# Time travelling

## Recommended Posts

All of those particles are known to exist. The tachyon is purely theoretical - nobody knows whether it actually exists or not.

(Also, I suggest you count the number of times they use the word "tachyon" in ST:TNG. It's quite obscene).

• Replies 206
• Created

#### Popular Days

yes, they say tachyon, but not tachyon frequency :Þ

##### Share on other sites

It is not posible to travel in time, neither to future of past. In theory is posible of course but in practice is not aplicable.

##### Share on other sites

Flak.. well but tell us why not? :S

##### Share on other sites

Is not posible technically speaking. No matter how fast you move you wont got back or foward. If you move 10 times the light speed you inside the vessel will be in present and the people outside will be in present aswell.

For example, in case cryogenic is posible, you travel 90 years at light speed to an star at 90 light years of distance, when you reach there you will be like when you enter on the cryogenic but on earth 90 years passed. You actually dont travelled in time to future just was in the cryogenic.

Other theory is that you can travel in time by entering on a wormhole. In case this is posible due of the stong forces around, you wont travel back or foward, just to any unknow place in the universe, but in present time.

About past, let say you go to a planet 20 year light of distance and with a potent telescopy you spot the Earth, you will notice the earth events 20 years earlier, but you will be in present and on Earth will be present aswell and all you check are part of the past.

The only posibility that for example, watch the dinosaurs, is go to a planet 70 millions year light of distance and with a powerfull telescopy watch the earth. But you will need very powerfull traveling devices to get in time, with cryogenic at light speed you will notice the current day you left the Earth.

##### Share on other sites

Any other examples? Preferably ones that don't involve string, but theories that can be tested with repeatable results.

Tachyons aren't nice because they destablise the vacuum. Rather oddly, as they lose energy they travel faster, so pretty soon all tachyons would be moving increadibly fast, spewing out energy as they went. In technical terms, the universe would not settle in the vacuum state that we observe, but would keep dropping to lower and lower energy states.

The only real way out of this is to assume that tachyonic states can't communicate with ordinary particles. This is actually fair enough, because the standard energy/momentum conservation relations prevent the tachyons coupling to ordinary particles. And if they do not couple to ordinary particles, then we cannot observe them (by definition: since we are made of ordinary particles, we need to be able to interact with them to observe them), and they may as well be removed from the theory (Occam's razor).

##### Share on other sites

Is not posible technically speaking. No matter how fast you move you wont got back or foward. If you move 10 times the light speed you inside the vessel will be in present and the people outside will be in present aswell.

For example' date=' in case cryogenic is posible, you travel 90 years at light speed to an star at 90 light years of distance, when you reach there you will be like when you enter on the cryogenic but on earth 90 years passed. You actually dont travelled in time to future just was in the cryogenic.

Other theory is that you can travel in time by entering on a wormhole. In case this is posible due of the stong forces around, you wont travel back or foward, just to any unknow place in the universe, but in present time.

About past, let say you go to a planet 20 year light of distance and with a potent telescopy you spot the Earth, you will notice the earth events 20 years earlier, but you will be in present and on Earth will be present aswell and all you check are part of the past.

The only posibility that for example, watch the dinosaurs, is go to a planet 70 millions year light of distance and with a powerfull telescopy watch the earth. But you will need very powerfull traveling devices to get in time, with cryogenic at light speed you will notice the current day you left the Earth.[/quote']

Traveling to the future can be done without breaking the speed of light. As you accelerate, time slows down FOR YOU. Atomic clocks synchronized on the ground show a different time when one is placed in a supersonic airplane. Yes, you will always be in the "Present", but you can arrive to the "Present" in a shorter amount of time than everyone else.

Traveling to the past is a different story.

##### Share on other sites

time travel to the future is easy. i do all the time. just did it. did it again. doing it right now.

##### Share on other sites

Traveling to the future can be done without breaking the speed of light. As you accelerate, time slows down FOR YOU. Atomic clocks synchronized on the ground show a different time when one is placed in a supersonic airplane. Yes, you will always be in the "Present", but you can arrive to the "Present" in a shorter amount of time than everyone else.

Because is the clock got affected by the supersonic flight.

##### Share on other sites

Time is relative, people. There is no such thing as universally simultaneous events so this talk of past/present/future remains in the realm of the abstract. Can I ask a question politely? How many of you here have actually studied relativity at a university/college level?

Judging by the responses, not many. I think in the interest of this site remaining a valid scienctific forum, please outline when you are stating your opinion and when you are stating accepted 'facts'. All too often we have people proffessing violations of relativity or new takes on space-time as though they are valid scienctific facts as opposed to errorneous(but interesting no less) opinions. I have no problem with people expressing their opinions, as long as they state it, as there are a few on this site who may read what your saying and believe you. Not exactly standing the youngins in good stead for their future education.

