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Question for astronomers
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Author | Message |
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Bob DeWoody Send message Joined: 9 May 10 Posts: 3387 Credit: 4,182,900 RAC: 10 |
Do stars that are relatively nearby, say less than 10 LY, display any motion against the background of stars that are much farther away? Or is our time frame just too short to catch such motion? Bob DeWoody My motto: Never do today what you can put off until tomorrow as it may not be required. This no longer applies in light of current events. |
Mr. Kevvy Send message Joined: 15 May 99 Posts: 3776 Credit: 1,114,826,392 RAC: 3,319 |
"Yes", if by "display any motion" you mean that photographs over time within the range of a human lifetime will show that they moved. "No" if you meant you'll see them move by looking at them, unless you can look at them without averting your eyes or sleeping for a year or so. :^) The fastest, Barnard's Star, has this note: "The 10.3 seconds of arc it travels annually amounts to a quarter of a degree in a human lifetime, roughly half the angular diameter of the full Moon." Caveat: I am not astronomer, nor do I play one on TV. |
Bob DeWoody Send message Joined: 9 May 10 Posts: 3387 Credit: 4,182,900 RAC: 10 |
Well I was figuring a period that would cover an astronomer's career. So that begs another question. Are all nearby stars watched on a regular basis to determine their projected path over the years and are any of them projected for a path through the oort cloud in the next few thousand years? Bob DeWoody My motto: Never do today what you can put off until tomorrow as it may not be required. This no longer applies in light of current events. |
betreger Send message Joined: 29 Jun 99 Posts: 11361 Credit: 29,581,041 RAC: 66 |
Well I was figuring a period that would cover an astronomer's career. So that begs another question. Are all nearby stars watched on a regular basis to determine their projected path over the years and are any of them projected for a path through the oort cloud in the next few thousand years? IMO it is very unlikely any stars will go through the oort cloud in that short of time frame. |
Gary Charpentier Send message Joined: 25 Dec 00 Posts: 30676 Credit: 53,134,872 RAC: 32 |
Millions are watched and cataloged. For a good introduction http://en.wikipedia.org/wiki/Proper_motion |
Julie Send message Joined: 28 Oct 09 Posts: 34053 Credit: 18,883,157 RAC: 18 |
Do stars that are relatively nearby, say less than 10 LY, display any motion against the background of stars that are much farther away? Or is our time frame just too short to catch such motion? Might have something to do with gravitational lensing. Bending of space and therefore also time as the Universe consists of spacetime, also know as the aether. http://en.wikipedia.org/wiki/Gravitational_lens [edit]Otoh, after reading the whole thread, the above has nothing to do with the opening post... :)) Spacetime and gravity do have an influence on any moving object in the Universe is what I think. rOZZ Music Pictures |
betreger Send message Joined: 29 Jun 99 Posts: 11361 Credit: 29,581,041 RAC: 66 |
When will you guys stop all this silly curvature of spacetime nonsense It is not nonsense, gravity lensing is used in astronomy. |
Es99 Send message Joined: 23 Aug 05 Posts: 10874 Credit: 350,402 RAC: 0 |
When will you guys stop all this silly curvature of spacetime nonsense Considering he just claimed that gravity is caused by the rotation of the Earth's core I think we can ignore Chris' scientific 'advice' Reality Internet Personality |
OzzFan Send message Joined: 9 Apr 02 Posts: 15691 Credit: 84,761,841 RAC: 28 |
If the Earth stopped rotating we wouldn't all fly off into space! but we would weigh less than we do now. But there would be no alternating days and nights, and the tides would be affected. [off topic] http://image.gsfc.nasa.gov/poetry/ask/q1168.html If the Earth stopped spinning suddenly, the atmosphere would still be in motion with the Earth's original 1100 mile per hour rotation speed at the equator. All of the land masses would be scoured clean of anything not attached to bedrock. This means rocks, topsoil, trees, buildings, your pet dog, and so on, would be swept away into the atmosphere. Whether the Earth were to stop spinning suddenly, or slowed to a stop, it would not be good for its inhabitants. |
