what observational evidence supports the expansion of the universe?
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The earliest and most direct observational evidence of the validity of the theory are the expansion of the universe according to Hubble's law (as indicated by the redshifts of galaxies), discovery and measurement of the cosmic microwave background and the relative abundances of light elements produced by BBN.
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The Friedmann equation which models the expanding universe has a parameter k called the curvature parameter which is indicative of the rate of expansion and whether or not that expansion rate is increasing or decreasing. It indicates the future fate of the universe.
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The Short Answer: The big bang is how astronomers explain the way the universe began. It is the idea that the universe began as just a single point, then expanded and stretched to grow as large as it is right now (and it could still be stretching).
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Observational astronomy is a division of astronomy that is concerned with recording data about the observable universe, in contrast with theoretical astronomy, which is mainly concerned with calculating the measurable implications of physical models.
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Tests of Big Bang: The CMB. The Big Bang theory predicts that the early universe was a very hot place and that as it expands, the gas within it cools. Thus the universe should be filled with radiation that is literally the remnant heat left over from the Big Bang, called the “cosmic microwave background", or CMB.
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The Big Bang theory is a cosmological model of the observable universe from the earliest known periods through its subsequent large-scale evolution. ... Detailed measurements of the expansion rate of the universe place the Big Bang at around 13.8 billion years ago, which is thus considered the age of the universe.
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As dark energy causes the universe to expand ever-faster, it may spur some very distant galaxies to apparently move faster than the speed of light. ... Over and over (and over and over) we're told the supreme iron law of the universe: Nothing — absolutely nothing — can go faster than the speed of light. Done.
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A scientific theory must be supported with empirical evidence.
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String theory (or, more technically, M-theory) is often described as the leading candidate for the theory of everything in our universe. But there's no empirical evidence for it, or for any alternative ideas about how gravity might unify with the rest of the fundamental forces.
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All in all, Hubble reveals an estimated 100 billion galaxies in the universe or so, but this number is likely to increase to about 200 billion as telescope technology in space improves, Livio told Space.com.
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The Big Bang theory explains where all the hydrogen and helium in the universe came from. ... Early on, the whole universe was dense enough to be completely opaque. But at a time roughly 380,000 years after the Big Bang, expansion spread everything out enough to make the universe transparent.
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Almost all other galaxies we can observe are moving away from us with the expansion of the universe, according to the Hubble statement. ... So, from the perspective of Earth, we see the galaxy moving toward us, even though other galaxies in the same cluster appear to be moving away from us at high velocities.
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In the 1980s, astronomers turned to multiverse theory to explain the “luckily small” amount of dark energy in our universe. According to cosmologist's theories, this small amount of dark energy appeared to enable our universe to host life, while most universes in the multiverse couldn't.
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Answer: Theory and fact (or observation) really go hand-in-hand. You really cannot have one without the other. Observations are used to support theories, while theories are the connections between what observations tell us about astrophysical objects and what the physical understanding of an object is.
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A scientific fact is something that can be observed in the universe by multiple individuals and is repeatably observable. A scientific theory is a generalized explanation of observed patterns in scientific facts or data that can successfully make predictions about other observations we can make about he universe.
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The universe is expanding at accelerated rate. The galaxies outside of our own are moving away from us, and the ones that are farthest away are moving the fastest. This means that no matter what galaxy you happen to be in, all the other galaxies are moving away from you. The universe is expanding at accelerated rate.
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Summary. Multiple types of evidence support the theory of evolution: Homologous structures provide evidence for common ancestry, while analogous structures show that similar selective pressures can produce similar adaptations (beneficial features).