# List of common misconceptions about relativity?

#### bahamagreen

You are going to use student group discussions leading to their presentation...

The concept problems will involve the most students (with their varying experience) if the issues are simple to grasp, foundational to relativity, and yet tough enough to challenge them...

Is there absolute motion?
If two objects are in relative motion with respect to each other, can't we conclude that at least one of them must be in some kind of absolute, true, or real motion?
Won't this hold true for any and all possible frames of reference?

Is relativity "real"?
Is relativity a theory of measurement, or a theory of existence?
Is it just a way to transform data from a distant/fast source into what makes sense to us locally, or does it actually describe the distant/fast situation?

How does gravity get out of a black hole?
How is there gravitational attraction outside of the black hole?
If it comes from inside the event horizon, how does it get out?
If from outside the event horizon, where is the source mass?
Does gravitational attraction pass through a black hole from one side to the other, or is it blocked?

Why aren't photons allowed to carry flashlights?
Why is there no inertial frame of reference for c?

#### zonde

Gold Member
Is aberration classical or relativistic effect?

#### PAllen

Is aberration classical or relativistic effect?
Both. It has a derivation according to:

(1) corpuscular theory
(2) moving aether theory
(3) relativistic derivation

They don't agree exactly, but (last I knew) the differences were actually too small to detect.

#### rjbeery

For a myth, how about "SR has proven the aether does not exist." I'm not advocating for aether, but there's a big difference between proving that something cannot exist in a theory versus merely acknowledging that it isn't necessary in that theory.

#### zonde

Gold Member
Right. It's just that aberration is usually explained classically but for me it was quite enlightening to find out how it can be worked out in relativity.

#### zonde

Gold Member
For a myth, how about "SR has proven the aether does not exist." I'm not advocating for aether, but there's a big difference between proving that something cannot exist in a theory versus merely acknowledging that it isn't necessary in that theory.
As I see this is rather complicated question. Obviously it's a myth. But at the time people where probably hung on the idea of finding preferred frame. So such a myth would ban useless discussions.
But nowadays I would say that such a myth promotes kind of magical thinking. That's because dimensional modelling is very powerful tool for consistency checking but that myth kind of prevents using it. But that's my viewpoint.

#### zonde

Gold Member
And another thing that I considered quite interesting (somewhat related to relativistic interpretation of aberration). This is actually a paradox kind of thing but it of course is related to some misconception (if you have it).

Let's say we have situation like this:

Observers "1" and "2" are observing box with an "A" printed on it's side. We view this situation in rest frame of the box and first observer. Second observer is in motion in that frame. Neither observer can see the "A" on the side of the box when both observers are side by side.

Now let's change to rest frame of second observer:

The box and first observer is in motion in that frame. Because the box is in motion and light doesn't get to observer instantly second observer see the box in it's past position. So should the "A" be visible for him?

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