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... hysics beyond the Standard Model.</p>]]></content:encoded>
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<?xml version="1.0" encoding="UTF-8"?><rss version="2.0" xmlns:content="http://purl.org/rss/1.0/modules/content/" xmlns:dc="http://purl.org/dc/elements/1.1/" xmlns:sy="http://purl.org/rss/1.0/modules/syndication/" > <channel> <title>RSS Univers</title> <link>https://www.universator.com/</link> <description>Univers</description> <lastBuildDate>Sat, 24 May 2025 12:33:04 +0200</lastBuildDate> <language>en</language> <sy:updatePeriod>daily</sy:updatePeriod> <sy:updateFrequency>1</sy:updateFrequency> <item> <title>Higgs boson LHC</title> <description>Today during the 50th session of “Rencontres de Moriond” in La Thuile Italy, the ATLAS and CMS experiments presented for the first time a combination of their results on the mass of the Higgs boson. The combined mass of the ...</description> <content:encoded><![CDATA[<img src="/img/find_a_higgs_boson_in_lhc.jpg" alt="Find a Higgs boson in LHC" align="left" /><p>Today during the 50th session of “Rencontres de Moriond” in La Thuile Italy, the ATLAS and CMS experiments presented for the first time a combination of their results on the mass of the Higgs boson. The combined mass of the Higgs boson is mH = 125.09 ± 0.24 (0.21 stat. ± 0.11 syst.) GeV, which corresponds to a measurement precision of better than 0.2%. The Higgs boson is an essential ingredient of the Standard Model of particle physics, the theory that describes all known elementary particles and their interactions. The Brout-Englert-Higgs mechanism, through which the existence of the Higgs boson was predicted, is believed to give mass to all elementary particles. Today’s result is the most precise measurement of the Higgs boson mass yet and among the most precise measurements performed at the LHC to date. “Collaboration is really part of our organization’s DNA, ” says CERN Director General Rolf Heuer. “I’m delighted to see so many brilliant physicists from ATLAS and CMS joining forces for the very first time to obtain this important measurement at the LHC”. The Higgs boson decays into various different particles. For this measurement, results on the two decay channels that best reveal the mass of the Higgs boson have been combined. These two decay channels are: the Higgs boson decaying to two photons; and the Higgs boson decaying to four leptons – where the leptons are an electron or muon. Candidate Higgs boson event from collisions between protons in the ATLAS detector on the LHC. From the collision at the centre, the particle decays into four muons (red tracks)(Image:ATLAS/CERN) Each experiment has found a few hundred events in the Higgs to photons channel and a few tens of events in the Higgs to leptons channel. The analysis uses the data collected from about 4000 trillion proton-proton collisions at the Large Hadron Collider (LHC) in 2011 and 2012 at centre-of-mass energies of 7 and 8 TeV. “The Higgs Boson was discovered at the LHC in 2012 and the study of its properties has just begun. By sharing efforts between ATLAS and CMS, we are going to understand this fascinating particle in more detail and study its behaviour, ” says CMS spokesperson Tiziano Camporesi. The Standard Model does not predict the mass of the Higgs boson itself, so it must be measured experimentally. But once supplied with a Higgs mass, the Standard Model does make predictions for all the other properties of the Higgs boson, which can then be tested by the experiments. This mass combination is the first step towards a combination of other measurements of the Higgs boson’s properties, which will include its other decays. "While we are just getting ready to restart the LHC, it is admirable to notice the precision already achieved by the two experiments and the compatibility of their results, ” says CERN Director of Research Sergio Bertolucci. “This is very promising for LHC Run 2.” Up to now, increasingly precise measurements from the two experiments have established that all observed properties of the Higgs boson, including its spin, parity and interactions with other particles are consistent with the Standard Model Higgs boson. With the upcoming combination of other Run 1 Higgs results from the two experiments and with higher energy and more collisions to come during LHC Run 2, physicists expect to increase the precision of the Higgs boson mass even more and to explore in more detail the particle’s properties. During Run 2, they will be able to combine their results promptly and thus increase the LHC’s sensitivity to effects that could hint at new physics beyond the Standard Model.</p>]]></content:encoded> <category><![CDATA[Higgs Boson]]></category> <link>https://www.universator.com/HiggsBoson/higgs-boson-lhc</link> <guid isPermaLink="true">https://www.universator.com/HiggsBoson/higgs-boson-lhc</guid> <pubDate>Sat, 24 May 2025 08:33:00 +0000</pubDate> </item> <item> <title>Force of gravity Calculator</title> <description>If you fill in the height, you'll get the time and speed at the end of your fall. If you're kind enough to supply your mass, you'll also get the energy in joules (newton-meters) when you hit the deck. :-) See the to see how ...