A few things in my experience have left me uneasy, as the pure wonderment puzzled me beyond my own ability to reason with them. This sensation however made me appreciate this comic enough to buy the shirt mentioned previously on this blog) which is the image in the last frame. I'll tackle the most pertinent group of phenomena whose mystery previously bothered me here, aside from particle physics vs. classical physics, and unified field theory vs. theory of everything:
- Does electricity actually travel at the speed of light (c)?
- If that speed, for light itself, is defined inside a vacuum, without any resisting obstacles, and light itself slows down through varying media, how does electricity do it, requiring a medium to travel at all, thus not occurring in a vacuum?
- If Natural Law is totally efficient (η), and a line is the shortest distance between two contact points; why and how does lightning travel in an arc that is non-linear, and why and how can it have branches?
- If electricity travels at c, and lightning strikes as electricity, and one can't notice light travelling from the clouds to Earth, why is the light emitted by lightning apparent to be travelling between the clouds and Earth at non-instant speeds, to the naked eye?
1. Yes. Electricity travels the same exact speed, through a wire, that light travels through a vacuum (c). But here are the problems with that:
- Electricity is the flow of electrons, and electrons have mass. Relativity says that massive bodies cannot travel at c. Only things without mass (zero rest mass) can (and must) travel at c.
- Even light cannot travel at c, when it is travelling through other substances, slowing down to travel through glass, water, air, etc. So, how can electrons travel at c, through copper?
I am not happy!
2. So electricity does indeed travel at c, but electrons themselves do not travel anywhere near c, within a wire. When an electron enters one end of a wire, another electron leaves the other end of the wire. This effect takes place at c, but they were not the same electron. The information, or the current, however, will have been the same as communicated to the beginning end of the wire, sans the wire's resistance.
I am happy.
3. In an electrical storm, the storm clouds are charged like giant capacitors in the sky. In the process of the water cycle forming the clouds, moisture accumulates as millions and millions of water droplets and ice suspended in the air. As the process of evaporation and condensation continues, these droplets collide with other moisture that is in the process of condensing as it rises. Also, the rising moisture may collide with ice or sleet that is in the process of falling to the Earth or located in the lower portion of the cloud. The importance of these collisions is that electrons are knocked off of the rising moisture, thus creating a charge separation.
3. In an electrical storm, the storm clouds are charged like giant capacitors in the sky. In the process of the water cycle forming the clouds, moisture accumulates as millions and millions of water droplets and ice suspended in the air. As the process of evaporation and condensation continues, these droplets collide with other moisture that is in the process of condensing as it rises. Also, the rising moisture may collide with ice or sleet that is in the process of falling to the Earth or located in the lower portion of the cloud. The importance of these collisions is that electrons are knocked off of the rising moisture, thus creating a charge separation.
The newly knocked-off electrons gather at the lower portion of the cloud, giving it a negative charge. The rising moisture that has just lost an electron carries a positive charge to the top of the cloud. Beyond the collisions, freezing plays an important role. As the rising moisture encounters colder temperatures in the upper cloud regions and begins to freeze, the frozen portion becomes negatively charged and the unfrozen droplets become positively charged. At this point, rising air currents have the ability to remove the positively charged droplets from the ice and carry them to the top of the cloud. The remaining frozen portion would likely fall to the lower portion of the cloud or continue on to the ground. Combining the collisions with the freezing, we can begin to understand how a cloud may acquire the extreme charge separation that is required for a lightning strike.
The strength or intensity of the electric field is directly related to the amount of charge buildup in the cloud. As the collisions and freezing continue to occur and the charges at the top and bottom of the cloud increase, the electric field becomes more and more intense -- so intense, in fact, that the electrons at the Earth's surface are repelled deeper into the Earth by the strong negative charge at the lower portion of the cloud. This repulsion of electrons causes the Earth's surface to acquire a strong positive charge. All that is needed now is a conductive path for the negative cloud bottom to contact the positive Earth surface. The strong electric field, being somewhat self-sufficient, creates this path.
That electric field causes the air around the cloud to "break down," allowing current to flow in an attempt to neutralize the charge separation. Simply stated, the air breakdown creates a path that short-circuits the cloud/Earth as if there were a long metal rod connecting the cloud to the Earth. The electric field causes the surrounding air to become separated into positive ions and electrons -- the air is ionized. This ionized, highly conductive air is known as plasma. Once the ionization process begins and plasma forms, a path is not created instantaneously. In fact, there are usually many separate paths of ionized air stemming from the cloud. These paths are typically referred to as step leaders.
