What does the theory of relativity have to do with basic biology?

Factual Questions
1

Nothing can travel faster then the speed of light? Fine, I give them that (though I don’t necessarily agree), I don’t think it matters for this post. It makes no difference.

The train scenario where two people see different things at the same time? Umm, ties into the speed of light, and distance from the light. That’s a different post.

NASA synchronized an atomic clock on the shuttle and one on the ground and they weren’t synchronized when the shuttle came back. Umm, O.K. fine. Was that meters or feet (had to throw that in).

So a person traveling at the speed of light does not age relative to the person standing still?

Our break down of cells, called aging, stops at the speed of light? Why?

I was once told that it is because the electrons that circle our protons and neutrons do so at nearly the speed of light. Therefor they do not circle the nucleus as fast in one direction. I don’t by it. The electrons are going just as fast as the nucleus, they are relative to the nucleus of the atom and the speed the atom is traveling. Just as Earth circles the Sun as we spin around our galaxy.

Why would speed slow down any clock, including aging?

Oh boy, here it comes.

2

This is ridiculous; electrons do not orbit anything. They just teach you that in high school to dodge quantum mechanics. This is not why.

No. Time stops at the speed of light. The cells break down at the same rate; x cells per second; but the duration of a second for an outside observer changes.

Here’s the deal.

The speed of light is constant for all observers. Ok? This is confirmed by experiment; it’s reality.

So you imagine a guy moving forward at velocity V on a flat train car down a reflective tunnel. And he’s shining a flashlight straight up. So for him, the light goes ||, UP and DOWN the hieght of the tunnel.

You have another guy watching. He sees the forward motion of the train, too, so he sees the light go UP AND FORWARD, then DOWN AND FORWARD. /\

Now, basic geometry tells us that that distance is longer than up and down, because the hypotenuse of a right trinagle is longer than the other sides, yes?

But they’re both seeing the same trip, by the same light, at the same speed for both of them.

If the tunnel is Y meters high, for the guy on the train, then the light’s trip up and down took Y/c seconds, where c is the speed of light.

For the outside observer, the equation is messier, because the hypotenuse is based on the distance the train traveled and the hieght of the tunnel, and the distance the train traveled is based on the velocity of the train and the time which has passed, which is what you’re solving for in the first place.

But if you do the math, the times are different. That’s the way it has to be, if c isn’t different for each observer, which its not.

No meters or feet to screw up; it’s just a thought experiment, but it uses simple mathematics to prove that time is not an absolute.

The cells are decaying more slowly to an outside observer, but that’s only because time as a whole for anything with acceleration is happening more slowly.

–John

3

Relativity says nothing about travelling faster than the speed of light, it only rules out accelerating past the speed of light. Things that have always been travelling faster than c are possible.

4

I understand that an outside observer would see things differently because of the speed of the train.

So the speed of light can not increase or decrease if put on a moving object. Like a bullet would travel faster if shot out of a moving car. O.K.

I don’t see this as the issue.

Was the person on the train in the tunnel for 1 second? Was the person watching outside for 1 second?

They saw different things because of speed and distance, O.K.

I don’t understand what this has to do with our own biological clock.

I’m trying to though.

5

Possible does not mean observed, however. I don’t think anyone has ever observed a tachyon (what a particle that goes faster than c would be called, if we ever found one).

And it should be clarified that c is the speed of light in a vacuum. The speed of light in a medium, like air, is slower. I, myself, think c should be renamed Einstein’s Constant, but that’s just MHO.

6

Yue Han has it right, but it may leave you wanting…

So to expand on this a bit: It’s fundamentally about the way we measure things. When we want to measure the space-time relationship between events, we can use a number of different techniques, but generally the most accurate measurements involve the use of light. It is not essential that we use light as our ruler, but since Yue Han has already given an excellent explanation why two observers will measure time and space differently, let’s stick with that. You may have to trust me that any other measurement technique will yield the same general results, just with lower resolution and accuracy.