</description> <content:encoded><![CDATA[<img src="/img/physics_equations_formulas_calculator.jpg" alt="Physics Equations Formulas" align="left" /><p>If you fill in the height, you'll get the time and speed at the end of your fall. If you're kind enough to supply your mass, you'll also get the energy in joules (newton-meters) when you hit the deck. :-) See the to see how impact velocity varies with height. As is probably obvious, the higher you are, the harder you land. The relationship looks like this, in km/h: In other words, falling from 50m high is the equivalent of getting hit by a car going 112 km/h, or 70 miles per hour — what would happen if you ran out into a busy freeway. If that's not a decent argument against free soloing, I'm not sure what is. Free fall / falling speed equations The calculator uses the standard formula from Newtonian physics to figure out how long before the falling object goes splat: The force of gravity, = 9.8 m/s2 Gravity accelerates you at 9.8 meters per second per second . After one second, you're falling 9.8 m/s. After two seconds, you're falling 19.6 m/s, and so on. Time to splat: sqrt ( 2 * height / 9.8 ) It's the square root because you fall faster the longer you fall. The more interesting question is why it's times two: If you accelerate for 1 second, your average speed over that time is increased by only 9.8 / 2 m/s. Velocity at splat time: sqrt( 2 * g * height ) This is why falling from a higher height hurts more. Energy at splat time: 1/2 * mass * velocity2 = mass * g * height Ignoring air friction: Terminal velocity This calculator doesn't take into account air friction. But think about what happens if you stick your hand out of the window while driving down the freeway: The wind pushes pretty hard against you. That's air friction. The faster you're going, the harder it pushes back. In fact, it pushes back with the square of your speed, whereas the acceleration of gravity is constant. This means that at some point, the force of air against you equals the force of gravity, and you stop accelerating. That point is called terminal velocity (see this wikipedia article for more information). It depends a lot on your position — something shaped like a bullet will have a higher terminal velocity than something shaped like a flat pancake parallel to the earth, because the latter has more surface area exposed to air friction. The calculator doesn't take any of this into account. In practice, terminal velocity on earth will prevent you from going more than about 320 km/h, or about 200 miles per hour. If you're lying belly-to-the-earth, you'll only travel about 195 km/h (122 miles per hour). As you can see from the graph above, you'd have to fall from higher than 50 meters above the ground for this to really matter much, and at that point, you'd be in enough trouble to not care much. Skydivers, however, should go read the Wikipedia article. About the calculator This is a javascript-based calculator. For you history buffs, the first version used a 10-iteration implementation of Newton's method to compute the square root needed for some of the equations, because in the days of yore, many browsers didn't support sqrt natively. You can see the original code here: newton_sqrt.js - Square root using Newton's Method in Javascript.</p>]]></content:encoded> <category><![CDATA[Gravitational Force]]></category> <link>https://www.universator.com/GravitationalForce/force-of-gravity-calculator</link> <guid isPermaLink="true">https://www.universator.com/GravitationalForce/force-of-gravity-calculator</guid> <pubDate>Thu, 15 May 2025 08:29:00 +0000</pubDate> </item> <item> <title>Gravitational force Equations</title> <description>Near the surface of the Earth, use = 9.81 m/s2 (meters per second squared; which might be thought of as "meters per second, per second", or 32.2 ft/s2 as "feet per second per second") approximately. For other planets, multiply by ...</description> <content:encoded><![CDATA[<img src="/img/gravitational_forces_equation_images.jpg" alt="Gravitational Forces Equation" align="left" /><p>Near the surface of the Earth, use = 9.81 m/s2 (meters per second squared; which might be thought of as "meters per second, per second", or 32.2 ft/s2 as "feet per second per second") approximately. For other planets, multiply by the appropriate scaling factor. A coherent set of units for , , and is essential. Assuming SI units, is measured in meters per second squared, so must be measured in meters, in seconds and in meters per second. In all cases, the body is assumed to start from rest, and air resistance is neglected. Generally, in Earth's atmosphere, all results below will therefore be quite inaccurate after only 5 seconds of fall (at which time an object's velocity will be a little less than the vacuum value of 49 m/s (9.8 m/s2 × 5 