The step leaders propagate toward the Earth in stages, which do not have to result in a straight line to the Earth. The air may not ionize equally in all directions. Dust or impurities in the air may cause the air to break down more easily in one direction, giving a better chance that the step leader will reach the Earth faster in that direction. Efficiency outside a straight line (η). Also, the shape of the electric field can greatly affect the ionization path. This shape depends on the location of the charged particles, which in this case are located at the bottom of the cloud and the Earth's surface. If the cloud is parallel to the Earth's surface, and the area is small enough that the curvature of the Earth is negligible, the two charge locations will behave as two charged parallel plates. The lines of force (electric flux) generated by the charge separation will be perpendicular to the cloud and Earth.
That electric field causes the air around the cloud to "break down," allowing current to flow in an attempt to neutralize the charge separation. Simply stated, the air breakdown creates a path that short-circuits the cloud/Earth as if there were a long metal rod connecting the cloud to the Earth. The electric field causes the surrounding air to become separated into positive ions and electrons -- the air is ionized. This ionized, highly conductive air is known as plasma. Once the ionization process begins and plasma forms, a path is not created instantaneously. In fact, there are usually many separate paths of ionized air stemming from the cloud. These paths are typically referred to as step leaders.
The step leaders propagate toward the Earth in stages, which do not have to result in a straight line to the Earth. The air may not ionize equally in all directions. Dust or impurities in the air may cause the air to break down more easily in one direction, giving a better chance that the step leader will reach the Earth faster in that direction. Efficiency outside a straight line (η). Also, the shape of the electric field can greatly affect the ionization path. This shape depends on the location of the charged particles, which in this case are located at the bottom of the cloud and the Earth's surface. If the cloud is parallel to the Earth's surface, and the area is small enough that the curvature of the Earth is negligible, the two charge locations will behave as two charged parallel plates. The lines of force (electric flux) generated by the charge separation will be perpendicular to the cloud and Earth.
We are taught that the shortest distance between two points is a straight line; but in the case of electric fields, the lines of force (flux lines) may not follow the shortest distance, as the shortest distance does not always represent the path of least resistance.
I am happy.
4. So now we have an electrically charged cloud with ever-growing step leaders stretching out toward the Earth in stages. These leaders are faintly illuminated in a purplish glow and may sprout other leaders in areas where the original leaders bend or turn. Once begun, the leader will remain until the current flows, regardless of whether or not it is the leader that reaches the ground first. The leader basically has two possibilities: continue to grow in stages of growing plasma or wait patiently in its present plasma condition until another leader hits a target. These branches are looking for a target to expel the electrical charge, and one will become the most efficient path, thus connecting first, leaving the remaining branches to glow along with it.
As the step leaders approach the Earth, objects on the surface begin responding to the strong electric field. The objects reach out to the cloud by "growing" positive streamers. These streamers also have a purplish color and appear to be more prominent on sharp edges. The human body can and does produce these positive streamers when subjected to a strong electric field such as that of a storm cloud. In actuality, anything on the surface of the Earth has the potential to send a streamer. Once produced, the streamers do not continue to grow toward the clouds; bridging the gap is the job of the step leaders as they stage their way down. The streamers wait patiently, stretching upward as the step leaders approach.
After the step leader and the streamer meet, the ionized air (plasma) has completed its journey to the Earth, leaving a conductive path from the cloud to the Earth. With this path complete, current flows between the Earth and the cloud. This discharge of current is nature's way of trying to neutralize the charge separation. The flash we see when this discharge occurs is not the strike -- it is the local effects of the strike.
Any time there is an electrical current, there is also heat associated with the current. Since there is an enormous amount of current in a lightning strike, there is also an enormous amount of heat. In fact, a bolt of lightning is hotter than the surface of the Sun. This heat is the actual cause of the brilliant white-blue flash that we see.
When a leader and a streamer meet and the current flows (the strike), the air around the strike becomes extremely hot. So hot that it actually explodes because the heat causes the air to expand so rapidly. The explosion is soon followed by what we all know as thunder.
