(CNN)You've been hearing about it all day -- Donald Trump's call for barring all Muslims entering the United States.
Imagine a ban on Muslims: What would United States look like?
The Republican Party's front-runner in the race for the presidential nomination has been met by sharp critiques, even from within his own party. But the idea is not without its supporters.
Trump explained his logic this way: A total and complete shutdown of Muslims entering the country until the U.S. government can figure out "what is going on." The ban would affect not just foreigners who want to immigrate to the United States, but tourists and students seeking temporary visas.
If Trump's suggestion became reality, what would happen?
Here's a hypothetical: If a Trump-like ban on Muslims had existed in decades past, what cultural influences, economic successes or advancements might the United States have missed out on?
Can you imagine a Chicago skyline without the Willis (formerly Sears) Tower or the John Hancock Center? These are just two of the buildings designed by the late Fazlur Rahman Khan. Considered a visionary in his field, his designs changed the way high-rise structures were built.
Khan's design for the Sears Tower (110 stories) made it the world's tallest building until 1996.
He was born in 1929 in what is today Bangladesh and came to the United States for the first time on a Fulbright Scholarship.
A practicing Muslim, Rahman helped engineer the Hajj Terminal at the airport in Jeddah, Saudi Arabia, which is designed to facilitate the arrival of tens of thousands of pilgrims heading to Mecca.
The proud city of Houston has a number of professional sports championships to boast: The now-defunct Houston Comets won four WNBA Finals in a row, and the pro soccer team, the Houston Dynamo, won the MLS Cup back to back.
But what is a Houston fan most likely to brag about first? The Houston Rockets' 1994 and 1995 NBA Championships. Among the three most popular leagues -- the NFL, NBA and MLB -- the Rockets provide the sole major championships for Houston.
Think Houston would have won those championships without Hakeem Olajuwon?
The 7-foot center did not win those titles alone, but was the most important player on the team. Long before he hung up his sneakers, it was widely accepted that Olajuwon would become a Hall of Famer.
He fasted during Ramadan, even during grueling matches. And when those championships came, Olajuwon reportedly skipped the champagne bath in the locker room and instead waited on the court.
He was inducted into the Hall of Fame in 2008. The Islamic Circle of North America celebrated the announcement, saying Olajuwon "consistently set an example for Muslims and Muslim youth by upholding the principles of Islam."
If he had been banned from immigrating to the United States from his native Nigeria because of his religion, the "Dream Shake" would have only existed in our imaginations.
In this hypothetical world, would iconic musicians like Ray Charles and Aretha Franklin have found their place in history regardless? Maybe.
But thankfully the discovery of Charles and Franklin wasn't left to chance. Ahmet Ertegun, the founder of Atlantic Records, saw greatness in them and signed them. His ear for a hit didn't stop with R&B.
American and British artists signed by Ertegun included the Rolling Stones, Led Zeppelin and Crosby, Stills, Nash and Young.
Ertegun was born in Turkey. His father was a diplomat, and the family moved to the United States when Ertegun's father was named ambassador to the United States.
Would a ban on Muslims have prevented his family from moving to Washington? We can speculate that Muslim diplomats would be allowed, but also imagine that Ertegun's family would not have been allowed to stay once the ambassadorship was over.
Instead, Ertegun and his brother Nesuhi stayed in the United States and went on to found one of the greatest record labels.
The year after his death, Led Zeppelin held a one-of-a-kind reunion and played in a tribute to Ertegun.
When asked about his religion in an interview once, Ertegun described himself as a "Muslim by birth," hinting at a complicated relationship with religion.
Dr. Qanta Ahmed has the type of American success story that, some would say, make this country great.
She's a foreign-born pulmonologist, internist and sleep specialist who has utilized her U.S. education to help people around the world as a medical expert and author. And she is Muslim.
Ahmed, who grew up in London and practiced medicine in Saudi Arabia, was medically trained through a special immigration visa program for doctors in the 1990s. Now living and working in New York, she will formally become an American citizen on Friday, for which she feels "extraordinary privileged."
Ahmed called Donald Trump's Muslim travel ban "a complete departure from American values," saying it contributes to the dehumanizing of Muslims without differential.
"It doesn't just promote xenophobia. ... It also is the fuel and food on which all Islamism breathes and becomes stronger. And that is that Muslims are under siege in the secular west," she told CNN's "New Day."
Ahmed said the issue is not really about immigration.
"It's about making us all into one group. One other that is to be feared and excluded. That's highly dangerous," she said.
Muslims make up a fraction of U.S. service members, which reflects the fraction of Muslims that make up the U.S. population as a whole. Still, the contributions of Muslims to the U.S. armed forces is not insignificant.
The exact number of Muslims serving in the U.S. military is not known, in part because religion is self-reported. But estimates range from 4,500 to 5,500.
Some of these troops are American Muslims or immigrants who became naturalized U.S. citizens. For the purposes of a scenario where a ban on Muslims existed in the past, it is safe to assume many of these service members would not have been able to fight for the United States, either because they would not have been allowed to immigrate into the United States, or because their parents would not have been allowed to immigrate.
"We certainly have Muslims serving in uniform right now," Pentagon spokesman Peter Cook said Tuesday.
Asked specifically about Trump's comments, Cook said: "The United States doesn't have any issue, and certainly the Department of Defense, anything that creates tensions and creates the notion that the United States is at odds with the Muslim faith and Islam would be counterproductive to our efforts right now, and totally contrary to our values."
The significance of Muslims in the U.S. armed forces is not just kind words in speeches.
Consider the story of Kareem Rashad Sultan Khan. He was born in New Jersey to immigrant parents, joined the Army and was killed in Iraq in 2007.
Khan and three other soldiers were killed by a bomb while they searched abandoned homes for explosives.
In an interview with Gannett News Service, Khan's father said the young man joined the Army because of his memories of 9/11.
"His Muslim faith did not make him not want to go. It never stopped him," Feroze Khan said. "He looked at it that he's American and he has a job to do."
Khan is buried at Arlington National Cemetery.
Through his comedy, his book on modern romance and his show "Master of None," Aziz Ansari has emerged as one of the distinct voices of aging millennials. Being a minority in America, balancing work and relationships, being one with your smartphone, he gets it.
Ansari was born in South Carolina, so, hypothetically, he would not be subject to an across-the-board ban on Muslims from abroad.
But in this thought experiment, it's fair to imagine that his parents would not have been able to immigrate from India. Ansari's observations on youth and culture, in this alternate history, would have been shaped more by Chennai and less by New York.
Ansari, an atheist, has proved to be a staunch defender against Islamophobia. His Twitter remarks slamming Rupert Murdoch for anti-Muslim remarks went viral.
In the make-believe America where Muslims are banned, maybe we would still have Aziz Ansari's comedy.
But his father (who also plays his father on "Master of None"), whose scene-stealing in the show has garnered praise, would have been stopped by Trump at the gates.
And that would have been a shame, because even though it is just a TV show, Shoukath Ansari's is an American story, too. His character's advice on the show: "You have to learn to make decisions, man," is one that resonates with any child of immigrants, or any American, for that matter.