The Secrets of the Universe
What is the Speed of the Earth?
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Courtesy NASA Click for Larger Image
This page deals with the actual speed of the Earth moving through space. There are many directions of travel and various speeds that have to be taken into consideration. We will divide this into categories and will provide two explanations. One in lay terms so the average person may easily understand the complex movements our planet and the other in scentific details. 

Why is this of importance?

Why is this of importance? For any discussion on the posibility or the probabiliy of space flight dealing with interstellar flight, it is necessary to have this data. 

Imagine for a moment that you have a faster than light or warp capable star ship...

Considering the speed at which the Earth moves, even a short mission away from Earth would result in the planet being millions of miles away from the point of origin at the time you left. Nasa calculations to reach a simple point like the Moon require enormous calculations and pin point accuracy. Any small error left uncompensated would result in Astronauts missing the Earth on return.

Motion, Speed and Direction of Travel of Earth Through Space

Or

"How the Hell Do I Calculate the Way Home"
A study by R. Schmidt July 21, 2006

Disclaimer:The following figures are approximate values for demonstartion only! Please DO NOT use them to calculate actual flight paths. We are not responsible for people getting "Lost in Space".

Consider yourself sitting at your computer on a chair...How fast are you moving?

1. The Earth "wobbles" on its polar axis.  This motion is not relevant (IMO) to the calculations needed to return to earth from interstellar space as it is an "in situ" motion, but it exists.

2. The Earth revolves {spins} on its axis. For these calculations we will use the equator with a circumference of approx. 25,000 miles. One rotation of Earth is approx. 24 hours. Again this is "in situ" motion so not relevant to space travel, but adds to our "stationary chair" model
25000/24 =1041.7 MPH

3. The Earth is orbiting the Sun once a year. The circumference of the Earth's orbit is approx.  607.6  million miles {or 940 million kilometers}. One year is approx. 365 days
365 days X 24 = 8760 hours
607,600,000/8760 = 69,360.73 MPH

So far we have basically 3 Directions of Motion {Wobble, Spin and Orbit} and a combined speed of 1041.70 + 69,360.73 = 70,402.43 MPH for a person sitting in a chair at the Equator. 
{Note: We will do the actual vector calculations at the end}

The following source gives more detail and a more precise calculation based on your latitude and more exact figures. Anyone dizzy yet? A little motion sickness perhaps?

NASA - What is the speed of the Earth?

When you take into account the three-dimensional picture of the Sun's movement through our Milky Way Galaxy, things get very complicated.

4. The sun {and hence the solar system} is moving towards the constellation Hercules, namely to the star Lambda Herculis at 12 miles per second {or 20 kilometers per second} which is 43,200 MPH

5. The Solar system is also moving upwards, at 90 degrees to the plane of the Milky Way, at 4.34 miles per second or 15,624 MPH. But we are actually leaving the Galaxy, out about 50 light years now and will be moving out to 250 light years before it reverses. Details of the mechanics of this are explained in the link below. We also crossed the Galactic plane 2 million years ago.

6. The Solar system is orbiting around the Galaxy at an "estimated" speed of 124 miles per second {or 200 kilometers per second} which is 446,400 MPH. The way that figure has been calculated can be found at the link below. 

Stanford University - What is the speed of the Solar System?
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Image NASA/ GSFC.

This is where finding our way home becomes difficult, as we do NOT have an actual true figure for this calculation. The further out we go, taking into account the various motions and speed, the more difficult it becomes to get precise calculations ergo the more room for error. Until we can actually go and measure the distances, a "best guess" is all we have. Over the past few decades these values have been revised several times, and are constantly being added to today.

From an Astronomer's point of view  this is not a problem, as they are merely observing from Earth and can fix their calculations when they get new data… no harm done… just reprint the maps.

BUT from a spaceship pilot point of view…touring just within our own galaxy… the problems are enormous. 

From a navigator's point of view, we can leave out the "wobble" and the Earth's rotation as those movements are "in place". For later calculations we could also leave out the Earth orbiting the Sun, because if we can make it back to the Sun, I am sure we can locate Earth.

So our "armchair Astronaut" is now moving through 6 different directions and a combined speed of approximately 574,585 MPH 

  69,361 MPH Spin and Orbit
  43,200 MPH Towards Lambda Herculis
  15,624 MPH Perpendicular to Galactic Plane
446,400 MPH Orbiting the Galactic Center {or Galactic Spin Rate}
-------------------
574,585 MPH Speed of Earth within Our Galaxy

So for every hour you are away from the solar system, your planet is moving half a million miles, and in several directions…

Now if you want to leave the galaxy add another 1,339,200 MPH to the calculations. This is the speed the galaxy is moving through the universe. But THEN you really get into difficulties pin pointing you reference point. Details can be found here…

So you see… the propulsion unit is the least of your worries…. 
You better have a REALLY GOOD NAVIGATOR.

