These posts make more sense when read in order.
Please click here for the first article in this series to enter the rabbit hole.
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© KarstenLoewenstein, CC-BY-3.0 & GFDL. |
Einstein’s interest in electromagnetism centered on the work of James Clerk Maxwell. In the 1860s Maxwell had come up with the unified theory of electromagnetism by combining magnetism with electricity. One feature of Maxwell’s equations was that they didn’t make sense unless light traveled at a set rate, no matter how fast the light’s source was moving.
Einstein took the constant speed of light and raised it to the level of a law of nature. While pondering the implications of this, Einstein realized that nothing can go faster than the speed of light, which in a vacuum is approximately 671 million miles per hour (1.08 trillion km/h).
Here’s where it starts to get counterintuitive. Since the speed of light remains the same in all frames of reference, if you had a rocket with a headlight and it was traveling at half the speed of light and you turned that light on, you would think that the photons shining from the light would zip away at one and a half times the speed of light, but it doesn’t work that way. Light in a vacuum always travels at the speed of light. That’s its maximum and minimum speed. If you release some photons in a vacuum, they will shoot off as fast as they can, or as slow as they can, depending on how you look at it. Either way, it’s the same thing since light always goes at one speed.
If two remotely controlled racecars collide head on and each are going 100 mph (161 km/h), then the speed of the collusion will be 200 mph (322 km/h)—the vehicles’ speeds combined—but if two beams of light meet—they can’t collide and will pass right through each other because they have no mass—their meeting will be at the speed of light, not the speeds combined. It can’t be faster.
Since the speed of light is constant in all frames of reference, this presents a problem. If you’re sitting in your backyard and you turn on your flashlight, the photons shoot away from you at the speed of light, but if you are inside the Red Queen’s Maserati spaceship traveling at close to the speed of light—which is not really possible—and you turned on a flashlight inside the ship, its light would still move away from you at the speed of light, taking into account the slight reduction in speed because of the atmosphere in the ship. You would expect it to slowly move out of your flashlight, but it doesn’t. The speed of light is a constant, no matter what your frame of reference is. But remember, space and time—or rather, spacetime—are distorted at this speed.
By now you’re probably thinking that this doesn’t make sense and can’t be right. That’s pretty much what the world’s physicists thought when Einstein published his ideas and they worked hard to disprove them, but the experiments sided with Einstein. And they are still being confirmed today.
I said it’s not possible for a ship to travel close to the light speed. This is a consequence of his famous formula E = mc2, which says that energy is equal to mass, when mass is multiplied by the speed of light squared to convert it into the same units as energy. This means that mass (the amount of matter, disregarding volume) and energy are essentially the same thing and equivalent as far as the equations go. So, the faster a ship goes, the more kinetic energy—the energy of its motion—it gains and the more massive it becomes. As you approach the speed of light, your mass would increase towards infinity, preventing you from reaching light speed. If you were to go faster, your mass would become negative, which doesn’t make sense. You’d also go backwards in time. Energy has no mass when it’s in the form of electromagnetic waves, such as light or radio waves which is why they travel at light speed, but without mass you can’t have a spaceship.
Now, the ship’s stationary mass doesn’t change. It’s the energy you put into it to make it go faster that increases. The mass in the E = mc2 equation doesn’t refer to mass like in a rock—it’s the stationary mass, plus kinetic energy acting like extra mass.
As you near the speed of light and your mass approaches infinity, the amount of energy needed to reach full speed also moves towards infinity. In addition, measurements and time shorten as your velocity increases, so as you near light speed, the ship becomes two-dimensional in the direction of travel and time would almost stop. This is a consequence of Einstein’s special theory of relativity and we’ll look at that more closely in a bit. Only massless objects—photons, and possibly zero-mass neutrinos and gravitons (if they exist)—travel at the speed of light. And they don’t have to build up to that speed; they are created at that speed. In a vacuum, that’s the only speed they can go.
For objects with mass, you put in energy to make them go faster. Light doesn’t work that way. If you add energy, or the falling effect of gravity, it increases the frequency of light’s waves. Thus if you have red light and pump in energy, you can shift it to blue or ultraviolet light, or push it to x-rays or gamma rays. But you can’t make it go faster.
Theoretically you can travel farther than the speed of light allows, but you’d have to use a wormhole as a shortcut. There are also hypothetical anti-mass particles called tachyons, which arise from a quantum field with “imaginary mass”, that can go faster than light—and for some viewers, backwards in time—but so far no one knows whether they actually exist.
Some galaxies are moving farther apart faster than the speed of light allows, but this doesn’t violate that law because it’s the universe itself that’s expanding. The galaxies aren’t moving faster than light, the space between them is growing because new space is being created, as we’ll see later.
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Esmail Golshan Mojdehi, CC BY-SA 3.0 (adjusted). |
As a side note, light travels at exactly 299,792,458 meters per second, confirmed to an accuracy of less than 0.01 micron per second (0.0000004 inches, which is the same size as a water molecule). One single-watt light bulb can produce a billion billion photons per second and they will take off across the universe as long as they don’t hit anything. If you turn on your flashlight and point it at the moon, if at least one photon makes it through the atmosphere and beyond without being deflected, it will reach the moon in 1.3 seconds.
To put this in perspective, if you could drive to the moon (238,855 miles), at 60 miles it would take you 166 days to get there, while light does it in 1.3 seconds. And if you could fly at the speed of light, you could go around the earth’s equator almost eight times in a second. Point your flashlight at the sun and your photon would arrive in 8.3 minutes. To Alpha Centauri—a triple star system that are some of our nearest stars, beside the sun—would take 4.3 years. Toward the Andromeda Galaxy, it will take 2.5 million years for your photon to reach its destination.
Since nothing is faster than light, spaceships can’t dodge light weapons, such as high-energy lasers or photon torpedoes, as they do in movies. They would hit you before you knew they were fired. It’s the same with dodging bullets. It can’t be done. The average bullet travels at 2,493 feet per second, so it would pass through you before your brain could register the muzzle flash, let alone respond to it.
I'll post more in this series when I can. There's a lot more to cover.
In the next posts we'll go deeper down the rabbit hole by continuing to explore Einstein's revelations, quantum physics, the multiverses, and other interesting topics affecting reality, such as whether the universe is a simulation and the peculiar nature of time.
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