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FAQ
Frequently Asked Questions
There are seven files you can search to see if there is an earlier answer to your question. They are, in chronological order, the most recent first:
http://www.askthephysicist.com/ask_phys_q&a.html
http://www.askthephysicist.com/ask_phys_q&a_old5.html
http://www.askthephysicist.com/ask_phys_q&a_old4.html
http://www.askthephysicist.com/ask_phys_q&a_old3.html
http://www.askthephysicist.com/ask_phys_q&a_old2.html
http://www.askthephysicist.com/ask_phys_q&a_old.html
http://www.askthephysicist.com/ask_phys_q&a_older.html
Below are some FAQs to which I will add periodically. Be sure to follow the links in the links too!
We
can turn mass into energy. Can we turn energy into mass?
Can
ice or frost form at temperatures higher than the freezing point of
water?
Do
cell phones cause cancer or other health problems?
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.)
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.)
Why
does a moving clock run slow?
Can
you give me some idea about the size of an atom?
Why
is acceleration due to gravity independent of mass?
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
LINKLINK
Why
does the speed of light have
the value 3x108 m/s and not some other value?
Why
can no object with mass go faster than the speed of light or even as
fast as the speed of light.
If
atoms are mostly empty space, why does stuff seem so solid? The first
two links here are actually to wrong answers, even though they are quite
plausible. The third link is to the actual reason, more esoteric though!
What
is gravity? Does gravity bend light? What is general relativity? What is
the equivalence principle?
Questions
involving acceleration, force, linear momentum, and Newton's second law
in special relativity.
Can
you communicate faster than the speed of light by pushing, pulling, or
rotating a very long rod or string?
Why
is E=mc2 apparently not true for photons which have
zero mass but nonzero energy?
What
happens if you drop something into a hole through the middle of the
earth?
What
are the meaning of the words heat, temperature, hot, cold?
Why
is the speed of light constant to all observers?
Questions
involving the "trampoline model" of gravity in general relativity.
Questions
involving gravitons.
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).
Who
wins a race of between a light and heavy car down a ramp? There are
several answers which this link will link to.
What
are dark matter and dark energy? My take is not mainstream!
Questions
about the twin paradox
Since
the earth is spinning on its axis, why can't we just hover and let it
spin under us? Easy traveling!
Do
things appear to be shorter if they move fast? Are things
shorter if they move fast? And similar questions about length
contraction.
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.
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.