Astronomy

[copernicus1234]

I was thinking and I came up with this odd vision. In this vision, it was stated, to me that the stars in the universe, including our sun, are stationary, based on experimental measurements. Example, a photograph of the celestial universe, in the last ten years, there have not been a measureable change in the positions of the stars. Probably in the last 100 years, since photograph, there hasn't been any changes of position, of the stars, and 1000 years there is no evidence (photography) and theres the time problem (no clocks). Isn't the assumed motion of the stars in the universe caused by the earth's daily and yearly rotational motions? Can someone explain to me how the distances of the stars, not including the sun, is measured. This in a very perplexing problem that has keep me awake, at night, since the stars are not in motion. Thank you.

Edited May 6, 2014 by copernicus1234

[pwagen]

Example, a photograph of the celestial universe, in the last ten years, there have not been a measureable change in the positions of the stars. Probably in the last 100 years, since photograph, there hasn't been any changes of position, of the stars, and 1000 years there is no evidence (photography) and theres the time problem (no clocks).

I thought this was pretty cool. It shows the stars close to the center of our galaxy, orbiting the black hole (visually enhanced, as you can probably tell).

Edited May 6, 2014 by pwagen

[Nicholas Kang]

You may think of stars are stationary, but in true they are not stationary, they just orbit around the galaxy center. Stars don`t move by its own, so do galaxy. The galaxy hardly move. It is just the space expansion that move them further apart.

[ajb]

You should look up the notion of proper motion.

[Nicholas Kang]

You are right in certain parts. But what about galactic movement across space? Aren`t they caused by space expansion? If not, this means my book is wrong.

[ajb]

You are right in certain parts. But what about galactic movement across space? Aren`t they caused by space expansion? If not, this means my book is wrong.

Well, the local expansion of the Universe is overcome by the local gravity of a given galaxy. Also the gravitational attraction of galaxies in a local cluster overcomes the expansion of the Universe. So, proper motion of stars within a galaxy is nothing to do with the expansion of the Universe. All the stars we see in the night sky are in our galaxy, though Hubble can resolve stars in Andromeda which is part of our local cluster.

 

We only really see the expansion of the Universe when dealing with clusters of galaxies.

[Nicholas Kang]

Are you sure that all the stars we see in the night sky are in our galaxy? The are billions of them, how would you prove then? Since stars are located in a galaxy, and galaxies are located in cluster, how can you sure that in such a vast expanding universe, the proper motion of stars really has nothing to do with the expansion of the universe even if the local expansion of the universe is said to be overcome by the local gravity. The gravity is shown in space-time, isn`t?

[ajb]

Are you sure that all the stars we see in the night sky are in our galaxy? The are billions of them, how would you prove then?

You can see that the stars are orbiting about the centre of the Milky Way. Well as far as I know, this has been properly done for star producing regions of the Milky Way. Also all the stars we see are relatively close.

 

Since stars are located in a galaxy, and galaxies are located in cluster, how can you sure that in such a vast expanding universe, the proper motion of stars really has nothing to do with the expansion of the universe even if the local expansion of the universe is said to be overcome by the local gravity.

Any contribution from the expansion of the Universe is tiny and just swamped by the local gravity.

 

 

The gravity is shown in space-time, isn`t?

Yes, according to general relativity gravity is seen as the local geometry of space-time.

[Nicholas Kang]

Ok, thanks. No objections, yet.

 

Regards,

 

Nicholas Kang

[ajb]

Ok, thanks. No objections, yet.

You mean questions!

 

I am not an expert in astronomy and I expect a quick google will give you more details.

[Nicholas Kang]

Keep it up

And thanks for reminding me It is Dr. Swansont.

[Dekan]

You can see that the stars are orbiting about the centre of the Milky Way. Well as far as I know, this has been properly done for star producing regions of the Milky Way. Also all the stars we see are relatively close.

 

 

Any contribution from the expansion of the Universe is tiny and just swamped by the local gravity.

