says to me that the Earth frame only ever observes the ship traveling at half light speed.
Remember that the Lorenz transformation requires the Earth frame to witness the ship traveling at almost light speed. It has no place for allowing for the light to separately travel back within the relativity equations that I can find.
The solving of the lorenz transformation clearly gives an answer of a little over 1000 years observation time for Earth reference frame. Not travel time, "observation time".
The Earth frame can not both observe the ship traveling at almost the speed of light and take 2000 years to observe the ship arriving.
What is going on here?
You're going to give me a headache thinking of this stuff!!!
So we know that it takes the ship 1000 years to get to its destination (=Fact).. And since its impossible to see the ship at its destination until it arrives (=Fact), it will take an additional 1000 years for the image of the ship to return to the observer on Earth. That's 2000 years. So I would say yes, as the ship travels to its destination, it would appear to an observer to slow down.
Now, if the ship immediately left its destination for the return trip home, I think the reverse would be true as I understand it. The return trip would look very very fast to an observer on Earth. As if the ship was traveling at much faster than light speeds.
The ship took 1000 years to get there, and 1000 years to get back. I think the Earth observer would see the ship take 2000 years to get there, and come back almost instantly (very very very fast). That is, based on my limited understanding of the concepts involved.
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The Earth frame can not both observe the ship traveling at almost the speed of light and take 2000 years to observe the ship arriving.
What is going on here?
You are using the word observe in 2 different contexts.
Relativity does not allow for the light travelling back from the destination because it is only considering travel time.
At a speed of almost light the ship will take just over 1000 yrs to reach its destination. The use of the term observer - on earth - should be read as meaning the time taken in the earth reference frame, which is considered to be at rest. If on arrival the ship sets off a bright light the light will take 1000 years to arrive on earth.
I think you are using the word observed to mean watched ie including time for light to get back to our eyes, which is not what was intended.
Edit: sorry MurBob our post crossed. Welcome to the forum, by the way.
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You claim the ship is traveling at the speed of light which is not possible and doesn't fit into the math. So I will assume you meant at almost the speed of light.
Thank you. Since I am not capable of running the complex mathematics involved, I'd prefer to keep things at a comprehension level rather than a technical level when possible. I do realize sometimes this is not practical.
You now claim that the Earth reference frame watches the ship uninterrupted for the whole journey of 1000 light years and according to your description the Earth reference frame now watches the ship travel for 2000 years to complete a journey of 1000 light years.
Now my math maybe a bit rusty but that says to me that the Earth frame only ever observes the ship traveling at half light speed.
Remember that the Lorenz transformation requires the Earth frame to witness the ship traveling at almost light speed. It has no place for allowing for the light to separately travel back within the relativity equations that I can find.
The solving of the lorenz transformation clearly gives an answer of a little over 1000 years observation time for Earth reference frame. Not travel time, "observation time".
The Earth frame can not both observe the ship traveling at almost the speed of light and take 2000 years to observe the ship arriving.
What is going on here?
You're going to give me a headache thinking of this stuff!!!
So we know that it takes the ship 1000 years to get to its destination (=Fact).. And since its impossible to see the ship at its destination until it arrives (=Fact), it will take an additional 1000 years for the image of the ship to return to the observer on Earth. That's 2000 years. So I would say yes, as the ship travels to its destination, it would appear to an observer to slow down.
Now, if the ship immediately left its destination for the return trip home, I think the reverse would be true as I understand it. The return trip would look very very fast to an observer on Earth. As if the ship was traveling at much faster than light speeds.
The ship took 1000 years to get there, and 1000 years to get back. I think the Earth observer would see the ship take 2000 years to get there, and come back almost instantly (very very very fast). That is, based on my limited understanding of the concepts involved.
This doe's not sound correct,
t=1000years
so let us add a distance and speed.
s=1035 mph
d= 9089230000 mile
From Earth to Volcan 1000 years
From Volcan to Earth 1000 years
Where are you getting 2000 years from?
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This doe's not sound correct,
t=1000years
so let us add a distance and speed.
s=1035 mph
d= 24902000 mile
From Earth to Volcan 1000 years
From Volcan to Earth 1000 years
Where are you getting 2000 years from?
I'm sorry, I don't understand your numbers. Were did you get 1035 mph? or 24.9 million miles?
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Edit: sorry MurBob our post crossed. Welcome to the forum, by the way.
