StarCraft® II

The Light Train to the Future

Posts: 638
I thought this was an interesting concept. I don't have a link but I recall stephen hawking talking about this on a show of his. The concept:

The light train is a maglev train that travels around the world at near the spead of light in a air-tight tube with the air sucked out of it. However, it is only supported above the ground by magnets, it is propelled by electromagnetic hoops at points along the track and pull it forward at progressively smaller intervals, like a enormous motor. The passengers on the train would stay on the train for two weeks and exit it 80 years in the future.

While the concept is intriguing and according to Stephen Hawking's calculations, plausible, there are some problems with the practical physics.

First off is centrifugal force. The earth is a gigantic sphere. A loop around it will create slight centrifugal force that becomes statistically significant as the train progresses towards the speed of light. The train will be ripped off the maglevs and forced against the top of the airtight tube. The passengers will also be crushed against the roof of the train.

There is also another problem. While two weeks is short for the passengers, it is quite a long time for a terrorist or genocidal murderer two bomb the track or sabotage any part of the mechanism. Like it or not, it will be a pain in the !@# to guard the track and prevent such shenanigans.

I just thought I'd share this concept with you guys.

TO THOSE WHO DO NOT UNDERSTAND THE PHYSICS OF THE TIME TRAVEL ITSELF

As any object nears the speed of light, they can't move faster because doing so would be moving faster than light, which is impossible because the object has to have mass. As they put more and more energy into moving faster, the energy has to go somewhere, so instead of moving through space, they move through the closest thing: time.
Edited by Xase on 8/29/2011 10:36 AM PDT
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Posts: 3,492
Huh, this is interesting.
So what would it look like to people outside the train? Would the train be constantly going for 80 years, even though it would feel a lot shorter for the people inside? Because that leaves a lot of time for terrorists to destroy it as you said. Or would it just disappear in 2 weeks and reappear in the future?
I'd say it's impossible anyway though. Good luck getting so many countries to agree to let you build a giant tube through their land, not to mention oceans.
Also, what is the practical purpose for this? I really don't see one.
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Posts: 142
I have not heard of this idea before but it's interesting (pratical application : send in sick people so they can 'travel' to the future to be cured; like cryogenics in the movies) (who cares about application, this is physics :D ).

Quick question (I haven't done relativistic electrodynamic in a while) : as you move faster and faster, wouldn't the magnets create an electric field (moving magnetic field makes an electric field) that would slow you down, hence limiting your speed at some point?

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Posts: 638
I have not heard of this idea before but it's interesting (pratical application : send in sick people so they can 'travel' to the future to be cured; like cryogenics in the movies) (who cares about application, this is physics :D ).

Quick question (I haven't done relativistic electrodynamic in a while) : as you move faster and faster, wouldn't the magnets create an electric field (moving magnetic field makes an electric field) that would slow you down, hence limiting your speed at some point?


A magnet passing in between copper coils creates electricity in the coils, hence, we have a generator. But the moving magnets are only moving around other magnets, and unless there is something I don't know, as long as you're pumping energy into the maglevs, there will be non generated.

Then again I'm in 8th grade so I really have no idea what electrodynamics truly encompass.
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Posts: 68
it would not work unless you had a nearly unlimited amount of energy at your disposal because the faster it goes, the more energy it take to move it faster
and how are you going to slow it down
Edited by TheEater on 8/26/2011 8:59 AM PDT
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Posts: 638
There are a lot of practical issues to this, but I thought it was intriguing.
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Posts: 85
Basically TheEater is right. As the speed of an object increases relative to an object at rest, three things happen:
1. time for the moving object slows down, compared to the resting object
2. length (space) for the object contracts, compared to the spatial length of resting object
3. mass increases for moving object, compared to mass of resting object

Say the train itself weighs 20,000lbs at rest. At 0.99c the weight of the train in earth's gravitational field would be 137,167 lbs compared to an identical train at rest. After two weeks in the train, the earth itself would have experienced a total of 99 days. For this kind of cute idea to be effective the train would have to travel well over 0.99c. The bad thing is that the mass increase spikes even more drastically and so do energy requirements for acceleration. (I used some online java calculator for these numbers so idk if they're accurate)

To put into perspective, an SR-71 blackbird can fly at almost 1000m/s whereas 0.99c is somewhere near 297,000,000m/s.

BUT the real question is....say this it were possible to accelerate a train to the speed required for the 2weeks=80years time dilation. What happens when the mass (read: gravity) grows infinitely high while the train is driving in a circle around the earth?

cool to see some 8th graders are interested in stuff, makes me want to dig out my old astro textbooks!
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Posts: 85

We -do- have an effectively unlimited and easily accessed source of energy right nearby - the sun.

It'd just take some actual forward-thinking politicians to spend the money necessary to harvest it properly - which could be accomplished with our current level of technology today - and we'd completely remove reliance on fossil fuels and have more than enough energy than we could ever need for as long as we stay in this star system.


Politicians are very forward-thinking....about how much money they are going to make from oil lobbyists!

I agree solar energy is not used enough. But it takes a lot of surface area to make it effective. The sun spits about 340watts per square meter onto the earth, which is fine for small scale uses. But america averages 1460 watts per second per person, so solar energy is supplementary at best. Although I did see a really cool article about a solar power plant that used a huuuuge mirror array to focus the suns energy into super-heating a salt resevoir until it liquified, then cooling it with water, creating steam to spin turbines. I think it said it was powering an entire city, forget where. very cool stuff.
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Posts: 85
The problem you're running in to is that you're not considering the proper location for massive solar farms; it's not on Earth.

