What is it about velocity (of light) that affects time?

Question

Please don't refer me to a book. For one reason, a lot of scientific texts don't explain things very well. I think that is something that is changing with time. . . . (getting worse, have you noticed how a lot of older science books were written so much better?).

Sorry, but I doubt anyone will put it in laymans terms rather than an equation.

I do a lot with maths but this field confuses many people. My main area of programming is maths and science. (It hurts when someone says "no maths involved"!)

I see that if travelling at or faster than the speed of light, things would seem to stop or go backwards if the optics were made steady (so objects didn't get smaller with distance), but that wouldn't stop a time traveller ageing, or returning to people without increased or decreased age in comparison to them.

It sounds as if at the speed of light a body is pure energy, so making this speed impossible to travel at, and time does not exist within energy. That's the bit of what's been said that I can picture. I'd also like to know if the concept of absolute zero temperature is related or has the similarity of timelessness.

Answer 1

As one approaches the speed of light, time slows down.

Light travels at 186,282mi/sec.
The fastest a man has traveled is only a fraction of that, ~5mi/sec. (on the way to the moon and back)

If you could travel at the speed of light, time would stop.
Most scientists believe that it is not possible for something other than electromagnetic radiation to travel at the speed of light. Most scientists also believe that it is not possible for anything to travel faster than the speed of light.

Answer 2

For a long time, scientists believed that time was constant, never changing. They also believed that light travelled through an "ether," just like sound travels through air or another medium, or waves in the sea travel through the water.

The Michaelson-Morely experiment disproved all that. These scientists set up mirror devices on nearby mountains to test the speed of light. The theory was this: if light travelled in a "ether" medium, it would be slower when travelling "upstream" and faster "downstream."

In other words: imagine you are in a train and you throw a ball at 20 mph. To you, the ball is moving at 20 mph. To a person watching the train go by, it depends on whcih direction you threw the ball. If you throw in the same direction of the train, then you add the speed of the train. If you throw in the reverse direction, subtract the speed of the train.

Another example: a river runs at 20 mph. If a salmon swims upstream at 21 mph, the salmon moves upstream at 1 mph. If the salmon lazily swims downstream at 3 mph, the salmon's speed, relative to the shore, is 24 mph.

These are examples of things that travel in a medium.

Back to light: By taking measurements of the speed of light at different times, when the Earth was rotating in different directions (as compared to the experiment), orbiting in different directions around the Sun, etc., IT MADE NO DIFFERENCE.

The conclusion was this: light has no reference medium, and its speed is universally constant, no matter how you look at it.

The problem with this it the following: how could it be that the speed of light is the same all the time? If you shine light in the same direction as the train, why doesnt the speed equal the speed of light PLUS the speed of the train? Why is the speed of the light measured the same on the train as off the train?

The answer is most strange, but has turned out to be true, and has even been proven experimentally.

Remember that speed is a function of distance and time (e.g. miles per hour). If the speed of light is constant, then it is time itself that must be different. Experiments have shown this to be true. The higher speed traveller experiences slower time, relative to the bystander.

Time changes, not the speed of light.

Answer 3

Thats a very good question. I suppose one answer would be that we don't know with any real certainty. Time just elapses whatever is happening. But what you are referring to is the Lorentz transformations, particularly the result known as time dilation.

One thing that we need to take into account is the assumptions made when this postulate was formulated. One of the assumptions made is that all Maxwell's relations remain invariant. The thing is Maxwell's relations were derived assuming the medium to be stationary, Not a moving medium like the theory of relativity suggests. This is an example of where caution needs to be taken in the validity of theories.

Personally, the whole time dilation and length contraction do seem a bit far fetched. I know of a result that shows time dilation to be right but length contraction. Hmm!

So to answer your question, it depends on your perspective. We just don't really know!

Answer 4

This was how it was explained to me. I may oversimplify it but it worked for me. I may be wrong in some concepts and would welcome any corrections.

