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On July 23 2011 04:52 Diks wrote:+ Show Spoiler +On July 23 2011 03:51 Nawyria wrote:Show nested quote +On July 23 2011 02:29 Diks wrote:
I want to complicate the OP a bit and let's imagine we have a theorical instantaneous conversation with the twins (This is not physically possible, this is just a brain fuck scenario).
They will talk like instant telepathy during the travel time.
The perception of time for the traveling twin will be different on the way back to earth. Time will feel like it goes slower for him, he'll feel like an hour last a bit longer and when his twin on earth will instantaneously talk to him, he'll feel like his twin is talking slower than usual. When he'll land to earth, there won't be any weird moment of "how can you be there ? You told me 1 minute ago that you were coming back in 2 years"
The key is not the mesure of time, but the perception. I bet clock will feel like turning slower in a fast space travel.
I'm curious but seriously lack of physical education on the subject, can anyone help clarify this ? The question I ask you then, is instantaneous to whose eyes? A big part of the Theory of Special Relativity is that simultaneity is in the eye of the beholder. Two events that occur simultaneous to you, may not occur simultaneous to me. Since all inertial systems are equal (this a fundamental postulate), there is no system we can point to and say "This observer has the correct notion of simultaneous". The only way we can work our way around this is to say "The signal travels instantaneously according to my perception of time". However, this generates an unresolvable paradox as below: Paradox+ Show Spoiler [picture] +1) Twin A sends Twin B an instantaneous question according to his perception of simultaneous. 2) Twin B sends Twin A an instantaneous answer according to his perception of simultaneous. 3) Twin A receives Twin B's answer before he ever asked the question. Thank you for your enlightment, I know realise my question didn't really make sens. I have something that still tickle me about "two events that occur simultaneous to you, may not occur simultaneous to me." So if I get this right; time and space are undissociable.
Time and space are not fixed quantities, but they represent "choices of axes" in what we call space-time. Within space-time, we can dissociate between three distinct regions, the timelike, the lightlike and the spacelike regions.
To understand this, consider the picture below:
+ Show Spoiler [picture 1] +
I've drawn 3 sets of space-time axes and the paths of 2 light signals that all pass through the same origin. As relative speeds get closer and closer to the speed of light, you can see that the space and time axes "bend towards" the rightbound light signal. However, since nothing that has any mass can go at the speed of light, the time-axis will always lie above this signal and the space-axis will always lie below this signal.
+ Show Spoiler [picture 2] +
This brings me to the subdivision mentioned earlier:
1) Timelike: the points of the lightcone that could be occupied by the time-axis of an observer passing through the same origin. Incidentally, these are the points in space-time that will ever be able to send a message to or receive a message from the origin through means of communication slower than the speed of light.
2) Lightlike: the points of the lightcone that could be occupied by any light signal passing through the same origin. Incidentally, these are the points in space-time that will ever be able to send a message to or receive a message from the origin through means of communication at the speed of light.
3) Spacelike: the points of the lightcone that could be occupied by the space-axis of an observer passing through the same origin. Incidentally, these are the points in space-time that will never be able to send a message to or receive a message from the origin.
I hope this clarifies it a bit.
When I see the mathematics model, the time/location is always refered as a dot, but we, human have a body that covers an area. Can I legitimately say that my right leg lives in the past and my left leg in the future ? (even by fractions of ns)
Do we have some sort of "center of the time/space perception" inside our brain ?
I'm sorry for my questions that may have no sense one again :/
Techically speaking, we would have to describe our body as the collection of molecules, the dealings of which are guided by chemical interactions and mechanical interactions. But then molecules are made out of atoms, atoms are made out of electrons and a nucleus of protons and neutrons. But then protons and neutrons are nothing but their constituent confined quarks, but these are delocalised and hard to measure and.. WWWAAAGGGHHHH. Things get very, very complicated when we try to describe objects that consist of large amounts of smaller objects to the point where it is very impractical to even use computers to attempt to simulate this.
However, there is a whole field of study dedicated to doing exactly this: namely Thermal Physics, which can be used to model, say, a balloon. However, the methods we use do their utmost best to avoid having to describe the balloon as the collection of molecules inside the balloon, but instead we talk about larger so-called "macroscopic" properties such as temperature, pressure, volume etcetera.
In practice, we generally approach describing complex objects as (in order of increasing complexity)
- A point-like object in space.
- Several point-like objects at the same position.
- A volume or surface at a point in space with a number of properties
- A continuum
- A large collection of point-like objects
As for the leg-question, the notion of "living in the past" is a bit vacuous in relativity. Technically speaking though, if you've swung your right leg more often than your left leg then it is younger by an immeasurably minute amount. However, remember that no single atom you had in your body when your were born is in your body right now; and no atom you have in your body right now is likely to be there in a decade. This raises the interesting philosophical questions of "How is a 'leg' defined?" and "How is my 'body' defined?", but these fall outside of the purview of physics I'm afraid.
