Jump to content

Walking on the Moon

Stationary stars?


discovered799
 Share

Recommended Posts

Everything in the entire universe is in constant motion. The ratio of their relative motion to their distance from our point of observation is so small that their movement is imperceptible from day to day. Because of that, we can use parallax to determine their distance, within some margin of error, by taking angular measurements from opposite sides of the planet and from different positions in our orbit around the sun.

Edited by Buzzard75
Link to comment
Share on other sites

Parallax is measured over period of time using astrometric measurements relative to more distant stars - or their "average" position. All the stars orbit galactic center but have local velocity components as well.

Stars further away move much less (they move on average the same, but angular motion is much less due to their distance), and if we take their average position, most proper motion components will cancel out. Compared to this we measure parallax and proper motion. Using spectrometry we can measure star motion along the line of sight (Doppler shift of spectral lines). So we can determine both speed and direction of star "in celestial plane", and along line of sight - thus giving us full 3 component vector of stars velocity relative to Sun.

Measurement of parallax looks something like this:

image.png.95d13bed6e199d2c0d4d654d93d2e351.png

Blue line represents star motion "across" the sky, while wobble represents parallax. For further info please look at this paper:

http://www.princeton.edu/~rvdb/tex/BarnardStar/BS.pdf

 

  • Like 1
Link to comment
Share on other sites

Stars further away move much less

 

\!/__________________________________________________

 

I soat da parallax was based on the stars of the celestial universe da a stationary. Is not but you are saying a contradiction is in fact or da facing value of za say? No yes oui oui.

Link to comment
Share on other sites

1 minute ago, discovered799 said:

Stars further away move much less

 

\!/__________________________________________________

 

I soat da parallax was based on the stars of the celestial universe da a stationary. Is not but you are saying a contradiction is in fact or da facing value of za say? No yes oui oui.

No parallax is not based on things being stationary. It is usually explained in terms of stationary things, but it also works with things that are in relative motion, you just need to account for that relative motion in order to get correct results of measurement.

Link to comment
Share on other sites

19 minutes ago, discovered799 said:

Everything in the entire universe is in constant motion.

 

\?/______________________________________________________________

 

 

Does dat mean dat I gota buy a new planisphere to zee in stars?

Yes, roughly every few thousand years you should get your self a new planisphere just to be up to date. oui oui

  • Haha 2
Link to comment
Share on other sites

55 minutes ago, vlaiv said:

Yes, roughly every few thousand years you should get your self a new planisphere just to be up to date. oui oui

And keep updating your 'favorite' planetarium program(s) too. :hiding: 

  • Like 1
Link to comment
Share on other sites

 

1 hour ago, discovered799 said:

Stars further away move much less

Ooh la la

SheepSmall.gif

Complicated, but interesting. I think the same is true for people on the beach.

 

Edited by Ruud
Link to comment
Share on other sites

24 minutes ago, Ruud said:

 

Ooh la la

SheepSmall.gif

Complicated, but interesting. I think the same is true for people on the beach.

 

In all fairness, that was quote from my post, a bit out of context

Link to comment
Share on other sites

37 minutes ago, ollypenrice said:

Of course there are philosophical questions, too. If the universe contained only one particle, could that particle move?

Olly

Hey, it's Friday! Don't make my head start hurting with thought exercises right before the weekend.

  • Like 1
Link to comment
Share on other sites

1 hour ago, ollypenrice said:

Of course there are philosophical questions, too. If the universe contained only one particle, could that particle move?

Olly

That's too easy! Real question is could it spin? :D

 

Link to comment
Share on other sites

19 hours ago, ollypenrice said:

Of course there are philosophical questions, too. If the universe contained only one particle, could that particle move?

Olly

That's easy.  It's an impossible question.  If you assume a point like particle (so hence only one) - lets assume a photon.  Then we can postulate the following:-

As there is only one particle there is no method for measuring distance, as fundamentally distance has to be defined by the distance between at least two objects.
As there is only one particle there is no method for measuring time because fundamentally that requires being able to measure an action (which requires measuring between two objects).