No problem.. Glad you chimed in.. And thank you.. This is fun!
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This doe's not sound correct,
t=1000years
so let us add a distance and speed.
s=1035 mph
d= 24902000 mile
From Earth to Volcan 1000 years
From Volcan to Earth 1000 years
Where are you getting 2000 years from?
I'm sorry, I don't understand your numbers. Were did you get 1035 mph? or 24.9 million miles?
1035 mph is the speed of the Earth's rotation at the equator, the circumference of the equator is 24,902 miles, and it takes approx 24 hrs for one rotation, 365 days is a year,
so if I did my calculation correct, your distance is 24.9 million miles relative to 1035 mph. But I edited since to 9089230000 mile which I still have to double check.
365*24902*1000=9089230000 mile
added - yes the new value
v=1035 MPH OR 0.28821759259 MILE /S 0R APPROX 463M/S
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1035 mph is the speed of the Earth's rotation at the equator, the circumference of the equator is 24,902 miles, and it takes approx 24 hrs for one rotation, 365 days is a year,
so if I did my calculation correct, your distance is 24.9 million miles relative to 1035 mph. But I edited since to 9089230000 mile which I still have to double check.
365*24902*1000=9089230000 mile
added - yes the new value
v=1035 MPH OR 0.28821759259 MILE /S 0R APPROX 463M/S
Sir, I don't think you're in the right forum thread. What does any of this have to do with traveling at near light speed to another planet?
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I'm sorry, I don't understand your numbers. Were did you get 1035 mph? or 24.9 million miles?
Good question
1035 mph is the speed of the Earth's rotation at the equator, the circumference of the equator is 24,902 miles, and it takes approx 24 hrs for one rotation, 365 days is a year,
I hope that enlightened you.
Form your own judgement on validity!
Edit: ha, did it again. Collision.
The Box regularly gets his posts moved to new theories, and if he keeps interrupting this thread he will find his posts split off.
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1035 mph is the speed of the Earth's rotation at the equator, the circumference of the equator is 24,902 miles, and it takes approx 24 hrs for one rotation, 365 days is a year,
so if I did my calculation correct, your distance is 24.9 million miles relative to 1035 mph. But I edited since to 9089230000 mile which I still have to double check.
365*24902*1000=9089230000 mile
added - yes the new value
v=1035 MPH OR 0.28821759259 MILE /S 0R APPROX 463M/S
Sir, I don't think you're in the right forum thread. What does any of this have to do with traveling at near light speed to another planet?
My apologies, I am unable to discuss this with you any further or talk to you to be social.
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You're going to give me a headache thinking of this stuff!!!
Good why should I be the only one with a headache. LOL
And yes welcome to the forum.
You are using the word observe in 2 different contexts.
Relativity does not allow for the light travelling back from the destination because it is only considering travel time.
Colin glad you found the other thread I mentioned that is still giving me this headache.
I thought the whole point of relativity is the fact that the speed of light has to stay constant for all observers. That was what drove Einstein to think of all this time dilation and length contraction. If nothing can be seen to exceed the speed of light from any reference frame, then time and space have to be seen to change to make sure this remains so. Nowhere in any of that does it actually state that the speed of light can't be exceeded.
In our thousand light year to Volcan trip, relativity as I understand it states that the Earth reference frame will see the ship traveling at a significant number of decimal places after 0.999....% the speed of light so will watch the trip last for a bit over 1000 years. If you want to give me an exact ship travel time, I can and will do the calculations and tell you exactly what speed will be seen by Earth and how long Earth will watch till the ship arrived. I mean that is not hard.
Yet relativity relies for the proof of time dilation on what is seen by the frame watching the ship and what that frame sees. The whole point of the Lorenz transformation is to explain why the Earth frame sees a longer travel time than the ship itself experiences.
Lets remember that the ship itself has to accelerate. From the ship's point of view, if it is capable of sustained 1g acceleration, for every second that goes by after departing Earth orbit, it is going 9.81 metres per second faster than it was the second before. In under one year (353.7 days), it has accelerated to the speed of light relative to the Earth. That does not mean that it hits some sort of barrier that says you will accelerate no more. You can in your own reference frame on the ship keep accelerating and every test you can possibly do will confirm that for every second that goes past you are going 9.81 metres per second faster than you were the second before.
