Sphere Detector Unit

Can you help with a problem of waves traveling in space?

TV programs are broadcast at a frequency of about 100MHz with about 100kW of total power in 24 frames per second, which emanates roughly uniformly into about a sphere in angle. Assume that interstellar space transmits these broadcasts without attenuation. Compute the number of photons per unit time per unit area reaching a receiver on a possible planet in the nearest star system, Proxima Centauri, about 4 light‐years away (a light‐year is the distance light travels in a
year). No matter how smart they are, aliens would require at least a photon per frame to interpret our signals. If aliens aimed a receiver or detector directly at earth, how big (in diameter) would it have to be to receive a photon per frame? If we ever develop practical interstellar space travel, could we show our faces in the more fashionable neighborhoods of the galaxy?

I can't find a formula for the dispersion of waves in space...
Any help would be great

Always looking for the right formula, and then you can just plug in the numbers and the answer falls out the bottom--just like a vending machine. Well, if you have been assigned such a problem, you should have had enough physics to realize the physics is UNDERSTANDING the universe. It is not finding the right formula in your text book.

You have 100kW of rf power. That get spread over a sphere. The farther away you are from the broadcast antenna, the larger the radius and the bigger the sphere. Since it is always 100 kW spread over the sphere, the bigger the sphere the smaller the w/m^2 . Now, imagine a sphere with a radius of 4 light years. How many w/m^2 do you find on such a sphere if 100 kW are coming from the antenna?

How many Watts to you need to have one photon in 1/24 s? You will have to find the energy of a photon and calculate the area.

You do not need any formula for the dispersion of waves in space.

Sphere $12.49 Sphere

Smoke Detector $200 The remote Smoke Detector can be placed up to 2000 feet away from the tattletale unit depending on structures and objects in-between the smoke detector and the tattletale. It uses photoelectric technology to detect smoke (not heat) and it continually monitors its own sensitivity and operational status. The tattletale does not need to be armed to send a smoke alarm. The two 3V lithium betteries that are included will typically last for about 1 year. *Requires TattleTale Base unit or starter kit below *See PDF for system overview

Spherical Harmonics and Approximations on the Unit Sphere (Paperback) $109.82 These notes provide an introduction to the theory of spherical harmonics in an arbitrary dimension as well asan overview of classical and recent results on some aspects of the approximation of functions by spherical polynomials and numerical integration over the unit sphere. The notes are intended for graduate students in the mathematical sciences and researchers who are interested in solving problems involving partial differential and integral equations on the unit sphere, especially on the unit sphere in three-dimensional Euclidean space. Some related work for approximation on the unit disk in the plane is also briefly discussed, with results being generalizable to the unit ball in more dimensions.

Ewalds Sphere $58.94 The Ewald sphere is a geometric construct used in electron, neutron, and Xray crystallography which neatly demonstrates the relationship between: the wavelength of the incident and diffracted xray beams, the diffraction angle for a given reflection, the reciprocal lattice of the crystal. It was conceived by Paul Peter Ewald, a German physicist and crystallographer. Ewald himself spoke of the sphere of reflection. Ewalds sphere can be used to find the maximum resolution available for a given xray wavelength and the unit cell dimensions. It is often simplified to the twodimensional Ewalds circle model or may be referred to as the Ewald sphere. Author: Miller, Frederic P./ Vandome, Agnes F./ McBrewster, John Binding Type: Paperback Number of Pages: 72 Publication Date: 2010/07/26 Language: English Dimensions: 5.98 x 9.01 x 0.17 inches

Wireless Motion Detector Sensor $55 Install additional Mace® Motion Detector security sensors near the doors and windows of your home for added home protection. This motion detector sensor has a range up to 8 yards and a detection angle of 110 degrees. When the sensor is triggered it outputs a wireless RF signal to the main control unit.

Vibrating Pocket Transmitter Detector $118.3 Our Vibrating Pocket Detector gently vibrates to alert the user of the presence of hidden transmitters. This device can be used as a sweep unit or body worn counter surveillance device. Includes Leather carry case Size 4 1/2″ x 2 3/8″ x 1 1/8″

XRSR7 12-Band Radar/Laser Detector $279 Cobra's XRSR7 12-Band Radar/Laser Detector features S-XRS maximum performance technology, easy-to-Install, discreet, main radar/laser detector unit, POP mode radar gun detection, ku band detection, and more!

Discovery 3300 Metal Detector $239 Packed with features for technical searches yet simple enough to enjoy if it's your first time out, the Discovery 3300 metal detector is great for both beginners and pros. Custom programming with both automatic and ground-balance let the coil find exactly what you're after as efficiently as possible. Lightweight at 2.4 pounds, the unit is well constructed and features a waterproof coil for optimal corrosion resistance. Great for searching in even the most mineralized soil conditions, the detector has no complex adjustments or settings to worry about for easy location of coins, rings, gold and relics at the park, beach, and campground or in the back yard.