When there are many other branches that flash at the same time as the main strike, and the main strike flickers or dims a few more times, the branches that you see are actually the step leaders that were connected to the leader that made it to its target. When the first strike occurs, current flows in an attempt to neutralize the charge separation. This requires that the current associated with the energy in the other step leaders also flows to the ground. The electrons in the other step leaders, being free to move, flow through the leader to the strike path. So when the strike occurs, the other step leaders are providing current and exhibiting the same heat flash characteristics of the actual strike path. After the original strike occurs, it is usually followed by a series of secondary strikes. These strikes follow only the path of the main strike; the other step leaders do not participate in this discharge.
In nature, what we see is often not what we get, and this is definitely the case with the secondary strikes. It is very possible that the main strike can be followed by 30 to 40 secondary strikes. Depending on the time delay between the strikes, we may see what looks like one long-duration main strike, or a main strike followed by other flashes along the path of the main strike. These conditions are easy to understand if we realize that the secondary strikes can occur while the flash from the main stroke is still visible. Obviously, this would cause a viewer to think that the main-strike flash lasted longer than it actually did. By the same token, the secondary strikes may occur after the flash from the main strike ends, making it appear that the main strike is flickering.
The actual light you see when viewing a lightning strike is the air associated with he strike, exploding. Explosion chain reactions take longer time to travel than actual light or electricity, so we can see the light emited by the fire, actually travelling along the strike path, much in the same way that we familiarly see lightning occur several seconds before actually hearing the explosions, as the sound waves also travel much slower than c.
As the step leaders approach the Earth, objects on the surface begin responding to the strong electric field. The objects reach out to the cloud by "growing" positive streamers. These streamers also have a purplish color and appear to be more prominent on sharp edges. The human body can and does produce these positive streamers when subjected to a strong electric field such as that of a storm cloud. In actuality, anything on the surface of the Earth has the potential to send a streamer. Once produced, the streamers do not continue to grow toward the clouds; bridging the gap is the job of the step leaders as they stage their way down. The streamers wait patiently, stretching upward as the step leaders approach.
After the step leader and the streamer meet, the ionized air (plasma) has completed its journey to the Earth, leaving a conductive path from the cloud to the Earth. With this path complete, current flows between the Earth and the cloud. This discharge of current is nature's way of trying to neutralize the charge separation. The flash we see when this discharge occurs is not the strike -- it is the local effects of the strike.
Any time there is an electrical current, there is also heat associated with the current. Since there is an enormous amount of current in a lightning strike, there is also an enormous amount of heat. In fact, a bolt of lightning is hotter than the surface of the Sun. This heat is the actual cause of the brilliant white-blue flash that we see.
When a leader and a streamer meet and the current flows (the strike), the air around the strike becomes extremely hot. So hot that it actually explodes because the heat causes the air to expand so rapidly. The explosion is soon followed by what we all know as thunder.
When there are many other branches that flash at the same time as the main strike, and the main strike flickers or dims a few more times, the branches that you see are actually the step leaders that were connected to the leader that made it to its target. When the first strike occurs, current flows in an attempt to neutralize the charge separation. This requires that the current associated with the energy in the other step leaders also flows to the ground. The electrons in the other step leaders, being free to move, flow through the leader to the strike path. So when the strike occurs, the other step leaders are providing current and exhibiting the same heat flash characteristics of the actual strike path. After the original strike occurs, it is usually followed by a series of secondary strikes. These strikes follow only the path of the main strike; the other step leaders do not participate in this discharge.
In nature, what we see is often not what we get, and this is definitely the case with the secondary strikes. It is very possible that the main strike can be followed by 30 to 40 secondary strikes. Depending on the time delay between the strikes, we may see what looks like one long-duration main strike, or a main strike followed by other flashes along the path of the main strike. These conditions are easy to understand if we realize that the secondary strikes can occur while the flash from the main stroke is still visible. Obviously, this would cause a viewer to think that the main-strike flash lasted longer than it actually did. By the same token, the secondary strikes may occur after the flash from the main strike ends, making it appear that the main strike is flickering.
The actual light you see when viewing a lightning strike is the air associated with he strike, exploding. Explosion chain reactions take longer time to travel than actual light or electricity, so we can see the light emited by the fire, actually travelling along the strike path, much in the same way that we familiarly see lightning occur several seconds before actually hearing the explosions, as the sound waves also travel much slower than c.
I am happy.
The last lightning images are from this video. See 2:25...
Electrical information derived from http://www.jimloy.com/physics/electric.htm and http://science.howstuffworks.com/lightning.htm/printable
