###### If my phone is in flight mode, will it emit radiation?

No they don't.Why?Because when the phone is being switched off or put into airplane mode,it sends a  "switched off "signal to the nearest MSO (A co-ordinating office for transferring phone calls).Now,the MSO updates the status of your phone number as "switched off".So when anybody calls you, it first goes to the MSO

###### Do cell phones emit more radiation while low on battery? Why or why not?

Low battery and high cell phone radiation do not form a causal relationship as is often portrayed. Battery has nothing to do with RF radiations from the cell phone.However there is an inverse relationship. In a low network area, the cell phone has to emit

###### What are some physics of everyday life?

We are living in the century of science and technology and introduction of science in our daily has transformed our lives. When people had no idea about science, even then their lives were governed by principles of different branches of science.

###### Will fusion energy be available in the next 20 years?

Since the 1950's people have been stating that controlled Fusion power plants will be available within the next 20 years, and every year it is the same thing: The next 20 years.....It is an Immense problem that has three issues:MaterialsHeatControlabilityOther than that it is easy.

###### Will fusion energy be available in the next 20 years?

Since the 1950's people have been stating that controlled Fusion power plants will be available within the next 20 years, and every year it is the same thing: The next 20 years.....It is an Immense problem that has three issues:MaterialsHeatControlabilityOther than that it is easy.

###### Why are luxury cars heavy?

Build quality of a car is one of the important aspect. If the car has robust build quality, it scores high on safety aspects. Now coming to your question of luxury cars being heavy because of features, it's not correct.Luxury cars are mostly manufactured by European companies like BMW,

###### Why are luxury cars heavy?

Build quality of a car is one of the important aspect. If the car has robust build quality, it scores high on safety aspects. Now coming to your question of luxury cars being heavy because of features, it's not correct.Luxury cars are mostly manufactured by European companies like BMW,

###### Why in astronomy is distance measured in light 'years'?

The distances which we measure in the outer space are huge. The distance on the earth are relatively small so we measure all the distance in Km, miles or meters.  To give you a simple idea the distance from earth to moon is roughly: 384,400

###### Do you believe in the possibility of extraterrestrial life?

Do you believe in aliens and why?I belive intelligent life exist elswere in the universe but i dont belive they are visiting the earthThere are millions of galaxies out there. with millions of solar systems each. to belive that there is no other planet among the untold billions of planets that exist that

###### Is thought faster than light?

It is sometimes objected that "they said no-one would ever go faster than sound and they were wrong. Now they say no-one will ever go faster than light. . ." Actually it is probably not true that anybody said it was impossible to go faster than sound. It was known

###### How is one side of the flight seeing bright sky while the other, a dark night sky?

Wow. What a question. Thanks for A2A. Aditya Suresh has asked that I simplify the answer to a school kid level. I am going to try but this is not a simple Q&A and takes a lot of 3-D visualization. However, if the kid

###### If nothing is impossible, can we move faster than light?

We know that the statement "nothing is impossible" is false.It is impossible to know both the position and momentum of a particle within a certain limit. If you precisely know the momentum of a particle it is impossible to know the position of the particle within

###### What is the most precise definition of time?

Third dimensional time is the illusion of distance between aspects of creative process of a thing, experience or situation.    Principles in the 3rd dimension are manifest in terms of seeming linear points of distance from the point of conception of a thing.  Time does not exist anywhere else, but in a slow

###### What are some interesting facts in physics?

Negative TemperatureThis is temperature that is below absolute zero, it's negatuve kelvin. You get a negative temperature when you add more heat energy to a system and it has reached maximum entropy (simplified it's a measure of the disorder in a system). Because the atoms can't get more disordered,

###### What are conditions necessary for the big rip, the Heat death/big freeze and the big crunch and bounce?

It all depends on how fast space is expanding.Rip happens when space expansion accelerates. As more and more space appears, things get pushed further faster and faster, eventually becoming stronger than the forces holding atoms together and ripping them apart.The big

###### Do we light up the world?

Thanks Jatin Rajput for A2AYes we do light up the world in our own unique ways.Feel like below are few ways of doing itSmiling a lot and more oftenHelping some one in needEncouraging someone who is feeling lowRespecting elders and loving themGiving ComplimentsPampering your close one'sPraying for people you loveWorking for human dignity and world peace

###### Why is time moving very fast after 2012?

That depends on your psychological age. It has a lot to do with how our brains work.There are 2 different setups in which our brains work. You will observe that we do not remember much of our initial childhood. Why do you think that is?

