Stephen Hawkins Universe - Time Travel

[Castiel]

well you'll want to write to the program makers then as he's just quoting them.

where are you getting the 7 year figure from btw?

The program is either seriously wrong or the OP has confused what it said.

The time dilation equation and an explanation on how it's used is here:

http://www.amnh.org/learn/pd/physical_science/week3/time_dilation.html

Basically for every year travelled at near the speed of light, seven years pass on earth.

 

[Koalaboy]

They said that the people on the train (just slower than the speed of light) would have experienced 1 week of time, but 100 years would have passed.

 

[Amp34]

Cryogenic sleep solves that problem.

But not the issue of Butlins Holiday park.

Nope, the OPs math is way off. If you travel for one year at the speed of light (.99) then during that lightyear, seven earth years would have passed.

Incidently if you travelled for one year at twice the speed of light only 7 months would have passed, hence travelling back in time (but only in relation to your travelling time)

Those maths would make more sense, but I'm sure that isn't anywhere near the times they mentioned... Anyone with 4OD want to clarify?

Amount of energy required to accelerate anything with mass resembeling that of spaceship up to that speed would be a problem.

*Haven't watched said programme

Apparently it would need a rather large ship, because of the amount of fuel.

 

[Castiel]

Amount of energy required to accelerate anything with mass resembeling that of spaceship up to that speed would be a problem.

*Haven't watched said programme

To accelerate any mass to lightspeed would take infinite energy, thus according to the laws of physics as we know them it is impossible (hence startrek and other scifi move space not the ship). 99 percent would require energy bordering on infinite so again highly improbable.

To get around this physicists say you can bend space-time to traverse the galaxy which negates much if the energy and time dilation effect.

 

[Alex_6n2]

Relativistic effects aside, getting a ship of what would be a very large mass up to 0.99c would take so much energy that it would never happen, so it will never be an issue. Time travel will never be achieved this way.

On the travel subject, only viable way of travelling intergalactic distances is either going to inter dimensional travel (Travel through a fourth spacial dimension) or hitching a massless ride on a theoretical particle that's already travelling faster than light. Both of which seem totally unrealistic now but technological and knowledge limits ignored are more viable than super fast physical speed. And we don't have any idea how these methods will effect relativistic time.

 

[d_brennen]

Who needs space/time travel? There's so much to learn about our Earth!

Besides, we need to build a Matrix to live out CGI fantasy lives

 

[daz]

http://en.wikipedia.org/wiki/Gamma_factor

Edit: To clarify, you put the numbers in to that equation (0.99) and dt/dtau comes out at 1/0.14 or about 7. (So 7 times slower for a ship travelling .99x the speed of light)

 

[Lashout_UK]

There's a brilliant book called Tau Zero (fictional) which is about a near-lightspeed ship that ends up out of control and the consequent results.

http://en.wikipedia.org/wiki/Tau_Zero

As far as I'm aware (it's one thing that's in the book and something that people seem to forget) while you might not be able to get to lightspeed, you can get very, very close (forget about the percentages, unless you want to run into millions of decimals) - and the closer you get, the more the time dilation increases. I was under the impression that you could accelerate closer and closer to the speed of light, but never breaking it, but forever increasing the time dilation to ever higher levels?

 

[Robosapien]

To accelerate any mass to lightspeed would take infinite energy, thus according to the laws of physics as we know them it is impossible (hence startrek and other scifi move space not the ship). 99 percent would require energy bordering on infinite so again highly improbable.

To get around this physicists say you can bend space-time to traverse the galaxy which negates much if the energy and time dilation effect.

How do you bend spacetime? With loads of mass? Which equivalent to energy?

 

[w3bbo]

Isn't time relative to gravity? I'm sure I read somewhere that the space shuttle 'time travels' as the digital clocks on there are calibrated to run ever so slightly slower due to the time difference between up there and down here....

