Try to envision a universe with nine spatial dimensions and one dimension of time. Such is the emerging view of our universe according to String Theory. Or, if you prefer the closely related M-theory, you will have to live with a universe of ten spatial dimensions and one of time.
I used to lie awake nights pondering where the extra dimensions were to be found. I would concentrate on a corner of the room, where two walls and the ceiling met, and try to envision a fourth spatial dimension. Our whole world view of normal space is constricted to three spatial dimensions, length, width and height. Trying to envision anything beyond those is very difficult.
But the extra spatial dimensions are not like the familiar width, length and height. Rather, they seem to be curled up inside of ordinary space as the image above suggests. They are closer to us than our own skin, and yet the open up to the very edges of our universe and perhaps beyond.
To envision String Theory, we must leave behind our normal concepts of space. Normal space that is bound by boxes demarcated by width, length and height. String Theory does not involve a fourth or fifth box dimension, but something much more exciting.
Think of the extra dimensions not as spaces but as channels or conduits. Our houses are not just boxes stacked together. What makes our houses actually work are the conduits that supply us with water, electricity, heating and cooling, and connectivity. When we flip a light switch, we expect the light to come on. We do not need to know the location of the electrical wiring, and so we do not even think about it.
Of course one could argue that these conduits are simply small boxes hidden within the big boxes of the house, and that would be technically correct. An electrical cable actually does have dimensions, and does occupy specific spaces within the walls, ceilings and floors of the house. But there are no dimensions to a Wi-Fi signal. There is no wiring schematic to show where the WI-Fi signal runs. It seems not to exist in ordinary space. Because Wi-Fi is totally disembodied, it makes an even better analogy for extra dimensions.
For most of human history, if you wanted to send a message a long distance, you would have to entrust it to a human (or string of humans), who would bodily carry the letter to its destination. A human being, moving under her or his own power, can cover something like 32 kilometers (20 miles) per day, and that assumes the most optimal terrain an weather conditions. At the end of the War of 1812, hostilities continued for more than sixty days after the war had officially ended because of the difficulties in spreading word of the wars ending to remote frontier regions.
Radio communications were as much a part of the universe back then as they are now. The problem was that the combatant in 1812 lacked the understanding of radio as well as any technological infrastructure to exploit it.
Today is a much different world. It is now possible for a person in Nome, Alaska to play a chess game with someone from Pretoria, South Africa, and to conclude that game real-time within in five or ten minutes. In the old days it would have taken many years of postal chess, where one move at a time would have been mailed from one participant to another, with each move requiring weeks or even months to arrive at its destination. We have achieved on this planet a state of simultaneity. And what I mean by that is that whatever happens at any place on the planet is now knows instantly across the whole planet, or at least in those places that have the technological infrastructure to tap into the planetary communications grid.
But once we leave the confines of this planet, that state of simultaneity vanishes. On earth, light speed communication counts as instantaneous, as radio waves can circle our planet seven-and-one-half times in one second. As we reach out into space, even a signal to Mars can take up to forty-five minutes. There is no need for a message to Curiosity telling it to, “Look out for that rock!” because by the time the message gets there, the rock will be just a distant memory.
Captain Kirk could always call Star Fleet Headquarters on “sub-space” communications links.
Now back to String Theory. What if some of these extra dimensions could provide us with simultaneity throughout the universe? This unfamiliar concept would totally change our society, not to mention our conception of the universe.
Think of two stars that are 10,000 light years apart. Now let us assume that both have civilizations and that both of these civilizations construct radio telescopes at the same time. Can we call this a simultaneous event? I think not because these two civilizations are not aware of each other’s presence. It also works to say that they are not aware of each other’s presents. Because of the messaging time, neither could be aware of the other’s existence for at least 10,000 years. A signal followed by a response would take at least 20,000 years. After such a long time interval one or both of those civilizations could have died out, or have been pushed back into the Stone Age.
Civilization on earth has only been around for 10,000 years. Civilization refers to the creation of walled cities, the development of agriculture, and the creation of writing and mathematics. The earth has had radio telescopes for only 100 years, and really good ones for about 50 years. While radio has been around since the late 19th Century, there was not much in the way of outbound radio messaging that could be intercepted in other star systems until World War II. Thus, our messages have been streaming out for only about sixty years to star systems in a sphere with a 60 light year radius. The Milky Way Galaxy has a radius of some 60,000 light years.
Now, let us suppose that String Theory allows for one or more of the extra dimensions to function as a channel or conduit through which connectivity is possible. Imagine if these two civilizations could sit down for a friendly game of chess in real time.
Somehow logic demands that there be universal simultaneity. We have just not discovered the technology to understand and exploit that technology. String Theory gives us at least the possibility of knowing what is happening on Proxima Centauri right now, without the need to wait 4.2 years to receive the message via light waves.
