# INTARESTIN DISCUSSHINS

General — Page [1] 2 3 4 5 6 7 8
Down Rodeo
Cap'n Moth of the Firehouse

2007 Oct 19 • 5486
57,583 ₧
Just like Mate de Vita said
Mate de Vita said:
You better!

I'm going to make a truck about it. So, SPECIAL RELATIVITY

You guys might not know a lot about this, but the question I am presenting is this: you are standing next to a barn and it is at rest relative to you. In the distance there is a stick. Previously you have measured the length of this stick while at rest relative to it and found it to be longer than the barn.

The stick is now moving towards the barn with constant velocity v which is a significant fraction of the speed of light such that relativistic effects are noticeable. From your perspective you perceive the stick to be contracted along the direction of its travel as predicted. At some point due to the stick's contracted length the barn doors are able to close entirely around the stick. Then both doors reopen and the stick flies out. At no point does the stick's velocity change.

If we now look from the stick's perspective the barn is moving toward us and therefore is contracted along its length. The stick is therefore far longer than the barn meaning at no point can the barn doors be closed around it, so my topic for discussion is: What the hell's going on? How do we resolve this paradox? I'll make a post explaining more of special relativity if you guys want. The wikipedia page might have the answer on it, but I'd like you guys to have a think about it.
 ≡ 2010 Sep 25 at 07:52 PDT — Ed. 2010 Oct 1 at 14:26 PDT
Mate de Vita
Kelli

2008 Oct 4 • 2453
159 ₧
The barn is travelling with a negative velocity (if the stick is travelling with a positive one), so it's expanding, not contracting.

No, in all seriousness though, I'm afraid this level of physics is a little out of my league, so I'll just leave it to the people who actually have a clue about Relativity.
...and that's the bottom line because Mate de Vita said so.
 ≡ 2010 Sep 25 at 08:16 PDT — Ed. 2010 Sep 25 at 08:17 PDT
Down Rodeo
Cap'n Moth of the Firehouse

2007 Oct 19 • 5486
57,583 ₧
Well, it's an interesting idea, but when you derive the maths that governs the contraction, you see a term v^2, so the negative doesn't matter. How might you resolve the paradox? We're not doing the maths or anything, we are THINKING ABOUT PHYSICS (that's a phrase that needs capitals).
 ≡ 2010 Sep 25 at 09:01 PDT
SRAW
Rocket Man

2007 Nov 6 • 2525
601 ₧
So the stick has eyes?
 ≡ 2010 Sep 25 at 18:12 PDT
Down Rodeo
Cap'n Moth of the Firehouse

2007 Oct 19 • 5486
57,583 ₧
No, we are standing next to the stick such that we perceive it to be at rest.
 ≡ 2010 Sep 25 at 18:46 PDT
Down Rodeo
Cap'n Moth of the Firehouse

2007 Oct 19 • 5486
57,583 ₧
Ok, it's been about 24 hours. Basically, the stick's viewpoint is that the shed doors open and close at different times. Each viewpoint is equally acceptable, there is no preferred rest frame. Isn't that weird and exciting?!
 ≡ 2010 Sep 26 at 17:00 PDT
SolidKAYOS

2007 Jun 24 • 84
68 ₧
Make awkward sexual advances, not war.
Down Rodeo said:
Dammit, this was the one place that didn't have this, but noooooo, molkman pisses all over that
 ≡ 2010 Sep 26 at 18:51 PDT
NatureJay
SJA: Commander of Ruthless Abuse

2005 Mar 22 • 1871
574 ₧
SolidKAYOS said:

Boy, wait until we start talking about clocks running faster at higher altitudes
100% natural, no antibiotics, and bloodgrass-fed
 ≡ 2010 Sep 26 at 21:26 PDT
Rockbomb
Dog fucker (but in a good way now)

2009 Nov 13 • 2045
NatureJay said:
SolidKAYOS said:

Boy, wait until we start talking about clocks running faster at higher altitudes

Wait, so you mean to tell me that a clock that if time were literally flying, that'd cause it to metaphorically fly?
Does this have something to do with thing at higher elevation moving faster than things closer to the core?

And DR, I think I'm just a little too tired to try comprehending your post, maybe I'll retry tomorrow
 ≡ 2010 Sep 26 at 22:13 PDT
SuperJer
Websiteman

2005 Mar 20 • 6311
I think the key to the problem is that there is no such thing as "two events occurring at the same time" when they are separated by space. At least in absolute terms.

Keep in mind also for this barn example to work, the whole thing has to happen in the tiniest fraction of a second. Any information at all travelling from one barn door to the other is going to take almost as long as it takes the stick to go through.

To put it another way, by the time the light from the one momentarily-closed door gets to the other, it's already open.