As for the brain part. I suppose the way it works is that our brains receive information through the nervous system and than processes this is some way that allows you to perceive what you perceive. Exactly how the brain processes this information and deals with concepts such as space and time are big, BIG unanswered questions in neurology. If only we knew...
Keep the questions coming!
Edit: missed a part of your question.
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On July 23 2011 05:30 Nawyria wrote:Show nested quote +On July 23 2011 04:52 Diks wrote:+ Show Spoiler +On July 23 2011 03:51 Nawyria wrote:Show nested quote +On July 23 2011 02:29 Diks wrote:
I want to complicate the OP a bit and let's imagine we have a theorical instantaneous conversation with the twins (This is not physically possible, this is just a brain fuck scenario).
They will talk like instant telepathy during the travel time.
The perception of time for the traveling twin will be different on the way back to earth. Time will feel like it goes slower for him, he'll feel like an hour last a bit longer and when his twin on earth will instantaneously talk to him, he'll feel like his twin is talking slower than usual. When he'll land to earth, there won't be any weird moment of "how can you be there ? You told me 1 minute ago that you were coming back in 2 years"
The key is not the mesure of time, but the perception. I bet clock will feel like turning slower in a fast space travel.
I'm curious but seriously lack of physical education on the subject, can anyone help clarify this ? The question I ask you then, is instantaneous to whose eyes? A big part of the Theory of Special Relativity is that simultaneity is in the eye of the beholder. Two events that occur simultaneous to you, may not occur simultaneous to me. Since all inertial systems are equal (this a fundamental postulate), there is no system we can point to and say "This observer has the correct notion of simultaneous". The only way we can work our way around this is to say "The signal travels instantaneously according to my perception of time". However, this generates an unresolvable paradox as below: Paradox+ Show Spoiler [picture] +1) Twin A sends Twin B an instantaneous question according to his perception of simultaneous. 2) Twin B sends Twin A an instantaneous answer according to his perception of simultaneous. 3) Twin A receives Twin B's answer before he ever asked the question. Thank you for your enlightment, I know realise my question didn't really make sens. I have something that still tickle me about "two events that occur simultaneous to you, may not occur simultaneous to me." So if I get this right; time and space are undissociable. Time and space are not fixed quantities, but they represent "choices of axes" in what we call space-time. Within space-time, we can dissociate between three distinct regions, the timelike, the lightlike and the spacelike regions. To understand this, consider the picture below: + Show Spoiler [picture 1] +I've drawn 3 sets of space-time axes and the paths of 2 light signals that all pass through the same origin. As relative speeds get closer and closer to the speed of light, you can see that the space and time axes "bend towards" the rightbound light signal. However, since nothing that has any mass can go at the speed of light, the time-axis will always lie above this signal and the space-axis will always lie below this signal. + Show Spoiler [picture 2] +This brings me to the subdivision mentioned earlier: 1) Timelike: the points of the lightcone that could be occupied by the time-axis of an observer passing through the same origin. Incidentally, these are the points in space-time that will ever be able to send a message to or receive a message from the origin through means of communication slower than the speed of light. 2) Lightlike: the points of the lightcone that could be occupied by any light signal passing through the same origin. Incidentally, these are the points in space-time that will ever be able to send a message to or receive a message from the origin through means of communication at the speed of light. 3) Spacelike: the points of the lightcone that could be occupied by the space-axis of an observer passing through the same origin. Incidentally, these are the points in space-time that will never be able to send a message to or receive a message from the origin. I hope this clarifies it a bit. Show nested quote +When I see the mathematics model, the time/location is always refered as a dot, but we, human have a body that covers an area. Can I legitimately say that my right leg lives in the past and my left leg in the future ? (even by fractions of ns)
Do we have some sort of "center of the time/space perception" inside our brain ?
I'm sorry for my questions that may have no sense one again :/ Techically speaking, we would have to describe our body as the collection of molecules, the dealings of which are guided by chemical interactions and mechanical interactions. But then molecules are made out of atoms, atoms are made out of electrons and a nucleus of protons and neutrons. But then protons and neutrons are nothing but their constituent confined quarks, but these are delocalised and hard to measure and.. WWWAAAGGGHHHH. Things get very, very complicated when we try to describe objects that consist of large amounts of smaller objects to the point where it is very impractical to even use computers to attempt to simulate this. However, there is a whole field of study dedicated to doing exactly this: namely Thermal Physics, which can be used to model, say, a balloon. However, the methods we use do their utmost best to avoid having to describe the balloon as the collection of molecules inside the balloon, but instead we talk about larger so-called "macroscopic" properties such as temperature, pressure, volume etcetera. In practice, we generally approach describing complex objects as (in order of increasing complexity) - A point-like object in space.
- Several point-like objects at the same position.
