Some people speculate that one day we will be able to travel to Mars and colonise it. Obviously, it will need a lot of work doing on it to be habitable. Yet, such plans for terra forming the surface of Mars are already on the drawing board. The idea would be to warm the planet up by introducing large quantities of greenhouse gases. The poles would melt producing water. In addition, frozen carbon dioxide at the poles would sublime into the atmosphere. This would add to the greenhouse effect. Liquid water trapped just under the surface would start to flow making the lowlands into seas. However, the gravitational field of Mars is something that we have no way of increasing. This means that the atmosphere would be thin. To support life, as we know it would require giant domes under which we would live. This of course is not a very long-term solution for billions of years in the future when the sun enters its red giant stage. Mars would then also be too close to the sun and although the sun’s surface temperature would have approximately halved from six thousand degrees Celsius to around three thousand degrees, Mars would be so close that its surface would be baked and we would be back to square one. Nevertheless, it is a good stepping-stone to encourage us to move on, having already reached the moon. In hundreds of years, flights to Mars may well be routine. We will have seen many more advancements in space flight and in an attempt to keep journey time to a minimum, the speed of the craft would increase. The surface of Mars would be terra formed and liquid water released. There may well be bases there where astronauts could live for months at a time, just as they have done on the space stations in orbit around the Earth. It is doubtful if people would want to live there permanently, reproducing and raising families. There would be a weaker gravitational field and a reduction in sunlight. This would cause adaptation to take place over a long period in the population. In other words, people’s appearance would change to adapt to the new environment. This would result in permanent genetic changes. They may well grow taller. They may well have thinner and weaker muscles and bones. They would need a regular return trip to Earth to maintain the status quo. If generations had passed and no return trips to Earth made, then it may be impossible to ever return without damage.
As an alternative, some scientists speculate that when the sun becomes much hotter as a prelude to the red giant stage that Titan a moon of Saturn, will burst into life. At present, it is like a world in deep freeze. Since it is a satellite of Saturn, we should really say moon in deep freeze. Due to space probes we have sent there, we know that it contains many of the natural elements such as nitrogen, as we have in the atmosphere of Earth. As the sun swells into its red giant stage, the liquid nitrogen would turn into gas and produce an atmosphere. Similar favourable conditions may occur on other large moons of Saturn or those of Jupiter. Whether they become habitable is open to question, but the fact remains, that this would only be a temporary solution to the problem. Once a star has entered its red giant stage, it is on its way out. Over millions of years, it will shed its outer layers into outer space as it moves into its final stage of evolution. Then it becomes a white dwarf, a white-hot cinder about the same size as the Earth is at present. Even the outer planets would have the outer layers of the sun blasting past them as the sun approached this final stage. This would be intolerable. What we really need is a more stable and permanent solution to the problem. That is, an inhabitable planet about the same size as the Earth around a much younger star.
Searching for planets around other stars is a brand new science. We have no chance of seeing a planet directly around another star, because the light from the star totally swamps out the reflected light of a planet. If a planet has a big enough mass then it can cause its host star to wobble slightly. This is a bit like looking at two Olympic hammer throwers, one with a hammer and one without. We look from such a distance so that we cannot see the hammer. We would be able to tell when they went through their routine which one had the hammer by the athlete's side to side motion. In the case of a distant star, what we detect is the star moving ever so slightly towards us and then away from us without any visible companion. It is possible to estimate the mass of the companion and its distance from the star. The first discovery of a planet around another star was in 1995. At the time of writing, we know of around fifty planets orbiting various stars.
The first ones discovered were giant planets with masses much greater than the mass of Jupiter. Later we started to discover Jupiter and Saturn sized planets. Obviously, these are no use to support life, but what they do show is that planet building around stars may be a common occurrence. If a giant planet is there, then there may well be a solar system of planets. The nearest star to the Earth with a known planet is Epsilon Eridani in the constellation Eridanus. In biblical times, this constellation was identified with the river Euphrates. The star is 10.5 light years away. The mass of the planet around it is around the same as that of Jupiter. It takes about 7.1 years to orbit the star. Also, its orbit is highly eccentric. If it were in our solar system it’s orbit would take it from about 1.4 times further out than the Earth to 5.4 times further out than the Earth, which is just beyond the orbit of Jupiter.
