# Tag Archives: physics

## Uncharted territory: how big is the universe?

How far is too far? On groggy Sunday mornings, the gym may seem “too far”, while for two long-distance lovers separated by circumstances, they are always “close enough”. For some, distance is relative to our motivation. Space, however, does not care what you think.

Voyager 1. Image from NASA.

It’s been over 35 years since NASA’s launch of Voyager 1, and since then, it has travelled almost 20 trillion kilometers from home. You might think that that’s far, but in the grand scheme of the universe where distances are measured with respect to light, it has travelled a mere 18 light-hours. To put that into perspective, the nearest star to our Sun, Proxima Centauri, is about 4.24 light-years away.

So how big is the universe then?

Before we address that, we need to know how old the universe is. Based on measurements of the cosmic microwave background, which is basically leftover radiation from the Big Bang, astronomers are confident that the universe is about 13.8 billion years old. Since Distance = Velocity × Time and nothing can travel faster than light (?), the universe must have a radius of 13.8 billion light-years, right? Wrong!

The Doppler effect on the pink sound waves. Image from user Charly Whisky from Wikipedia.

The short answer to the size of the universe is that it is at least 93 billion light-years in diameter. The reason that the universe is larger expected is because the universe is expanding. This can be determined by the apparent redshift of distant stars due to the Doppler Effect. So an object emitting light from 13.8 light-years away would have moved to a position much farther away.

One thing to note, is that this measurement is only what we can observe.  The observable universe from another planet billions of light-years away is likely different from our reference frame of the Earth. Is the universe infinite? Perhaps. But for now, we can appreciate that even though our paradigm of the universe is limited, there is still much to explore; we have observed billions of galaxies, and in each are billions of stars, each hosting their own worlds much like ours. Despite the uncertainty in the true size of the universe, we know that space is vast. As the Dutch artist Vincent van Gogh had once said, “for my part I know nothing with any certainty, but the sight of the stars makes me dream.”

If you have 45 minutes to spend exploring part of our Solar System, check out Alphonse Swinehart’s video below, where you travel from the Sun to Jupiter at the speed of a photon! Do yourself a favour and enjoy the video in full screen mode.

– Trevor Tsang

## The Magnus Effect: From Football to Flight

In 1997 during a football match between Brazil and France a Brazilian player named Roberto Carlos scored an “impossible goal”. With no direct line to the goal it seemed unreasonable for him to even attempt for goal 35 meters away, yet with with a good run up and calculated strike he sent the ball flying towards out of bounds, passed the free-kick wall, before curving back into the net, giving brazil the lead. This shot made the 21-year-old player a household name in the sport and left spectators amazed. It seems to defy Newton’s first law of motion, that states: “an object in motion stays in motion with the same speed and in the same direction unless acted upon by an unbalanced force.” The ball’s change in direction meant that must have been some force acting upon the ball causing it to curve back on target. This phenomenon is called the Magnus Effect, named after Heinrich Gustav Magnus who described it in 1852, although it was first documented 200 years earlier by Isaac Newton when playing tennis at Cambridge College.

As the ball moves and spins through the air one side is spinning with the direction of air flow and the other against. The side where air moves opposing the direction of spin causes high pressure. The area where air is moving in the same direction as its spin, the deflected air creates an area of lower pressure. The makes the ball act as a wing as is moves from an area of high pressure to an area of lower pressure, which causes the ball to move in the direction of spin, curving into the goal.

The Magnus Effect affects all rotating balls or cylinders flying through the air, making it an important aspect in ball sports like football, tennis and golf. Nevertheless the Magnus Effect has found several industrial applications in the past making ships sail without sails and planes fly without wings. The image below is a sail boat without sails, instead is has large spinning cylinder called ‘Flettner Rotors’ that deflect cross winds, using the Magnus Effect, to propel the ship forward. Even nowadays there are hybrid ships with flettener rotors in decrease diesel consumption improving efficiency.

Flettner Rotor Sail Ship https://en.wikipedia.org/wiki/Rotor_ship#/media/File:Buckau_Flettner_Rotor_Ship_LOC_37764u.jpg

This idea took to the skies in the early 20th century. The image below is that of a wingless plane, where its wings have been replaced with spinning cylinder. Using the Magnus Effect the cylinders generate more lift than traditional wings, however they do generate a lot more drag making them impractical for aviation. Nowadays the only planes utilizing flettner rotors are small remote controlled model planes.

Flettner Rotor PLane
https://en.wikipedia.org/wiki/Flettner_airplane#/media/File:Flettner_Rotor_Aircraft.jpg

From the football field to the seas, understanding  the Magnus Effect gives for spectacular sport and ingenious design, amazing spectators and increasing efficiency.