- A volume or surface at a point in space with a number of properties
- A continuum
- A large collection of point-like objects
As for the leg-question, the notion of "living in the past" is a bit vacuous in relativity. Technically speaking though, if you've swung your right leg more often than your left leg then it is younger by an immeasurably minute amount. However, remember that no single atom you had in your body when your were born is in your body right now; and no atom you have in your body right now is likely to be there in a decade. This raises the interesting philosophical questions of "How is a 'leg' defined?" and "How is my 'body' defined?", but these fall outside of the purview of physics I'm afraid. As for the brain part. I suppose the way it works is that our brains receive information through the nervous system and than processes this is some way that allows you to perceive what you perceive. Exactly how the brain processes this information and deals with concepts such as space and time are big, BIG unanswered questions in neurology. If only we knew... Keep the questions coming! Edit: missed a part of your question.
Wow, thank you, you are amazing.
I was about to talk about an imaginary giant so big that the distance between his 2 eyes would be the distance earth-sun.
The giant would be spinning and traveling at near lightspeed. I would be curious to know how his brain could process 2 very distinct timelines.
What I'm curious is that what could be observed in small scale should apply in larger scale.
So the giant traveling at light speed is just an exageration of a human standing on the moving earth. This is not solvable yet I guess.
I don't see how we can possibly pretend to be in a space/time moment when our body actually are in an near infinite space-time moments. I guess we should have at least one molecule that we refere to be the center of perception or that our brain accept some sort of tolerance in what he assume to be the present (as we are pretty small and all our body travel at same velocity, so the reference could agree to have this 1/1000000 margin of error) in wich case the flying giant could not exist.
I've always been passionated by those subjects and I regret to not have continue my studies in physics.
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Blazinghand
United States25552 Posts
On July 23 2011 05:52 Diks wrote:Show nested quote +On July 23 2011 05:30 Nawyria wrote:On July 23 2011 04:52 Diks wrote:+ Show Spoiler +On July 23 2011 03:51 Nawyria wrote:Show nested quote +On July 23 2011 02:29 Diks wrote:
I want to complicate the OP a bit and let's imagine we have a theorical instantaneous conversation with the twins (This is not physically possible, this is just a brain fuck scenario).
They will talk like instant telepathy during the travel time.
The perception of time for the traveling twin will be different on the way back to earth. Time will feel like it goes slower for him, he'll feel like an hour last a bit longer and when his twin on earth will instantaneously talk to him, he'll feel like his twin is talking slower than usual. When he'll land to earth, there won't be any weird moment of "how can you be there ? You told me 1 minute ago that you were coming back in 2 years"
The key is not the mesure of time, but the perception. I bet clock will feel like turning slower in a fast space travel.
I'm curious but seriously lack of physical education on the subject, can anyone help clarify this ? The question I ask you then, is instantaneous to whose eyes? A big part of the Theory of Special Relativity is that simultaneity is in the eye of the beholder. Two events that occur simultaneous to you, may not occur simultaneous to me. Since all inertial systems are equal (this a fundamental postulate), there is no system we can point to and say "This observer has the correct notion of simultaneous". The only way we can work our way around this is to say "The signal travels instantaneously according to my perception of time". However, this generates an unresolvable paradox as below: Paradox+ Show Spoiler [picture] +1) Twin A sends Twin B an instantaneous question according to his perception of simultaneous. 2) Twin B sends Twin A an instantaneous answer according to his perception of simultaneous. 3) Twin A receives Twin B's answer before he ever asked the question. Thank you for your enlightment, I know realise my question didn't really make sens. I have something that still tickle me about "two events that occur simultaneous to you, may not occur simultaneous to me." So if I get this right; time and space are undissociable. Time and space are not fixed quantities, but they represent "choices of axes" in what we call space-time. Within space-time, we can dissociate between three distinct regions, the timelike, the lightlike and the spacelike regions. To understand this, consider the picture below: + Show Spoiler [picture 1] +I've drawn 3 sets of space-time axes and the paths of 2 light signals that all pass through the same origin. As relative speeds get closer and closer to the speed of light, you can see that the space and time axes "bend towards" the rightbound light signal. However, since nothing that has any mass can go at the speed of light, the time-axis will always lie above this signal and the space-axis will always lie below this signal. + Show Spoiler [picture 2] +This brings me to the subdivision mentioned earlier: 1) Timelike: the points of the lightcone that could be occupied by the time-axis of an observer passing through the same origin. Incidentally, these are the points in space-time that will ever be able to send a message to or receive a message from the origin through means of communication slower than the speed of light. 2) Lightlike: the points of the lightcone that could be occupied by any light signal passing through the same origin. Incidentally, these are the points in space-time that will ever be able to send a message to or receive a message from the origin through means of communication at the speed of light. 3) Spacelike: the points of the lightcone that could be occupied by the space-axis of an observer passing through the same origin. Incidentally, these are the points in space-time that will never be able to send a message to or receive a message from the origin. I hope this clarifies it a bit. When I see the mathematics model, the time/location is always refered as a dot, but we, human have a body that covers an area. Can I legitimately say that my right leg lives in the past and my left leg in the future ? (even by fractions of ns)
Do we have some sort of "center of the time/space perception" inside our brain ?
