38 replies to this topic

[ninjadude]

the L, on 27 August 2011 - 08:14 PM, said:

Okay so In past, it was very close to earth and we didnt see Sun at all.

It was closer to the earth in the far past. So the solar eclipses would not have looked like they do today. In the far future, the moon will be still further away. So far future earthlings will see more sun during a solar eclipse.

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Also I wonder, in what period Solar and Moon eclipse happens? How many times in a year? In decades?

For an eclipse to occur, the Moon must be near the intersection of the two orbital planes. The number of eclipses per year varies and appears in many places around the world.

Edited by ninjadude, 28 August 2011 - 07:46 PM.

[ninjadude]

the L, on 27 August 2011 - 07:57 PM, said:

I wonder too what would our solar system look like if Jupiter was Sun?

there would be a large star and a smaller star. The movie '2010' had some nice speculation about how the sky would look at the end of the movie. Also how increasing mass in Jupiter could cause ignition.

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Also If sun is nuclear reactor that use hydrogen why shouldnt we head in that direction. Science look for all types of energy sources instead to copy nature?

Using nuclear fusion and hydrogen is one of the hottest things going in alternative energy. The problem is at least twofold. You have to create tremendous sustained heat. And you have to contain the reaction in a magnetic field. Currently we can do both of these things but for only short times.

Edited by ninjadude, 28 August 2011 - 07:52 PM.

[Chrlzs]

What they said...

Just to add, the Moon isn't exactly the right size to cover the Sun..  And even if it was, eclipses would still vary due to the non-circular orbits involved.  And as pointed out above, the Moon's distance from us is varying over the millenia so the 'coincidence' is really about you and I happening to be alive and discussing it at this time.

Given all the bazillions of facts that are out there, there's gotta be some interesting coincidences...

[the L]

Thanks guys. You are very informative.
More questions. I read little about arch-astronomy and I found some note where it said about ages. Age of Virgo, Age of Aquarious and similar.
Anyway cycles of ages for all signs are long, so cycle started 26000 bc and end 300 bc, or I get it wrong. Can someone explain that please.

[ShadowSot]

the L, on 31 August 2011 - 07:32 PM, said:

Thanks guys. You are very informative.
More questions. I read little about arch-astronomy and I found some note where it said about ages. Age of Virgo, Age of Aquarious and similar.
Anyway cycles of ages for all signs are long, so cycle started 26000 bc and end 300 bc, or I get it wrong. Can someone explain that please.

Well... one reason you might get confused is because it's not to do with astronomy, but astrology.
Astrology... had a brief flinge with science back in the Ptolemaic age of Egypt and has studiously avoided it ever since. It's based off of the precession of the equinoxes, where the wobble of the Earth's movements causes the sun to move through the 12 classical Greek constellations. (Ignoring the forgotten 13th one.)

People try to link it to archaeology by supposedly dating sites based off of their alignment to the heavens. Problem is, these dates don't often match any other dating method used and their proof is "it looks like it aligned" some time ago.

[MID]

the L, on 28 August 2011 - 11:30 AM, said:

Thanks MID.

Can you answer on post 11.

Don't think I was ignoring you, L.
I got cut off in the middle of posting on Saturday evening by a Hurricane that decided to intrude upon my space.  I'm just back as of yesterday, able to post!

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Okay so In past, during solar eclipse, moon didnt cover the sun? Or it was very close to earth and we didnt see Sun at all.

Although there is an observed increasing of the distance between the Earth and the Moon, it's so small a value as to be something that no one living on this planet will ever notice, or probably has noticed, for all the duration of man's presence here.  I don't think the Moon's distance from earth was ever significantly closer so as to be angularly larger than we see it in any naked-eye perceptual sense.

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Also I wonder, in what period Solar and Moon eclipse happens? How many times in a year? In decades?

It varies alot L.

Solar eclipses occur 2 or 3 times a year, sometimes more than that, but's it's rare to see 4 or 5 solar eclipses in a year.
Lunar eclipses happen also happen just about every year, one or two of them, sometimes three. And sometimes, there are none in a particular year.  We expect to average 2+ per year for this century according to the folks who calculate these things, and we'll see lunar eclipses; 2 this year, 2 in 2012, and 3 in 2013.