Einstein theorized that space, time, and all matter exist in a universe that moves. Let's use a freeway to illustrate.

Imagine yourself standing at the edge of the freeway with all the cars travelling at the same speed in one direction. From where you stand, you see the cars travelling fast.

Let's call this freeway the time-space continuum. What speed are the cars travelling? This will be the speed in which the universe exists. Einstein theorized that this would be the speed of light.

Now lets say that you got into your car and started to drive then the freeway. As you increase your speed, the cars that are passing do not seem to be travelling as fast anymore. They may even seem to be slowing down. But the cars are not slowing down, you are just speeding up. For another person standing still beside the freeway, he would see athe other cars travelling at the same high speed as you have seen when you were standing still.

So your view of speed of the cars is different from the third person's view of the speed of the cars because of the relative positions. You are travelling in a car, while the third person is standing still.

(Hence the Einstein's theory of relativity)

Now, as you accelerate more and match the speed of the other cars exactly, the cars seem to be standing still. That's because you are travelling at the same speed, the speed of light. For the third person's relative position on the side of the freeway, you and all the cars are still zooming away at the same speed.

So for you in the car, time has stopped. But for the third person, time still continues on.

As you accelerate more, exceeding the speed of light, you begin passing the cars that are still at the speed of light. And as you know, when you pass a slower car, the car seems to be moving backward from your relative position inside your car. Same thing as you pass a truck running at 55mph on the freeway by travelling in a car at 65mph. You see the truck move from the front of you to the back of you. So as you exceed the speed of light, time goes backwards.

Since space, matter and time (represented by the speed of light) are correlated, Einstein theorized that some form of energy is used to bind all this together. And this energy can be released by disrupting it. Einstein measured this energy through his famous equation, E = mc(squared) where m is the mass and c is the constant (speed of light). This equation also simply means that you'll need lots of energy to make something (mass) travel at the speed of light.

Answer 5

first things first, the speed of light is not constant, it is only constant when travelling through free space. (a vacuum). it isn't so much the velocity of light which affects time, simply the fact that it is the fastest thing there is, it is impossible for an object with any tangible mass to travel at the speed of light (even in theory) as the energy requirements would be near infinite. the concept of time changing as you approach the speed of light revolves around the fact that the speed of light is constant to the observer in a given medium. this means that as you approach the speed of light space and time must adjust in order for the speed of light to remain constant from your frame of reference. It is not only time that will warp but also space.

Answer 6

Some good answers here, I'll make my more understandable description of time dilation, but I think you've been given some good answers.

To understand how how the velocity effects time experience (time dilation) you have to understand some important aspects of light.
(please exempt meduim different meduims and anything relating to earth).

(Light is constant through space), light can't slow down nor speed up. if I travelled at 50mph in a car and shone a light ahead, (unlike a ball) those photons of light won't gain an increase in velocity, just as shining the light behind the car won't lose velocity.

(Light is the maximum speed limit within the universe) Matter, information and everything within the void of the universe cannot exceed the speed of light. It is due to mass and energy relationship ( E=mc2), but all you need to know us than nothing can exceed light speed withn the Universe.

With these two relationships of light I we can describe to you how both of these laws effect time for the observor in the ship and time dilation.

If an astronaut travelled in a space ship at a relativistic (impossible) velocity od 99.9999% of light speed, taking the constancy of light, everything within the space ship and the hand of the clock cannot gain any extra velocity and thus travel over to the speed limit. Taking the speed limit into consideration, if I attempt to throw or shine my torch ahead of me that torch will appear to move slowly. This is becuase (light travels at the same speed as the torch shone) + (the speed of the spaceship is running behind the speed limit of light). Near complete time dilation, attempted to throw or move my hand would be impossible becuase my hand would be violating the e=mc2 and thus travelling faster than light speed. Travelling behind this complete forzen time dilation state would make the observor in the ship appear to slow down (unless the photons in his brain slows his perception). The hands on the clock would appear to slow down becuase after all it is made of matter just like the astronaut.
This is a different alternative description regarding the 'twin paradox'.
As for the the observor, I have described the observor in the ship, and not the observor relative to the ship!

