# Time And Other Things

I’ve been troubled by a series of things for awhile, starting with the nature of time. I’ve read that when an object gets faster the amount of time experienced drops. Now is this a constant rate at which it drops or more like a curve? Also, at The Speed Of Light (Or c.) does the amount of time experienced equate to zero? If not, then at what speed should it equate to zero? Or better yet can it?

Any response will suffice. Thanks.

Great topic, Xilivai. Like you, I’m interested in the concept of time and have been reading up on it and special relativity recently. I am especially intrigued by the question of whether or not the arrow of time could be symmetrical, ie. travel both ways. Some seriously mind-blowing stuff (although not really related to your specific OP).

Anyway, most thought experiments on time dilation are illustrated with an inert “observer” and an “astronaut” travelling away from the observer. As I understand it, according to special relativity, here’s how to calculate how time slows for a fast-moving object/astronaut:

For the observer, his/her watch ticks uniformly with one second between ticks.

For the astronaut travelling away from the observer, the time between ticks of clock = 1/β seconds

The β factor = √(1 - square of fraction of c)

So for example:
⋅ where velocity is .99 times the speed of light, 1 tick of the clock would be 7.1 seconds for the astronaut
⋅ where velocity is .9999 times the speed of light, 1 tick would be 70.7 seconds for the astronaut
⋅ where velocity is the speed of light (impossible), 1 tick would be infinity seconds for the astronaut

Not sure if that exactly answers what you are getting at…?

Thank you so much for answering and yes that is somewhat what I’m looking for.

Now to keep things going, do you know why we cannot travel faster than or at c? ( I would like to discuss this matter rather than just look it up on google so please, everyone, don’t tell me to “google” it. Thanks.")

Also, here is a few other questions.

When you say symmetrical, is the question whether or not it is possible to travel backwards in time rather than just forward?

I do not understand this fully, mainly the “square of fraction of c” part. What exactly does this mean?

Edit: Nevermind, I just got it. (Man I’m feelin’ kinda’ slow today.)

I realized on a graph it would appear to increase on a curve instead of a constant rise. Whether or not it can go negative is beyond me. I would imagine that since c is the maximum speed and time would seem to stop for an object traveling at c, we could only go backwards in time if we exceed c.

Also, a few more questions for everyone to try and answer.

1 - Does light have mass? (I think I already know the answer to this one.)
2 - How does light travel as fast as it does?
3 - Why can we not travel as fast or faster then c?

Again any answer will suffice. Thanks.

BTW I made a time calculator for fun, heh heh. It takes your speed in metres/second^2 and produces the time experienced by the object traveling at the speed specified. I’m just starting out in C++ so I can only do basic stuff like this, but it amuses me non-the-less.

Ok, this is what I’ve gathered.

The time experienced by an object on a graph appears to rise on a curve, rather then a straight line meaning that time will only distort significantly if we are extremely closer to c.

From my research, light has no mass which allows it to travel as fast as it does.

Now is there an equation that shows how much mass we gain when we approach a certain fraction of c? I’ve seen mixed responses saying either “when mass reaches” c, mass would require an infinite amount of energy to maintain that speed. I’ve also seen “as we approach” c, an object gathers more mass and at c we would require an infinite amount of energy to maintain that speed. Both of these differ drastically and I need someone to clarify which of these is correct.

We can arbitrarily claim that any particular object is moving at a speed close to the speed of light. Differences between time are introduced when we compare one system of coordinates with another, where the difference between the two systems is that one is moving relative to the other. Since we can identify a system of coordinates that is associated with any given object, we have to apply the proper translations when we write a proper description of an interaction between objects. Every object experiences time, so to speak, as if it were not moving at all.

Indeed there is. The amount of mass that an object has when it is at rest translates into momentum in a system of coordinates in which the object is moving. So if we consider any object in a system of coordinates in which the object is moving, then we will have to consider that it has a great deal of momentum in that system.

Ok, I’m not too incredibly knowledgeable in this area (Hints why I’m asking the questions, .) so I have a few questions.

One being, is an object ever at rest or can it be? I read somewhere that gravity is always affecting (Is that the right word?) mass wherever it may be in the universe.

Two, can you simplify that last bit?

Thanks.

Xilivai: time is much simpler than you might think. It’s a cumulative measure of motion. That might sound too simple, but think about a mechanical clock. You can’t see time, It isn’t actually clocking up “time”, just the spring-driven motion of the cogs and gears. A quartz clock counts the electrically-powered vibration of quartz. The definition of the day relies on the motion of the earth, as does a year. The official definition of the second employs an atomic clock which employs microwaves, and counts passing wave-pulses. It’s relying on the motion of light. I’ll start a new thread that explains it in detail.