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Hello! I am a brand-new member here (please be gentle and basic).

I have been listening to a course on special relativity and general relativity—the lecturer is Dr. Richard Wolfson. I have no serious mathematical background but would like to have a much better conceptual understanding of physics since Einstein. In any case, Dr. Wolfson uses the following as an example of the twins paradox:

**One twin remains on earth, while the other twin travels to and back from a nearby star (10 light years away from earth) and is moving at 0.8c.

**While the twin on earth experiences an elapsed time of 25 years, the travelling twin only experiences 15 years of elapsed time.

**So, the travelling twin returns 10 years younger than the twin who remained on earth.

Given this (and I assume it is accurate), I hope that someone might offer me some direction (or correction) concerning my questions below, some of which are very basic in nature.

Thanks for any help!

1) Concerning the example of the twins (one travels to a star and back; one remains on earth), why is the travelling twin (who ages less) to be thought of as moving into the future? Somehow to me, it seems that with that twin being younger, then she would have moved more slowly in time. I am sure that I am missing the obvious here.

2) When an object approaches the speed of light (let’s use the spaceship example again), does only that object experience time dilation? What if there were debris that got caught up in the motion (like dust behind a car)? I take it that, for a brief time (while the debris is at the same speed as the spaceship), the debris would experience time dilation the same way (?). But, as the debris slowed down (changes frame of reference), it would begin to experience a lesser degree of time dilation, right? It seems like that, if we think of each frame of reference (differing speeds), then the spaceship, the debris, and the debris in different frames or sort of wrapped in their own little bubble (or universe?). I am struggling here, but is it fair to say that if we could measure precisely enough and found that almost all objects are moving at slightly different speeds (and with associated effects of time dilation), then all objects would truly not be in the same universe (at least along the lines of time and maybe in terms of space too given what I have just heard about contraction)? It seems as if “the” (wrong word?) universe would become multi-layered in all directions. Maybe there are multiple universes? (Especially if we break speed down in the sort of fashion found in Xeno’s Paradoxes.)

3) What if “inside” the spaceship, I (somehow) throw another object at near the speed of light? Does this create dilation within dilation?

4) I am interested in the concept of “emergent properties.” If from our perspective (not sure that this is even logically possible), we were monitoring several spaceships, say one moving .0001 of the speed of light, one at .001 the speed of light (etc.), until we get to one at .900 the speed of light (and imagine many ships and many gradations of the speed of light); then would we see different things? That is, would we see younger pilots (dilation) or shorter ships (contraction)? If we could monitor one ship that started slowly and then moved towards the speed of light (acceleration), then what would occur? What would we see? If so, at what fraction of the speed of light, would these changes be apparent to human beings?

5) What if an object goes the full speed of light? Can an object go faster than the speed of light?

I would deeply appreciate any help! I am virtually certain that I have at least one foot still planted firmly in Newtonian physics.

Take care.

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# Dilation & Contraction-First Post

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