Just an idea...

##### Share on other sites

How many of you here have actually studied relativity at a university/college level?

I have.

who wrote that?

##### Share on other sites

I also had learned at a college. All of us was for sure.

##### Share on other sites

Because is the clock got affected by the supersonic flight.

The speed of sound has nothing to do with it. The closer you get to c the slower time passes for you relative to a "stationary" observer.

edit: I did not learn at a university. I'm just a high school student by the way.

##### Share on other sites

The lightspeed have nothing to do with time. If we get the light of an start 20 years light of distance we are just receiving the light of 20 years ago.

##### Share on other sites

You mean that when we look at a star 20 light years away we are seeing the light that existed 20 years ago? Well yeah, so what?

I'm not sure what you meant by "The lightspeed have nothing to do with time."

##### Share on other sites

I'm not sure what you meant by "The lightspeed have nothing to do with time."

He sure meant that travelling at lighspeed doesnt makes you go trought the time. you only overpass the light sent before. or something like that.

##### Share on other sites

• 3 weeks later...
What I can't visualise is if a ship flew across our heavens at the speed of light for 93 million miles and I was on it and it took me 8 minutes to make the journey. How would that affect time on Earth in relation to my own??

Travelling at lightspeed it would take me 8 minutes and the people left on Earth would see it for 8 minutes too.

Our sun is moving through our galaxy so when we look at the sun it is actually moved in relation to where it was 8 minutes ago which is what we see.

If I'm travelling 93 million miles at light speed and it takes me 8 minutes the people on Earth will still only see me 8 minutes away from where I started. Won't they??

Thanks for all the replies but I'm still no wiser, maybe I should try rephrasing my question.

Say the ship (in the quote above) was magically converted into light wave particles near our Sun and travelled to Earth as light. The ship would still be the same thing with people still living on it as normal but it would be made from light particles, we're talking Harry Potter fantasyland magic here.

Since it's travelling at the speed of light it would make the 93 million mile journey in around 8 minutes.

How can those people set off from near the Sun at 5pm and arrive here at 5:08pm according to our clocks but arrive much further into the future according to their clocks on the ship??

Doesn't light from the Sun go through the same time distortions??

Einsteins theory just sort of breaks apart when I think about it like this...

##### Share on other sites

.

How can those people set off from near the Sun at 5pm and arrive here at 5:08pm according to our clocks but arrive much further into the future according to their clocks on the ship??

time dialation

$t=\frac{t'}{\sqrt{1-\frac{V^2}{c^2}}}$

edit: to them, they would have arrived at 5pm, not 5:08pm

##### Share on other sites

Thanks for all the replies but I'm still no wiser' date=' maybe I should try rephrasing my question.

Say the ship (in the quote above) was magically converted into light wave particles near our Sun and travelled to Earth as light. The ship would still be the same thing with people still living on it as normal but it would be made from light particles, we're talking Harry Potter fantasyland magic here.

Since it's travelling at the speed of light it would make the 93 million mile journey in around 8 minutes.

How can those people set off from near the Sun at 5pm and arrive here at 5:08pm according to our clocks but arrive much further into the future according to their clocks on the ship??

Doesn't light from the Sun go through the same time distortions??

Einsteins theory just sort of breaks apart when I think about it like this...[/quote']

The people in the ship wouldn't arrive much further into the future, they would arrive with no time having passed at all. At c, time ceases to pass.

##### Share on other sites

'']The people in the ship wouldn't arrive much further into the future, they would arrive with no time having passed at all. At c, time ceases to pass.

isn't that what my last post said?

##### Share on other sites

im sorry if this has already been covered (there is a lot of stuff in this thread) but since when does something get more massive when its moving faster?

(if this has already been covered in this thread then bash me down with insults and ill retreat back into my corner)

##### Share on other sites

'']The people in the ship wouldn't arrive much further into the future, they would arrive with no time having passed at all. At c, time ceases to pass.

why? why would something moving faster cause it to not experience time? i have always looked at it as a vector kind of thing, time is just another dimension. if im on an extremely wide conveyor belt moving to my left and im walking forward it doesnt matter how fast i walk forward, i still go left at the speed of the conveyer belt. they dont effect each other.

##### Share on other sites

since always.

$m=\frac{m'}{\sqrt{1-\frac{V^2}{c^2}}}$

edit: time dialation

$t=\frac{t'}{\sqrt{1-\frac{V^2}{c^2}}}$

if V=c, then V^2=c^2. c^2/c^2=1, that makes $t=\frac{t'}{\sqrt{0}}$. $\sqrt{0}=0$, so t is now undefined.

##### Share on other sites

i really dont care how many formulas you have. its the reasoning behind them i was wondering about.

## Create an account

Register a new account