Travel to the end of the Universe

About a week ago, I had a contest on io9 calling for questions about the universe. I got one that seems, on first blush, to be kind of silly, but on further inspection is kind of awesome. Cameron asks:

What impact will the expanding universe have on humans exploring space?

Locally, not at all, but if you wanted to travel to other galaxies — especially the most distant galaxies — everything gets crazy.

I’m going to do my actual (non-technical) column on io9 answering this this Thursday, but I wanted to give a heads-up to the truly devoted. There are at least 4 issues:

  1. Time slows when you’re going fast.

    The issue is in how we might imagine traveling over interstellar distances. We’re human, which means that we need to slowly get up to speed, accelerating at a rate of 1g until we’re going close to the speed of light, and then decelerating at the tail end of the trip.

    Of course, if we’re going close to the speed of light, then Einstein tells us that time appears to slow. I already did a technical post on this, but only to the nearest stars.

    In other words, to travel 100 light-years, even though you’ll never hit the speed of light (let alone break it), according to your personal clock, much than 100 years will have elapsed.

  2. Distant galaxies are a moving target.

    Just because a galaxy is 5 billion light years away now doesn’t mean that it would take 5 billion years to get there, even at the speed of light. Every day these distant galaxies get further and further away.

  3. An expanding universe drags your ship.

    The expanding universe slows down your ship, just from the expansion of spacetime itself. It’s the same thing that causes light to get redder and redder (lower and lower energy) as time goes on. Just to keep at a constant speed, you need to keep your foot on the gas.

  4. In an accelerating universe, there’s an ultimate horizon.

    We live in a universe of dark energy, which means that the universe is accelerating, and there is a particle horizon beyond which can’t ever reach, no matter how quickly we travel.

This is to say nothing of other potential weird effects like the fact that you can’t be sure of what you’ll reach when you get to your destination (or even if the galaxy hasn’t already been destroyed in the collision), or that in a curved universe, you and a friend might head off in different directions and eventually meet.

This question got me so excited that I did the detailed calculation to figure it out. This goes well beyond what I’d normally post here, but if you’d like to have a look:

[Technical Calculations]

There are some awesome results, including:

  • You’d need a matter-antimatter drive the size of the moon to carry about 500kg of cargo to the edge of the universe
  • It would only take about 45 years (ship time) to reach the edge of the universe.

The detailed numerical calculations were done using a Python code, which I’m happy to share with you.

This code generated the figure up at the top which shows (for arbitrary distances), how long it takes to get there according to both the rocketship, and to the cosmos generally.

I hope you’ve enjoyed my nerdsplosion, and keep an eye out on Thursday of this week!

Update: 6/20 My greatly expanded version of this is up on io9!

-Dave

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4 Responses to Travel to the end of the Universe

  1. Stu says:

    This is great! You certainly have a crazy hobby. Thanks for the Python code, I am going to give it a shot.

  2. tonyon says:

    …interstellar travel constant acceleration (Sun-Deneb: 1000g)… Earth…the 2 ships that will go formation flying for mutual assistance if there are problems…indestructible estructures made of Hexapentas materials, awaiting in airport the arrival of passengers… Dat 1: zero-speed… THE SHIPS TAKEOFF ►… navigation computer place on screen the ship in the center of sphere…spherical\tridimensional\spatial Heading: Deneb… Antimatter rocket engines…ON… Here we go…goooooo!…1g…10g…100g…constant acceleration cruise: 1000g (9.8 kms/sec²)… Inside of living areas (the same as going submerged in water: constant acceleration downwards…less…constant thrust, constant acceleration, from water upwards)…the gravitational transformers, perfectly synchronized with acceleration, running: 1000g constant acceleration toward the floor ↓↓(motors)↓↓…less…999g constant acceleration toward the ceiling ↑↑(gravitational transformers)↑ = 1g constant acceleration toward the floor↓… 8.5 hours: light-speed = 1c…the fusion reactor as an artificial sun illuminating the immense Life Support Gardens to lowering, from their comfortable appartments, cheerful passage to the pool…the electromagnetic shield anti-radiation…antigravity fields generator run forwards, working: light objects away from the path of the ship, and trajectory ship away from the heavy objects…superluminal-speed > 1c… 42.5 hours: reaches hyperluminal-speed = 5c… Day 508: Half Journey…1000 light years…high hyperluminal-speed = 1435.39c… OFF engines…a few minutes of weightlessness during maneuver…the ship rotates 180º around its axis…motors ON again and… ◄starts to brake… Day 1017 (2.79 years): End Path party…2000 light years…zero-speed… The forever young passage of the 1st Immortal Generation (3D Bioprinting…Telomerase…modified Biological Timers…) disembarks at destination: an extra-stellar planet came errant to orbit of Deneb giant.

