Ever notice President Obama's hair -- and how gray it's gotten over the last eight years? It's not because he joined the Gray Hair Club for Men. Instead, it probably has to do with the knowledge that he has the awesome ability to destroy the entire world dozens of times over -- and the responsibility to make sure that never happens. This despite a hair-raising array of threats that range in size from China and Russia all the way down to North Korea or some crazy terrorist with enough dough to buy a "suitcase bomb" or radioactive waste from some rogue state.

George W. Bush, for better or worse, wasn't afraid of using U.S. military force, but it sure sounds like America's vast nuclear arsenal scared the heck out of him. "I had no idea we had so many weapons," he told a briefer after taking office in 2001, according to Newsweek magazine.

"What do we need them for?" If only W. had been that inquisitive about those weapons of mass destruction that weren't in Iraq.

Anyway, times have changed. On  January 20, America will inaugurate a new president with no apparent worries about the number of nuclear weapons in the possession of either the United States or its superpower allies and no feel for the devastating fallout -- pun intended -- if nukes were to be used in combat for the first time since Hiroshima and Nagasaki in 1945. To the contrary, Donald Trump -- according to the presidential megaphone of Twitter -- doesn't think America's weapons cache is big enough.

"The United States must greatly strengthen and expand its nuclear capability until such time as the world comes to its senses regarding nukes," Trump tweeted. He didn't offer any additional details. He never does. But his vague words held out the promise of reversing a U.S. policy course that dates back to the late 1960s and Richard Nixon.

Ironically, Trump's tweet followed closely a pronouncement by Russian president Vladimir Putin, who has the keys to the world's second-largest nuclear stockpile, that his nation is working on modernizing its atomic arsenal to "reliably penetrate any existing and prospective missile defense systems." This all comes at a perilous moment when citizens -- not just of the United States but of the entire world -- are wondering whether America and Russia are launching a new Cold War or whether Trump and Putin have instead formed a dark alliance against Western-style liberalism.

The one thing I know is this: No one believed that we were voting on November 8 for a return to the days of fallout shelters and those classroom drills where kids learned to put their head between their knees and kiss their butts goodbye. The present moment feels slightly terrifying -- and let's just say that reassurance isn't Donald J. Trump's greatest quality. There's another thing I can say with some certainty, which is that Ronald Reagan would be spinning in his grave if he could witness Trump's cavalier attitude on nukes.

Yes, that's ironic, because -- as I remember well from my college days -- a lot of people worried at one time that Reagan would be the U.S. president to start a nuclear war. After all, the Gipper had once said his plan for Vietnam would be to turn that nation into a giant parking lot (a fitting metaphor for a Californian), and once in the White House he rattled more nerves when he referred to Moscow as "an evil empire."

But things began to change rapidly around 1983, just two years into his presidency. A series of war games involving the U.S. and the USSR brought the two nuclear superpowers closer to actual combat than the public realized at the time. Ironically, that same month, ABC aired the now legendary TV movie The Day After, which showed the grim aftermath of an all-our nuclear war and the struggles of people in Lawrence, Kansas, to survive the loss of friends, family and the civilized world they once knew. One of the millions of Americans who watched The Day After was the former Hollywood actor, Ronald Wilson Reagan.

"It is powerfully done, all $7 million worth. It's very effective and left me greatly depressed," Reagan wrote in his diary after a private screening of the movie at Camp David. "Whether it will be of help to the 'anti-nukes' or not, I can't say. My own reaction was one of having to do all we can to have a deterrent & to see there is never a nuclear war." Just two months later, in a nationally televised speech, the then-president said "my dream is to see the day when nuclear weapons will be banished from the face of the earth."

Remarkably, he spent the next five years doing as much as he could to make that vision a reality. I wrote about it in my 2009 book, Tear Down This Myth. Here's an excerpt:

When a crisis of aging Soviet leadership was finally resolved in 1985 with the ascension of Mikhail Gorbachev -- himself soon motivated to seek sweeping change by the nuclear power disaster at Chernobyl -- the two world leaders embarked on a series of remarkable summits aimed largely at nuclear arms reduction. When they met in Reykjavik in October 1986, they even entertained a radical proposal to eliminate all nuclear weapons, although it foundered on Reagan's refusal to give up another cherished personal vision, his notion of a high-tech weapons shield. That meeting did lay the groundwork for an agreement fourteen months later to eliminate all of those intermediate-range nuclear weapons in Europe. Today you can see the Pershing II and the SS-20 right next to each other -- in the Smithsonian Institute, where most would agree such lethal weapons belong.

When that treaty was inked, a Reagan associate sent a telegram to the director of The Day After: "Don't think your movie didn't have any part of this, because it did." Maybe the presidency will change Trump in some of the ways that it changed Reagan -- but that's hard to imagine right now. All we know is what Trump said on the campaign trail in August, when he responded to a comment by MSNBC's Chris Matthews that Americans don't want to hear the president speak about using nuclear weapons: "Then why do we have them?" Trump asked.

At one point in the 1980s, Trump actually said that Reagan's nuclear-arms negotiators were too soft and offered to replace them; not much later he blasted The Gipper as an "effective...performer" in the White House with little substance. Running for president as a Republican in 2016, of course, he had nothing but praise for the late 40th president, and Trump's lack of a political background has brought some Reagan comparisons that are more than a little forced, especially when one remembers that Reagan had eight years of experience as governor of the nation's largest state when he was inaugurated.

The differences don't end there. Reagan also offered a pathway to citizenship for undocumented immigrants, often turned down his advisors' calls for military action from Panama to the Middle East, fearing collateral damage to civilians, and signed a treaty meant to eliminate torture. It was a time when a principled hard-core conservative could see shades of gray, learn new things on the job, and cultivate the "art of the deal" with opposition leaders like the Democrats' Tip O'Neill. A time that seems quaint in a world where Trump's Twitter thumbs will soon be on the nuclear button. For someone who considers himself the "Merry Christmas president," Donald Trump has a lot to learn about peace on earth and goodwill toward humankind.

Blogger's note: On those words, I wish everyone a happy holidays AND a merry Christmas... so there! I'll be back on Dec. 27 with Attytood's annual look back, on that most wonderful time of 2016.