I'm sorry for my questions that may have no sense one again :/ Techically speaking, we would have to describe our body as the collection of molecules, the dealings of which are guided by chemical interactions and mechanical interactions. But then molecules are made out of atoms, atoms are made out of electrons and a nucleus of protons and neutrons. But then protons and neutrons are nothing but their constituent confined quarks, but these are delocalised and hard to measure and.. WWWAAAGGGHHHH. Things get very, very complicated when we try to describe objects that consist of large amounts of smaller objects to the point where it is very impractical to even use computers to attempt to simulate this. However, there is a whole field of study dedicated to doing exactly this: namely Thermal Physics, which can be used to model, say, a balloon. However, the methods we use do their utmost best to avoid having to describe the balloon as the collection of molecules inside the balloon, but instead we talk about larger so-called "macroscopic" properties such as temperature, pressure, volume etcetera. In practice, we generally approach describing complex objects as (in order of increasing complexity) - A point-like object in space.
- Several point-like objects at the same position.
- A volume or surface at a point in space with a number of properties
- A continuum
- A large collection of point-like objects
As for the leg-question, the notion of "living in the past" is a bit vacuous in relativity. Technically speaking though, if you've swung your right leg more often than your left leg then it is younger by an immeasurably minute amount. However, remember that no single atom you had in your body when your were born is in your body right now; and no atom you have in your body right now is likely to be there in a decade. This raises the interesting philosophical questions of "How is a 'leg' defined?" and "How is my 'body' defined?", but these fall outside of the purview of physics I'm afraid. As for the brain part. I suppose the way it works is that our brains receive information through the nervous system and than processes this is some way that allows you to perceive what you perceive. Exactly how the brain processes this information and deals with concepts such as space and time are big, BIG unanswered questions in neurology. If only we knew... Keep the questions coming! Edit: missed a part of your question. Wow, thank you, you are amazing. I was about to talk about an imaginary giant so big that the distance between his 2 eyes would the distance earth-sun. The giant would be spinning and traveling at near lightspeed. I would be curious to know how his brain could process 2 very distinct timelines. What I'm curious is that what could be observed in small scale should apply in larger scale. So the giant traveling at light speed is just an exageration of a human standing on the moving earth. This is not solvable yet I guess. I don't see how we can possibly pretend to be in a space/time moment when our body actually are in an near infinite space-time moments. I guess we should have at least one molecule that we refere to be the center of perception or that our brain accept some sort of tolerance in what he assume to be the present (as we are pretty small and all our body travel at same velocity, so the reference could agree to have this 1/1000000 margin of error) in wich case the flying giant could not exist. I've always been passionated by those subjects and I regret to not have continue my studies in physics.
The giant's brain would be effected by having parts of it moving at light speed and parts of it not moving at light speed; the physical layout of the brain and the dendrites connecting the nerves, along with the speed and direction of the impulses, would all be negative factors for brain function at varying near-light speeds.
His glial cells that were closer or further from the axis of rotation would feed the neurons at different rates, killing them through starvation or flooding them with nutrients. He would die almost immediately, and would have next to no brain function while alive due to the inability of parts of his brain in different reference frames to communicate with each other.
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On July 23 2011 05:55 Blazinghand wrote:Show nested quote +On July 23 2011 05:52 Diks wrote:On July 23 2011 05:30 Nawyria wrote:On July 23 2011 04:52 Diks wrote:+ Show Spoiler +On July 23 2011 03:51 Nawyria wrote:Show nested quote +On July 23 2011 02:29 Diks wrote:
I want to complicate the OP a bit and let's imagine we have a theorical instantaneous conversation with the twins (This is not physically possible, this is just a brain fuck scenario).
They will talk like instant telepathy during the travel time.
The perception of time for the traveling twin will be different on the way back to earth. Time will feel like it goes slower for him, he'll feel like an hour last a bit longer and when his twin on earth will instantaneously talk to him, he'll feel like his twin is talking slower than usual. When he'll land to earth, there won't be any weird moment of "how can you be there ? You told me 1 minute ago that you were coming back in 2 years"
The key is not the mesure of time, but the perception. I bet clock will feel like turning slower in a fast space travel.
