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Quickie Questions - Phascinating Physics - Other

Date Answered Questioner (age, location) Question Answer

February 9, 2010george (age 63, florida) If our universe only had one parcel of mass, how would it's speed be measured? Speed (scalar) or velocity (vector) need of a reference frame to be defined. In your hypothetical case, the only reference frame is that unique parcel, then, for any observer on it, there won't be any change of position, or v = 0.
February 5, 2010Deanna (age 11, Michigan) What does m/s2 mean? This is the unit used to express acceleration. Acceleration is defined as the rate of change of velocity. Because the unit of velocity is meter/second (or m/s) and time is expressed in seconds, then acceleration is expressed as (m/s)/s or m/s2.
February 4, 2010Kirsten (age 10, United Kingdom) Can you please help me identify examples of physical reactons and chemical? Please! You're the best!! Two of the most common are: 2H2 + O2 2H2O (Hydrogen and Oxygen react to form water) CH4 + O2 CO2 + 2H2O (When a gas stove is lighted, methane reacts with the oxygen in the air, resulting in carbon dioxide and water vapor, and, of course, light and heat that you see as the flame).
February 3, 2010nisha (age 23, india) if i weigh the mass of a solid sphere at different place(ie;india,usa,germany etc........),would it be equal? If you are measuring the weight using an extremely accurate instrument, you would surely obtain slight changes on the measured weight, depending on your geographical location and altitud.
February 3, 2010nisha (age 23, india) if i weigh the mass of a solid sphere at different place(ie;india,usa,germany etc........),would it be equal? If you are measuring the weight using a very accurate instrument, you would surely obtain slight changes on the measured weight, depending on your geographical location and altitud.
February 3, 2010kim (age 12, phillipines) why do objects move? Since Newton's time (4 January 1643 31 March 1727) it has been known that the cause of the motion of a body is an external force applied on it.
February 3, 2010David (age 17, Australia, NSW) In Bernoulli's principle, it says that in an incompressible, inviscid liquid, a increase in velocity (i.e. kinetic energy) is accompanied by a decrease in fluid pressure and potential energy of the liquid.
What kind of potential energy is this? Gravitational? Or is it an internal energy of some sort? I can't find this anywhere... Thanks!!
Potential energy is always related with the relative positions of parts of a system. In this case, it is energy stored within the fluid as a result of the position or configuration of the different parts of that system.
February 1, 2010Devinder (age 20, India) In String theory,what are strings made of? The strings of string theory are one-dimensional oscillating theoretical lines.
January 27, 2010Nikki (age 26, colorado) What experiments have led scientists to describe the shapes of orbitals that compose the atomic sublevels? The experiments with cathode-ray tubes, oil drop experiments, Rutherford's -particle experiments, Moseley's X-ray experiment, and Chadwick's bombardment of 9Be with -particles, were all very important for the definition of the modern atomic structure.
January 27, 2010SHIVAM (age 19, INDIA) How to decide the poles of a magnet kept in space? The same way we can identify poles on earth,following the lines of force of the magnetic field. The lines always come out of the north magnetic pole, and go into the south magnetic pole. They can be observed through the interactions with the solar wind.
January 15, 2010Alexey (age 19, USA) What fourth dimmension look like? This is a hard one! Better than to try to explain a fourth-dimension space, I will let one of the best science promoters, Dr Carl Sagan, do it. See here.
January 11, 2010Mary (age 11, USA) What is the effect of chemical weathering on a rock? phyical weathering? The processes involved in chemical weathering are CARBONATION (dissolved carbon dioxide in rainwater or moisture in surrounding air forms carbonic acid and reacts with the minerals in the rock); HYDROLYSIS (chemical reaction between the minerals in the rock and hydrogen in rain water); OXIDATION (oxygen combine with water and minerals in the rock forming iron oxide. The iron-oxide crust crumbles easily and weakens the rock); SOLUTION (minerals in the rocks dissolve directly in water); and HYDRATION (minerals in the rock absorb water and expand, creating stress which causes the disintegration of rocks).
January 11, 2010Mary (age 11, USA) What is the effect of chemical weathering on a rock? phyical weathering? The processes involved in chemical weathering are CARBONATION (dissolved carbon dioxide in rainwater or moisture in surrounding air forms carbonic acid and reacts with the minerals in the rock. This process weakens the rock thus breaking it down in the process); HYDROLYSIS (chemical reaction between the minerals in the rock and hydrogen in rain water); OXIDATION (oxygen combine with water and minerals in the rock. When iron reacts with oxygen iron oxide is formed. The iron-oxide crust crumbles easily and weakens the rock); and SOLUTION (minerals in the rocks dissolve directly in water); HYDRATION (minerals in the rock absorb water and expand, creating stress which causes the disintegration of rocks).
January 11, 2010Richard (age 37, Colorado/United States) Why does your soft-drink can "sweat" more in the summer and than in the winter? Because warm air, due to its higher energy, "hold more moisture" (it is better to say that it is a more conducive environment) for gaseous water than cold air. When warm air is in contact with a cold surface, like a bottle of soft-drink, there is more moisture to condence.
January 8, 2010 (age , ) If gravity were to completely disappear from the universe would the universe reach its maximum entropy as a result of that? This is a question better answered by a expert in Cosmology, but here are my two cents: I don't believe that this hypothetical condition (an Universe with no gravity) will imply a maximum entropy condition. There is still the kinetic energy of the system available for work.
January 7, 2010jj (age 18, us) what are the properties of plasma? From our web page The Plasma State: Almost everything is made up of atoms (your dog, your science book, this computer...). The atom has a nucleus which has a positive charge. Electrons orbit the nucleus. The electrons (which have a negative charge) are attracted to the nucleus. Remember, opposites attract! But sometimes something comes along that sets the electrons free from orbiting the nucleus. Really hot temperatures can do this! When electrons are no longer trapped in orbits around the nucleus, we have the plasma state.