Or something like that.
 ≡ 2010 Sep 27 at 00:02 PDT
Down Rodeo
Cap'n Moth of the Firehouse

2007 Oct 19 • 5486
57,583 ₧
superjer said:
I think the key to the problem is that there is no such thing as "two events occurring at the same time" when they are separated by space. At least in absolute terms.

Yes! Well, kind of. Observers moving relative to one another will in general disagree about the simultaneity of events. At speeds where relativity kicks in of course.

RB, NatureJay is talking about General Relativity. Basically, masses warp both space *and* time with the result that clocks in a stronger gravitational field (or accelerating strongly) appear to tick more slowly. Sounds a bit esoteric but this result is necessary to make GPS work!

Finally this is all thought-experiment, so we're assuming that the doors work properly for our purposes and that. I'm a physicist, not a masochist.

In fact, you could kind of do it in an actual experiment by knowing the velocity of the stick in advance, then synchronising clocks at each door. You then know where the stick will be and when it will be there and can set the doors to open and close at the correct times. That way the stick will definitely "see" the doors opening and closing at different times.
 ≡ 2010 Sep 27 at 06:56 PDT — Ed. 2010 Sep 27 at 07:01 PDT
SRAW
Rocket Man

2007 Nov 6 • 2525
601 ₧
This stuff isn't even proven yet, that's why we call them theories, so no point to debate on something that isn't true
 ≡ 2010 Sep 28 at 00:18 PDT
SRAW
Rocket Man

2007 Nov 6 • 2525
601 ₧
This stuff isn't even proven yet, that's why we call them theories, so no point to debate on something that isn't true
 ≡ 2010 Sep 28 at 00:18 PDT
SRAW
Rocket Man

2007 Nov 6 • 2525
601 ₧
Wow I doubled post... chrome fail
 ≡ 2010 Sep 28 at 00:19 PDT
Mate de Vita
Kelli

2008 Oct 4 • 2453
159 ₧
SRAW said:
This stuff isn't even proven yet, that's why we call them theories, so no point to debate on something that isn't true

Who says it isn't true?
...and that's the bottom line because Mate de Vita said so.
 ≡ 2010 Sep 28 at 00:36 PDT
sprinkles

2009 Sep 6 • 2547
10 ₧
Down Rodeo said:
Finally this is all thought-experiment, so we're assuming that the doors work properly for our purposes and that. I'm a physicist, not a masochist.

No, but assuming you intended us to endure your big walls o' text could make you a sadist.
 ≡ 2010 Sep 28 at 02:12 PDT
Down Rodeo
Cap'n Moth of the Firehouse

2007 Oct 19 • 5486
57,583 ₧
@Sprinkles: Suppose.

Ok SRAW, if you want to be like that, we could admit that there are no "theories" as such, since the definition of a Mathematical theory involves some sort of irrefutable proof based on some set of axioms. However, we can only produce hypotheses that agree with experiment, that make predictions about our world. Either the theory predicts correctly and survives another day or it is wrong and needs to be modified. So far, Special Relativity has survived about 100 years, which isn't too bad.
 ≡ 2010 Sep 28 at 06:48 PDT
buq25

2008 Jul 5 • 583
295 ₧
NEAW INTRESTN DISISSUNS!

HOW IS THIS POSSIBLE?!!!

Edit: I presume that I should tell you that I knuw teh answur.
Today's post brought to you by the letter: "heck".
 ≡ 2010 Sep 29 at 11:47 PDT — Ed. 2010 Sep 29 at 11:50 PDT
Down Rodeo
Cap'n Moth of the Firehouse

2007 Oct 19 • 5486
57,583 ₧
Because the hypotenuses of both triangles are not single straight lines. Instead they deviate by a small amount; this actually equates to one square, allowing the block to be paradoxically rearranged.
 ≡ 2010 Sep 29 at 12:49 PDT
phoenix_r

2009 May 13 • 902
17 ₧
Down Rodeo said:
hypotenii

BOO
 ≡ 2010 Sep 29 at 14:41 PDT
Down Rodeo
Cap'n Moth of the Firehouse

2007 Oct 19 • 5486
57,583 ₧
 ≡ 2010 Sep 29 at 16:07 PDT
NatureJay
SJA: Commander of Ruthless Abuse

2005 Mar 22 • 1871
574 ₧
phoenix_r said:
Down Rodeo said:
hypotenoise

100% natural, no antibiotics, and bloodgrass-fed
 ≡ 2010 Sep 29 at 18:06 PDT
aaronjer

2005 Mar 21 • 4667
1,227 ₧
I prefer hypotenoi.
 ≡ 2010 Sep 29 at 21:23 PDT
Mate de Vita
Kelli

2008 Oct 4 • 2453
159 ₧
I myself am more a fan of hypothesis.
...and that's the bottom line because Mate de Vita said so.
 ≡ 2010 Sep 29 at 23:30 PDT