## Time in an Instant

There is nothing instant about “instant”.

Not in coffee, not in two shakes of a lambs tail (or a coffee spoon) and not in love at first sight.

I’ve harped on before about the importance of the speed of light, and how nothing can go faster than it.

In the latter article I gave the example of the Earth rotating around a non existent sun after for some reason the sun ceased to be; the transmission of information that the sun ceased to be (one parameter being the existence of gravity) would take some 8 minutes to reach the Earth. The Earth would therefore remain in orbit around a non existent sun for those transitional 8 minutes.

Archimedes had his brainwave whilst he was taking a bath. I had mine during a shower, watching the waste water spiral down through the plug hole. In true Archimedian style I thought to myself “Screw it.”

Why? Surely there must be something out there that can exceed the speed of light.

And I might have found it.

Let’s return to our orbiting Earth (or at least, remain firmly affixed to it’s surface, thanks to our gravitational friend).

As far as we are concerned, sitting (or showering) on the Earth, everything is hunky dory until the Sun disappears, the light goes out and we are flung into space obeying Newton’s second law of motion (i.e. that we travel in a straight line at constant speed unless an external force [in this case, the Sun’s gravity] is applied.

We know that the sun must have vanished 8 minutes ago, so let’s call that moment t = 0 and the present t = 8.

So from the perspective of the Earth at t = 8 we know that the sun vanished at t = 0.

And on the sun, the sun vanished at t = 0. At the same time, i.e. at t = 0. The event of our hindsight knowledge and the event itself was simultaneous.

Is hindsight instantaneous?

I think the example shows that the progression of time across space is instantaneous, although I do concede that it’s a bit strange to give time a speed when it is itself a term in the equation! (speed = distance divided by time!

I’ll conclude with a quote from Bill Nye (more time and time travel quotes here):

â€œWhen we see the shadow on our images, are we seeing the time 11 minutes ago on Mars? Or are we seeing the time on Mars as observed from Earth now? Itâ€™s like time travel problems in science fiction. When is now; when was then?â€ â€“ Bill Nye.

Paul

## Is time travel really impossible?

Maybe some don’t dare to believe that time travel is possible, but this view is changing! The understanding of the science behind time travel is improving

Is it or isn’t it…who really knows?

Most of us probably don’t dare to believe that time travel is possible, but I think this is changing! The understanding of the science behind time travel is getting better understood, and an increasing number of scientists are now finding ways which one day might unlock the mystery of the time machine blueprint. The hard study and the calculations continue.

But even if we don’t know how to travel in time now…that doesn’t mean it’s impossible…does it?

Why isn’t time travel impossible?

There are so many paradoxes associated with time travel that you could well be forgiven for thinking that time travel is not possible. The “grandfather paradox” – where you go back in time and kill your grandfather (why would you do that?!) thus preventing your own existence to go back and kill him in the first place is perhaps the most famous of these paradoxes.

Or if time travel was possible, surely we would have met time travelers who have come to our time from another time by now?

So on the face of it, it would seem that the idea of time travel is just that…an idea. It has certainly captured the attention of many science fiction authors, and even poets. And recently…scientists. Yes, there have already been many eminent scientists who have gained funding for looking into the possibility of time travel – and to find a way to make it happen. They do this by turning to Einstein’s theory of relativity.

Einstein’s theory of relativity is used to describe our understanding of time and space. Actually, time and space are so heavily intertwined that they are referred to collectively as “timespace” as one affects the other. By studying the theory of relativity, scientists hope to discover a solution to its equations which permit time travel. So has there been any success?

Interestingly, success has been found in the opposite sense…that is to say that nothing has been found which forbids time travel. So that is good news for those of us who would like to travel in time – though we are still no closer in finding out how we can do this. Or are we?

Time dilation

The theory of relativity describes “time dilation”. Time dilation refers to how a second of time can take longer in some situations than in others. This is slightly different to the perception of time which Einstein himself has been quoted as saying “When you are courting a nice girl an hour seems like a second. When you sit on a red-hot cinder a second seems like an hour. That’s relativity.”

Here’s an example of time dilation. There are 2 identical clocks. Let’s call then clock A and clock B. Clock A is put on a jet plane, whilst clock B stays on the ground at the airport. The jet plane takes off, travels at high velocity around the world and lands back at the airport. The times on the two clocks are compared…clock A (the clock which was on the plane) shows that less time has elapsed than shown by clock B at the airport. Why? Because travelling at speed causes time to slow down. That is time dilation.

Another example of time dilation is seen in the satellites used in GPS navigation. In this case, there are two causes of time dilation. The first is the high speed relative to the Earth at which the satellites travel, and the second is the decrease in gravitational potential the satellites experience in orbit. The clocks on board the GPS satellites actually need to be corrected for the effect of time dilation!

The existence and reproducibility of time dilation is a good step towards realising the possibility of time travel. But are we any closer to making our time machine?

Faster than light

Perhaps. Experiments have been conducted which have shown that faster than light speed travel might be possible with some sub atomic particles and arguably this is a step in the right direction for moving on towards building a time machine. However, the energy input required is astronomical, and to reiterate…this was only a sub atomic particle! Perhaps the understanding of an alternative theory of timespace would show a solution to time travel where the energy requirement is not a practical limitation.

