- 3472 - ATOMIC CLOCKS - finding Dark matter? Atomic clocks work by tracking the energy levels of electrons. When an electron changes energy levels, it absorbs or emits light with a frequency that is identical for all atoms of a particular element. Optical atomic clocks keep time by using a laser that is tuned to precisely match this frequency.
------------- 3472 - ATOMIC CLOCKS - finding Dark matter?
- Atomic clocks are the most accurate instruments ever made. The inaccuracies are measured in seconds lost in billions of years. That seems impossible? How would we know?
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- These instruments can measure time so precisely that they will only lose one second every 300 billion years. This accuracy will allow scientists to make for more exact measurements of gravitational waves, dark matter and other physics phenomena.
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- Optical lattice clocks are already the best clocks in the world, and here we get this level of performance that no one has seen before. Generally speaking, atomic clocks are clocks that track the resonances of atom frequencies, usually the atoms of cesium or rubidium.
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- “Atomic clocks” work by tracking the energy levels of electrons. When an electron changes energy levels, it absorbs or emits light with a frequency that is identical for all atoms of a particular element.
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- “Optical atomic clocks” keep time by using a laser that is tuned to precisely match this frequency.
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- The new study created a multiplexed clock, which separated strontium atoms into a line in a single vacuum chamber. The laser on only a single clock, the laser excited electrons in the same number of atoms for only one-tenth of a second. But with two clocks at the same time, the atoms stayed excited for 26 seconds.
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- The group then attempted to measure differences between clocks precisely, because two groups of atoms in slightly different environments will "tick" at different rates due to changes in magnetic fields or gravity. The team ran the experiment over 1,000 times to measure the difference, finding more precision in that measurement over time.
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- Ultimately, the researchers detected a difference in the ticking rate between two atomic clocks "that would correspond to them disagreeing with each other by only one second every 300 billion years.
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- These researchers are putting a global network of the most precise timekeepers ever made to the task of hunting for dark matter, the invisible and largely intangible substance that researchers think makes up about five-sixths of all matter in the universe.
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- The existence of dark matter is suggested via its gravitational effects on the movements of stars and galaxies. However, it remains a mystery as to what it might be composed of, and projects ranging from the most powerful atom smasher ever built to vats of chilly liquid xenon have failed to find a trace of it so far.
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- Scientists have largely eliminated all known particles as possible explanations for dark matter. One remaining possibility is that dark matter is made of a new kind of particle; another is that dark matter is not made of particles at all, but rather a field that pervades space much like gravity does.
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- Previous research suggested that if dark matter is a field, structures could emerge within it, "topological defects" shaped like points, strings or sheets and potentially reaching at least the size of a planet. These structures might have formed during the chaos after the Big Bang, and essentially froze into stable forms when the early universe cooled down.
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- Now scientists are testing the existence of dark-matter fields by looking for disturbances in some of the most accurate scientific instruments ever constructed, atomic clocks.
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- These instruments keep time by monitoring the quivering of atoms, much as grandfather clocks rely on swinging pendulums. Nowadays, atomic clocks are so accurate that they would lose no more than 1 second every 15 billion years, longer than the 13.8-billion-year age of the universe.
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- Interacting with a topological defect could make an atomic clock's atoms temporarily shake faster or slower. By monitoring a network of synchronized atomic clocks that are spread far enough apart for a topological defect to have an effect on some clocks but not others, scientists could detect the existence of these ghostly structures and measure some of their properties, such as their size and speed.
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- The researchers employed optical atomic clocks, which use laser beams to measure the motions of atoms when they are slowed down by cooling them to temperatures near absolute zero.
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- They calculated that passing through a topological defect could increase or decrease the fine-structure constant, which describes the overall strength of the electromagnetic force. Such changes would alter how atoms respond to lasers and the rate at which those clocks ticked.
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- Another possible explanation for dark matter is that its effects are caused by fields that vary in strength over time, which in turn lead to regular fluctuations in the strength of the electromagnetic field. Atomic clocks could detect such "coherently oscillating classical scalar fields“.
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- By analyzing four atomic clocks on three continents, in Colorado, France, Poland and Japan, the researchers could look for subtle variations in the fine-structure constant with about 100 times greater sensitivity than previous experiments. However, they did not detect any signal consistent with dark matter.
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- One of the major problems of optical atomic clocks is that they can currently only operate continuously for about a day. One reason for this is that optical atomic clocks need to keep many lasers operating in sync in order to work, and over time at least one of these lasers fall out of sync. However, a key advantage of their network is that it does not require all its clocks to operate at the same time.
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February 20, 2022 ATOMIC CLOCKS - finding Dark matter? 3472
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