 

 

 

Suppose it's the case that these days, local gravity can stop the expansion of space. As for example in galaxies such as our Milky Way or M31. These Galaxies are essentially tightly-packed clusters of stars.

And within them, the stars exert so much local gravitational pull on each other, that the cluster can't expand. So the the MY and M31 stay the same size.

 

OK, but what about the very early Universe. At that time, weren't all the stars tightly-packed into a single cluster. Which would resemble a kind of super-Milky Way, or super-M31.

Within such a Universal super-cluster, wouldn't the local gravitational pull between its constituent stars, be immensely strong. And so keep it the same size.

 

So how has the Universe managed to break out from gravity, and become an expanding Universe?

[ajb]

OK, but what about the very early Universe. At that time, weren't all the stars tightly-packed into a single cluster.

How early are you talking about? In the very very early universe there were no stars. We think stars first formes about 200 million years after the initial big bang.

 

Anyway, I don't think these early stars were packed into a single cluster.

 

So how has the Universe managed to break out from gravity, and become an expanding Universe?

There are differences in the density of material in the Universe and gravity iw weak on the large scale, there is a 1/r^2 law here.

[Mordred]

the early stars and galaxies wasn't packed tightly inflation had already occurred. Now as to why the universe expanded during the matter dominated universe, well the simple answer is that pressure is also involved. same with the radiation dominant era. The idea gas laws in cosmology has equations of state that relate the energy-density to pressure relations. This pressure relation acts in some ways as negative gravity in some textbooks (I personally don't like that way of explaining it)

 

anyways expansion is due to an energy-density to pressure relation. the equations of state is covered here

 

http://en.wikipedia.org/wiki/Equation_of_state_%28cosmology%29

 

here is a basic article in regards to universe geometry and how it affects distance measures

http://cosmology101.wikidot.com/universe-geometry page 2 is http://cosmology101.wikidot.com/geometry-flrw-metric/

 

-during the radiation dominant era radiation pressure dominated expansion

 

-during the matter dominant era matter slowed down the rate of expansion however didn't halt or cause a collapse. The negative pressure relations is still slightly positive as opposed to gravity as a positive pressure

 

now we are currently in the lambda [latex]\Lambda[/latex] dominant era (dark energy is one explanation for the cosmological constant lambda.

 

these articles will show the eras and there expansion relations

 

http://arxiv.org/pdf/hep-ph/0004188v1.pdf :"ASTROPHYSICS AND COSMOLOGY"- A compilation of cosmology by Juan Garcıa-Bellido
http://arxiv.org/abs/astro-ph/0409426 An overview of Cosmology Julien Lesgourgues
http://arxiv.org/pdf/hep-th/0503203.pdf "Particle Physics and Inflationary Cosmology" by Andrei Linde (full length textbook)

Edited June 8, 2014 by Mordred

[copernicus1234]

Did you know that the earth yearly motion is approximately Mach 60 that mean standing on the surface of the earth you are propagating 60 times faster then the fastest jet.

 

 

 

 

Einstein describes the effects of gravity using Newton's theory that is based on the earth-sun attraction but the attraction of earthly masses is not observed. Example, in an experiment, a small glass marble that is suspended from a string and separated (d = .0001mm), from a moveable 1000kg cubic block of solid gold. Marble is unaffected, by the gold block. The glass marble is placed a distance of .0001mm, from the surface of the gold block, and near the center of the outer surface of the gold block. As the gold block is slowly moved away from the suspended marble, the marble is unaffected by the gravitational force of the gold block. If masses attract, the marble's position would be affect by the change in position of the gold block's mass yet the gold block experiment produces a negative result. The graviational force theory orginates from Newton's observations of the earth's motion around the sun but Newton is ignoring the spinning of the earth, the internal effects of the earth's mantle, the enormous velocity of the earth's yearly motion (Mach 60) and the sun, that is emitting an enormous amount of energy. The gold block experiment, contradicts Newton law of gravity since the gold block and marble masses do not show the attraction of Newton's gravitational force. Newton theory is based on the sun-earth attraction but the sun-earth attraction is unrelated to masses attracting (marble-gold block) which prove Newton's gravitational theory is physically invalid.