s) due to air resistance). Air resistance induces a drag force on any body that falls through any atmosphere other than a perfect vacuum, and this drag force increases with velocity until it equals the gravitational force, leaving the object to fall at a constant terminal velocity. Atmospheric drag, the coefficient of drag for the object, the (instantaneous) velocity of the object, and the area presented to the airflow determine terminal velocity. Apart from the last formula, these formulas also assume that negligibly varies with height during the fall (that is, they assume constant acceleration). The last equation is more accurate where significant changes in fractional distance from the center of the planet during the fall cause significant changes in g. This equation occurs in many applications of basic physics. The equations [edit] Measured fall time of a small steel sphere falling from various heights. The data is in good agreement with the predicted fall time of , where h is the height and g is the acceleration of gravity. Examples [edit] The first equation shows that, after one second, an object will have fallen a distance of 1/2 × 9.8 × 12 = 4.9 meters. After two seconds it will have fallen 1/2 × 9.8 × 22 = 19.6 meters; and so on. The second to last equation becomes grossly inaccurate at great distances. If an object fell 10, 000 meters to Earth, then the results of both equations differ by only 0.08%; however, if it fell from geosynchronous orbit, which is 42, 164 km, then the difference changes to almost 64%. Based on wind resistance, for example, the terminal velocity of a skydiver in a belly-to-earth (i.e., face down) free-fall position is about 195 km/h (122 mph or 54 m/s). This velocity is the asymptotic limiting value of the acceleration process, because the effective forces on the body balance each other more and more closely as the terminal velocity is approached. In this example, a speed of 50% of terminal velocity is reached after only about 3 seconds, while it takes 8 seconds to reach 90%, 15 seconds to reach 99% and so on. Higher speeds can be attained if the skydiver pulls in his or her limbs (see also freeflying). In this case, the terminal velocity increases to about 320 km/h (200 mph or 90 m/s), which is almost the terminal velocity of the peregrine falcon diving down on its prey. The same terminal velocity is reached for a typical .30-06 bullet dropping downwards—when it is returning to earth having been fired upwards, or dropped from a tower—according to a 1920 U.S. Army Ordnance study. Competition speed skydivers fly in the head down position and reach even higher speeds. The current world record is 1, 357.6 km/h (843.6 mph/Mach 1.25) by Felix Baumgartner who skydived from 38, 969.4 m (127, 852.4 ft) above earth on 14 October 2012. The record was set due to the high altitude where the lesser density of the atmosphere decreased drag. For astronomical bodies other than Earth, and for short distances of fall at other than "ground" level, in the above equations may be replaced by G(M+m)/r2 where is the gravitational constant, M is the mass of the astronomical body, m is the mass of the falling body, and r is the radius from the falling object to the center of the body. The time taken for an object to fall from a height to a height , measured from the centers of the two bodies, is given by: where is the sum of the standard gravitational parameters of the two bodies. This equation should be used whenever there is a significant difference in the gravitational acceleration during the fall. Acceleration relative to the rotating Earth [edit] Centripetal force causes the acceleration measured on the rotating surface of the Earth to differ from the acceleration that is measured for a free-falling body: the apparent acceleration in the rotating frame of reference is the total gravity vector minus a small vector toward the north-south axis of the Earth, corresponding to staying stationary in that frame of reference.</p>]]></content:encoded> <category><![CDATA[Gravitational Force]]></category> <link>https://www.universator.com/GravitationalForce/gravitational-force-equations</link> <guid isPermaLink="true">https://www.universator.com/GravitationalForce/gravitational-force-equations</guid> <pubDate>Tue, 06 May 2025 08:27:00 +0000</pubDate> </item> <item> <title>Equation for universal Gravitation</title> <description>Figure 1: Portrait of Isaac Newton (by courtesy of SEDS). Newton's Laws of Motion Law of Inertia: A body continues in its state of constant velocity (which may be zero) unless it is acted upon by an external force. Fundamental ...