Earth restricted to watching you at the speed that light can carry the information of your position back, will of course see you edging closer to the speed of light, but can never see you traveling at or over light speed. Light can not carry such information. It's not fast enough.
But does it really mean that the ship doesn't travel faster than light? Does it?
I think where this strange thought experiment of mine is taking me, is to the realization that;
Relativity does not actually disallow superluminal travel. It doesn't even make the claim.
What it does claim is that nothing can be "seen" to travel faster than light from any reference frame, by any means available to Electromagnetic information transfer. The rest of your "observed" reality will always adjust to make this so.
That is actually a totally different thing!
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. Nowhere in any of that does it actually state that the speed of light can't be exceeded.
I'm going to open my mouth and probably stick my foot in it.. but here goes anyhow.
There isn't enough energy in the universe to accelerate matter faster than the speed of light. Even a tiny itsy-bitsy particle like an electron would require more energy than what is available in the universe. I'm no mathematician, but isn't this what E=MC2 means?
Trivia: Did you know that even Einstein had to hire a guy to help him with the math?
Here are two things that are very easy to understand and can not be argued with.
1) It takes the ship 1000 (and a bit) years to get there.. 2) It takes the photons that make up the image of the ship at its destination, 1000 years to get back to Earth.
That's 2000 years... no way around that. The one that I had a problem with was understanding the return trip.. but I got that figured out too finally.
I should have taken up music.. so much easier...
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I'm going to open my mouth and probably stick my foot in it.. but here goes anyhow.
There isn't enough energy in the universe to accelerate matter faster than the speed of light. Even a tiny itsy-bitsy particle like an electron would require more energy than what is available in the universe. I'm no mathematician, but isn't this what E=MC2 means?
Sticking our feet in it is part of the fun.
OK let me attack this from a different angle.
If E=Mc² is interpreted to really say that you gain infinite mass at the speed of light, then whatever your method of constant 1g propulsion system is, would also have to be outputting infinite energy as all your propellant has itself gained infinite mass.
It is a mistake to consider that E=Mc² really raises your rest mass at all. Everything past the rest mass is kinetic energy and that is relative to any other observer with a different relative speed to you.
Just remember that every reference frame apart from one's own because of the limited speed of light is distorted in some way.
The only thing that can be stated with any certainty is that every reference frame in the entire universe is unique. No two can ever agree to the N th degree about everything. And that is because we use Electromagnetic Radiation as a means of information transfer. that necessarily means that everything is gaged against the backdrop of the speed of light.
And the speed of light is damn slow...
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Something like this?
[ Invalid Attachment ]
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I'll see if I can put together a diagram with thoughts.
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The only thing that can be stated with any certainty is that every reference frame in the entire universe is unique. No two can ever agree to the N th degree about everything. And that is because we use Electromagnetic Radiation as a means of information transfer. that necessarily means that everything is gaged against the backdrop of the speed of light.
The energy is how we measure relative change in the universe. However, although this tells us many things, this method does not completely deal with the matter of universe. It deals with reference, but not substance. For example, say we had a ship of mass M and we used X energy to accelerate it to a terminal velocity V. Special relativity, in the ship reference, will define changes in time, distance and relativistic mass; proportional to its mass and the energy used to propel it.
From an earth reference, if this ship was heading toward us, or was heading away from us, we will see something different in terms of the light that come off it; blue shift or red shift. Yet, in the ship reference, it does not matter if it is coming or going to the earth. It will not see two different things. It will see one thing in both directions in its own reference.
If we use the twin paradox, the twin on the ship, coming or going to the earth, will age slower, even if the rocket appears to red shift or blue shift, going and coming. They don't cancel in a round trip. In this example, there is a preferred reference; moving twin who used real energy, and not relative observational energy.
This is why Einstein used three terms in Special relativity; time, distance and mass. General Relativity also implies a specific amount of mass density. But there is a tendency to dismiss the mass term, and define everything in terms of space-time, which does not always work. It adds a wrong assumption that does not close the energy balance; tangible energy used.
I have traced the source of this problem to the way we measure time. Time moves spontaneously in one direction, to the future. Time does not cycle, and time does not return to where it began. Yet clocks cycle and return to where they began; 12 midnight. Even atomic clocks use an atomic cycle; vibration/wave. Cycling is what energy does. Cycling is not what time does.
