# Space travel

According to the special relativity, an object that has a mass cannot travel at the speed of light. So nothing in this universe can travel faster than the light, especially our spacecraft which has mass. Then would it be ever possible for us to visit far off heavenly bodies in a finite (less than some 100 yrs!) time?

My doubt is that ...... for this, do we need to develop technology that take us to the space at speed greater than that of light or do we have any other way?

Note
: I am just 17 and very new to this subject even. So please ignore if I am silly at questioning the things and excuse me for my weak english :)

Last edited:

mathman
If you consider the twin paradox, space travel to distance stars (thousands of light years away) is possible. The main problem is technical - how to get the rocket ship to go close to the speed of light. Using the Lorentz transformation, the time that the space traveler spends getting to a distance star will be short (in his own reference frame). However it would be very long in the earth's frame, so that if he decided to come back to earth he would find many thousands of years have past on earth.

As posted above, the astronaut would only experience a short duration on the trip (years) whereas we at home would see him gone for centuries. I think it might still be worthwhile to send probes to stars for our future descendants. They can transmit data back to Earth when they get there. As far as sending people, there are so many dangers that it might not be worthwhile for many reasons. Even if one could get a ship up to the relativistic speeds necessary for the astronaut to experience time slow enough to reach the star in his lifetime, the danger to the ship at such high speeds would be immense. Imagine running into space debris, dust, asteroids, or a dense gaseous cloud at 99.9% of the speed of light? Your space ship would not survive the collision without an immense shield of some sort. But most likely, your ship would be annihilated. There are new ion drive engines that might one day be able to achieve 99% of the speed of light, but again, space is full of things that can impact the ship and destroy it.

You mentioned going faster than the speed of light. This is what is needed. While you can't travel through space faster than the speed of light, warp engine theories would allow you to get around this limit by using immense positive energy fields to expand space behind your ship, and immense negative energy fields to shrink the space in front of the ship, allowing you to move from one point to another without moving through space much at all (you cross over it). Using this space folding technique, no physical laws regarding the speed of light are broken (you may blow up the earth behind you and destroy the solar system, but who's counting). Of course, this is all theory, and probably not possible, but it is a fun idea to think about.

Last edited:
Chronos
Gold Member
This one of the possible solutions to Fermi's paradox. The universe could be chock full of advanced civilizations - and they are all trapped in their home star system. Interstellar travel may be prohibitively impractical and expensive. One possible solution is a wormhole generator - none of those annoying collisions with stuff between destinations. All we need are a few scientific and engineering breakthoughs.

Although it would be nice to travel near the speed of light, I think it is more likely that any trips to other stars and their planets would be strictly one way affairs. I.e something along the lines of a "city, or seed, ship" which would travel at classical velocities, take a very long time to get there, and either use advanced medical techniques to "slow down aging", or carry and sustain multiple generations, which, to my mind, seems the more likely option.

I can imagine an interstellar travel that is not that "prohibitively impractical and expensive". Consider something like nanoengineered crystal of microscopic black holes - each of the holes located near each of the atoms of the macro object. Coherent falling of the atoms into the corresponding black holes gives you the same effect as falling into the single huge black hole. Vu a la.

I like that Note at the end. I'm the same way.

Put it this way, 500 years ago we didn't think it was possible to be able to travel to the moon. We accomplished that and more. We have satellites outside our solar system now.

Although our technology isn't advanced, in a few hundred years I think we'll be able to travel to distant galaxies.

There have been schematics for deep space travel crafts since the 70s. Project Orion ran using nuclear fission. Every explosion would drive the craft further "like a vast, cosmic motorboat", as Sagan described it. The development was stopped though when there was the agreement to not test nuclear explosions in space.
Project Daedalus, like Orion, uses nuclear power. Daedalus, however, uses nuclear fusion to propel itself. These two ships could travel at about 10% the speed of light, making the time problem mostly irrelevant. They could reach the closest star in 45 years.
Another craft, one that is nowhere near a surmountable task anytime soon, would scoop the hydrogen atoms found in space like a giant, metal butterfly net and then ignite them. It could travel very near the speed of light. It could reach the center of the milky way galaxy in 21 years. On this ship, unlike Orion and Daedalus, time would slow down drastically. By the time it returned from the center of the galaxy, 10s of thousands of years would have passed.

