Hubble Deep Space Images

what’s it expanding into?

Think fireworks.

Suppose you lived inside a balloon. As the balloon inflated, how could you imagine what outside space it expands into.

That's my problem. There must be "something" into which to expand. So what's it expanding into? If it's expanding into a "void", then the void itself is something. In your analogy, what is the balloon floating in? I'm starting to think it's a parallel universe and we are encroaching into that space.

You need to do a bit more reading, for example read up on the Alcubierre Drive.

You need to do a bit more reading, for example read up on the Alcubierre Drive.

Silliness. People read to much science fiction

Or...from a Suess-ish viewpoint, we examine atoms - which it is agreed have particles orbiting nucleii. What if our universe constitutes the atoms of an even larger creation. Do I hear a Who?

Ever since taking college level physics and learning the time travel is impossible

I am surprised. You should know that time travel is not impossible. It has been proven. Have you not heard of the time dilation effect? This has been proven as fact in numerous experiments. And it effectively proves that travel into the future is also possible.

I would concede that time travel into the past is impossible. But that's it.

I feel very small today.

For the FOURTH time I ask you- Do you think we know all there is to know about interstellar travel?

The fermi ‘paradox’ is an intellectual exercize- nothing more. For thousands of years we had no ovidence of ‘electrons’ but that did not mean they didnt exist. the same argument applies- there are probably many things we have not yet seen evidence of- but they do exist.

You sound like you read a thing or two and formuilated a rock-solid belief. This is all theory.

FTL [faster than light] travel is impossible

Einstein's theory never actually said things couldn't go faster than light. It said things *with mass* couldn't be accelerated TO the speed of light or slowed down to the speed of light (if the object was somehow already traveling faster than light.), for it would take an infinity amount of energy to do either. Objects without mass (photons, gravity waves/gravitons, tachyons) can travel at light speed.

Let us assume the existence of wormholes (or however one wishes to express a negotiable rift in the fabric of space/time). Is it not true that a distant visitation point targeted via visible light might be found to no longer exist upon one’s “arrival”?

The Fermi paradox (Fermi's paradox or Fermi-paradox) is the apparent contradiction between high estimates of the probability of the existence of extraterrestrial civilizations and the lack of evidence for, or contact with, such civilizations.

The age of the universe and its vast number of stars suggest that if the Earth is typical, extraterrestrial life should be common.[1] In an informal discussion in 1950, the physicist Enrico Fermi questioned why, if a multitude of advanced extraterrestrial civilizations exists in the Milky Way galaxy, evidence such as spacecraft or probes is not seen. A more detailed examination of the implications of the topic began with a paper by Michael H. Hart in 1975, and it is sometimes referred to as the Fermi–Hart paradox.[2] Other common names for the same phenomenon are Fermi's question ("Where are they?"), the Fermi Problem, the Great Silence,[3][4][5][6][7] and silentium universi[7][8] (Latin for "the silence of the universe"; the misspelling silencium universi is also common). There have been attempts to resolve the Fermi paradox by locating evidence of extraterrestrial civilizations, along with proposals that such life could exist without human knowledge. Counterarguments suggest that intelligent extraterrestrial life does not exist or occurs so rarely or briefly that humans will never make contact with it.

Starting with Hart, a great deal of effort has gone into developing scientific theories about, and possible models of, extraterrestrial life, and the Fermi paradox has become a theoretical reference point in much of this work. The problem has spawned numerous scholarly works addressing it directly, while questions that relate to it have been addressed in fields as diverse as astronomy, biology, ecology, and philosophy. The emerging field of astrobiology has brought an interdisciplinary approach to the Fermi paradox and the question of extraterrestrial life.

The Fermi paradox is a conflict between an argument of scale and probability and a lack of evidence. A more complete definition could be stated thus: The apparent size and age of the universe suggest that many technologically advanced extraterrestrial civilizations ought to exist. However, this hypothesis seems inconsistent with the lack of observational evidence to support it.