The net affect is we measure/parallel a one directional phenomena; time, with a cyclic tool that better describes energy. We approximate a time line with a sine wave. This may seem trivial, but it leads to conceptual flaws further down the line. A faulty foundation premise is like a rotten beam that supports a house. The bean will crack and the house will sag.
Let me give an analogy, so you can see the potential problems that can and will arise. We can theoretically measure temperature using a hydrometer; used to measure humidity. Temperature is an artifact of atomic and molecular collisions, while humidity is a measure of how much water is in the air. These two things do not express the same phenomena. However, the amount of water in the air, will be fixed for any temperature. If we know the amount of water in the air, we also know the temperature. It only requires a conversion factor which we can build into the hydrometer dial.
Say we alter the pressure in the room, around our hydrometer. More pressure will squeeze water out of the air; condenses into liquid water. Since the amount of water drops, the hydrometer reading will fall and therefore telling us the temperature just fell. However, we don't feel anything different. We conclude there much has been a virtual temperature drop.
On the other hand, if we had a real thermometer, we would notice the temperate did not change. The wrong tool has shown a change. We see something that is not really there, even though hydrometer/thermometer says it is there. After careful thought we figure out that what has changed was the pressure. After running further test we can see that pressure directly impacts the temperature reading, therefore they much be governed by similar things, But conceptually these are two different things. This is what I would see. Yet the assumption will work, if built into the hydrometer, even though it is wrong. If you accept that, the mind is now wandering, due to a conceptual disconnect. This implies there will be no preferred temperature. Temperature all depends on whether we measure on the mountain or sea level. But if we used a proper thermometer, one system works for all. There is preferred temperature, which will be called preposterous.
This is like the space ship that had been propelled, whose reference appears relative to the blue or red shifts; moving toward or away from us on earth. The twin stays younger either way. This is all due to using a tool that is not paralleling the phenomena of time. Time can only go one way and not two ways. That should be a dead giveaway, but is not seem.
Time is more conceptually related to entropy than it is to energy. The second law says the entropy of the universe has to increase, just like time. Both go one way in terms of a spontaneous direct. Energy cycles. plus and minus, which is not what time does. When the clock slows or speeds up we are seeing what sine wave of energy does, not what the arrow of time is doing.
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. Nowhere in any of that does it actually state that the speed of light can't be exceeded.
Not me, I think it was Spaceflow said it.
Here are two things that are very easy to understand and can not be argued with.
1) It takes the ship 1000 (and a bit) years to get there.. 2) It takes the photons that make up the image of the ship at its destination, 1000 years to get back to Earth.
That's 2000 years... no way around that.
This is the problem I have with the scenario. To me it is all in the rest frame of Earth and Volcan, so there is no reason to use time dilation as we are not asking how much the traveller aged during the journey.
I should have taken up music.. so much easier...
Not in my experience. I'm prepping for a music exam at moment and my fingers are sore!
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Something like this?
like the diagram, but i've just realised what you are assuming.
I think yu are applying time dilation to the traveller and assuming he travels the full distance in our frame and so appears to travel FTL. But that is not what happens from his perspective.
He appears stationary, with our frame rushing past at .9xx of c. Just as we see his ship to be length contracted he sees the distance to Volcan to be contracted. So although Volcan moves towards him he completes a shorter journey in a shorter time, he doesn't exceed the speed of light.
I think I mentioned the length contraction in the other post as to why he still measures constant light speed, but hadn't quite clocked how you were using the dilated time.
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Try contemplating the Earth observer sees on the return trip..
The Earth observer sees the spaceship turn to leave and arrive back on earth almost instantly. Like playing a movie in fast forward.
To the observer on Earth, the journey out looks as though it took 2000 years and plays in slow motion.. but the return trip looks like it takes only a few seconds and play out very very fast.
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I think yu are applying time dilation to the traveller and assuming he travels the full distance in our frame and so appears to travel FTL. But that is not what happens from his perspective.
I am applying the apparent time dilation to what the Earth Frame sees looking at the traveler. What I am saying is that the traveler in this scenario does not experience any time dilation within his own frame. Time for him happens normally with any system he uses to measure it. Same as anyone else in the Universe within their own reference frame. The time dilation is only seen from the Earth frame because in this scenario, no matter what speed above light you make the traveler accelerate to, Earth will only see him traveling at the speed that light can communicate the information back. The speed of light. He can never appear to go faster than light. There is no other choice of view no matter how fast he actually really goes.
