May 16, 201913 min read

How far can we reach?

Updated: Jan 24, 2020

Starship going past the moon/ concept art by SpaceX — Starship going past the moon/ By Spacex from Flickr

As far as the length of our outstretched arm. But that’s not quite the answer most people would be looking for. We are talking along the lines of futuristic prospects of the human race. The concept of the movie interstellar was menacing and promising at the same time for different reasons. But if the earth became uninhabitable in the distant future, will we have found another planet to inhabit?

Our space endeavors began with the launch of Sputnik 1 in 1957, and humans would enter space four years later. In 1969, Apollo 11 landed people on the moon, and with that, our space odysseys flourished. Even though the manned missions to space decreased after the early ’70s, we have sent many probes out there, some of which still relay information to us.

Currently, there are about 25 spacecrafts[1] actively transmitting information to us from various regions of our solar backyard. But out of these, only two have crossed the heliopause boundary[2] into interstellar space. The Voyager 1 and Voyager 2, send as part of the Voyager Interstellar Mission, are soaring through the vast emptiness of interstellar space as we speak. But as far as our reach is concerned, no man-made object is as far from us as Voyager 1. It had recently passed the 13.5 billion[3] mile mark, and to put that in perspective, Voyager 1 would have to go almost 542,000 times around our planet to cover that same distance.

An artist's rendering of NASA's Voyager 1 spacecraft entering interstellar space, or the space between stars. Image Credit: NASA/JPL-Caltech

Nearest things that we can reach

Mars, the red planet, is almost in the bag as far as we are concerned, with plans of reaching and colonizing it by 2050, even by 2030, with the likes of SpaceX in the mix. The trip to Mars when it is closest to earth in its orbit will take roughly around 6-8 months with the technology that we have today. But reaching out from Mars is bound to be tricky. We have sent unmanned missions through the perilous Asteroid belt between Mars and Jupiter, and we have done so successfully. But it is not simply the dangers of the mission that will make it tough, but it’s the duration. These missions will be challenging on the mind and the body, for human bodies are not programmed to spend such vast spans in the outer stretches of space.

If we will have found life on Titan or Europa by the time we had colonized Mars, our sights will shift to these giant moons. But these places might not harbor the perfect habitable zones for humans. So, even if we find life, we are not likely to stick around.

An image of Titan beside Saturn, Veiled Worlds/ Source: NASA/JPL-Caltech/Space Science Institute

The farthest planet in our solar neighborhood is Neptune, which is 4.3 billion kilometers[4] away from the earth in its closest approach, which is around 28 times farther away the sun is from the earth. The time it will take to get there will depend on a lot of factors. Gravitational assists or planetary flybys will definitely come into play on these missions as such maneuvers save a lot of time, fuel, and can also provide energy to the spacecrafts.

But this distance is tiny compared to the distance to our second neighboring star. Proxima Centauri, part of the Alpha Centauri star system, lies 4.2 light-years away, which means that when you spot Proxima Centauri with a telescope ( because it can’t be seen with the unaided eye), you are seeing the light that left the star 4.2 years ago! If Voyager 1, which is now in interstellar space, were to be traveling to Proxima Centauri at its speed of 17.3 km/s, it will take about 73,000 years for it to get there! When the spacecraft Juno did a planetary flyby of Jupiter, it reached a speed of 265,000 km/hr[5], the fastest we have ever achieved in space. But even if we could attain such constant speed on the trip to Proxima Centauri, it will still take about 17,300 years to get there!

Reaching Proxima Centauri will not just be a golden age in our future but will also be promising because reaching new stars also means entering into new solar systems and finding new planets. The Goldilocks zones are regions around a star where life potentially exists, and planetary scientists are studying these exoplanets, which could host life. Proxima b[6] is one such planet, which revolves around the red dwarf, Proxima Centauri.

An artist's impression of Proxima b, Credits: ESO/M. Kornmesser / NASA

But the major factor that comes into play here is time, and undoubtedly, the scope of humanity in exploring deeper regions of the space is hardwired to it. To make time much less of a concern, we will have to outsmart it with technology. And technology always resides in places where there are ample amount of resources to be used up.

Civilization types

The answer lies closely connected to the civilization types, as mentioned by Nikolai Kardashev. The Kardashev scale measures civilizations primarily based on their ability to harness energy to their needs.

A type 1 civilization is one that uses all available energy from the star it orbits. It involves controlling all things that happen on the planet. A type 1 civilization can manipulate the weather and manufacture rain on a sunny day and could even prevent natural disasters. The underlying principle here is utilizing all things ‘planetary’.

A type 2 civilization can harness as well as manipulate the entire energy of a star to their liking. A hypothetical structure called a Dyson sphere is a mega-structure that envelops a star and absorbs as much energy the civilization needs and then transfers it to the planet or planets to be consumed. The type 2 civilization has complete freedom to operate in their solar system, making them a stellar civilization.

A type 3 civilization is far superior, and their powers are scarier in comparison. They are galactic and can, therefore, do as they wish with the entire energy output of the galaxy. Which means they have a vast number of stars, asteroids, comets, planets, even black holes at their disposal. They could travel between stars, move cosmic bodies in their way, obliterate asteroids, and do much much more.

