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A massive object like the Earth will bend space-time, and cause objects to fall toward it. More When giving the coordinates for a location, most people provide the latitude, longitude and perhaps altitude. But there is a fourth dimension often neglected: time. The combination of the physical coordinates with the temporal element creates a concept known as space-time, a background for all events in the universe. "In physics, space-time is the mathematical model that combines space and time into a single interwoven continuum throughout the universe," Eric Davis, a physicist who works at the Institute for Advanced Studies at Austin and with the Tau Zero Foundation, told Space.com by email. Davis specializes in faster-than-light space-time and anti-gravity physics, both of which use Albert Einstein's general relativity theory field equations and quantum field theory, as well as quantum optics, to conduct lab experiments. "Einstein's special theory of relativity, published in 1905, adapted [German mathematician] Hermann Minkowski's unified space-and-time model of the universe to show that time should be treated as a physical dimension on par with the three physical dimensions of space — height, width and length — that we experience in our lives," Davis said. [Einstein's Theory of Relativity Explained (Infographic)] "Space-time is the landscape over which phenomena take place," added Luca Amendola, a member of the Euclid Theory Working Group (a team of theoretical scientists working with the European Space Agency's Euclid satellite) and a professor at Heidelberg University in Germany. "Just as any landscape is not set in stone, fixed forever, it changes just because things happen — planets move, particles interact, cells reproduce," he told Space.com via email. The idea that time and space are united is a fairly recent development in the history of science. "The concepts of space remained practically the same from the early Greek philosophers until the beginning of the 20th century — an immutable stage over which matter moves," Amendola said. "Time was supposed to be even more immutable because, while you can move in space the way you like, you cannot travel in time freely, since it runs the same for everybody." In the early 1900s, Minkowski built upon the earlier works of Dutch physicist Hendrik Lorentz and French mathematician and theoretical physicist Henri Poincare to create a unified model of space-time. Einstein, a student of Minkowski, adapted Minkowski's model when he published his special theory of relativity in 1905. "Einstein had brought together Poincare's, Lorentz's and Minkowski's separate theoretical works into his overarching special relativity theory, which was much more comprehensive and thorough in its treatment of electromagnetic forces and motion, except that it left out the force of gravity, which Einstein later tackled in his magnum opus general theory of relativity," Davis said. In special relativity, the geometry of space-time is fixed, but observers measure different distances or time intervals according to their own relative velocity. In general relativity, the geometry of space-time itself changes depending on how matter moves and is distributed. "Einstein's general theory of relativity is the first major theoretical breakthrough that resulted from the unified space-time model," Davis said. General relativity led to the science of cosmology, the next major breakthrough that came thanks to the concept of unified space-time. "It is because of the unified space-time model that we can have a theory for the creation and existence of our universe, and be able to study all the consequences that result thereof," Davis said. He explained that general relativity predicted phenomena such as black holes and white holes. It also predicts that they have an event horizon, the boundary that marks where nothing can escape, and the point of singularities at their center, a one dimensional point where gravity becomes infinite. General relativity could also explain rotating astronomical bodies that drag space-time with them, the Big Bang and the inflationary expansion of the universe, gravity waves, time and space dilation associated with curved space-time, gravitational lensing caused by massive galaxies, and the shifting orbit of Mercury and other planetary bodies, all of which science has shown true. It also predicts things such as warp-drive propulsions and traversable wormholes and time machines. "All of these phenomena rely on the unified space-time model," he said, "and most of them have been observed." An improved understanding of space-time also led to quantum field theory. When quantum mechanics, the branch of theory concerned with the movement of atoms and photons, was first published in 1925, it was based on the idea that space and time were separate and independent. After World War II, theoretical physicists found a way to mathematically incorporate Einstein's special theory of relativity into quantum mechanics, giving birth to quantum field theory. "The breakthroughs that resulted from quantum field theory are tremendous," Davis said. The theory gave rise to a quantum theory of electromagnetic radiation and electrically charged elementary particles — called quantum electrodynamics theory (QED theory) — in about 1950. In the 1970s, QED theory was unified with the weak nuclear force theory to produce the electroweak theory, which describes them both as different aspects of the same force. In 1973, scientists derived the quantum chromodynamics theory (QCD theory), the nuclear strong force theory of quarks and gluons, which are elementary particles. In the 1980s and the 1990s, physicists united the QED theory, the QCD theory and the electroweak theory to formulate the Standard Model of Particle Physics, the megatheory that describes all of the known elementary particles of nature and the fundamental forces of their interactions. Later on, Peter Higgs' 1960s prediction of a particle now known as the Higgs boson, which was discovered in 2012 by the Large Hadron Collider at CERN, was added to the mix. Experimental breakthroughs include the discovery of many of the elementary particles and their interaction forces known today, Davis said. They also include the advancement of condensed matter theory to predict two new states of matter beyond those taught in most textbooks. More states of matter are being discovered using condensed matter theory, which uses the quantum field theory as its mathematical machinery. "Condensed matter has to do with the exotic states of matter, such as those found in metallic glass, photonic crystals, metamaterials, nanomaterials, semiconductors, crystals, liquid crystals, insulators, conductors, superconductors, superconducting fluids, etc.," Davis said. "All of this is based on the unified space-time model." Scientists are continuing to improve their understanding of space-time by using missions and experiments that observe many of the phenomena that interact with it. The Hubble Space Telescope, which measured the accelerating expansion of the universe, is one instrument doing so. NASA's Gravity Probe B mission, which launched in 2004, studied the twisting of space-time by a rotating body — the Earth. NASA's NuSTAR mission, launched in 2012, studies black holes. Many other telescopes and missions have also helped to study these phenomena. On the ground, particle accelerators have studied fast-moving particles for decades. "One of the best confirmations of special relativity is the observations that particles, which should decay after a given time, take in fact much longer when traveling very fast, as, for instance, in particle accelerators," Amendola said. "This is because time intervals are longer when the relative velocity is very large." Future missions and experiments will continue to probe space-time as well. The European Space Agency-NASA satellite Euclid, set to launch in 2020, will continue to test the ideas at astronomical scales as it maps the geometry of dark energy and dark matter, the mysterious substances that make up the bulk of the universe. On the ground, the LIGO and VIRGO observatories continue to study gravitational waves, ripples in the curvature of space-time. "If we could handle black holes the same way we handle particles in accelerators, we would learn much more about space-time," Amendola said. Will scientists ever get a handle on the complex issue of space-time? That depends on precisely what you mean. "Physicists have an excellent grasp of the concept of space-time at the classical levels provided by Einstein's two theories of relativity, with his general relativity theory being the magnum opus of space-time theory," Davis said. "However, physicists do not yet have a grasp on the quantum nature of space-time and gravity." Amendola agreed, noting that although scientists understand space-time across larger distances, the microscopic world of elementary particles remains less clear. "It might be that space-time at very short distances takes yet another form and perhaps is not continuous," Amendola said. "However, we are still far from that frontier." Today's physicists cannot experiment with black holes or reach the high energies at which new phenomena are expected to occur. Even astronomical observations of black holes remain unsatisfactory due to the difficulty of studying something that absorbs all light, Amendola said. Scientists must instead use indirect probes. "To understand the quantum nature of space-time is the holy grail of 21st century physics," Davis said. "We are stuck in a quagmire of multiple proposed new theories that don't seem to work to solve this problem." Amendola remained optimistic. "Nothing is holding us back," he said. "It's just that it takes time to understand space-time." Black Hole Quiz: How Well Do You Know Nature's Weirdest Creations? Copyright 2016 SPACE.com, a Purch company. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.

