Those of you who are astronomy buffs (or Colbert Report fans) may have heard the news this past January that the Milky Way is just as massive as Andromeda. Colbert even did a special on his show about “America’s Galaxy.”
Just by watching the tides on Earth, we can figure out what the gravitational tidal forces on our planet are from everything around us, including from the Earth itself. The Earth dominates everything, and that’s why the oceans stay bound to our planet. But then we can look at what the external effects are, and where they come from. The Moon turns out to be the strongest, the Sun’s effect is about 1/3 of the Moon’s, and everything else is negligible.
Well, by looking at the outskirts of the Milky Way galaxy, we can determine what the tidal effects of both the Milky Way and Andromeda are, and figure out what their mass ratios are.
Know what his results are?
Andromeda is not only more massive than the Milky Way, it is (most likely) two or three times the mass of our galaxy. So no, we are not the same size as Andromeda, and one possible (and very interesting) explanation could be that Andromeda simply has more dark matter than we do! I am sure there will be more to learn about our own local group coming soon…