Time travel. The idea has captivated humans for millennia. Ancient myths and science fiction imagine rips in the universe, portals that let us observe history before our eyes. What most people do not realize, though, is that they do this every day.
Let’s step back—four hundred years back. In the mid-seventeenth century, astronomer Ole Romer noticed something strange about Jupiter’s moons. When they came close to Earth, the time between their eclipses was short, but when they moved farther away the time in between them was longer. Many scientists at the time believed light traveled instantaneously, that our eyes observed Jupiter and its moons in real time. This meant that the moons’ orbits changed depending on their position relative to Earth. It also made no sense.
Romer, however, proposed a different solution. The time between eclipses varied, he hypothesized, because the light from the moons traveled at a finite speed. When the moons were close, the light reached us quickly, but as they receded it took longer for information to reach us. (Note: while others throughout history had suggested the same idea about light, Romer was the first to measure it). Though his calculations failed to catch on for various reasons, Romer had stumbled upon one of the universe’s greatest secrets: our observations are delayed.
Light travels quickly (approximately three hundred million meters/second or 186 miles/hour), making delays in everyday life irrelevant. Things become interesting, however, when we think on an astronomical scale. It takes light eight minutes to travel from the sun to the Earth and about 4.2 years to make its way to the nearest star. If either of these were to go out, we would not know until their light ceased to reach us. The night sky is a story of the past.
Things become even more mindboggling when we observe galaxies billions of lightyears away. Their light carries information from the distant past, depictions of the early stages of the universe. By glancing at far away objects, we peer into the annals of history, reading as it unfolds before our eyes. The further away we look the deeper into the past we explore. If someone 200 million lightyears away were to glance at Earth, he would see a bunch of dinosaurs running around Pangaea.
So time travel is possible, insofar as watching past events is concerned. We can observe almost any moment in time just by shifting our gaze through the stars. Next time you look up at the night sky, be sure to marvel at the history of the universe. And don’t forget to smile—a future astronomer may at some point be watching.
So what do you think? The fact that we can observe events from the early universe blows my mind. Even crazier is the idea that something somewhere could be watching the dinosaurs right now. Is this as awesome as I think it is? Share your thoughts in the comments below. As always, please like, share, or reblog this post if you enjoy it. That small click really helps me out! Be sure to check me out on Twitter and Facebook as well. Thanks for reading! Don’t forget to subscribe for new content every Wednesday! IT’S FREE!
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Comment question of the week
If you could observe any event in the history of the universe, what would you choose and why? (I’d go with the Big Bang–if it could be observed, that is).