I'm curious but seriously lack of physical education on the subject, can anyone help clarify this ? The question I ask you then, is instantaneous to whose eyes? A big part of the Theory of Special Relativity is that simultaneity is in the eye of the beholder. Two events that occur simultaneous to you, may not occur simultaneous to me. Since all inertial systems are equal (this a fundamental postulate), there is no system we can point to and say "This observer has the correct notion of simultaneous". The only way we can work our way around this is to say "The signal travels instantaneously according to my perception of time". However, this generates an unresolvable paradox as below: Paradox+ Show Spoiler [picture] +1) Twin A sends Twin B an instantaneous question according to his perception of simultaneous. 2) Twin B sends Twin A an instantaneous answer according to his perception of simultaneous. 3) Twin A receives Twin B's answer before he ever asked the question. Thank you for your enlightment, I know realise my question didn't really make sens. I have something that still tickle me about "two events that occur simultaneous to you, may not occur simultaneous to me." So if I get this right; time and space are undissociable. Time and space are not fixed quantities, but they represent "choices of axes" in what we call space-time. Within space-time, we can dissociate between three distinct regions, the timelike, the lightlike and the spacelike regions. To understand this, consider the picture below: + Show Spoiler [picture 1] +I've drawn 3 sets of space-time axes and the paths of 2 light signals that all pass through the same origin. As relative speeds get closer and closer to the speed of light, you can see that the space and time axes "bend towards" the rightbound light signal. However, since nothing that has any mass can go at the speed of light, the time-axis will always lie above this signal and the space-axis will always lie below this signal. + Show Spoiler [picture 2] +This brings me to the subdivision mentioned earlier: 1) Timelike: the points of the lightcone that could be occupied by the time-axis of an observer passing through the same origin. Incidentally, these are the points in space-time that will ever be able to send a message to or receive a message from the origin through means of communication slower than the speed of light. 2) Lightlike: the points of the lightcone that could be occupied by any light signal passing through the same origin. Incidentally, these are the points in space-time that will ever be able to send a message to or receive a message from the origin through means of communication at the speed of light. 3) Spacelike: the points of the lightcone that could be occupied by the space-axis of an observer passing through the same origin. Incidentally, these are the points in space-time that will never be able to send a message to or receive a message from the origin. I hope this clarifies it a bit. When I see the mathematics model, the time/location is always refered as a dot, but we, human have a body that covers an area. Can I legitimately say that my right leg lives in the past and my left leg in the future ? (even by fractions of ns)
Do we have some sort of "center of the time/space perception" inside our brain ?
I'm sorry for my questions that may have no sense one again :/ Techically speaking, we would have to describe our body as the collection of molecules, the dealings of which are guided by chemical interactions and mechanical interactions. But then molecules are made out of atoms, atoms are made out of electrons and a nucleus of protons and neutrons. But then protons and neutrons are nothing but their constituent confined quarks, but these are delocalised and hard to measure and.. WWWAAAGGGHHHH. Things get very, very complicated when we try to describe objects that consist of large amounts of smaller objects to the point where it is very impractical to even use computers to attempt to simulate this. However, there is a whole field of study dedicated to doing exactly this: namely Thermal Physics, which can be used to model, say, a balloon. However, the methods we use do their utmost best to avoid having to describe the balloon as the collection of molecules inside the balloon, but instead we talk about larger so-called "macroscopic" properties such as temperature, pressure, volume etcetera. In practice, we generally approach describing complex objects as (in order of increasing complexity) - A point-like object in space.
- Several point-like objects at the same position.
- A volume or surface at a point in space with a number of properties
- A continuum
- A large collection of point-like objects
As for the leg-question, the notion of "living in the past" is a bit vacuous in relativity. Technically speaking though, if you've swung your right leg more often than your left leg then it is younger by an immeasurably minute amount. However, remember that no single atom you had in your body when your were born is in your body right now; and no atom you have in your body right now is likely to be there in a decade. This raises the interesting philosophical questions of "How is a 'leg' defined?" and "How is my 'body' defined?", but these fall outside of the purview of physics I'm afraid. As for the brain part. I suppose the way it works is that our brains receive information through the nervous system and than processes this is some way that allows you to perceive what you perceive. Exactly how the brain processes this information and deals with concepts such as space and time are big, BIG unanswered questions in neurology. If only we knew... Keep the questions coming! Edit: missed a part of your question. Wow, thank you, you are amazing. I was about to talk about an imaginary giant so big that the distance between his 2 eyes would the distance earth-sun. The giant would be spinning and traveling at near lightspeed. I would be curious to know how his brain could process 2 very distinct timelines. What I'm curious is that what could be observed in small scale should apply in larger scale. So the giant traveling at light speed is just an exageration of a human standing on the moving earth. This is not solvable yet I guess. I don't see how we can possibly pretend to be in a space/time moment when our body actually are in an near infinite space-time moments. I guess we should have at least one molecule that we refere to be the center of perception or that our brain accept some sort of tolerance in what he assume to be the present (as we are pretty small and all our body travel at same velocity, so the reference could agree to have this 1/1000000 margin of error) in wich case the flying giant could not exist. I've always been passionated by those subjects and I regret to not have continue my studies in physics. The giant's brain would be effected by having parts of it moving at light speed and parts of it not moving at light speed; the physical layout of the brain and the dendrites connecting the nerves, along with the speed and direction of the impulses, would all be negative factors for brain function at varying near-light speeds. His glial cells that were closer or further from the axis of rotation would feed the neurons at different rates, killing them through starvation or flooding them with nutrients. He would die almost immediately, and would have next to no brain function while alive due to the inability of parts of his brain in different reference frames to communicate with each other.