So from the earth frame to make sense of what they are observing, time and distance have to be seen to distort. It doesn't mean they really distort.
From the traveler's perspective, none of that is true. He just keeps going 9.81 metres per second faster than he was the second before. He is in an accelerated frame not a static one.
But that is not what happens from his perspective.
He appears stationary, with our frame rushing past at .9xx of c. Just as we see his ship to be length contracted he sees the distance to Volcan to be contracted. So although Volcan moves towards him he completes a shorter journey in a shorter time, he doesn't exceed the speed of light.
Wrong he never can consider himself as stationary. He is and measures and understands himself to be in an accelerated frame. He sees Volcan rushing towards him ever faster because he is accelerating towards it. Not because length is contracting. According to his own accelerating frame he completes the journey in less time because he accelerated past the speed of light not because of the visual effects caused by the slower speed of light.
Have another look at the diagram. This view that I am describing gives the same results as relativity for what everyone (Earth, Traveler, and Volcan) see, but like moving around a building can visually foreshorten lines, it is only an illusion of frame of reference perspective. Not reality.
Try contemplating the Earth observer sees on the return trip..
Try and envision what a Volcan observer sees on the first trip.
The traveler leaves from Earth's now, heading for Volcan's now. Earth and traveler can not see where the traveler is going by any means whatsoever, as Volcan's now will not be visible to Earth for 1000 years. Yet that is where the traveler is going.
Volcan at the traveler's departure time has no way of seeing that departure as they can't see Earth's now and will not see it for 1000 years. Yet the traveler is accelerating towards their now.
If we say that the traveler takes 1003 years to complete the journey to volcan, then Volcan will see the journey last for 3 years. and Earth will see the journey last for 2003 years. That is not what relativity is telling us.
As the Earth and Volcan frames are considered co-moving, they have to agree according to relativity on what speed and time applies to the traveler. So lets break this down to what each observes. Volcan has observed the traveler cross 1000 light years in 3 years, where Earth has observed the traveler cross 1000 light years in 2003 years. One would observe him traveling superluminal, while the other would observe him traveling at half the speed of light. Yet relativity is meant to explain the difference in observations from one frame to the other.
None of that gives what the relativity equations state, which is what speed has to be observed and measured to give you the right "γ" (Gamma) to account for observed time dilation and length contraction.
The math doesn't appear to work.
Remember that no matter how it's presented, the only one that can track progress in real time is the traveler.
Both the other reference frames have a distorted view of events.
Earth views the start of the journey in the now frame of the traveler, but has a more and more distorted view as he is traveling to somewhere they can not see for 1000 years. No matter what speed we assign to the traveler, Earth can not observe Volcan at the time of departure until 1000 years have been continually observed. There is no way around that.
Volcan similarly has no way of seeing the traveler start his journey at the Volcan now time that he started it, they in fact have no way of observing this event for 1000 years after it happened.
And the traveler from his perspective leaves Earth now behind and accelerates from Earth's now that Volcan can't see, to Volcan's now that Earth can't see.
He's perspective is the only one that connects all the realities. And according to him, what someone else perceives as light speed, is totally irrelevant. After about 348 days of 1g acceleration he can turn his drive off and consider his frame as static. He may not at this stage be able to even see the Earth as his to him static frame the Earth is receding at almost the speed of light and as such has redshifted to or even past his observational horizon. He is seen Volcan rushing towards him at almost the speed of light and and such blushifted into a continuous gamma ray source. No matter what speed of light caused distortions are apparent to anyone else, he can start his drive again and increase his speed from this to him static frame by his constant 1g acceleration rate.
Earth would definitely redshift out of his observable Universe, and again because of the slowness of light speed bringing the information to him, Volcan will just keep blue-shifting to ever shorter Gamma rays while appearing closer than it is.
Yes he would be seen length contraction forward and length expansion backward.
But being a clever monkey he knows that it is just a visual effect brought about by his speed being higher than what the speed of light can transfer information. As explained during my time learning relativity, his motion is changing the angle through time that he views the Universe.
It in no way changes time or space. Just his angle of observation.
He is observing his view go from Earth now and Volcan 1000 years in his past at the start of the journey, to Volcan now and Earth 1000 years in his past at the end.
Everything else from any observation point other than the traveler's is an illusion brought about by that so horribly slow speed of light.
The lorenz transformations are simply a way to explain why those illusions come about.