Millis M.G.,Tau Zero Foundation
JBIS - Journal of the British Interplanetary Society | Year: 2010

Estimates for the earliest launch dates for interstellar missions are found by comparing propulsion energy to extrapolations of world energy. World energy production and growth rate are extracted from 1980-2007 data (1020 Joules in 2007+1.9 ±1.7%/ yr). The proportion of energy available for space missions is estimated by comparing total USA energy to Space Shuttle propulsion energy (1:10-6). The uncertainty ranges in growth and commitment are considerable, and the resulting predictions should be treated accordingly. Mission energy is calculated using both the ideal case of just kinetic energy, and a rocket with 106 s Isp . Two mission scenarios are considered: launching a minimal colony ship (107 kg) where destination and mission duration are irrelevant, and sending a probe to Alpha Centauri, where the mission duration is set to a long tolerance of 75 years. For the Centauri probe, two calculations are performed: determining mission date corresponding to a vehicle mass of 103 kg, and the reciprocal - determining the maximum mass corresponding to available energy. It is found that the kinetic energy for the colony ship is nominally achievable around the year 2200, and its rocket version around 2500. The kinetic energy for the 103 kg Centauri probe is nominally achievable around 2400, and its rocket version around 2500. From energy growth extrapolations, the maximum mass that could be sent on the Centauri probe mission in 2007 is 0.8 kg when considering only kinetic energy, and 0.1 kg when considering a rocket. Mass capacity is directly proportional to world energy production and follows the same growth thereafter. Additionally, an examination of the incessant obsolescence postulate (where newer probes pass older probes) is argued to be irrelevant in all but the case where interstellar flight is a race, and then it is only valid for a finite time before advancing thresholds are reached. Other procrastinations are also examined and recommendations for next-steps are offered. All key factors are indentified for other researchers who wish to reassess these findings. Source

