A question

[marymouse]

I was taught in grammar school that the sun rises in the east and sets in the west. No one ever said anything about the moon, except it had 4 quarters. Lately, I started to wonder. I am sure all you smart people know this. Can you clue me in? Thank you.

(I have time to think about this because I am afraid to use theVM because those java script errors might mess things up.)

[sb126k]

What's your question exactly? I couldn't get one from your post.

[Howie]

The moon goes thru a cycle every month!!!

You see a 1/4 lit up moon then a half lit up moon, then a 3/4 lit up moon and finally, you see a full lit up moon!!!

The java Problem will not hurt your computer,,,just will slow you down and be a pain in the butt!!!

Howie

[fjgiie]

Hi marymouse,

Just from observation you have seen the full moon also rise in the east just like the sun.
Here is a wikipedia link for the phases the moon goes through. At new moon, when you can just see
a thin crescent, it goes down right behind the sun. Each day the moon goes down later and later behind
the sun, until full moon when it is approximately 12 hours behind. The full moon rises in the east as we have
sunset in the west.
http://en.wikipedia.org/wiki/Moon_cycle

[bmendez]

I was taught in grammar school that the sun rises in the east and sets in the west. No one ever said anything about the moon, except it had 4 quarters. Lately, I started to wonder. I am sure all you smart people know this. Can you clue me in? Thank you.

(I have time to think about this because I am afraid to use theVM because those java script errors might mess things up.)

Hi Mary,

The Moon also appears to rise in the East and set in the West. So do all the stars and planets. This is because of the rotation of Earth. The Sun and Moon do not actually move from East to West, but rather Earth spins from West to East, and that makes everything in the sky appear to move from East to West on a daily basis.

The Moon itself goes around Earth (causing its phases - we see different parts of it lit up as it moves around us) and that motion is actually from West to East. But that motion takes a month to complete. Since it is much slower than the rate that Earth spins we don't see the Moon moving from West to East during the course of one day.

Hope that helps,
Bryan

[marymouse]

Thank you very much.

[startrak]

I know, there are no stupid questions but here goes. Do space dust particles all travel in the same direction or are they bouncing off one another? If bouncing off one another anything to do with dark energy/matter?

[fjgiie]

There may not be any silly questions especially here on this forum, just some "difficult" ones to answer sometimes. The interstellar dust that we are looking for comes from the general direction of the constellation Ophiuchus and the dust particles are all traveling in the same direction in a stream.

Dark energy has more to do with the the rate of expansion of the universe. Dark matter must be what you are referring to. Does interstellar dust interact with this dark matter? If the two things are real and would come together then I guess that would be interacting.

My own thoughts are that dark energy is the wrong term and that the cause of the increase in the rate of expantion of the universe lies outside of the universe and not within it. "I did not want to be in this play anyhow." Only silly Answers.

[Nikita]

Space dust...well, I would guess it depends on what is going on out there. Let me take a chance at explaining what I have learned, I'm sure a pro will come in and put me in my place though.

We know that objects will move in the direction pushed. If I throw a ball, it will go the direction I sent in (not always the way I meant for it to go!) Now on Earth, there are other forces that will slow it down very quickly, a big one being gravity. In space, the force is weaker out in deep space and stronger closer to objects. Therefore, objects will go the direction sent until pulled upon by something else. Just within our solar system we have solar wind pushing stuff away but the force of the sun and planets pulling things in. A comet is pulled towards and circles the sun by gravity, but the dust and water it sheds always moves away from the sun because of the solar wind. So here we have two objects moving in two directions. The dust is being pushed by the solar wind outward and should continue outward until it is pulled into something by gravity.
Going on a larger scare, dust from a supernova, where a sun explodes it's outer shell, can go in any direction and can travel a long, long way. Two supernovas can create dust that travels in two different directions. Those dust particles can be aligned toward the same direction if they are pulled the same way by a larger object or they can cross paths if there is no other force and they are just too small to affect eah other.
So to try and sum it up, dust can be moving in any direction and may change directions multiple times before finally getting sucked in by something. What we did was go and collect some of that dust that we knew about. The stuff we have we knew the basic direction it was moving which allowed us to set the collector to try and get them head on. But we do have some shallow suspects because they were in the neighborhood, but going in another direction when they ran into the collector.
Dark Matter, Dark Enegry, well, I don't know how much they would affect the dust. I think I answered at a basic level. I don't think I could get into the other factors within the constrains of the forum. Besides, I think my head would explode at some point too! I don't know if the top dogs even know the answers to some of those.
I hope I not only made sense but answered fairly accurately. There are so many variables to be able to give a simple answer and I could see a whole semester in college spent on just answering this question and all the formulas. The final would be to determine how a dust particle of a specific size would move at a given location in space, at what speed, where it would be going and the last known direction it came from, what were the last known forces to affect it. And why.

