At my Astronomy Society meeting the other week we had an expert talk to us about the Andromeda Galaxy. I also spoke to a woman who has witnessed a form of time travel but I’ll come to that later.
You can find the Andromeda galaxy as shown on the chart below. The constellation Cassiopeia appears in the north-east sky at nightfall and swings high to the north as evening progresses. It’s shaped like an M or W. Note that one half of the W is more deeply notched than the other half. This deeper V is your “arrow” in the sky, pointing to the Andromeda galaxy.
On a dark night, this galaxy looks like a faint smudge of light and where there is light pollution from street lamps etc it may be difficult to see. Nevertheless, binoculars should show it clearly and are better than a telescope to find it as binoculars have a wider field of view. Just don’t expect it to look like the photo though, even with a telescope.
A galaxy is a gravitationally bound system of stars, stellar remnants, dust and gas and dark matter. The word galaxy is derived from the Greek, galaxias, literally “milky”, and our own galaxy is called the Milky Way. Galaxies range in size from dwarfs with just a few thousand stars to giants with one hundred trillion stars, each orbiting their galaxy’s own centre of mass.
There can be billions of suns in a galaxy and according to most estimates there are one hundred billion galaxies. Just try and assimilate those figures for a minute to see how many suns there may be. I shouldn’t try to multiply them together to get a total as you will run out of space on a calculator. Now, try and imagine that many of those suns (stars) may well have planets orbiting them and multiply that figure by the previous ones. Still with the total calculation? Yeah….right. It is almost infinitesimal.
Andromeda is a spiral galaxy and is the closest one to us. It is very similar to our own Milky Way which you see high in the sky in the summer but it is two and a half million light-years away, How could we ever get there?
Light travels at a constant speed in a vacuum; 186,000 miles per second. The Scottish physicist James Clerk Maxwell showed that when electric and magnetic fields change in time, they interact to produce a travelling electromagnetic wave. Maxwell calculated the speed of the wave from his equations and found it to be exactly the known speed of light. This reveals that light is an electromagnetic wave. In 1905, Albert Einstein showed that c, the speed of light through a vacuum, is the universal speed limit. According to his special theory of relativity, nothing can move faster. He showed that the increased relativistic mass (m) of a body comes from the energy of motion of the body—that is, its kinetic energy (E)—divided by the speed of light squared (c2) i.e. E = mc2
This means that you would have to travel at 186,000 miles a second for two and a half million years before you reached Andromeda. Of course such astronomical distances are impossible to breach, unless a new form of propulsion is found or we harness the potential time/space anomalies of black holes or wormholes.
In String Theory For Dummies, the authors (Andrew Zimmerman Jones and Daniel Robbins) explain that in physics, time travel is closely linked to Einstein’s theory of relativity, which allows motion in space to actually alter the flow of time. This effect is known as Time Dilation and was one of the earliest predictions of relativity. This sort of time travel is completely allowed by the known laws of physics, but it allows only travel into the future, not into the past.
Time dilation and black hole event horizons provide intriguing ways of extending human life, and in science fiction they’ve long provided the means for allowing humans to live long enough to travel from star to star.
But when travelling at the speed of light there are other problems. Einstein’s equation indicates that time slows down when you reach the speed of light and mass gets bigger. At another of our meetings a few months ago I spoke to a lady who had actually operated the Large Hadron Collider at CERN. She said that she had witnessed this effect first hand. As the particle accelerated round and round, the atoms and molecules slowed down within it.
There is another example where time slows down, this time in general relativity, and it involves black holes. A black hole is formed when a very heavy star (usually) collapses in on itself due to the force of its own gravity. Fortunately, our Earth and Sun will never become black holes because their gravity is not sufficient to overcome the nuclear and atomic forces of their interiors. That’s handy, isn’t it?
Wikipedia describes a black hole as a geometrically defined region of spacetime exhibiting such strong gravitational effects that nothing—including particles and electromagnetic radiation such as light—can escape from inside it. The theory of general relativity predicts that a sufficiently compact mass can deform spacetime to form a black hole. The boundary of the region from which no escape is possible is called the event horizon.
In other words a black hole bends spacetime itself, to the point where even light can’t escape. This bending of spacetime means that as you approach a black hole, time will slow down for you relative to the outside world.
If you were approaching a black hole, someone watching from far away would see you approach it, slow down and eventually hover outside it. (There are other complications with ‘watching’ but I won’t bother to explain them here.) If you could somehow resist the terrific force of gravity pulling you into the hole, they would see you through your spaceship window sitting still, having no idea that as you glide past the black hole’s event horizon, thousands of years were passing outside of the black hole. That’s where the theories about time travel start.
Could we find a way of using the super massive black hole at the centre of our own Milky Way galaxy to allow us to bend Time so we could reach vast distances within our lifetimes? Every galaxy has a super massive black hole at its centre. Could they be linked in some way? I don’t know. I am just postulating the theory.
With the billions of suns available it is quite possible there are quite a number of planets circling these suns.That should make the probability of another planet like ours quite feasible, so you would think. However, it is not at all certain that this is so. Scientists think that our planet is at the optimum distance from our star, the sun, and has the right tilt of axis and other factors which enable life to grow just as it has. Our moon provides both our tides, a calendar and a light for hunting at night (important many centuries ago). Even a small difference in distance from the star, the thickness of our atmosphere, or any of these things would make life improbable.
Consequently, as strange as it may seem, it is quite likely that there are no other planets like ours in the whole of the universe. We are unique. If so, does this rather smack of creation rather than random chance? The whole scale of the universe and infinite distances is something that mortal minds cannot really comprehend let alone the possibility of a multi-universe system and other dimensions. Is heaven somewhere in the realms of dark matter, dark energy or another dimensional universe? For me, science does not weaken my belief that all this is organised… and not just the result of some random act.
When we were talking about the Andromeda Galaxy at my meeting and wondering whether there is any life on any planets in that system, it occurred to me that we are looking at light that came to us from two a half million years ago. Therefore, a lot may have happened on any such planet in that system since then and I just wonder whether some person is using a telescope on that planet looking up at our galaxy and wondering if there is any life here? At this moment, he would see only our galaxy as it was two and a half million years ago, when Neanderthal man was roaming around on Earth but using language just like we do today. Just think of the advances we have made since then that the Andromeda man does not know about. Similarly, I wonder what has happened there in Andromeda in the last two and a half million years? Will it take another two and a half million years to find out, or will something staggering happen before that?
And remember….Time flies like an arrow. Fruit flies like a banana.
(Chart and image courtesy of EarthSky.org)