NASA - What is the Speed of our Galaxy?
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Credit: NASA/JPL-Caltech/R. Hurt (SSC)

Oh and about that vector calculation thing? … 
--------------Forget it I have a headache! … 
----------------------------Go ask a rocket scientist! ...

WANTED: ROCKET SCIENTIST...
JOB: Provide Accurate measurements and vector details for the Scientific Explanation
PAY: The Satisfaction that comes from sharing your knowledge.
 

What is the speed of the Solar System?

(by Amara Graps)

Or, how fast is the Sun (Solar System) hurling towards the constellation Hercules?
 

From the book: _Guide to the Galaxy_, 1994; Henbest and Couper; Cambridge University Press.

The Sun is moving towards Lambda Herculis at 20 kilometers per second or 12 miles per second. Or in units "per hour": 72,000 kilometers per hour or 45,000 miles per hour. This speed is in a frame of rest if the other stars were all standing still.

The three-dimensional picture of the Sun's movement through the Galaxy is a little more complicated.

The Sun is moving upwards, out of the plane of the Milky Way, at a speed of 7 kilometers per second. Currently the Sun lies 50 light-years above the mid-plane of the galaxy, and its motion is steadily carrying it further away.

But the gravitational pull of the stars in the Galactic (Milky Way) plane is slowing down the Sun's escape. The astronomer Frank Bash estimates that in 14 million years the sun will reach its maximum height above the Galactic disk. From that 250 light-year position, it will be pulled back towards the plane of the Galaxy. Passing through, it will travel to a point 250 light-years below the disk, then oscillate upwards again to reach its present position 66 million years from now. We crossed the plane 2 million years ago. We are currently in the thick of the galactic disk and our view of distant regions is largely blocked by dust but 10-20 million years from now, our motion will allow a full view of our starry galaxy.

The Sun-Galactic center distance is 25,000 light-years -- plus or minus 2,000 light-years. The galaxy is thought to be 100,000 light-years in diameter and we are thought to be about halfway out from the center (used to be thought that we were two-thirds out).

If you have a good idea of the Sun's distance from the Galactic center, then the solar system's speed can be approximated. Using speed measurements of the gas at different distances from the Galactic center, the Sun appears to be cruising along at 200 kilometers per second and it takes 240 million years to complete the grand circuit around the Galaxy. This speed is an absolute speed.

Stanford University - What is the speed of the Solar System?
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What is the Speed of Light

The speed of light in a vacuum is an important physical constant denoted by the letter c for constant or the Latin word celeritas meaning "swiftness"

In metric units, c is exactly 299,792,458 metres per second (or 1,079,252,848.8 km/h). Note that this speed is a definition, not a measurement, since the fundamental SI unit of length, the metre, has been defined since October 21, 1983 in terms of the speed of light: one metre is the distance light travels in a vacuum in 1/299,792,458 of a second. Converted to imperial units, the speed of light is approximately 186,282.397 miles per second, or 670,616,629.384 miles per hour.

Source Wikipedia

What is a Light Year

A light-year is approximately equal to

    * 9,460,528,404,879 km (about 9.461 Pm)
    * 5,878,482,164,161 statute miles[1]
    * 63,239.7263 AU (about 63,240 AU)
    * 0.306601394 pc

The actual, exact length of the light-year depends on the length of the reference year used in the calculation, and there is no wide consensus on the reference to be used. The figures above are based on a reference year of 31,556,925.9747 seconds, but other reference years are often used, such that the light-year is not an appropriate unit to use when extremely high precision is required.

However, the IAU style guide recommends the use of calendar years, specifically Julian (and not Gregorian) calendar years of 365.25 days or exactly 31,557,600 seconds. This gives the light-year an exact value of 9,460,730,472,580,800 meters, again about 9.461 Pm).

The light-year is often used to measure distances to stars. In astronomy, the preferred unit of measurement for such distances is the parsec, which is defined as the distance at which an object will generate one arcsecond of parallax when the observing object moved one astronomical unit perpendicular to the line of sight to the observer. This is equal to approximately 3.26 light years. The parsec is preferred because it can be more easily derived from, and compared with, observational data. However, outside scientific circles, the term light-year is more widely used.

1 light-year = 9.46*10^{15} meters
1 parsec = 3.08*10^{16} meters 

Source Wikipedia

See Also the Cosmic Yin Yang
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