# Sisyphus

Senior Members

6185

1. ## Distance and space expansion

In one million years, the galaxy will be more than 1G lightyears away, because the amount of space in between them will have increased in the meantime, even if they are not moving relative to one another. That's what the expansion of space means.
2. ## If there is no end to the space

If I may, Owl gave a spatial distance between the Earth and the Sun, two locations in space. The invariant spacetime interval that Iggy is talking about is between events, i.e. particular points in space and time. Since the Earth and the Sun are not events, the equivalent value that you are asking for does not exist. If you specify locations and times in a given reference frame, then you could get a value with this formula: s^2 = -(ct)^2 + d^2, where t is the time elapsed between the events and d is the distance between where they happened. In a different reference frame, t and d will both be different, but s will be the same. Please correct me if I've misunderstood the misunderstanding - I've just been skimming the last few dozen posts.
3. ## Magnets, how they work

What do you think the difference is? Give an example. (Also, there's a great deal we don't know about how nature works, even with a generous usage of "know.") I know that you're being sarcastic, but that's actually true. Why is a silly question when there's no meaningful answer. But if by "why" you just mean "what is happening," then it's always interesting if you go deep enough.
4. ## Magnets, how they work

"Why does the nail stay in the wood?" "How does the nail stay in the wood?" "What is happening when the nail stays in the wood?" Since a final cause agent would indeed be a silly addition, I would just assume those three questions are soliciting the same type of response (or responses, as the case may be). In cases that don't involve intent (like with nails, or magnets), either there is no distinction between "why questions" and "how questions," or "why questions" are meaningless, depending on how pedantic you're willing to be.
5. ## Magnets, how they work

What do you mean by that?

Boats?
7. ## Magnets, how they work

Indeed, he says it's an excellent question, just one that's not as straightforward as it seems, because it's difficult to answer in a way that people find satisfying. "Because she slipped on the ice" is, objectively speaking, a much vaguer explanation than "because magnets repel," but people find one more satisfying than the other on the basis of familiarity alone. Not on the strength of the explanation and not because it's fundamentally better understood - as he shows, if you keep asking "why" in the hospital scenario you quickly leave common knowledge again ("why is ice slippery," etc.). And so, in order to reach that goal of "satisfying" to the reasonably intelligent layman, you have to explain many, many other things first, which causes frustration and suspicion that the explainer doesn't actually know what he's talking about. "Just tell me!" "Tell you what, exactly?" Oh, and for those who missed the reference, "f***ing magnets, how do they work" was recently an internet meme tied to this phenomenon, and it comes from an Insane Clown Posse song expressing rage towards "lying" scientists: http://knowyourmeme.com/memes/fcking-magnets-how-do-they-work
8. ## Why are homosexual/polygamous marriages illegal in so many countries?

Corinthians is the words of St. Paul. Not Jesus. Jesus only gets lines in the gospels.
9. ## Magnets, how they work

Explaining how magnets work to someone who is not already scientifically literate is like explaining why your aunt is in the hospital to an alien from another planet.
10. ## Why are homosexual/polygamous marriages illegal in so many countries?

Well, I just read these: http://en.wikipedia.org/wiki/Polygamy http://en.wikipedia.org/wiki/Same-sex_marriage Interesting stuff. It seems that historically, polygamy has been more prevalent than monogamy. ("Of 1231 societies noted, 186 were monogamous. 453 had occasional polygyny, 588 had more frequent polygyny, and 4 had polyandry.") That monogamous cultures now dominate can apparently be traced to medieval Christian theology, and the rest is just tradition. Same-sex marriage has been very rare before modern times, but not entirely unprecedented. It was outlawed in 342 in Rome, again because of Christian theology, which saw the primary purpose of marriage as reproduction. I'm guessing that's probably a common theme even among cultures tolerant of homosexuality - that they just wouldn't use the same word to describe a homosexual partnership. As for the legality question, my answer is the same in both cases. I don't think the state should be needed to grant permission for marriage in the first place. You don't need a "best friend license," and you shouldn't need a "marriage license." I realize this would require substantial changes in the legal system, with things like the right not to have to testify against a spouse, etc. As for what causes homosexuality, I honestly don't know if figuring out exactly what causes it would make a difference to the public. For myself, I don't really care. My condoning it does not depend on what causes it.
11. ## What's the best time to marry?

And that makes this an ethical question how?
12. ## What's the best time to marry?

Why is this in ethics?
13. ## Why does the light travel at precisely the speed...

http://en.wikipedia.org/wiki/Speed_of_light#Measurement That includes three different astronomical methods. The simplest, now that we have space probes all over the solar system, is to simply time a signal between them. There is also a separate article on Ole Romer's initial calculations based on the relative velocity of light, Earth, and Jupiter, as evident by anomalies in the observed transit times of Jupiter's moons: http://en.wikipedia.org/wiki/R%C3%B8mer%27s_determination_of_the_speed_of_light
14. ## If there is no end to the space

And when you step on the bus, it has the minimum observable kinetic energy: zero. And it has the minimum velocity, etc. A frame in which an object is at rest is going to be a limiting case in several ways, because there is no such thing as negative velocity. However, if you think all other measured properties are somehow illusory, I once again invite you to step in front of a speeding bus to test that hypothesis. There is "one reality." And in that reality, things like length, duration, velocity, etc. are dependent on reference frame. If you can't come up with a reason for why you have a problem with some of those properties (like length) but not others (like velocity) besides that it "looks like total crap," then there really isn't anything left to discuss, is there?
15. ## Relatively confused

To spell it out: In frame in which A is at rest, time is passing more slowly for B. In the frame in which B is at rest, time is passing more slowly for A. It sounds in impossible, I know, but it actually does work out.
16. ## If there is no end to the space

But quantity of money is not frame-dependent. It's not even physical. Velocity clearly is.
17. ## diagram one

I'm not sure what you mean by events popping from nowhere.
18. ## diagram one

Not by that route, no. In practice, yes, of course. If you're looking at something through a telescope, then technically you're observing something in the interior of the light cone. The light slowed as it passed through the atmosphere, and it reflected back and forth in the mirrors of the telescope before it reached your eye.
19. ## Contradictions: Religion vs Science

Sure it does. You can argue that it's not intended to be believed as written, but that it is what it says. That's what "literal" means.
20. ## diagram one

Sure, assuming the light is only traveling through total vacuum in a straight line. That is the fastest possible route for information.
21. ## diagram one

What's the distinction? You're receiving information about the event. The boundary of the light cone represents the farthest/soonest it is theoretically possible to receive the information. Therefore, events inside the cone can be causally connected to the observer, those outside cannot.
22. ## If there is no end to the space

Oh, but it is.
23. ## If there is no end to the space

And how does it exert that force, if it has no kinetic energy?

We sure can:
25. ## If there is no end to the space

It's special in that it's the rest frame. It's not special in that it's somehow more real. The bus speeding down the street has a rest frame, too. In that rest frame, it has zero kinetic energy. In yours, standing on the sidewalk, it has a lot. Step in front of it, and then tell me frame dependent properties are just an illusion.
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