Intergalactic travel
Encyclopedia
Intergalactic travel is space travel between galaxies
. Due to the relatively enormous distances between our own galaxy and even its closest neighbors, any such venture would be far more technologically demanding than even interstellar travel
. In comparison, intergalactic distances are roughly one-million fold (six orders of magnitude) greater than their interstellar counterparts.
ability and is considered pure science fiction
. It would require the available means of propulsion
to become advanced far beyond what is currently thought possible to engineer in order to bring a large craft close to the speed of light
. While it takes light approximately 2.54 million years to traverse the gulf of space between Earth and the Andromeda Galaxy
, it would take an arbitrarily short amount of time for a traveler at relativistic speed due to the effects of time dilation
; the time experienced by the traveler depends both on velocity, being anything less than the speed of light, and distance traveled (length contraction
).
Unless the craft were capable of reaching extreme relativistic speeds, another obstacle would be to navigate
the spacecraft between galaxies and succeed in reaching any chosen galaxy, star, planet or other body, as this would need an understanding of galactic movements and their coordination that is as of yet not understood.
In addition, the craft would have to be of considerable size and, without reaching speeds with noteworthy relativistic effect as mentioned above, it would also need a life support system and structural design able to support human life through thousands of generations and last the millions of years required, including the propulsion system—which would have to work perfectly the millions of years after it was built to slow down the machine for its final approach.
Even for unmanned probes which would be much lighter in mass, the problem exists that the information they send can only travel at light speed, which would mean millions of years just to receive the data they send.
Current physics
states that an object within space-time cannot exceed the speed of light, which seemingly limits any object to the millions of years it would at best take for a craft traveling near the speed of light
to reach any remote galaxy. Science fiction
frequently employs speculative concepts such as wormholes and hyperspace
as more practical means of intergalactic travel to work around this issue.
of the Milky Way
, and are traveling out into intergalactic space. A theory for their existence is that the supermassive black hole
at the center of Milky Way
ejects stars from the galaxy at a rate of about one every hundred thousand years. By 2010, sixteen hypervelocity stars had been observed. Intergalactic dust
is also thought to be ejected from galaxies, and has been observed in intergalactic space.
Galaxy
A galaxy is a massive, gravitationally bound system that consists of stars and stellar remnants, an interstellar medium of gas and dust, and an important but poorly understood component tentatively dubbed dark matter. The word galaxy is derived from the Greek galaxias , literally "milky", a...
. Due to the relatively enormous distances between our own galaxy and even its closest neighbors, any such venture would be far more technologically demanding than even interstellar travel
Interstellar travel
Interstellar space travel is manned or unmanned travel between stars. The concept of interstellar travel in starships is a staple of science fiction. Interstellar travel is much more difficult than interplanetary travel. Intergalactic travel, or travel between different galaxies, is even more...
. In comparison, intergalactic distances are roughly one-million fold (six orders of magnitude) greater than their interstellar counterparts.
The difficulties of intergalactic travel
Intergalactic travel, as it pertains to humans, is impractical by modern engineeringEngineering
Engineering is the discipline, art, skill and profession of acquiring and applying scientific, mathematical, economic, social, and practical knowledge, in order to design and build structures, machines, devices, systems, materials and processes that safely realize improvements to the lives of...
ability and is considered pure science fiction
Science fiction
Science fiction is a genre of fiction dealing with imaginary but more or less plausible content such as future settings, futuristic science and technology, space travel, aliens, and paranormal abilities...
. It would require the available means of propulsion
Spacecraft propulsion
Spacecraft propulsion is any method used to accelerate spacecraft and artificial satellites. There are many different methods. Each method has drawbacks and advantages, and spacecraft propulsion is an active area of research. However, most spacecraft today are propelled by forcing a gas from the...
to become advanced far beyond what is currently thought possible to engineer in order to bring a large craft close to the speed of light
Speed of light
The speed of light in vacuum, usually denoted by c, is a physical constant important in many areas of physics. Its value is 299,792,458 metres per second, a figure that is exact since the length of the metre is defined from this constant and the international standard for time...
. While it takes light approximately 2.54 million years to traverse the gulf of space between Earth and the Andromeda Galaxy
Andromeda Galaxy
The Andromeda Galaxy is a spiral galaxy approximately 2.5 million light-years from Earth in the constellation Andromeda. It is also known as Messier 31, M31, or NGC 224, and is often referred to as the Great Andromeda Nebula in older texts. Andromeda is the nearest spiral galaxy to the...
, it would take an arbitrarily short amount of time for a traveler at relativistic speed due to the effects of time dilation
Time dilation
In the theory of relativity, time dilation is an observed difference of elapsed time between two events as measured by observers either moving relative to each other or differently situated from gravitational masses. An accurate clock at rest with respect to one observer may be measured to tick at...
