- 3659 - EINSTEIN’S - simple equation big meaning? Einstein’s famous equation E = mc^2 means that energy is equal to mass times the speed of light squared. It also means that any amount of mass is equal to energy divided by the speed of light squared. This little equation is central to the theory of special relativity, and also explains how nuclear fusion and fission can generate energy.
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--------------------- 3659 - EINSTEIN’S - simple equation big meaning?
- In a famous paper written in 1905, Albert Einstein discovered an equality between mass and energy. He found that the conservation of mass is the same as the conservation of energy, and vice versa. These insights were a part of his development of the theory of special relativity, which describes the relativity of motion, particularly at near light speed.
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- One way to understand what E= mc^2 means is to think about the speed of light as simply a number that can be expressed in terms of any arbitrary set of units. If you define your units, what a "meter" and a "second" are, you can say that the speed of light is around 300 million meters per second (or 670 million miles per hour).
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- A jet airliner cruises at a snail's pace of 0.000001, or 0.0001% the speed of light. Two of the fastest human-made objects, the Helios probes, zoomed around the solar system at a 0.00025 times the speed of light. Way short of light speed.
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- Once the speed of light is defined as equal to “1“, we can take a different look at the most famous equation in physics: E = mc^2 having different units of measure. “E” is for energy, “m” is for mass and “c” is the constant speed of light. But in this newly defined unit system (called geometrized units), “c” equals 1, and that famous equation boils down to its essence:
-------------------- E = m. Energy = mass.
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-------------------- Energy is mass. Mass is energy.
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- They are equivalent. They are the same thing.
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- Light, photons, or packets of light, don't have any mass, but they have lots of energy.
Photons have momentum, which is how things like “light sails” (also called solar sails) get the ability they need to glide around the solar system: Their propulsion comes from the sun's radiation pressure. And momentum has energy. But where's the momentum in
E = m?
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- The confusion comes from the “m” used in E = m. People normally think of mass as something concrete and simple. Hold a rock; it has mass. Throw it, and it has mass and momentum. But that's not the “m” in E = m. Instead, when Einstein wrote down that equation, he meant something different, usually referred to as “relativistic mass“.
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- According to the understanding of special relativity, it's impossible to move at the speed of light, because the faster something goes, the more mass it has. To get to the speed of light, something has to have “infinite mass“, so it would be impossible to push!
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- A fundamental aspect of the universe is that there's a universal speed limit: the same speed light goes. No matter what, no one can crack that speed.
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- So, what's going on? The answer is energy. You still have the same old rest mass you always had. But you're going really, really fast. And that speed has an energy associated with it, kinetic energy. So it's like all that kinetic energy is acting like extra mass; any way you count it, you get harder to push because of that fundamental speed limit.
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- When we break up “m” into its different parts, we get this equation, where p is momentum:
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-------------------------- E^2 = m^2 + p^2
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Or, bringing back c, the speed of light, we get this:
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------------------------- E^2 = m^2 * c^4 + p^2 * c^2
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- That's why photons don't have mass, but, they do have “momentum“, so they still get energy. One way to think about this relationship is to consider that stationary objects are still moving in time. A rock, for example, may be perfectly still. But it's still moving into the future, at the rate of 1 second per second. The same is true for every other object in the universe.
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- While people are familiar with kinetic energy, the energy of motion, they usually define that motion only in terms of movement through space. But relativity considers motion through the entire four-dimensional fabric of space-time. Something that is perfectly still in space is still moving through time, so we can associate a kinetic energy with that motion.
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- This is what leads to E = mc^2: the energy of a stationary in space, an object that is nonetheless moving through time.
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- A hot cup of coffee literally weighs more than a cold cup. A fast-moving spaceship literally weighs more than a slow one. An atomic nucleus is a compact, bundled-up ball of energy, and sometimes we can tease some of that energy out for a big boom: a nuclear reaction. So now you know.
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August 21, 2022 EINSTEIN’S - simple equation big meaning? 3657
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