Time Dialation and Biological systems

[ghwellsjr]

You guys are taking a very simple concept and confusing it. In Special Relativity, whoever and whatever is moving in a particular reference frame is experiencing time dilation. It's not an issue of what observers see because no one can see time dilation, rather it's an assignment due to a specified frame of reference.

How does this, in any way, contradict what I wrote?

Here's what you wrote:

I don't think you understand special relativity. Different observers disagree on the passage of time and length of objects in order to preserve a constant speed of light. You always see the clocks in your frame of reference as ticking normally, and measure objects as having the same length as in the rest frame. However, observers in a slower frame of reference see your clock ticking slower. Hence, they see your body processes occurring slower. There is no contradiction.

You have mentioned three different frames:
1) Your frame of reference.
2) The rest frame.
3) A slower frame of reference.
This is confusion. Look at this sentence:

You always see the clocks in your frame of reference as ticking normally, and measure objects as having the same length as in the rest frame.

Assuming that when you say "your frame of reference", you mean what everyone else means which is a frame in which you are at rest, then what do you mean by "the rest frame"?
Look at this sentence:

However, observers in a slower frame of reference see your clock ticking slower.

The first two frames apparently were at rest. What do you mean by "a slower frame of reference"?

If you pick one frame and realize that all objects are in that frame, then it is very clear how much time dilation each object experiences simply by their speeds in that frame. You can then do it all over again and pick another frame moving with repect to the first one and recalculate all the speeds and derive a new set of time dilations. Assigning different objects exclusively to different frames is confusion.

 

[Mark M]

Here's what you wrote:

You have mentioned three different frames:
1) Your frame of reference.
2) The rest frame.
3) A slower frame of reference.

1) I think it's generally understood what a reference frame is. I was speaking of an observer that was moving.

2) An observer free-falling in empty space.

3) Don't see the confusion here.

This is confusion.

Not really.

then what do you mean by "the rest frame"?

An observer sitting in empty space that isn't moving. This might be confusing you because you can't specify an absolute state if rest in SR, which you would be correct about.

The first two frames apparently were at rest. What do you mean by "a slower frame of reference"?

What makes you think this? I mean an observer that is moving with less velocity than the frame we were speaking of. What about that confuses you?

Let me be more specific - I never 'experience' time dilation. I don't feel my body slowing down, others observe it. This is well understood.

 

[ghwellsjr]

1) I think it's generally understood what a reference frame is. I was speaking of an observer that was moving.

So you think that it is generally understood that "your frame of reference" means "an observer that was moving"?

2) An observer free-falling in empty space..

And you think that it is generally understood that "rest frame" means "an observer free-falling in empty space"?

But a free-falling observer is simply another way of saying an inertial observer which is another way of saying a non-accelerating observer which is another way of saying an observer moving at a constant velocity, not necessarily at rest with respect to any frame.

3) Don't see the confusion here. Not really.

An observer sitting in empty space that isn't moving. This might be confusing you because you can't specify an absolute state if rest in SR, which you would be correct about. What makes you think this? I mean an observer that is moving with less velocity than the frame we were speaking of. What about that confuses you?

In Special Relativity, all velocities are defined with respect to the frame we are speaking of. How can an observer be moving with less velocity than the frame?

Let me be more specific - I never 'experience' time dilation. I don't feel my body slowing down, others observe it. This is well understood.

Nobody ever feels the effects of time dilation just like nobody feels the effects of velocity but both effects are defined according to an arbitrary Frame of Reference. In a particular Frame of Reference, if an observer is moving, then he is experiencing velocity even though he can't feel it and he is experiencing time dilation even though he can't feel it.

But, at the same time, nobody else observes time dilation in another observer. How could they? If it is an effect of a particular FoR and the effect can change for the exact same scenario with a different FoR, then how would you account for any observer being able to observe different time dilations in another observer, just because different FoRs were being used?

 

[indirachap]

I'm afraid things things are getting too technical for me.

If a spaceship travels from Planet Earth to a Plant X and back at the near speed of light would the clock onboard the spaceship run considerably slower than the clock at the spaceship station on Earth? If the answer is yes would this not mean that the crew lived their lives onboard in actual slowmotion - indeed a virtual standstill?

 

[ghwellsjr]

I'm afraid things things are getting too technical for me.

