My telescope, designed for astrophotography in my light polluted backyard in San Diego, was directed to the galaxy without being far from the ground. My wife Christina climbed just when the first space photo was flocking to my tablet. He shines on the screen before us.
“This is the galaxy of the rotating,” I said. The name is derived from its shape – although this rotating wheel contains about a trillion stars.
The rotating wheel light traveled for 25 million years through the universe – about 150 quintillion miles – to get to my telescope.
My wife wondered: “The light doesn’t get tired during such a long trip?”
Her curiosity sparked a conversation with provoking the thought of light. After all, why does the light not wear and lose energy over time?
Let’s talk about the light
I am an astrophysicist and one of the first things I learned in my studies is how light is often behaved in ways that oppose our intuitions.
The photo of the author of the Pinwheel galaxy. Jarred Roberts
Light is an electromagnetic radiation: in general an electric wave and magnetic wave, combined together and traveling through space-time. There is no mass. This point is crucial because the mass of an object, whether stains of dust or spacecraft, limits the maximum speed it can travel through space.
But since light is oily, it is able to reach the maximum speed limit in vacuum – about 186,000 miles (300,000 kilometers) per second or almost 6 trillion miles a year (9.6 trillion kilometers). Nothing that travels through space is faster. To put this in perspective: in a time that takes you to blink your eyes, a particle of light walks around the Earth’s circumference more than twice.
As incredibly fast, the space is incredibly widespread. The light from the sun, which is 93 million miles (about 150 million kilometers away) from Earth, takes just over eight minutes to reach us. In other words, the sunlight you see is eight minutes away.
Alpha Centaur, the closest star next to us after the sun, is 26 trillion miles (about 41 trillion kilometers). So by the time you see him in the night sky, his light is just over four years. Or, as astronomers say, it’s four light years.
Considering those huge distances, think about Christina’s question: how can light travel through the universe and not lose energy slowly?
In fact, some light loses energy. This happens when something bounces like a interstellar dust and is scattered.
But most of the light just goes and go without colliding with anything. This is almost always because space is mostly empty – nothing. So there’s nothing on the way.
When light travels unobstructed, it does not lose energy. It can maintain this speed of 186,000 miles per second forever.
It’s time
Here is another concept: Introduce yourself as an astronaut aboard the International Space Station. You orb the 17,000 miles (about 27,000 kilometers) per hour. Compared to someone on the ground, your wristwatch will mark 0.01 seconds more slow in one year.
This is an example of expanding time – time to move different speeds under different conditions. If you move really fast or close to a large gravitational field, your clock will note more slowly than someone who moves more slowly than you, or which is further than a large gravitational field. To say it briefly, time is relative.
Now think that light is inextricably linked to time. A picture sitting on photon, a major particle of light; Here you would experience maximum dilation over time. Everyone on Earth would have a clock at the speed of light, but from your reference frame the weather will stop completely.
This is because the time to measure clocks are in two different places that run very different speeds: the photon moving at the speed of light and the relatively slow speed of the earth that goes around the sun.
Moreover, when you travel or close to the speed of light, the distance between where you are, and where you go, it becomes more short. That is, the space itself becomes more compact in the direction of movement -so the faster you can go, the shorter your trip should be. In other words, the background is stuck.
Which brings us back to my photo of the Pinwheel galaxy. From the point of view of a photon, a star in the galaxy radiated it, and then a pixel in my camera in the backyard swallowed it at the same time. As the space was squatting, for photon the journey was infinitely fast and infinitely short, a small part of a second.
But from our point of view on Earth, the photon left the Galaxy 25 million years ago and traveled 25 million light years in space until I landed on my tablet in my backyard.
And there, on a cool spring night, his stunning image inspired a delightful conversation between a nervous scientist and his curious wife.
This article is reissued by the conversation, a non -profit, independent news organization that brings you facts and a reliable analysis to help you make sense of our complex world. It is written by: Jared Roberts, University of California, San Diego
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Jarred Roberts receives NASA funding.