December 30, 2009Nthabiseng (age 13, South Africa) Is water a pure element or a compound? The water molecule is formed by two atoms of hydrogen and one of oxygen, it is a compound.
December 30, 2009Nthabiseng (age 13, South Africa) Is water a pure element or a compound? The water molecule is formed by two atoms of hydrogen and one of oxygen, it is a compound.
December 30, 2009Nthabiseng (age 13, South Africa) Why does ice float on water? Because ice has lower density than water. Visit our Density Definition Page for more information on this property of matter.
December 30, 2009balakrishna (age 43andhrapradesh, andhrapradesh/india) why inseries resisters voltage is split? This is related with the calculation of total resistance and the Ohm's Law. Resistances coupled in series are simply added (Rt = R1 + R2), the reciprocal of the net resistance from resistances coupled in parallel is the addition of the reciprocal of the values of the resistances(1/Rt = 1/R1 + 1/R2). Note that the combined resistance in parallel will always be less than any of the individual resistances. From Ohm's Law V = I*R (volts = amperes*ohms), voltage is proportional to the net resistance.
December 28, 2009steve (age 56, calif) Hi, an opportunity might present itself to use a community hiking trail to mark planetary distances along the trail, measured from a model sun at the trailhead. A brochure would compare how the sun and planets interact to make differing conditions in temperature, atmosphere, etc., all to better appreciate ecology, too. In marking planetary distances from a 50 inch sun circle, it became apparent that the location of planetary semi-major axis and peri- / ap-helions on the trail would differ by a sun radius depending on whether planetary distances are measured from the suns surface or center. The Suns radius of 435,000 [ 0.7 million km ] is within significant numbers for planetary distances and would also affect our model planets by 2 feet. It would nice to know for closer terrestrial planets. Is triangulation to the Suns surface, or its center? Thank you for any light to us on the subject. Thanks, Steve Huffey Astronomical distances are usually measured to the center of the bodies, and it is the case with distances in our system.
December 22, 2009Eric (age 12, Indiana/USA) How long would it take to go 9.461 light years ? 1 light year is the distance the light will cover traveling in a vacuum in a year (9 460 528 400 000 kilometers or 5,878,499,810,000 miles). So, to cover 9.461 light years the light needs 9.461 years.
December 22, 2009anne (age 18, philippines) in the thermospher, the temperature of an orbiting spaceship is determined by the amount of solar radiation it absorbs and not the temperature of surrounding air. if an astronaut extends his arms out his spaceship will his arm be burned? why? (the temperature in the ionosphere is 1000 degree celcius. Due to the very low concentration of particles, temperature at these altitudes describe the kinetic energy of the molecules in the medium rather than the "heat feeling" that we are used to.
December 16, 2009Alberto (age 13, Puerto Rico) What if I were on a cement platform that fell from a big building and I jumped up before the cement platform smashes on the ground?What will happen to me? Let's make a simple calculation. Any object in a free fall moves with a downward acceleration of 9.8 m/s2. That means that the vertical velocity of the object increases in 9.8 m/s (32.2 ft/s) each second. In ten seconds of free fall, the object will be moving at 98 m/s (321.5 ft/s), at 100 sec, it would be 980 m/s ( 3 215.2 ft/s). To cancel out this downward motion, you would have to jump up with a initial speed similar to these values!
October 27, 2009sreeragh (age 18, kerala/india) iheared that every object on earth is attracted towards the centre of earth, if there is no condutor for this attraction why it is telling the man in a vaccant box will fly, since he is also in the earts magnetic field, with weight. is there any conductor for magnetic field in the air? A magnetic field doesn't require of a conductor to exist, it exists between two magnetic poles.
October 16, 2009sean (age 9, WA) what is dark energy Dark energy is a hypothetical form of energy that permeates all of space and tends to increase the rate of expansion of the universe. Along dark matter they form about 75% of the matter/energy of the universe.
October 16, 2009Ashvin (age 13, Nepal) what does the electron revolves round the nucleus? In classical physics, the electron rotates around the nucleus following the Bohr "planetary model". In quantum physics, the electron does NOT rotate around the nucleus, is not just an electron any longer but instead a wave.
October 16, 2009Ashvin (age 13, Nepal) if two cars with no mass are going in the speed of light in the vaccum and the car at the back turns the headlight will it be able to see the car infront?(imagination) Forma purely physics point of view, this question does not make sense. But assuming room for a lot of assumptions, no, the front car won't be able to see the lights from the following car.
October 16, 2009Ashvin (age 13, Nepal) If we strike ball on the wall then does it returns on the same speed as we throw it or not ?if not why ? does the wall obsorb the energy of the ball ? if yes then how? In an ideal case, frequently used in introductory physics to teach the basic principles of the mechanical interaction between two bodies, there is no energy lost (it is called a perfectly elastic interaction), but this is not the case in real interactions, where there is an energy transfer between the bodies. This is the cause for a lower returning speed.
October 8, 2009RONALD (age 64, VENEZUELA) HOW CAN YOU CALCULATE THE EARTH GRAVITY (9,81 m/s2)? HAVE YOU A FORMULA? STILL TODAY IT'S ONLY A MEDITION... There are many ways to do it. The one I like, and have used in the past with my students, is using a pendulum. The period of a pendulum is given by a simple expression ( T = 2 (l/g)0.5 ), where T is the period of the pendulum (a full oscilation), l is the lenght of the pendulum string (should be aslong as possible), = pi = 3.14159265, ang g is the acceleration of a free falling object (due to gravity). It is very easy to measure T, and from this expression to obtain g.
