1. Can we travel to the stars?
A surprisingly common question deserving of an answer. Often lying behind this question is whether humans can ever venture out to the stars considering that it takes light at least 4.3 years to reach the nearest star after our Sun, and billions of years to reach distant galaxies. As some people have said, if we could travel at the speed of light, then surely all the galaxies outside the Milky Way would still be permanently out of our reach since many are 18 billion light years away? So isn't travelling to the stars an impossibility?
If we could hypothetically travel at the speed of light, the answer to your question is, "Yes, you can go anywhere in the Universe". However, this can only happen if you participate in the flight, not for those who sit on a planet (they are the ones who must wait years, centuries or billions of years for your return). Even if it is hypothetically possible to travel anywhere in the universe, in reality travelling at the speed of light is never a good thing. Apart from the fact that no mass can reach let alone exceed the speed of light, if we could somehow reach the speed of light in some kind of exotic technology, everything in the Universe will not only be within our reach and we will get there instantaneously, we will also not give ourselves time to see where we are going. Colliding into a massive object, such as a star, planet or rogue rock in space, becomes a distinct possibility. Ideally you would want to throttle the speed just a tad. Just enough to give yourself ample time to see what is in front of you and make the necessary course correction. But let's face it. Do you have to move at the speed of light just to travel from one end of the visible universe to the opposite end?
If you accelerate at 1g and decelerate at 1g to arrive at a destination (useful for large spacecraft not built for speed), simple calculations show that it would take:
- a little less than 0.95 years to travel 1 light year away
- a little less than 1.5 years to travel 4.3 light years away
- a little less than 27 years to travel to a point 1 million light years away
- It would take 40 years to go 1 billion light years.
- 53.6 years to go 1 trillion light years.
- 62.5 years to go 1000 trillion light years.
As you can see, we do not have to travel at the speed of light to reach any part of the universe in a human lifetime. Indeed, interstellar travel is not only feasible, but it would permit any biological entity (or entities) to participate in those long flights. Just build a big enough spacecraft, make sure it has all the most useful mod cons you would need to while away the time, there are ample places to grow enough food, and a reliable engine to provide the continuous accelerating and decelerating forces, and you will be fine. You might be required to do a lot of recycling of plant-based foods and water (the latter can also be extracted from space clouds and some planetary atmospheres or oceans) and carefully grow the food throughout the journey. That means you may have to be a vegetarian throughout much of the journey. Oh well. There are tougher things in life than being a vegetarian. NASA and the Russian space agency have already shown the feasibility of surviving in space for long periods simply by growing enough plants in space to provide all the nutrients.
The results really do speak for themselves: anyone can travel a great distance within a human lifetime. What is important to remember here is to participate in the flight. Apart from that, you need a reliable technology to provide continuous acceleration/deceleration lasting many years assuming the aim is to travel to, say, the edge of the Milky Way or beyond.
Or far less time if you are merely travelling to a star closest to the Earth after our Sun!
2. There is no way we can travel to the stars. It requires so much energy that it would be impractical to try even for a modestly advanced alien civilisation. So isn't interstellar travel impossible?
This is another common question.
In answering this question, the answer is "Yes, you need energy. To travel to the stars, a fair amount of energy is required. But not a much as you think."
For example, if you build a very lightweight, but tough spacecraft, you will need much less energy to accelerate it to high speeds compared to, say, a much more massive spacecraft of the type we build today (from NASA, the European Space agency etc.). Our society tends to favour heavy objects with very thick hulls. Such a great thickness is necessary to protect ourselves from space debris. Little do we know that the use of a strong magnetic field externally and a means to electrify things (e.g., a charged surface) as we approach something can help to deflect space debris and charged particles, and probably more effectively too. In which case, what you have left is an external hull whose thickness can be no greater than, say, a sheet of newspaper. So why would you need a thicker hull? Shape the spacecraft in a symmetrical way and use a metal or alloy for the hull and you can protect the people from the external electromagnetic hazards.
It should already be apparent by now that the first important key to making interstellar travel possible is to reduce the mass of the spacecraft. In that way, the amount of energy needed to move a spacecraft is reduced. Any spacecraft that attempts to travel to the stars must always be as lightweight as you can get it.
Now, speaking of a technology to provide continuous acceleration and deceleration over many years, physicists know that we cannot be expected to carry enough energy by way of a solid mass called "fuel" to achieve this aim, especially if you want biological entities to travel to the stars. Apart from the finite nature of the fuel, you cannot carry too much of it or the mass of the spacecraft will increase dramatically. Even with nuclear fuel to reduce the amount of solid matter by way of fuel, all it will do is significantly bog down the mass of the spacecraft to such an extent that it would take a long time to reach even the nearest star after our Sun (i.e., 45 years to reach Alpha Centauri at 4.3 light years away, or 60 years to reach Barnard's Star at 6.0 light years away based on a design provided by Project Daedalus). What you need is to have energy available throughout the journey and to tap onto it when you need it, or else you must somehow recycle the energy emitted for propulsion. Or why not do both?
