How Fast Do Network Packets Really Travel?

The speed of light is a universal constant, denoted by 'c', and is equal to 300,000 kilometres per second or 186,000 miles per second. However, the speed of light is dependent on the medium through which it is travelling. In a vacuum, light travels at 'c', but when travelling through glass, for example, light moves at about 60% of its maximum speed.

The internet relies on light to transmit data, and so the speed of the internet is dependent on the speed of light. In principle, the internet should operate at the speed of light, but in reality, it is much slower. This is due to the chaotic nature of the network of underground fibre optic cables that the internet relies on, as well as the fact that light moves slower through glass.

There are ways to speed up the internet, such as using microwave radio transmission towers to allow internet signals to travel in a straight line through the air.

Light packets can travel at the speed of light, but they don't always

The speed of light in a vacuum is a universal constant, denoted by the symbol 'c', and is more than 670 million miles per hour. However, this doesn't mean that light always travels at this speed. Light moves through glass at about 60% of its maximum speed in a vacuum.

Light packets, or photons, are the smallest discrete amount of electromagnetic radiation and are massless. They are both a wave and a particle, displaying the properties of both.

When it comes to the internet, the speed of light is the theoretical maximum speed for data transfer. However, in reality, internet data moves 37 to 100 times slower than the speed of light due to factors such as network latency and the properties of the medium through which the light travels.

The network of underground fibre optic cables that the internet relies on is highly chaotic. It zig-zags beneath highways and railroad tracks and often sends signals in the wrong direction. Additionally, fibre optic cables are made of glass, which slows down the speed of light significantly.

Despite these factors, there are still ways to optimise data transfer speeds. For example, a national network of microwave radio transmission towers could allow internet signals to travel in a straight line through the air, speeding up the internet. This idea has already been successfully tested on a limited scale, such as between stock exchanges in Chicago and New Jersey, to reduce latency for high-frequency trading transactions.

In conclusion, while light packets can theoretically travel at the speed of light, various factors, such as the medium and infrastructure, can slow them down. However, ongoing research and innovations aim to minimise these speed constraints and bring us closer to achieving internet speeds at the speed of light.

Light packets can be made to travel at the speed of a jet aircraft

By bundling light waves into special packets, physicists have proposed a stable way to slow light signals to one-millionth of the speed limit, which is about as fast as a jet aircraft. Light has been made to go slower than this, and even to stand still. However, most light packets will lose their shape when their speed is decreased, which is a problem for their application in the telecommunication industry.

The new packets, however, belong to a type of wave pattern called a soliton, which has a robust shape that does not easily decay. Solitons were discovered in the 1800s as water waves that propagate without losing their height for miles and miles. Optical solitons are light waves that travel close to the speed of light, but they can be made to travel much slower, giving them more applicability in data transfer applications.

In fibre optic cables, the light travels at around 60% of the speed of light in a vacuum, so around 200,000 km/s. This is roughly the same for normal network cables. WiFi signals travel in the air, so their speed is almost exactly the same as the speed of light in a vacuum, which is 300,000 km/s.

The speed of light is an incredible 299,792,458 meters per second. At that speed, you could circle the Earth more than seven times in one second, and humans would finally be able to explore outside our solar system. In 1947, humans first surpassed the speed of sound, paving the way for the commercial Concorde jet and other supersonic aircraft.

Based on our current understanding of physics and the limits of the natural world, it is not possible to travel at the speed of light. According to Albert Einstein's theory of special relativity, summarised by the famous equation E=mc^2, the speed of light is a cosmic speed limit that cannot be surpassed. So, light-speed travel and faster-than-light travel are physical impossibilities, especially for anything with mass, such as spacecraft and humans.

Even for very tiny things, like subatomic particles, the amount of energy (E) needed to near the speed of light poses a significant challenge to the feasibility of almost light-speed space travel. The Large Hadron Collider (LHC), the largest and highest-energy particle accelerator on Earth, has boosted protons (particles within atoms) as close to the speed of light as we can get. However, even a minuscule proton would require near-infinite energy to actually reach the speed of light, and humans haven't figured out how to generate near-infinite energy yet.

In addition, during the aftermath of a neutron star merger, a jet of material propelled from a disk surrounding a black hole can appear to be travelling four times the speed of light. This phenomenon is known as superluminal motion and occurs when the jet travels at nearly the speed of light and at a small angle relative to our line of sight. Since the jet is moving at nearly the speed of light, when a particle within the jet emits a bit of light, the particle doesn't fall far behind the bit of light it emitted. When a long time passes and the particle emits a second bit of light, it will do so close to the first one, and when the light reaches us, the particle will appear to have been moving faster than light.

Light packets can be made to stand still

In 2001, two teams of researchers from Harvard University and the Rowland Institute for Science in Cambridge, Massachusetts, and the Harvard-Smithsonian Center for Astrophysics, also in Cambridge, independently discovered a way to make light stand still.