</description> <content:encoded><![CDATA[<img src="/img/presentation_chapters_13_16_13_universal.jpg" alt="G, in the equation for" align="left" /><p>Figure 1: Portrait of Isaac Newton (by courtesy of SEDS). Newton's Laws of Motion Law of Inertia: A body continues in its state of constant velocity (which may be zero) unless it is acted upon by an external force. Fundamental Law of Dynamics: For an unbalanced force acting on a body, the acceleration a produced is proportional to the force impressed; the constant of proportionality is the inertial mass m of the body. F = m . a Law of Action and Reaction: In a system where no external forces are present, every action force is always opposed by an equal and opposite reaction force. Newton's Law of Universal Gravitation Two bodies attract each other with equal and opposite forces; the magnitude of this force is proportional to the product of the two masses and is also proportional to the inverse square of the distance between the centers of mass of the two bodies. F = G . M . m / r2 where m and m are the masses of the two bodies, r is the distance between the two, and G is the gravitational constant, whose value is : G = 6.67 . 10-11 Newton.metre2/kg2 The force with which the Earth attracts bodies situated near to its surface is called body's weight. The weight of a mass m, located on the Earth's surface is : P = m . g This expression is an immediate consequence of the Universal Gravitation Law and of . Under normal conditions, the value of g is approximately equal to 9.8 metres/second 2. Gravitational Acceleration According to, if a body acts on another with a certain force, the latter one acts on the former with an equivalent force in opposite direction. This happens with the Universal Gravitation Law, where the force that a body with mass m exerts on another body of mass m is the same as that exerted by the body of mass m on the body of mass m (although in opposite direction). However, although these forces are equal, the accelerations are not. By applying we will have: The acceleration value of the body with mass m is: am = F / m = G . M / r2 which does not depend on m, but on m. The acceleration value of the body with mass m is: aM = F / M = G . m / r2 That is: The acceleration of a body subject to the action of gravity does not depend on its own mass, but on that of the body acting on it. The Two-body Problem: Differential Equations of Universal Gravitation Considering that acceleration is the second derivative with respect to time, we have that the acceleration of a body subject to the gravitational action of another body of mass m is: d2r/dt2 = G . M / r2 We use a cartesian co-ordinates permanently situated in the center of the body with mass m. For this reason, the position of the body of mass m coincides with its distance r to the origin of co-ordinates (its radius vector). Changing the previous equation to cartesian co-ordinates (x, y) we obtain: d2x/dt2 = G . M . x / r3 d2y/dt2 = G . M . y / r3 where r = square root (x2 + y2) Depending on the masses of the two bodies, and the initial conditions (the initial positions and velocities) the trajectory of the moving body may be: A free fall in a straight line. A circle (an ellipse with no eccentricity). An ellipse with a low eccentricity. An ellipse with a high eccentricity (a very elongated ellipse). A parabole (the limiting case). You can push one of the following six buttons to see a simulation of these cases. Two additional buttons allow you to stop the simulation and to continue it.</p>]]></content:encoded> <category><![CDATA[Universal Gravitation Constant]]></category> <link>https://www.universator.com/UniversalGravitationConstant/equation-for-universal-gravitation</link> <guid isPermaLink="true">https://www.universator.com/UniversalGravitationConstant/equation-for-universal-gravitation</guid> <pubDate>Sun, 27 Apr 2025 08:24:00 +0000</pubDate> </item> <item> <title>Gravitational field Physics</title> <description>Variation of g with distance from the centre of a uniform spherical mass of radius, R Variation of g on a line joining the centres of two point masses If m1 &gt; m2 then The potential at a point in a gravitational field is equal ...</description> <content:encoded><![CDATA[<img src="/img/physics_focus_first_direct_measurement.jpg" alt="Figure caption expand figure" align="left" /><p>Variation of g with distance from the centre of a uniform spherical mass of radius, R Variation of g on a line joining the centres of two point masses If m1 > m2 then The potential at a point in a gravitational field is equal to the work done bringing a 1kg mass from infinity to that point. The units are Jkg-1. To calculate work done by a force we use the equation w = F.s but in this situation it is a little more complicated because the force is not of constant magnitude. However, we do know how the force varies with distance from the body (Newton’s law of universal gravitation) and it can be shown* that the work done, w, bringing a mass, m, from infinity to point p is given by: where, M is the mass of the body (the earth, in this case). *a very useful phrase if you a) don't know how to do something or b) can't be bothered to do it ! A body at infinity, has zero gravitational potential. A body normally falls to its lowest state of potential (energy) so we must arrange that the equation for potential is such that, as r decreases, the potential decreases. We can do this by including a negative