If there was such a thing as instantaneous transmission of information, then the distortions of light speed being a constant for all would simply disappear.
Nothing can be seen to travel faster than light when light carries the information of that trip.
That is not the same as nothing can travel faster than light.
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You called up Vulcan on the intergalactic subspace instant communication system and say your pizza is leaving here now.
Vulcan turns their telescope on Earth to watch the departure. They would see nothing for 1000 years. Then, at 1000 years, they would see you depart and it would appear to them as though your ship was traveling much much faster than light. So if your journey was gong to take 1003 years, to Vulcan, it would only look like the trip took just 3 years.
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You called up Vulcan on the intergalactic subspace instant communication system and say your pizza is leaving here now.
Vulcan turns their telescope on Earth to watch the departure. They would see nothing for 1000 years. Then, at 1000 years, they would see you depart and it would appear to them as though your ship was traveling much much faster than light. So if your journey was gong to take 1003 years, to Vulcan, it would only look like the trip took just 3 years.
So how do we reconcile your above statement with the entire principle of relativity coming about just to explain that nothing can from any reference frame be seen to travel faster than light.
With that description you have just destroyed the reason that relativity exists in the first place.
Volcan or any other reference frame in the Universe is not allowed to observe anything traveling faster than light.
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Wrong he never can consider himself as stationary.
But that is the whole point of relativity, that relative to him the earth frame is moving.
He is in his own rest frame and hence experiences his own proper time.
He is and measures and understands himself to be in an accelerated frame. He sees Volcan rushing towards him ever faster because he is accelerating towards it. Not because length is contracting.
Yes he is a clever monkey and knows he has accelerated, so he can make sense of the situation. However, special relativity states that he sees length contraction of the distance to Volcan. If length contraction is a visual illusion then so is time dilation, they have the same source.
Remember that no matter how it's presented, the only one that can track progress in real time is the traveler.
Both the other reference frames have a distorted view of events.
The traveller's view of earth's frame is also distorted.
I can see where you are coming from, but this is not a standard interpretation of SR.
As the traveller approaches light speed the length contraction means the distance he has to travel approaches 0, hence the speed of light limit.
Have a read through this and see what you think and how your theory differs from the usual interpretation. http://galileo.phys.virginia.edu/classes/252/time_dil.html
After you've read it you might still want to develop your theory in New Theories as it is an interesting interpretation.
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The one that I had a problem with was understanding the return trip.. but I got that figured out too finally.
Think about doppler shift, retreating and approaching give different results. As you say, you figured it out a different way.
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Quote from: Space Flow on Today at 12:06:32
Wrong he never can consider himself as stationary.
But that is the whole point of relativity, that relative to him the earth frame is moving.
He is in his own rest frame and hence experiences his own proper time.
Ohh Colin. You are getting your relativities mixed up.
You are thinking in terms of SR and applying it to an accelerated frame.
SR does not apply to an accelerated frame. That is the whole reason that Einstein kept on working to bring relativity so it can be applied to the real world. That after all is what general relativity is all about. Accelerated frames. No while under acceleration the traveler can not consider his frame as being at rest and SR is not enough to explain the situation.
However, special relativity states that he sees length contraction of the distance to Volcan. If length contraction is a visual illusion then so is time dilation, they have the same source.
Again SR can not describe an accelerated frame.
But you are right in your assessment. If length contraction is an illusion than time dilation is also an illusion both brought about by the limited speed of information transfer.
The traveller's view of earth's frame is also distorted.
Yes if this point of view is in any way relevant, than anyone's frame of reference is distorted when viewed from any other frame of reference.
Again because the speed of information flow is limited. That distorts all information about space and time to some degree with any and all movement. Any of those distortions are so small they can and are ignored. But when you approach movement that is close to or faster than the rate that information can be transmitted, weird things start to happen.
I can see where you are coming from, but this is not a standard interpretation of SR.
As the traveller approaches light speed the length contraction means the distance he has to travel approaches 0, hence the speed of light limit.
And yet that is the interpretation from someone in an external reference frame, not the traveler's.
He does dot notice at any point that he has reached the speed of light and so can not accelerate further. In the traveler's reference frame, by doing what the Earth frame claims is close to the speed of light, he can detach an unpowered signal drone that has no propulsion system. This drone will have a rest frame that the Earth will view as traveling close to the speed of light.
