It was October 18, 1968, and as the battle for civil rights raged on American soil, these two sprinters had dragged the fight on to the most global of stages.
Carlos and Smith's protest at the Olympic Games in Mexico City - after they finished third and first respectively in the 200m final - was one of the most iconic moments of the 20th Century.
Carlos was just 23 when he made his stand, and it cost him everything. With his reputation ruined, he struggled to find a job, his children were bullied at school and nine tortuous years later, his wife Kim took her life. By then, their marriage had broken down.
Carlos, now 71, believes her death was partly the result of the endless interference of the FBI, which had put him under constant surveillance since his return to the United States.
As much as Carlos' story is one of bravery and courage, it is also about sacrifice. In the years since, it is a sacrifice that other athletes have been largely unwilling to replicate. But now, with US racial tensions again rising to the fore Carlos believes change is on the way.
Citing the death of Freddie Gray in April last year, after suffering severe spinal cord injuries in the back of a police van, and the Charleston shooting a few months later, when nine black people were killed in a church, Carlos is "appalled" by the race problems sweeping America.
He supports the Black Lives Matter campaign, which has gained momentum in recent months following the deaths of black men Philando Castile and Alton Sterling at the hands of police officers.
"It's the same difference," Carlos says when asked how these troubles compare. "The fight is going to go on."
The question is whether it will be fought by athletes.
In this era of agents, sponsorship and proclamations about "brand values", it seems the weight of the establishment is heavier than ever.
As spelled out by Rule 50 in the Olympic Charter, "no kind of demonstration, religious or racial propaganda is permitted in any Olympic sites, venues or other areas".
And such is the primacy of sports brands in the US that an athlete's kit supplier is listed alongside their name on results sheets, and is often read out when they are announced to the crowd before competition.
If the silence in that Olympic Stadium in 1968 was one of fear for Carlos, then the relative silence of his successors - the only overtly political act in Rio was the refusal of an Egyptian judoka to shake the hand of an Israeli opponent, which resulted in his being sent home by his team - is a source of great frustration.
"The only way we are going to win this thing is through people turning up their voices. The entertainers and the athletes, those are the public figures you see and hear every day.
"If they say something, people are going to stop and listen," he says.
Across the Atlantic, Carlos believes it is starting to happen. The days when athletes were cowed by sponsors are gone, he says.
American runner Nick Symmonds is leading the campaign against strict sponsorship and advertising rules, and stars such as Serena Williams and basketball player Carmelo Anthony are at the forefront of a new, politically active generation of sportspeople.
Carlos and Smith have been welcomed back as heroes at their old university, California's San Jose State. A larger-than-life statue of their protest was unveiled there in 2005 and they were awarded honorary doctorates. Last week they were invited back for the relaunch of the track and field programme.
"We did not go to Mexico to become legends," Carlos says, but such status is a consequence of what he and Smith did in 1968.
"There are only certain people who everyone remembers winning," Carlos says.
"You might get one or two like Usain Bolt, but there are many who get their 15 minutes in the sun and that's all they get. What happens when their Olympic light goes out?"
After the death of his wife in 1977, Carlos fell into depression. Eventually life began to change. He was helped by his second wife, Charlene, and by finding work in 1985 at Palm Springs High School in California, where he coached track and field and became a guidance counsellor until retiring.
Recognition took a long time, but there is no doubt in Carlos' mind that he would do it all again.
"What I did was right 48 years ago and 48 years later it has proven to be right," he says. "In 1968 we were on a programme for humanity - we are still on the same programme today."