Ryan_m_b
Staff Emeritus
One of the biggest problems with space travel is the amount of energy needed. If we had a fusion rocket then 1kg of fuel for every 1kg of ship would only burn for 100,000 seconds (a little over one day). With an antimatter rocket that number increases to 1,000,000 seconds (~10 days). If you want to get close to the speed of light (>.9c) you would need 60 parts antimatter fuel for 1 part ship, with fusion that becomes 600 parts fuel for 1 part ship. That's a HELL of a lot of energy!

Another big concern is who exactly is going to be allowed to fly/own this ship? Let's say you have an antimatter rocket massing 1,000,000 tons with 60,000,000 of antimatter capable of getting to .9c. Crash that into planet Earth and you will annihilate the biosphere and wipe out absolutely all life. Would you feel safe knowing that somewhere space cadets are flying around in rockets easily capable of snuffing out our pale blue dot?

A........Using this space folding technique, no physical laws regarding the speed of light are broken (you may blow up the earth behind you and destroy the solar system, but who's counting)...

I think this is why in earlier Star Trek ep's they talked about not being allowed to use warp engines til well past Jupiter (though this policy must have needed modification to allow story lines where urgent use of warp drive was needed). Imagine strolling along on impulse drive while the Borg threat was imminent.

On warp drive, I read somewhere that the use of it would likely cause a small black hole to sit just ahead of the ship.. hmmm Perhaps that would intercept any junk that threatened to smash into the ship, but it could also (if a long trip) add to the mass within the black hole, thus making it unstable, with regard to propulsion. Which also makes me wonder if there might be any debris floating around in hyperspace.

Ryan_m_b
Staff Emeritus
I think this is why in earlier Star Trek ep's they talked about not being allowed to use warp engines til well past Jupiter (though this policy must have needed modification to allow story lines where urgent use of warp drive was needed). Imagine strolling along on impulse drive while the Borg threat was imminent.

On warp drive, I read somewhere that the use of it would likely cause a small black hole to sit just ahead of the ship.. hmmm Perhaps that would intercept any junk that threatened to smash into the ship, but it could also (if a long trip) add to the mass within the black hole, thus making it unstable, with regard to propulsion. Which also makes me wonder if there might be any debris floating around in hyperspace.

Unfortunately there is no good ideas about how we could go about manipulating space in this manner. To create a warp drive would require a shell of exotic energy and arranging this shell would require you to locally send FTL signals to keep the shell where it is. For the same reason the space cadets wouldn't be able to steer, control or stop the ship once it is in motion. IIRC the necessary energy to make such a warp drive work would be the energy equivalent of entire galaxies!

In summary warp drive is a good option if you can;
Assemble impossible materials
Arrange them in impossible ways
Give them impossible amounts of energies
:tongue:

Unfortunately there is no good ideas about how we could go about manipulating space in this manner. To create a warp drive would require a shell of exotic energy and arranging this shell would require you to locally send FTL signals to keep the shell where it is. For the same reason the space cadets wouldn't be able to steer, control or stop the ship once it is in motion. IIRC the necessary energy to make such a warp drive work would be the energy equivalent of entire galaxies!

In summary warp drive is a good option if you can;
Assemble impossible materials
Arrange them in impossible ways
Give them impossible amounts of energies
:tongue:

Man cannot travel faster than 30mph.
If God had meant for man to fly, he would have given him airline tickets.

Man cannot travel faster than 30mph.

Completely different issue.

One is a belief, the other is based on science.

Ryan_m_b
Staff Emeritus
Man cannot travel faster than 30mph.
If God had meant for man to fly, he would have given him airline tickets.