Having said that the subject of time travel is now receiving more attention from scientists, that is not to say that all scientists are in support of the existence of time travel. Many scientists have discredited the idea entirely, and it is clear that the question of whether time travel exists or not is still a topic of hot discussion.

So is time travel possible?

I think that presently, it is not possible in the way that we would like it to be – the days of the fabled time machine are far away. I do hope that one day in the future we will be able to travel back to the past, or into the future and experience other times just as we can experience and enjoy the present, though at the same time I am cautious about the possible dangers. Many of us are still not able to navigate safely through space (just think of all of those road accidents…) and I’m sure that navigating through time is a much more complex issue.

Thankfully, even if real life time travel doesn’t exist, we can still read about it in science fiction!

For a more detailed look on the possibility of time travel (and how), take a look at my time travel 101 main page. If you have time! 😉

## What is the role of the speed of light in time travel?

You’ve probably found that there are many references to the speed of light when reading about time travel. This brief articles hopes to explain the relationship between the two.

The speed of light is not just the speed that light travels – in some ways that can be considered to be a coincidence. The speed of light is the speed limit of the known physical universe, and is just shy of 300 million meters per second. This speed limit relates to everything, including the transfer of information. This might be counter-intuitive, but there is no such thing as “instant”! (And I’m not one to argue with Einstein!)

So how is this related to time travel?

Einstein’s theories show that time can dilate in a number of circumstances. Time dilation is where the passage of time occurs at a different rate in one situation than it does in another. For example, time passes more quickly for someone experiencing a lower gravitational acceleration than for someone who is subjected to high gravitational forces. Another example, and relevant to our discussion here, is that time passes more slowly for someone who is travelling at speed in comparison to someone who is stationary.

This means that if someone flew in a jet engine at high speed, his watch would register a shorter time of flight that someone who remained standing in the airport waiting for his return (this might explain why planes are always late! 😉

The greater the difference in relative velocities, the greater the effect of time dilation. For the velocities that we are easily able to acheive in everyday life, the effect of time dilation is very small (in the order of milliseconds.) However, if we could gain very high velocities, and travel at them for sufficient lengths of time to accrue the time differences, the effects can be noticeable.

This is of significance to the time traveller. If I travelled at a sufficiently high velocity, my experience of the passage of time is slower for that of someone waiting for me to come back. In practical terms, in my point of view, I’d fly for say 1 year, but someone waiting for me would have waited for a year and a month. In effect then, I have travelled 1 month into the future.

If then, I travel at a greater speed, the effects of time dilation are proportionally greater; I travel at twice the speed I did before for 1 year, and my expectant welcome committee would have waited for 1 year and 2 months.

It follows that the faster I travel, the further into the future I can transport myself. It also means that my journey doesn’t need to last as long – instead of travelling at high speed for 1 year, I can travel at a faster speed for 1 month. Or an hour. Or a second. There is greater efficiency in time travel at higher speeds.

And we know that the fastest speed we can travel is the speed of light! This is why achieving light speed is considered to be important in time travel.

There are two important things to note here…

The first is that in this way, time travel into the future is possible, but not the past.

The second is a possible time travel paradox – the so called twin paradox. I mentioned that I travelled at high speed for one year, whilst someone remains stationary on Earth. But relatively speaking…who’s to say that I wasn’t stationary, and it was the Earth-bound person who moved away at speed? In real terms, each of us would find that the other person has experienced more time than themself, and this is not possible!

Actually, the ‘solution’ to this quandary is in the means by which I gain high velocity. If my journey starts on the Earth, my velocity is zero in relation to my observer. I then accelerate to high velocity. Here then is the solution – acceleration brings about a further time dilation effect for me as the traveler (as well as time dilation by moving further away from Earth’s gravitational field). These differences would ensure that our relative experiences of time passage are different from each other.

As a side note – what would happen if the speed of light really could be exceeded?

I hope that this explains the relationship between the speed of light and time travel!

## What is time travel?

There are many definitions of time travel but most compare travelling through time with travelling in space. I suppose this makes sense in a way, although there is a definite difference: we have control when we travel through space, but we all travel through time by doing nothing, and we can do nothing about it. I’d argue that time travel, then, needs some sort of control in how we move through time.

I’ll write later on the speed of light and its importance in time travel, but the two must not be confused; for now I’ll clarify with an example:

When you look up at the stars, it is commonly said that you are “looking into the past”. This is because the stars are so distant that the light travelling from them takes several years to reach us…so we see them as they were this many years ago. But is this a form of time travel? Are we really looking into the past?

I don’t think so. I think this is more similar to watching a movie of say, your children, which was taken some time ago where again, we are watching past events. I suppose the difference is that you can watch those home movies again and again, whereas we can only see the stars for that one ‘real time’ moment.

I believe that a certain level of interaction is key for time travel. If I went back in time, I could qualify that statement by describing the people and places and things that I saw that I otherwise would not have been able to see. There is a new exchange of information. With a home movie, we can’t look out of the camera view, or talk to the people on film (or hear back from them). A time traveller, on the other hand, would be able to look wherever they wanted, or interact with the people and objects in the new time.

I hope that this has answered the question of “what is time travel?”

Further examples of what is and isn’t time travel can be found here.