sign in the above equation. Then, as r decreases, V decreases (becomes a greater negative quantity). Therefore, to calculate the potential at a point in the gravitational field of a point mass or a uniformly distributed spherical mass: If a body is thrown upwards fast enough, it never comes back down: it has escaped from the planet. The velocity needed to do this is called the escape velocity of the planet. As the body is moving away from the planet, it is losing kinetic energy and gaining potential energy. To completely escape from the gravitational attraction of the planet, the body must be given enough kinetic energy to take it to a position where its potential energy is zero. The potential energy possessed by a body of mass m, in a gravitational field is given by:</p>]]></content:encoded> <category><![CDATA[Gravitational Field]]></category> <link>https://www.universator.com/GravitationalField/gravitational-field-physics</link> <guid isPermaLink="true">https://www.universator.com/GravitationalField/gravitational-field-physics</guid> <pubDate>Fri, 18 Apr 2025 08:22:00 +0000</pubDate> </item> <item> <title>Space time distortion</title> <description>We are used to thinking of time as absolute and universal, so it is disturbing to find that it can flow at a different rate for observers in different frames of reference. But consider the behavior of the γ factor shown in ...</description> <content:encoded><![CDATA[<img src="/img/space_time_distortion_1_by_13tangerines.jpg" alt="Space-time distortion 1 by" align="left" /><p>We are used to thinking of time as absolute and universal, so it is disturbing to find that it can flow at a different rate for observers in different frames of reference. But consider the behavior of the γ factor shown in figure h. The graph is extremely flat at low speeds, and even at 20% of the speed of light, it is difficult to see anything happening to γ. In everyday life, we never experience speeds that are more than a tiny fraction of the speed of light, so this strange strange relativistic effect involving time is extremely small. This makes sense: Newton's laws have already been thoroughly tested by experiments at such speeds, so a new theory like relativity must agree with the old one in their realm of common applicability. This requirement of backwards-compatibility is known as the correspondence principle. h / The behavior of the γ factor. Space The speed of light is supposed to be the same in all frames of reference, and a speed is a distance divided by a time. We can't change time without changing distance, since then the speed couldn't come out the same. If time is distorted by a factor of γ, then lengths must also be distorted according to the same ratio. An object in motion appears longest to someone who is at rest with respect to it, and is shortened along the direction of motion as seen by other observers. No simultaneity Part of the concept of absolute time was the assumption that it was valid to say things like, “I wonder what my uncle in Beijing is doing right now.” In the nonrelativistic world-view, clocks in Los Angeles and Beijing could be synchronized and stay synchronized, so we could unambiguously define the concept of things happening simultaneously in different places. It is easy to find examples, however, where events that seem to be simultaneous in one frame of reference are not simultaneous in another frame. In figure i, a flash of light is set off in the center of the rocket's cargo hold. According to a passenger on the rocket, the parts of the light traveling forward and backward have equal distances to travel to reach the front and back walls, so they get there simultaneously. But an outside observer who sees the rocket cruising by at high speed will see the flash hit the back wall first, because the wall is rushing up to meet it, and the forward-going part of the flash hit the front wall later, because the wall was running away from it. i / Different observers don't agree that the flashes of light hit the front and back of the ship simultaneously. We conclude that simultaneity is not a well-defined concept. This idea may be easier to accept if we compare time with space. Even in plain old Galilean relativity, points in space have no identity of their own: you may think that two events happened at the same point in space, but anyone else in a differently moving frame of reference says they happened at different points in space. For instance, suppose you tap your knuckles on your desk right now, count to five, and then do it again. In your frame of reference, the taps happened at the same location in space, but according to an observer on Mars, your desk was on the surface of a planet hurtling through space at high speed, and the second tap was hundreds of kilometers away from the first. Relativity says that time is the same way - both simultaneity and “simulplaceity” are meaningless concepts. Only when the relative velocity of two frames is small compared to the speed of light will observers in those frames agree on the