If a spaceship travels from Planet Earth to a Plant X and back at the near speed of light would the clock onboard the spaceship run considerably slower than the clock at the spaceship station on Earth? If the answer is yes would this not mean that the crew lived their lives onboard in actual slowmotion - indeed a virtual standstill?

This is the classic Twin Paradox. After the spaceship returns to Earth, the crew will be much younger than the people who remained on Earth. Is that all you want to know?

 

[Mark M]

So you think that it is generally understood that "your frame of reference" means "an observer that was moving"?

Point me to where I said this.

And you think that it is generally understood that "rest frame" means "an observer free-falling in empty space"?

I really don't know how else I could put this. I simply meant an observer who wasn't moving. I acknowledged that this was sloppy, because there is no such thing as being 'at rest' without specifying a FoR in special relativity. I fail to see how it has any relevance to the point.

In Special Relativity, all velocities are defined with respect to the frame we are speaking of. How can an observer be moving with less velocity than the frame?

What do you mean? If I'm moving 100 m/s in someone's FoR then they're moving with less velocity. This is trivial.

Nobody ever feels the effects of time dilation just like nobody feels the effects of velocity

Correct.

But, at the same time, nobody else observes time dilation in another observer. How could they? If it is an effect of a particular FoR and the effect can change for the exact same scenario with a different FoR, then how would you account for any observer being able to observe different time dilations in another observer, just because different FoRs were being used?

I really can't make sense out of this. If I observe some moving observer holding a clock that is ticking slower than normal, then I think I'd be justified in saying that time dilation is occurring.

Finally, I don't understand the point of your posts. Do you disagree that time dilation is an effect seen by observers? I simply stated that although another observer observers someone's clock ticking slower, that person measures their time normally.

 

[indirachap]

This is the classic Twin Paradox. After the spaceship returns to Earth, the crew will be much younger than the people who remained on Earth. Is that all you want to know?

How does a biological system survive life slowed to a virtual standstill in a spaceship traveling at the near speed of light?

 

[Mark M]

I'm afraid things things are getting too technical for me.

If a spaceship travels from Planet Earth to a Plant X and back at the near speed of light would the clock onboard the spaceship run considerably slower than the clock at the spaceship station on Earth? If the answer is yes would this not mean that the crew lived their lives onboard in actual slowmotion - indeed a virtual standstill?

The clock is slower in the ship. They had to undergo an acceleration to h their velocity, so they are the ones in motion. See the twin paradox.

They, according to the observers on earth, lived in slow motion. But they measure time in their FoR as ticking perfectly normally.

 

[indirachap]

The clock is slower in the ship. They had to undergo an acceleration to h their velocity, so they are the ones in motion. See the twin paradox.

They, according to the observers on earth, lived in slow motion. But they measure time in their FoR as ticking perfectly normally.

Are you absolutely sure about this? Surely if the clock on board runs slow, biological systems "must" run slow as well?

 

[Mark M]

Are you absolutely sure about this? Surely if the clock on board runs slow, biological systems "must" run slow as well?

Everything on the ship runs slower according to the observers on earth. In the ship, time is normal. It takes me the same time to brush my teeth in the morning, for a clock to tick, for anything. However, observers on Earth see everything aboard the ship moving in slow motion. It is all dependent on which frame of reference you are in.

 

[indirachap]

Everything on the ship runs slower according to the observers on earth. In the ship, time is normal. It takes me the same time to brush my teeth in the morning, for a clock to tick, for anything. However, observers on Earth see everything aboard the ship moving in slow motion. It is all dependent on which frame of reference you are in.

But in the ship time is not normal in its own frame of reference because the clock on the wall is showing that time is running slow.

 

[Mark M]

But in the ship time is not normal in its own frame of reference because the clock on the wall is showing that time is running slow.

No, it only appears slow to the observers on earth. This is a key concept in special relativity - different observers disagree on the passage of time. The clock appears slow because the ship, in Earth's frame of reference, is moving. In our frame of reference on the ship, everything in the ship is normal.

 

[indirachap]

No, it only appears slow to the observers on earth. This is a key concept in special relativity - different observers disagree on the passage of time. The clock appears slow because the ship, in Earth's frame of reference, is moving. In our frame of reference on the ship, everything in the ship is normal.

How can everything in the ship traveling at the near speed of light appear normal to those onboard when everything is at a virtual standstill ?

 

[Dale]

How can everything in the ship traveling at the near speed of light appear normal to those onboard when everything is at a virtual standstill ?

