# An issue with length contraction

• I
• student34
In summary, when an object is at rest relative to you, you measure the length from the tip to the end to be ##L##. When the same object is moving relative to you, you measure the length from the tip to the end to be ##L'##, and ##L' < L.## Length contraction is not an illusion.
student34 said:
I just wanted to know if I was misinterpreting something about length contraction. Now I don't think I am.
Your post #68 strengthens the impression I expressed in post #57.

student34 said:
It is still sort of an illusion. The muon just takes a shorter route through spacetime to get to the ground.
Why would you call a shorter route an illusion? Is it also an illusion that it is shorter to drive from Miami to New York through Washington DC than through Denver? In what way is the word "illusion" appropriate here?

russ_watters
Ibix said:
Why is the green line more illusory than the blue one?
I meant that the length contraction for the muon's journey is an illusion, at least in the strict sense of the term contraction.

PeterDonis said:
Shorter compared to what?

There is no such object in the scenario. What's the point of this?
Shorter than compared to the slower object in blue.

student34 said:
I meant that the length contraction for the muon's journey is an illusion, at least in the strict sense of the term contraction.
No, it's just a different measurement. Again, you are focusing on the exact meanings of words in their general context, words that we repeatedly tell you are not and cannot be precise. The sooner you accept that the words are jargon and do not have their customary meanings, the sooner you can get on with learning relativity.

Dale said:
Why would you call a shorter route an illusion? Is it also an illusion that it is shorter to drive from Miami to New York through Washington DC than through Denver? In what way is the word "illusion" appropriate here?
If I am riding the muon from its resting point through its journey to the Earth, it is going to seem like the distance contracts for me once I start accelerating. But I am actually taking a geomterically different route than the route which I saw when I was at rest. It is an illusion for humans because we don't see the temporal dimension.

student34 said:
I am actually taking a geomterically different route than the route which I saw when I was at rest.
No, you are not. The muon's route through spacetime is an invariant.

student34 said:
I meant that the length contraction for the muon's journey is an illusion, at least in the strict sense of the term contraction.
In other words, we are right back to where we started with this thread. None of the discussion after 75 posts has made any impression on you at all. So what's the point of discussing?