simultaneity of events. j / In the garage's frame of reference, 1, the bus is moving, and can fit in the garage. In the bus's frame of reference, the garage is moving, and can't hold the bus. The garage paradox One of the most famous of all the so-called relativity paradoxes has to do with our incorrect feeling that simultaneity is well defined. The idea is that one could take a schoolbus and drive it at relativistic speeds into a garage of ordinary size, in which it normally would not fit. Because of the length contraction, the bus would supposedly fit in the garage. The paradox arises when we shut the door and then quickly slam on the brakes of the bus. An observer in the garage's frame of reference will claim that the bus fit in the garage because of its contracted length. The driver, however, will perceive the garage as being contracted and thus even less able to contain the bus. The paradox is resolved when we recognize that the concept of fitting the bus in the garage “all at once” contains a hidden assumption, the assumption that it makes sense to ask whether the front and back of the bus can simultaneously be in the garage. Observers in different frames of reference moving at high relative speeds do not necessarily agree on whether things happen simultaneously. The person in the garage's frame can shut the door at an instant he perceives to be simultaneous with the front bumper's arrival at the back wall of the garage, but the driver would not agree about the simultaneity of these two events, and would perceive the door as having shut long after she plowed through the back wall.</p>]]></content:encoded> <category><![CDATA[Newton Universal Law]]></category> <link>https://www.universator.com/NewtonUniversalLaw/space-time-distortion</link> <guid isPermaLink="true">https://www.universator.com/NewtonUniversalLaw/space-time-distortion</guid> <pubDate>Wed, 09 Apr 2025 08:22:00 +0000</pubDate> </item> <item> <title>Gravitational force equation Calculator</title> <description>Newton's Law of Gravity states that 'Every particle attracts every other particle with a force that is proportional to the product of their masses and inversely proportional to the distance between them. where, G = Universal ...</description> <content:encoded><![CDATA[<img src="/img/gravity_calculation_of_a_normal.jpg" alt="Enter image description here" align="left" /><p>Newton's Law of Gravity states that 'Every particle attracts every other particle with a force that is proportional to the product of their masses and inversely proportional to the distance between them. where, G = Universal Gravitational Constant = 6.6726 x 10-11N-m2/kg2 m1 = Mass of Object 1 m2 = Mass of Object 2 r = Distance Between the Objects. Case 1: Determine the force of gravitational attraction between the earth 5.98 x 1024 kg and a 70 kg boy who is standing at sea level, a distance of 6.38 x 106 m from earth's center. m1 = 5.98 x 1024 kg, m1 = 70 kg, r = 6.38 x 106 m, G = 6.6726 x 10-11N-m2/kg2 Substitute the values in the below Gravitational Force formula: This example will guide you to calculate the Gravitational Force manually. Case 2: Find the mass of one object if the magnitude of the gravitational force acting on each particle is 2 x 10-8, the one mass is 25 kg and the objects are 1.2 meters apart F = 2 x 10-8, m2 = 25 kg, r = 1.2 m, G = 6.6726 x 10-11N-m2/kg2.</p>]]></content:encoded> <category><![CDATA[Gravitational Force]]></category> <link>https://www.universator.com/GravitationalForce/gravitational-force-equation-calculator</link> <guid isPermaLink="true">https://www.universator.com/GravitationalForce/gravitational-force-equation-calculator</guid> <pubDate>Mon, 31 Mar 2025 08:18:00 +0000</pubDate> </item> <item> <title>What is dark matter?</title> <description>Years ago I read an article by Martin Rees, in which he surveyed the options for what the dark matter of the universe might be. I forget the exact wording, but near the end he said something like “There are so many candidates ...</description> <content:encoded><![CDATA[<img src="/img/dark_matter_map_milky_way.jpg" alt="Click for view big size" align="left" /><p>Years ago I read an article by Martin Rees, in which he surveyed the options for what the dark matter of the universe might be. I forget the exact wording, but near the end he said something like “There are so many candidates, it would be quite surprising to find ourselves living in a universe without dark matter.” I was reminded of this when I saw a Quantum Diaries post by Alex Millar, entitled “Why Dark Matter Exists.” Why do we live in a universe with five times as much dark matter as ordinary matter, anyway? As it turns out, the post was more about explaining all of the wonderful evidence we have that there is so much dark matter. That’s a very respectable question, one that I’ve covered again. The less-respectable (but still interesting to me) question is, Why is the universe like that? Is the existence of dark matter indeed unsurprising, or is it an unusual feature that we should take as an