How close to the Universal "equator" is the earth? or How close is the earth to the Galactic "equator"?

Question

How close to the Universal "equator" is the earth? or How close is the earth to the Galactic "equator"?

Answer 1

I am not sure we have any idea as far as the "universal equator" where we are at.  In the Milky Way, we are actually towards the outside of it.

http://www.msnbc.msn.com/id/10385928

Answer 2

There is nothing like universal equator, Centre of the universe and such like terms. The concept of Universe, endless precludes all that.

Coming to our own galaxy, 'Milkyway':

The Galactic plane (as seen from Earth, that implies the whole Solar system) is well defined. It is a great circle that makes an angle of 62d 56' degrees with our reference Great circle, Celestial Equator, at a point whose Right Ascension is 18hrs 49min (It is obvious that the declination is '0' degrees being on Equator). It is perceived to be the Galactic Equator.

But since the Galactic Center is situated at RA=17h 42' 37",

Decl= -28d 57' that is not on the galactic plane (galactic equator). It can be guessed that Solar system (that is speck in galactic dimensions) is displaced from the galactic equator slightly. Solar syatem is 26,000 light years from galactic center (an object called 'Sagittarius A').

Answer 3

The Milky Way divides the sky into two roughly equal hemispheres.  That would suggest that we're even with the center of the galactic plane up and down.  Since crossing the center is also historically when the Earth has extinction events, it's time to watch out. But where the Milky Way is 100,000 light years across, it's only 1,000 light years thick.  If you glue 5 CDs together, you get something like the proportions.  Don't use your kid sister's favorites - she'll get mad at you, and will get even.  She's so much smarter than you are, so it's gonna hurt. You're better off using your own.  Or you could just not glue them - hold them together to get the idea, then put them back into their jewel boxes. Anyway, we're about 26,000 light years from the center.  Remember that the radius is about 50,000 light years.  So we're a little over half way to the outside.

The Universe is not known to have any angular momentum of it's own.  It's simply not spinning.  All the evidence suggests that the Universe is not flattened, but extends in all directions in a uniform way.  Now, we don't see the whole Universe.  We only see the visible part.  The rest of it is invisible, due to the expansion.  The farther two points are apart, the faster they seem to be moving away from each other.  At the edge of the visible Universe, things are moving away from us at the speed of light.  That's the Cosmic Microwave Background Radiation (CMBR) - a leftover from when the Universe was about 370,000 years old.  Since we can't ever see anything past this stuff, the real shape of the full Universe could be anything.  We are moving with respect to the CMBR.  It shows up in a Doppler shift dipole.  So, perhaps, there is a preferred rest frame of reference.  At least locally.

Answer 4

The Galactic equator as plane of the galactic disk: Sun is 65 LY above it currently. In galactic coordinates, the Sun is only a few million km above it - the solar system is the reference for it.

There is no universal equator. The universe has no references to use for such coordinates.

Answer 5

The celestial equator, the Galactic equator, the ecliptic... are all great circles projected on the celestial sphere for the purposes of calculations.

The celestial sphere is always described as having a radius such that the distance between the observer and the centre of the planet is negligible.

Any great circle has "poles", points that are located at exactly 90 degrees from the great circle.

The celestial equator's poles are the celestial poles, which are the projection of Earth's axis of rotation on the celestial sphere.

Using the same approach, there are Galactic poles.  If you want to see them as the projection of the Galaxy's axis of rotation, then you have to imagine a radius such that the distance between the observer (that's us) and the Galactic centre is negligible.

That negligible distance is 25,000 light-years, so that the "distance" to the Galactic equator would be measured in millions of light-years (if the equator were to be a real object -- it's not, it is a mathematical concept).

The universe has no real equator.  However, using the Doppler shift observations, we can identify two special points on the Cosmological Microwave Background radiation:  the one towards which we approach and its opposite, the point we appear to be moving away from.

SInce these points are easily identifiable and are 180 degrees apart, then it is possible to draw a great circle that is everywhere at 90 degrees from these points.  That could be a universal equator.  If so (and given that it is a projection on the CMB radiation), then it is 13.7 billion light-years away.

As for angular separation (as in "When will we cross the Galactic equator"), the answer is never.  These points of reference are measured from Earth.  They are centred on the observer and move with the observer.

It is as if you carried a very large circle around you and the circle moves with you, marking a permanent radius around you.  You walk forward, the circle moves forward at the same rate.

When will you cross the circumference?  never.  You are always at the centre.

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On a sphere, if you have two distinct great circles, then they must cross exactly twice (and the two intersections are 180 apart).

The ecliptic (which shows the apparent path of the sun over the year) and the celestial equator are two great circles on the celestial sphere.  They cross twice:  the two intersections are called "equinoces" (singular = equinox).  When the Sun is at one intersection, it is said to be the "day of the equinox" (Spring or Autumn).

The Galactic equator is also a great circle.  Therefore, the ecliptic also crosses it twice.  Which means that the Sun crosses the Galactic equator twice per year.

If you look at the reference system as centred on the Sun, then it is the Earth that follows the ecliptic and crosses the Galactic equator twice every year.

If there were such a thing as a universal equator, it would also be a great circle.  Therefore, the Sun (or Earth, depending on the point of view you use) would cross it twice a year.