October 8, 2009katelin (age 14, geelong) when a substance is heated its tempreture increases, what other change might be observed? Many changes occur when a substance is heated. With the increased temperature, the atoms and molecules move faster and in a less organized fashion, the dimensions of the object change, increasing both its linear dimensions and its volume. If we continue heating the substance it could reach the melting point, when a solid becomes a liquid.
October 2, 2009Stephanie (age 27, Florida/USA) The phase of matter when it reaches close to absolute zero kelvin through magnatism when all atoms become as 1. If it were possible that when atoms can reach that point would that explain a burst of energy on the opposite end of the spectrum transformed into a plasma/ or abolsute heat. Everything in the universe is based off +/-, there are 2 sides to everything like a continues circle of perfection. saying there is always a neutral between the both +/-. There are two states of matter related to temperatures close to 0 K, superfluids and the Bose-Einstein condesate.
October 2, 2009Hammad (age 18 years, Pakistan) What is difference between electric and magnetic field In the simplest possible way, there is an electric field in some region of space if electrically charged objects accelerate in a particular way, but electrically neutral objects do not. Similarly, there is a magnetic field in some region of space if objects with inherent magnetism rotate in a particular way, but objects without any inherent magnetism do not. See this article for more information.
October 2, 2009karthikeya (age 13, india) why do clouds appear in different shades of yellow and red during the time of sunset? The red colour at sunset (and sunrise) is due to an effect called Rayleigh scattering. At this time, the distance that the light has to travel to an oberver is longer, and a larger amount of blue and violet is scattered, the remanent, a longer wavelength, corresponds to red.
September 30, 2009courtney (age 13, New Zealand) Mercury is an element that is a liquid at room temerature. It is used in thermomerters to measure how hot or cold a substance is. Explain what happens to the mercury in a thermometer when it is taken out of hot liquid and placed into a cold liquid. All substances change with change in temperature (and pressure, and volume). When temperature increase there is a increasing in the volume of the mercury, and viceversa, with a decreasing temperature, the volume also decrease.
September 28, 2009Jameela (age 16, Michigan/United States of America) What happens when rays of light incident on a lens and parallel to the principal axis of the lens converge? They cross a common point known as the focus of the lense. This is the principle for parabolic antennas.
September 17, 2009Liza (age 32, Philippines) What happens when a bar magnet is heated to a vey high temperature?thank u There could be a random realigment of the atoms, resulting in a weakened magnetic field, or a magnetic field destroyed by this random realigment.
September 17, 2009Lily (age 32, Philippines) is a hydrogen atom a magnetic dipole?why? A hydrogen atom contains a single positively-charged proton and a single negatively-charged electron or, in other words, two equal and opposite charges Q separated by a distance s. The definition of electric dipole.
September 17, 2009safia (age 16, india) when do we say an electric diople is ideal one? An electric dipole consists of two equal and opposite charges Q separated by a distance s. In an ideal dipole s is very small compared to the distances to any other charges and also to any points where we wish to find the resultant electric potential or E-field. However Q is sufficiently large such that the product Qs is finite.
September 17, 2009Nathan (age 19, USA) I've been told by my physics professors that atoms can have an instantaneous connection with one another, regardless of distance. If this is so, wouldn't that "connection" be faster than any speed, including light? This is still a topic under discussion. For example, the scientific paper Nonlocality and Casuality in Quantum Electrodynamics, by Compagno and others (published in The Physics of Communication, Proceedings of the XXII Solvay Conference on Physics) debate the topic, concluding that "Our method... allows an unambiguous identification of which contribution to the evolution of one atom comes from the other..." In other words, no instantaneous connection.
September 16, 2009jessica (age 18, nd) the acceleration of gravity on the surface of Mars is 37m/s^2. if an astronaut in a space suit can jump upward 20 cm on earth's surface, how high could he jump on the surface of Mars? From the simple kinematic expression: Vf2 = Vi2 + 2gh where: Vf - Final speed (which is zero for the maximum height), Vi - Initial speed (assumed to be the same in both cases), g - acceleration of gravity for Earth (gE = 9.8 m/s2) and for Mars (gM = 3.7 m/s2), and h - height reached at each planet (hE = 20 cm). Because the final speed is zero, Vi2 + 2gEhE = Vi2 + 2gMhM Because the initial speed is the same, we get, gEhE = gMhM From where: hM / hE = gE / gM Or hM = hE * gE / gM And using the numerical values we obtain that hM = 53 cm.
August 26, 2009Marcus (age 13, Singapore) Why is space without air? Because air molecules, since they have mass (= 5.6 x 10-26 kg), are under the gravitational pull of the planet.
August 19, 2009cya (age 14, india) why are bubbles always spherical in shape? The walls of the soap bubble behaves as an elastic membrane under tension (known as surface tension). Under this tension, the membrane tends to become as small as possible, and since spherical shape has the least surface among all shapes, the bubbles tend to become spherical.
August 12, 2009Narayanan (age 14, Kerala,India) It is said that ,from the beginning ,universe has been expanding due to the conversion of dark matter to dark energy. If so, what is the force causing it? This is a very controversial topic, where no final theory has been produced and accepted by the majority of the scientists. Our web pages The Future of the Universe and An Eternal Universe offer general information on this issue.
July 22, 2009Catherine (age 54, Mo/USA) If the temperature graph of a certain experiment formed a straight line when recorded on the Celsius scale, what would a graph of the same experiment on the Kelvin scale look like? Consider the following values in Celsius (0, 10, 20, 30, 40, 50, 60, 70, 80, 90, 100). The corresponding values in the Kelvin scale are (273.15, 283.15, 293.15, 303.15, 313.15, 323.15, 333.15, 343.15, 353.15, 363.15, 373.15). Both series form a straight line.
July 16, 2009NIraj (age 15, Assam/India) what makes a string Oscillate in a frequency
is there any forces behind it?