The first aspect of the paradox, "the argument by scale", is a function of the raw numbers involved: there are an estimated 200–400 billion[9] (2–4 ×1011) stars in the Milky Way and 70 sextillion (7×1022) in the visible universe.[10] Even if intelligent life occurs on only a minuscule percentage of planets around these stars, there might still be a great number of civilizations extant in the Milky Way galaxy alone. This argument also assumes the mediocrity principle, which states that Earth is not special, but merely a typical planet, subject to the same laws, effects, and likely outcomes as any other world.

The second cornerstone of the Fermi paradox is a rejoinder to the argument by scale: given intelligent life's ability to overcome scarcity, and its tendency to colonize new habitats, it seems likely that at least some civilizations would be technologically advanced, seek out new resources in space and then colonize first their own star system and subsequently the surrounding star systems. Since there is no conclusive or certifiable evidence on Earth or elsewhere in the known universe of other intelligent life after 13.7 billion years of the universe's history, we have the conflict requiring a resolution. Some examples of which may be that intelligent life is rarer than we think, or that our assumptions about the general behavior of intelligent species are flawed.

The Fermi paradox can be asked in two ways. The first is, "Why are no aliens or their artifacts physically here?" If interstellar travel is possible, even the "slow" kind nearly within the reach of Earth technology, then it would only take from 5 million to 50 million years to colonize the galaxy.[11] This is a relatively small amount of time on a geological scale, let alone a cosmological one. Since there are many stars older than the Sun, or since intelligent life might have evolved earlier elsewhere, the question then becomes why the galaxy has not been colonized already. Even if colonization is impractical or undesirable to all alien civilizations, large-scale exploration of the galaxy is still possible; the means of exploration and theoretical probes involved are discussed extensively below. However, no signs of either colonization or exploration have been generally acknowledged.

The argument above may not hold for the universe as a whole, since travel times may well explain the lack of physical presence on Earth of alien inhabitants of far away galaxies. However, the question then becomes "Why do we see no signs of intelligent life?" since a sufficiently advanced civilization[Note 1] could potentially be observable over a significant fraction of the size of the observable universe.[12] Even if such civilizations are rare, the scale argument indicates they should exist somewhere at some point during the history of the universe, and since they could be detected from far away over a considerable period of time, many more potential sites for their origin are within range of our observation. However, no incontrovertible signs of such civilizations have been detected.

It is unclear which version of the paradox is stronger.[Note 2] [edit]Name

In 1950, while working at Los Alamos National Laboratory, the physicist Enrico Fermi had a casual conversation while walking to lunch with colleagues Emil Konopinski, Edward Teller and Herbert York. The men discussed a recent spate of UFO reports and an Alan Dunn cartoon[13] facetiously blaming the disappearance of municipal trashcans on marauding aliens. They then had a more serious discussion regarding the chances of humans observing faster-than-light travel by some material object within the next ten years, which Teller put at one in a million, but Fermi put closer to one in ten. The conversation shifted to other subjects, until during lunch Fermi suddenly exclaimed, "Where are they?" (alternatively, "Where is everybody?")[14] One participant recollects that Fermi then made a series of rapid calculations using estimated figures (Fermi was known for his ability to make good estimates from first principles and minimal data, see Fermi problem.) According to this account, he then concluded that Earth should have been visited long ago and many times over.[14][15] [edit]Drake equation

Main article: Drake equation While numerous theories and principles are related to the Fermi paradox, the most closely related is the Drake equation. The equation was formulated by Dr. Frank Drake in 1961, a decade after the objections raised by Enrico Fermi, in an attempt to find a systematic means to evaluate the numerous probabilities involved in alien life. The speculative equation factors in: the rate of star formation in the galaxy; the fraction of stars with planets and the number per star that are habitable; the fraction of those planets which develop life, the fraction of intelligent life, and the further fraction of detectable technological intelligent life; and finally the length of time such civilizations are detectable. The fundamental problem is that the last four terms (fraction of planets with life, odds life becomes intelligent, odds intelligent life becomes detectable, and detectable lifetime of civilizations) are completely unknown. We have only one example, rendering statistical estimates impossible, and even the example we have is subject to a strong anthropic bias.

