Naked Science Forum

Non Life Sciences => Physics, Astronomy & Cosmology => Topic started by: jayesh on 27/01/2009 11:47:04

Title: Star movement viewed from earth
Post by: jayesh on 27/01/2009 11:47:04

Hi There,

Why we see stars moving with us when we walk ?

Thanks.

Jayesh.

Title: Star movement viewed from earth
Post by: Vern on 27/01/2009 11:55:27

Stars are so far away that the angle between you and the star does not change; the angle between you and things close by do change noticeably.

Title: Star movement viewed from earth
Post by: Chemistry4me on 27/01/2009 21:57:27

Are you sure that it wasn't an artificial satellite?

Title: Star movement viewed from earth
Post by: DoctorBeaver on 27/01/2009 22:54:41

Just to expand on what Vern said. The change in angle is so minute that we don't notice it. It's called parallax and is the method used to calculate the distance to some stars. The star is viewed twice, 6 months apart so there is maximum difference in the position of the Earth in its orbit. The difference is observational angle of the star can then be used to triangulate to get the distance.

Title: Star movement viewed from earth
Post by: Madidus_Scientia on 28/01/2009 05:40:32

Like when driving along a highway and the trees whiz past, but the far mountain only moves very slowly. The very very very very very very very very very very very far stars seem not to move at all.

Title: Star movement viewed from earth
Post by: jayesh on 28/01/2009 07:26:29

Quote from: Madidus_Scientia on 28/01/2009 05:40:32

Like when driving along a highway and the trees whiz past, but the far mountain only moves very slowly. The very very very very very very very very very very very far stars seem not to move at all.

Thanks and it is true,but what I was asking taht unlike mountain which loks stationaty star seems to be moving with us and that is what exactly I want to know.
Thanks Again.
Jayesh.

Title: Star movement viewed from earth
Post by: DoctorBeaver on 28/01/2009 15:18:32

Jayesh - to follow up on Madidus's analogy:-

The further away something is, the slower it will appear to move relative to the observer. Imagine moving the muntains further & further away. Their movement to the observer will seem to get slower & slower until they appear to moving at the same rate as the observer rather than falling slowly behind.

Title: Star movement viewed from earth
Post by: dentstudent on 28/01/2009 15:32:49

And from DB earlier, here is some info on parallax (http://en.wikipedia.org/wiki/Parallax#Stellar_parallax).

Title: Star movement viewed from earth
Post by: Vern on 28/01/2009 22:41:55

Quote from: Madidus_Scientia on 28/01/2009 05:40:32

Like when driving along a highway and the trees whiz past, but the far mountain only moves very slowly. The very very very very very very very very very very very far stars seem not to move at all.

And since the stars don't seem to move at all relative to you, you see them as moving along with you.