Science advances by a combination of normal science and discovery of anomalies. Many revolutions come from long periods of normal science reinforced by exceptional science. example: accelerating universe from supernova Ia measurements Discoveries often come from opening up new technological windows. example: LIGO detection of gravitational waves from colliding black holes Sometimes discoveries come as unexpected events using technology that has been present for some time example: discovery of quasars example: GRB 990123 prompt afterglow
Dark matter experiments If dark matter consists of WIMPs, dark matter particles will cause nuclei to recoil and emit a photon if the interaction is not too weak. The Liquid Underground Xenon experiment uses about 100 kg of liquid xenon in the Homesake Mine in South Dakota. The dark matter scattering events were distinguished from neutron scattering events by looking for single scattering as opposed to multiple scattering events. The most recent experiment ended in May 2016. no candidate dark matter particle has yet been detected.
Dark matter in accelerators Dark matter particles may be created in accelerators. These particles may have negligible interactions with normal baryonic matter. Their presence could be inferred from missing energy and momentum that are not detected from any other particles. If dark matter particles interact with quarks they might be created when two proton beams travelling in opposite directions collide at CERN in the LHC. If dark matter particles interact with leptons, they may be created in collisions in the Large Electron-Positron Collider at CERN.
James Webb Space Telescope JWST is a 6.5 m segmented mirror that will be launched in 2018 and will observe from the L2 point beyond the Moon. JWST is optimized to observe at mid-infrared wavelengths.
Cosmology with JWST JWST would detect galaxies at redshift z=20. Individual Population III stars are too faint to detect unless they are lensed or are bursting.
Extremely Large Telescopes If mirrors are segmented, arbitrarily large telescopes can be constructed with no optical distortion from bending of the mirror under stress. In the next decade, the European Extremely Large Telescope in Chile and the Thirty Meter Telescope on Mauna Kea in Hawaii will begin operations.
ELTs will be optimized to observe at optical wavelengths, which corresponds to restframe ultraviolet at high redshift. JWST will operate up to mid-infrared wavelengths and therefore look at higher redshifts than TMT/ELT TMT/ELT will make measurements over a wider area than JWST and therefore provide better statistics on cosmological parameters that are sensitive to variation of the galaxy population over time.
Large Synoptic Survey Telescope The LSST Survey Telescope is a wide-field 8.4 m telescope in El Penon, Chile that will image the entire available sky every week. The field of view has 3.5 diameter and the telescope uses a 3.2-gigapixel CCD camera. The telescope will generate 1.28 petabytes of data each year.
The cosmological parameters will be established to better than 1%, providing constraints on the nature of dark energy.
Square Kilometre Array The SKA is an array of radio telescopes under construction in South Africa and Australia with total collecting area one square kilometre. It will consist of several subarrays operating between 50 MHz and 1.4 GHz. The SKA will map 1 billion galaxies in the 21 cm line out to the edge of the observable Universe. This will provide a three-dimensional picture of all stages of galaxy formation, which is sensitive to the cosmological parameters and also to the manner in which gas accumulates in galaxies and turns into stars.
Atacama Large Millimetre Array ALMA is an array of sixty-six 12 m telescopes and seven smaller telescopes optimised to work at millimetre and submillimetre wavelengths. This site was selected for its altitude and dryness. ALMA can detect the first generation of massive galaxies, before they build up enough dust to be invisible at optical and near-infrared wavelengths. Galaxies between redshifts z = 10 and z = 5 are detectable because of their negative K correction
Future X-Ray astronomy The International X-Ray Observatory (merger of Constellation-X and ZEUS) was cancelled in 2012. The ESA Athena (Advanced Telescope for High-Energy Astronomy) satellite will be launched in 2028. it will be 100 times more sensitive than current x-ray telescopes like Chandra and XMM. A primary goal of Athena is to map the hot gas structure throughout the history of star formation and supermassive black hole formation. The feedback operates through momentum transfer by hot ionized gas that can be observed in x-rays. Feeding a black hole is through x-ray accretion discs.
Fermi Gamma-ray Space Telescope Fermi is a gamma-ray telescope launched in 2008 in a low Earth orbit. Its main instrument is Large Area Telescope (LAT) which will study active galactic nuclei and will look for dark matter candidates. In 2013 Fermi observed GRB 130427A, which had energy 94 GeV. It might be associated with a Type IC supernova at redshift z=0.3.
Laser Interferometer Space Antenna LISA is a proposed (launch 2030) mission designed to detect gravitational waves. The observatory consists of three spacecraft, arranged in an equilateral triangle with 2.5 million kilometre arms in a heliocentric orbit. The detection regime is intermediate between pulsar timing arrays which are sensitive to low frequency waves and LIGO, which is sensitive to high frequency waves. The intention is to watch the buildup of supermassive black holes. LIGO is only sensitive to lower mass inspirals like GW150914.
Cosmological simulations Cosmological simulations can measure the behaviour of a large number of particles within a fixed volume. Current simulations have more than 10 billion particles and have resolution elements as small as 100 pc. There are a range of techniques to investigate how the baryons interact with each other through hydrodynamics and gravity as they move between the volume elements. The simulations can be compared to observations on large and small scales both and low at high redshift. There are parameters in the models that are not constrained well by observations which have a strong effect on the model results, for example the Lyman alpha escape fraction from the highest redshift galaxies. Within the uncertainties, the Lambda CDM model from Planck is consistent with the simulations.
Quantum fluctuations during inflation In quantum physics, a vacuum fluctuation is the uncertainty in the energy at a point in free space due to Heisenberg's uncertainty principle. As the Universe inflated, these fluctuations would have grown and become fixed. These could eventually turn in to the fluctuations observed in the microwave background, and eventually into galaxies. A goal of inflation theory is to find a scalar field and potential which simultaneously inflates the Universe through 60 e-foldings and grows vacuum fluctuations into the microwave background anisotropies.
Philosophical considerations Anthropic principle Theories of Everything Experiment and mathematics Cosmological selection Frameworks
Anthropic principle Strong Anthropic Principle The Universe is compelled to have conscious and sapient life emerge and therefore we should expect fundamental constants to fall within the narrow range compatible with the development of life. Weak Anthropic Principle Fine tuning of model parameters is due to selection bias because of our location in cosmological time.
Theories of Everything Godel s Impossibility Theorem Any model which can be proved is necessarily incomplete.
Experiment and mathematics At higher energies physical theories rely progressively less on direct experimental verifications. At the very highest energies, we need to rely completely on mathematics. The transition from theories being purely mathematical as opposed to be verified by experiment is at the end of the GUT era at an energy of about 10^16 GeV.
Cosmological selection The weak anthropic principle applies to our ability to measure cosmological parameters in the same way that it applies to fundamental constants. The anthropic principle and Gödel s theorem do not distinguish between epoch and fundamental constants.
Frameworks Fundamental constants and cosmological parameters can be fine tuned to match observables. But the frameworks that define the constants and parameters also need to be selected and fine tuned. What selected quantum field theories and general relativity? Asking this question recursively leads to an interpretation of Gödel s theorem.