For the oscilation to continue there should be forces acting. Once the spring is compressed by an external force, it tends to recover its original lenght under the action of an internal force known as elastic force.
June 17, 2009Bryce (age 12, Colorado) In string theory, gravitons are used to explain gravity. How do gravitons explain gravity on the quantum level? An important thing to keep in mind is that the graviton is a hypothetical elementary particle that mediates the force of gravity in the framework of quantum field theory. However, attempts to extend the Standard Model with gravitons have run into serious theoretical difficulties at high energies because of infinities arising due to quantum effects. More information here.
June 16, 2009CAROLYN (age 55, NJ) What are the four components of the water molecule. So far, I have three, including 2 hydrogens and 1 oxygen. Where in the model or diagram shown is the 4th component? Could you send the http addres of the model or diagram shown? As you pointed out, the water molecule is made of two atoms of hydrogens and 1 of oxygen. I don't know of any other element.
June 2, 2009Cariel (age 11, New Jersey, U.S.A.) How many Elements are on the Periodic Table of Elements? The Periodic Table of Elements currently has 113 elements.
June 2, 2009chances (age 16, usa) what is the chemical reaction formula for rusting There are different reactions that can be described as rusting, all of them involving oxygen in any of its forms.
May 18, 2009Narayanan (age 14, INDIA) How dark matter & dark energy is related to the expansion of universe? In physical cosmology and astronomy, dark energy is a hypothetical form of energy that permeates all of space and tends to increase the rate of expansion of the universe. Dark matter, on the other hand, is hypothetical matter undetectable by its emitted radiation, but whose presence can be inferred from gravitational effects on visible matter.
April 28, 2009aakanksha (age 14, india) how is ozone related to oxygen? The oxygen molecule is formed by two atoms of oxygen (O2), ozone is formed by three atoms of oxygen (O3).
March 10, 2009Bianca (age 12, Philipppines) What are phyisical quantities? Physical quantities are jusies physical property that can be quantified (measured and/or calculated and expressed in numbers.)
March 3, 2009cya (age 14, india) can you please explain me about despersion and bending of light? Refraction is the bending of light rays as they pass through the interface between two transparent media. This is caused by the different speed that different wavelengths have in a medium.
March 2, 2009Mike (age 61, Tx) If 2 trucks are going the same speed on level ground, one has a load of 40,000 lbs the other is empty, which truck requires more energy to maintain momentum, and would this be the same if it were 2 oil tankers, one fulll one empty and would the answer be the same if we assumed that there was no friction in either case Let me try to answer: Momentun = mass * velocity. Change of Momentum = Energy. So, the loaded truck will have a higher value of momentum, but if this value is constant, then there is no energy being used. Of course, this is assuming ideal conditions. There are factors like friction that complicate the picture. When these factors are considered, there are other expression to use. The friction produces a de-acceleration of the bodies, and a constant force (of the same value of fricton, but opposite) has to be applied. The coefficient of friction is proportional to the mass, then a higher friction will act against the motion of the heavier object, and a higher force will be required to keep the motion.
February 27, 2009Vidya (age 13, Bangalore, India) how do you know that when you pass by the event horizon of the black hole the time slows down as no one has even gone near a black hole ? Physicists, using the models most currently accepted, theorize about systems that they can't visit, including black holes. Their theories are based on previous theories tested by the scientific community, and they will be tested against new observations and experiments.
February 24, 2009Yonatan (age 10, Israel) Why isn't there ice on the ocean floor?
No radiation gets there, so how come the temperature there is 3 degrees and not below zero?
Fluids, like liquids and water, tend to circulate trying to balance the temperature everywhere. These so-called circulatio cells move energy from hot to cold spots.
February 10, 2009emy (age 17, cairo) pllzzzzzzzzzz can u tell mee more about the plazma state ? thnx for reading my question Plasma is known as the fourth state of matter. Really hot temperatures can set the electrons free from orbiting the nucleus of atoms. When electrons are no longer trapped in orbits around the nucleus, we have the plasma state. Most of the matter in the universe is found in the plasma state.
February 9, 2009Saurav (age 14, Bihar state) What is Plasma state of matter? Where can i see it? Is this visible or not? Plasma is known as the fourth state of matter. Really hot temperatures can set the electrons free from orbiting the nucleus of atoms. When electrons are no longer trapped in orbits around the nucleus, we have the plasma state. Most of the matter in the universe is found in the plasma state.
February 8, 2009kenneth (age 23, UNITED STATES) ON THIS SIDE OF THE UNIVERSE IF A STAR WAS TO EXPLODE WOULD THE SOUND OF THE EXPLOSION CARRY ON WITHOUT DIEING OUT BECAUSE THERE WILL NOT BE ANY FORCE THAT WOULD CARRY INTO A the sound into a facture of sound I mean like thier will not e any opposing force to have it die down. EXPLOSIVE The sound is a mechanic wave that NEED a medium to propagate. There is no sound trasmited in a vaccum.
February 5, 2009Rabia (age 15, Pakistan) what does it meant by forming the image infront or behind the plane mirror? Although a plane mirror makes images of the objects in front of it; these images appear to be behind the plane in which the mirror lies. In the case of plane mirrors, the image is said to be a virtual image (images formed in locations where light does not actually reach).
February 2, 2009ofelia (age 13, PENNSYLVANIA) what happens to a substance when it goes through a physical change? Physical changes between the states of matter can be produced by heating and cooling. The heat being added or substracted increases or decreases the vibration (motion) of atoms and molecules. This changes the way in which the molecules and atoms interact. For higher temperatures the molecules and atoms will have more motion, will be farther from each other, and will interact less (which corresponds to liquids and gasses), for lower temperatures the opposite happens: less vibrational motion, closer to each other, more intense interaction. This corresponds to solids.