A deeper objection is that the very form of the Drake equation assumes that civilizations arise and then die out within their original solar systems. If interstellar colonization is possible, then this assumption is invalid, and the equations of population dynamics would apply instead.[16] The Drake equation has been used by both optimists and pessimists with wildly differing results. Dr. Carl Sagan, using optimistic numbers, suggested as many as one million communicating civilizations in the Milky Way in 1966, though he later suggested that the actual number could be far smaller. Pessimists, such as Frank Tipler & John D Barrow, have used pessimistic numbers and concluded that the average number of civilizations in a galaxy is much less than one.[17][Note 3] Frank Drake himself has commented that the Drake equation is unlikely to settle the Fermi paradox; instead it is just a way of "organizing our ignorance" on the subject.[18] [edit]Empirical resolution attempts

One obvious way to resolve the Fermi paradox would be to find conclusive evidence of extraterrestrial intelligence. Efforts to find such evidence have been made since 1960, and several are ongoing as of 2011.[19] As human beings do not possess interstellar travel capability, such searches are being remotely carried out at great distances and rely on analysis of very subtle evidence. This limits possible discoveries to civilizations which alter their environment in a detectable way, or produce effects that are observable at a distance, such as radio emissions. It is very unlikely that non-technological civilizations will be detectable from Earth in the near future. One difficulty in searching is avoiding an overly anthropocentric viewpoint. Conjecture on the type of evidence likely to be found often focuses on the types of activities that humans have performed, or likely would perform given more advanced technology. Intelligent aliens might avoid these "expected" activities, or perform activities totally novel to humans. [edit]Mainstream astronomy and SETI

There are two ways that astronomy might find evidence of an extraterrestrial civilization. One is that conventional astronomers, studying stars, planets, and galaxies, might serendipitously observe some phenomenon that cannot be explained without positing an intelligent civilization as the source. This has been suspected several times. Pulsars, when first discovered, were called LGMs (Little Green Men), because of the precise repetition of their pulses (they rival the best atomic clocks). Likewise Seyfert galaxies were suspected to be industrial accidents[20] because their enormous and directed energy output had no initial explanation. Eventually, natural explanations not involving intelligent life have been found for all such observations to date. Specifically, pulsars are now attributed to neutron stars, and Seyfert galaxies to an end-on view of the accretion onto the black holes, but the possibility of discovery remains.[21]

The other way astronomy might settle the Fermi paradox is through a search specifically dedicated to finding evidence of life. [edit]Radio emissions Further information: SETI, Project Ozma, Project Cyclops, Project Phoenix (SETI), SERENDIP, and Allen Telescope Array

Radio telescopes are often used by SETI projects Radio technology and the ability to construct a radio telescope are presumed to be a natural advance for technological species,[22] theoretically creating effects that might be detected over interstellar distances. Sensitive observers of the solar system, for example, would note unusually intense radio waves for a G2 star due to Earth's television and telecommunication broadcasts. In the absence of an apparent natural cause, alien observers might infer the existence of terrestrial civilization. Therefore, the careful searching of radio emissions from space for non-natural signals may lead to the detection of alien civilizations. Such signals could be either "accidental" by-products of a civilization, or deliberate attempts to communicate, such as the Communication with Extraterrestrial Intelligence's Arecibo message. A number of astronomers and observatories have attempted and are attempting to detect such evidence, mostly through the SETI organization, although other approaches, such as optical SETI, also exist.

Several decades of SETI analysis have not revealed any main sequence stars with unusually bright or meaningfully repetitive radio emissions, although there have been several candidate signals. On August 15, 1977 the "Wow! signal" was picked up by The Big Ear radio telescope. However, the Big Ear only looks at each point on the sky for 72 seconds, and re-examinations of the same spot have found nothing. In 2003, Radio source SHGb02+14a was isolated by SETI@home analysis, although it has largely been discounted by further study. There are numerous technical assumptions underlying SETI that may cause human beings to miss radio emissions with present search techniques; these are discussed below. [edit]Direct planetary observation

A composite picture of Earth at night, created with data from the Defense Meteorological Satellite Program (DMSP) Operational Linescan System (OLS). Human civilization is detectable from space. Detection and classification of exoplanets has come out of recent refinements in mainstream astronomical instruments and analysis. While this is a new field in astronomy—the first published paper claiming to have discovered an exoplanet was released in 1989—it is possible that planets which are likely able to support life will be found in the near future.