Hence it is impossible to know

Link to comment
Share on other sites

8 minutes ago, Whirlwind said:

That's easy.  It's an impossible question.  If you assume a point like particle (so hence only one) - lets assume a photon.  Then we can postulate the following:-

As there is only one particle there is no method for measuring distance, as fundamentally distance has to be defined by the distance between at least two objects.
As there is only one particle there is no method for measuring time because fundamentally that requires being able to measure an action (which requires measuring between two objects).

Hence it is impossible to know

Is it merely impossible to know, or is the movement of a unique particle impossible since movement describes a change in the distance between two particles?

Olly

Link to comment
Share on other sites

On ‎14‎/‎04‎/‎2018 at 12:44, ollypenrice said:

Is it merely impossible to know, or is the movement of a unique particle impossible since movement describes a change in the distance between two particles?

Olly

It is impossible to know, it would be a metaphysical concept.  Everything is relative, with only one absolute particle there is no way to measure anything.  The concept of time, speed, temperature and distance wouldn't even exist in such a universe.  

  • Like 1
Link to comment
Share on other sites

You start off with a particle that is spinning, remove everything else in the universe without changing the state of your spinning particle. Your particle is still spinning as you did not change its state, if it is not then you did change its state  - shame on you. :) 

Jim  

Link to comment
Share on other sites

So how would you measure that spinning particle. How would you instantaneously destroy everything in the universe without any signature left behind?  How do you know that in removing everything else in the universe that stopped the particle spinning if you have nothing to measure it against?

Link to comment
Share on other sites

On 4/15/2018 at 19:37, saac said:

You start off with a particle that is spinning, remove everything else in the universe without changing the state of your spinning particle. Your particle is still spinning as you did not change its state, if it is not then you did change its state 

So many issues

If you remove everything from the universe, where do you leave it?

And when you're done you have removed yourself. There will be nobody left to study the particle.

Link to comment
Share on other sites

49 minutes ago, Ruud said:

So many issues

If you remove everything from the universe, where do you leave it?

And when you're done you have removed yourself. There will be nobody left to study the particle.

Hey those are mere details, I'm an ideas guy - big hand small map. :) 

Jim 

 

1 hour ago, Whirlwind said:

So how would you measure that spinning particle. How would you instantaneously destroy everything in the universe without any signature left behind?  How do you know that in removing everything else in the universe that stopped the particle spinning if you have nothing to measure it against?

And that's what you have difficulty with, to be honest I didn't get past the universe only containing one particle :hiding:

Jim 

  • Like 1
Link to comment
Share on other sites

I was not quite clear on that one, one particle in a universe.

Does that mean two entities - one of the universe, and one particle, or are we talking about single entity - one "particle" (entity) and nothing else? Like no space (or space-time) just something we call particle?

  • Like 1
Link to comment
Share on other sites

Could not a single entity particle (a universe particle) still not spin on an axis without seeking permission or indeed need for the presence of another object; would this not remove the need for movement being relative to something else.

Indeed are we really saying that there can be no movement unless a second object is present in which to measure the "relative"  part.  How is this relative presence communicated to the first object so that it knows whether it is permitted to move or not?

Perhaps what we are saying is that the relative association is required only for the measurement of motion and not the existence of motion itself.

 

Remember , I'm an ideas man so go easy :) 

Jim  

Link to comment
Share on other sites

And here we go, down the philosophical rabbit hole ... :D

I think that prevailing view is that QM wavefunction is part of reality, regardless of the fact that we can't measure superposition of states. This means that something can be part of reality even if we can't measure it.

Which leads me to postulate correct answer for one particle universe (can it move, or can it spin):

One particle universe is in superposition of all imaginable states - all motion and spin vectors at the same time, and only once we measure it we will find it in particular state - moving or not, spinning or not ... :D

 

  • Like 1
Link to comment
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
 Share

×
×
  • Create New...

Important Information

We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue. By using this site, you agree to our Terms of Use.