Millis M.G.,Tau Zero Foundation
JBIS - Journal of the British Interplanetary Society | Year: 2010

Recurring patterns from history are applied to diagnose recent events in civil space activities and then to predict events and opportunities through 2025. NASA's "Vision for Space Exploration" (2004-2010), is indicative of the "pride before the fall" of incumbent leaders when faced with new challenges. In this pattern, the incumbent will falter and other service providers will rise in prominence, which in turn, changes the character of the activity. In the case of civilian space activities, major change agents include robotic instead of human activities, entrepreneurial joy rides, commercial launch services, and space programmes in multiple countries. Another influential factor is that Federal funding for the US space programme has remained steady, but insufficient to complete the "von Braun visions" which defined the "space age." Future scenarios, based on historic patterns, suggest that space activities will become decentralised and diverse, with several different types of organisations filling different niches of the overall possibilities. It is predicted that by 2015 citizen joyrides will be common and private rovers will be exploring the Moon. By 2020, commercial orbiting hotels will exist and national space programmes will be attempting to work together to build international human outposts on the Moon and Mars, and will be working to protect Earth from doomsday asteroids. By 2025, the rise of artificial intelligence combined with growing robotic prowess will enable construction of human outposts on Mars before any humans arrive. And lastly, an unpredictable wild card is if new propulsion physics is discovered that can create acceleration fields and/or faster-than-light drives. Within these scenarios, opportunities are identified. Source

Gilster P.A.,Tau Zero Foundation
JBIS - Journal of the British Interplanetary Society | Year: 2013

The ambitious title of the 100 Year Starship study will resonate with the public, a fact that requires the recipient of the DARPA grant to use communicators who can follow a careful strategy as they bring this vision to the Internet and other outlets. It will be necessary to spur public engagement and sustain the 'buzz' that will help the organization develop its ideas. This paper examines these issues in the context of the author's long involvement with Centauri Dreams, a Web site devoted to presenting interstellar flight to a broad, general audience. Central to the presentation of the starship idea is the advocacy of long-term thinking and the value of spin-off research by placing the goal of a starship in the context of other human activities that have transcended the lifetime of individual participants. Teaching cross-generational responsibility will invoke issues of history, economics and philosophy in addition to the technology issues raised by a journey of this magnitude. The best communicators for this role will be generalists who can connect such widely dispersed disciplines. Key to the study is the development of a Web presence that uses the Internet with caution. Certain Internet myths including 'the wisdom of crowds' and resistance to top-down editing will compromise the project. The benefits and drawbacks of social networking will be discussed in this context. A strong editorial voice willing to cull public responses to maintain high standards in the resulting discussions is essential. Furthermore, a high standard of reporting demands the presentation of research without associated hype and a level of discourse that educates but does not patronize its audience. Careful citation of relevant research and a willingness to set the bar of discussion high will result in feedback from researchers and the public that, with the help of strenuous moderation, will build a database of thirdparty ideas that will engage interest and add materially to the value of the overall research. Source

Gilster P.,Tau Zero Foundation
JBIS - Journal of the British Interplanetary Society | Year: 2013

Before our species can begin interstellar exploration, a Solar System-wide infrastructure will need to be in place. Driving its construction will be two realities: 1) We will need to develop the technologies to alter the trajectories of Earth-crossing objects as a means of planetary security; 2) Our drive to understand our place in the universe will impel us to explore ever more distant targets to learn whether or not life exists elsewhere. Interstellar expansion is not likely to be sudden and disruptive but an evolutionary progression through a series of ever more distant targets that satisfy these imperatives. Exploration of the outer planets will search for life in sub-surface oceans on venues as distinct as Europa, Triton and numerous Kuiper Belt objects. Understanding the factors that disrupt the Oort Cloud will lead us to the study of what Freeman Dyson calls "iceteroids" and the possibility of exotic life even there. Rogue planets moving through interstellar space without stars are under investigation, with several candidate objects already identified. Before we reach even the nearest stars, we will examine these and consider the possibility of faint brown dwarfs in nearby space. Ultimately, our journey into the Orion Arm will witness many stops along the way. The Oort Cloud may extend halfway to Alpha Centauri and our dispersal can be gradual as we move between our own system and the possibly overlapping cometary cloud around the Alpha Centauri stars. Such "slow boat" migration may take tens of millennia but involves no technologies inconsistent with known physics. Source

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