Well, did you know that there is energy in space that we can utilise? Space is not exactly a perfect vacuum. It contains energy, mostly by way of electromagnetic energy, or radiation (including planetary, solar and galactic magnetic fields). All you have to do to make this energy practical for propulsion purposes by concentrating it by some means. Then you can tap onto this concentrated energy to make it do our bidding. That is the key to making interstellar travel a reality for those who want to participate in the flight.
Can we use technology to concentrate this energy and use it for some practical purpose, such as propelling on object in space?
An excellent question. According to UFO reports, the ability of some objects to render themselves invisible, and often in a periodic manner, is revealing evidence of a technological means of concentrating electromagnetic energy around the objects which, in turn, is helping to distort the path of light coming to our eyes from near and directly at the object. Furthermore, Einstein's Unified Field Theory claims that the electromagnetic field generates a gravitational field of its own. It is this gravitational field that helps to bend light around an object and prevents light from emerging from the object itself. In other words, an object can be rendered invisible to the naked eye. If this is true, it is clear UFOs are already able to concentrate electromagnetic energy. Furthermore, the invisibility effect is also revealing a way to "recycle" electromagnetic energy.
However, before we can explain at least a couple of techniques on how we can concentrate the energy in space, imagine that we could concentrate this energy. What then? Not a problem. Once you have this energy in place, you can use, say, a metal antenna to cut through the energy as you move through space. Then you will generate a voltage (or charge) at opposite ends of the antenna. But can we use this voltage to propel an object? Yes you can. How about you oscillate the voltage and use it to generate and emit radiation on the external metal hull? Why? Well, if this energy is used to emit radiation predominantly in one direction at a higher energy density, the object will accelerate. But not just any old acceleration. According to the solution of the Abraham-Lorentz formula for a charged object emitting radiation, the acceleration is said to be "exponential". The kind of acceleration you will not find in a car or man-made aircraft.
It is here where physicists have found a way to travel to the stars using the laws of electromagnetism, and for people to participate in those flights. The only question is, Can we implement the "exponential" solution in the real world? At last, we have come to the $64,000 question for science.
3. How do we concentrate the energy in space?
Good news! Scientists have discovered at least one way to concentrate the energy in space just make the spacecraft move at relativistic speeds. Why? It is because at such high speeds, the mass of the spacecraft increases as detected by an outside observer. This extra mass is not coming from the materials making up the spacecraft. Rather, it is the mass in the energy of space getting concentrated around the spacecraft. It is a kind of bunching effect as the spacecraft moves through space (in mathematical terms, it is a bending or folding of space-time not unlike how a rubber band is stretched and bent). It is this extra mass that prevents the spacecraft from ever reaching the speed of light. You can imagine this situation as like the plough that tries to push snow on the ground. Eventually enough snow will stop the plough from travelling any faster. The same is true for a spacecraft pushing against (or pulling gravitationally) the energy of space. Nevertheless, this increase in the apparent mass of a moving spacecraft is evidence of energy concentrating on the object itself. Of course, the only tricky part is how to get the spacecraft up to speed to benefit from this extra "free" energy?
There is another way. It might come as a surprise for readers to learn that applying an oscillating charge on a metal surface does the same trick. Instead of relying on an accelerating spacecraft moving linearly through space at high enough speeds to help concentrate the energy of space, you can accelerate electrons instead. Even while the spacecraft is at a rest position in space or sitting on the ground, the accelerating motion of the electrons does all the work of concentrating the energy of space around the spacecraft. Electrons move very fast on a metal surface and can move to relativistic speeds. So why not make use of the electrons to do this energy concentrating work for you?
When we refer back to UFO reports, it is interesting to find plenty of examples of nocturnal UFOs and some daytime UFOs having a large glowing region, and that this region can be blinking on-and-off. The glows are highly reminiscent of the way a metal heats up as you apply an oscillating voltage commonly found in an incandescent light bulb. Well, any build-up of electric charge on a metal surface is always concentrating energy. The "blinking on-and-off" is just evidence of the oscillating nature of this charge. As the charge reduces, the temperature of the glowing metal can drop and the glowing effect is diminished. Increase the charge, and the flow of electrons moving on the metal surface can cause the metal to heat up. If the electrons move fast enough, it isn't just the energy that we emit from the charge that concentrates energy in space. Space itself also responds "in kind" by being "attracted to" and increasing its density as it bunches up around the oscillating charged surface.
Basically you have a double whammy effect going on here with the energy you generate and with the energy you bring to the object through the oscillating charge.
4. How can a person moving in a spacecraft reach the destination quicker even though it takes light years, decades, centuries or even billions of years to reach the same destination?
