# How does the world look like after a Lorentz transformation?

1. Mar 18, 2013

### nick41

I would like to get a detailed description, how the world looks for a moving observer in Special Relativity compared to the way it looks for an observer at rest. Do you know any reference, where I can find such a description? Can you maybe even tell me, where to find two pictures of the sights of both observers?

2. Mar 18, 2013

### ghwellsjr

A Lorentz Transformation does not in any way affect what any observer sees.

3. Mar 18, 2013

### nitsuj

Oh Compared to, yes of course.
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Plenty of examples.

Last edited by a moderator: May 6, 2017
4. Mar 19, 2013

### DimReg

Go for a jog, and look at things around you. You've applied a lorentz transformation to yourself and you can see how it looks different. ;)

At faster speeds, things might look shorter in the direction of travel, because they are lorentz contracted. But note that only relative speeds matter, if you start running with a meter stick in your hand it wont look any shorter.

5. Mar 19, 2013

### ghwellsjr

Where is the Lorentz Transformation in this scenario? Remember, a Lorentz Transformation changes the coordinates of events which is information not available to any observer and doesn't in any way affect what an observer sees.
You won't necessarily see things looking shorter just because there is a fast relative speed between you and the object. The images of objects get blue shifted as you/they approach each other and change to red shifted as you/they pass each other but the visual shapes of objects is a very complicated subject and has nothing to do with a Lorentz Transformation.

6. Mar 19, 2013

### DimReg

The lorentz transformation is a boost... You start out not running, then later you are. I thought that was clear. And yes it does affect what an observer sees: before the boost some things will be at rest, and after they will be moving. While the coordinate aspect of lorentz transformations is not measurable, non lorentz invariant quantities (such as energy) do change under lorentz transformations, so you can't claim that lorentz tranformations don't affect what an observer sees.

Ok, I did say that you "might" see things get shorter. Judging by the question of the OP, I don't think he's completely comfortable with special relativity, so I don't see the point in making my answer as complicated as possible. I tried to give a simple version of what goes on, and not bother the OP with issues like red shift and blue shift, so he can focus on what he want to know.

My point about going for a jog wasn't that you'd notice lorentz contraction, but that there is nothing unusual about lorentz transformations, and they don't change the way the world looks in an exotic way.

7. Mar 19, 2013

### ghwellsjr

Before and after the boost, different things are at rest and different things are moving according to the IRF but relative speeds between objects remain the same in all IRF's. Therefore, what an observer sees is not affected by transforming to a different IRF.
No Lorentz variant quantity is in any way visible to any observer. And any measurement or derived calculation that any observer determines for these Lorentz variant quantities come out the same for him when you transform to a different IRF.
Unfortunately, when an OP who is uncomfortable with Special Relativity asks a confusing or disjointed question, it is impossible to determine what he wants to know. But that is not an excuse to give him wrong information. It's wrong to tell him that a Lorentz Transformation changes what he sees, measures or determines.
They don't change the way the world looks to any observer in any way. That's the whole point of Special Relativity, all IRF's are equally valid, none is preferred.

Last edited: Mar 19, 2013
8. Mar 19, 2013

### nitsuj

Also, SR doesn't account for an eyeball & memory, or it being a continuum.

I don't know SR well enough to envision all comparative situations.

But, Doppler is easy enough to visualize.

And there is even that MIT game A Slower Speed of Light.

(assuming this thread is about the visual relativistic effects as seen in the game)

Last edited: Mar 19, 2013