###### Do mermaids exist?

Yes!Mermaids and Mermen exist.They just don't exist in exactly the form that most people would concieve of them existing. They also exist in the future: but not in the present.Today, a pre-ancestral form of a mermaid exists.Let me explain this by way of an analogy.In the year 1900, jet airliners did not exist.That does not mean that they

###### How can art and science meet?

I am neither an artist nor scientist, but I enjoy both disciplines.Each time subject matter overlaps, art and science meet.However, art and science do not serve the same purpose and it isn't necessary for them to do so.For me, art

###### Does conservation of energy survive during time travel if we consider that time travel is possible?

If you have a time machine, you need to be able to lock up the time period you left from causality effects, effecting it.Imagine if the time machine you had could move things from the past, from the future.Move a quark out of place

###### Why does sound travel at the same speed through air?

The speed of sound is a function of the mechanical properties of the medium, (e.g., air, water, brass, etc.) in which it is traveling. In other words, sound is a mechanical wave that causes molecules in a medium to vibrate back and forth

###### Do you believe in the possibility of extraterrestrial life?

Do you believe in aliens and why?I belive intelligent life exist elswere in the universe but i dont belive they are visiting the earthThere are millions of galaxies out there. with millions of solar systems each. to belive that there is no other planet among the untold billions of planets that exist that

###### If sound traveled at the speed of light, what would happen?

For one, you would always hear thunder in synch with the flash of lightning.But, as others have suggested, it messes up a lot of known physics. Before even a what-if style question can be answered, you would have to

###### How fast does space/time travel?

As fast as you can think about them. Space and time are abstract concepts; they are thoughts, not objects, not fields of energy. We only know about space and time because we conjure these ideas to provide a context in which we can visualize the existence and motion of real objects.

###### How is one side of the flight seeing bright sky while the other, a dark night sky?

Wow. What a question. Thanks for A2A. Aditya Suresh has asked that I simplify the answer to a school kid level. I am going to try but this is not a simple Q&A and takes a lot of 3-D visualization. However, if the kid

###### How long will our sun shine?

It depends on what you mean by

###### How is motion related to balance (in the way of a spinning top or a motorcycle)?

The gyroscopic forces due to the spinning wheels play a secondary part in balancing a motorcycle. The primary balancing is by steering the wheels to be under the motorcycle. This is way you balance a broom upside down on your hand. It's what

###### What is the mechanism behind the workings of a light emitting diode?

Light is composed of photons... quanta of light. Each color of light is associated with a particular wavelength of light which in turn represents a particular energy of the photons. Visible photons, those coming from the light emitting diodes that you can see, have a range of energy between 1.75 and 3.1 electron volts, eV.Semiconductors can produce quanta of

###### How is America's NASA further ahead in the space race than the combined European space agency, ESA?

To clarify Mike Thielman the ESA budget is only about \$5.5b, which is less than 1/3 of NASA's budget.  That isn't very promising when you consider there are 320 million people in America and nearly 750 million in Europe.  The head start NASA had is a tremendous help, to be sure, but I suspect that the quantity of

###### If the sun suddenly stopped producing heat, how long would it take for the earth to completely freeze?

The earth would freeze in less than two weeks, and probably in a few months, if you are counting the oceans too. And don't count on the heat from Earth's inner core - it's down, down, very deep.Think of how much the temperatures fall on a cloudless

###### Does light loses energy as it travels?

light is an electromagnetic wave which consists of electric and magnetic vector perpendicular to each other. The key concept here is that a changing electric field produces a changing magnetic field even when no charges are present and no physical current flows. Though this mechanism electromagnetic wave propagate to infinity through a perfect vacuum without losing energy.