important clue as to the nature of our world? Generally, physicists love asking these kinds of questions (“why does the universe look this way, rather than that way?”), and yet are terribly sloppy at answering them. Questions about surprise and probability require a measure: a way of assigning, to each set of possibilities, some kind of probability number. Your answer wholly depends on how you assign that measure. If you have a coin, and your probability measure is “it will be heads half the time and tails half the time, ” then getting twenty heads in a row is very surprising. If you have reason to think the coin is loaded, and your measure is “it comes up heads almost every time, ” then twenty heads in a row isn’t surprising at all. Yet physicists love to bat around these questions in reference to the universe itself, without really bothering to justify one measure rather than another. With respect to dark matter, we’re contemplating a measure over all the various ways the universe could be, including both the laws of physics (which tell us what particles there can be) and the initial conditions (which set the stage for the later evolution). Clearly finding the “right” such measure is pretty much hopeless! But we can try to set up some reasonable considerations, and see where that leads us. Here are the important facts we know about dark matter: It’s dark. Doesn’t interact with electromagnetism, at least not with anywhere near the strength that ordinary charged particles do. It’s cold. Individual dark matter particles are moving slowly and have been for a while, otherwise they would have damped perturbations in the early universe. There’s a goodly amount of it. About 25% of the energy density of the current universe, compared to only about 5% in the form of ordinary matter. It’s stable, or nearly so. The dark matter particle has to be long-lived, or it would have decayed away a long time ago. It’s dissipationless, or nearly so. Ordinary matter settles down to make galaxies because it can lose energy through collisions and radiation; dark matter doesn’t seem to do that, giving rise to puffy halos rather than thin galactic disks. None of these properties is, by itself, very hard to satisfy if we’re just inventing new particles. But if we try to be honest — asking “What would expect to see, if we didn’t know what things actually looked like?” — there is a certain amount of tension involved in satisfying them all at once. Let’s take them in turn. Having a particle be dark isn’t hard at all. All electrically-neutral particles are dark in this sense. Photons, gravitons, neutrinos, neutrons, what have you.</p>]]></content:encoded> <category><![CDATA[Dark Matter]]></category> <link>https://www.universator.com/DarkMatter/what-is-dark-matter</link> <guid isPermaLink="true">https://www.universator.com/DarkMatter/what-is-dark-matter</guid> <pubDate>Sat, 22 Mar 2025 09:05:00 +0000</pubDate> </item> <item> <title>Quantum Physics, Theories</title> <description>Quantum theory is the theoretical basis of modern physics that explains the nature and behavior of matter and energy on the atomic and subatomic level. The nature and behavior of matter and energy at that level is sometimes ...</description> <content:encoded><![CDATA[<img src="/img/quantum_physics_theories_quantum_physics_theories.jpg" alt="The Main reason why You should" align="left" /><p>Quantum theory is the theoretical basis of modern physics that explains the nature and behavior of matter and energy on the atomic and subatomic level. The nature and behavior of matter and energy at that level is sometimes referred to as quantum physics and quantum mechanics. In 1900, physicist Max Planck presented his quantum theory to the German Physical Society. Planck had sought to discover the reason that radiation from a glowing body changes in color from red, to orange, and, finally, to blue as its temperature rises. He found that by making the assumption that energy existed in individual units in the same way that matter does, rather than just as a constant electromagnetic wave - as had been formerly assumed - and was therefore quantifiable , he could find the answer to his question. The existence of these units became the first assumption of quantum theory. Planck wrote a mathematical equation involving a figure to represent these individual units of energy, which he called . The equation explained the phenomenon very well; Planck found that at certain discrete temperature levels (exact multiples of a basic minimum value), energy from a glowing body will occupy different areas of the color spectrum. Planck assumed there was a theory yet to emerge from the discovery of quanta, but, in fact, their very existence implied a completely new and fundamental understanding of the laws of nature. Planck won the Nobel Prize in Physics for his theory in 1918, but developments by various scientists over a thirty-year period all contributed to the modern understanding of quantum theory. The Development of Quantum Theory In 1900, Planck made the