Shit, I just killed the giant :/
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Blazinghand
United States25552 Posts
On July 23 2011 06:02 Diks wrote:Show nested quote +On July 23 2011 05:55 Blazinghand wrote:On July 23 2011 05:52 Diks wrote:On July 23 2011 05:30 Nawyria wrote:On July 23 2011 04:52 Diks wrote:+ Show Spoiler +On July 23 2011 03:51 Nawyria wrote:Show nested quote +On July 23 2011 02:29 Diks wrote:
I want to complicate the OP a bit and let's imagine we have a theorical instantaneous conversation with the twins (This is not physically possible, this is just a brain fuck scenario).
They will talk like instant telepathy during the travel time.
The perception of time for the traveling twin will be different on the way back to earth. Time will feel like it goes slower for him, he'll feel like an hour last a bit longer and when his twin on earth will instantaneously talk to him, he'll feel like his twin is talking slower than usual. When he'll land to earth, there won't be any weird moment of "how can you be there ? You told me 1 minute ago that you were coming back in 2 years"
The key is not the mesure of time, but the perception. I bet clock will feel like turning slower in a fast space travel.
I'm curious but seriously lack of physical education on the subject, can anyone help clarify this ? The question I ask you then, is instantaneous to whose eyes? A big part of the Theory of Special Relativity is that simultaneity is in the eye of the beholder. Two events that occur simultaneous to you, may not occur simultaneous to me. Since all inertial systems are equal (this a fundamental postulate), there is no system we can point to and say "This observer has the correct notion of simultaneous". The only way we can work our way around this is to say "The signal travels instantaneously according to my perception of time". However, this generates an unresolvable paradox as below: Paradox+ Show Spoiler [picture] +1) Twin A sends Twin B an instantaneous question according to his perception of simultaneous. 2) Twin B sends Twin A an instantaneous answer according to his perception of simultaneous. 3) Twin A receives Twin B's answer before he ever asked the question. Thank you for your enlightment, I know realise my question didn't really make sens. I have something that still tickle me about "two events that occur simultaneous to you, may not occur simultaneous to me." So if I get this right; time and space are undissociable. Time and space are not fixed quantities, but they represent "choices of axes" in what we call space-time. Within space-time, we can dissociate between three distinct regions, the timelike, the lightlike and the spacelike regions. To understand this, consider the picture below: + Show Spoiler [picture 1] +I've drawn 3 sets of space-time axes and the paths of 2 light signals that all pass through the same origin. As relative speeds get closer and closer to the speed of light, you can see that the space and time axes "bend towards" the rightbound light signal. However, since nothing that has any mass can go at the speed of light, the time-axis will always lie above this signal and the space-axis will always lie below this signal. + Show Spoiler [picture 2] +This brings me to the subdivision mentioned earlier: 1) Timelike: the points of the lightcone that could be occupied by the time-axis of an observer passing through the same origin. Incidentally, these are the points in space-time that will ever be able to send a message to or receive a message from the origin through means of communication slower than the speed of light. 2) Lightlike: the points of the lightcone that could be occupied by any light signal passing through the same origin. Incidentally, these are the points in space-time that will ever be able to send a message to or receive a message from the origin through means of communication at the speed of light. 3) Spacelike: the points of the lightcone that could be occupied by the space-axis of an observer passing through the same origin. Incidentally, these are the points in space-time that will never be able to send a message to or receive a message from the origin. I hope this clarifies it a bit. When I see the mathematics model, the time/location is always refered as a dot, but we, human have a body that covers an area. Can I legitimately say that my right leg lives in the past and my left leg in the future ? (even by fractions of ns)
Do we have some sort of "center of the time/space perception" inside our brain ?
I'm sorry for my questions that may have no sense one again :/ Techically speaking, we would have to describe our body as the collection of molecules, the dealings of which are guided by chemical interactions and mechanical interactions. But then molecules are made out of atoms, atoms are made out of electrons and a nucleus of protons and neutrons. But then protons and neutrons are nothing but their constituent confined quarks, but these are delocalised and hard to measure and.. WWWAAAGGGHHHH. Things get very, very complicated when we try to describe objects that consist of large amounts of smaller objects to the point where it is very impractical to even use computers to attempt to simulate this. However, there is a whole field of study dedicated to doing exactly this: namely Thermal Physics, which can be used to model, say, a balloon. However, the methods we use do their utmost best to avoid having to describe the balloon as the collection of molecules inside the balloon, but instead we talk about larger so-called "macroscopic" properties such as temperature, pressure, volume etcetera. In practice, we generally approach describing complex objects as (in order of increasing complexity) - A point-like object in space.
- Several point-like objects at the same position.
