Space Travels to Nearby Exoplanets: Any Possibility (Part 5)

Instead of travelling far too far, what about some nearby exoplanets – planets that exist outside our Solar System? How many of them have been discovered?  Could life exist on newly discovered exoplanets, and can we go there?

There are thousands of exoplanets discovered so far, with many in the habitable zone (where conditions might support liquid water). Some promising candidates include:

Proxima Centauri b (4.24 light-years away) – A rocky planet in the habitable zone of Proxima Centauri, though it is bombarded with strong stellar radiation.

The TRAPPIST-1 System (~39 light-years away) – Seven Earth-sized planets, at least three of which are in the habitable zone.

Kepler-442b (~1,120 light-years away) – A super-Earth that receives enough sunlight to potentially support life.

Although we haven’t confirmed life on any exoplanet yet, scientists use methods like spectroscopy to analyse their atmospheres for biosignatures such as oxygen, methane, and water vapor. Future telescopes, like the James Webb Space Telescope (JWST), are designed to study exoplanets in greater detail.

 

Can We Travel to the Nearest Exoplanets?

Theoretically, reaching the nearest exoplanet (e.g., Proxima Centauri b) is possible, but with current technology, it would take thousands of years. Here are some of the reasons.

Current limitations with conventional rockets are the fastest spacecraft ever launched, Voyager 1, travels at ~17 km/s. At that speed, it would take over 73,000 years to reach Proxima Centauri. The we also have fuel constraints of carrying enough fuel to reach high speeds is a major problem. Consider survival in space even to the nearest exoplanets since  human lifespans and exposure to radiation pose significant risks for long journeys. Some possible future solutions include a breakthrough Starshot, namely a proposed mission to send tiny, laser-powered probes to Alpha Centauri at 20% the speed of light, reaching it in 20 years. Technologies like nuclear pulse propulsion or fusion propulsion rockets could cut travel time to a few decades. We have earlier talked about warp drive concepts that are theoretical physics that suggests space-time manipulation (e.g., Alcubierre drive) that could enable faster-than-light travel, but it remains speculative.

We have also suggested generation ships or cryosleep if journeys take centuries, humans might need to live on self-sustaining "ark ships" or enter hibernation.

While even traveling to the nearest exoplanets is currently beyond our technological reach, future advances in propulsion, energy storage, and space travel may eventually allow us to explore them. The search for life continues, and if we detect signs of extraterrestrial life, it may push humanity to develop new ways to reach the stars.

Technologies That Could Enable Travel to Exoplanets

Travelling to exoplanets is one of the greatest challenges humanity faces. Our current propulsion methods are far too slow, but there are several theoretical and experimental technologies I have written earlier that could make interstellar travel a reality. Just to recall, below are the most promising approaches:

 

Near-Term Technologies (Could Be Developed in the Next 100 Years)

Breakthrough Starshot (Laser-Powered Light Sail) This concept lies on tiny spacecraft (gram-sized "StarChips") with light sails propelled by powerful Earth-based lasers. Speeds up to 20% the speed of light (~60,000 km/s) is possible. The time to Proxima Centauri (4.24 light-years) is 20-30 years. But the challenges are that it requires enormous laser arrays on Earth, risk of damage from interstellar dust, and difficulty in slowing down at the destination. However, the physics is well understood, and the technology is already being researched.

Alternatively, we can also consider using nuclear fusion rockets (direct propulsion). The concept here uses controlled nuclear fusion reactions (like the Sun) to generate immense thrust. The speed we can expect is 10% the speed of light (~30,000 km/s). The time to Proxima Centauri is 40 years. The challenges are it requires advanced fusion reactors that don't yet exist, plus enormous energy storage. If we master nuclear fusion for energy, it could also power rockets. Projects like NASA's Direct Fusion Drive (DFD) and Project Daedalus study this approach.

 

I have also earlier suggested using antimatter propulsion. The concept is,  matter and antimatter annihilate to produce pure energy (E = mc²), providing extreme thrust. The speed we can expect is up to 50% the speed of light (~150,000 km/s). The time to Proxima Centauri is  8-10 years. The challenges are, antimatter is extremely expensive to produce and store safely. It is probably the most energy-efficient propulsion possible, but we lack the technology to produce antimatter in large quantities.

Far-future technologies (100+ years away, but theoretically possible. This are

Alcubierre warp drive that goes faster-than-light travel). The concept is, it compresses space ahead of a spacecraft while expanding space behind it, allowing "faster-than-light" travel without breaking relativity. The speed theoretically is many times the speed of light.

