The day was kind in Boston: no more blizzards or Siberian winds. In fact, the sun shone through.

A few hundred demonstrators were already in Copley Square when I arrived 20 minutes early. Hundreds more came by noon, some in white coats, many carrying signs saying "STAND UP FOR SCIENCE" and "WE DON'T WANT ALTERNATIVE FACTS".

All those I questioned said they had never been to such a rally before, and generally preferred to get on with their work, researching or teaching. Some were professors at MIT or Harvard. Sorry, this audio has expired Listen to Robyn Williams' report from Boston

One who addressed the crowd was the famed Naomi Oreskes, professor of the history of science at Harvard.

Others insisted they were not science professionals, only concerned citizens who benefit every day from the results of good research.

Naomi Oreskes, professor of the history of science at Harvard, addressed the crowd. ( Supplied: ClimateTruth.org/Amanda Kowalski )

Boston is science central, with Harvard, MIT, Tufts, Boston University and scores of other institutions doing frontline investigations within a few miles of each other.

Already there are drastic signs of the Trump administration's attempted cuts, sanctions and changes.

When, earlier, I went to MIT to interview Phiala Shanahan, winner of the Bragg Award for the best physics PhD in Australia (she comes from Adelaide and has just been named in Forbes Magazine's Top 30 Under 30 in science) the desk next to her was vacant.

Her young colleague doing postdoc work at the Department of Theoretical Physics is from Iran and had fallen foul of the threatened immigration laws. Dr Shanahan was furious.

Concern about generational damage

John Holdren said he was deeply concerned about the cultural consequences for America. ( Supplied: ClimateTruth.org/Amanda Kowalski )

Before the rally, John Holdren of Harvard, who was President Obama's chief scientific adviser, deplored the way scientists have been painted as "elite" — once a desirable term, now an indication you are remote from the real people out there.

Professor Holdren listed the clear benefits of science to everybody, from better medicine and efficient systems to the devices we all use, crave and can't imagine doing without.

But he also insisted that science creates real wealth, preserves our precious environment and warns us all about the dangers of issues like climate change. His list of concerns was stark.

"So far what we've heard about the economic policy of the new administration is that they want to cut taxes, spend a trillion or 1.5 trillion on infrastructure, boost the defence budget — and if they do all that the numbers simply don't add up," he said.

A family with their signs at the Stand up for Science rally in Boston. ( Supplied: ClimateTruth.org/Amanda Kowalski )

"There is nothing or next to nothing left for discretionary spending other than defence spending and so the R&D spending is the first to go.

"I'm particularly worried about R&D at the Department of Energy, where clean energy and energy efficiency are likely to be slashed — I'm worried, of course, about the EPA, all the more since [new EPA head and climate sceptic Scott] Pruitt's confirmation.

"I am worried about the Food and Drug Administration. I'm worried about the National Science Foundation, which along with the National Institute of Health is the biggest funder of fundamental research."

Hundreds of people turned up for the rally, many of whom had never been to one before. ( Supplied: ClimateTruth.org/Amanda Kowalski )

Professor Holdren said the research under threat encompasses climate change, environmental toxins, particle accelerators, telescopes, high-capacity computing and satellites.

This list is clearly shocking. If Professor Holdren's fears are realised, and they are shared by many I spoke to in Boston, there could be generational damage to US R&D and therefore to international research, including that done in Australia.

Future of science looks grim

But he is also deeply concerned about the cultural consequences for America.

"It is pretty clear by now that we have a President who resists facts that don't comport with his predetermined positions," he said.

"That bodes ill for the emphases on scientific integrity, transparency and public access and fact-based decision-making.

Concerned citizens who turned up to the rally said they benefited every day from the results of good research. ( Supplied: ClimateTruth.org/Amanda Kowalski )

"I think it bodes ill for the continuing presence at the policy-making tables of the government's experts in science and technology. We are, I'm afraid, in for a very rough ride."

If you go to a rally, Professor Holdren urged, or the March for Science planned in cities around the world on April 22, take two friends who are not in science.

"This is for everyone."

His words were supported by Jane Lubchenco, former head of the National Oceanic and Atmospheric Administration.

"My biggest worry is about the consequences to society," said Professor Lubchenco.

"If scientists are muzzled and intimidated, if science is defunded, data are deleted and scientific institutions are undermined, I fear for the health and well-being of scientists and the economy and the environment, and indeed for the future of democracy and of our world."

The Union of Concerned Scientists call themselves the "watchdogs of attacks on science". ( Supplied: ClimateTruth.org/Amanda Kowalski )

Trump has unleased a formidable enemy

Professors Holdren and Lubchenco were speaking at the American Association for The Advancement of Science (AAAS) meeting that finished on Tuesday (AET). The hall was packed, and the crowd overflowed into the corridors and rooms outside.

Four colleagues alongside Professor Holdren and the atmosphere was both angry and exuberant. Trump, it's clear, has unleashed a formidable enemy.

The AAAS was formed in 1848: it is the largest general science meeting in the world, held every February over, ironically, the President's Day holiday.

Science has faced detractors before; this battle is not new. ( Supplied: ClimateTruth.org/Amanda Kowalski )

What the AAAS' founders would have made of such furious public dissent, or of the current administration's threatened wholesale debauching of science, can only be imagined.

Science has faced detractors before; this battle is not new. But this particular skirmish feels different — and it is only just beginning.