Following my aspieness. ;)

Answer 7

Here is an excellent, easy to understand tutorial on relativity and time dilation:
http://www.phys.unsw.edu.au/einsteinlight/

Start with Galileo and work your way through. The tutorial only takes about 10 minutes, but there also a lot of additional information available.

This Nova page might be helpful, too:
http://www.pbs.org/wgbh/nova/einstein/hotsciencetwin/

And another:
http://www.einstein-online.info/en/elementary/specialRT/index.html

No math knowledge is needed for any of the above links.

Answer 8

think of it like this.if we as humans all went about our daily business at the speed of light we would not be aware of doing it.it would be normal,as is now at our slow speed. light travels at 186,000 miles per second.the problem only lies in the mind of man because he knows of nothing faster yet.if i phone halfway round the world in a sec its much faster than light.

Answer 9

There is of necessity a basis of physical time, meaning there must exist a reason for time existing, and there must be a singular factor common to all mass and energy. It is this basis of our existence I would like to call your attention to.

There exists a trilogy in physics that describes our universe in its most basic manner. The trilogy is: E = mc2, m = E/c2, and c2 = E/m. The last concept is that for a field of physical time or that of a field of gravity. Notice that it comes into existence because of a mass to energy relationship. This value is also found in the "E" and "m" values and, if you look at them carefully, this value becomes the basis of each of these also.

It is this particular value that is what you seek. The value of "c" describes our physical reality as to its existence - our entire universe is solely composed of this value, as are each of us. According this this value, it is how quickly the present folds into becoming the past, it shows the duration of our existence in physical value (how long present time exists before it moves into becoming the past). It describes our limitation of existence as being that of the speed of light, "c". Other universes could have a "c" value of a slightly different speed (how quickly the present becomes the past) and they could exist, spatially, within our own, but they would not be recognized due to existing in another time.

"light", or electromagnetic energy, is what forms phycal time. Now we need to see why the acceleration of a mass, which is composed of electromagnetic energy, has differing time values according to its speed.

There is a short, easy to understand writing at http://360.yahoo.com/noddarc entitled "The Problem and Repair of Relativity" that gives a further basis of physical time. I think, though, what you are interested in is the "Twin Paradox".

Robin and Ralph and brother and sister. They are each 30 years of age. Ralph has devised a manner by which he is able to move through space at the speed of light. He leaves earth to begin a ten year journey to a nearby star where there is a planet that is made up of gold and platinum. He has with him a large cup of hot coffee and two doghnuts. For ten years he travels through space and then arrives at the planet he sought. Landing, he takes a sip of his yet hot coffee and eats a fresh doughnut.

In that he can only carry 20 tons of gold and platinum, it takes but five minutes for him to have robots load up his ship, and then he immediately heads back home at the speed of light. Upon arrival his coffee is still hot - after a period of 20 years, and the second doghnut still fresh. Not only that, but he finds his sister 20 years older and he has aged but five minutes. How is this possible?

When mass accelerates toward the speed of light, the frequency of the mass itself changes. There is an increase of frequency density in direction of travel, that is at the expense of energy/mass at right angles to direction of travel. When a mass reaches the speed of light, the mass converts into electromagnetic radiation and is no longer mass (it converts into becoming one dimensional only). It is able to be seen that the concept of a mass moving at the speed of light and then returning to becoming a mass again is impossible. Once a mass reaches the speed of light it becomes the clock of the universe by which all other entities having less speed are timed by. There exists no such thing as time when moving at the speed of light, for time is a condition that exists only in relation to mass.

When we move, we move in multiple dimensions. When a mass nears the speed of light, one dimension increases and the other two decrease proportionately. In order for the aging process to occur it requires all three dimensions to be affected. If there is but a single dimension, physical time does not exist to the other two dimensions. The proportion of energy existing at right angles to direction of travel determines dimensional time to us.