assumption that energy was made of individual units, or quanta. In 1905, Albert Einstein theorized that not just the energy, but the radiation itself was quantized in the same manner. In 1924, Louis de Broglie proposed that there is no fundamental difference in the makeup and behavior of energy and matter; on the atomic and subatomic level either may behave as if made of either particles or waves. This theory became known as the principle of wave-particle duality : elementary particles of both energy and matter behave, depending on the conditions, like either particles or waves. In 1927, Werner Heisenberg proposed that precise, simultaneous measurement of two complementary values - such as the position and momentum of a subatomic particle - is impossible. Contrary to the principles of classical physics, their simultaneous measurement is inescapably flawed; the more precisely one value is measured, the more flawed will be the measurement of the other value. This theory became known as the uncertainty principle, which prompted Albert Einstein's famous comment, "God does not play dice." The Copenhagen Interpretation and the Many-Worlds Theory The two major interpretations of quantum theory's implications for the nature of reality are the Copenhagen interpretation and the many-worlds theory. Niels Bohr proposed the Copenhagen interpretation of quantum theory, which asserts that a particle is whatever it is measured to be (for example, a wave or a particle), but that it cannot be assumed to have specific properties, or even to exist, until it is measured. In short, Bohr was saying that objective reality does not exist. This translates to a principle called superposition that claims that while we do not know what the state of any object is, it is actually in all possible states simultaneously, as long as we don't look to check. To illustrate this theory, we can use the famous and somewhat cruel analogy of Schrodinger's Cat. First, we have a living cat and place it in a thick lead box. At this stage, there is no question that the cat is alive. We then throw in a vial of cyanide and seal the box. We do not know if the cat is alive or if the cyanide capsule has broken and the cat has died. Since we do not know, the cat is both dead and alive, according to quantum law - in a superposition of states. It is only when we break open the box and see what condition the cat is that the superposition is lost, and the cat must be either alive or dead.</p>]]></content:encoded> <category><![CDATA[Gravitational Field]]></category> <link>https://www.universator.com/GravitationalField/quantum-physics-theories</link> <guid isPermaLink="true">https://www.universator.com/GravitationalField/quantum-physics-theories</guid> <pubDate>Thu, 13 Mar 2025 09:04:00 +0000</pubDate> </item> <item> <title>Gravitational pull on an object</title> <description>The framework the Universe is built from (space-time) is 'flexible' and is affected (to a degree) by the *contents* of the Universe. Particles with mass *deform* spacetime. The effect is very, very weak - but it's there, and it's ...</description> <content:encoded><![CDATA[<img src="/img/presentation_everything_in_the_world_is.jpg" alt="Of gravitational pull on" align="left" /><p>The framework the Universe is built from (space-time) is 'flexible' and is affected (to a degree) by the *contents* of the Universe. Particles with mass *deform* spacetime. The effect is very, very weak - but it's there, and it's cumulative. You and I have hardly any effect, but a big ball of stuff like the earth deforms space-time quite a lot. It results in 'curvature' of space-time. This is the reason why when you throw a ball across the park, it moves in an arc. The ball actually moves in a straight line, but the universe (space-time) is curved towards the mass of the earth, and the ball's path traces a curve. If you find this hard to believe: Think about the path the ball would follow if you threw it in outer space, where local space-time isn't dominated by a powerful gravitational field like the one the earth creates. The ball would move in a straight line! Did you throw it differently? Or is the curvature of spacetime different? Further proof: If you fired yourself from a cannon at the same speed and direction as the ball, if you look at the ball while you both fly through the air, *the ball appears to move in a straight line*. From your perspective, space-time 'curves' less when you move in concert with the ball, compared to if you were stationary (relative to the ball).</p>]]></content:encoded> <category><![CDATA[Gravitational Pull]]></category> <link>https://www.universator.com/GravitationalPull/gravitational-pull-on-an-object</link> <guid isPermaLink="true">https://www.universator.com/GravitationalPull/gravitational-pull-on-an-object</guid> <pubDate>Tue, 04 Mar 2025 08:37:00 +0000</pubDate> </item> </channel></rss>If you would like to create a banner that links to this page (i.e. this validation result), do the following:
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