An artistic rendering of a Dyson sphere, a hypothetical structure that surrounds a star to absorb energy from it directly — An artistic rendering of a Dyson sphere

So, what about our civilization? Humans have come a long way from living in the plains of Africa to sending people to the moon. We have pioneered many things along this long journey, some remarkable as understanding the laws of science, while others questionable as waging wars. But nevertheless, one of the most profound things that separate us from other forms of life on the planet is our intellect. So, clearly, we have to be a type 1 civilization, right? Wrong. We haven’t quite reached there yet. According to Carl Sagan, we are not necessarily a type 0 civilization, but an intermediary civilization that’s moving towards type 1. Based on the energy usage in 1973, he coined our civilization as a 0.7 civilization, and we would likely be pushing 0.8 by now.

Michio Kaku states that our progress to type 1 civilization is gaining momentum, and he envisions our civilization to reach there in around 100 years. While this may be exemplary, the resources on our planet might be spent in doing so, and we will have to look up at the sky for further answers. But the transition from type 1 to type 2 won’t be easy. It is estimated to take thousands of years to get to that point, but that transition is nothing compared to the transition from type 2 to type 3. It is said to take hundreds of thousands to a million years. But these are surely rough estimates and are likely to change according to our advancement in science and technology.

While transitioning from one civilization to another sounds like a matter of time and technology, it seems to come with a catch. And judging by the evolution of life from single cellular to multi-cellular to conscious organisms, it is possible that exploration is part of life itself. So, when the resources on a planet are about to empty, the species on the planet are likely to look elsewhere for a new home or resources. There are roughly about septillion planets in the observable universe, and in a manner of speaking, civilizations, stellar or galactic should exist somewhere out there in the depths of the universe, in agreement with the Kardashev scale. But the fact that we haven’t found evidence of any such galaxy-harnessing civilizations is deeply worrying. Maybe there is something out there that prevents such transitions from happening, some form of barrier that no civilization can cross.

Life is a mystery to us all. We are not sure if it started from dead things on earth, or if it booked a ticket on an asteroid that struck earth 3.5 billion years ago. But life survived, whether it was through a fortunate chance, or through multiple tries, it found a way. So, perhaps life finding a way was the great filter, and if that were true, humans have already crossed the filter.

But, of course, this is wishful thinking, to say the least, for there could be impending filters that we are yet to cross, or to sound morbid, fail to. Nuclear wars, some form of natural calamity, a disease gone out of control, a meteor intervention, for all we know, it could be any of these or something that we can’t even possibly imagine. Or maybe our doom will be decided when we finally find aliens. But on the contrary, if we are the fortunate filtrates, there is a long and hopeful road ahead of us.

The futuristic travel

The Saturn V will always be remembered as the rocket that put people on the moon. But as we look back upon it, we realize that rockets and spacecrafts have become much more efficient and faster than what it used to be. With technology expanding the bubble that we live in, we now have private companies investing in state-of-the-art space vehicles for the imminent future.

Whether we truly believe it or not, we are living in a great age of space exploration. The main contributing factor to it is the improvement of technology in space programs. Rockets no longer need to be disposed off, they are much more efficient than before, they can carry more payload, and most importantly, SpaceX claims that their new rocket, called the ‘starship’[7], which can carry more payload than Saturn V, would also have the lowest launch costs relative to others because of its re-usability. The space launch system by NASA will also take center stage in our revisit to the moon and is also likely to be strongly involved in the Mars missions as well.

While these are incredible feats of humanity, which shows our passion and hunger towards exploration, innately, we know that spacecrafts will have to get much much better in the future to have any hopes of reaching another solar system. During the final flyby of the Parker Solar Probe[8] around the sun, it will reach an approximate speed of around 690,000 km/hr under the Sun’s immense gravitational pull, making it the fastest speed ever attained by a space probe. It will be more than double the current speed record held by Juno. But even such high-speed transportation simply will not be enough if we were to travel to our nearest exoplanet. We need something much faster. So, is there any ground-breaking technology that exists which could make this possible?

One of the main problems with the typical spacecrafts is the weight-speed correlation. Obviously, the weight of the fuel jeopardizes the speed of a spacecraft, but contrastingly, if the spacecraft needs to reach a farther celestial body like Proxima Centauri, it requires a lot of fuel on-board. Solar sails get around this problem really well. They are made of lightweight materials which are just 0.00045 cm thick and works under the influence of the sun’s push. The speed is dependent on the area of the sail, as more area would mean more photons pushing the sail. And the fuel problem is non-existent as it's powered solely by solar energy. The planetary society’s[9] new solar sail, called the LightSail 2, has 32-square-meter sails, which accelerate it at 0.0.58 mm/s2, but in a month of sunlight exposure, it’s speed will increase by 549 km/hr.

