The tide of the civil rights movement changed in August 1963 when over 200,000 people joined the March on Washington for Jobs and Freedom, rallying for civil and economic rights for African Americans. At that march, Dr. Martin Luther King, Jr. gave his “I have a dream” speech, which changed our lives. I was ten years old. Now, along with hundreds of thousands of other people, I will march in Washington on January 21st, the day after the inauguration of Donald Trump as President of the United States, because the progress we have made towards that dream is under threat. I will stand up for women, for people of color, for immigrants, for all marginalized voices, for universal health care, for the environment, for justice, and for science. In my immediate group, I will stand with three other scientists, my sociologist daughter, Anna Mueller, my feminist economist sister, Diana Strassmann, and my cell biologist brother-in-law, Claudius Vincenz, along with other friends and family members.

In his campaign, Mr. Trump went to unprecedented lengths to demonstrate his disrespect for human beings and for scientific evidence. Both are extremely dangerous in a president. I object strongly to his contempt of immigrants, people of color, the disabled, and women. As a scientist, I object to his unfounded assertions, including those on climate change, the impact of Planned Parenthood on the lives of women and children, and the Affordable Care Act, to name just a few. His statements during the campaign received the lowest scores from independent fact checkers that have ever been seen on in a national campaign for our nation's top office.

Mr. Trump and his team make many specific assertions that disregard evidence about issues vital to women, children, families, and the environment. They wish to repeal the Affordable Care Act, ignoring over 16 million formerly uninsured Americans who now have health insurance. The temperature of the earth is rising faster and faster due to human activities that pump carbon dioxide and methane into the atmosphere. The increasing damage to the environment and to human lives is enormous. Yet Mr. Trump has named a climate change skeptic to head the Environmental Protection Agency and threatens to withdraw the US from the historic Paris agreement on climate change. Decisions not based on evidence that are instead based on prejudice, personal preference, or ideology are bad decisions.

The ethos of science says that no individual has the knowledge and expertise to evaluate all theories. We are far more likely to get useful information from a climate scientist who has devoted her life to studying the climate and who puts her scientific reputation on the line with every word she writes about it than from someone who simply has an opinion. Yet Mr. Trump relies on his own intuition, his relatives, and his business associates, for guidance rather than experts. Simply witness his uninformed and baseless denial of Russia’s interference in the 2016 presidential election.

Now, more than ever, scientists must embrace the challenge and responsibility to communicate clearly and accurately with the public in ways that make the practical significance of scientific results clear. Social science in particular can help with understanding the complex interface between people’s beliefs and policy. For example even climate change deniers might favor actions for solar and wind power that mitigate climate harm if they are also economically beneficial.

The importance of science, evidence, and facts in developing policy is clear. But that does not mean that there is not room for differences of opinion and belief. Science does not say what people should believe, for example, what you should think about the morality of abortion. But science can inform opinions and beliefs. If you think abortion should be less frequent, ready access to health care that includes birth control will achieve this goal more effectively than reducing access to health care.

We cannot move forward wisely on any issue with an administration that does not respect evidence. These are very troubled times, whatever your political perspective, and so I march as a scientist for policies informed by scientific evidence. As a citizen, I march against an outdated electoral system that puts in power a man who makes unacceptably crass statements, brags about exploitative actions, and lost the popular vote by millions. Marches can make a difference, especially when they are part of a sustained movement. I hope this march marks a recommitment to the vision of Barack Obama and a rebirth of the kind, caring, and well-informed America I love.