Deutsche Welle – From the conference's opening session, President Trump and the new US administration were high on the agenda.
"Some members of our community who had planned to attend this meeting have not been able to or decided not to travel to the US," said Geraldine Richmond, professor of chemistry at the University of Oregon and Presidential Chair of the American Association for the Advancement of Science (AAAS).
At their annual meeting, nearly 10,000 members of the AAAS - scientists, policymakers and science communicators - have come together in Boston.
But some scientists from abroad are missing, "due to travel uncertainties resulting from the January 27th White House executive order on immigration and visa," Richmond tells the audience.
Even though the immigration ban for seven countries including Sudan has been suspended by the court, some scientists felt it was better not to risk traveling.
Rania Mokhtar from Sudan University of Science and Technology is among them. At the AAAS Meeting she would have received an award for her excellent research as an early-career female scientist in the developing world. Now she will be attending the meeting via a web conference.
Before the conference started on Thursday, some scientists speculated on social media whether this year's meeting would be different, saying they would be "greatly disappointed if it was just business as usual".
But those who expected demonstrations and provocative posters will be disappointed. After all, this is a science conference.
Buttons saying "Stand up for science", an open letter to Trump available to sign, newly added conference sessions on science policy under the Trump era - this is how scientists react when they feel threatened - for a start, at least.
"We have tried to convince the president [that science is important]," AAAS CEO Rush Holt told DW. "We have sent letters offering to help. Also, we sent a letter saying that the immigration ban for these seven designated countries is a bad idea."
Up to now, those letters have had no effect.
Rush Holt is particularly concerned about the fact that Donald Trump is yet to appoint the traditional White House science advisor.
"We hope that we can get the president to understand that the science advisor will help him with [any] crisis - whether it is an oil-well blow-out or an emerging disease."
"Science is in danger"
But even though the scientists' resistance is civilized, it is still strong.
Everybody at the AAAS Meeting in Boston seems to agree that Trump's position seems to present a threat to science, and that he must be watched closely.
At the opening session, AAAS president Barbara Schaal said, to loud applause by the audience, "We need to make a clear case for the role of science, clearly and forcefully, so that our government understands the critical role that science plays in our lives."
Gretchen Goldman of the Union of Concerned Scientists tells DW that already in those first weeks of Trumps presidency too much has happened.
"We are very worried about science under the Trump administration. Indications so far are that the president and his administration won't respect science, at least as we have understood things so far."
It is concerning, Goldman says, that federal scientists had to use alternative social media accounts to speak to the public. Of further concern is the fact that scientific information has been removed from government websites and that Scott Pruitt is now head of the Environmental Protection Agency, even though he has been suing this very agency for many years as the Attorney General of Oklahoma.
"But we are prepared to push back," Goldman says.
Against alternative facts
The theme of this year's AAAS meeting is "Serving Society Through Science Policy".
The theme was chosen over a year ago, AAAS president Barbara Schaal said, "because we knew that the US would be in the very early days of a new administration." And during those times, "there is always a sense of uncertainty."
But with Republican Trump becoming the 45th president of the US, the situation has worsened.
It is not only about Whitehouse executive orders, AAAS's Rush Holt says. It is about the overall perception of science.
"The biggest story in science right now is the uncertainty about the state of science in our culture and our government. Is evidence still respected? Are so-called alternative facts replacing scientific-based understandings?"
On Sunday at the conference, scientists will dress up in lab coats and officially "stand up for science" at a public rally.
And in April, a globally organized "March for Science" will take place.
Maybe that will be the time when the rather quiet resistance gets louder.