February 2, 2009rajendra (age 30, lndore(MP)) what actual difference between classical mechanics and quantum mechanics ? Quantum mechanics is the branch of quantum physics that accounts for matter at the atomic level; an extension of statistical mechanics based on quantum theory (from wordnet.princeton.edu/). Clasical mechanics only deals with the motions of macroscopic objects.
January 28, 2009Ella (age 9, Minnesota) Is light a gas,a liquid,or a solid? Light is an electromagnetic radiation that has a dual behaviour as a wave and a particle.
January 27, 2009Gus (age 11, Washington) how fast is sunlight The speed of light in a vacuum is 299 792 458 m/s.
January 22, 2009Ashuntae (age 12, South Carolina) What is a convection current? I've got to know this for my project on the atmosphere before tomorrow because we're working on a childrn's book in science class. The movement of heat through any fluids (liquids and gases). When the substance is heated from below, the liquid or gas will expand, become less dense, and rise. When it is away from the source of heat, the opposite will occur, the liquid or gas will contract and sink.
January 22, 2009Ashuntae (age 12, South Carolina) What is a convection current? I've got to know this for my project on the atmosphere before tomorrow because we're working on a childrn's book in science class. The movement of heat through any fluids (liquids and gases). When convection current heated from below, a liquid or gas will expand, become less dense, and rise. When it is away from the source of heat, the opposite will occur, the liquid or gas will fall.
January 20, 2009ROGER (age 43, NM ) DOES STAR AGE SUPPORT BIGBANG THEORY The age of stars varies in a wide range, as it should be due to the life cycle of a star. As far as I know, the age of stars has not been use to support nor against the BB theory.
November 12, 2008jake (age 14, md united states) how can you relate newtons third law to locomotives All bodies moving at much lower speed than the speed of light follow Newton's Three Laws of Mechanics. The third law applies to a locomotive in that it allows the motion to happen. When the train wheels start to move, the contact point with the rails is moving in the opposite direction, and there is an equal and opposite force of the rails on the wheels. This par of forces (known as action-reaction forces) act simultaneously, and are the cause of the motion of the locomotive.
November 6, 2008Kylee (age 13, United States) What is kepler's 2nd law? Kepler's second law of the planetary motion: The line joining the planet to the Sun sweeps out equal areas in equal intervals of time. As a result of this law the planets move faster when they are closer to the Sun.
November 4, 2008bernadette (age 14, united kingdom) how many meters are there in 12 billion light years 12 billion light years = 1.13526341 1026 meters
November 3, 2008Howard (age 11, Canada) Can earth provide anymore energy resources such as fossil fuel? The existence of fossil fuels are limited. They are non-renewable sources of energy. We should, sooner rather than later, start producing energy from renewable sources like the Sun, wind, etc.
November 3, 2008Liz (age 12, England) What would happen to the temperature of a 1Kg block of Al at 50 degrees C if it was dropped into 1Kg of water at 20 degrees C? There would be an increase in the temperature of the water, and a decrease in the temperature of the Al. If there is no transfer of heat to the recepient or the surroundings, then the following relation -mAlcAl(T-TAl) = mWcW(T-TW) where m (mass), c (specific heat), T (equilibrium temperature), TAl (temperature of the Al block), TW (temperature of water); should be satisfied.
November 3, 2008Maria (age 15, Kansas/USA) Which of the following is not a change from liquid to gas states.
a. vaporization b. boiling c. condensation d. evaporation
Condensation is the process of changing from a gaseous to a liquid state.
October 22, 2008kerianne (age 11, ohio/usa) what form of measurement to scientist use Many, many types of measurements are used by scientists. Scientist need to measure simple magnitudes as mass, weight, height to more complex like force, electric and magnetic field, plasma concentration and energy. There are many other magnitudes but the list would be too long to compile.
October 21, 2008Dequisha (age 14, New York, United States of America) is it true that scientist seen atoms or is it a theory. If it is why would they say copper is made of atoms if they dont even know if it exists. My science book is exploring cration with physical science written by dr. jay l. wile. so please answer my question so i can understand it See by yourself this picture, or this one.
October 21, 2008sumaita (age 13, india) how does the astronauts receives messages from the earth when they are in the space since we know that the soundwaves cannot travel through vacuum but there is no air in space? You are right on that soundwaves cannot travel in space. They are mechanic waves, that require a medium to move. However, radio signals are electromagnetic waves, that do not require a medium for propagation.
October 16, 2008Colin (age 17, Ontario/ Canada) What determines that an electron will have a negative charge, a proton will have a positive charge, and a neutron will have no charge? As you said, electrons have negative charge, and protons have positive charge. The terms "positive" and "negative" are arbitrary. The essential implication of that is that the proton and electron will strongly attract each other, therefore they have opposite charges.
October 3, 2008Uri (age 59, Israel) Dear Sir
I'm 59 years old and amateur cosmologist for the last 30 years.
I have a question on Linear Chirp (http://en.wikipedia.org/wiki/Chirped_radar) energy.
The energy of electromagnetic radiation is given by E=hf.
What is the equation for the energy (instantaneous) of Linear Chirp wave?
Thanks a lot
Best regards
Uri
The instantaneous frequency of a linear chip radar varies in time following the expression f(t) = fo + kt. The energy at any given time will then be expresed as E(t)= hf(t) = h(fo + kt).
October 1, 2008patti (age 40, ohio) why is measurement a better means of describing something to a scientist than just using qualitative observation and our senses? Because scientists around the world use, in most the cases, the same measurement systems, which is void of any personal (subjective) element. In this way we can "talk" to each other using the same terms!
