What’s The Point Of Theoretical Physics?

 

You don’t have to be a physicist to get excited about breakthroughs in theoretical physics. Discoveries such as gravitational waves and the Higgs boson can motivate wonder at the complex beauty of the universe no matter how slight you really understand them.

 

But some will always question why they should care about scientific advances that have no obvious impact on their daily life – and why we spend millions funding them. Sure, it’s incredible that we can study black holes thousands of light years away and that Einstein really was really as much of a genius as we thought, but that won’t change the way most people live or work.

 

Yet the reality is that only theoretical physics can sometimes lead to wonderful changes in our society. In fact, several key pillars on which our modern society rests, from satellite communication to computers, were made possible by studies that had no obvious application at the time.

 

Quantum Leap

 

About 100 years ago, quantum mechanics was a purely theoretical topic, only established to understand certain properties of atoms. Its founding fathers such as Werner Heisenberg and Erwin Schrödinger had no applications in mind whatsoever. They were merely driven by the journey to understand what our world is made of. Quantum mechanics states that you cannot detect a system without changing it fundamentally by your observation, and primarily its effects to society were of a philosophical and not a practical nature.

 

But today, quantum mechanics is the foundation of our use of all semiconductors in computers and mobile phones. To build a modern semiconductor for use in a computer, you have to understand concepts such as the way electrons behave when atoms are held together in a solid material, something only defined correctly by quantum mechanics. Without it, we would have been stuck using computers based on vacuum tubes.

 

 

 

GPS: a relative success. Shutterstock

 

At a similar time as the key developments in quantum mechanics, Albert Einstein was trying to better understand gravity, the dominating force of the universe. Rather than observing gravity as a force between two bodies, he defined it as a curving of space-time around each body, similar to how a rubber sheet will stretch if a heavy ball is placed on top of it. This was Einstein’s general theory ofrelativity.

 

Today the most common application of this theory is in GPS. To use signals from satellites to locate your location you need to know the exact time the signal leaves the satellite and when it arrives on Earth. Einstein’s theory of general relativity means that the distance of a clock from the Earth’s centre of gravity affects how fast it ticks. And his theory of special relativity means that the speed a clock is moving at also affects its ticking speed.

 

Without knowing how to adjust the clocks to take account of these effects, we wouldn’t be able to accurately use the satellite signals to determine our position on the ground. Despite his amazing brain, Einstein probably could not have imagined this application a century ago.

"That … in general relativity, can be understood, actually, as the effect of space-time curvature," Roura told Space.com, referring to one of Albert Einstein's most famous theories.

 

As the atom that went higher was closer to the ring, it experienced more acceleration thanks to the ring's gravity. In a perfectly constant gravitational field, such effects would cancel out. That isn't what happened here; the atoms' wave packets were out of phase instead, and thanks to the effects of time dilation, the atom that experienced more acceleration was ever so slightly out of time with its counterpart.

 

The result is a miniature change, but atom interferometry is sensitive enough to pick it up. And since the researchers can control the placement and the mass of the ring, Roura told Space.com, "they are able to calculate and study these effects."

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References:

The Conversation