Direct evidence for the existence of life may eventually be observable, such as the detection of biotic signature gases (such as methane and oxygen)—or even the industrial air pollution of a technologically advanced civilization—in an exoplanet's atmosphere by means of spectrographic analysis.[23] With improvements in our observational capabilities, it may eventually even be possible to detect direct evidence such as that which humanity produces (see right). However, exoplanets are rarely directly observed (the first claim to have done so was made in 2004[24]); rather, their existence is usually inferred from the effects they have on the star(s) they orbit. This means that usually only the mass and orbit of an exoplanet can be deduced. This information, along with the stellar classification of its sun, and educated guesses as to its composition (usually based on the mass of the planet, and its distance from its sun), allows only for rough approximations of the planetary environment.

Prior to 2009, methods for exoplanet detection were not likely to detect life-bearing Earth-like worlds. Methods such as gravitational microlensing can detect the presence of "small" worlds, potentially even smaller than the Earth, but can only detect such worlds for very brief moments of time, and no follow-up is possible. Other methods such as radial velocity, astrometry, and the transit method allow prolonged observations of exoplanet effects, but only work with worlds that are many times the mass of Earth, at least when performed while looking through the atmosphere. These seem unlikely candidates to harbor Earth-like life. However, exoplanet detection and classification is a very active sub-discipline in astronomy, with 424 such planets being detected between 1988 and 2010,[25] and the first possibly terrestrial planet discovered within a star's habitable zone being found in 2007.[26] New refinements in exoplanet detection methods, and use of existing methods from space, (such as the Kepler Mission, launched in 2009) are expected to detect and characterize terrestrial-size planets, and determine if they are within the habitable zones of their stars. Such observational refinements may allow us to better gauge how common potentially habitable worlds are. Using methods like the Drake equation with this data would therefore allow a much better idea of how common life in the universe might be; this would have a profound influence over the expectations behind the Fermi paradox itself.

[edit]Alien constructs [edit]Probes, colonies, and other artifacts Further information: Von Neumann probe and Bracewell probe As noted, given the size and age of the universe, and the relative rapidity at which dispersion of intelligent life can occur, evidence of alien colonization attempts might plausibly be discovered. Evidence of exploration not containing extraterrestrial life, such as probes and information gathering devices, may also await discovery. Some theoretical exploration techniques such as the Von Neumann probe (a self-replicating device) could exhaustively explore a galaxy the size of the Milky Way in as little as half a million years, with comparatively little investment in materials and energy relative to the results. If even a single civilization in the Milky Way attempted this, such probes could spread throughout the entire galaxy. Evidence of such probes might be found in the solar system—perhaps in the asteroid belt where raw materials would be plentiful and easily accessed.[27]

Another possibility for contact with an alien probe—one that would be trying to find human beings—is an alien Bracewell probe. Such a device would be an autonomous space probe whose purpose is to seek out and communicate with alien civilizations (as opposed to Von Neumann probes, which are usually described as purely exploratory). These were proposed as an alternative to carrying a slow speed-of-light dialogue between vastly distant neighbours. Rather than contending with the long delays a radio dialogue would suffer, a probe housing an artificial intelligence would seek out an alien civilization to carry on a close range communication with the discovered civilization. The findings of such a probe would still have to be transmitted to the home civilization at light speed, but an information-gathering dialogue could be conducted in real time.[28]

Since the 1950s, direct exploration has been carried out on a small fraction of the solar system and no evidence that it has ever been visited by alien colonists, or probes, has been uncovered. Detailed exploration of areas of the solar system where resources would be plentiful—such as the asteroids, the Kuiper belt, the Oort cloud and the planetary ring systems—may yet produce evidence of alien exploration, though these regions are vast and difficult to investigate. There have been preliminary efforts in this direction in the form of the SETA and SETV projects to search for extraterrestrial artifacts or other evidence of extraterrestrial visitation within the solar system.[29] There have also been attempts to signal, attract, or activate Bracewell probes in Earth's local vicinity, including by scientists Robert Freitas and Francisco Valdes.[30] Many of the projects that fall under this umbrella are considered "fringe" science by astronomers and none of the projects has located any artifacts. Should alien artifacts be discovered, even here on Earth, they may not be recognizable as such. The products of an alien mind and an advanced alien technology might not be perceptible or recognizable as artificial constructs. Exploratory devices in the form of bio-engineered life forms created through synthetic biology would presumably disintegrate after a point, leaving no evidence; an alien information gathering system based on molecular nanotechnology could be all around us at this very moment, completely undetected. The same might be true of civilizations that actively hide their investigations from us, for possible reasons described further in this article. Also, Clarke's third law suggests that an alien civilization well in advance of humanity's might have means of investigation that are not yet conceivable to human beings. [edit]Advanced stellar-scale artifacts