  3. tonyon says:

    …interplanetary travel (to the asteroid of the end of the world)… asteroid Toutatis…how to move a mass of 40,000 million Tm?. Obviously the chemical rockets are not useful. Only a few nuclear charges will be enough for gives it the shove. At Space, on having not air, there is not expansive wave. Only will arrive to it the radiations, gamma rays, etc, which volatilize the impact surface of those radiations and eject the superficial material as a jet propulsion. Subterranean nuclear charge: destruction of the asteroid. Nuclear charge very near from the surface: deflection of the asteroid. If asteroid it is small, as DA-14, perhaps being enough with a single nuclear charge…or less drastic for give them thrust: to install on asteroid a nuclear electric generator. A spatial-catapult, as the aircraft´s carrier deck but with a linear electric motor, some over rails tip cars, or fastened to an endless belt, launching rocks and/or plastic bags filled with ground… A spatial-sling, a revolving tube at high revolutions, rocks entering by the gyration axis and go out by the tube sent away at big speed towards the Space… Thrust by action/reaction for deflecting it with time… If asteroid it is large, as Toutatis, probably would be necessary a few stepped nuclear charges for moving it. War ballistic missiles that there are, they are not useful, are designed for go away from continent to continent… Only can be useful a rocket that can to put the charge at interplanetary orbit, as the multi-phase which put satellites in geostationary orbit (is necessary have them already prepared in a Spatial-Command with all the nuclear weapons that there are in the World controlled and preserved by an International Organism, only for that)…(“Doomsday asteroid”: W. Cox and H. Chestek). Not only will can deflecting them from their trajectories of collision with Earth, but besides…they will be placed in geostationary orbit for to exploit their wealth of minerals, water, oxygen, nitrogen for the air and agriculture of Vital Support Gardens, etc. They will be utilized as ships, for to travel in them to the Solar System boundaries…as a “buses” fleet, going over there in one and if want to return or go away to other direction await the approaching of suitable asteroid to transferring… Drilling them by the center, as a gyratory without bone olive, with a fusion reactor in the center which it will gives the light and heat as an artificial sun… Immense subterranean Gardens which will produce the air and food… At to look over there at high…will se to those other cities “downwards head”…

  4. tonyon says:

    …interstellar travel (thousands G of constant acceleration)… gravitation, dimensions and inertia: the Matter… The electromagnetic radiation: quanta (pieces) of energy in discrete amounts (minimum and independents), photons, which move in waves… Why energy quanta (photons) are attracted by gravitational fields of “stellar lenses” curving their trajectories and move on?…go ahead because they have inertia…and are attracted because the Energy also has Gravitation, but does not manifest because it no emits Graviton, or emits in imperceptible degree, because it has to be condensed enough like in matter for that, but it is sensitive to Gravitation from Matter emits… Energy and Gravitation “associated”…and…the Gravitational Force is another manifestation, unknown yet, from Energy…(no “curvature” of that called “space-time” relativistic)…beyond any exorbitant density/temperature of the Energy…Gravity (→attraction←)…becomes Antigravity (←repulsion→)…Big-Bang!!…its particle exchange, the theoretical Graviton yet…maybe “quanta of gravitational energy”… The Energy (e=mc²) is sensitive to Gravitation but hardly emits Graviton… The Matter, which is condensed Energy (m=e/c²), emits now Gravitons proportionally to its density… The Matter with normal density, naturally, emits few Gravitons (weak intensity of gravitational force). But…if someday could transform some of matter, not in Energy by annihilation with antimatter but entirely in Gravitational Force with an exponential Gravitons emission…would have a way to amplify the Gravitational Force a certain amount of mass…gravitational transformers…for spacecrafts to thousands G of constant acceleration…

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