The Harvard team, led by Lene Vestergaard Hau, used a tiny, cigar-shaped cloud of ultracold sodium gas in the middle of a vacuum chamber. A laser beam, known as the coupling beam, was fired at the gas cloud, illuminating it and mixing with the sodium atoms. Then, a short laser pulse was fired into the gas cloud perpendicular to the original coupling beam. The laser pulse was completely absorbed into the gas cloud, which was only as wide as a single thread. If the coupling beam hadn't been in place, the laser pulse would have dimmed and eventually diffused through the gas. But the two beams interacted, and the laser pulse simply slowed down rather than disappearing. With the pulse passing through the gas cloud, the scientists switched off the coupling beam. The laser pulse stopped and seemed to disappear. But when they switched the coupling beam back on a millisecond later, the laser pulse reappeared and continued as if nothing had happened.

The team from the Harvard-Smithsonian Center for Astrophysics, led by Ronald Walsworth and Mikhail Lukin, used lasers and clouds of gas to stop and then start a pulse of light.

In 2004, Lu Deng of the National Institute of Standards and Technology and his colleague Ying Wu devised a way to make optical solitons (a type of wave pattern with a robust shape that does not easily decay) that travel much slower, giving them more applicability in data transfer applications. Optical solitons are generally light waves that travel close to the speed of light.

In 2015, a team of scientists at the Vienna University of Technology demonstrated that light could be slowed down to a speed of 180 km/h and even brought to a complete stop. They coupled atoms to glass fibres, creating an exceedingly strong interaction between light and matter. The team used an additional control laser in their experiment, which coupled the high-energy state to a third atomic state. The interplay between these three quantum states prevents the photon from being randomly emitted and instead transfers the photon's quantum information to an ensemble of atoms in a controlled way, where it can be stored for some time. After two microseconds, the control laser was used to prompt the atoms to emit the light back into the glass fibre. The properties of the photon stay exactly the same, an important prerequisite for quantum communication.

Light packets can be made to travel at different speeds through different mediums

The speed of light is often discussed in a vacuum, where it travels at its maximum speed of approximately 299,792 kilometres per second (km/s), or about 300,000 km/s. This is the "universal constant" for the speed of light, denoted by the symbol c. However, light travels through various substances on Earth, and its speed varies depending on the medium.

In air, the speed of light is slightly reduced because air contains particles that slow light down, though not by much. In air, the speed of light is approximately 299,705 km/s—still incredibly fast and very close to the speed in a vacuum. The refractive index of air is roughly 1.0003, meaning light slows down just a bit.

When light travels through any material, whether it’s water, glass, or any other substance, it slows down. The reduction in speed depends on the refractive index of the medium. The refractive index (n) is a measure of how much the medium slows down light, calculated as:

N = c / v

Where:

• N is the refractive index
• C is the speed of light in a vacuum
• V is the speed of light in the given medium

The higher the refractive index, the more light slows down in that medium. For example, light travels much slower in glass, with speeds ranging from 158,000 to 200,000 km/s. In distilled water, the speed of light slows down to about 225,000 km/s. This is significantly slower than in a vacuum due to the refractive properties of water molecules.

Recently, optical solitons—a type of wave pattern with a robust shape that does not easily decay—have been used to slow down light. Optical solitons are generally light waves that travel close to the speed of light. However, they can be modified to travel much slower, giving them more applicability in data transfer applications.

Light packets can be used for data transfer applications

Light packets, or optical solitons, are a stable way to slow light signals to one-millionth of the speed of light, which is about as fast as a jet aircraft. Optical solitons are a type of wave pattern that has a robust shape that does not easily decay.

The current method of data transfer involves converting an optical signal to an electrical signal, which is then stored in a buffer while the address is read. Once the destination is known, the signal is converted back to optical and sent on its way. However, these conversions waste resources.

Light packets can be used to simply slow down the main signal while the address is read, instead of converting it to an electrical signal. This can be done in tiny cells filled with gas atoms, where a laser is shone into the cell to tune the speed of light. However, slowing down a wave can cause it to break up and lose the signal.

Optical solitons are a solution to this problem, as they do not easily decay. They are light waves that travel close to the speed of light, but can be made to travel much slower, giving them more applicability in data transfer applications.

Li-Fi is a wireless communication technology that utilizes light to transmit data. It is capable of transmitting data at high speeds over the visible light, ultraviolet, and infrared spectrums. Li-Fi is similar to Wi-Fi in terms of its end user, but differs in that it uses the modulation of light intensity to transmit data, while Wi-Fi uses radio frequency.

Li-Fi has a number of potential applications, including:

• Home and building automation
• Underwater application
• Airborne environments, such as commercial passenger aircraft
• Medical facilities
• Vehicles
• Industrial automation
• Free-space optical communication
• Indoor positioning systems

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