Frequently Asked Questions

With the recent publication of PHYSICS IS... there are now three Ask the Physicist books! Click on the book images below for information on the content of the books and for information on ordering.

Can an airplane take off when on a trendmill which keeps the plane from moving forward?

LINK

There is an absloute minimum of temperature. is there an abslolute maximum?

LINK

Questions like "if there are birds in a box and they are flying, what does the box weigh".

LINK LINK LINK LINK

Questions about artificial gravity in a rotating cylinder.

LINK LINK LINK

Can a particle be in two places at the same time?

LINK LINK LINK

Questions about sci-fi and video game guns.

LINK LINK LINK LINK LINK

Questions like how long does it take for one object to fall into another because of gravity or electrostatics.

LINK LINK LINK LINK LINK

Questions involving escape velocity.

LINK LINK LINK

Questions about muscles doing work

LINKLINK

We can turn mass into energy. Can we turn energy into mass?

LINK

Is it true that a particle can be in two places at the same time?

LINK

Can ice or frost form at temperatures higher than the freezing point of water?

LINK LINK LINK LINK LINK

Do cell phones cause cancer or other health problems?

LINK

How much force is needed to make something have a certain speed. (First, note that this question has no answer. For the details see the link.)

LINK

A related question: How much force is felt when one object hits another, like dropping something on somebody's head or when one car collides with another. (Again, note that this question has no answer. For the details see the link.)

LINK LINK

Why does a moving mass have more mass (inertia) than when at rest?

LINK

Why does a moving clock run slow?

LINK

Can you give me some idea about the size of an atom?

LINK

Why is acceleration due to gravity independent of mass?

LINK

What was there before the big bang? Where did the big bang come from?

I will answer that right here after many times giving this answer: nobody knows.

Questions about air friction (drag, air resistance) and terminal velocity.

LINK LINK LINK LINK LINK LINK LINK LINK LINK LINK LINK LINK

Why does the speed of light have the value 3x10⁸ m/s and not some other value?

LINK

Why can no object with mass go faster than the speed of light or even as fast as the speed of light.

LINK

If atoms are mostly empty space, why does stuff seem so solid? The first two links here are actually the wrong answer, even though they are quite plausible. The third link is to the actual reason, more esoteric though!

LINK LINK LINK

What is gravity? Does gravity bend light? What is general relativity? What is the equivalence principle?

LINK LINK LINK

Questions involving acceleration, force, linear momentum, and Newton's second law in special relativity.

LINK LINK LINKLINK

Can you communicate faster than the speed of light by pushing, pulling, or rotating a very long rod or string?

LINKLINK

If a stick is long enough, can you rotate it fast enough to have the end go faster than the speed of light?

LINK

Why is E=mc² apparently not true for photons which have zero mass but nonzero energy?

LINK

Why is the sky blue? Why are clouds white?

LINK LINK

What happens if you drop something into a hole through the middle of the earth?

LINK

What are the meaning of the words heat, temperature, hot, cold?

LINK

Why is the speed of light constant to all observers?

LINKLINKLINK

Questions involving the "trampoline model" of gravity in general relativity.

LINKLINK

Questions involving gravitons.

LINK LINK

What is the speed of gravity?

LINK

If you shine a flashlight forward in a fast-moving spacecraft, why does the light not go faster than the speed of light (and similar questions like this).

LINK

Who wins a race of between a light and heavy car down a ramp? There are several answers which this link will link to.

LINKLINK

What are dark matter and dark energy? My take is not mainstream!

LINKLINKLINK

Questions about the twin paradox

LINK

Since the earth is spinning on its axis, why can't we just hover and let it spin under us? Easy traveling!

LINK

Do things appear to be shorter if they move fast? Are things shorter if they move fast? And similar questions about length contraction.

LINKLINK

Do clocks appear to be go slower if they move fast? Do clocks run slower if they move fast? And similar questions about time dilation.

LINKLINK

Newton's third law says that for every action there is an equal and opposite reaction. Then why can anything ever move since the sum of all forces is zero.

LINKLINK