I am curious how fast the earth is moving, I am not asking about its rotation around the sun or the rotation on the earth's axis. I am curious if you were to observe the solar system in space at a single point and not affected by gravity or any force and you were to watch the solar system pass on by.
How fast is the earth moving.
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JoeTheJuggler
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I think the OP is asking how fast the Milky Way is rotation (relative, for instance, to a point in another galaxy). Is that right? Or are you asking about our solar system's motion independent of the galaxy's rotation? (I imagine there is some other motion, but I'm not sure.)
The problem here is that there is no fixed reference frame of "space". Your observer can only determine how fast the Earth is moving relative to himself. It doesn't matter if this observer is somehow immune to the effect of all forces.
roger
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Your question still makes no sense. Imagine an observer in an empty part of space, hurtling towards the earth at 200 kps. He would measure the speed at nearly 200 kps. Another observer in the same part of space, going 100kps away from the earth, will measure it at -100kps. Neither observer is feeling any force.
scratchy
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I can see only one meassure that has some meaning: how long it takes for the earth to make a full circle around the sun. If that makes it 220 km/s its less than 0,1 % the speed of light, almost 300 000 km/s.
Yes. How fast is it basically expanding outward from the center of the universe.
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There is no center of the universe. Everything is moving away from everything else (in general, anyway), so there's no single location you can point to and say "that's it."
You can choose a sensible reference frame (i.e. how fast the earth is moving relative to the sun, or relative to the center of our galaxy, or anything else you like), but there's no such thing as "floating motionless in space." You're always going to have to pick something to be motionless relative to.
You can choose a sensible reference frame (i.e. how fast the earth is moving relative to the sun, or relative to the center of our galaxy, or anything else you like), but there's no such thing as "floating motionless in space." You're always going to have to pick something to be motionless relative to.
Oualawouzou
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I am a little puzzled by this.
It is my layman's understanding that the Universe started a given "point" out of which it is (still) expanding. The analogy of a balloon being inflated is often used, but even this balloon as a center: why doesn't the Universe? If we were to turn around the galaxies and get them to go opposite their current directions, wouldn't they converge towards the actual "center of the Universe"?
roger
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There is no center to the universe.
Summary: so far as we can tell, there is no center; space itself is expanding, and uniformly in all directions.
Now, if it turns out the universe is uniform, we could mathematically compute a center, but a) we don't know if it is uniform, and b) we don't know the extent of the universe.
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So, even if there is a center, we don't know where it is. Thus, there is no way to specify the earth's speed in relation to it. Even if we could, it's entirely arbitrary. That point will move as the universe expands, and there is no special relevance to the center of the universe. I believe Ceritus doesn't understand relative motion, not that s/he is trying to get the measure of the earth compared to a specific point which was poorly articulated.
Summary: so far as we can tell, there is no center; space itself is expanding, and uniformly in all directions.
Now, if it turns out the universe is uniform, we could mathematically compute a center, but a) we don't know if it is uniform, and b) we don't know the extent of the universe.
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So, even if there is a center, we don't know where it is. Thus, there is no way to specify the earth's speed in relation to it. Even if we could, it's entirely arbitrary. That point will move as the universe expands, and there is no special relevance to the center of the universe. I believe Ceritus doesn't understand relative motion, not that s/he is trying to get the measure of the earth compared to a specific point which was poorly articulated.
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In the analogy of the expanding balloon, the universe would be the surface of the balloon, not the volume. The balloon itself may have a center, but the two-dimensional surface does not. Yet all points on the surface move away from each other as the balloon expands.
Effectively, you can think of our universe as the three-dimensional surface of a four-dimensional balloon. I don't think that's literally true, but it's the analogy for understanding how the whole universe expands with all objects moving away from each other, yet there is no center point or stationary reference frame the expansion is relative to.
I less than three logic
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You're thinking of the wrong dimension of the balloon in the analogy. In the balloon analogy, the entire universe in all dimensions is represented by just the outside of the balloon. Just the surface, nothing else, not the space or air inside of the balloon. Where is the center of the surface area of a balloon when it is expanding?
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Claim: The Earth doesn't move; obviously, everything else does!
Evidence: From my stationary point of reference, the Earth is not moving towards me, away from me, or tangentially to me. Since there is no relative motion between the Earth and me, the Earth must not be not moving!
Right?
Wrong.
You must specify a point of reference, and pose the question as "What is the velocity of the Earth relative to a point in space that is located at X, Y, and Z?"
Your original question is too vague, and is open to too many assumptions.
Evidence: From my stationary point of reference, the Earth is not moving towards me, away from me, or tangentially to me. Since there is no relative motion between the Earth and me, the Earth must not be not moving!
Right?
Wrong.
You must specify a point of reference, and pose the question as "What is the velocity of the Earth relative to a point in space that is located at X, Y, and Z?"
Your original question is too vague, and is open to too many assumptions.
You can use the cosmic microwave background. The Cosmic Rest Frame is defined as that in which the CMB is isotropic.
I agree it's difficult to visualize sometimes. Yes, in the Big Bang the universe did, in a sense, explode outward from a point. But the problem is, we were at that point. So was the next galaxy over, and that quasar 10 billion light years away. You can't point to any particular location and say it was at the center, because every point in the universe has just as much claim to being the "center" as any other.
If we turned all the galaxies around and they started contracting, they would indeed collapse back to a single point, but you'd still run into the same problem: that single point would contain everything, with no one location having any particular claim to fame.
roger
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The speed that the galaxy is rotating has nothing to do with the center of the universe, which doesn't exist anyway. Hence, your "yes" is puzzling.
Oualawouzou
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Fascinating, I've been aware of the balloon analogy for years yet never picked up only the surface of it is relevant to the demonstration. Thanks! 