The traveler can then keep accelerating till he is doing close to the speed of light relative to that drone. Earth is still seeing both the drone and the traveler moving at close to the speed of light. That is all that the speed of light can show Earth. Yet the traveler who belongs to the reference frame that is actually doing the moving, is still going 9.81 metres per second faster now than he was one second before.
If faster than light travel is actually possible, there is no way for the speed of light to show such a fact. It just has no way to do it.
Having said all that, I don't actually think any of it is true.
I just can't think of a way to fault the thinking.
Have a read through this and see what you think and how your theory differs from the usual interpretation. http://galileo.phys.virginia.edu/classes/252/time_dil.html
After you've read it you might still want to develop your theory in New Theories as it is an interesting interpretation.
I will look at your link. thank you.
And thanks to all concerned for a very stimulating contemplation of Relativity.
Sad to say I don't think we managed to answer the original question posed by this post;
Hi,
Although, I used to be a student of science but there is one thing that still haunts me i.e. Time travel.
I understand that the time is just a unit that as human we introduced which is "he duration of 9 192 631 770 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the caesium 133 atom". I completely accept that this phenomenon can be dependent on a number of environmental variables and other fields which when changed would impact the period and gravity is one of those.
From above I understand that if a person on earth using an atomic clock matched to the other atomic clock with another person in space then eventually the atomic clock in space will slow down in relation to the one on earth hence 81 years on earth could be 80 years in space. Having said that I couldn't understand that is it possible that, if the person on earth takes 81 years to complete something then at the same speed the person in space will complete the same in 80 years? or will it be 81 years in space?
I reckon it should be 80 years in space considering time is relative and 80years in space will be equal to 81 years on earth. Similarly the span that the person has lived will be exactly the same on both sides with the only difference that their measuring scales are acting different because of gravity or may be other reasons.
If my assumption is true than I really fail to visualize the concept of time dilation.
Please help me in understanding this and visualize the time dilation.
In fact me voicing my doubts, may have confused ankur.jain even more.
So in an attempt to make up for that ankur.jain, let me have a go at giving you a way to understand this time dilation thingy.
Visualise for me if you can an x,y coordinate grid.
Let the x axis represent the physical dimension. (Space)
Let the y axis represent the Temporal dimension. (Time)
Now visualise your self as the possessor of a certain amount of velocity. Lets call it 10.
Now that velocity of 10 is a constant. you always possess it no matter what.
So you are sitting at your computer screen reading this. You are not moving at all in the Space dimension (x axis) but you still possess this 10 velocity. On the graph all your movement is in the y axis. You are moving at maximum velocity through time.
Now say you got up, jumped in your car and drove to the shops and back. During that journey, your graph showed some movement in the x axis. maybe you drove really fast so managed a velocity of 1 in the x axis. Your total velocity is still 10. So if 1 has gone to the x axis then only 9 has been travel in the y axis. You have used some of your total velocity to travel through space and as such reduced the amount of travel you did through time.
So lets amp this up a bit. You now jump in an experimental space ship that takes you to pluto and back at half the speed of light. Your graph now shows a diagonal line at 45 degrees. Your total velocity is still 10 but you have now used a lot more of it in the space deimention so you have done even less traveling through time. You are aging a lot slower than when you were just sitting at your desk now.
You get back and they tell you that while you were gone they improved the design amd have now got a ship for you to test that is capable of 99% the speed of light. You jump in to this ship and head off into outer space. Your total velocity is still 10 but the line on your graph is now almost horizontal. you are using 9 of your velocity to travel in the x axis and only 1 in the y.
You are now traveling very fast through space and very slow through time.
That's why it is called Spacetime.
We live in a two dimensional Universe. One dimension of space and one of time. The thing that connects the two is movement. And the ratio of space to time is the definition of speed.
Hope that helps, and sorry for hijacking your post.
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The one that I had a problem with was understanding the return trip.. but I got that figured out too finally.
Think about doppler shift, retreating and approaching give different results. As you say, you figured it out a different way.
There are two distinct things going on. The retreating and approaching of an object are based on the light/energy, emanating from the source, that we use to observe the source. All our instruments measure energy signals. The underlying matter behaves differently from the energy. We will see/measure the light from a flashlight, not the matter of the flashlight. The flashlight does not change, whether the light is on or off. But if the light is off, there is no flashlight to see. But it is still there.
