13) What is Time Dilation? Time dilation is counter-intuitive and seems to be totally nonsensical when taken to its logical conclusion. Basically what Einstein discovered was that time is not a constant! It depends on how fast you are travelling. The faster you travel the less you age! The ‘Twin Paradox’ says that if one twin flew off in a hypothetical space ship at close to the speed of light, on a 10 year round-trip to another star system, his brother, who had stayed behind on earth, would have died of old age when he got back! This is not mumbo jumbo, but scientific fact! The Sat-Nav in your car has to take time dilation into effect or you would end up miles from your desired destination!
13) Are we alone in the universe?
There is a very strong tendency among people to believe what they want to believe rather than what is demonstrably true. Many, myself included, would love to believe that flying saucers are real and that we are not alone in the universe, but wanting to believe can cloud your judgement. There has to be more concrete evidence than a few blurred photographs, some indentations in the ground, crop circles and stories of abduction before we can conclude that aliens really have visited us. You could ask yourself, ‘If a race of intelligent beings was advanced enough to build spacecraft, capable of transporting themselves trillions of miles across the galaxy and taking thousands of years to do so, would they really come all this way to our little planet just to make some fancy impressions in wheat fields? Does that strike you as being particularly intelligent? Scientists lean towards a premise known as ‘Occam’s Razor’ which roughly states: ‘The simplest explanation is most likely to be the correct one.’ As Richard Dawkins explains, ‘ It really comes down to parsimony, economy of explanation. It is possible that your car engine is powered by psychokinetic energy, but if it looks like a petrol engine, smells like a petrol engine and performs like a petrol engine, the sensible hypothesis is that it is a petrol engine!…If you hear the clip-clop of hooves in the street it could be a zebra or even a unicorn, but before you assume that it is anything other than a horse, you should demand a minimal standard of evidence! …By all means let us be open-minded, but not so open-minded that our brains drop out!’
Invoking Occam’s Razor should lead us to the very strong likelihood that crop circles are man-made and not indications of visitations by extra terrestrials from some planet trillions of miles away!
Some of these UFO enthusiasts even insult our intelligence (and demonstrate their own appalling ignorance) by claiming that the aliens have travelled from another galaxy! Our galaxy, the Milky Way, (comprising around 200,000 million stars), is part of a cluster of galaxies called the Local Group. This stretches the term ‘local’ to the limits because some of the others in this group are more than two million light years away from us. (One light year being the distance a beam of light, travelling at 186,000 miles per second, would cover in a year. About 6 million, million miles.) So even if they could travel at the speed of light (which they couldn’t) it would take them two million years to get here! And if they arrived at the opposite side of the Milky Way from us, it would still take them another thousand centuries just to cross our galaxy!
Some people argue, ‘If these aliens are very advanced they might well be able to travel at (or above) the speed of light. The very idea that there are limits in nature is abhorrent to many. After all, they argue, the speed of sound was a barrier once, but these days most jet fighter aircraft can exceed it. However, I’m afraid there really are limits in nature. There is an absolute lowest temperature of minus 273 degrees centigrade and nothing can be colder. The speed of light is also finite and cannot be exceeded. Only particles with no mass, such as photons, neutrinos etc can travel at the speed of light. Anything with mass, i.e. a spaceship, would need more energy than there is in the universe to accelerate it to light speed!
Although nothing can travel through space faster than the speed of light, space itself can expand faster. Currently the best theory for the origin of the universe postulates that there was an inflationary period of expansion of the universe, after the big bang, which was well above light speed. This concept is difficult to grasp, but Stephen Hawking’s book, ‘The Universe in a Nutshell’ explains it very well.
It is of course possible to travel faster than light relativistically. The American astronomer Edwin Hubble (after whom the space telescope is named) proved that the universe is expanding in all directions. By definition, the further away the other stars and galaxies become the faster they appear to be travelling, relative to us here on earth. Eventually their relative speed exceeds 186,000 miles per second and they disappear from our view. This means that there is an ‘edge’ to the universe beyond which we can never see! The Hubble telescope was pointed at a blank, dark area in space, where nothing was visible and the Ultra Deep Field viewer turned on. What it saw was incredible. There were millions of primitive galaxies looking as they did just a billion years after the big bang. When we look deep into space we see the stars not as they are now, but as they were when their light set off on its journey toward us, hundreds, thousands or millions of years ago! Hubble can see more than half way to the edge of the observable universe and most of the distance back to the beginning of time!
We live in exciting times in the exploration of space. In just the last few years we have found over 400 new planets orbiting stars other than our own sun! We always suspected that other star-systems would have attendant planets in orbit around them, but we couldn’t be sure until now. How these planets were found is a resounding triumph for science, because trying to see an ‘extra-sol’ planet, (a planet around another star) is like trying to see a firefly perched on the rim of a searchlight beamed straight at you!
No one has yet actually seen one of these planets, but we know they are there because of their dance with their parent star. Each causes the other to wobble as they circle each other and that wobble tells astronomers a great deal about the planet. They can deduce its size, mass, orbital radius and even the length of its year. Much of this information has been ratified by measuring the reduction in the amount of light radiating from the star as the planet crosses in front of it. In one instance they found not just one planet, but three orbiting the parent star! Although we have not yet seen such a planet, we are hopeful that we will soon be able to. Scientists are even now working to build a Hubble-style orbiting interferometer that will damp down the glare from these stars and actually allow us to see these new planets directly. Up to now the only planets we have identified have been Jupiter-sized giants in close orbits. These are highly unlikely places for life to exist, but when the interferometer is up and running, we hope to see earth-like planets that could harbour life, and possibly even intelligent life!
It would be egotistical in the extreme to suppose that amongst all those zillions of planets, around all those trillions of stars, in all those billions of galaxies ours is the only one with intelligent life.
Recently, however, a disturbing theory has been put forward as to why we have still not made contact with ET, even after SETI (The Search for Extra-Terrestrial Intelligence) has spent years scanning the radio waves from space. The theory is that Hypernovas may be sterilising all planetary life in their parent galaxies! A hypernova is the biggest explosion since the universe was formed by the big bang. Previously the greatest explosions known to astronomers were the Supernovas. When a massive star has burned most of its hydrogen fuel the internal pressure can no longer withstand the star’s huge gravitational attraction and the monster implodes! This triggers an explosion of staggering intensity, momentarily brighter than an entire galaxy, hurling matter light-years out into space and seeding the universe with heavy metals, elements and the ingredients of life. The corpse of the dead star is a bizarre object indeed; a rotating neutron star called a pulsar. It is like a giant atomic nucleus. Its immense magnetic field focuses its radiation into twin beams, from the star’s poles, like a cosmic lighthouse sweeping through space.
The discovery of the, even bigger, Hypernovas is worth a mention. In the 60’s and 70’s U.S. satellites, checking for Russian A-bomb explosions in space, detected hundreds of gamma-ray bursts coming from very distant galaxies, billions of light-years away. The Compton Gamma Ray Observatory, in orbit around the earth, is detecting more every day. These explosions are so powerful that they briefly outshine every star and galaxy in the whole universe combined! These are the Hypernovas. If one went off in our own galaxy it would strip away the atmospheres of every planet, including the earth, and we would all be roasted by the intense radiation. Perhaps this is why we are listening to a silent cosmos!
The best guess as to what generates these incredible events is that a super-massive star collapses so catastrophically that it forms not a pulsar, but a huge black hole.