 

Also, without Gottfried Leibniz's derivative (dx/dt) Newton would not have been able to form Newton's equations of mechanics or the integral. Newton would be absolutely nothing without Leibniz.

 

Edited July 24, 2014 by copernicus1234

[swansont]

 

Einstein describes the effects of gravity using Newton's theory that is based on the earth-sun attraction but the attraction of earthly masses is not observed. Example, in an experiment, a small glass marble that is suspended from a string and separated (d = .0001mm), from a moveable 1000kg cubic block of solid gold. Marble is unaffected, by the gold block. The glass marble is placed a distance of .0001mm, from the surface of the gold block, and near the center of the outer surface of the gold block. As the gold block is slowly moved away from the suspended marble, the marble is unaffected by the gravitational force of the gold block. If masses attract, the marble's position would be affect by the change in position of the gold block's mass yet the gold block experiment produces a negative result.

 

To what experiment are you referring, that used gold and marble? Cavendish was able to measure this, using lead.

 

http://en.wikipedia.org/wiki/Cavendish_experiment

[copernicus1234]

Then why cann't a marble rotate around a large solid gold sphere, in free space? Cavendish experiment is childish. In addition, why are we not attracked to a cliff, by a the force of gravity, when standing next to a cliff of enormous mass. Also, the motion of the celestial universe is caused by the earth's yearly motion, Mach 60!...........When the voyager 1 was traveling to Venus (hot), did anyone take any picture of the celestrial universe. Also those pretty picture of the galaxys with the pretty colors and gases are fake.

Edited July 28, 2014 by copernicus1234

[Janus]

Einstein describes the effects of gravity using Newton's theory that is based on the earth-sun attraction but the attraction of earthly masses is not observed. Example, in an experiment, a small glass marble that is suspended from a string and separated (d = .0001mm), from a moveable 1000kg cubic block of solid gold. Marble is unaffected, by the gold block. The glass marble is placed a distance of .0001mm, from the surface of the gold block, and near the center of the outer surface of the gold block. As the gold block is slowly moved away from the suspended marble, the marble is unaffected by the gravitational force of the gold block. If masses attract, the marble's position would be affect by the change in position of the gold block's mass yet the gold block experiment produces a negative result. The graviational force theory orginates from Newton's observations of the earth's motion around the sun but Newton is ignoring the spinning of the earth, the internal effects of the earth's mantle, the enormous velocity of the earth's yearly motion (Mach 60) and the sun, that is emitting an enormous amount of energy. The gold block experiment, contradicts Newton law of gravity since the gold block and marble masses do not show the attraction of Newton's gravitational force. Newton theory is based on the sun-earth attraction but the sun-earth attraction is unrelated to masses attracting (marble-gold block) which prove Newton's gravitational theory is physically invalid.

A 1000 kg cube of gold would be 2.68 meters to a side. To calculate the force on the marble using Newton's formula for gravitational force, d is the center to center distance between the masses, (marble and gold cube.) you haven't given a size for the marble, so I'll guesstimate it at a radius of 1/2 cm.

 

Thus, if the surface to surface distance between marble and cube is .0001 mm, then the center to center distance is 2.6805000001 meters.

 

The gravitational acceleration that the marble would have towards the cube would be 0.00000037 m/s^2 This will be counteracted by the force of gravity of the Earth pulling down on the marble. How much the marble would be expected to pull the string from vertical depends on the length of the string. (again something you neglected to mention). All in all, this would be result in a very very small deflection that you would have to measure.

 

In addition, the above calculation is actually on the high side, as it assumes that all of the gold brick's mass is contained within a 2.68 m radius sphere. Since it is not, (the corners stick out of such a sphere) the effective pull is weakened.