Like Jared said this is no a scientific assessment!

In addition to my previous comments I forgot to add that if you did manage to create a warp drive you would now have the ability to make closed timelike curves. After that you may find that you run into a chronology protection conjecture as discussed here http://arxiv.org/abs/gr-qc/0204022" [Broken]

Last edited by a moderator:
According to the special relativity, an object that has a mass cannot travel at the speed of light. So nothing in this universe can travel faster than the light, especially our spacecraft which has mass. Then would it be ever possible for us to visit far off heavenly bodies in a finite (less than some 100 yrs!) time?

Maybe. One thing to point out is that the "biology" limits are easier to solve than the physics limits. There are some fundamental physics reasons why we are limited to c, but there are no fundamental physics limits that say that we couldn't re-engineer the human body to live 1000 years.

If you want to look at technologies, then immortality is an "easier" problem than trying to travel faster than light.

Ryan_m_b
Staff Emeritus
Maybe. One thing to point out is that the "biology" limits are easier to solve than the physics limits. There are some fundamental physics reasons why we are limited to c, but there are no fundamental physics limits that say that we couldn't re-engineer the human body to live 1000 years.

If you want to look at technologies, then immortality is an "easier" problem than trying to travel faster than light.

As well as the engineering nightmare of making a long-term stable ecosystem with a habitat large enough to hold it (and then crank up to a respectable speed). Then theres the social engineering problem of building a society stable enough to last thousands of years whilst maintaining their environment. Additionally theres the legal problem of what sentence would be appropriate for the Crime Against Humanity that is sticking a few million people in an asteroid sized chunk and sending them and their descendants off into the void...

Still easier than FTL engines though

Even if we did reached the speed of light, it would still take centuries for us to reach distant places, like other galaxies. But we can't reach the speed of light. It is possible for us to reach 99.99% speed of light, that way we could reach the stars. But with our current technology, I don't think we'll be able to make such a space craft any time soon. Besides we would also be travelling through time, time would run slower for us. So when we were to return back to Earth we would be in a completely different time. This would make the experience quite unpleasant. It may be possible, but it won't happen any time soon. Another way to reach far off bodies would be teleportion. There are theories that we can use blackholes and wormholes for teleportion, but it's not certain if that's possible and even if it is possible, we don't have the technology to use it.

Ryan_m_b
Staff Emeritus
Even if we did reached the speed of light, it would still take centuries for us to reach distant places, like other galaxies. But we can't reach the speed of light. It is possible for us to reach 99.99% speed of light, that way we could reach the stars. But with our current technology, I don't think we'll be able to make such a space craft any time soon. Besides we would also be travelling through time, time would run slower for us. So when we were to return back to Earth we would be in a completely different time. This would make the experience quite unpleasant. It may be possible, but it won't happen any time soon. Another way to reach far off bodies would be teleportion. There are theories that we can use blackholes and wormholes for teleportion, but it's not certain if that's possible and even if it is possible, we don't have the technology to use it.

Depends on if you actually want to come back.

If (as has been discussed on this thread) life extension/biological immortality is developed perhaps it wouldn't be such a harsh thing to leave your home for 100 years (10 years your time).

But is it possible to have a space craft that emits a periodic and controlled gravitational force that would propel space-time around it and hence creep its way to it's destination - obviously ensuring that it does not effect any normal space-time vortex' ?

I'm not quite sure how else to explain my thoughts... But maybe like a caterpillar creeps along... Would that also slow down time to such extents as mentioned above? Would this avoid the need of travelling at the speed of light?

We are working on the merging of the mysterious,weak thing called gravity with rest of the fundamental forces in hopes of knowing more at quantum level,so having a device which creates fluctuation of graviton is in my opinion far fetched for now.

If I think of it in a pseudo science way then I would apply quantum entanglement(not that this is so pseudo science but too soon for now) to accomplish this alternative to reaching relativistic speeds.

Regards,
ibysaiyan

Last edited: