Interesting question! According to Albert Einstein, traveling at or exceeding the speed of light isn't possible. But let's imagine for a moment that we have a spaceship capable of light-speed travel and want to visit the Andromeda Galaxy, our nearest spiral galaxy.
The Andromeda Galaxy is close by cosmic standards—only 2.5 million light years away. To put it into perspective, a light year is the distance light travels in one year, roughly 5.88 trillion miles (9.46 trillion kilometers). So, even at light speed, it would still take 2.5 million years to get there.
The vast distances in space are truly mind-boggling. Andromeda is just our nearest neighbor; there are galaxies hundreds of millions or even billions of light years away. Even at the ultimate speed limit set by physics—the speed of light—reaching these distant galaxies would take an unimaginably long time. It’s safe to say that, for now, intergalactic travel remains firmly in the realm of science fiction.
Which is too bad because wouldn’t it be cool to explore the great expanse between the Milky Way and Andromeda galaxies, where there are very few stars, but there’d be great views of both galaxies? This intergalactic space, often thought of as an empty void, is actually a realm in outer space filled with subtle wonders. While it's true that the density of stars and other celestial bodies drops off dramatically in these regions compared to the bustling interior of a galaxy, the space between galaxies—called the intergalactic medium—still holds fascinating mysteries.
Imagine traveling through this vast, near-empty expanse. With galaxies like Andromeda and the Milky Way dominating the view on opposite horizons, the vista would be breathtaking. The sky wouldn't just be a dark canvas speckled with stars—it would be punctuated by the grand spirals of entire galaxies, shining faintly but majestically.
There are stars between galaxies, though they are relatively rare. These stars, known as intergalactic stars or intracluster stars, exist outside the boundaries of any particular galaxy. They are scattered across the vast expanse of space between galaxies, often within galaxy clusters. Galaxies frequently interact gravitationally. These interactions can eject stars from their parent galaxies, flinging them into intergalactic space. I wonder if any of them have exoplanets in habitable zones. The view at night for those aliens would be much different than our view inside the Milky Way.
This space is also home to the mysterious phenomenon of dark matter and dark energy. The gravitational pull of dark matter helps bind galaxies together in clusters, while dark energy drives the universe’s accelerated expansion. Exploring the intergalactic void might offer insights into these cosmic puzzles, which remain some of the greatest mysteries in physics.
Intergalactic space is not entirely devoid of matter. It’s filled with tenuous gas, primarily hydrogen, and scattered particles that were either ejected from galaxies or left over from the early universe. This medium might seem insignificant, but its sheer volume across the cosmos means it plays a crucial role in the universe’s structure and evolution.
Our current technology isn’t even close to achieving light-speed travel. The fastest spacecraft we've built to date, the Parker Solar Probe, zips around the Sun at about 430,000 miles per hour (700,000 kilometers per hour). But at that pace, it would still take billions of years to reach Andromeda.
To put this into perspective, even if we aimed to reach the nearest exoplanet, Proxima Centauri b, it would take approximately 6,634 years traveling at 430,000 mph. And that's just within our galaxy, which contains billions of planets orbiting billions of stars.
Beyond speed, intergalactic travel has some other difficulties. We would need sustainable life support systems, protection from cosmic radiation, and an immense amount of energy for propulsion, and that’s simply the tip of the iceberg.
While the idea of traveling to another galaxy is fascinating and a staple of science fiction, the reality is that, with our current understanding of physics and technology, intergalactic travel is not just improbable—it’s impossible. The sheer vastness of space and the constraints imposed by the speed of light make such journeys unattainable not only in one human life, but even the spaceship would break down after thousands of years. For now, we can only look, not touch.
Another fun layer of complexity is time dilation. At speeds approaching the speed of light, time would pass much slower for the travelers than for those left behind. A trip to Andromeda at near-light speed might feel like a few years for the crew, but millions of years would pass back on Earth. They'd return (if ever) to a world unrecognizably changed. A spacecraft would need to travel at approximately 99.999999995% of the speed of light for passengers to experience only 25 years of travel time between the Milky Way and Andromeda galaxies, due to relativistic time dilation. This highlights the extreme velocities required to achieve such significant effects. This wouldn’t violate the laws of physics, but getting to that speed would. We have no technology to even get to 1% the speed of light, what to speak of 99.999999995% of the speed of light. But it’s a fun thought.
Sadly, perhaps, the only journeys to other galaxies will be in our minds, through science fiction, or as a distant dream for civilizations far more advanced than ours. It’s a reminder of the scale of the universe and how small we are in comparison. Dream on.