Exploring The Universe: Light-Years Travelled And Counting

The concept of traversing vast distances in space has long been a subject of fascination and exploration. Light years, representing the distance light travels in a year, serve as a unit of measurement to grasp the enormity of the cosmos. While light zips through space at an astonishing speed of 186,000 miles per second, the reality of human space travel paints a different picture. Our fastest spacecraft, Juno, travelling at 165,000 mph, would take over 4,100 years to cover a quarter of the distance to the closest star to our sun. This limitation prompts us to consider innovative solutions, such as acceleration, more efficient engines, and even speculative methods like those seen in science fiction. The challenge of traversing light years underscores the vastness of space and the enduring quest to push the boundaries of human exploration.

Light travels at 186,000 miles per second

The speed of light is so fast that it can be used to measure immense distances in space. A light-year is the distance light travels in a year, which is about 6 trillion miles. Proxima Centauri, our nearest neighbouring star, is 4.2 light-years away.

The speed of light is so fast that it can be used to travel through time. If you could accelerate at 9.8 metres per second squared, you would hit the speed of light in about a year. If you kept accelerating, you could travel billions of light-years in a human lifetime. However, while you might experience a few decades, the rest of the universe would experience billions of years.

The speed of light is also central to Einstein's theory of special relativity. This theory states that as matter approaches the speed of light, its mass becomes infinite. Therefore, the speed of light is a speed limit for the universe.

The speed of light is so important that scientists and science fiction writers spend time contemplating faster-than-light travel. However, this remains in the realm of speculation.

The fastest spacecraft we've ever made will take over 4100 years to travel a quarter of the distance to our closest star

The vastness of the universe is truly mind-boggling. Our closest neighbouring star, Proxima Centauri, is 4.25 light-years away. That's 24 trillion miles or 38.6 trillion kilometres. To put that into perspective, if an airline offered a flight there by jet, it would take 5 million years.

Now, consider this: the fastest spacecraft we've ever made, Juno, travels at 165,000 mph. Even at this speed, it would take over 4,100 years to travel a quarter of the distance to our closest star. That's a staggering length of time, especially when you consider that the pyramids were built around 4,500 years ago.

To put it simply, a light year is an incredibly large distance, and our spacecraft don't go very fast in comparison. Even our fastest deep-space probes only travel at a tiny fraction of the speed of light.

It's not just a matter of accelerating to go faster. As an object approaches the speed of light, its mass increases, requiring more and more energy to continue accelerating. Theoretically, to reach the speed of light, an object with mass would need an infinite amount of energy, which is impossible.

To travel great distances in a shorter amount of time, we need much better propulsion technology. We need to be able to go much faster so that our technology can survive the trip. For example, we couldn't send a probe to Proxima Centauri with our current technology because its electronics wouldn't survive a 20,000-year hibernation, and humanity might not either.

While it's fascinating to contemplate travelling vast distances in a short amount of time, the reality is that with our current technology, it would take thousands of years to travel even one light year. Our fastest spacecraft, the Voyager 1 probe, has only travelled 0.0019 light years in 40 years.

Time dilation means that while you might experience a few decades of travel, the rest of the universe will experience billions of years

Time dilation is a phenomenon that occurs when two clocks are moving at different velocities relative to each other. It is described by the theory of relativity, which was developed by Albert Einstein in 1905. According to this theory, the speed of light is always constant, no matter the velocity of the observer. This has some mind-bending implications for time.

Imagine you are travelling through space at close to the speed of light. From your perspective, you are moving incredibly slowly, and so is everyone else. But to those on Earth, you are moving incredibly fast—and time is passing much more slowly for you than for them.

If you were to accelerate at 9.8 meters per second squared, you could travel billions of light-years in a human lifetime. However, while you might experience only a few decades of travel, the rest of the universe would experience billions of years. By the time you arrived at your destination, the Sun would have died out billions of years ago.

The effect of time dilation is negligible at common speeds, such as that of a car or a jet plane. But as you approach the speed of light, the differences become more pronounced. For example, if you were to travel to the centre of the Milky Way, 28,000 light-years away, at a constant 1G acceleration, only 20 years would pass for you. But back on Earth, 28,000 years would have gone by.

Time dilation has been repeatedly confirmed by experiments, such as the Pound-Rebka experiment in 1959, which measured the gravitational redshift of light at different altitudes. It also has practical applications, such as in the operation of satellite navigation systems like GPS.

Light-years are used to measure the vast distances of space

A light-year is the distance light travels in one year. Light zips through interstellar space at 186,000 miles (300,000 kilometres) per second and 5.88 trillion miles (9.46 trillion kilometres) per year. Light-years are used to measure the vast distances in space. Our galaxy is a gravitationally bound collection of stars, swirling in a spiral through space. It is one of about 2 trillion galaxies in the observable universe. Our galaxy is about 100,000 light-years across. That sounds huge, and it is, at least until we start comparing it to other galaxies. Our neighbouring Andromeda galaxy, for example, is some 220,000 light-years wide. Another galaxy, IC 1101, spans as much as 4 million light-years.

The fastest spacecraft we've ever made (Juno, at 165,000 mph) would take over 4,100 years to travel a quarter of the distance to the closest star to our sun. Even using the best theoretical propulsion technology, we don't expect to be able to send anything faster than a few dozen per cent of the speed of light. Making even 'short' journeys to nearby star systems would require transit times of decades or hundreds of years.

However, if we could somehow accelerate at 9.8 metres per second squared, we could hit the speed of light in about a year. We could then travel across billions of light-years within a human lifetime. For example, a trip to the centre of the Milky Way, located about 28,000 light-years away, would take only 20 years from the traveller's perspective. But back on Earth, 28,000 years would have passed.

We can travel light years, but with our current propulsion technology, it would take thousands of years

Light travels at an astonishing speed of 186,000 miles per second (300,000 km/sec) or 5.88 trillion miles (9.46 trillion km) per year. This unit of distance, the light-year, is used to measure the vast distances in space. While it is theoretically possible to travel light years, our current propulsion technology is insufficient.

The fastest spacecraft we have built, Juno, travels at 165,000 mph. This speed would take over 4,100 years to travel 1 light year, which is only one-quarter of the distance to the closest star to our Sun. To put this into perspective, it would take 16,000 years to reach our nearest neighbouring star, Proxima Centauri, which is 4.25 light years away.

To travel at the speed of light, one would need infinite energy, as the closer an object gets to the speed of light, the more energy it requires. This is because the faster an object travels, the heavier it becomes, and thus, the more energy it consumes. Therefore, with our current technology, it would take thousands of years to travel light years.

However, it is important to note that time dilation occurs when travelling at near-light speeds. This means that while a traveller might experience a few decades of travel, the rest of the universe would experience billions of years. For example, if one were to travel to the nearest star, Proxima Centauri, it would feel like 3.5 years have passed, but on Earth, almost 6 years would have gone by.

To overcome the limitations of our current propulsion technology, we need to develop more efficient engines that can extract more propulsive energy from fuel. Alternatively, we could explore theoretical options such as laser fusion rockets or the Orion drive, which uses nuclear bombs. By improving our propulsion technology, we can travel much faster, covering longer distances in a shorter time, thus making long-distance missions feasible.

Frequently asked questions