# Time Travel Pecha Kucha Presentation

Updated on May 31, 2012

## Prelude

This was a pecha kucha presentation that I gave (slightly shorter, as it was only 15 slides at 20 seconds each) on time travel. The presentation was obviously of extremely limited duration, and to a non-scientific audience, so I had to drastically simplify a lot of the concepts. The audience enjoyed it, and I presumed that it would make a decent hub as an introduction to the concept of time travel. I know that time travel is a lot more complex, but the design of this presentation is to get the main points across without a lot of complex science. Thank you for taking a look.

## Introduction

Have you ever wanted to go back in time and do something over? You can turn the hands on a clock back, but, despite what it says, you are not going back in time. Why doesn’t it work like that?

## Defining Time

To answer that, we first have to define time. Fortunately, that has already been done for us. In his general and special theories of relativity, Albert Einstein effectively redefined time as movement in a fourth dimension.

## Measuring Time

A clock is a device that measures time, much like a ruler, which measures the other three dimensions. Moving the hands on a clock doesn’t change time any more than moving an object along a rules changes its size. That brings us to an important question:

## The Question

Is there anything that affects the rate of the passage of time, and would it make time travel possible? The answer is yes. I am going to discuss what affects time, and how time travel is possible through the usage of technology and natural phenomena.

## Space-time

The three dimensions of space and the one dimension of time are merged into space-time. All of matter has mass, and also all of matter is in motion, both of which are directly proportional to how matter alters the passage of time.

## The Effect of Velocity on Time

When an object, such as a space shuttle, moves with sufficient velocity in comparison to another object, such as the launch site, it experiences time dilation. To the launch site, time appears to move slower on the space shuttle.

## The Effect of Mass on Time

Objects with a lot of mass, such as a black hole, also experience time dilation in comparison to less massive objects, like a person. The time dilation between a satellite and antenna on Earth must be accounted for in order to make GPS accurate.

## Black Holes

Going back to black holes, they are collapsed stars which have infinite density. Their escape velocity exceeds the speed of light. That means that anything inside a black hole cannot get out. Theoretically, time could stop past the event horizon of a black hole.

## Light Cones

Space and time are graphed into light cones. The present event is in the center. The shading below it is in the past, while the shading above it is the possibilities of the future. Anything outside of the cones is not an event, and it must either go faster than light or go through a wormhole.

## Wormholes

There are many different types of wormholes, but I am only going to give a cursory explanation of a couple of simple types. The first is an interaction between a black hole and a white hole. The other is a recurvature of space-time, which I shall call a space-time tunnel.

## Black Hole/White Hole Wormhole

If you wanted to travel to Alpha Centauri, it would take time to get there. However, if there was a nearby black hole, you could go through the wormhole and exit at the white hole by the star. It would take you almost no time at all because you would be travelling through very little conventional space-time.

## Space-time Tunnel

In a space-time tunnel, you would be going through the same amount of space-time, but, because the time dimension is recurving, you would be travelling backwards in time. In this instance, you could revisit the past and share information from the future.

## Some Problems With Technology

There are some problems with time travel. Obtaining a velocity for an appreciable time dilation requires an immense amount of energy. Currently, we do not have a powerful enough energy production method to maintain such speed. Also, we have no material strong enough to withstand such drastic conditions.

## Problems With Nature

Black holes are voracious monsters of space, and white holes vomit enough energy to destroy whole galaxies. Here is a black hole swallowing a star and a white hole hurling its remains into the heavens. Nothing would survive.

## Conclusion

So, now you know some ways that time travel is possible. You also know that there are some problems that must be overcome before it is feasible. Sadly, it is going to be quite some time before you can take a vacation in the future or the past.

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