- A volume or surface at a point in space with a number of properties
- A continuum
- A large collection of point-like objects
As for the leg-question, the notion of "living in the past" is a bit vacuous in relativity. Technically speaking though, if you've swung your right leg more often than your left leg then it is younger by an immeasurably minute amount. However, remember that no single atom you had in your body when your were born is in your body right now; and no atom you have in your body right now is likely to be there in a decade. This raises the interesting philosophical questions of "How is a 'leg' defined?" and "How is my 'body' defined?", but these fall outside of the purview of physics I'm afraid. As for the brain part. I suppose the way it works is that our brains receive information through the nervous system and than processes this is some way that allows you to perceive what you perceive. Exactly how the brain processes this information and deals with concepts such as space and time are big, BIG unanswered questions in neurology. If only we knew... Keep the questions coming! Edit: missed a part of your question. Wow, thank you, you are amazing. I was about to talk about an imaginary giant so big that the distance between his 2 eyes would the distance earth-sun. The giant would be spinning and traveling at near lightspeed. I would be curious to know how his brain could process 2 very distinct timelines. What I'm curious is that what could be observed in small scale should apply in larger scale. So the giant traveling at light speed is just an exageration of a human standing on the moving earth. This is not solvable yet I guess. I don't see how we can possibly pretend to be in a space/time moment when our body actually are in an near infinite space-time moments. I guess we should have at least one molecule that we refere to be the center of perception or that our brain accept some sort of tolerance in what he assume to be the present (as we are pretty small and all our body travel at same velocity, so the reference could agree to have this 1/1000000 margin of error) in wich case the flying giant could not exist. I've always been passionated by those subjects and I regret to not have continue my studies in physics. The giant's brain would be effected by having parts of it moving at light speed and parts of it not moving at light speed; the physical layout of the brain and the dendrites connecting the nerves, along with the speed and direction of the impulses, would all be negative factors for brain function at varying near-light speeds. His glial cells that were closer or further from the axis of rotation would feed the neurons at different rates, killing them through starvation or flooding them with nutrients. He would die almost immediately, and would have next to no brain function while alive due to the inability of parts of his brain in different reference frames to communicate with each other. Shit, I just killed the giant :/
Dude, he was a one of a kind, how could you ((
but yeah the main thing is that the communication between the eyes and the brain is not instantaneous, it works just like, say, 2 radio operators with radios moving and relativistic speed would.
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Dude, he was a one of a kind, how could you (( but yeah the main thing is that the communication between the eyes and the brain is not instantaneous, it works just like, say, 2 radio operators with radios moving and relativistic speed would.
That is to say, not very good ^^
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On July 22 2011 00:49 Jombozeus wrote:
Well, your signal would take a near-infinite amount of time to reach your twin if hes traveling at near the speed of light.
In other words, its probably just not going to reach him within his lifetime after 2 days if hes traveling at 99% speed of light. Just do the math.
what the hell are you talking about?
traveling at the speed of light in one direction does not mean that light coming from you travelling in the opposite direction essentially stops, thats just insane thinking, how did you manage that? thats like saying multiple galaxys out there should be doing this sort of thing since there are some that move at almost the speed of light.
i dont know why anybody thinks that travelling faster than the speed of light would slow time down, the speed of light is just a speed limit placed on the universe, it has no other affect on it. it may not even be a limit, and if it wasnt, most of our physics/science up till this point will need a total rethink.
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Thinking that what happen in small scale apply in large scale is quite stupid from my part.
The scale matters a lot as the proportional relativity changes from the unvariable constants like lightspeed.
The size of a living body is determined by those unvariable composants and there may be a size-cap for a living being.
If we take into account that what we see is past (because of light+nerves travel speed).
All our thoughts and perceptions take time to travel through our body at different length and speedrate.
But yet, we account that multiple past time lines to be our present and the present, a very close future.
From thoses asomptions, a very small being like a fly would live closer to the actual present he's in than us (due to his size and scale compared to the constants like nerves and light speed.)
if you wondered why you never able to catch flies, I guess we have our answer !
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On July 23 2011 04:55 Nawyria wrote:Show nested quote +On July 23 2011 04:23 Trainrunnef wrote:
Question...
Why would one twin hear the communication of the other as slowed. Wouldn't there just be a delay in the communication due to the time it took for the light to reach twin a/b.
IIRC the speed of light is constant, and redshift/blueshift is due to an accelleration either towards or away from the reciever of the signal.
So with this in mind the communications would be heard by both twins with a normal speech pattern just a long pause. This is partly because of time dilatation. That is to say, when the two twins travel away from each other they observe each other's clocks as running slower; when the two twins travel towards each other, they observe each other's clocks as running faster. This is because our notion of what space and time shifts as the speed between two inertial frames becomes of order c. Another way to think about it is this: If I'm travelling at some reasonable fraction of the speed of light away from you (say, 50%) and I say a sentence to you that takes me 10 seconds to say, then by the time I've finished speaking I'll be 5 lightseconds further away from you relative to where I was when I started speaking and the end of the message will take 5 seconds longer to reach you than the start of the message. This means that you'll receive my original 10-second message smeared out over 15 seconds and thus I'll appear to be talking in slow-motion.
