The success of 2009's "Avatar" demonstrates that moviegoers appreciate the difference between 2-D and 3-D, and they're willing to pay a little more for an upgrade. Most of us are accustomed to watching 2-D; even though characters on the screen appear to have depth and texture, the image is actually flat. But when we put on those 3-D glasses, we see a world that has shape, a world that we could walk in. We can imagine existing in such a world because we live in one. The things in our daily life have height, width and length. But for someone who's only known life in two dimensions, 3-D would be impossible to comprehend. And that, according to many researchers, is the reason we can't see the fourth dimension, or any other dimension beyond that. Physicists work under the assumption that there are at least 10 dimensions, but the majority of us will never "see" them. Because we only know life in 3-D, our brains don't understand how to look for anything more.
In 1884, Edwin A. Abbot published a novel that depicts the problem of seeing dimensions beyond your own. In "Flatland: A Romance of Many Dimensions," Abbot describes the life of a square in a two-dimensional world. Living in 2-D means that the square is surrounded by circles, triangles and rectangles, but all the square sees are other lines. One day, the square is visited by a sphere. On first glance, the sphere just looks like a circle to the square, and the square can't comprehend what the sphere means when he explains 3-D objects. Eventually, the sphere takes the square to the 3-D world, and the square understands. He sees not just lines, but entire shapes that have depth. Emboldened, the square asks the sphere what exists beyond the 3-D world; the sphere is appalled. The sphere can't comprehend a world beyond this, and in this way, stands in for the reader. Our brains aren't trained to see anything other than our world, and it will likely take something from another dimension to make us understand.
But what is this other dimension? Mystics used to see it as a place where spirits lived, since they weren't bound by our earthly rules. In his theory of special relativity, Einstein called the fourth dimension time, but noted that time is inseparable from space. Science fiction aficionados may recognize that union as space-time, and indeed, the idea of a space-time continuum has been popularized by science fiction writers for centuries [source: Overbye]. Einstein described gravity as a bend in space-time. Today, some physicists describe the fourth dimension as any space that's perpendicular to a cube -- the problem being that most of us can't visualize something that is perpendicular to a cube.
Researchers have used Einstein's ideas to determine whether we can travel through time. While we can move in any direction in our 3-D world, we can only move forward in time. Thus, traveling to the past has been deemed near-impossible, though some researchers still hold out hope for finding wormholes that connect to different sections of space-time.
If we can't use the fourth dimension to time travel, and if we can't even see the fourth dimension, then what's the point of knowing about it? Understanding these higher dimensions is of importance to mathematicians and physicists because it helps them understand the world. String theory, for example, relies upon at least 10 dimensions to remain viable [source: Groleau]. For these researchers, the answers to complex problems in the 3-D world may be found in the next dimension -- and beyond.
Although the 1950s are most often considered the 3-D movie decade, the first feature length 3-D film, "The Power of Love," was made in 1922. Since that time the use of 3-D technology in theaters and on television has drifted in and out of mainstream popularity. But, whether you've used them for the big screen or at home in front of your television, you have to admit 3-D glasses are incredibly cool.
They make the movie or television show you're watching look like a 3-D scene that's happening right in front of you. With objects flying off the screen and careening in your direction, and creepy characters reaching out to grab you, wearing 3-D glasses makes you feel like you're a part of the action - not just someone sitting there watching a movie. Considering they have such high entertainment value, you'll be surprised at how amazingly simple 3-D glasses are.
In a movie theater, the reason why you wear 3-D glasses is to feed different images into your eyes just like a View-Master does. The screen actually displays two images, and the glasses cause one of the images to enter one eye and the other to enter the other eye. There are two common systems for doing this:
Red/Green or Red/Blue
Although the red/green or red/blue system is now mainly used for television 3-D effects, and was used in many older 3-D movies. In this system, two images are displayed on the screen, one in red and the other in blue (or green). The filters on the glasses allow only one image to enter each eye, and your brain does the rest. You cannot really have a color movie when you are using color to provide the separation, so the image quality is not nearly as good as with the polarized system.
The red and blue lenses filter the two projected images allowing only one image to enter each eye.
At Disney World, Universal Studios and other 3-D venues, the preferred method uses polarized lenses because they allow color viewing. Two synchronized projectors project two respective views onto the screen, each with a different polarization. The glasses allow only one of the images into each eye because they contain lenses with different polarization.
The polarized glasses allow only one of the images into each eye because each lens has a different polarization.
There are some more complicated systems as well, but because they are expensive they are not as widely used. For example, in one system, a TV screen displays the two images alternating one right after the other. Special LCD glasses block the view of one eye and then the other in rapid succession. This system allows color viewing on a normal TV, but requires you to buy special equipment.
3-D glasses with red/blue lenses
From millennium-skipping Victorians to phone booth-hopping teenagers, the term time travel often summons our most fantastic visions of what it means to move through the fourth dimension. But of course you don't need a time machine or a fancy wormhole to jaunt through the years.
As you've probably noticed, we're all constantly engaged in the act of time travel. At its most basic level, time is the rate of change in the universe -- and like it or not, we are constantly undergoing change. We age, the planets move around the sun, and things fall apart.
We measure the passage of time in seconds, minutes, hours and years, but this doesn't mean time flows at a constant rate. Just as the water in a river rushes or slows depending on the size of the channel, time flows at different rates in different places. In other words, time is relative.
But what causes this fluctuation along our one-way trek from the cradle to the grave? It all comes down to the relationship between time and space. Human beings frolic about in the three spatial dimensions of length, width and depth. Time joins the party as that most crucial fourth dimension. Time can't exist without space, and space can't exist without time. The two exist as one: the space-time continuum. Any event that occurs in the universe has to involve both space and time.
In this article, we'll look at the real-life, everyday methods of time travel in our universe, as well as some of the more far-fetched methods of dancing through the fourth dimension.
Let's say you are in plane flying westward around the Earth's equator. At the equator, the time zones are a little over 1,000 miles (1,609 km) apart, so to cross one every hour, your plane would have to fly at over 1,000 miles per hour (1,609 kph).
If you started flying at 12:00 noon, at 1:00 p.m. (according to your watch) you would cross a time zone, making it 12:00 noon again. This process would continue for as long as your plane could stay in the air: As soon as your watch passed 12:59, you'd have to turn it back to 12:00 again. For your entire westward trip around the Earth, the time would be between 12:00 noon and 1:00 p.m.
What you are really doing is maintaining your position on the Earth relative to the sun. You are flying at the same speed as the Earth is rotating, but in the opposite direction, so the sun is always in the same part of the sky. We know that at noon the sun is approximately overhead, so on this journey the sun would always be over the plane. In effect, you are chasing noon around the world. If you prefer sunsets, you could watch a perpetual sunset by departing on your westward journey just as the sun is setting.
What if your plane could stay in the air for days, or even weeks? Would you stand still in time forever? The answer is that the time of day would always be the same, but the date would continue to change. The time would always be between 12:00 noon and 1:00 p.m., but each time you crossed the International Date Line, it would instantly become 12:00 noon the next day.
The International Date Line runs from the North Pole to the South Pole, through the Pacific Ocean. It is on the opposite side of the world from the Prime Meridian (which is in Greenwich, England).
Before the establishment of the International Date Line, Portuguese explorer Ferdinand Magellan, who was the first to circumnavigate the Earth, found that when he arrived back, he was one full day behind. His crew had kept careful track of each day in their journals, and it turned out that over the course of the almost-three-year voyage, they had seen one less sunrise and sunset than those on land.