LAB Physics - file 02
Traveling around the World within a blink
Can you imagine the Universe without Light? Light is fundamental, energetic, and the symbol of hope, but mysterious. And it's always the most spotlighted superstar on the stage of physics in history.
In light of physics, light is, in short, a Quantum phenomenon of energy. It displays Wave-Particle Duality, which means both wave-like and particle-like properties.
Light behaves as an Electromagnetic Wave. It explains phenomena of the wave, such as Diffraction and Interference. And light can travel through a vacuum without a medium as a form of energy.
At the same time, light is composed of discrete, massless particles of energy called Photons. This explains interactions with matter, such as the Photoelectric Effect.
Light is said to be the fastest in the Universe, in common sense. In fact, how fast in the world does light travel?
Light runs 7.5 times around the Earth in 1 second!
In fact, light can indeed circle the Earth about 7.5 times in a single second. So let's break it down and calculate it!
At first, to understand why this happens, let's look at two specific numbers: the speed of light and the size of our planet.
Speed of Light (c):
Earth’s Circumference:
In this connection, the meter was initially defined in the 1790s by the French National Assembly as 1/10,000,000 of the distance from the North Pole to the Equator, measured along the Meridian Line running through Paris. So rationally, as the distance from the North Pole to the Equator (1/4 of the circumference of the Earth) equals (approximately) 10,000,000 m = 10,000 km, the Earth’s circumference should be 4 times that, so 40,000km!
Let's get back to the calculation…
1. How many times does light go around the Earth?
2. And how long does one single lap take?
To know how long it takes for a beam of light to complete one full lap around the Earth, it's simple!
This means light circles the Earth in about 134 milliseconds. This is literally faster than a blink of your eye, as the blink of a human eye usually takes around 300 - 400 milliseconds (0.3 - 0.4 seconds)!
Traveling to the Moon and the Sun
Light travels in an instant everywhere on the Earth. Then, how about in the cosmic scale? There are well-known figures that had been already calculated in Astronomy. So let's see the travel of light to our neighbors!
●The Moon
Light reaches our only satellite, the Moon, in about 1.3 seconds in a straight line.
For comparison, the Space Shuttle's maximum speed is around 28,000 km/h(17,500 mph) in orbit, allowing it to circle Earth every 90 minutes. So theoretically, if the Space Shuttle fly from the surface of the Earth to the Moon with a constant maximum speed in a straight line (388,400km);
So the Space Shuttle would take around 13.7 hours (about 13 hours 44 minutes).
But in reality, our current space rocket must overcome Earth's gravity, and moreover, requires complex orbital mechanics and maneuvers to navigate to the Moon, taking roughly 3 days to the Moon.
●The Sun
Likewise, light can reach our father, the Sun, in about 8 minutes and 20 seconds. So conversely, you always see the Sun beam that has actually departed from the Sun 8 minutes 20 seconds ago ever.
But in reality…
Theoretically, we could calculate the speed of light above, which can circle the Earth 7.5 times. However, there are some restrictions that affect the speed of light in the environment in reality…
1. The Path of Light
In reality, light doesn't travel round along the Earth's surface like going on a circular orbit, but in straight lines regardless of the Earth's gravity. So in order to travel around the Earth, light must need to be reflected by a series of mirrors, or guided through a Fiber-Optic Cable.
2. Fiber Optics
Then, if we send data through fiber-optic cables like the internet, light actually travels about 30% slower. Because light needs to pass through dense glass molecules rather than a vacuum. Even as much slower, NO matter. Light can still reach everywhere on the Earth in a fraction of a second through fiber-optic cables!
Speed comparisons!
Let's compare the speed of human technologies to the speed of light so that we can intuitively see the speed of light!
Before proceeding, let's convert the speed of light (c = approx. 300,000 km/s) into km/h, which is a more familiar unit in our everyday life. It's not complicated at all to calculate it.
Just let it (c) multiply by 3,600! Because 1 hour consists of 60 minutes, and 1 minute consists of 60 seconds in turn (60 X 60 = 3,600).
●Commercial airliner (920 km/h)
1,080,000,000 km/h / 920 km/h = approx. 1,173,913
 |
| NASA Parker Solar Probe (source: NASA Science) |
Launched in 2018, Parker Solar Probe bravely advances alone toward the scorching Sun to explore the Sun's outer corona. Despite its only 3-meter small body, it's capable of withstanding extreme heat up to 1,370-1,650°C (2,500-3,000°F) by reflecting intense solar radiation, and has reached extremely close to the Sun, flying through the Sun's outer atmosphere. He made history in December 2024 by coming the closest within 6.1 million kilometers (3.8 million miles. ONLY about 4.4 times the diameter of the Sun!) of the Sun’s surface.
In theory, using the same way of calculation for light above, the NASA Parker Solar Probe can travel a single lap of the equator of the Earth in about 3.5 minutes!
Plus, last but not least, we shouldn't forget to compare the speed of Sound!
●Speed of Sound (1,235 km/h = Mach 1)
Even if…
●Shinkansen bullet train
Even if you took a Shinkansen bullet train from Tokyo to London, about 9,500 km away (of course, the Amphibious version of Shinkansen), it would take you about 30 hours of non-stop travel in the shortest course.
But light could make that same trip in 0.03 seconds within a blink (taking about 0.3-0.4 seconds on average)!
●Commercial airplane
Even if you took a flight from New York to Paris, about 5,850 km away, it actually takes about 7 hours and 25 minutes on average.
But light can fly 25 round-trips (51 one-way trips) between the John F. Kennedy International Airport (JFK) and the Paris-Charles de Gaulle Airport (CDG) ONLY in a single second!
Consequently, we need to declare our complete defeat… Actually, in terms of speed, there is nothing humans have made to compare to light on our Earth. Even the NASA Parker Solar Probe, which currently boasts the fastest human-made object ever built, can reach ONLY about 0.06% (6/10,000) of the speed of light…
Having said that, the speed of light is NOT altogether formidable, but varied and slowed down. In the next post, let's examine it together! Stick around!
Light is energy for life, fertility, hope, grace, and still infinite possibility for Human Beings as well as for All living organisms. We, as humanity, have always been attracted to, pursued, and worshipped light for millions of years. Our history has been with light, and also our future will be with light forever as long as the Sun is shining on us.
Further Reading (sponsored by Amazon):
Designed to offer a comprehensive and engaging introduction to intermediate- and upper-level undergraduate physics and engineering students, this “Introduction to Optics”(3rd edition) also allows instructors to select specialized content to suit individual curricular needs and goals!
Table of Contents
“Principles of Optics” is one of the most highly cited and most influential physics books ever published, and one of the classic science books of the 20th century!
Table of Contents
●Grant R. Fowles (2012). Introduction to Modern Optics (Dover Books on Physics). 609 pages. Dover Publications.
This incisive “Introduction to Modern Physics” provides a basic undergraduate-level course in modern optics for students in physics, technology, and engineering!
Table of Contents
The Experiments of Sagnac and of Michelson and Gale to Detect Rotation