Two large solar stations on the moon would put one in sunlight all the time, and with no weather there'd be no interruption due to clouds - and with no atmosphere there'd be no loss of sunlight. With no plants, animals, weather or seasons there'd be very low wear and tear.

It would cost a lot to get it operational, but is possible with our current level of technology (and in fact, the solar panels themselves would be much, much easier to manufacture in an environment with no atmosphere), and it would completely fulfill all our power needs.


Of course it is possible. NASA had an exploratory project some time ago to research the feasibility of a solar array in space, but it was a satellite not a fixed structure on the moon, which would have the same benefits of a moon-based system, without the drawback of being so far away. However they determined new developments would be required to make it cost-effective.

1. Cost of spaceflight overall is too high.
2. The most cost-effective solar panel tech would be damaged by solar wind/storms which could shut down or severely reduce power output over the course of a few years.
3. Maintenance costs.
4. There may not be plants, animals or atmospheric weather in space, but micrometeors are extremely commonplace and can travel with very high kinetic energy. Also solar weather can be damaging to any electrical systems. Space is very harsh, and shielding costs are very steep, and would be difficult for something like a solar farm.
5. A large percentage of collected energy would be required to power the transmission to earth.
6. Cost of transmission/receiving apparatus would be significant. Dipole rectenna is cheapest, I think, and operates at 85-90% optimal efficiency. I'm not sure about transmission antennae.

These are just some things I could think of based from memory of college and random internet surfing. I love these kinds of ideas but it's not merely a problem of politics or thinking outside the box.

I think we will probably see other breakthroughs in energy tech before this kind of thing comes to fruition.
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Posts: 638

We -do- have an effectively unlimited and easily accessed source of energy right nearby - the sun.

It'd just take some actual forward-thinking politicians to spend the money necessary to harvest it properly - which could be accomplished with our current level of technology today - and we'd completely remove reliance on fossil fuels and have more than enough energy than we could ever need for as long as we stay in this star system.


Politicians are very forward-thinking....about how much money they are going to make from oil lobbyists!

I agree solar energy is not used enough. But it takes a lot of surface area to make it effective. The sun spits about 340watts per square meter onto the earth, which is fine for small scale uses. But america averages 1460 watts per second per person, so solar energy is supplementary at best. Although I did see a really cool article about a solar power plant that used a huuuuge mirror array to focus the suns energy into super-heating a salt resevoir until it liquified, then cooling it with water, creating steam to spin turbines. I think it said it was powering an entire city, forget where. very cool stuff.


There are two plants that you are talking about.

One of them is in spain, powering most of Madrid.
The other is in my homestate of California, in Death Valley powering San Diego (I think).

Here's the link: http://en.wikipedia.org/wiki/Concentrated_solar_power

I saw a show on Naked Science about it, it's really just fascinating, and IIRC creating these plants is less harmful to the environment because the process of producing photovoltaic cells uses petroleum based plastic (or something...? I can't remember).

From what you remember, which plant is generally more cost efficient?

Also, I saw a show where Michio Kaku talked about creating solar plants in space. He said the most efficient way to gather as much energy as possible is to have a a giant, hollow sphere of photovoltaics surrounding the sun. There would be an empty band along the plane of the planet's orbit's around the sun, so all the planets get light from the sun normally, but there is a bowl shape around the poles that capture energy and transmit it to earth via microwave radiation.
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Posts: 33
Yes, I remember this. It was supposed to be a "near future" type of thing, with an AI running it, making the small adjustments (on the magnets and other auxilary crap) to stop the damn thing dropping an atom too low and splattering itself. I, for one, find ion-thruster-powered spaceships orbiting a super-dense black hole in the centre of our galaxy to be more funnerer.

Sciiiieeeenceeee!

EDIT: Hah, didn't notice the de-railment to energy and spaceflight. My personal choice would be He3, essentially a compound or some !@#$ which the Moon is largely comprised of, the way it is extracted or utilised I've forgotten by now, but the point remains, there's enough He3 on the Moon to power the Earth into the projected future for thousands of years, population and increased power needs accounted for. Or, it's just one of those series that tries to make you think we aren't royally !@#$ed because we lack the will to harvest that big ol' ball of fire just chilling a few lightyears away.

Bleh.
Edited by Catatafish on 9/18/2011 4:37 AM PDT
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Community Manager
Posts: 1,261


Politicians are very forward-thinking....about how much money they are going to make from oil lobbyists!

I agree solar energy is not used enough. But it takes a lot of surface area to make it effective. The sun spits about 340watts per square meter onto the earth, which is fine for small scale uses. But america averages 1460 watts per second per person, so solar energy is supplementary at best. Although I did see a really cool article about a solar power plant that used a huuuuge mirror array to focus the suns energy into super-heating a salt resevoir until it liquified, then cooling it with water, creating steam to spin turbines. I think it said it was powering an entire city, forget where. very cool stuff.


There are two plants that you are talking about.


There are many more than two!

http://en.wikipedia.org/wiki/List_of_solar_thermal_power_stations
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Posts: 406
This doesn't really make sense to me, you just travel around earth at the speed of light for 18 days or whatever and get out, if you're even alive at that point and it's 18 days later. I can't see speed ever affecting actual time.
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Posts: 3,739
well said, Astrai. I grappled with relativity for a long time before I finally said "well it makes sense, damn it."

UGH I am such a different breed of nerd lol
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