Others have talked about keeping up with the news to get in on their conversations, but I want to expand on that, explaining how and why.
The Link Between Politics and News
Political discussions are (often) about empirical facts and what's practically possible and current events. (Sometimes the discussions are about political philosophy and how the world should be, and even following current events will help with that in the long run, since opinion pages often discuss current events in light of underlying political philosophy. Peufeu's list of books addresses the political philosophy side, although you might want to see if you can find an undergrad textbook on political philosophy before reading the primary source material, so you can see how different ideas are in conversation with each other.)
I'd suggest asking people in the group where they like to get their news.
Then, in addition to their favorites, I'd suggest skimming a few well-accepted news sources. The following list is based on being an English speaker in the U.S., but:
- The Week Magazine (nice summaries of important news--often samples from the sources below)
- New York Times
- Washington Post
- Wall Street Journal
- The Economist
- BBC News
- The Guardian
- Al Jazeera News
Since you're a scientist, maybe add in something like Gizmodo or Wired or Ars Technica.
(You could set these sources as preferences on a newsfeed app, and you'll get a mix of articles. Don't start out by expecting to thoroughly read through even one of these every week.)
And/or try to watch Stephen Colbert, John Oliver, Trevor Noah, Samantha Bee, et al. as they talk about politics on their TV shows.
Perhaps at first, try to focus on one or two current political topics. In America, a current one might be: What are tariffs and economic sanctions, and what happens when they are used? Another: What is "gun control" and what values and legal arguments are invoked by each side?
After a while, you'll see that many news stories keep repeating similar background (though maybe the slant and substance of that background is different across various news sources).
Ask About Current Events
A bonus of reading the news is that it's currently unfolding. So even if you know less about politics so far than the others, you could still contribute by bringing up current events, or nod when someone else talks about something you've heard about. You could ask questions like, "I'm trying to understand tariffs and I just read that [news update about tariff proposal]. Do you think that proposal is likely to happen? Who do you think would be the winners and the losers if that does go through?"