Frequency seems to be about the same for both types of eclipse.

[psyche101]

ninjadude, on 27 August 2011 - 01:20 AM, said:

An easier answer than those given so far. The moon fits exactly because we have incredible dumb luck. In the far distant past, it did not, it in the far distant future. it will not. The moon's distance from the earth is not constant.

The answers to the other stuff is right on.

I was always amazed by that too. What incredible luck hey! I cannot remember, the window is still open for another couple million years or so?

Top thread L.

Edited by psyche101, 01 September 2011 - 08:24 AM.

[the L]

Thanks on your answers.

I got some new questions.

Whats distance from our solar system and center of our galaxy?
Whats spiral arm and how long periodic movement of that arm lasts? (whatever it was)
Is gravity itself proof of another dimension? It effect on things trough matter and on very big distance.

[the L]

ShadowSot, on 31 August 2011 - 08:13 PM, said:

Well... one reason you might get confused is because it's not to do with astronomy, but astrology.
Astrology... had a brief flinge with science back in the Ptolemaic age of Egypt and has studiously avoided it ever since. It's based off of the precession of the equinoxes, where the wobble of the Earth's movements causes the sun to move through the 12 classical Greek constellations. (Ignoring the forgotten 13th one.)

People try to link it to archaeology by supposedly dating sites based off of their alignment to the heavens. Problem is, these dates don't often match any other dating method used and their proof is "it looks like it aligned" some time ago.

Can you remind me about 13 sign? My memory is fading mate.
I read that age of one sign last for 2150 years. How do we get that number?

[ShadowSot]

the L, on 02 September 2011 - 07:40 PM, said:

Can you remind me about 13 sign? My memory is fading mate.
I read that age of one sign last for 2150 years. How do we get that number?

The thirteenth is Ophiuchus, no worries on memory, this past week has had me stumbling over myself more often than a room ful of clumsy clones.

As for the age of the sign, is it 2150 or 2160?
It takes about 2160 years for the precession of Earth to move through each constellation along the elliptic.

[Mentalcase]

Sun's distance to the milky way's galactic center (supermassive blackhole) is roughly 25,000 light years. The milkyway is aproximately 100,000 LY in diameter.


I forget how long it takes a spiral arm to make a complete rotation. Depending on reference the milky way rotates at about 600 km per second. One facinating aspect of a spiral is the speed at which stars rotate. In our solar system, the closer you are to the sun, the faster you move (i.e. Mercury verses pluto). However, with a spiral galaxy this isn't the case. Some stars on the outer spiral arms rotate faster around the glactic center then stars much closer. This is presented evidence for the existense of dark matter.


Demensions are a completely different subject (and very speculative and near impossible to ever detect, if possible at all).. As we know of only 3 spacial demnsions and time as the fourth, there are another ten or so theorized demensions. A subect that is really, extremely hard to comprehend. I think L, you would appreciate a course in theoretical physics.

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TimeA temporal dimension is a dimension of time. Time is often referred to as the "fourth dimension" for this reason, but that is not to imply that it is a spatial dimension. A temporal dimension is one way to measure physical change. It is perceived differently from the three spatial dimensions in that there is only one of it, and that we cannot move freely in time but subjectively move in one direction.

The equations used in physics to model reality do not treat time in the same way that humans commonly perceive it. The equations of classical mechanics are symmetric with respect to time, and equations of quantum mechanics are typically symmetric if both time and other quantities (such as charge and parity) are reversed. In these models, the perception of time flowing in one direction is an artifact of the laws of thermodynamics (we perceive time as flowing in the direction of increasing entropy).

The best-known treatment of time as a dimension is Poincaré and Einstein's special relativity (and extended to general relativity), which treats perceived space and time as components of a four-dimensional manifold, known as spacetime, and in the special, flat case as Minkowski space.