The time to Proxima Centauri is instantaneous (in principle). But the challenges are that this requires exotic negative energy (which may not exist), and controlling space-time warping is beyond our current physics. It is promising that if negative energy fields or advanced quantum field manipulation become possible, warp drives could revolutionize travel.

I have already written about using Einstein- Rosen bridge or wormholes (space shortcuts) where the concept is,  hypothetical tunnels through space-time that could connect distant locations instantly. The speed is instantaneous, and the time to Proxima Centauri is just a few seconds (if stable wormholes exist). Unfortunately, currently we do not know if wormholes exist naturally or how to create them, and keeping them stable requires exotic matter. If wormholes exist or can be artificially created, they could enable true interstellar travel.

Regardless of propulsion, long-duration space travel requires additional technologies, including generation ships that are large self-sustaining space colonies where multiple generations live and die before reaching an exoplanet. Our challenges require perfect ecosystem balance, long-term social stability, and massive engineering efforts. But it allows slow travel over thousands of years while keeping humans alive.

In that case, we need to revert to cryogenic sleep (biostasis) where the concept is  deep freezing or slowing down human metabolism for long-duration space travel. Fortunately, our challenge is, we haven’t perfected human hibernation, and long-term effects are unknown. If we solve human biostasis, we could "sleep" through a long journey.

Can we reach exoplanets then? Yes, but not with current technology. The best near-term option is laser sails (breakthrough Starshot), while nuclear fusion or antimatter propulsion could make human travel practical. In the far future, warp drives or wormholes could revolutionize space travel - ah, provided they are physically possible.

I have already written about  wormholes as a hypothetical tunnel connecting two points in space-time. It was first proposed as a solution to Einstein's General Relativity equations by Albert Einstein and Nathan Rosen in 1935 (hence called an Einstein-Rosen Bridge). The key properties of Wormholes are, they connect distant locations in space, potentially allowing instant travel between them.

They could also connect different times, making time travel a theoretical possibility. They are predicted by Einstein’s equations, but we have never observed one.

I have earlier explained if we imagine space-time as a piece of paper. If you fold the paper and punch a hole through it, a wormhole will act like a tunnel connecting two points on the paper, bypassing the usual long route. A wormhole could be used as a time machine to travel backward in time. The challenges of using wormholes for Time Travel while  sounds exciting, there are serious obstacles to making a wormhole a real time machine, first, do wormholes even exist? My answer is, no natural wormhole has ever been observed. Theoretically, they could form in extreme space-time conditions (like inside black holes), but we don’t know if nature allows them. Keeping a wormhole open requires exotic matter. Einstein’s equations suggest that wormholes might collapse instantly unless held open by negative energy or exotic matter (which violates normal energy conditions). Some quantum physics theories (like the Casimir Effect) hint that negative energy is possible, but we don’t know how to generate enough of it.

 The Paradox Problem (Grandfather Paradox).

If we use a wormhole to travel back in time and change the past (e.g., stopping our grandparents from meeting), we create a causality paradox. Solutions like the Novikov self-consistency principle suggest that events will always adjust to prevent contradictions. Then we also have quantum instability. Some calculations suggest that even if a wormhole were created, quantum effects might make it collapse the moment a time loop is formed.

 What about a time machine without wormholes? If wormholes aren’t possible, could a time machine still be built? Some alternative ideas exist such as - Tipler Cylinder (Rotating Infinite Cylinder. Here a huge, infinitely long, super-dense rotating cylinder could warp space-time enough to allow time loops. But our problem is, it requires infinite length and impossible material density.

Another concept is Kerr Black Holes (Rotating Black Holes) that is a fast-spinning black hole that might create a region where time loops exist. But our problems are,  falling into a black hole would likely destroy anything before time travel is achieved.

What about Cosmic Strings? These are hypothetical "strings" of ultra-dense material left over from the early universe that might distort space-time enough to allow time travel. But our problems are, no evidence that cosmic strings exist.

So, back to exoplanets. Could we ever use a wormhole to visit an exoplanet or the past?

Ah, my answer is, if stable wormholes exist, interstellar travel could be nearly instantaneous.

If time dilation is applied to one wormhole mouth, time travel to the past becomes theoretically possible.

However, currently we lack the physics and technology to manipulate space-time this way, because wormholes and time machines remain speculative, but they are consistent with Einstein’s equations. Future breakthroughs in quantum gravity (e.g., theories like Loop Quantum Gravity or String Theory) may one day reveal if they are truly possible.

If time travel is possible, where are the time travellers? Perhaps time travel can only go as far back as the invention of the first-time machine, meaning no travellers from the future could arrive until such a machine exists.

I hope my answers are not mind-blogging ideas and difficult to understand  for scientists in the medical field, or for medical doctors – perhaps, reachable for theoretical physicists