October 1, 2008Yadira (age 13, INDIANA) How is it possible for you to hard math??(6.67 10−11 N m2 kg−2) The first part (6.67 10−11) just means a number preceded by eleven zeros: 0.0000000000667. The second part (N m2 kg-2) is called units or dimensions of the previous number. This expressed what this number is about, in this particular case the number descibes how the gravitational force (expressed in N = Newtons, units of force) varies with the distance (m = meters) and the mass (kg = kilogram).
September 25, 2008 (age , ) Can the way that solar panels convert light into electricity be viewed as that the solar panels uses what does not change( what does not change refers to a constant, which in this case being the speed of light ) to replenish what does change, and what does change refers to what decreases, meaning the energy loss in the form of heat due to friction of 2 bodies( 2nd law of Thermodynamics )? I am not sure what your question is, but what a solar panel does is to transform the solar energy in to electric energy. There is a detailed description of the inner working of solar cells here.
September 24, 2008USMAN (age 26, PAKISTAN) WHAT IS A WEATHER FORECAST? Weather forecast is the prediction of future weather for a given location, based on the current conditions, weather patterns and the output of models developed by scientists.
September 24, 2008USMAN (age 26, PAKISTAN) WHAT IS A WEATHER FORECAST? Weather forecast is the prediction of future weather for a given location based on the current conditions, weather patterns and the output of models developed by scientists.
September 8, 2008ayan (age 20, india) what is the reason(mechanism) of existence of "inertia"? There is no reason or mechanism for inertia, it is a general property of matter to tend to keep their state of motion or to tend to stay at rest.
September 8, 2008ayan (age 20, india) what is the reason(mechanism) of existence of "inertia"? There is no reason or mechanism for inertia, it is a general property of matter.
September 3, 2008SUNNY (age 14, INDIA) WHAT ARE PROPERTIES OF PLASM STATE OF MATTER ? Plasma state is where a gas becomes a collection of negatively charged electrons which have escaped the pull of the nucleus and ions which are positively charged because they have lost one or more electrons. More information on our web page Plasma State.
September 1, 2008deepti (age 16, india) i need to know about curvature of space PLease, visite This page for a detailed answer to your question.
September 1, 2008Zach (age 16, Nevada) Here in nevada we have many problems with high temp.
My question is is there any way to actually stop the heat from transfering to other objects, or does heat win every time?
There are many methods to slow down to a minimum the transfer of heat. But because the transfer of heat is just the transfer of kinetic energy from molecules, atoms and elemental particles to other, it is impossible to create the "perfect insulator".
August 29, 2008Thu (age 17, United Kingdom) Why does some liquids mix together while other does not? Actually, all liquids mix together, it just depends on the right amount of energy (heat, motion, etc) given to the system. For example, oil and vinegar do not mix under normal conditions, but it just requires a little shaking for them to mix. Other examples would require heating, or pressing, etc.
August 24, 2008jugal (age 12, west bengal, india) where else is the concept of density used in daily life ? Everywhere. density is a characteristic of all matter (mass/volume).
August 21, 2008Crystal (age 19, CA) The specific heat of water is 4.2 joules/g celc. If you wish to heat 300 grams of water from 30 degrees celc, how much heat will be required? The temperature to reach is necessary to answer your question.
August 21, 2008aheli Pul (age 13, India) What is the shape of a water bubble in space and why? In the Earth due to the gravity it is in the shape of a tesr drop. Does water evaporate in space. if it is so then where the evaporated water go. The espherical shape is the minimum energy shape. All bodies, in the absence of external forces, will tend to this shape.
August 21, 2008aheli Pul (age 13, India/jamshedpur) What is the shape of a water bubble in space and why? In the Earth due to the gravity it is in the shape of a tesr drop. Does water evaporate in space. if it is so then where the evaporated water go. The espherical shape is the minimum energy shape. All bodies, in the absence of external forces, will tend to this shape.
August 20, 2008Genevieve (age 14, Texas) he most common elements in the earths crust are rarely found on their own, they are usually found combined; why is this? Because chemical elements tend to react among them, forming new substances as a result.
August 14, 2008sharanya (age 13, karnataka,India) why is ligtning not caused when it is not raining? Actually it does. It is very common to observe lightining with no rain.
August 14, 2008sharanya (age 13, karnataka,India) Of course, water contains oxygen,why does not it help in burning? The hydrogen in the water molecule has already reacted with the oxygen. It is not available for further reaction with air, neccesary for burning.
July 1, 2008Michael (age 9, NSW,Australia) How much is a lightyear? 1 lightyear = 9.4605284 1015 meters, which is the same as 9 460 528 400 000 000 meters, or 9 460 528 400 000 km, or 5 878 499 810 000 miles.
June 18, 2008Nathan (age 12, Texas) How many other dimensions are there? And how would they affect humans if we were in them? Physical theories have predicted for a long time the existence of other dimensions. So far there are no concrete proof in favor or against them.
June 17, 2008 (age , ) Any object that can be accelerated up to a speed greater than the Escape Velocity (about 11.2 kilometers per second), will abandon our planet.
May 29, 2008anthony messere (age 24, haynnis ma) is the big rip dangerouse. should i be worried in this life time. pluss gamma rays scare me. I wouldn't worry too much. The authors of this cosmological hypothesis, in which the matter of the universe is progressively torn apart by the expansion of the universe, calculate that the end of the universe would be in approximately 50 billion years.
May 23, 2008Krista (age 10, Philippines) How do scientists measure each planets?atmosphere? or even the sun? Scientists use multiple methods to measure the celestial bodies and their distances. From parallax, used by Cassini in 1672 to measure the distance to Mars, to Issac Newton's Law of Universal Gravitation used to obtain the mass of the Sun and the planets, science is continuosly advancing our knowledge of the planets and other celestial bodies.