Additional dimensions Theories such as string theory and M-theory predict that physical space in general has in fact 10 and 11 dimensions, respectively. The extra dimensions are spatial. We perceive only three spatial dimensions, and no physical experiments have confirmed the reality of additional dimensions. A possible explanation that has been suggested is that space acts as if it were "curled up" in the extra dimensions on a subatomic scale, possibly at the quark/string level of scale or below.

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

Edited by Mentalcase, 03 September 2011 - 07:31 PM.

[MID]

the L, on 02 September 2011 - 07:19 PM, said:

Thanks on your answers.

I got some new questions.

Whats distance from our solar system and center of our galaxy?
Whats spiral arm and how long periodic movement of that arm lasts? (whatever it was)

L,

The distace from here to the galactic center is, as has likely already been said, around 27,000 light years.
That's roughly 160,000,000,000,000,000 miles away, or around a billion and a half times the distance between us and the Sun!

Kind of a big place, eh?

I think you're asking about the period for the galaxy to rotate once?
There are several estimates, but the average value of those is around 240,000,000 years (let's say around 3 million human lifetimes).  It takes a while.

Edited by MID, 05 September 2011 - 08:42 PM.

[the L]

And why I cant see our Milky way galaxy? I seen numerous pictures but never in live.
http://www.wired.com...es 2))&pid=2102

Edited by the L, 15 September 2011 - 06:11 AM.

[Chrlzs]

the L, on 15 September 2011 - 06:09 AM, said:

And why I cant see our Milky way galaxy? I seen numerous pictures but never in live.
http://www.wired.com...es 2))&pid=2102

You need to get out more...  What I mean is, find a dark location, away from city and town lights, on a clear night (being in a desert area and/or at a higher altitude helps..).  Then spend twenty minutes in absolute darkness to let your eyes fully dark adapt, and then finally.. look up.  Well, actually, for northern hemisphere viewers at the moment (September) before midnight, you'll need to look a bit West of South for the thickest part of the Milky Way.  Trouble is, the Moon is around at the moment - it washes out the sky, so maybe leave it for a week or two..

Sadly for you northerners, you don't get a very good view of the 'centre' of the Milky Way, which is near Sagittarius.  Sagittarius is probably at its highest around July (?) I think.

For us Southerners (eg Australia), it's almost directly overhead at this time of year.  So our desert night skies are simply beautiful, as the 'Backbone of the Night' stretches out overhead...  OK, that image is cheating, as it's a composite of many selected time exposures, but for a fully dark adapted eye and from a clear desert sky, it can almost look that good..!

It's one of the reasons why I love camping in the middle of nowhere...

Edited by Chrlzs, 15 September 2011 - 12:54 PM.

[MID]

the L, on 15 September 2011 - 06:09 AM, said:

And why I cant see our Milky way galaxy? I seen numerous pictures but never in live.
http://www.wired.com...es 2))&pid=2102

Ah but you can, L!

Read very carefully what Chrlzs told you about seeing the "Milky Way"
It's visible.
It does depend on where you are and when you're there.
However, alot of people have a tough time seeing it, when I've pointed it out to them, plain as day, on a dark night here in the mid-Atlantic U.S. Sometimes, the glow of it is massive to me, and yet, I have to teach people how to look without staring (averting the eyes, relaxing them...off center of the object of your desire...an astronomer's technique!).

Maybe it's a little hazy and they're not picking it up...I'll give them a fine binocular and have them look into it.  The stars they see in thefield suddenly are amazing!

I suggest consulting star charts for your particular location.  They will paint the Milky Way on the chart for you, so you'll know where to look.

Where Chrlzs is now should be pretty good viewing  (I think it's coming up on Spring in Australia??).  I don't know where you are, so it may not be so
good right now....but generally, everyone has the opportunity to see an arm of our glaxy, if they know where to look!


And if you know what you're looking at...it's a pretty stunning thing!


Might I suggest that you go to www.astronomy.com.   Maybe subscribe to that journal (It's great).  Look, you're far too interested in this stuff not to check out your sources, and in my opinion, for what it's worth, Astronomy is the best one you can get!