; the time experienced by the traveler depends both on velocity, being anything less than the speed of light, and distance traveled (length contraction
Length contraction
In physics, length contraction – according to Hendrik Lorentz – is the physical phenomenon of a decrease in length detected by an observer of objects that travel at any non-zero velocity relative to that observer...
).
Unless the craft were capable of reaching extreme relativistic speeds, another obstacle would be to navigate
Navigation
Navigation is the process of monitoring and controlling the movement of a craft or vehicle from one place to another. It is also the term of art used for the specialized knowledge used by navigators to perform navigation tasks...
the spacecraft between galaxies and succeed in reaching any chosen galaxy, star, planet or other body, as this would need an understanding of galactic movements and their coordination that is as of yet not understood.
In addition, the craft would have to be of considerable size and, without reaching speeds with noteworthy relativistic effect as mentioned above, it would also need a life support system and structural design able to support human life through thousands of generations and last the millions of years required, including the propulsion system—which would have to work perfectly the millions of years after it was built to slow down the machine for its final approach.
Even for unmanned probes which would be much lighter in mass, the problem exists that the information they send can only travel at light speed, which would mean millions of years just to receive the data they send.
Current physics
Physics
Physics is a natural science that involves the study of matter and its motion through spacetime, along with related concepts such as energy and force. More broadly, it is the general analysis of nature, conducted in order to understand how the universe behaves.Physics is one of the oldest academic...
states that an object within space-time cannot exceed the speed of light, which seemingly limits any object to the millions of years it would at best take for a craft traveling near the speed of light
Speed of light
The speed of light in vacuum, usually denoted by c, is a physical constant important in many areas of physics. Its value is 299,792,458 metres per second, a figure that is exact since the length of the metre is defined from this constant and the international standard for time...
to reach any remote galaxy. Science fiction
Science fiction
Science fiction is a genre of fiction dealing with imaginary but more or less plausible content such as future settings, futuristic science and technology, space travel, aliens, and paranormal abilities...
frequently employs speculative concepts such as wormholes and hyperspace
Hyperspace (science fiction)
Hyperspace is a plot device sometimes used in science fiction. It is typically described as an alternative region of space co-existing with our own universe which may be entered using an energy field or other device...
as more practical means of intergalactic travel to work around this issue.
Natural intergalactic travel
Theorized in 1988, and observed in 2005, there are stars moving faster than the escape velocityEscape velocity
In physics, escape velocity is the speed at which the kinetic energy plus the gravitational potential energy of an object is zero gravitational potential energy is negative since gravity is an attractive force and the potential is defined to be zero at infinity...
of the Milky Way
Milky Way
The Milky Way is the galaxy that contains the Solar System. This name derives from its appearance as a dim un-resolved "milky" glowing band arching across the night sky...
, and are traveling out into intergalactic space. A theory for their existence is that the supermassive black hole
Supermassive black hole
A supermassive black hole is the largest type of black hole in a galaxy, in the order of hundreds of thousands to billions of solar masses. Most, and possibly all galaxies, including the Milky Way, are believed to contain supermassive black holes at their centers.Supermassive black holes have...
at the center of Milky Way
Milky Way
The Milky Way is the galaxy that contains the Solar System. This name derives from its appearance as a dim un-resolved "milky" glowing band arching across the night sky...
ejects stars from the galaxy at a rate of about one every hundred thousand years. By 2010, sixteen hypervelocity stars had been observed. Intergalactic dust
Intergalactic dust
Intergalactic dust is cosmic dust in between galaxies in intergalactic space. Evidence for intergalactic dust has been suggested as early as 1949, and study of it grew throughout the late 20th century. There are large variations in the distribution of intergalactic dust...
is also thought to be ejected from galaxies, and has been observed in intergalactic space.
See also
- Intergalactic space, Intergalactic stars, Intergalactic dustIntergalactic dustIntergalactic dust is cosmic dust in between galaxies in intergalactic space. Evidence for intergalactic dust has been suggested as early as 1949, and study of it grew throughout the late 20th century. There are large variations in the distribution of intergalactic dust...
- Faster-than-lightFaster-than-lightFaster-than-light communications and travel refer to the propagation of information or matter faster than the speed of light....
- Galaxies in fictionGalaxies in fictionGalaxies other than the Milky Way are popular settings for creators of science fiction, particularly those working with broad-scale space opera settings. Among the most common settings are the Andromeda Galaxy, the Magellanic Clouds, and the Triangulum Galaxy, all part of the Local Group close to...