Most discussions about time travel regard physics appropriately so , however human physiology should also be important . For example , when someone travels at the a speed close to that of light ,time slows down including the age of the person travelling at the great speed . This is illustrated by Eienstien's example of the traveller in space who comes back to see everyone is dead and gone while he has only aged a brief amount of time .therefore there must be some physiological process that slows done allowing for this person to basically live much longer relative to his contemporaies .What happens ? The answer may afford a clue to time travel and should be examined .
time travel
- Thread starter surgcare
- Start date
That's right.
Actually, it isn't just that your body and mind "think" everything is normal. As far as the reference frame of your ship is concerned, everything really is normal.
And here's the really weird part: You would expect that the astronaut will preceive the earth clocks as going fast, right? But in reality, the exact opposite happens. As far as the astronauts are concerned, it is the earth who is in motion. And since clocks in motion are slowed down, they will preceive the earth's clocks as being slow. Yet, at the same time, we preceive their clocks as going slow relative to us!
So, what's going on here? Isn't this a paradox? No, because comparing earth time and ship time can only be done indirectly, due to the great distance between the earth and the ship.
Perhaps an example will help clear things up:
Let us assume that the ship is launched from earth at 60% the speed of light. The ship is launched at Noon. Four hours later, at 4 PM, we want to compare the clocks on the ship with the clocks on earth.
How do we do that? By sending the following question via radio waves:
"It's 4 PM here. Please respond with the time shown by your clocks the minute you get this message."
Of-course, since the ship is going at 60% the speed of light, it will take the radio signal some time to reach the ship. 6 hours, to be precise. For after 6 hours, at 10 PM, the ship will be 0.60x10=6 light-hours away from earth.
It would take another 6 hours for the astronaut's response to reach the earth. After a total of 12 hours, at 4 AM the following day, the response would reach mission control: "Our clocks read 8 PM".
So far so good. There is no paradox. Both the astronauts and the people left on earth agree about the sequence of events: The earth's clocks showed 4 PM when the meessage was sent. The ship's clocks showed 8 PM when the message was received. The only thing left to do, is to calculate how many hours elapsed between these two events.
We already know that from the earth's point of view, it took 6 hours for the signal to reach the ship. But would the astronauts on the ship agree with this statement? Let us do the calculation:
The message was received at 8 PM, which is 8 ship-hours after launch. From the point of view of the ship, the earth is moving away at 60% the speed of light. So after 8 hours, the earth is 0.60x8=4.8 light hours away.
At the same time, the signal from earth is approaching the ship at exactly the speed of light (the speed of light never changes, even when the source is moving). So every hour, the distance between the earth and the radio waves (as measured from the ship) increases by 1+0.6 = 1.6 light hours. Since the signal (and the ship) is now 4.8 light hours from earth, it must have been sent 4.8/1.6 = 3 hours ago.
So from the astronauts' point of view, the delay wasn't 6 hours. It was only 3 hours. And as we shall see immediately, this disagreement is the reason each party believes the clocks of their colleagues are slow:
For the guys at mission control, The question was received 6 hours after it was sent. Since it was sent at 4 PM, they would conclude that the reply was sent at 10 PM (4+6). And since the reply was "the ship's clocks show 8 PM", this means that the ship's clocks are 2 hours (10-8) slow.
For the astronauts, the question was received only 3 hours after it was sent. Since it was received at 8 PM (by their watch), they would conclude that it was sent at 5 PM (8-3). And since the message stated "It's 4 PM on earth", this means that the earth's clocks are 1 (5-4) hour slow.
Both point of views are correct. There is no paradox, because niether party can look at the other party's clock at real time. Indeed, the very meaning of "real time" is different for the two parties.
Actually, it isn't just that your body and mind "think" everything is normal. As far as the reference frame of your ship is concerned, everything really is normal.
And here's the really weird part: You would expect that the astronaut will preceive the earth clocks as going fast, right? But in reality, the exact opposite happens. As far as the astronauts are concerned, it is the earth who is in motion. And since clocks in motion are slowed down, they will preceive the earth's clocks as being slow. Yet, at the same time, we preceive their clocks as going slow relative to us!
So, what's going on here? Isn't this a paradox? No, because comparing earth time and ship time can only be done indirectly, due to the great distance between the earth and the ship.
Perhaps an example will help clear things up:
Let us assume that the ship is launched from earth at 60% the speed of light. The ship is launched at Noon. Four hours later, at 4 PM, we want to compare the clocks on the ship with the clocks on earth.
How do we do that? By sending the following question via radio waves:
"It's 4 PM here. Please respond with the time shown by your clocks the minute you get this message."
Of-course, since the ship is going at 60% the speed of light, it will take the radio signal some time to reach the ship. 6 hours, to be precise. For after 6 hours, at 10 PM, the ship will be 0.60x10=6 light-hours away from earth.
It would take another 6 hours for the astronaut's response to reach the earth. After a total of 12 hours, at 4 AM the following day, the response would reach mission control: "Our clocks read 8 PM".
So far so good. There is no paradox. Both the astronauts and the people left on earth agree about the sequence of events: The earth's clocks showed 4 PM when the meessage was sent. The ship's clocks showed 8 PM when the message was received. The only thing left to do, is to calculate how many hours elapsed between these two events.
We already know that from the earth's point of view, it took 6 hours for the signal to reach the ship. But would the astronauts on the ship agree with this statement? Let us do the calculation:
The message was received at 8 PM, which is 8 ship-hours after launch. From the point of view of the ship, the earth is moving away at 60% the speed of light. So after 8 hours, the earth is 0.60x8=4.8 light hours away.
