Inking a comic about the glorious variety that is life. Published weekly from Aotearoa 🇳🇿 New Zealand

Mighty din

In the primordial plasma soup: photons wielding swords are shown nearing gravitons wielding clubs. Both are represented as spherical entities. Photons are radiating, while gravitons are massive. Photons battled gravity making a mighty din: in the foreground a photon crosses his sword with graviton's club, making a sound "klang!". Sound waves radiate from the weapons. In the background, more photons and gravitons fight - one photon skewers a graviton, and one graviton smashes photon's head. This noise froze when the universe cooled: noise waves are depicted as dark arcs, next to them there is two open freezers, and one photon and one graviton lay on the ground, icicles hanging from them and their weapons. The frozen waves creating a cosmic ruler: a measuring tape is shown placed against the frozen waves, measuring 1, 2, 3. There is some galaxies depicted between the waves, and the distance between them is marked as 490 million light-years. Triangle-person is shown looking at a computer screen. It displays "Astronomy Today", depicting the frozen waves below, with subtitle: "And that's one way to measure the universe! On the final image, the Triangle-person looks at the reader and says: "I swear they make this shit up!"

In the primordial plasma soup: photons wielding swords are shown nearing gravitons wielding clubs. Both are represented as spherical entities. Photons are radiating, while gravitons are massive.

Photons battled gravity making a mighty din: in the foreground a photon crosses his sword with graviton’s club, making a sound “klang!”. Sound waves radiate from the weapons. In the background, more photons and gravitons fight - one photon skewers a graviton, and one graviton smashes photon’s head.

This noise froze when the universe cooled: noise waves are depicted as dark arcs, next to them there is two open freezers, and one photon and one graviton lay on the ground, icicles hanging from them and their weapons.

The frozen waves creating a cosmic ruler: a measuring tape is shown placed against the frozen waves, measuring 1, 2, 3. There is some galaxies depicted between the waves, and the distance between them is marked as 490 million light-years.

Triangle-person is shown looking at a computer screen. It displays “Astronomy Today”, depicting the frozen waves below, with subtitle: “And that’s one way to measure the universe!

On the final image, the Triangle-person looks at the reader and says: “I swear they make this shit up!”

This is called Baryon acoustic oscillations. Early universe varied in density, and the denser regions had radiation pressure (photons) fighting with gravity. This created a ripple effect as if a stone was thrown into a pond.

These waves traveled outward from each of the dense regions for 450 million light-years until the universe cooled down enough for them to freeze in place.

Since there were many dense regions (so, many stones thrown into the pond) the circular ripples kept colliding creating a randomly interfering pattern. The effect is like waves in the middle of the ocean - many randomly distributed peaks and troughs, forming a pattern.

This can now be inspected - if you measure 490-500 million light-years away from any galaxy, you are statistically more likely to find another galaxy there, as opposed to looking closer or further away. The effect is very subtle - but real.

Why 490-500 million light-years? The universe has expanded! BAO is one of the ways we can measure this expansion.

#science