[startrak]

Thanks so much for your very informative answers that I think I understand. So glad I only think of questions -- not answers -- or my head would definitely explode.

[jsmaje]

I just wish they could rename that CMB feature dubbed by someone with little sensitivity the 'axis of evil'.
How about the 'axis of interest' or whatever?

[bmendez]

Nikita's and fjgiie's answers were good.

I'll just add to them a bit...

Dust particles in the Galaxy generally move in all manner of directions, depending on the forces that are acting on them. That we see the ones collected by Stardust coming from the constellation Ophiuchus is a combined effect of our Solar System's motion in the Galaxy (toward the constellation Hercules) and the motion of a local cloud of dust and gas moving away from the center of the Galaxy (in the constellation Sagittarius).

The density of the dust particles is very low and they themselves are very small, so collisions between them are exceedingly rare.

We don't know what dark energy and dark matter are (hence their mysterious names), but we do know what they are not, and we do know what effects they have on large scales in the Universe. Dark matter is repsonsible for the structure of galaxies and clusters of galaxies and the large scale structure in the Universe. Dark energy is responsible for the acceleration of the expansion of the Universe.

Dark matter is so-called because it does not interact well with photons and hence does not produce light that we can detect. It therefore is not the usual kind of matter that you and I are made of, which is the same stuff that interstellar dust particles are made of. So dark matter is not likely to have any interactions with interstellar dust, just as it does not have any interaction with you and I.

-Bryan

[Nikita]

There goes my head!
See, leave it to the experts!

[Nikita]

Startrak,

I saw this and I thought of this thread. Talk about mind blowing! Enjoy!

[fjgiie]

Dark Energy and Dark Matter Links (A whole lot about what?)

http://antwrp.gsfc.nasa.gov/apod/ap071021.html Big Rip (from Nikita above)

http://supernova.lbl.gov/~evlinder/sci.html (read first)

http://www.lbl.gov/Science-Articles/Arc ... nergy.html Dark Energy

http://chandra.harvard.edu/xray_astro/dark_matter.html Dark Matter Mystery - four pages


http://chandra.harvard.edu/chronicle/04 ... index.html Dark Side
http://chandra.harvard.edu/chronicle/index.html

http://imagine.gsfc.nasa.gov/docs/scien ... nergy.html Dark Energy
http://arxiv.org/abs/astro-ph/0202256v1 Abstract


We consider the fate of the observable universe in the light of the discovery of a dark energy component to the cosmic energy budget. We extend results for a cosmological constant to a general dark energy component and examine the constraints on phenomena that may prevent the eternal acceleration of our patch of the universe. We find that the period of accelerated cosmic expansion has not lasted long enough for observations to confirm that we are undergoing inflation; such an observation will be possible when the dark energy density has risen to between 90% and 95% of the critical. The best we can do is make cosmological observations in order to verify the continued presence of dark energy to some high redshift. Having done that, the only possibility that could spoil the conclusion that we are inflating would be the existence of a disturbance (the surface of a true vacuum bubble, for example) that is moving toward us with sufficiently high velocity, but is too far away to be currently observable. Such a disturbance would have to move toward us with speed greater than about 0.8c in order to spoil the late-time inflation of our patch of the universe and yet avoid being detectable.
Dragan Huterer, Glenn D. Starkman, Mark Trodden
(Submitted on 13 Feb 2002)
http://arxiv.org/pdf/astro-ph/0202256 PDF arXiv:astro-ph/0202256v1

Phantom Energy and Cosmic Doomsday
Cosmologists have long wondered whether the Universe will eventually re-collapse and end with a Big Crunch, or expand forever, becoming increasingly cold and empty. Recent evidence for a flat Universe, possibly with a cosmological constant or some other sort of negative-pressure dark energy, has suggested that our fate is the latter. However, the data may actually be pointing toward an astonishingly different cosmic end game. Here, we explore the consequences that follow if the dark energy is phantom energy, in which the sum of the pressure and energy density is negative. The positive phantom-energy density becomes infinite in finite time, overcoming all other forms of matter, such that the gravitational repulsion rapidly brings our brief epoch of cosmic structure to a close. The phantom energy rips apart the Milky Way, solar system, Earth, and ultimately the molecules, atoms, nuclei, and nucleons of which we are composed, before the death of the Universe in a ``Big Rip''.
Robert R. Caldwell, Marc Kamionkowski, Nevin N. Weinberg
(Submitted on 25 Feb 2003)
http://arxiv.org/pdf/astro-ph/0302506 Phantom Energy

Findings Pin Down Age of Universe, Birth of First Stars
http://www.space.com/scienceastronomy/m ... 30211.html
WMAP Wilkinson Microwave Anisotropy Probe

Now, I need to read some of this

_______fjgiie