Remember, all of the biological functioning is at a virtual standstill. Their wall clocks are slowed down and so are their heartbeats, their nerve impulses, their muscle contractions, etc. everything slowed by the same amount. How would they notice anything?

Right now there exists a reference frame where YOU are traveling at .999999 c and are slowed down by an enormous amount. Do YOU notice that time seems slow right now?

Btw, did you understand my post 21?

 

[Mark M]

How can everything in the ship traveling at the near speed of light appear normal to those onboard when everything is at a virtual standstill ?

It is only in a virtual stand still according to the observers on earth. Not to the observers on the ship.

Are you aware why time dilation occurs in the first place? It occurs to ensure that different observers agree on the speed of light in a vacuum. Hence, different observers must disagree on the passage of time and the length of objects. The key word there is 'disagree'. Time in your own frame of reference is always normal, you see other observer's time adjusting.

I have to ask, how much have you studied special relativity?

 

[Chestermiller]

How can everything in the ship traveling at the near speed of light appear normal to those onboard when everything is at a virtual standstill ?

Everything on the ship is not at a virtual standstill. It is proceeding at its normal rate, including clocks' tick rates, and human heart rates. But, to people back on earth, and for observers at rest with respect to the earth, the clocks and biological processes on the ship seem to be running slow. There is no test that the people in the Earth's frame of reference can perform to convince them that the processes taking place on the spaceship are running anything but slow.

Chet

 

[indirachap]

Thank you both for your input - its much appreciated. Its just I have received conflicting info from different scientists such as: When traveling at the near speed of light every would come to a virtual standstill. Cheers until later.

 

[phinds]

Thank you both for your input - its much appreciated. Its just I have received conflicting info from different scientists such as: When traveling at the near speed of light every would come to a virtual standstill. Cheers until later.

If this scientist you speak of knows what he is talking about, he did NOT say everything WOULD come to a virtual standstill, he said it would APPEAR (to someone in a different frame of reference) to be at a virtual standstill.

There is no conflict here, it just that you are trying to understand something that requires knowledge of relativity and apparently you have no understanding of relativity.

I will try the explanation for you one more time, and I guarantee you no one with an understanding of relativity will contradict this:

When someone is traveling close to the speed of light, everything seems perfectly normal to them. Their hearts beat at the normal speed. In their frame of reference they are not moving at all (I'm not talking now about periods of acceleration).

Someone in a different frame of reference, the one from which it appears that they are traveling close to the speed of light will see them doing everything in slow motion.

EDIT: Google the "Twin Paradox"

 

[indirachap]

I have read various articles on relativity and and am happy with the idea of FORs. However I feel somewhat under pressure from the science community to just accept the idea without question - especially counterintuitive issues. This evokes suspicion in the layman who then looks for chinks in the armour of theoretical science and then what does he find out? He finds out that science, for quite sometime now, has not been able to reconcile the theory of the everyday world with the theory of the very small in a theory of everything which subsequently begs the question wether certain parts of scientific theory has not been fudged over so as to speak in order to make other parts of theory work.

 

[BruceW]

Nothing has been fudged over. That is the great thing about science. For example, we had non-relativistic mechanics for ages, and it was very useful to make lots of predictions. But eventually relativity came along, and we realized that non-relativistic physics was not theoretically 'correct', but of course it was approximately correct in the limit of low speeds, and low gravity. So from this example, I'm trying to make the point that even though relativity is not a 'theory of everything' (whatever that might be), relativity is still a useful theory.

About accepting relativity - It is a very good idea to question the physics. For example, the twin paradox. It was only when I really had a good think about the twin paradox that I started to get more familiar with the idea of world lines and the spacetime interval. So it is by questioning the theory that you can start to learn it. And this is by a positive kind of questioning. You must actively try to find the answer. This will mean that you start learning the maths and physics of relativity, and this leads to understanding relativity. I guess I'm saying don't be too hasty to dismiss it.

 

[Ryan_m_b]

I have read various articles on relativity and and am happy with the idea of FORs. However I feel somewhat under pressure from the science community to just accept the idea without question - especially counterintuitive issues.

No idea where you are getting that feeling from, certainly not here. I can't find any examples of someone admonishing you for questioning and plenty of people trying to help you to understand. To suggest otherwise is to be a severe distortion of the facts and would be quite insulting.