So what has this got to do with cellular biology? Well, all of molecular processes involved in cellular biology can be expressed in terms of events. The process we called life is merely the movement of molecules and this movement could, theoretically, be measured with light by different observers. The measurements taken in local proximity to the cell would differ with the measurements taken by a remote observer in exactly the same way as any macro event. In other words, physics at the molecular level have to follow the same laws as physics at the macro level.

Hope that helps.

7

Well, no, no one has ever obseved a tachyon, because the same math that tells you that you can’t accelarate past the speed of light from below tells you that you also can’t accelerate past it from above. Another words, tachyons may or may not exist, but they’ll never get down to speeds lower than c, and hence (as I understand the argument) you can never observe them.

8

Y’know, I suspected as much, even though I’ve never done any real research on the topic. Thanks for the info.

One final question: What is the benefit of postulating particles that nobody can observe, and that can have no observable impact on what we can observe?

9

AFAIK, it doesn’t change anything to your biological clock. You’re aging as quickly (or slowly, depending on how optimistic you are) than usual. If you spend one year at a very high velocity, perhaps 10 years will have been elapsed for other folks, and so you’ll be younger than them, but you would felt only one year has elapsed, so you won’t live longer. You would still live say 70 years, except that meanwhile 700 years will have elapsed for other people. But as far as you and your body are concerned, it was only an ordinary 70 years long life.

10

enipla

No. They saw light cover different amounts of ground during the same, um, period. If this were classical mechanics and, say, a bouncing ball, it wouldn’t be a problem, because the outside observer would include the speed of the train forward in the speed of the ball.

But when you’re dealing with light, the speed of light is always c. Always. If you’re going 60 miles an hour, and you shine a light ahead of you, it’s going ahead of you at c. And if someone is standing still and watching you go forward, instead of seeing the light travelling at c+60, which is what classical mechanics expects, he sees it travelling at… c.

No. The person in the train, moving at v, experienced a different amount of time than the person outside tunnel, for the same period, as marked by events.

Let’s deal with the interval from the light switch on, until it hits the roof. This is a period defined by events, not by a clock. It should still happen in the same amount of time.

(At the distances I am using, there would be a delay in seeing things because of the distance; the distances were only picked to make the math easier, so let’s ignore the delays)

A light-second is a unit of length definined as how far light goes in a second. If the tunnel is 4 light-seconds tall (BIG tunnel), 4 seconds would pass for the guy on the train. He would see the light travel up 4c meters at c m/s. The light takes 4 seconds to travel from floor to ceiling.

If the train was going (3/4)c (FAST train), in that 4 seconds, he would have covered 3 lightseconds. So for an outside observer, the light would make the hypotenus of a right triangle with hieght 4 and length 3. Thanks to my clever choice of number, we see that this is 5. The light travels 5c meters from an outside observers perspective, and it does it a c m/s, so the light takes 5 seconds to travel from floor to ceiling.

*The person on the train is experiencing only 4/5 the time the person outside does. *

His biological clock, relative to his watch, is passing at the same rate; x cells dying per second. But his watch, and any other timekeeping device that is accelerating with him, is ticking more slowly from the perspective of an outside observer.

–John

11

Slight nit here. While I agree that your physical age will have been time dialated, I’m not sure about your conscious age - you used the term “felt”, which implies consciousness. Since we don’t have an accurate model for consciousness and how it relates to space-time and relativity, and since there is some evidence to suggest that consciousness may actually be a quantum mechanics phenomenon, we don’t know exactly what to expect.

We do know that the theory of relativity and the theory of quantum mechanics are in some disagreement with respect to space and time.

This may be drifting off topic a bit, and I don’t think it can be answered yet, but it does add an interesting twist to the relativity in biology question (assuming we’re generous enough to include consciousness in our list of biological phenomena).

