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yogiwp
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Just curious, what is the speed of an object standing still on earth? (taking into account Earth's rotation and revolution, the rotation of our galaxy, the fact that we are part of an expanding universe, etc.)
arildno said:Fast in respect to what?
As Tom McCurdy implied, your question is meaningless without specifying a reference frame.
If you're asking "what is the velocity of an object at rest relative to the Earth within the C.M. reference frame of the universe?", you have a somewhat better posed question.
Let's say from the frame of reference of an absolute stationary point in the universe. (Does such point exist? The center of the universe maybe?)Tom McCurdy said:It all depends on your frame of reference, it you negelt any accelerations just say we are standing still and everyone is moving around us.
Cool!Garth said:The discovery of the Cosmic Microwave Background (CMB) has indeed made the latter posed question a sensible one.
When the Earth's velocity around the Sun has been taken into account the Solar System is traveling at 390 +- 60 km/sec relative to the surface of last emission of the CMB. However when the Sun's motion around the Galaxy is also taken into account this translates into the fact that the Galaxy is traveling relative to the surface of last emission of the CMB, which probably defines the C.M. reference frame of the universe, at 603 km/sec or about 0.2%c! (Nature, Vol 270, 3 Nov 1977, pg 9)
arildno said:Cool!
I thought the question at present was unanswerable..
Garth said:However when the Sun's motion around the Galaxy is also taken into account this translates into the fact that the Galaxy is traveling relative to the surface of last emission of the CMB, which probably defines the C.M. reference frame of the universe, at 603 km/sec or about 0.2%c! (Nature, Vol 270, 3 Nov 1977, pg 9)
yogiwp said:Garth: thanks, that's exactly the answer I was looking.
So, according to SR, our Earth time is somewhat slower than time at "some absolute stationary point in the universe" (say, CMB or something else). Is this correct?
yogiwp said:So, according to SR, our Earth time is somewhat slower than time at "some absolute stationary point in the universe" (say, CMB or something else). Is this correct?
Gonzolo said:If one believes CMB can define a reference frame, then the answer is yes. Personally though, I am not entirely convinced of this, although it sounds nice at first.
jcsd said:The CMB can define a refernce frame pretty much, due to the extermely homogenous nature of the universe when it was emitted, but it's just one refrence frame among an infinite number of reference frames.
The key pont is that the laws of physics do not prefer any refrence frame; if stated corrcetly they are the same in all frames and not dependt on one particular frame. Howvere this doesn't stop nature from conspiring to create a refernce frame that is very convient, especially from the point of view of doing calculations in cosmology (i.e. the one defined by the CMBR).
Because we are moving relative to it?Gonzolo said:How is the CMB reference frame different than the one defined by placing ourselves (or our galaxy) at (0,0,0) of a spherical coordinate system?
The CMB could possibly be in the same reference frame throughout the universe.Gonzolo said:How is the CMB reference frame different than the one defined by placing ourselves (or our galaxy) at (0,0,0) of a spherical coordinate system?
Gonzolo said:How is the CMB reference frame different than the one defined by placing ourselves (or our galaxy) at (0,0,0) of a spherical coordinate system?
Standing still does not have a speed in the traditional sense. Speed is defined as the rate at which an object moves in a particular direction. Since standing still means not moving at all, it does not have a speed.
Standing still can be described using the concept of velocity, which is the speed of an object in a specific direction. Since standing still means having a velocity of zero, it can also be described as having zero velocity.
Technically, standing still is not considered motion since there is no change in position. Motion is defined as the movement of an object from one position to another. However, standing still can be considered a relative motion, as the person or object may be moving in relation to something else, such as the Earth's rotation.
No, an object cannot be standing still and moving at the same time. Standing still means not moving at all, while moving means changing position. These are two contradictory states and cannot occur simultaneously.
As previously mentioned, standing still does not have a speed. Therefore, it cannot be measured using traditional methods such as a speedometer. However, the velocity of standing still can be measured by calculating the displacement of the object over a period of time, which would result in a velocity of zero.