This evokes suspicion in the layman who then looks for chinks in the armour of theoretical science and then what does he find out? He finds out that science, for quite sometime now, has not been able to reconcile the theory of the everyday world with the theory of the very small in a theory of everything which subsequently begs the question wether certain parts of scientific theory has not been fudged over so as to speak in order to make other parts of theory work.

Yes science is incomplete, if it wasn't we would have stopped. This is not a hidden fact but a foundation of modern scientific enquiry. You're framing this as though there is a conspiracy amongst scientists to cover up the fact that we don't know everything, I'm sorry but like most conspiracy theories it's all in your head.

Thank you both for your input - its much appreciated. Its just I have received conflicting info from different scientists such as: When traveling at the near speed of light every would come to a virtual standstill. Cheers until later.

Only from the perspective of someone in another frame of reference. Put it this way:
Alice and Bob are sitting in spaceships at rest relative to each other. Alice fires up her engines and blasts away, measuring her speed relative to Bob to be .9c. Bob looking through his spaceship's telescope will see everything on Alice's ship happening slowly; the clock will tick slower than his, her breathing will be slower, heart rate etc. However for Alice nothing has changed. Time seems to pass exactly as it did when she was at rest.

 

[indirachap]

No idea where you are getting that feeling from, certainly not here. I can't find any examples of someone admonishing you for questioning and plenty of people trying to help you to understand. To suggest otherwise is to be a severe distortion of the facts and would be quite insulting.

No insult intended. By pressure I mean not pressure from scientists on this board but pressure from science in general on the layman to conform to conventional scientific thought.

Only from the perspective of someone in another frame of reference. Put it this way:
Alice and Bob are sitting in spaceships at rest relative to each other. Alice fires up her engines and blasts away, measuring her speed relative to Bob to be .9c. Bob looking through his spaceship's telescope will see everything on Alice's ship happening slowly; the clock will tick slower than his, her breathing will be slower, heart rate etc. However for Alice nothing has changed. Time seems to pass exactly as it did when she was at rest.

"However for Alice nothing has changed". Is this phrase not pure supposition? Surely for Alice everything has changed. Bob can see that Alice is virtually frozen in time by traveling at the near speed of light. Supposing that biological systems are affected by time dialation, Alice by being virtually dead would not percieve anything like normality and would not even if she were functioning normally

The question is (a) what is the actual physical state of Alice's biological system when Bob saw her through his telescope and (b) does this violate some basic a priori principles of life as we know it. If the answer is yes, then surely science is irrational?

 

[Ryan_m_b]

No insult intended. By pressure I mean not pressure from scientists on this board but pressure from science in general on the layman to conform to conventional scientific thought.

I'm not going to dispute that you feel that way and I can't really comment on it more without knowing more about your background.

"However for Alice nothing has changed". Is this phrase not pure supposition? Surely for Alice everything has changed. Bob can see that Alice is virtually frozen in time by traveling at the near speed of light. Supposing that biological systems are affected by time dialation, Alice by being virtually dead would not percieve anything like normality and would not even if she were functioning normally

From Alice's point of view nothing has changed. Even from Bob's perspective she is not virtually dead, he could record his observations of her and play them at a faster speed and she would seem to behave exactly as she was when they were stationary.

The question is (a) what is the actual physical state of Alice's biological system when Bob saw her through his telescope and (b) does this violate some basic a priori principles of life as we know it. If the answer is yes, then surely science is irrational?

Alice's biology is behaving in exactly the same manner as it was before she accelerated away, just slower from Bob's perspective. There is nothing inconsistent here.

 

[phinds]

The question is (a) what is the actual physical state of Alice's biological system when Bob saw her through his telescope and (b) does this violate some basic a priori principles of life as we know it. If the answer is yes, then surely science is irrational?

YOU ARE NOT LISTENING !

As stated previously by me and others, Alice experiences NOTHING untoward. Everything is perfectly normal to her. Time dilation is an artifact of frames of reference. It is NOT experienced by the Alice, it is observed by Bob. It is an artifact of relativity. Get over it and move on.

EDIT: I see Ryan beat me to it (and with less vehemence )

 

[Dale]

I feel somewhat under pressure from the science community to just accept the idea without question

This is an absurd comment. We are not asking you to accept the idea without question. We are asking you to accept the boatloads of experimental evidence that supports the idea:

http://www.edu-observatory.org/physics-faq/Relativity/SR/experiments.html

It isn't science applying pressure on you to change your way of thinking, it is nature. Yes, our classical/intuitive worldview is hard to relinquish, but it has been experimentally disproven. Nature simply doesn't work in the way you want it to.