 

Also, when you say the experiment fails, you are implying that the experiment has actually been physically performed. That somebody actually got together 1000 kg of gold shaped into a brick, suspended a marble next to it and tried to measure the deflection of the marble. That, to me, seems highly improbable. For one thing, you wouldn't use a brick shape as you would be lessening the effect, and gold is pretty expensive to use for such an experiment. The way the experiment is set up it would take very accurate measurements to determine failure or success and there are much better ways of setting up the experiment to improve its accuracy.

 

 

Then why cann't a marble rotate around a large solid gold sphere, in free space?

It can, if removed far enough away from other gravity sources. But it is a very delicate situation. A 1000 kg sphere of Gold would have a radius of 2.02 meters. The escape velocity from the surface of the sphere would be 0.000257 m/s. Anything moving faster than that would fly away from the sphere. Orbital speed would be 0.00018 m/s and the orbital period would be 19.4 hrs. So an object just orbiting at the surface of the sphere would take over 3/4 of a day to complete its orbit. If we moved it out so that it was 1 meter away from the surface of the sphere, the orbital period would increase to 35.5 hrs or just a little under 1 1/2 days. If we keep increasing the distance, the orbital period keeps getting larger.

 

If there are any large gravity sources nearby, then there is a limit as to how far an object can be from the sphere and still maintain an orbit. For example, if we put our sphere in orbit around the Earth at the same distance as the Moon is, this limit is ~14.7 meters. Any further than this and Earth's gravity will disrupt the orbit.

Edited July 28, 2014 by Janus

[swansont]

Cavendish experiment is childish.

Very analytical. Just the kind of rigorous analysis that sways minds.

[Ophiolite]

Newton would be absolutely nothing without Leibniz.

Leibniz had big shoulders, then?

[copernicus1234]

The escape velocity from the surface of the sphere would be 0.000257 m/s. Anything moving faster than that would fly away from the sphere.

 

 

Nice analyse of the problem. This is the kind of analyse that I am looking for. You should become a moderator. This is a good example for people who want to answer my posts. These very short denial without an explaination is extremely boring. I read everything that you wrote. Great job.

Edited July 29, 2014 by copernicus1234

[swansont]

Nice analyse of the problem. This is the kind of analyse that I am looking for. You should become a moderator. This is a good example for people who want to answer my posts. These very short denial without an explaination is extremely boring. I read everything that you wrote. Great job.

This raises the question of why you didn't do this relatively simple analysis yourself. Unable or simply unwilling?

[copernicus1234]

 

The gravitational acceleration that the marble would have towards the cube would be 0.00000037 m/s^2 This will be counteracted by the force of gravity of the Earth pulling down on the marble.

 

 

This is patently incorrect.

Edited July 30, 2014 by copernicus1234

[Janus]

This is patently incorrect.

No it is not. The Earth's pull on the marble is straight down. The brick's pull is sideways. Thus the Earth's gravity tries to keep the string perfectly vertical, while the Brick's gravity tries pull the string from the vertical. Without the Earth's gravity, the marble would be free to pull the marble all the way to the brick. Instead, we have two forces acting against each other.

 

Put another way, the marble is on the end of a pendulum, in order for it to get closer to the brick, the pendulum must swing in that direction, But doing so causes the marble to rise against gravity ( the marble is at its lowest point when it is hanging straight down). The Earth's gravity opposes this. The forces will balance out when with the string at something less than vertical. How much of a sideways motion this results in depends on the length of the pendulum. The longer the string, the more sideways swing you can get at equilibrium.

[copernicus1234]

The forces will balance out when with the string at something less than vertical. How much of a sideways motion this results in depends on the length of the pendulum. The longer the string, the more sideways swing you can get at equilibrium.

 

 

Experimentally, there is no sideways motion, of the marble, formed by the gold block.