How is it that spiral galaxies don't spiral?

Hans Blaster said:

It does not travel on a spiral path.

Click to expand...

Shemjaza said:

Spiral shape, not spiral motion.

Click to expand...

Hans Blaster said:

No, in accordance with the laws of physics. The "spiral arms" are just places of higher density, and in particular higher star formation. The stars that light up the spiral arms are massive and young (far less than a billion years old).

Click to expand...

But then there would be lanes (like a target shape) rather than spirals.

You've go to stop whiffing the glue of atheism and consider the facts about creation and the OBVIOUS signs of a young universe (like spiral galaxies).

Shemjaza said:

Why would gravity only work laterally into rings?

Also the laws of physics are a completely separate issue to atheism... for goodness, sake, the original theory of the Big Bang came from a priest.

(The Big Bang was often put forward as a justification for creation and theism, because it demonstrates some kind of beginning, rather then an eternal steady state).

Click to expand...

Ophiolite said:

Point 1: Intuition as to the physics of the problem does not trump careful collection of detailed data and meticulous analysis by trained experts. You are mistaken.

Point 2: Your intuition on the point is weak by any standards. You are mistaken.

Point 3: Spiral arms are regions of higher density in a galaxy’s disk, not fixed collections of stars. Because galactic disks rotate differentially (inner parts orbit faster than outer parts), material arms would quickly wind up and disappear. Their persistence shows that spiral arms are patterns, not permanent structures.

The leading explanation is density wave theory. Spiral arms are long-lived gravitational density waves that rotate through the disk at a different speed from the stars and gas. As gas passes through an arm it is compressed, triggering star formation. Bright, short-lived blue stars highlight the arms, while older stars drift away.

The spiral shape arises naturally from gravity acting in a rotating, shearing disk, which favours trailing spirals. Bars and galaxy interactions can strengthen or trigger these patterns, but the arms themselves are sustained density waves rather than material features.

The writing in my previous explanation was sloppy. I had AI tidy it. Nevertheless, the key take away is - you are mistaken.

And, as @Shemjaza notes, atheism and basic physics are separate issues.

Click to expand...

Tinker Grey said:

I tell ya what. Here's an experiment. Draw a black spiral on a piece of paper. Put a red dot on one of the outer arms. Poke a hole in the middle of the spiral and poke a pencil through that hole. Now spin it.

Once you understand why that red dot doesn't move toward the center you might begin to understand why our solar system doesn't move toward the center.

Just cuz something looks like a spiral doesn't mean its bits are going down a drain.

If the above doesn't work for you, starch a string in a spiral shape; stick a pin in it; spin it; note that the pin isn't moving toward the center.

Click to expand...