This is kind of a funky way of saying this. The direction of travel isn't relevant to a discussion of time dilation, but is relevant to the waveshift. To be precise, I mean to say that when A is traveling towards B, B is aware of A's velocity. While B may observe A's clock to read a difference of 1.1 seconds after one second of travel, he is aware that A is moving towards him and that the light has originated at a distance that is closer by some non-trivial amount. Because B and A are both aware of time dilation and they know their relative velocities, B will still deduce that A's clock is moving more slowly than B's, and A will still deduce B's clock to be moving more slowly than B's. Correct?
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On July 23 2011 06:20 CptCutter wrote:Show nested quote +On July 22 2011 00:49 Jombozeus wrote:
Well, your signal would take a near-infinite amount of time to reach your twin if hes traveling at near the speed of light.
In other words, its probably just not going to reach him within his lifetime after 2 days if hes traveling at 99% speed of light. Just do the math. what the hell are you talking about? traveling at the speed of light in one direction does not mean that light coming from you travelling in the opposite direction essentially stops, thats just insane thinking, how did you manage that? thats like saying multiple galaxys out there should be doing this sort of thing since there are some that move at almost the speed of light. i dont know why anybody thinks that travelling faster than the speed of light would slow time down, the speed of light is just a speed limit placed on the universe, it has no other affect on it. it may not even be a limit, and if it wasnt, most of our physics/science up till this point will need a total rethink.
Actually, it is quite intuitional thinking. If i stand on a train, and throw a stone backwards, it will be by the trains speed slower then if i had thrown it standing on solid ground. It is remarkable and unintuitive that that does not apply to light.
You seem to accept that the speed of light is constant no matter the frame of reference. This can only yield consistent observations in each inertial system if time slows down more the nearer you get to the speed of light. Since from observation the speed of light does not seem to be affected by your own velocity, almost all physicists accept special relativity and as a result time delation on faster moving objects. So far, special relativity has resisted every attempt to disprove it, and as long as that stays the case, there is no problem in using it.
Also, that was not even his point. His point was that If someone is travelling away from you at 0.99c, if you send a signal 2 days after he started it will reach him only after 200 days in your frame of reference.
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On July 23 2011 06:51 scorch- wrote:Show nested quote +On July 23 2011 04:55 Nawyria wrote:On July 23 2011 04:23 Trainrunnef wrote:
Question...
Why would one twin hear the communication of the other as slowed. Wouldn't there just be a delay in the communication due to the time it took for the light to reach twin a/b.
IIRC the speed of light is constant, and redshift/blueshift is due to an accelleration either towards or away from the reciever of the signal.
So with this in mind the communications would be heard by both twins with a normal speech pattern just a long pause. This is partly because of time dilatation. That is to say, when the two twins travel away from each other they observe each other's clocks as running slower; when the two twins travel towards each other, they observe each other's clocks as running faster. This is because our notion of what space and time shifts as the speed between two inertial frames becomes of order c. Another way to think about it is this: If I'm travelling at some reasonable fraction of the speed of light away from you (say, 50%) and I say a sentence to you that takes me 10 seconds to say, then by the time I've finished speaking I'll be 5 lightseconds further away from you relative to where I was when I started speaking and the end of the message will take 5 seconds longer to reach you than the start of the message. This means that you'll receive my original 10-second message smeared out over 15 seconds and thus I'll appear to be talking in slow-motion. This is kind of a funky way of saying this. The direction of travel isn't relevant to a discussion of time dilation, but is relevant to the waveshift. To be precise, I mean to say that when A is traveling towards B, B is aware of A's velocity. While B may observe A's clock to read a difference of 1.1 seconds after one second of travel, he is aware that A is moving towards him and that the light has originated at a distance that is closer by some non-trivial amount. Because B and A are both aware of time dilation and they know their relative velocities, B will still deduce that A's clock is moving more slowly than B's, and A will still deduce B's clock to be moving more slowly than B's. Correct?
Hmm, you are correct indeed. Time dilatation does not care about direction, only about the absolute speed; the visual impression of objects does. It seems I stand corrected.
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Thanks for an extremely interesting thread 
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if the person travelling at the speed of light constantly was talking to the person on a cell phone, surely the sound wouldnt ever reach the person traveling at the speed of light? or am i missing something
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On July 23 2011 07:04 GamerSyneX wrote:
if the person travelling at the speed of light constantly was talking to the person on a cell phone, surely the sound wouldnt ever reach the person traveling at the speed of light? or am i missing something
The point is that the travelling twin can never truly travel at the speed of light, but could reach any speed just below the speed of light. While it is true that the faster he goes, the longer it takes for the message to reach him; but given enough time, messages will reach him.
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On July 23 2011 07:04 GamerSyneX wrote:
if the person travelling at the speed of light constantly was talking to the person on a cell phone, surely the sound wouldnt ever reach the person traveling at the speed of light? or am i missing something
According to our understanding of our universe, no person can travel at the speed of light. So, if the person was travelling at the speed of light, our laws of physics break down and we have no idea what would happen.
If the person was travelling very close to the speed of light, it would reach him eventually. The length of time it took depends on the frame of reference.
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