Impression of relative velocities

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Hi everyone,
This is just a random thought that popped up in my mind while I was travelling in train to my college
When we are inside a moving object and looking outside those thing that are near appears to move back(or move in opposite direction to that of our motion) with a same speed as ours but the farther object on the side(as seen through the window of the vehicle) seems to move a bit slower!
I have felt the same when looking to moon from a moving perspective, it seems the moon does not move.
I wonder how can these thing be explained!
 

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The angular velocity of objects (how fast they move through your field of vision) depends on the ratio of their speed and their distance.
Near -> large angular velocity
Far -> small angular velocity
 
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The angular velocity of objects (how fast they move through your field of vision) depends on the ratio of their speed and their distance.
Near -> large angular velocity
Far -> small angular velocity
Could you make it more specific. Will I be right to take the centre of rotation as the far point that I look at when considering the point about which it rotates!
 
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You are the center of the perceived rotation.
 
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You are the center of the perceived rotation.
Ohk, now that make sense
Thank you[emoji3531]
 
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  • #6
Janus
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For a visual representation, the black lines are your field of vision. Your motion is "downward" in the figure.
fov.gif

At first, both the distant and near object are in the center of your field of vision and along the same sight line.
At some moment later, you have moved to a new position relative to the objects as shown by the green arrow. The new sight lines to the objects are shown. Even though your relative motion and resultant shift in position relative to both objects is the same, the sight line to the nearer object has shifted more than the sight line to the further object. Extrapolating this forward and backward in time has the nearer object entering your field of vision well after, leaving it well before, and taking less time to cross your field of vision than the further object does.
 

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  • #7
A.T.
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...the farther object on the side(as seen through the window of the vehicle) seems to move a bit slower...
Do you understand why farther objects look smaller? The distance they move per time looks smaller for the same reason.
 
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For a visual representation, the black lines are your field of vision. Your motion is "downward" in the figure.
View attachment 237760
At first, both the distant and near object are in the center of your field of vision and along the same sight line.
At some moment later, you have moved to a new position relative to the objects as shown by the green arrow. The new sight lines to the objects are shown. Even though your relative motion and resultant shift in position relative to both objects is the same, the sight line to the nearer object has shifted more than the sight line to the further object. Extrapolating this forward and backward in time has the nearer object entering your field of vision well after, leaving it well before, and taking less time to cross your field of vision than the further object does.
This is more convincing and simple explanation
Thank you [emoji3531]
 
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Do you understand why farther object look smaller? The distance they move per time looks smaller for the same reason.
I guess that is because of the perspective,
I don't know whether I am right!
 
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[emoji846]
 
  • #12
sophiecentaur
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Hi everyone,
This is just a random thought that popped up in my mind while I was travelling in train to my college
When we are inside a moving object and looking outside those thing that are near appears to move back(or move in opposite direction to that of our motion) with a same speed as ours but the farther object on the side(as seen through the window of the vehicle) seems to move a bit slower!
I have felt the same when looking to moon from a moving perspective, it seems the moon does not move.
I wonder how can these thing be explained!
No one seems to have introduced the term "Parallax" yet. That's the normal way that these strange effects that we see when moving on trains etc.. A search on the term will give you plenty to think about and many explanations.
 
  • #13
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No one seems to have introduced the term "Parallax" yet. That's the normal way that these strange effects that we see when moving on trains etc.. A search on the term will give you plenty to think about and many explanations.
How parallax is getting connected with this phenomenon! [emoji848]
 
  • #14
sophiecentaur
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How parallax is getting connected with this phenomenon! [emoji848]
I suggest you read about parallax and then you will find out. It is the best explanation of the effect you get on a train and the same effect is used in calculating the distance to stars.
Good old Wiki will tell you all about it.
 
  • #15
George Keeling
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At first, both the distant and near object are in the center of your field of vision and along the same sight line.
At some moment later, you have moved to a new position relative to the objects as shown by the green arrow.
Janus's diagram also (nearly) shows why very distant objects such as the Sun or Moon do not appear to move at all. They are almost at infinity, so the line of sight remains in the same position. I remember asking my father this very question when I was small and staring out the car window. Trees flashed past but the Sun was steady. His correct explanation went over my head.:cry:
 
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