Space Travel
Jules Verne published some exciting scientific predictions in the 19th Century but his proposed use of a large cannon to fire people into space was a bit too far fetched.
In his book entitled "Journey to the Moon", he envisaged a giant cannon firing a projectiles containing astronauts into space and onto the moon. (The image to the left depicts his idea of projectile trains carrying people into space.) In practice, any inhabitants of a fired projectile capable of escaping the earth's gravitation would not survive the required degree of acceleration.
The best way of getting off the earth and into space is by rocket. Rockets can take us into space but they are also extremely limited in what they can do. Distances between stars are enormous - and covering these distances will take enormous amounts of time.
What really limits us is the speed of light. As far as we know, nothing material can travel at or faster than the speed of light. Scientists have apparently managed to accelerate electrons to 99.99999995% of the speed of light but if Einstein is correct, it will take an infinite amount of energy to accelerate an electron to the speed of light - at which time it's mass will become infinite.
Even if we could build a rocket that could travel at 99% of the speed of light - say 298,000,000 meters per second, it would take about 4.5 years to reach Proxima Centauri which is the nearest star outside our solar system. The observable universe contains over 100 billion galaxies that each contain more that 100 billion solar systems. Traveling at the speed of light, it would take more that 300,000 years to reach one of the stars on the outer edge of our own galaxy which is the Milky Way.
However, the faster we travel the slower time appears to pass. As we get closer to the speed of light, the faster we travel the slower time appears to pass. This means that if we could travel near the speed of light, we could reach the edge of the Milky Way in what would appear to us to be less than 10 years - but when we returned to Earth, (if it was still there) we might find that more than 600,000 Earth-years had elapsed.
The rate at which time progresses is not the same everywhere. It depends on our frame of reference - where we are and what we are doing. We have to have a point of reference from which to measure time and we have to have a point of reference from which to measure points in space.
Speed is a combination of time and distance. If something is traveling at what appears to be a constant speed, it will speed up if time slows down. This is more evident as we approach the speed of light. So, something traveling at near the speed of light will cover much larger distances in what appears to be a smaller amount of time.
Relativity
The fundamental idea of the Theory of Relativity published by Einstein in 1904, was that the laws of science should be the same for all freely moving observers, no matter what their speed: All observers should measure the same speed of light, no matter how fast they are moving.So, if a person could travel at the speed of light, with a beam of light traveling alongside, the person would still observe the beam of light to be traveling at the speed of light relative to his or her position.
An important consequence of relativity is the way it has revolutionized our ideas of space and time. The theory of relativity put an end to the theory of absolute time.
The publication of Einstein's ideas on relativity effectively created a new branch in physics called Modern Physics. Classical Physics is represented mostly by the work that was done before Einstein and is dominated or summarized to a large extent by the work of Isaac Newton. Modern Physics refers to physics knowledge obtained in the 20th century. It is often used to represent the subjects of Quantum Mechanics and Relativity.
We'll take a much closer look at Relativity and some of the current ideas on time and space in the Fourth Unit of this curriculum. The first three units are devoted to classical (and possibly more useful) aspects of physics.
During the next few weeks, we'll study energy, motion and mechanics. We will build a range of useful and exciting devices and gain some experience in measurement and scientific investigation - and become familiar with some of the language, images and models of Classical Physics. pole.
DIMENSIONS
Simple Dimensions The simplest definition (from an engineering perspective) is that a dimension is anything in which something can be measured.
The most common dimensions are length, mass and time.
Each dimension is measured in a Unit. The most commonly used units in scientific circles are the SI units. These include meters, kilograms and seconds.
Virtual Dimensions
If we want to explain more complex ideas such as Time Warps, we need to use a mathematical approach. In mathematics, we are allowed to use virtual (or imaginary) numbers and virtual dimensions. Just like the virtual images we see behind mirrors - or the virtual situations we find in computer games, virtual dimensions help us to work with, and get a feel for, things we cannot experience directly.
From a mathematical perspective, an event can be defined by three dimensions in space and a fourth dimension which is time. It can also be defined within a single dimension that Einstein proposed and called "Spacetime". .
Lets see how forces and energy behave in time and space at or near ground level on earth.
More on Forces and Energy in Space and Time
MODERN PHYSICS
Mathematical models consist of single equations or groups of equations. Their purpose - as with real models and simulators - is to help us to picture and experiment with things that are either too large, too complicated or too dangerous for us to work with directly.
In Einstein's models - or virtual depictions of the real universe, he proposed that the apparent flexibility of time and space could best be reflected in a model that used spacetime as a single dimension.
The publication of Einstein's ideas on relativity effectively created a new branch in physics called Modern Physics. Classical Physics is represented mostly by the work that was done before Einstein and is dominated or summarized to a large extent by the work of Isaac Newton. Modern Physics refers to physics knowledge obtained in the first half of the 20th century. It is often used to represent the subjects of Quantum Mechanics and Relativity. More on Forces and Energy in Space and Time
The Cannon. Jules Verne's projectile being fired from a cannon in the ground.