Es99 Send message Joined: 23 Aug 05 Posts: 10874 Credit: 350,402 RAC: 0 |
If the Earth stopped rotating we wouldn't all fly off into space! but we would weigh less than we do now. But there would be no alternating days and nights, and the tides would be affected. Exactly, gravity is nothing to do with the Earth's rotation. We would only fly off because of Newton's 1st law. Gravity is an attractive force related to the separation of two masses according to Newton's law of Gravitation. F= GMm/r^2 in the case of the Earth, the two masses would be the mass of the Earth and whatever object we are talking about, e.g. a person. Your weight is the value of the force, F. r is the distance between your centre of mass and the Earth's centre of mass and G is the universal gravitational constant. (6.67 x 10^-11 N m^2/kg^2.). Your weight (the size of gravitational attraction between you and the Earth) has nothing to do with the spinning of the Earth's core. Einstein uses the curvature of space-time to model this attractive force quite successfully. The CERN people have been trying to figure out what gives things mass. Light does bend around gravitational objects and this has been shown via Eddington's famous experiment of 1919. The bending of light because of the curvature of Space-time is a different effect that the everyday bending of light we see due to refraction. Reality Internet Personality |
Es99 Send message Joined: 23 Aug 05 Posts: 10874 Credit: 350,402 RAC: 0 |
... Artificial gravity is not the same force as gravity. It just creates an acceleration the same as the one that produced by the gravitational force. Much like a spinning round about. You feel the acceleration because the wheel is spinning, you don't fly off as long as you are holding tight. In the case of the space station you will be stopped from flying off because of the walls of the spaceship. This will feel like gravity. It has nothing to do with gravity and more to do with inertia. Reality Internet Personality |
Mr. Kevvy Send message Joined: 15 May 99 Posts: 3776 Credit: 1,114,826,392 RAC: 3,319 |
Artificial gravity is not the same force as gravity. Actually in G.R. the Equivalence principle shows the two as the same, with the caveat that it holds true for point-sized samples. (You can tell if your local "gravity" is due to "upwards" acceleration through space or acceleration due to gravity by whether it has tidal falloff by the square of the distance from the hypothesized other mass.) This equivalence is strong enough that it was used by Einstein to deduce the bending of light rays by gravitational fields. The equivalency is that a beam of light traveling across a room accelerating "upwards" will curve "downwards", so the exact same curve should appear under acceleration due to gravity. That it did was yet another confirmation of G.R. |
Es99 Send message Joined: 23 Aug 05 Posts: 10874 Credit: 350,402 RAC: 0 |
Artificial gravity is not the same force as gravity. The equivalence principle says that the acceleration is the same. That is not the same as saying the force is the same. Reality Internet Personality |
JaundicedEye Send message Joined: 14 Mar 12 Posts: 5375 Credit: 30,870,693 RAC: 1 |
And what's the effect of the Dark Matter Lattice on gravity, mass and all tangible matter? Why don't the stars at the edge of a galaxy revolve around the center mass at the correct rate (slower than they actually do)? "There are more things in Heaven and Earth, Horatio........." :D...g "Sour Grapes make a bitter Whine." <(0)> |
Odysseus Send message Joined: 26 Jul 99 Posts: 1808 Credit: 6,701,347 RAC: 6 |
A gyroscope’s angular momentum resists tipping (rotation about a different axis), so that it can remain stable at an impossible-seeming angle. But it has no additional resistance to falling: it still has to be supported. Put a gyroscope on a scale, and no matter how far it leans over its weight will read the same. No matter how fast or slow the Earth spins, its gravity remains constant. It used to rotate faster, when the Moon was closer, and given enough time would eventually become tidally locked, making only a few rotations per year—but the dying red-giant Sun will probably vaporize both bodies before that happens. |
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