....or am I missing the point entirely

 

[Koalaboy]

http://www.news.com.au/technology/t...-stephen-hawking/story-e6frfro0-1225861418565

However, once spaceships approached the speed of light, their crew would start skipping through Earth years on a daily basis, giving the human race a chance to start again.

“It would take six years at full power just to reach these speeds," Hawking said.

"After the first two years, it would reach half light speed and be far outside the solar system.

"After another two years, it would be traveling at 90 per cent of the speed of light.

“After another two years of full thrust, the ship would reach full speed, 98 per cent of the speed of light, and each day on the ship would be a year on Earth.

"At such speeds, a trip to the edge of the galaxy would take just 80 years for those on board.”

 

[daz]

Isn't time relative to gravity? I'm sure I read somewhere that the space shuttle 'time travels' as the digital clocks on there are calibrated to run ever so slightly slower due to the time difference between up there and down here....

....or am I missing the point entirely

Yes, this is in general relativty
Travelling fast is covered in special relativity

 

[Castiel]

They said that the people on the train (just slower than the speed of light) would have experienced 1 week of time, but 100 years would have passed.

I haven't watch the program, but I know the math.

The problem is that the equation is exponential, so the closer you get to 100% Lightspeed the closer to infinity you get, hence the paradox. Once you begin to travel at multiples of lightspeed your subjective time gets longer than earth time so technically you would age quicker, relatively anyway.

 

[Robosapien]

The time dilation at only 99 percent the speed of light is not great enough for that period of Earth time to have passed in relation to Ship time.

One Lightyear is the distance it takes light to travel a specific distance....Thus in 80 years ship time, only 560 years would have passed during the journey. The Galaxy (milky way) is about 100,000 light years across so light would take 100,000 years to traverse the galaxy.

To extrapolate, a starship travelling at lightspeed would also take 100,000 years to traverse the galaxy (ship time), however back on earth due to relativistic time dilation 700,000 years subjective earth time would have passed.

Is the starship travels at light speed then an infinite amount of Earth time would have passed.
At .99c, isn't 100,000 years our subjective earth time, and it's slower for observer traveling at .99c?

 

[Amp34]

http://www.news.com.au/technology/t...-stephen-hawking/story-e6frfro0-1225861418565

Ahh, it's day, not minute or whatever I put. Still 30 thousand years, not really useful in any sense.

That doesn't however correlate with the 7:1 ratio some in this thread are talking about...

Having said that I think it is aimed at the lowest common denominator.

 

[~>Dg<~]

it is 7:1 as i remember embarrising a maths teacher on this subject in first yr sceniors

 

[Castiel]

http://www.news.com.au/technology/t...-stephen-hawking/story-e6frfro0-1225861418565

As Brian Cox stated, they are talking about 99.99r the speed of light, not 99 percent the speed of light as the OP said.


You can work it out using the Lorenz Factor equation

γ = (1 − v2/c2)−1/2.

 

[stulid]

The show also showed that time travel happens right here on earth and in orbit.

The 31(think its that many) GPS satellites gain 3 billionths of a second everyday which needs correcting otherwise the equipment down here on the surface will be approximately 6 miles out.

the time difference is explained by the mass of the earth and its gravity slowing down time, so the objects in space(satellites) gain time being further away.

 

[greywolf]

If traveling in a straight line in some ship, you would only be traveling in time in that one dimension, what about the other dimensions that you are not? They would be out of sync so to say with the one that you are passing along at close to the speed of light.

 

[Castiel]

Is the starship travels at light speed then an infinite amount of Earth time would have passed.
At .99c, isn't 100,000 years our subjective earth time, and it's slower for observer traveling at .99c?

Yes you are correct, but it is exponential. At 99% the dilation is 7 years, for each percentage above this to 100% this rises exponentially to infinity. I think the OP meant 99.99r to attain those kind of time dilation effects, hence the confusion when you use the equation.

γ = (1 − v2/c2)−1/2