"The future ain't what it used to be."

# time-travel to the past...

#### Paul

Timekeeper
I just thought I'd say if I could travel back in time it would be so COOL! Imagine meeting your younger self! The film THE TIME MACHINE is pretty exciting. I enjoyed watching the time traveller reach 802,701 A.D. TimeCop deals with serious changes to the past which start your mind wondering...
Timeâ€¦(a very strange thing)
Of course we all move forward in time every second of our lives. Newton thought time was absolute i.e. that it passed at the same rate regardless of anything. This simple common sense idea was believed for centuriesâ€¦
Until in 1905 Albert Einstein came to the conclusion that time must be relative. The speed of light 186,000 miles per second doesnâ€™t change if you are moving relative to it. No matter how fast or slow you are already moving youâ€™ill always measure a beam of light as 186, 000 mps.
Since light speed is actually absolute space and time must be relative. Time can be slowed down by increasing the velocity. This means if you take a trip traveling very fast for a year you could return and find a century might have passed for everyone else. Less time would have passed from your point of view. This is the time dilation effect predicted by Einsteinâ€™s special theory of relativity. In 1971 atomic clocks proved Einstein had been right about time slowing down. As you move faster in space you move slower in time. If you could travel at light speed time would stop and faster than light would take you back in timeâ€¦

TIME-TRAVEL to the future
Once you arrive in the future itâ€™s either impossible or very difficult to get back to the past.

General Relativity
*Gravity also slows down time.
*Gravity itself is actually a warp in space-time. When anything falls it falls because space-time is curved.

TIME-TRAVEL TO THE PAST!
It seems like no one really knows if itâ€™s possible or not. The laws of quantum gravity (which may answer the big question) are barely understood. Physicist Kip Thorne described how he might be able to make a time machine out of a macroscopic wormhole.

If someone could go physically back in time he/she could become involved in the making or remaking of history. Changes in the past could trigger a chain reaction of events preventing you from ever being born.

If you went back in time and visited your granny during her ninth birthday donâ€™t kill her! Because if you put a gun to her head and pull the trigger she could not have given birth to your mum. YOU certainly were never bornâ€¦

Therefore you could not have killed anyone as you never existed. Now this means your granny couldnâ€™t have been killed by you. She didnâ€™t die nine years old. This permits you to be born.

If you were born could you go back and kill your granny? No, not your real granny. This general idea has been used in Back to the future. Marty nearly stops himself from being born when he prevents his parents from falling in love.

Solving The Problem
1, You simply canâ€™t change history meaning if you go back in time you have no free will(as shown in Twelve Monkeys, Crime Traveller etc. Events will get in your way if you try to kill your granny. YOU CANâ€™T DO IT.

2, When you so-called change history youâ€™re actually moving up a different branch in time into another universe. The previous universe (where you were born) still exists. When you fire the the gun youâ€™re really killing another version of your grandmother.

3, Any actions you make in the so-called past has no affects on the present. Itâ€™s a different time-line universe.

The laws true solutions donâ€™t present real time-travel as you go into another world.

Conclusion
We canâ€™t simply use the grandmother paradox to rull out time-travel claiming it causes logical inconsistances. We need to look at all the possibilities.

How could we build a time machine?
The mathematics of general relativity suggest that under extreme conditions space-time might become so warped it would be possible to travel back in time. There is also the possibility of tunnels in time created by negative mass.

Very long rotating cylinders of matter-proposed by Frank Tipler

Kerrâ€™s spinning blackholes-since most stars spin this becomes worth looking (proposed by Roy Kerr).

Cosmic strings-(as Richard Cott suggested)

Travelling faster than light â€“ would take us back in time(as suggested by solutions to relativity). Wormholes might allow us to outpace light (if you walk through the short cut quicker than light throughconvential (normal) space.

Tachyons-are sub-atomic particles which always travel faster than light and therefore move back in time constantly. They have not yet been found and remain hypethical.

Contracting Universe- Time might then be running backwards but since everything else also would itâ€™s unsuitable.

Macro-wormholes(Kip Thorne showed how we could use it as a time machine).

Reviewing Crime Traveller

Crime Traveller was first broadcast on BBC one in march first 1997. The story begins when we see a quantum physicist named Holly Turner use her time machine.

In the first episode she reveals the time machineâ€™s existence to Jeff Slade, a detective. Jeff manages to get Holly to use the time machine to solve murders in several episodes. From the very start Holly tells Jeff that they canâ€™t change the past. Time has to protect history.

In the third and sixth episode Jeff is endangered when trying to change the past. Stephen Hawkingâ€™s chronology protection hypothesis is mentioned.

When they go back in time a parallel universe is created. Anything physical that happens to them, such as been injured, is erased when they arrive back to their own time zone.

Jeff was shot while time travelling and when he went back to his own universe it hadnâ€™t happened to him, the wound had healed. Photos and lottery tickets also back when you get back to the machine. This happens because they didnâ€™t take them photos or buy the ticket in the time zone they are now in.

If they are not back at the machine at the same point in time they left they will be trapped in the loop of infinity. This wil mean living the same time they travelled across again forever. Holly told Jeff it happened to her father.

In the seventh episode Jeff thinks he can cheat the laws of time to win the lottery. He knows the slip will blank when he arrives back in the present. He plans to go back in time tell Holly the winning numbers and she can buy the winning ticket. Jeff doesnâ€™t buy the ticket so it canâ€™t fade away.

Holly doesnâ€™t think it will work but eventually agrees to treat it as an experiment. The machine sends Jeff back twelve hours and fifty eight minutes. Holly has already left for work by then. Jeff goes to the police department where she works.

When Jeff is leaving a message for Holly he is urgently needed on a case. His boss cancels the training course his other self is on. He phones her office when she isnâ€™t in it. He tries to send her a fax but her fax machine has run out of paper. When he realises he wonâ€™t be able to contact Holly he asks Nicky to buy the winning ticket for him.

Jeff wrote the numbers on a piece of paper and gave it to Nicky. Accidentally he reads the numbers upside down. He misreads six and twelve as nine and twenty one. He only got four numbers. Instead of winning six or seven million pounds Jeff ends up winning only a hundred and eighty six pounds.

In the last episode of the series Holly finds out that sheâ€™s not the only person with a time machine. Steven Marlow paid a company to build a time machine and when they finished it he killed them.

He used time travel to give himself a perfect alibi. Jeff finds out and breaks into Web bio tech building. Using a different time machine he time travels and searches for Holly. Steven tries to kill her but Jeff manages to save her life. When Stevenâ€™s time machine breaks down he ends up trapped in a loop of infinity.

Michael French played Jeff Slade in Crime Traveller. He previously was David Wicks in Eastenders but didnâ€™t plan to return. Not he is in Holby City.

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Paul Curran