"Major" is a lot like beauty or trash. What's of major importance to one person may be totally different to another, and vice versa. A scientist would want to know all about medical and space inventions, while a chef would be intrigued by how the invention of the boxed cake mix changed the way Americans cook. Fortunately for all, the 1940s was a decade of inventions of all kinds. Naturally, World War II had a lot to do with many of the inventions, which then found uses in daily life after the war. Some inventions were brand new, while others were invented years earlier but were brought to use in the 1940s.

Warfare and Space Exploration

Mention the 1940s, and World War II is top of mind. The invention of radar enabled Great Britain to surprise the Germans in the Battle of Britain in 1940. The jet engine had been invented in the 1930s but wasn't flight-tested until 1941. Actress and inventor Hedy Lamarr received a patent in 1942 for a frequency-hopping wireless signal that could guide navy torpedoes to their targets. The Navy ignored the invention, however, until its engineers rediscovered it in the 1950s, so it wasn't used in World War II.

The Manhattan Project began in 1942 with the goal of developing the first atomic bomb. It was tested in July 1945 in the New Mexico desert, then dropped over Hiroshima and Nagasaki, Japan in August that year, ending the war. By 1949, the Soviet Union had the weapon as well, and the nuclear arms race was on.

It was Germany that launched the first guided missiles during the war, the V1 and V2. They could be guided to hit a city and terrorized Londoners regularly. At the war's end, the Soviet Union took over the manufacturing center, but the missiles' creator, Wernher von Braun, surrendered to the U.S. He went to work using V2 technology to design rockets for space travel.

Medical Marvels

Alexander Fleming discovered penicillin quite by accident in 1928 and didn't realize what it was for at least a decade. While studying staphylococcus, he neglected to put a petri dish containing staph into the incubator. A mold spore drifted into the room and into the dish. Upon returning from his two-week vacation absence, Fleming was surprised to find the mold had grown into perhaps a topical anesthetic, which he named penicillin. In the 1940s, his associates Howard Florey and Ernst Chain experimented with the penicillin and found that it could fight many bacterial diseases. The three received the Nobel Prize in Physics or Medicine in 1945 for their discovery of penicillin.

After watching patients die from kidney disease, Dutch physician Willem Kolff invented the first kidney dialysis machine, called an artificial kidney, in 1943. The first synthetic fillings for tooth decay were invented in 1944.

Post-War Transportation

The benefits of the tough, hardworking German jeep during the war made the U.S. Army put out the call for a four-wheel drive vehicle that could carry 600 pounds, clear the ground by at least 6.25 inches and wouldn't overheat; and they wanted it in 49 days. The jeep made a huge difference in the war; it could be dismantled, shipped anywhere and rebuilt. Civilian jeeps hit the market in 1945.

The invention of synthetic rubber in the early 1940s contributed greatly to the availability of Jeeps during the war. Tires had been made by natural rubber, and the Axis powers kept the rubber from being shipped to the U.S. Synthetic rubber ended America's dependence on other countries for rubber during the war and after.

Computer Innovations 

A German scientist named Konrad Zuse invented the world's first programmable computer, called Z3, in 1941 in his parents' living room. It read its programs off of punched film. In 1944, Dr. Howard Aiken of Harvard designed the Mark I, the first computer to perform long calculations automatically. It was built by IBM. The Electronic Numerical Integrator and Computer, the world's first electronic digital computer, was proposed by physicist John Mauchly in 1942 and was introduced to the public in 1946. The first computer to run at electric speed, it contained 18,000 vacuum tubes and burned one out every day or two.

Daily Living and Entertainment

The year 1948 heralded inventions that would change lives forever. A young engineer at CBS, Peter Goldmark, invented a three-color wheel that could spin and create the colors produced by the camera. CBS presented the idea to the Federal Trade Commission which, pressured by RCA, ruled the device wasn't ready for use yet. Instead, it was picked up by Smith, Kline and French pharmaceuticals as a teaching tool, televising operations from the University of Pennsylvania.

That same year, Bell Labs revolutionized electronics by replacing vacuum tubes with transistors. Polaroid's 95 Land Camera, invented by Edwin Land, brought to the public the ability to produce instant photos in 60 seconds.

It may seem as if M and Ms have existed forever, but in fact, they made their debut in 1940. Ditto for boxed cake mixes, which came on the market in 1949.

In 1943, the aqualung, which was later renamed SCUBA, made deep water diving a possibility for anyone. The once-favorite toy, Slinky, came to market in 1947; the Frisbee in 1948; and Silly Putty in 1949.

As it turns out, the microwave oven, which certainly revolutionized cooking, shares something with penicillin. It, too, was invented by accident. Percy Spencer, an engineer at Raytheon who held several patents in magnetrons used for radar, was testing the power of one when he noticed something odd. He reached into his pocket for his peanut cluster bar and realized it had melted. He continued to test with eggs (they exploded) and corn (sharing fresh popcorn with his co-workers). The Radarange, weighing in at almost 750 pounds, was available in 1947 for just under $2,000. It would be two decades before the appliance could be made light enough and cheap enough for consumer use.