Let me explain this in terms of the twin paradox. We will have a stationary twin who will be observer. The other twin will be put on a rocket, with fuel energy X, which propels him and the rocket to velocity V. The moving twin's velocity does not have to be going in any particular direction, relative to the earth, for hm to age slower. It is all about kinetic energy; velocity. The moving twin will age slower in both directions, since the earth is not an absolute reference.
The observer twin will not directly see the other twin, but will see the light or radio signal, He will first see a red shift in this energy as the other twin moves away from the earth and then a blue shift as the other twin returns toward the earth. The light; red shifted, makes it appears like space-time is expanding as the other twin moves away. Then the light makes it look like space-time is contracted as he returns; blue shifted. This may be true of the energy, as seen from the earth, but it does not reflect what the other twin is actually doing in terms of his matter. He ages slower in both directions.
Let me approach this from another angle. Say we saw a star moving at V, close to the speed of light. It appears to distance contract so it appears to be half its diameter due to relativity.This is true of the light that we use to measure the star. It is not the same in terms of the mass/matter. If it was the same, at half diameter, the volume of the star would physically decrease by 8 times. This means that star should become 8 times denser. Hydrogen at 8 times the density will be a very dense solid metal that not will give off normal plasma emissions. If we see normal atomic hydrogen emissions the star can't be 8 times denser. Only the light that has left the star is contracting, not the actual star. Relative reference only applies to the energy, not the matter. In terms of matter, since we still see atomic emissions not metallic hydrogen emissions,
Let me give another example. Say we have a fog horn that sounds to warn ships. This fog horn produces 10,000 watts of audio power; energy conservation. This amount of energy is fixed based on their electron bill. One speed boat is heading toward the fog horn and due to the doppler shift, he hears a higher pitch; blue shift. Another speed boat is moving away from the fog horn and hears a lower pitch; red shift. Since a tweeter generates high pitches and a woofer generates lower pitches, one boat assumes the fog horn is a tweeter, while the other assumes the fog horn is a woofer. A woofer and tweeter take different amounts of energy to make their sound, with the woofer needing more energy. In the reality, the light houses uses a mid range. Both speed boats will misjudge the source energy.
The amount of actually energy never changes at the fog horn source. This is an absolute based on the electric bill; energy conservation. Whereas both observational references added or subtract source energy based on how the sound waves change in their reference. The fog horn power is absolute, but the speed boats, by using second hand data, energy, that can be massaged by motion, becomes relative. As long as we use energy to measure the universe, we never see the real fog horn.
Say the fog horn was the source of the cosmic microwave background radiation; during the big bang. Depending on our movement in space, relative to that original source, we will see either too much energy or not enough, since we are not measuring the source, but second hand energy that came from the source, that is vulnerable to motion of the observer. The source is a universal standard, while the energy we use to represent it, becomes relative to reference.
The theory that there is no absolute reference in the universe, means the fog horn energy; 10,000 watts, can be disregarded since this cannot exist. This may be true of the reflected light/sound, removed from the source, but it is not true of the source. The fog horn never changes.
I have discussed how we measure time using cyclic phenomena that reflect 5he nature of energy more than time. Time is a line while energy is a sine wave. A sine wave will hit the center line three times each cycle, but the rest of the sine wave misses the line, positive and negative about the line. It sees red shift and blue shift, when the twin ages slower whether we see a red or blue shift. The twin has matter is motion, and we see detached energy moving in space.
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Ohh Colin. You are getting your relativities mixed up.
You are thinking in terms of SR and applying it to an accelerated frame.
SR does not apply to an accelerated frame.
No, I used SR because looking at your calculations I had assumed you had used SR time dilation. Did you use the GR formula for time dilation?
Also, the Lorentz equations do not take account of acceleration because they do not consider the history of how a certain speed was reached, they depend only on the current speed and are therefore applicable to accelerating frames.
Just as we look at the traveller's frame and apply time dilation, we also apply length contraction to the distance he will travel. So at current speed he will complete the journey in the dilated time.
Although you are adding a complication by having variable speed over the journey, you could calculate the effect by integrating.
As your acceleration is constant, there is no additional time dilation due to differential gravity fields so I can't see any additional GR effect. If you are considering time dilation due to the g difference between weightless and 1g, it is not large enough to be significant.
Although GR deals with accelerated frames, nothing in GR overturns SR, it just extends it to gravitational fields.