Lone Star Metal Detector $159 Most children, at one point or another, embark on a treasure hunt. They dig in the sand at the beach, or in the flower boxes at home, hoping to find a pirate's booty, an Egyptian King's tomb, or a lost toy. As children grow, the meaning of treasure evolves from mythical wooden chests stuffed with gold into more commonplace articles, but the hunt maintains that sense of adventure. For those who covet treasures of the metal variety, Bounty Hunter offers their Lone Star metal detector. Those individuals who prize Mother Earth also benefit from the detector, redirecting littered cans to the recycling bin. The detector scans using a waterproof 8-inch coil on an ergonomic S-rod. Moving the coil levelly over the ground or water, the unit detects small items up to 8 inches below and larger items up to 3 feet under. Three different operation modes further assist the bounty hunter. For indiscriminate prospecting, press the "all metal" button on the detector's touch pad, while selecting "auto notch" eliminates most pull-tabs and trash items from detection. The "discriminate notch" method eradicates iron and trash and allows the user to manually adjust the DISC/NOTCH knob to rule out other metals. The detector deciphers a target's metal composition both visually on the LCD screen, and audibly with a tone through the built-in speakers. A low tone indicates nails, bottle caps, gold or nickel while a medium tone suggests pull-tabs, zinc, and post-1982 pennies. High tones denote copper, silver, brass, and pre-1982 pennies. A headphone jack is installed. Headphones must be purchased separately, as must the two 9-volt alkaline batteries that power the detector. This item is covered under a five-year warranty. The USA-made detector measures 28.7 by 10.5 by 6.7 inches upon shipping and weighs 4.6 pounds.

2.4GHZ Carbon Monoxide Detector $450 Completely Wireless Home Carbon Monoxide Detector Camera Makes Surveillance Easy Unit available in Wireless Color or Wireless B/W. Select the right unit to suit your needs from the drop down menu located at the top right side of this page. This is a non-functioning Home Carbon Monoxide Detector Camera. This Home Carbon Monoxide Detector Camera is ideal because it plugs right in to a wall socket and can utilize many locations. It can even be plugged into an outlet close to the floor and still view the entire room. This item cannot be used to detect carbon monoxide.It's completely wireless and captures great quality black and white video. Includes: Wireless cameras include FREE 2.4 GHz receiver All necessary power supplies and battery packs are included. Black and white cameras feature .003 Lux which allows best possible images in almost complete darkness. Camera requires some ambient light (night light, television)

MB-1-R Gasoline Fume Detector $193.94 MB-1-R Gasoline Fume Detector MB-1-R Gasoline Fume DetectorSingle channel gasoline fume detector, with the same features as the M-1-R:High-tech stylingCompact sizeCircuitry TestAlarm horn mute functionsStandard two-inch display unit with gasoline sensor and twenty feet of plug-together lead.The MB-1-R adds a 10 amp relay to automatically start the bilge blower fan should gasoline fumes be detected. Installation requires only the addition of two wire leads from the control to the blower switch. To test, simply touch the test pad on the control: the red alert lamp will glow, the alarm horn will sound and the blower motor will start.The system works with power requirements of up to ten amps at 12 VDC.In addition to gas fumes, the MB-1-R can also detect high concentrations of battery hydrogen or engine exhaustIndicator lamp automatically increases in brightness during daylight and softens at night

Cobra XRS-9965 Radar Detector $160.99 1.90" Height x 3.10" Width x 5.20" Depth 6.50 oz The XRS 9965 provides total protection and peace of mind with Super-Xtreme Range Superheterodyne Technology, detecting all 15 radar/laser bands with its super-fast lock-on detection circuitry. The unit provides extra detection range and the best possible advance warning to even the fastest of POP mode radar guns. Other features include Cobra exclusive Touchscreen, full-color ExtremeBright DataGrafix Display, an 8-point electronic compass, Voice Alert, car battery voltage display/low car battery warning and much more. Touch Screen ExtremeBright DataGrafix Display Cobra Cobra Electronics Corporation K-band Ka Band Ka Superwide Laser Radar Detector Spectre Alert VG-2 Alert X-band XRS-9965 XRS-9965 Radar/Laser Detector www.cobra.com

Zircon Zircon Water Detector 64003 $9.26 Water detector Unit can be placed anywhere the potential for flooding or leaking exists: Under sink, near water heater, in basement, etc Loud alarm (95 dB) sounds with direct water contact Floats and signals for up to 72 hours Fully automatic operation - no wiring required Low battery indicator for optimum safety and performance Works on a 9V battery (not included) Brand #: Zircon 64003 UPC: 042186850086 Keywords: detector water alarm flood leaks