###### Why can't we build a spaceship that travels at half the speed of light?

Just to add to the existing excellent answers, and to highlight the mind bogglingly large amount of energy needed:Assume you want a manned mission, and assume you could engineer in the life support etc into the 90 tonne space shuttle frame,

###### Do we light up the world?

Thanks Jatin Rajput for A2AYes we do light up the world in our own unique ways.Feel like below are few ways of doing itSmiling a lot and more oftenHelping some one in needEncouraging someone who is feeling lowRespecting elders and loving themGiving ComplimentsPampering your close one'sPraying for people you loveWorking for human dignity and world peace

###### Does Dark Energy travel at the speed of light?

I can say YES, following the inverse square law as a radiating energy law and Newton and Einstein use a version of it for gravity's applied force, the gravitational waves are constantly emitted (and replaced with photons) for a net neutral energy within an atom. That means that space itself is radiating at the

###### What are conditions necessary for the big rip, the Heat death/big freeze and the big crunch and bounce?

It all depends on how fast space is expanding.Rip happens when space expansion accelerates. As more and more space appears, things get pushed further faster and faster, eventually becoming stronger than the forces holding atoms together and ripping them apart.The big

###### Is it certain that the universe is expanding rather than matter shrinking?

What silly answers. Really. There is so much information going back for so many years...sigh.Yes, it is certain. We can look at distant objects that rotate and tell the direction of the rotation because of its influence of wavelengths of light: known emission or absorption lines shift to longer

###### Which color light travels faster?

The velocity of light doesn't depend on its color. If you had asked which color light pushes electrons to move at a faster speed then it would have been the photon with greater energy; In the case of Red, Green and, Blue light

###### If light bends around a massive object, why don't sun light bend all around the circumference of earth, making day all time?

In his context, Earth is featherlight. The first measurement of this effect during solar eclipse (in 1919 by Arthur Eddington; see Tests of general relativity) was at the border of reproducibility, and modern gravitational microlensing  measurements are not much better. But the effect definitively exists, and is useful for discovery of distant, massive, dark objects.

###### Bob travels 99% speed of light versus Joe traveling 1% speed of light. Which one will pass the finish line first when traveling on earth?

Let's make a simplified racetrack. It's 1 light year long. We are sitting on the sideline watching the race.$t = \frac{d}{v}$This is the relationship between distance, time, and velocity...for the people watching the race on the (stationary) sidelines. In this case, it takes Bob about 1.01 years to

###### Are the majority of stars we see on the sky at night emitting their own light (like the sun) or just reflecting light from stars resembling the sun?

All stars only emit their own light.Suppose one star is reflecting the light. What's the distance for the nearest star? 4 light years, or something like this. Even a perfectly reflective body will have a dim light to reflect, and if you were seeing it at a distance of 4 light years too, you won't see anything.

###### What would happen if Jupiter were to collide with the Sun?

Depending on the speed of collision it'd be differentIf it's relatively slow, they'd combine, since they are made of about the same (hydrogen). the sun is about 9 times bigger than Jupiter (Relative Sizes of the Planets and the Sun: Diameter of Earth), so the sun would be a bit bigger,

###### If the earth is a sphere, how is it that wherever we stand, we never fall off?

From the phrasing of your question, it sounds like you might be thinking of "round" as in "circular", like a dinner plate.  But when people say "the Earth is round", they actually mean it's spherical - that is, in the shape of a round ball.

###### When I switch on the light, how much time does it take for the light to reach my eyes?

By far the longest chain in the sequence is for the source to start producing light. The travel time of the light itself will be much faster. Incandescent lights need to generate enough heat to reach their operating point or close to it. LED lamps have circuits that take quite

###### How can light be the example of transverse wave? It travels in straight line.

Whether a wave is longitudinal or transverse is decided by the type of vibration it causes in the medium of its propagation.A longitudinal wave vibrates parallel to the direction of its propagation (back and forth), and a transverse vibrates perpendicular to the direction of its propagation (up and down). In the propagation of light,

###### Does faster than light travel generate antimatter?

The universe probably inflated, yes. Possibly faster than light.That doesn't necessarily mean any object moved faster than light. I can make a dot of light on the moon move faster than light by flicking a laser pointer across it. That doesn't break any physical