A new project[10] announced in 2016 takes solar sails to another level. It aims at laser propelled solar sails, which can be accelerated to 20 percent the speed of light! This could actually be done by pointing laser beams from the comfort of our planet. Scientists predict that a journey to Alpha Centauri by such a means will only take a few decades! A trip to Mars, a mere 3 days!

While solar sails are efficient and could well be the best means to understand the nearby stars and planets, it doesn’t really make human transportation possible. Technically, it could, but the underlying principle of a solar sail is strictly against that notion. It will become a whole lot slower on adding more weight and could drastically elevate the duration of expeditions, and ‘time’ gets thrown into the mix yet again.

This is the current horizon of technology that we can see, but what if we were to think from within the realm of science fiction? What if we could invent technology that makes time, less of a concerning factor? What if we could manipulate the very fabric of space-time itself?

Warp drives and wormholes are often discussed as cool science fiction items in movies. But they have math in them which could be of major contention in the long-view of technology. Both of these concepts work well within the limits of general relativity. A warp drive[11] distorts the space-time to form a bubble around the spacecraft and moves that space itself faster than the speed of light, thereby moving the spacecraft from point A to point B without violating the laws of physics.

A Wormhole[12] works under a similar principle, which involves the bending of spacetime. It could well be defined as a bridge that offers a shortcut from point A to point B almost instantaneously. While neither of these concepts violates the speed barrier of light, scientists believe that the existence of such things are permitted only under cases where incredible amounts of negative matter are there at disposal. Negative matter[13] or exotic matter is a special kind of matter which we know little to none about, and are known as some of the weirdest things that exist in the universe. They are repelled by things that have mass, and because of this, though exotic matter can technically make our science fiction come to life, it can never be found in excess amounts. But perhaps when our knowledge of the universe grows, we might yet find ways to make wormholes and warp drives come to reality.

The expansion of space

In 1929, Edwin Hubble[14] discovered something strange while looking at the sky through his telescope. He observed that the light from a few far galaxies appeared red. Hubble described this as a phenomenon caused when the wavelength of light is stretched. This could only happen if the light-source was moving away from the observer. This led to the understanding of an expanding universe.

But this expansion, which was thought to slow down, did not. Theoretically, all the matter in the universe was supposed to be pulled together by gravity, hence slowing down the expansion. But the Hubble Space Telescope[15] in 1998, revealed images of distant supernovae, which told another story. Scientists realized that the expansion of the universe was much slower than today, which meant that the expansion has been accelerating.

This cosmic acceleration is thought to be caused by something called dark energy. Theorists have not yet unfolded the mystery, but are sure of its composition in the universe, which is about 68 %[16], in fact, it’s the most common thing out there in space according to this theory! One way to answer the question of dark energy is by imagining it as a property of ‘space’ itself[17]. Einstein believed in the amazing properties of empty space! But anyway, since dark energy is entwined with space, it would not dissipate as space expands but would merely increase, thereby expediting the expansion.

But how does this affect the narrative of human limits? Well, we now know that the universe is expanding, and it's expanding fast. And from high school physics, we know that nothing can travel faster than the speed of light. But with the expansion of the universe, there happens to be a catch, a sort of beautiful loophole. Relativity only prevents matter, ‘things that occupy space’, from reaching or crossing the speed barrier, it does not limit ‘space’ itself from doing so. Hence, there will come a time in the future, when the expansion of the universe, especially the current horizon, will exceed the speed of light, and our distant cosmic bodies will forever disappear from our sight. Hence, with the governing laws that we have now, we will never reach those far-out places in the deep darkness of space, and in trying, we will have finally understood our limits! But of course, this would seem a really dull thing to read if someone were to reconfigure special relativity, or if we figured out a way to synthesize exotic matter in vast amounts.

So, what then?

Our universe is an endless ocean of energy. Sometimes it can be harsh and terrifying, sometimes strange and mysterious. But at all times, it is enchantingly beautiful. And in a way, we are also all these things. Sure, we are always likely to be playing catch-up with the expanding universe, but that doesn’t have to be discouraging. We are still at the dawn of possibilities, staring at the ever-changing horizon in front of us. There are countless discoveries to be made, machines to invented, and, most importantly, science to be understood. Our limits are bound within our capabilities. Much like our universe, we are yet to know our limits of understanding.

Hubble legacy field crop, Credit: NASA, ESA, G. Illingworth and D. Magee (University of California, Santa Cruz), K. Whitaker (University of Connecticut), R. Bouwens (Leiden University), P. Oesch (University of Geneva), and the Hubble Legacy Field team

This image was published on the Hubble website[18] in May of 2019. It is a combination of thousands of snapshots, worth 16 years of observations, and is one of the widest views of the universe ever made. Called the Hubble Legacy Field, the full resolution image accounts for a download size of 927 megabytes!

In it lies 200,000 galaxies[19], some of which are as old as 13.3 billion years. Perhaps some of them will become invisible to us in the future, and perhaps we won’t even reach any of them. But the image represents just a tiny speck of our vast night sky! If we shift our telescopes to another speck, we find more and more of these celestial bodies, near and afar. Even if we are bound by laws that we can’t break, there are things out there we can still reach, and maybe that is not such a discouraging thought at all.