Science a GoGo's Home Page Forums General Discussion General Science Discussion Forum i just duno why you can't observe light speed as half c

then explain why the person going on a high c fraction ship would return younger than his brother. its not an illusion. time does slow down for him, which means that from his perspective the universe speeds up. when he slows down at the end, the universe appears to slow down to normal, but it is really his time that is changing.

then explain why the person going on a high c fraction ship would return younger than his brother. its not an illusion. time does slow down for him, which means that from his perspective the universe speeds up. when he slows down at the end, the universe appears to slow down to normal, but it is really his time that is changing. [/QUOTE]

We have both posted. Mine is just before yours (see above).

Time only actually slows down within his reference frame when the spaceship accelerates and decelerates. In order to compare the ages of the two, the twin who left has to return to earth so that their ages can be compared relative to a single reference frame. The twin who has left had to accelerate to get away and to decelerate in order to return. Therefore, he will be the younger one.

If it were possible to leave with near light speed without acceleration, and the twins communicate by radio all the way, then both will conclude that they are ageing faster than the other twin. It is strange that this should be so; but, as mentioned above, both are experiencing an "illusion" within their respective reference frames of what is happening in their brother's reference frame. If, however, each twin corrects for the time he observes within the other twin's reference frame, as we are doing for the GPS satellites, they will find that they are actually ageing at exactly the same rate.

Hi JB:

I think I am still on topic to ask for your comparison of time passing. It seems to me we have time as an objective circumstance measured for dates and such by the rotation of the earth and then we time as an organic event. We get old independently of the earths rotation or the speed with which it orbits the earth. Possibly the drag of gravitation on our bodies provides some contribution as well.

When you quote an interpretation of Einstein and aging factors with acceleration by what means is our organic aging going to be restrained or accelerated as a result of moving through space? This has always been a curious suggestion to me.
This as an organic result needs something more than math to make it work. What can be shown to be going on in the body to age slower or faster?
jjw

Yes fascinating questions! According to special relativity (not considering gravitation), time is the fourth dimension. Thus it is an integral part of our four-dimensional universe and should thus manifest within every inertial reference frame at the same rate (the "proper rate"). In fact if this were not the case, estimations of the "age of the Universe" would have been futile. If time varied as a consquence of the speed you are moving at, the Universe would have different ages relative to different galaxies. Furthermore, the line widths of spectra will be different for materials moving relative to each other. The Universe would have been chaotic when being observed. Thus the contraction in time observed by an observer (considering himself to be stationary) within a reference frame moving relative to the observer is, as I have pointed out, a relativistic "illusion".

Thus a human being on another planet exactly like the earth but moving relative to earth with a high speed will still age at the same rate as he/she would have on earth.

From Einstein's general theory of relativity one finds that acceleration (which can be equated to gravity) causes actual time to slow down; for example at the event horizon of a black hole time supposedly stops completely. I sometimes speculate that the event horison is not a cloak of a singularity but rather the gateway to eternity. Thus if you can travel to end up near an event horison, you should actually age slower; i.e. all the time-related processes in you body should slow down. It might be a very boring and sad existence. Everything will be happenning in slow motion. On the other hand, if everything slows down , also you bodily functions and your thought rate, you might not notice the difference (except of course the massive gravitational force which you have to counteract not to fall "into" the black hole).

An interesting question: Can change occur (i.e. entropy change)within an Euclidean space-time. If it is truly Euclidean, the time axis will be perpendicular to the space axes so that any time-derivative will always be zero; nothing should then be able to change with time. I speculate that "our Universe" came into being when the fourth axis of an Euclidean (timeless; zero entropy) space-time became bent so that time and light started to manifest within three-dimensional space. Maybe our Universe is expanding because it is unbending to eventually again become a space-time with zero entropy.

Thank you JB.

It all sounds good but I get involved with details. Medical people tell us an adults person has a heart beat (pulse) of between 60 and 100 per minute. A trained athelete has a pulse between 40 and 60 per minute. Astronauts are in pretty good shape so let's assume an average of 60 perminute, the equivalent of 1 per second.

When things begin to slow down for our traveler at what point will the system be prone to fail. If we slow the ageing by 50 % does that mean a pulse of 30 per minute? A theory that touts the slowing of aging by acceleration or location must be quantified to provide the participants with some remaining life force to survive and continue. I am aware yhay I am baiting the question but it does seem to me that we are being in "very general relativity" with concepts like this one. Cheers.
jjw

The way I see it is that time is measured by change. There are now two possibilities: 1. that life functions do not slow down when time slows down and then your question is valid; 2. that everything slows down in concert so that we are not aware of the fact that we are living in slow motion relative to another reference frame.

It will be interesting to find out which is which. Point 2 might be correct. On the other hand when subjecting ourselves to a huge increase in gravity for a long time in order to slow time down, will probably kill us. This would indicate that point 1 could be correct. At least we know that when two persons are moving at a high speed relative to each other, the time rate each experiences IS THE SAME. Time dilation in this case is observed by each observer when he views the other observer. As I have said it is a kind of "illusion".

Have you considered the case where the twin who is leaving (on average) accelerates at a rate that is less than gravitaional acceleration on earth and comes back by decelerating at the same rate. The twin who has left will then have experienced an average effective gravitational field that is less than what the twin on earth has experienced. This will then imply that the twin that has left could be older than the twin who stayed behind. maybe this is not possible when taking into account that the twin travelling from earth first have to break free from earth's gravity. I have not yet made a full analysis; but raise this possibility because it is amusing.

Thanks again. I appreciate your response.

I think my point is that we are aware and will be aware of organic time. Taking Kepler literally we know that planets in orbit around the Sun following an elliptic path are sometimes traveling as much as 10 times the velocity as they are at other times. Extreme orbits such as that of Pluto should provide an example of this.
We do not generally feel any effects of this common acceleration that occurs at least once in every eliptical orbit. I suppose the speed is not significant in this example because it is not fast enough. That, I hope, will focus my issue. If the basic premise is correct then to me any acceleration should be meaning full. The highest speed is at the lesser axis so it is of short duration compared to the major axis. The Earths orbit is not extreme but the speed difference is still present.

So, "organically" I do get the feeling at times that the day is shorter or possibly longer, and that should qualify me for the DKV award.
jjw

Interesting viewpoint to ponder on. The effects that acceleration and deceleration has when the earth follows its elliptical orbit is probably negligible compared to the earth's own gravity. In fcat it must be so or else we should have picked it up on our bathroom scales.

Not quite:

The scale might tell you if you dropped a pound or two. It would not tell you if you lost an hour or two. Great fun.
jjw