At the same time, the signal from earth is approaching the ship at exactly the speed of light (the speed of light never changes, even when the source is moving). So every hour, the distance between the earth and the radio waves (as measured from the ship) increases by 1+0.6 = 1.6 light hours. Since the signal (and the ship) is now 4.8 light hours from earth, it must have been sent 4.8/1.6 = 3 hours ago.
So from the astronauts' point of view, the delay wasn't 6 hours. It was only 3 hours. And as we shall see immediately, this disagreement is the reason each party believes the clocks of their colleagues are slow:
For the guys at mission control, The question was received 6 hours after it was sent. Since it was sent at 4 PM, they would conclude that the reply was sent at 10 PM (4+6). And since the reply was "the ship's clocks show 8 PM", this means that the ship's clocks are 2 hours (10-8) slow.
For the astronauts, the question was received only 3 hours after it was sent. Since it was received at 8 PM (by their watch), they would conclude that it was sent at 5 PM (8-3). And since the message stated "It's 4 PM on earth", this means that the earth's clocks are 1 (5-4) hour slow.
Both point of views are correct. There is no paradox, because niether party can look at the other party's clock at real time. Indeed, the very meaning of "real time" is different for the two parties.
Darby
Epochal Historian
Surgcare,
"Einstein" - the name is Einstein. And I don't recall a paper where he spoke to the exact scenario that you attributed to him.
Anyway...
The slowing of time in the sense that you alluded to is found in the Special Theory of Relativity. A person who is "at rest" will observe all physical processes slow for an object that s/he observes to be traveling at near light speed. This means that electrons orbit more slowly, radio-isotopes have longer half-lives, cellular activity is slowed in living matter, etc. It is all physics. "Physiology" is just another word used to describe bio-physics.
And remember that this is the Theory of Relativity. In Special Relativity neither person can say for a fact that they are in the rest frame or the moving frame. Each will look at the other and say that the other is aging too fast.
They can never answer the question of who was moving fast and who was at rest under Special Relativity. To answer the question of who was moving fast and who was not moving they both have to "hit the brakes". The one who slams face first into the wind sceeen is the one who was in the moving frame.
OK - the one who felt the force of acceleration when the brakes were applied was the one who was moving - thus the one who will age more slowly. And this involves the General Theory of Relativity - acceleration & gravitation. The principle of equivalence.
"Einstein" - the name is Einstein. And I don't recall a paper where he spoke to the exact scenario that you attributed to him.
Anyway...
The slowing of time in the sense that you alluded to is found in the Special Theory of Relativity. A person who is "at rest" will observe all physical processes slow for an object that s/he observes to be traveling at near light speed. This means that electrons orbit more slowly, radio-isotopes have longer half-lives, cellular activity is slowed in living matter, etc. It is all physics. "Physiology" is just another word used to describe bio-physics.
And remember that this is the Theory of Relativity. In Special Relativity neither person can say for a fact that they are in the rest frame or the moving frame. Each will look at the other and say that the other is aging too fast.
They can never answer the question of who was moving fast and who was at rest under Special Relativity. To answer the question of who was moving fast and who was not moving they both have to "hit the brakes". The one who slams face first into the wind sceeen is the one who was in the moving frame.
OK - the one who felt the force of acceleration when the brakes were applied was the one who was moving - thus the one who will age more slowly. And this involves the General Theory of Relativity - acceleration & gravitation. The principle of equivalence.
experiment1
Temporal Novice
Also, isn't time a concept that we created? It's a whole dimension to itself. Space is another one. If we create our own reality, which I personally think we all did and do collectively, then what we have created is consensus reality. Think of of the many times we have dreamed about our past and realized that the dream seemed so real. I believe we can go to the past and replace negative things that we have done and replace them with positive actions, thus altering the past, present, and future. <font color="blue"> [/COLOR] /ttiforum/images/graemlins/smile.gif
Jaxon
Temporal Novice
Wishing it doesn't make it so. And you don't change time just for yourself. Your actions and interactions cause ripple effects in other peoples' lives, which in turn affect their past.
We all make bad decisions. Learn to deal with them and learn from them so you don't make them again.
We all make bad decisions. Learn to deal with them and learn from them so you don't make them again.
Darby
Epochal Historian
Sugarcare,
The process isn't strictly psysiological. The process is applicable to all physical processes. From the perspective of the person in the accelerated frame nothing unusual happens - although if that person looks "out the window" to see the universe around him/herself he will observe that the universe is moving very quickly. By moving I mean aging.
The process has been examined. The examinate started in 1905, when Einstein first published his June paper (I believe that it was the June paper...he published five ground breaking papers in 1905). It wasn't really taken seriously until 1925. But thereafter Special & General Relativity became the framework for all of physics - and still are the base for all of physics. The effects predicted by those two combined theories have been confirmed by thousands of experiments.
The process isn't strictly psysiological. The process is applicable to all physical processes. From the perspective of the person in the accelerated frame nothing unusual happens - although if that person looks "out the window" to see the universe around him/herself he will observe that the universe is moving very quickly. By moving I mean aging.
The process has been examined. The examinate started in 1905, when Einstein first published his June paper (I believe that it was the June paper...he published five ground breaking papers in 1905). It wasn't really taken seriously until 1925. But thereafter Special & General Relativity became the framework for all of physics - and still are the base for all of physics. The effects predicted by those two combined theories have been confirmed by thousands of experiments.