Cobra XRS-9550G Radar Detector $145.99 1 Year Limited 1.30" Height x 2.80" Width x 4.40" Depth 360° 5.30 oz Voice alert Pop detection IntelliMute Pro Safety Alert System (SAS) Stores up to 1,000 user alert locations Xtreme Range Superheterodyne technology DigiView Data Display The XRS 9550G provides total protection and peace of mind with the Xtreme Range Superheterodyne technology, detecting all 14 radar/laser bands with reliable and proven performance. The unit provides extra detection range and the best possible advance warning to even the fastest of POP mode radar guns. It comes with a GPS Locator and Lifetime Subscription to AURA Database to alert you to verified Speed and Red Light Camera locations, dangerous intersections, and reported Speed Trap locations. Other features include Cobra exclusive GPS 8-point compass, Voice Alert, text display, and more. City Cobra Cobra Electronics Corporation Highway K-band Ka Band Ku Band Laser Radar Detector Spectre Alert VG-2 Alert X-band XRS-9550G XRS-9550G Radar/Laser Detector www.cobra.com

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Galaxy Quest (Deleted Scenes)

Black Holes – Do They Exist?

Black holes are postulated to be one of the most destructive forces known in the universe, with nothing being able to escape from its gaping maw, not even light. Even, supposedly, all known laws of physics fall apart inside the depths of the black hole. So how does the universe allow these objects to exist? Or rather do they exist or are they just a product of humanity’s misunderstanding?

Fundamentally black holes are a product of gravity, the weakest of the four known forces in the universe. It was with Isaac Newton in which the first seeds of knowledge concerning black holes began to grow. With his laws of universal gravitation, Newton proposed that this gravitational force acts on everything, even light. As Novikov (1990) says “It is with the understanding of the fact that light is also subject to gravitational force that the early history of black holes began”.

The first tentative step into theorising the existence of black holes was taken by the British natural philosopher John Michell in 1783. In his explanation to show what very compact stars should look like, Michell tried to combine Newton’s law of gravitation with the corpuscular description of light. Michell came up with the notion of ‘escape velocity’, which explains the velocity with which a particle needs to escape a body’s gravity. Anything under the escape velocity will, by the force of gravity, be pulled back down. Developing this idea further Michell came up with the theory of a critical circumference, for which the speed of the light is its escape velocity for this body’s mass. Any thing under this critical circumference then light would even be pulled back down by gravity’s overwhelming force. Michell speculated that there was a number of stars in the universe, which were under the critical circumference, these he called dark stars. These ‘dark stars’ were the eighteenth century version of black holes. Laplace thirteen years later also predicted these dark stars to exist, but in the third edition of his famous work ‘Le System du Monde’ there was no mention of these dark stars at all.

It was in the following two centuries that amazing discoveries in science were forged, which were to help predict the existence of black holes. James Clark Maxwell’s (1865) electromagnetic theory united electricity and magnetism, which at the end of the nineteenth century were two of the known three forces in the universe, the other being gravity. Maxwell came up with four equations, which are known as the theory of the electromagnetic field, and it was with this that the first visible cracks in the Newtonian view of the universe began to show.

The second crack appeared when Albert Michelson began timing the propagation of light. In the Newtonian view of the universe space and time are absolute and the speed of light is relative. Using what is now called the ‘Michelson inferometer’, a highly accurate experimental technique, Michelson found that there was no variation in the speed of light. It was the same in all directions irrespective of motion.

It was with the advent of one physicist, Albert Einstein, which changed the fundamental nature of astrophysics. It was while working on the problem of trying to fit Maxwell’s electromagnetic laws with the Newtonian view of the universe, that Einstein in a flash of inspiration turned the known laws of physics upon its head. In one swift stroke Einstein rejected Newton’s view of absolute space and time, demanding that space and time are relative. With this he devised two new fundamental principles. 

The Principle of the absoluteness of the speed of light-Whatever might be their nature, space and time must be so constituted as to make the speed of light absolutely the same in all directions, and absolutely independent of the motion of the person who measures it.

The principle of Relativity- Whatever might be their nature, the laws of physics must treat all states of motion as relative.

These two principles started Einstein on his quest to properly explain the phenomena of the universe, which would inevitably lead to a renewed enquiry into the existence of black holes.

Einstein’s first principles led him onto some amazing discoveries: mass could be converted into energy (the famous E=MC2) and the principle that nothing could go faster than light. With this first set of relativity theory, named special relativity, Einstein turned to the problem of fitting gravity into this relativistic framework. 

