Andromeda Definition and 66 Threads

I'm fulfilling my life-long dream of learning relativity theory by working through Taylor and Wheeler's Spacetime Physics. I've successfully made it through the first three chapters except for one problem, 1-10 on p. 23: Samantha is beamed from Earth via a transporter to the planet...

The https://www.physicsforums.com/archive/index.php/t-240147.html" occurred to me several years ago when I was still chasing relativity by the tail. I didn't learn that Rietdijk, Putnam, and Penrose had advanced this argument till yesterday. Weird. Anyway there are direct testable consequences...

Why is the closing velocity of Andromeda and our galaxy so high? 100-140 kms^-1 http://en.wikipedia.org/wiki/Andromeda_(astronomy)"

Wikipedia: http://en.wikipedia.org/wiki/Rietdijk-Putnam_Argument Quote: "Two people pass each other on the street; and according to one of the two people, an Andromedean space fleet has already set off on its journey, while to the other, the decision as to whether or not the journey will...

http://en.wikipedia.org/wiki/Rietdijk-Putnam_Argument"

The orbits of the Magellanic Clouds about the Milky Way Galaxy have apparently been determined, and the two dwarf irregular galaxies are now about as close as they will get to the MW in their 2.2 billion year orbit. See p. 42 of "Our Growing, Breathing Galaxy" by Wakker and Richter, Scientific...

Homework Statement An astronaut wishes to visit the Andromeda galaxy 2 million light years from Earth. He wishes the one way trip to take him 30 years (ie in the frame of reference of the spaceship). Assuming that his speed is constant, how fast must he travel? Homework Equations...

Does Andromeda contain dark matter? Is the newly discovered halo able to account for the rotation of the galaxy?

The article from space.com: http://www.space.com/scienceastronomy/070107_andromeda_halo.html I have a question about the article. What do current galaxy formation theories say about why the cores of galaxies like Andromeda have more metal-rich stars than their halos do? I am guessing...

Since our galaxy and the andromeda galaxy are drifting towards each other. How long will it take to look as big as the moon today in the night sky?

The Andromeda glaxaxy is two million light-years from earth, measured in the common rest frame of the Earth and Andromeda. Suppose you took a fast spaceship to Andromeda, so it got you there in 50 years measured on the ship. If you sent a radio message home as soon as you reached Andromeda, how...

New pics. These are a month old, but I forgot to upload them. They are from Sept 29. That was the first night it got really cold and I drove to the Poconos to set up shop, so while the sky was very clear and very dark, it was also very windy. First is another shot at the Andromeda Galaxy...

http://www.space.com/scienceastronomy/050920_andromeda_stars.html

Very quiet around the board today. And yesterday. Where is everybody? I spent a night in the deep woods, lying on my back on the ground, looking at the stars. There was very little silence in the woods. The peepers have been joined by chorus frogs and tree frogs, and they are raving in...

Is the Andromeda Galaxy going to collide with the Milky Way? I've heard that the Andromeda Galaxy is going to collide with the Milky Way someday. I understand how its radial velocity relative with respect to the Milky Way is determined through its blueshift, but how do we know its tangental...

Why is it easier to measure overall structure of Andromeda Galaxy than to measure Milky Way Galaxy?