In 1961, Frank Drake formulated his famous equation to predict the likelihood of intelligent, technological life in the galaxy. Since that time we have made numerous scientific advances. In 1961 we had not found any extra-solar planets, and were not even sure if they existed. Today we have found hundreds of extra-solar planets and now believe that there are planets surrounding most stars.
Drake made his calculation and came up with the number 10. His answer was that there were ten civilizations in our galaxy with intelligent, technological societies with which we could communicate.
A technological civilization simply means a society capable of building radio telescopes to scan the heavens, for without such instruments any extraterrestrial contact is simply impossible. It should be noted that the first radio telescope on the earth was built in 1931. So, by this definition, we have been a technological society for less than one hundred years, a brief moment in the history of the cosmos.
The Drake equation states that:
N = the number of civilizations in our galaxy with which communication might be possible;
R* = the average rate of star formation per year in our galaxy
fp = the fraction of those stars that have planets
ne = the average number of planets that can potentially support life per star that has planets
fℓ = the fraction of the above that actually go on to develop life at some point
fi = the fraction of the above that actually go on to develop intelligent life
fc = the fraction of civilizations that develop a technology that releases detectable signs of their existence into space
L = the length of time for which such civilizations release detectable signals into space.
But now it would appear that Frank Drake was an optimist. Steven Hawking has predicted that we might be alone in the Universe as the only technological society.
The nearest star to us is a red dwarf star named Proxima Centauri at a distance of 4.24 light years. This is our nearest neighbor in interstellar space, but getting there would take us some 80,000 years traveling at space shuttle speed. Just beyond Proxima Centauri is the binary star system Alpha Centauri A and B at 4.37 light years from our sun. And, what if we went there and found nothing? What would be our next destination and how long would it take to get there?
We are learning how hard and slow the process is to evolve from primitive life forms to advanced, technological civilizations. On earth this process took some four billion years. This means that a planetary nursery must be maintained in a relatively steady state for billions of years in order for an intelligent, technological society to emerge.
Humanity went almost extinct 73,000 years ago from the great Toba super-volcano in Sumatra. Some sources say that only around 10,000 humans were left on the planet, while other sources say that the human population dwindled down to a few hundred or even a few dozen. After millions of years of evolution we almost died out, but a few survived and our species went on to build a radio telescope.
There are new factors, not found in the Drake Equation, that may set earth off as the sole technological society:
The earth is big enough to sustain its magnetic field and the shielding that it produces for billions of years. Because the earth’s core is still molten, we have a magnetic shield that protects us from harmful radiation, coronal mass ejections, and the solar wind that could strip our planet of its atmosphere and water. When Mars lost its magnetic shield that planet died of these effects.
The earth has plate tectonics that continuously recycle the continents and continuously bring new minerals to the surface.
The earth has a large moon that provides gyroscopic stability and prevents our axis from wobbling too much. This provided for climactic stability over millennium in order that civilization may develop and thrive in one place without disruption or dislocation. Imagine, for example, if the earth’s axis tilted so that Europe dropped down to the latitude of the Sahara Desert. Any such civilization at that latitude would be doomed.
The moon was originally much closer to the earth than it is now. In the early days the moons tidal pull upon the earth was much larger. The effect of this tidal pool was to stir the waters in the inter tidal zone. This tidal stirring, this mixing of nutrients, proteins, and amino acids may well have aided in the formation of life.
The earth has big brother Jupiter that protects us from asteroid bombardment by corralling many errant space rocks and ice balls before they hit the earth. This was recently demonstrated by the Jovian capture and destruction of the Shumaker-Levi 9 comet.
The earth orbits a single star. Any planets in multiple star systems would be at a distinct disadvantage. It would be very difficult for a planet in a multiple star system, such as Alpha Centauri, to find a stable orbit in the “Goldilocks” zone where it is neither too hot nor too cold. Also, it is likely that at some point in time the planet would be either torn apart by gravitational forces or slung out into the interstellar void.
Our sun will shine for another five billion years. Our technological civilization is flourishing as our sun is in the middle of its useful life. Scientists believe that the world will be habitable for at least the next billion years or so, unless we destroy ourselves earlier. After the next five billion years we know that the sun will swell up into its red giant phase, with its outer edged touching the earth’s orbit. Long before the sun reaches its full expansion the earth will become a scorched, lifeless cinder.
Other planets in our galaxy may not be so lucky.
Carl Sagan worried that we might have reached the required level of technological development (i.e. radio telescopes) just in time to destroy ourselves with nuclear weapons. For today’s generation our main worry might be global warming. It is sad, but it seems that achieving the technological pinnacle of a radio telescope gives us power over nature to destroy ourselves and our habitat.
Steven Hawking said that since we might be the only intelligent, technological society in the galaxy, we may want to survive and continue.