It wasn’t Einstein, though, that first unified space and time. Minkowski (1908), who built on Einstein’s work, discovered that the universe is made up of a four-dimensional ‘spacetime’ fabric that is absolute and not relative, and exists independently in all reference frames. But following this discovery, which Einstein first rejected, Einstein began to develop his theory of gravity. The conclusions, which he came up with, were devastating for the Newtonian view of gravity. He proposed that space and time are warped, which made him realise that what was previously thought of as tidal gravity, was actually the manifestation of spacetime curvature (or warpage).

In 1915 published his results into marrying his relativistic laws with gravity, which he called General Relativity, and with this the renewed interest into the dark stars of Michell and Laplace began.

Karl Schwarzschild first took the tentative first step into black holes, after the publication of the general relativity theory. From Einstein’s field equation he calculated the spacetime curvature outside any non-spinning spherical star, which led to the formation of Schwarzschild geometry, which was to expand knowledge of gravity and the universe enormously. The Schwarzschild equations found that if a mass is compressed into a sufficiently small radius space-time becomes so severely distorted that even light can't escape from the force of gravity. This is the same critical circumference that Michell found more than a century earlier. The theory says that a star two or three times the mass of the sun light will not to be escape the pull of gravity. The theory also states that once these stars run out of energy, they begin to collapse inward with such tremendous force that even the powerful internuclear forces within the atoms of the star aren't sufficient to prevent it from continuing to fall in on itself until the entire mass of the star is concentrated at a point called a singularity. It is within this singularity that matter is infinitely compressed into a region of infinite density, gravity is infinite and spacetime has become infinitely curved.
The formation of a black hole begins when a star begins to contract, concentrating itself into an ever-smaller region of space. As this contraction continues the effects of gravity becomes more and more pronounced, and soon light cannot even escape the pull of gravity itself. This happens when the star reaches the Schwarzschild radius, because the escape velocity has exceeded the speed of light, which we know is absolute, and nothing can go faster than the speed of light. Nothing now can escape the clutches of the black hole.

The outer edge of the hole is called event horizon because all events beyond this region are unknown, beyond this lays the photon sphere, in which the gravitational pull of the black hole isn’t strong enough to pull light into the event horizon, yet strong enough to prevent it from leaving.

We now have showed that black holes exist in theory but the question is have they been found in actual reality. The search for black holes began as soon as the concept began to take a foothold in physics. The problem was how does one look for an object that is hidden from us? It was the Russian physicist Zel’Dovich who first proposed a method for finding the existence of a black hole in the universe. He suggested that one would have to look for a star whose light spectrum, viewed through a spectrograph, shifted from red to blue to red to blue (which indicates the Doppler shift). This is a sign that the star has a companion, and thus is in a binary system. Measurement of the lights spectra infers the speed of the star around its companion, and from that velocity you can infer the mass of its companion. If the companion is massive and no light can be detected from it then it could be a black hole. This method was mulled over a few years until a new method for the search was proposed, which like the other method required the black hole to be in a binary system. A black hole with another star beside it should be drawing matter in to itself from the star. The matter then would be spinning round the black hole like water down a plughole and as the stellar matter gets closer to the event horizon it would accelerate at ever-increasing rates. The matter would then heat up and begin to emit photons of electromagnetic radiation, and when these stellar gases are close to extinction they release x-rays of intense energy. It is these x-rays that physicists are looking for, if there part of a binary system. It is now that part of Zel’Dovich method comes into play. As was described the mass of the companion to the star is inferred from the velocity of the star. With this in mind it can be deduced whether or not the companion to the star is a black hole or not.

One candidate for this search was Cygnus X-1, which is nearly 14 million kilometres from the earth. What was found was a binary made of an optically bright and X-ray dark star with its companion being optically dark and X-ray bright. The mass of the black hole is bigger than three solar masses, and is most likely closer to sixteen solar masses. And it appears to be the brightest x-ray source in the universe. This seemed to fill all of the criteria for the companion to be a black hole, and is thus assumed to be the first black hole found in the universe.

So can we conclude now that we have successfully proved the actual existence? Well if one were to put a percentage to the surety of their existence, it would have to be that astrophysicists are at least 95% sure that Cygnus X-1 is a black hole. There is no clear signal that announces that Cygnus X-1 is a black hole, unlike other objects like neutron stars that have clear signal telling us what they are. There is hope though in this research in finding a black hole signature, which is to be found in gravitational radiation. Hopefully soon there will be gravitational wave detectors that will be able to map the locations of black holes. But black holes have inevitably been accepted as real in the minds of most physicists, and it will only be a matter of time till a firm piece of evidence to show that black holes do exist.

About the Author

Tom Feinberg has spent more than 15 years working as a professor at the University of Maine. Now he spends most of his time with his family and shares his experience about Assignment. Tom Feinberg is a right person to ask about where to find Physics Assignment.