Can anyone explain the theory of relativity to me?

Answer 1

Without going into a lot scientific mumbo jumbo, Einstein's theory of relativity states that nothing in the universe is 'absolute'. Your perception of anything (e.g. size, speed, position, and even passage of time) is relative to how you are moving. In short, your measurements for size, speed, position and time, will be different from another person who is travelling at a different speed to you. The differences are neglible at low speeds but can vary dramatically when dealing with speeds approaching the speed of light.
The speed at which we see light moving is the one thing which is the same for everybody. No matter how fast you are moving (relative to someone else) you will record the same speed of light - roughly 186,000 mile sper second.

Answer 2

For objects traveling near light speed, however, the theory of relativity states that objects will move slower and shorten in length from the point of view of an observer on Earth. Einstein also derived the famous equation, E = mc2, which reveals the equivalence of mass and energy.

Answer 3

OK, this is a bit long, but it's a fairly straightforward explanation that I've given people before:

There are two theories of relativity, general and special.

General Relativity: With this Einstein theorised that space and time together formed a 4th dimension, known as space time. Space time can be warped, and it's this warping that results in gravity. Imagine two people holding a rubber sheet (representing space-time) pulled taut between them. Then a third person comes along with a cannon ball and places it in the middle. The sheet will remain taut, but will dip slightly in the place where the ball rests. If we then roll another smaller ball towards the cannon ball, it will fall into the dip. This is, in essence, how gravity works. It is not really a kind of magnetism, as most people assume, it is actually a direct effect of the warping of space-time by very large objects of mass like planets.

And that, probably, is as far as any non-physicists can ever really get towards understanding that aspect of relativity.

Then of course, there's Special Relativity - and that deals with the very strange way that light travels within the universe, and what it means to our understanding of time.

Before Einstein it was assumed that time ticked on for all of us at the same rate and speed regardless of our circumstances. Didn't matter where you were or how fast you were travelling, time was time was time. Two synchronised watches would always stay synchronised. But relativity shows that, actually, that's not the case. It entirely depends on how fast you are travelling but ONLY relative to an observer.

Imagine that you're in a car that's travelling at 30mph, and I am standing at the roadside watching you approach. If you throw a ball out of the window at me as you go past at, say, 10mph then we would have a different perspective on how fast that ball was actually travelling. To you, in the car, the ball is travelling at 10mph - but to me, it's 40mph. You are already travelling at 30mph, so you would measure the velocity of the ball at 10mph, but I would have to take into account the speed of the car and add it onto the speed of the ball to get the true velocity.

This is quite simple and straightforward. But where it gets complicated is when we understand that the light that is travelling from the car's headlamps does not behave that way. It is entirely different. From both our perspectives light travels at exactly the same speed, without variation. Your car could be travelling at 100,000 mph, but light would still flow on from it at the same rate - you do not add on the car's speed to get the true velocity as you would when trying to judge the balls true speed. Regardless of your movement, or lack of it, the speed of light remains constant. And light travelling towards me comes at the same speed whether it's from a car travelling at 30mph, or a rocket at 100,000mph.

Einstein then theorised that if the speed of light does not change, then something else must. We know that in order to work out the speed of anything we need to divide distance covered by time taken. So it must be distance and time that change. And they do - but, again, only relative to an observer.

The faster an object travels the more time slows down, and the more the object will shrink - but ONLY from the perspective of any observer, and not from the perspective of the object itself.

Best way to envisage this is the train analogy. I am on a train platform, and you are on a train travelling at a velocity close to the speed of light. As you zoom past me, I will see that the train appears much shorter than it did at the beginning of the journey, and if I look through the windows I will observe that time has slowed down for you - your watch will be running slower, your movements will appear sluggish, and your voice, if I could hear it, would sound slurred.

But, to you, none of these effects would be evident. It's not just that you don't notice, but from your perspective, there's nothing to notice. If you were to look out the window at me it would be my time that had slowed, my watch that was running slower.

