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# Time travel quiz

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I don't know how old the Time Travel quiz is, but it just came up when I logged in, so I took it. I missed one question (I believe that gave me 14 out of 15 correct, or a score of 530 out of a possible 550). But I disagree with some of the answers.

One question asked whether Einstein's E = mc^2 allowed time travel into the past for object, for things moving faster than light, or didn't prohibit it (I can't remember the exact possibliities). E=mc^2 does none of those. E = mc^2 isn't about time travel, it's about the equivalence of energy and mass. Unless someone can explain an obvious link between the two things, it's kind of like asking if y = mx + b allows parabolas to be concave up. This is the one question I missed (on the first try - I chose the "correct" answer on my retry).

Another question asked how we can tell that gravity dilates time. The "correct" answer was that clocks tick more slowly in an airplane than on the ground. That's backwards. The greater the gravitational field - which would be here on Earth - the slower clocks will tick. The airplane experiment with atomic clocks mixed special and general relativity: general relativity in that the plane was farther from the center of the Earth - speeding up the clock ticks relative to someone at rest on the surface - and special relativity in that the airplane was traveling through space - which would slow down the clock ticks relative to someone at rest on the surface of Earth. I guessed which of the wrong answers was supposed to be the correct one and got it "right".

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Okay, I better answer this since I wrote the quiz (it was a while ago, though).

1) E=mc^2 does not *prohibit* time travel, and that was the point here. I have lost my original sources for this quiz but I used a page similar to this:

http://www.iep.utm.edu/t/timetravel.htm

There are two sections on relativity (special and general) which cast some light on the issue.

The question was based on a recent discussion about tachyons (hypothetical particles moving faster than light) and was related to E=mc^2. Sorry about being so unclear...

2) The second one was taken from the book, "How to build a time machine" by Paul Davies. The question is simplified, and in fact the answer is partly correct (clocks either slow down or speed up depending on whether the plane moves eastward or westward - showing time dilation). Time dilation WAS at first proved using atomic clocks on airplanes, so maybe I just need to drop the second part of the option.

http://hyperphysics.phy-astr.gsu.edu/hbase/relativ/airtim.html#c3 -> details on the experiment.

The quizzes are always popularized because most people take them just for fun. If you find errors I would also appreciate suggestions for alternative answers. I'm not infallible, you know.

And...just for the record...the quiz has been taken more than 5,000 times and nobody has complained about it before. But I may still be wrong, of course.

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Originally posted by: TormodAnd...just for the record...the quiz has been taken more than 5,000 times and nobody has complained about it before.

This post doesn't have any kind of scientific nature, but I had never let pass a sophism without pointing it. This is a "call to tradition". It isn't because no one ever complained that someone complaining will be wrong about it. *bows humbly* Sorry for the disturbance. I just dont like sophisms.

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History, the point was of course that even though the quiz has been taken many times, this is the first time I was told there might be problems with it. Like I said, I'm not infallible and appreciate feedback. So I humbly think your "sophism" comment is a bit misdirected.

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• 2 weeks later...

I was wondering where I could find this time travel quiz? It seems really interesting!

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Here are two tips (looking for a quiz? Work for it!)

1) There is a mysterious page called our "Front page" at http://www.hypography.com/

2) There is an even more mysterious and even baffling service called our "Search Engine". Try putting the words "Time Travel Quiz" in there for a magical journey.

...or, of course, just click on this maddeningly obvious link : http://www.hypography.com/quiz.cfm?id=32409

Tormod

hehe thanks