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Author Topic: Are galaxies such as the Milky Way expanding?  (Read 2584 times)

Offline CliffordK

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Are galaxies such as the Milky Way expanding?
« on: 18/12/2012 08:43:18 »
Ok,

The Milky Way will occasionally capture and incorporate other small galaxies. 

However, what about the existing stars in the Galaxy?

I always thought of gravity as a contracting force...  making things slowly spiral together.  But...  is it also an expansion force?

Thinking of the Earth and the Moon.  The Moon causes tides on the Earth, and drag slowing down the rotation of the Earth, and corresponding adding energy to the moon's orbit, and it is slowly receding from the Earth. 

Likewise, I presume the Earth's gravity interacts with the sun, and slowly increases the Earth's distance from the sun.

In fact, any object beyond the geosynchronous, or equivalent orbit should gain energy from the body it is orbiting, while the body looses energy.

Are the same tidal forces in effect with galaxies.

In particular, Spiral Galaxies like the Milky Way seem to force the spirals to rotate too fast.  Shouldn't this add energy to the stars in the spiral, and cause the spiral portion of the galaxy to slowly expand.

At the same time, some of the stars in the central bulge should loose energy, and thus the central bulge would should slowly contract, at least in the middle part of the bulge, while the stars in the outer part of the bulge may eventually join the spirals.


 

Offline Ethos_

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Re: Are galaxies such as the Milky Way expanding?
« Reply #1 on: 21/12/2012 18:25:20 »


I always thought of gravity as a contracting force...  making things slowly spiral together.  But...  is it also an expansion force?

There is a balancing act going on here my friend. The force of gravity competing with the orbital momentum of the planetary bodies. In reality, the planets orbiting the sun are falling toward the sun due to the combined gravity of both bodies. However, because the velocity of their orbits produces enough centrifugal force to balance the fall, they continue in orbit. The reason the planets continue to recede outward from earlier positions is the result of the energy which is scrubbed off during this competition. It's not because gravity is somehow working against its self.
« Last Edit: 21/12/2012 22:52:40 by Ethos_ »
 

Offline UltimateTheory

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Re: Are galaxies such as the Milky Way expanding?
« Reply #2 on: 22/12/2012 22:31:04 »
Likewise, I presume the Earth's gravity interacts with the sun, and slowly increases the Earth's distance from the sun.

There is also one another aspect:
Sun is making lighter with time- it's emitting photons, neutrinos, and other particles in the space in eruptions.
Earth, Moon and Sun also are getting heavier by matter that is attracted by them.
Even if meteorite is burning in the atmosphere, its particles is making Earth heavier.

Quote
In particular, Spiral Galaxies like the Milky Way seem to force the spirals to rotate too fast.  Shouldn't this add energy to the stars in the spiral, and cause the spiral portion of the galaxy to slowly expand.

At the same time, some of the stars in the central bulge should loose energy, and thus the central bulge would should slowly contract, at least in the middle part of the bulge, while the stars in the outer part of the bulge may eventually join the spirals.

That's why scientists introduced Dark Matter and Dark Energy.. They couldn't explain what they see using currently known formulas.
 

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Re: Are galaxies such as the Milky Way expanding?
« Reply #2 on: 22/12/2012 22:31:04 »

 

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