12

Thank you for all your insightful responses. The fog is lifting - a little. While I re-read these posts for about the 10th time I would like to ask one more question.

I never understood or really thought about the constant speed of light for all observers. I do now. But, how was this proven? Has it be done with a physical experiment?

13

Mostly, I think, it’s just noting that they DO satisfy the equations, and you can’t rule them out. But I’m not an expert on this…

Actually, this pops out of the equations that govern electromagnetic phenomena. One possibility was that those equations were wrong, and the other was that our intuition was wrong and the speed of light is constant. Since Maxwell’s equations work so well, Einstein decided that it was intuition that was wrong and worked from there. I suspect that many experiments have verified this by now, although not being a relativist, I don’t know any good references off the top of my head.

14

Actually the constancy of the speed of light is an axiom. It cannot be proved, though it could theoretically be disproved. The Michaelson Morley experiment is usually named as the chief source of support for the axiom.

15

Well, can’t you find length contractions and time dilations and whatnot? If you can observe these, I’d think the constancy of c would be demonstrated automatically.

16

When light enters a denser medium than a vacuum (i.e. air, water, molasses) it slows down somewhat, doesn’t it? I haven’t done any physics in a while, but I remember this pretty well. Couldn’t there be some medium in which a tacheon could be slowed down enough so we could detect it? Or would it also involve a situation a little like the neutrino, where you’d need to figure out the probability of one actually hitting whatever sensor you have?[sub]isn’t that how neutrino detectors work? one occasionally actuallly hits a deuterium atom, and sensors pick that up?[/sub].

17

Quoth ACoverOfNoise:

One of the postulates of Special Relativity is that there is no experiment which an observer can perform to determine if he’s moving or not. Now, I can devise an experiment to measure “consciousness time”: I can, for instance, measure the amount of time it takes a person to do a math problem of a certain complexity, or survey a sufficiently large group of people on how long an hour “felt” to them. If this “conscious” measure of time disagrees with a wristwatch for a moving observer, then I’ve got a way to tell who’s moving and who’s not. Now, it’s important to note that this is a postulate of the theory, not a consequence, but all experiments on the subject support it.

You mention that consciousness may be a fundamentally quantum phenomenon. Without debating the validity of that statement, it still wouldn’t have any bearing on the problem. Quantum mechanics is perfectly consistent with Special Relativity, which is what we’re discussing here. When exact results are important in QM, you do them relativistically, and the rules governing such behavior are well-known by physicists. It’s only when you get into General Relativity, which involves gravity, that you get problems with quantum mechanics.

mnemosyne, in order for a material to slow a tachyon down, it would first have to interact with it… Which it can’t do until it’s already been slowed down. Sorry.

18

Chronos

Two problems with this approach: (1) You’re using some physical device to measure time, which we already agree is invalid and (2) You’re using a subjective tool (survey) to make a measurement.

Einstein once wrote:

Not my theory, by-the-way. A number of experts on consciousness are postulating this theory. (Froehlich, Penrose, Hameroff, Globus, Jibu, Stapp, and others) I wouldn’t want you to think I was making this stuff up…

I believe you are mistaken (that’s about as polite as I can muster). Maybe you should look into Bell inequalities and EPR effects. I don’t want to get into a pissing contest, since this is veering off-topic…

19

Our units of time and distance are matters of definition, not axiom. Currently the meter is defined in terms of the second and the speed of light. No experiment can disprove a definition. The speed of light is constant by definition of the meter. The Michaelson-Morley experiment is the motivation for the current definition of the meter.

20

Well, yes, DrMatrix, but then the question becomes whether the meter is constant.

ACoverOfNoise, your objections aren’t valid. Of course I’m using a physical device to measure time… I can’t exactly ask God if I can sneak a peek at His wristwatch, can I? And surveying a group of people is a perfectly valid way to make a measurement, if the measurement you’re interested in is a psychological one (as in this case).