In essence, it's all relative.

I've gone on a bit, I know, but I hope I've helped.

Answer 4

Everything around us is relative to our own perceptions. If I am at work doing a boring job, 1 hour seems like 5. But when I'm with my man having fun, 5 hours seem like 1. It's all in how we perceive life around us.

Answer 5

E=mc2

Answer 6

In a nutshell:
Every action has an equal and opposite reaction.

Answer 7

Yeah it's all relative!

Answer 8

General Relativity

Einstein's 1916 paper
on General Relativity




In 1916 Einstein expanded his Special Theory to include the effect of gravitation on the shape of space and the flow of time.

This theory, referred to as the General Theory of Relativity, proposed that matter causes space to curve.
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Embedding Diagrams
Picture a bowling ball on a stretched rubber sheet.


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The large ball will cause a deformation in the sheet's surface. A baseball dropped onto the sheet will roll toward the bowling ball. Einstein theorized that smaller masses travel toward larger masses not because they are "attracted" by a mysterious force, but because the smaller objects travel through space that is warped by the larger object. Physicists illustrate this idea using embedding diagrams.

Contrary to appearances, an embedding diagram does not depict the three-dimensional "space" of our everyday experience. Rather it shows how a 2D slice through familiar 3D space is curved downwards when embedded in flattened hyperspace. We cannot fully envision this hyperspace; it contains seven dimensions, including one for time! Flattening it to 3D allows us to represent the curvature. Embedding diagrams can help us visualize the implications of Einstein's General Theory of Relativity.


The Flow of Spacetime
Another way of thinking of the curvature of spacetime was elegantly described by Hans von Baeyer. In a prize-winning essay he conceives of spacetime as an invisible stream flowing ever onward, bending in response to objects in it s path, carrying everything in the universe along its twists and turns.


This is a basic postulate of the Theory of General Relativity. It states that a uniform gravitational field (like that near the Earth) is equivalent to a uniform acceleration.

What this means, in effect, is that a person cannot tell the difference between (a) standing on the Earth, feeling the effects of gravity as a downward pull and (b) standing in a very smooth elevator that is accelerating upwards at just the right rate of exactly 32 feet per second squared.
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In both cases, a person would feel the same downward pull of gravity. Einstein asserted that these effects were actually the same. A far cry from Newton's view of gravity as a force acting at a distance!

Gravitational Time Dilation
Einstein's Special Theory of Relativity predicted that time does not flow at a fixed rate: moving clocks appear to tick more slowly relative to their stationary counterparts. But this effect only becomes really significant at very high velocities that app roach the speed of light.
When "generalized" to include gravitation, the equations of relativity predict that gravity, or the curvature of spacetime by matter, not only stretches or shrinks distances (depending on their direction with respect to the gravitational field) but also w ill appear to slow down or "dilate" the flow of time.

In most circumstances in the universe, such time dilation is miniscule, but it can become very significant when spacetime is curved by a massive object such as a black hole. For example, an observer far from a black hole would observe time passing extremely slowly for an astronaut falling through the hole's boundary. In fact, the distant observer would never see the hapless victim actually fall in. His or her time, as measured by the observer, would appear to stand still. The slowing of time near a very simple black hole has been simulated on supercomputers at NCSA and visualized in a computer-generated animation.


Grappling With Relativity
In the decade after its publication in 1916, Einstein's Theory of General Relativity led to a burst of experimental activity in which many of its predictions were vindicated. These predictions were encapsulated in a series of field equations that laid the foundation for all subsequent research into relativity and partly for modern cosmology as well.

The Math Behind Einstein's Vision
The mathematics behind the Einstein Field Equations not only presented a formidable challenge to solve, but also led to seemingly bizarre consequences, particularly those of black holes and gravitatio nal waves. At the time they were postulated, both were dismissed by many experts as mathematical aberrations. It remains to be seen whether either truly exist.

Answer 9

Your best bet is to pick up a basic book about it.