[Political Junkie Too]

The problem with light being massless is the lensing effect.

If light is massless, then why does it bend around galaxies? Why are scientists saying that the gravitational effect of galaxies bends the light of objects behind it?

If a galaxy can bend light, then why can't the entire mass of the universe bend light, too?

"Most Exquisitely Aligned" Gravitational Lens Is A One-In-A-Billion Find...The object is record-breaking and it has implications well beyond its beauty.

Oldest Ever Star Clusters From When Universe Was 460 Million Years Old Discovered....This kind of object made the universe transparent in the first billion years.

And from just a few weeks ago...

Overlooked for 140 years: Perfect Einstein ring discovered by accident

-PJ

[Lazamataz]

The problem with light being massless is the lensing effect. If light is massless, then why does it bend around galaxies?

Well, that one is easier to explain. Spacetime itself is warped by gravity. The light, still massless, is changed in direction by that warping.