Obviously, being the enquiring type that we are, we are not going to let it rest there. Plans are under way for a much larger space telescope called an interferometer. It has an apt name, the Darwin Mission. If it comes off, the European Space Agency will launch it around the year 2015. It consists of three space telescopes around three metres in diameter, due to be placed somewhere beyond the earth moon system and further out from the sun . This is a special point of equilibrium chosen because it moves around the sun at the same speed as the earth. After a two-year journey, they will arrive at their destination.. There it will join other previously launched detectors designed to perform similar feats. The three telescopes will line up in space about fifty metres apart providing a very long baseline. They will examine initially around one hundred and twenty stars. With such a combination of images, it should be possible to subtract the light from the host star and look at what remains. The idea being to detect Earth like planets and solar systems. Once we find such planets, it should then be possible to detect if plant life has established itself on such a planet by detecting the presence of oxygen in the atmosphere. The interferometer will look for the presence of both oxygen and water. Younger stars with Earth like planets will be our natural choice for any interstellar journey of the future.
A journey to another star appears out of the question under our present technology. Even a journey to our nearest star system of Alpha Centauri situated about four light years away would take about four years if we could travel at the speed of light. A journey at 10 times the speed of sound would go on for over one hundred thousand years and that is just to the nearest star. It is feasible that in the future that star ships may be able to accelerate to a significant fraction of the speed of light. Remember that we are not speculating on hundreds of years in the future but thousands or millions. Einstein’s equations prohibit speeds faster than light. These show that you would need an infinite amount of energy to achieve the speed of light with a physical object. The acceleration of electrons and protons in giant colliders show this to be true. Therefore, if you cannot break the rule for an electron, you have no chance with a space ship. Some scientists have speculated about space warps or wormholes in space as ways out of this dilemma, Yet, this is pure speculation and until someone breaks the rule by accelerating even a single proton to a speed faster than light then we are stuck. Relativity though may come to our rescue. One of the consequences of travelling at a significant fraction of the speed of light is that the Lorenz Contraction takes effect. This means that the apparent distance between any two points in the direction of travel shrinks to you as an observer. So although you cannot exceed the speed of light all the energy that you put into approaching that speed makes the distance of travel shorter instead. Let’s say we journeyed to our nearest star Alpha Centuri 4.2 light years away at 90% of the speed of light. Then effectively as far as the traveller is concerned, the distance becomes 1.8 light years; 95% of the speed of light reduces it to 1.3 light years; 99% gives 0.59 light years and 99.9% reduces it to 0.19 light years. Ideally, if we could do it, our giant cylindrical ark would accelerate at 9.81 m/s2. This has the advantage that it creates an artificial gravity on the craft, which is the same strength as that on Earth. It does not take much to show, that with a steady acceleration of this value, speeds, which are of a significant fraction of the speed of light, are attainable. At the half waypoint, we would turn the craft round and then decelerate at the same rate for the second half of the journey.
We have not yet considered another factor. The sun is like a giant spaceship itself as well as being our local nuclear reactor. It orbits around the centre of the galaxy at a speed of around 220 kilometres per second. Traditional understanding of the movement of stars in a galaxy, also allows it to oscillate slightly towards the centre and out again. While doing this, it also oscillates up and down in and out of the plane of the galaxy. There are others who paint a different, none traditional picture. Here younger stars move outwards from the central regions and older stars nearing the end of their lifetime move towards the centre of the galaxy. This would be why we observe a lot of old red giants towards the central regions of the galaxy.
Whichever model turns out to be true, we will probably not know the full picture until the Hipparcos survey of the movement of large numbers of stars has been fully analysed and interpreted correctly. What is a fact is that the sun will travel a very long way in the next four to five billion years of its lifetime. In a time of one billion years, the sun will travel over several hundred thousand light years of space. During this time, there may well be other stars which will pass within a few light years or less of the sun. If the star were much younger than our own and a future methods of detection showed us a planet about the same size of the Earth with liquid water and the presence of plants, then it may well be worth the trip for our continued existence. Let’s hope that it doesn’t turn out to be full of giant reptiles. That would pose a bit of a problem.
Naturally, taking our existing know how and technology with us would mean that the towns and cities built would not be like the mud huts of our ancestors, but would be more like the impressive cities described by John in his visions in the book of Revelation.
The book of Revelation comments, that there would be no night. At first thought, this does not seem feasible. Surely, it is not possible to have a planet with no night. Yet, go out on a winter’s night and stare up over the equator at the planet Jupiter, the brightest object after the planet Venus. Just imagine that it had been big enough for nuclear reactions to start up in its core, that is, about fifty times its present size. It would have been a star. This could have applied to any of the outer planets. The light source would be much smaller and further away than the sun, but nevertheless it would far outshine the reflected light that we get from the moon, illuminating the Earth at night. So day and night would not be, as we know them. The only time that it would go dark and the stars would be visible would be once a year when the small star was on the opposite side of the Sun to us. This would have made for interesting seasons.
We may be an exception in the Universe, just having one central star. It is more common for stars to be members of binary systems. In fact, the nearest star system to us, Alpha Centauri is actually a three star system. Obviously, God (the Universe) only knows, if and what type of star system we may encounter, way off in the future.
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