May 22, 2008Renae (age 12, Washington) How do scientists measure to find out how old rocks are? There are different methods (of diverse accuracy) to date rocks. One of the most used is radiocarbon dating. It uses the naturally occurring radioisotope carbon-14 (14C) to determine the age of carbonaceous materials up to about 60,000 years.
May 22, 2008brendan (age 5, pipersville PA) Could you please explain density to me? I am doing a liquids project for preschool
Thanks
Density is a characteristic of each substance that represents the amount of mass in each volume unit. In other words, if we obtain the mass of an object (a weight scale can be used, although mass and weight are not exactly the same), and the volume of a liquid (or gas or solid), then we can divide the mass by the volume (density = mass/volume) to obtain the density. For example, ice has higher density than water, and this is the reason for ice to float!
May 7, 2008eloisa (age 14, philippines) are there any more example for sublimation aside from drying ice? Sublimation a transition from the solid to gas phase with no intermediate liquid stage. Sublimation, as any other phase change, depends of three factors, temperature, pressure and volume. Most substances would be able to sublime controlling these parameters. There are other compounds, besides dry ice, that sublime at atmosheric pressure. For example, ionide would sublime with a light heating and snow also sublime (slowly) at below-freezing temperatures.
May 2, 2008Chris (age 46, Florida, U.S.A.) If a device could be constructed that would allow you to travel to the center of the Earth, (it could get you there, protect your body, etc.) what sort of gravitational force as well as centrifugal force could you expect? The answer to this question is very complicated because the many different factors acting simultaneously. A detail answer must include factors such as radioactivity, temperature of the core, variations in density, rotational motion, etc. There is also the issue that the center of the earth is not exactly the gravitational center. For a simple, uniform solid sphere, with an empty center, the gravitational force would be cero in the center, but this is far from the real case of our planet.
April 30, 2008Cameron (age 13, Ohio/U.S) Why do solar cells produce more electricity in low temperatures? A detailed answer to your question is beyond this section, but you can find it here.
April 30, 2008Cameron (age 13, Ohio/U.S) Why do solar cells produce more electricity in low temperatures? A detailed answer to your question is beyond this section, but you can find it here.
April 24, 2008 (age , ) What kind of rock is halite: a sedimentary rock, an igneous rock, or a metamorphic rock? Halite occurs in beds of sedimentary minerals that result from the drying up of enclosed lakes, playas, and seas. Halite is the mineral form of NaCl, commonly known as rock salt.
April 24, 2008Sandira (age 14, Nassau,Bahamas) The weight of all layers of the atmosphere creates what type of force? The weight of all layers of the atmosphere on each square centimeter is called ATMOSPHERIC PRESSURE.
April 23, 2008Azfarihin (age 12, Singapore) With the earth rotating, revolving and hurtling through space at fantastic speeds, why can't we feel the movement?Why does everything appear to be motionless? The short answer is because we are moving WITH the earth at the same rate. It is like being in a car that moves at a constant speed on a smooth, long and straight highway, if we close our eyes we will not feel the motion, unless the car accelerates, turn or break.
April 18, 2008Alex (age 18, Minnesota/ USA) What is the KE of the Earth with respect ot the sun as the sum of two terms, that is due to the daily rotation about its axis, (Assuming the the Earth is a perfect sphere, with a mass of 6.0*10 to the power 24 kg, and radius of 6400000 meters, and a distance from the sun 150000000 meters The TOTAL kinetic energy of an object in motion is obtained by adding the translational term (Kt = 1/2 mV2, where m is the mass of the object and V its translational or lineal velocity) and the rotational term (Kr = 1/2 Iw2, where I = mr2, and w is the angular speed).
April 9, 2008chamisa (age 35, va) besides the stars what is another example of plasma? Lightning, the Sun, Nebulae, Solar Wind, Auroras, Quasars, Radiogalaxies, and Galaxies are all examples of the plasma state.
April 8, 2008MUENCH (age 11 , US) WHAT PLANET DISCOVERED BY MATHEMATICS? Although Neptune was physically discovered on September 23, 1846 by the astronomer Johann Galle, is existence was predicted before by a young British astronomer and mathematician , John C. Adams, in 1843. The discovery of the asteroid belt is also a good example of how mathematic has helped the astromers.
April 8, 2008Jared (age 17, Iowa) As light travels through water, does the refraction index (and thus the speed) change as the temperature of the water changes? Absolutely, the relation between the refraction index (n) and temperature (T) expressed in Celsium is given by the expression: dn/dt = -0.0004 1/oC
March 31, 2008mary ann (age 16, philippines) why are the spetral lines of many stars shifted toward the red end of the spectrum? This effect, first described by Christian Doppler in 1842, relates the change on the frequency (in this case color) with the direction of the motion. The shift to red indicates that all celestial bodies are moving farther from each other.
March 25, 2008VARSHA (age 17, INDIA) WHY DOES THE PLANETS MOVE FASTER WHEN IT COMES NEAR TO THE SUN.? This is a result of the universal law of conservation of energy. A planet orbiting a star has two forms of energy, Kinetic Energy (K, energy associated with the speed of its motion) and Gravitational Potential Energy (P, energy associated with the gravitational attraction of the two objects). From these concepts it is straightforward that for greater distances between the star and the planet, the greater the potential energy will be. Now, from the law of conservation of energy, K + P = constant. So, when the planet is closer to the star, P is small, and, to conserve K+P constant, K, and the speed, should increase.
March 20, 2008Rachna (age 15, Toronto, Canada) what feature of clouds allows them to reflect the light and heat of sunlight In general, light-colored objects reflect better heat and sunlight.
March 19, 2008Dustin (age 14, Ohio / USA) What is the advantage of radio waves? Radio waves are a form of electromagnetic radiation. Through them we can communicate all around the planet, with satellites, shuttles and the International Space Station. Scientists study the Sun and the Universe using radio telescopes. Our web page Radio Waves offers more information on this topic.