Further information: Dyson sphere, Kardashev scale, Alderson disk, Matrioshka brain, Stellar engine

A variant of the speculative Dyson sphere. Such large scale artifacts would drastically alter the spectrum of a star. In 1959, Freeman Dyson observed that every developing human civilization constantly increases its energy consumption, and theoretically, a civilization of sufficient age would require all the energy produced by its star. The Dyson Sphere was the thought experiment that he derived as a solution: a shell or cloud of objects enclosing a star to harness as much radiant energy as possible. Such a feat of astroengineering would drastically alter the observed spectrum of the star involved, changing it at least partly from the normal emission lines of a natural stellar atmosphere, to that of a black body radiation, probably with a peak in the infrared. Dyson himself speculated that advanced alien civilizations might be detected by examining the spectra of stars, searching for such an altered spectrum.[31]

Since then, several other theoretical stellar-scale megastructures have been proposed, but the central idea remains that a highly advanced civilization—Type II or greater on the Kardashev scale—could alter its environment enough as to be detectable from interstellar distances. However, such constructs may be more difficult to detect than originally thought. Dyson spheres might have different emission spectra depending on the desired internal environment; life based on high-temperature reactions may require a high temperature environment, with resulting "waste radiation" in the visible spectrum, not the infrared.[32] Additionally, a variant of the Dyson sphere has been proposed which would be difficult to observe from any great distance; a Matrioshka brain is a series of concentric spheres, each radiating less energy per area than its inner neighbour. The outermost sphere of such a structure could be close to the temperature of the interstellar background radiation, and thus be all but invisible.

I’ve actually studied Relativity (the real stuff, not just Special Relativity), and the math says that space and time is curved. It’s also been observed on many occasions with light being bent around stars.

That's my problem. There must be "something" into which to expand. So what's it expanding into?

According to the Big Bang theory, there is absolutely nothing outside the expanding universe. All that is is being created within the expansion. Furthermore, there is no one center to the expansion. Everywhere is the center. ie, every point within the universe see everything else expanding away from it at the same (accelerating) rate.

For the FOURTH time I ask you- Do you think we know all there is to know about interstellar travel?

What I am saying is that there is nothing in physics that would lead me to believe that the question you proposed is even relevant.

It has been proven. Have you not heard of the time dilation effect?

Moving clocks (relative to the observer) tick slower. It's been proven right here on Earth with highly accurate cesium clocks. central_va knows little to nothing about quantum physics or relativity. Let's not even approach Strings or multi-dimensinal geometry.

It is hard to accept that we are alone in the universe and that interstellar, let alone intergalactic, travel is impossible. Accept we must. I am not saying that our solar system isn’t worth exploring, but that’s it. The laws of physics and the human condition say we are stuck here.

Moving clocks (relative to the observer) tick slower. It's been proven right here on Earth with highly accurate cesium clocks. central_va knows little to nothing about quantum physics or relativity. Let's not even approach Strings or multi-dimensinal geometry.

I know about those things, the problem I have is with the belief that somehow this will translate into some kind of space travel. That is the ridiculous(fantasy) part of this.

...there is absolutely nothing outside the expanding universe.

That's where my brain starts a meltdown. I can't imagine "nothing" and its ability to have something expand into it. I've just got to accept the fact that I don't have the tools of a Hawking, drop this topic, and go back to thinking about sex.

A whole new perspective.

Thanks for the great post!

One thing I always appreciated about Einstein was his willingness to admit that he didn’t know everything. He was a true theoretical scientist who didn’t accept things as fact until proven.

He believed that gravity bent light but spent years seeking proof. (Many others also sought and provided proof)