Calculating Earth's Speed Around Milky Way

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In summary, the Earth orbits the sun at a speed of 18.5 miles/sec and the sun orbits the galactic center at a speed of 137 miles/sec.
  • #1
pLatOscLoSET
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I know that the Earth orbits the sun at roughly 18.5 miles/sec and the sun orbits the milky way at around 137 miles/sec. How do I calculate Earth's speed as it coils around the milky way?
 
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  • #2
You take the distance of the sun from the centre of the milky way (about 30,000 lyr) and the time it takes to go around, 1 galactic year = 250million years.
 
  • #3
? The progress the Earth makes around the milky way IS the sun's speed. The Earth is orbiting the sun so it spends just as much time heading away from the directon of rotation as towards relative to the sun so the net velocity of the Earth around the milky way is the velocity of the sun around the milky way.
 
  • #4
maverick_starstrider said:
it spends just as much time heading away from the directon of rotation as towards relative to the sun


How do we know that?
 
  • #5
...because the Earth orbits the sun in an elliptical orbit...
 
  • #6
maverick_starstrider said:
The Earth is orbiting the sun so it spends just as much time heading away from the directon of rotation as towards relative to the sun so the net velocity of the Earth around the milky way is the velocity of the sun around the milky way.

I thought the the world line of the Earth is helical in spacetime... if that is so then wouldn't that contradict the statement quoted above?
 
  • #7
I think what you're getting at is motion represented by an epicycle, the same as in this picture:
http://phyun5.ucr.edu/~wudka/Physics7/Notes_www/img127.gif
(Replace the Earth with Galactic Center, and Mars with Earth, and imagine the Sun is at the center of the epicycle)

What others are saying is the radius and period of the Earth's orbit are so small compared to the galactic orbit, that for all intents and purposes, the Earth's motion (with respect to the sun) can be ignored.
 
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  • #8
yes but the velocity of the Earth through its epicyclic path is NOT its velocity AROUND the milky way. For the velocity around the milky way we don't include the components of the velocity that aren't tangentional to the elliptical orbit. So the net velocity of the Earth AROUND the milky way is what you'd get if you projected that funky orbit onto the elliptical orbit and it would fluctuate but its net value would be that of the suns rotation around the galaxy.
 
  • #9
I attached an image... I guess it is not a big deal in the grand scheme of things but the Earth definitely appears to me to travel a greater distance in an equal amount of time.
 

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  • #10
Yeah, you're right - the Earth's orbit is closer to perpendicular than parallel to the galactic plane. You can draw a right triangle with those two speeds on the legs and calculate the hypotenuse...
 

FAQ: Calculating Earth's Speed Around Milky Way

How do scientists determine Earth's speed around the Milky Way?

Scientists use a combination of astronomical observations and mathematical calculations to determine Earth's speed around the Milky Way. They track the movement of stars and other celestial objects and use the laws of motion and gravity to calculate the speed and trajectory of Earth's orbit.

What is Earth's average speed around the Milky Way?

Earth's average speed around the Milky Way is approximately 828,000 kilometers per hour. This means that Earth travels around the Milky Way at a distance of approximately 100,000 light-years in about 225-250 million years.

How does Earth's speed around the Milky Way affect our perception of time?

Earth's speed around the Milky Way does not have a significant impact on our perception of time. However, it does contribute to the gradual shifting of the night sky, known as the precession of the equinoxes. This phenomenon occurs over a period of approximately 26,000 years.

How does Earth's speed around the Milky Way compare to other galaxies?

Earth's speed around the Milky Way is relatively slow compared to other galaxies. For example, the Milky Way's neighbor, the Andromeda galaxy, is estimated to have a speed of about 2.2 million kilometers per hour.

Can Earth's speed around the Milky Way change over time?

Yes, Earth's speed around the Milky Way can change over time due to various factors such as gravitational interactions with other celestial bodies. However, these changes are relatively small and do not significantly affect Earth's orbit or speed around the Milky Way in the short term.

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