March 19, 2008Dustin (age 14, Ohio / USA) What is the advantage of radio waves? Radio waves are a form of electromagnetic radiation. Through them we can communicate all around the planet, with satellites, shuttles and the International Space Station. Scientists study the Sun and the Universe using radio telescopes. Our web page Radio Waves offers more information on this topic.
March 18, 2008Ksnake (age 21, Dubai/UAE) how does current follows the electric field intensity differences in a circuit ? The Electric Potential Difference, commonly known as "voltage", is define as the work needed to move a charge between two points. The direction of the electrons movement (electric current) is from the negative pole to the positive one, but by convention the positive sense of the current is from (+) to (-). It should be mentioned that the intensity of the electrical current is only a function of the resistance of the conductor.
March 17, 2008Mahima (age 18, india) how can earth take and give any number of electrons? Not only our planet, everything in the universe is constantly taking and giving away charged particles. This is part of the normal interaction at atomic level.
March 5, 2008JAMIE (age 13, NAUGATUCK) WHAT ARE NEWTONS THREE LAWS? First Law (Inertia): Every object in a state of uniform motion (or rest!) tends to remain in that state of motion unless an external force is applied to it. Second Law (Force): If a force F is applied on an object of mass m, it will acquire an acceleration a proportional to the force F (F = ma). Third Law (Action-Reaction): For every action there is an equal and opposite reaction.
February 15, 2008Denese (age 12, Tennessee) What are the three atoms that make up the ozone layer? A molecule of ozone is made up by three oxygen atoms.
February 11, 2008Ian (age 17, ON) You know how there are only two charges. Positive and negative. Their laws state that opposites attract and likes repel. Is there any way of changing the properties of charges. Sorry I really don't know how to word this question. Thanks for your time. This is a basic principle of the interaction of charged particles. There is not, as far as I know, a way to change this interaction.
February 11, 2008Ian (age 17, Burlington ON) If neutrons have no charge then what is their purpose of the atom or do they do anything at all? Like the rest of the particles, neutrons do not need a purpose, they exist, they just are.
February 11, 2008Ian (age 17, ON) If neutrons have no charge then what is their purpose of the atom or do they do anything at all? Like the rest of the particles, neutros do not need a purpose, they exist, they just are.
February 11, 2008Ian (age 17, ON) Theoretically is it possible to heat something to a certain extent that the electric fields of the atoms would dissapate? When an atom is accelerated to a high velocity, the electric charges and the absolute electric field around those charges do not have to change in order to remain compatible with the principle of mass-energy conservation. More information here.
February 11, 2008AKuah (age 11, New Jersey) What ar the particles of matter? All matter is composed by molecules and atoms. The atom is composed by neutrons, protons and electrons, which are called elemental particles.
February 6, 2008Stephanie (age 10, California) If you are going 70mph straight in the freeway and you threw a baseball in the air, would it land in the same spot? From your point of view, assuming you are in the same auto, the ball will go straight up and down, and will land in your hands, but for somebody standing on the side of the road, the ball will follow a parabolic (ballistic) trajectory, at the same time that you are moving in a straight line. This observer will see, as you do, that the ball will land in your hands.
February 3, 2008Ian (age 17, ON) What is wave particle duality? In Physics, waveparticle duality is the concept that all matter exhibits both wave-like and particle-like properties.
February 3, 2008Ian (age 17, ON) What is quantum entanglement? The Standford Encyclopedia of Philosophy defines quantum entanglement as a physical resource, like energy, associated with the peculiar nonclassical correlations that are possible between separated quantum systems. This article discusses the topic in a very interesting way.
February 3, 2008Ian (age 17, ON) My physics teacher likes to rant about how when you touch something you are not actually touching it at all it's just the exchange of electrons. Is this true or is it different or am I right? In a macroscopic scale, the act of touching consist in bringing in contact our fingers and abother object. In microscopic physics "touch" can not be defined in the same way, the interaction of subatomic particles blurr the act of touching.
January 24, 2008Anudip (age 18, India) According to releativity theory Mass and Energy can be converted to each other, is it possible to convert any known mass to energy and energy again to mass? Can you explain me this phenomenon with example. The idea of the mass-energy equivalence as a general principle was proposed by Albert Einstein. His well known expression E = mc2 uses as the equivalence factor the square of the speed of light (299,792,458 m/s)2. Is due to this high value that the conversion between mass and energy is not easily observed at velocities much lower than the speed of light.
January 24, 2008Chiranjeev (age 11, India) How does a spacecraft flies in space where there is no air? Spacecrafts fly in space based on a physical principle known as "The Law of Momentum Conservation". Momentum is defined as mass times velocity P = m V). This principle states the in the absence of a net external force, the net momentum of a system remains constant (dp = 0), so, if the mass of a system decreases, the speed will increase. After a given speed is reached the ship will continue its motion due to the inertia.
January 24, 2008Chiranjeev (age 11, India) How does a spacecraft flies in space where there is no air? Spacecrafts fly in space based on a physical principle known as "The Law of Momentum Conservation". Momentum is defined as mass times velocity P = m V). This principle states the the net momentum of a system remains constant (dp = 0), so, if the mass of a system decreases, the speed will increase. After a given speed is reached the ship will continue its motion due to the inertia.
January 24, 2008maddie (age 13, virginia/usa) how/why does a solid sublimate? At normal pressures most sustances are able to exist in three different states at different temperatures. For example, when increasing temperature a solid will transition to a liquid state and, if we continue increasing temperature, the liquid will transition to gaseous state. However, for some elements or substances at some pressures the material may pass directly from solid to the gaseous state. This happens when the exterior pressure exerted on the substance is too low to stop the molecules from escaping from the solid state.
Last modified November 6, 2008 by Eduardo Araujo-Pradere.

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