Have you kept your body nice and thin? Are you a person of short stature? Great. So now you can get up to speed, and not just intellectually speaking too. However, as you have quite rightly pointed out, it can be hard to understand how a person participating in the flight can reach his/her destination quickly compared to those staying behind on a planet. As people have quite rightly suggested, wouldn't this require travelling faster than light and physicists know no mass can exceed the speed of light. How is this possible?
Well, the first thing you will notice as you get to relativistic speeds is how the space around you gets distorted as the energy gets more concentrated. The position of stars look odd and the star directly ahead of you (and the one you are reaching for) looks surprisingly closer than you think. The reason this is happening is because the concentrated energy around the front end of the spacecraft (and to a lesser extent behind the spacecraft) acts as a magnifying glass in bringing the light from these objects lying along the direction of motion (i.e., directly behind and in front of you) closer to your spacecraft. If you measure the distance to your destination using this light emitted by a star in front of you, for instance, it would appear that the star has a shorter distance. This is the old famous so-called length contraction along the direction of motion of Einstein's Special Theory of Relativity. However, in truth, any kind of length contraction as seen by an outside observer or based on your observations as an optical illusion. Stars in front or behind do not magically jolt from their positions in response to the movement of the spacecraft and come closer. Yes, you are getting to you destination much quicker (which we have yet to explain how in a moment) as if the distance to the destination has shortened according to your observations and quick calculations (while relying on the apparent speed of your spacecraft as measured by the outside observer) would suggest this. However, in reality, what is really happening is that the distances to the stars remain always the same. The reason why you are getting to your destination quicker inside the moving spacecraft is because the spacecraft is moving faster than the speed of light.
But, hold on! Isn't it true that no solid matter can travel faster than the speed of light? Yes, you are correct. There is one more thing we have to remember.
All this concentrated energy is coming from somewhere. It is not created out of nothing. It is really a displacement of the energy from another part of space near the spacecraft that has responded to the motion of the spacecraft and has become "attracted" to the moving object (or simply bunched up). This means that as the density of this concentrated energy builds up in the vicinity of the spacecraft, the density of the energy in the region of space where the energy got displaced is at a lower level. It is lower than the normal density of space. It means that any kind of solid matter, including light, can actually travel faster in a lower energy density environment.
You can exceed the speed of light while moving through normal energy density of space because you have affected the balance in the energy density of space due to your tremendous speed. A higher energy density of space around the spacecraft means there has to be a lower energy density elsewhere. However, the universe does not permit this lower than expected energy density to be maintained. So the way to compensate and balance this situation is by electromagnetically pushing (or gravitationally pulling) on the concentrated energy surrounding the spacecraft and the spacecraft itself much like a surfboard riding a wave towards the shore to a higher speed as the universe attempts to restore balance and have this lower energy density region "filled" and returned to the normal density of space. The universe does this balancing effect so quickly that it pulls (or pushes) the spacecraft to a higher speed and with great force.
In fact, in the limiting case of zero energy density, any energy outside of this region will enter this perfect vacuum region with such force that it will be effectively infinite in strength. Nothing inside the perfect vacuum can counteract the force of the universe in filling this empty region. In other words, the universe does not allow for a region of perfect vacuum with no energy (like wormholes) to exist. It is impossible to create a perfect vacuum in reality even if the mathematics claim it is theoretically possible. The real universe cannot allow it to exist even for a fleeting moment. However, there is nothing in the laws of physics to stop you from lowering the energy density of space to help increase the speed of your spacecraft in order to reach a destination more quickly. That is a perfectly fine thing to do.
Think of the energy of space as like a rubber band. You stretch the rubber band and, naturally enough, the density of those atoms making up the rubber band is lowered. However, the chemical bonds holding atoms together doesn't like this stretching situation. The bonds will want to pull back and bring the atoms together to an equilibrium level and hence a normal density. The same thing happens for the rest of space. The energy of space is like the springs or the chemical bonds of the rubber band. It will counteract this stretching of space-time. It will pull gravitationally (or push electromagnetically by the radiation) the higher energy density formed by the moving spacecraft to help fill the lower energy density region formed elsewhere in an attempt to restore the balance. But since the spacecraft continues to move at high speeds, there is a continuous concentrating of energy from the rest of space to the spacecraft as well as pulling (or pushing) to rebalance the energy density of space by the rest of the universe. And since the universe has more mass, it will pull (or push) the spacecraft more strongly to itself.
As you maintain this continuous tussle in the differences in energy density with the spacecraft pulling on the energy to itself and the rest of space balancing the situation causing the spacecraft to travel faster to fill the lower energy density region, you maintain exceptional high speeds. The kind of speed that will be greater than light travelling through the standard energy density of space as measured by an outside observer. In other words, you will get to your destination much quicker.
That is why it is important to participate in the flights to the stars if you want to benefit from short journey times, but not for those who stay behind on a planet.