 

[Dale]

"However for Alice nothing has changed". Is this phrase not pure supposition? Surely for Alice everything has changed. Bob can see that Alice is virtually frozen in time by traveling at the near speed of light. Supposing that biological systems are affected by time dialation, Alice by being virtually dead would not percieve anything like normality and would not even if she were functioning normally

You are currently traveling at .9999999 c in some reference frame. Do you notice anything abnormal? Are you virtually dead?

The question is (a) what is the actual physical state of Alice's biological system when Bob saw her through his telescope and (b) does this violate some basic a priori principles of life as we know it. If the answer is yes, then surely science is irrational?

(a) Alice is "actually" slowed down IN BOB'S FRAME. (b) no it doesn't violate any principles of biology. I already explained to you in great detail why not, but it seems that you either did not understand the answer or you understand it but don't want to acknowledge it.

 

[ghwellsjr]

...
If a spaceship travels from Planet Earth to a Plant X and back at the near speed of light would the clock onboard the spaceship run considerably slower than the clock at the spaceship station on Earth? If the answer is yes would this not mean that the crew lived their lives onboard in actual slowmotion - indeed a virtual standstill?

I have read various articles on relativity and am happy with the idea of FORs.

...
"However for Alice nothing has changed". Is this phrase not pure supposition? Surely for Alice everything has changed. Bob can see that Alice is virtually frozen in time by traveling at the near speed of light. Supposing that biological systems are affected by time dialation, Alice by being virtually dead would not percieve anything like normality and would not even if she were functioning normally

The question is (a) what is the actual physical state of Alice's biological system when Bob saw her through his telescope and (b) does this violate some basic a priori principles of life as we know it. If the answer is yes, then surely science is irrational?

Let's say Bob stays on Earth and Alice travels at high speed toward Planet X where Carl lives. In the FoR where Earth and Planet X are both at rest, Alice will be experiencing time dilation. When Bob looks at Alice through his telescope, he sees her in slow motion. However, when Carl sees Alice take off through his telescope and start her journey toward him, he sees her in fast motion. Furthermore, when Alice looks back at Bob on Earth, she sees him in slow motion and as she looks ahead at Carl on Planet X, she sees him in fast motion. All these different observations from different points of view are not what we call time dilation. You have to make a distinction between what is observed by different observers and what is assigned by the specified Frame of Reference.

Now let's consider a different FoR, one in which Alice is at rest while she is "traveling" toward Planet X. Now Alice is experiencing no time dilation but both Bob on Earth and Carl on Planet X are experiencing time dilation. They are the ones that are traveling at near light speed and are "virtually frozen in time", as you like to say.

But again, as Alice looks back at Bob on Earth, she sees him in slow motion and as she looks ahead at Carl on Planet X, she sees him in fast motion, just as before. And when Bob looks at Alice, he sees her in slow motion and Carl sees her in fast motion. The selected FoR has no bearing on what observers see.

So if you are really happy with the idea of Frames of Reference, then you should have no problem understanding that time dilation is relative to the selected FoR and has nothing to do with what observers see.

Do you understand all this? Do you have any questions?

 

[indirachap]

Thank you ghwellsjr and everybody else for their kind replies.

[Do you understand all this? Do you have any questions?]

I am unhappy about the idea that Alice would have aged less than Bob on her return to Earth. Does this not violate some basic a priori principles of biology?

 

[Dale]

Does this not violate some basic a priori principles of biology?

No, it does not.

 

[Nugatory]

I am unhappy about the idea that Alice would have aged less than Bob on her return to Earth. Does this not violate some basic a priori principles of biology?

No. Alice is away for five years, she ages fives years, celebrates five birthdays (assuming that she celebrates a birthday every 365*24*3600 seconds according to her wristwatch), her wristwatch records the passage of five years, if she brings a sample of radioactive material with a five-year half-life with her it will be decay by 50% during the journey. No paradox or contradiction there, she's just lived through five years and aged accordingly just as any other chemical, biological, physical, or mechanical system would age over five years.

Bob stays at home for ten years, ages ten years, celebrates ten birthdays, his wristwatch records the passage of ten years, his sample of the radioactive material will be 75% decayed because that's two half-lives. There's no paradox or contradiction there, he's just lived through ten years and aged accordingly just as any other chemical, biological, physical, or mechanical system would age over ten years.

It's just a bit surprising when they meet each other.