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# Just a big question...

## Just a big question... - Physics Forum

### Just a big question... - Physics Forum. Discuss and ask physics questions, kinematics and other physics problems.

#1
05-07-2005, 04:10 AM
 rahemanvelji@yahoo.ca Guest Posts: n/a
Just a big question...

There is a guy named Mavis on a space ship. The space ship is at rest
and he measures the ship to be "60m" long. The ship then accelerates
to a speed of "0.8c", where "c" is the speed of light. Now, due to
relativity Mavis will no longer measure the ship to be "60m". Instead,
the length of the ship as measured by Mavis will be longer than "60m".

I'm sure you are all familiar with the equation

"l = 1/y * l_o"

where
"l" is the length of the space ship at rest and equals "60m"
"l_o" is the length of the ship travelling at "0.8c" as measured by
Mavis
"y" equals "1/sqrt(1-vē/cē)"

Now "1/y" equals "0.6".

So "l_0" equals "100m".

Now, Mavis can measure the ship in various ways. If he measures the
space ship using light signals he will find that the ship is "100m"
long. However, if he measures the ship with a ruler he will find that
the ship measures "60m". The reason why the ship hasn't expanded when
measured with a ruler is because the ruler *itself* has also expanded!

This leads to the Big Question:

the Big Question #1: Does this not contradict Einstein's first
postulate, the Principle of Relativity, which states that "the laws of
physics are the same in every inertial frame of reference." Because
obviously if Mavis can figure out what velocity the ship is travelling
at then there must be an absolute frame of reference, that is, a frame
of reference from which to measure the velocity of the ship.

Here's another way of looking at it:

We all are familiar with the fact that "relativistic mass" and "rest
mass" are related by the following equation:

"m_r = y * m"

where
"m_r" is the "relativistic mass"
"m" is the "rest mass"
"y" equals "1/sqrt(1-vē/cē)"

Let's say that we have a brick on a scale on the Earth. Right now it
weighs "3 kg". Now, what if by some extraordinary spacial event that
the Earth was sent out into space accelerating till is acquired a
velocity of "0.8c". Now, the relativistic mass of the brick will be "5
kg". The scale will definetely weigh the brick to be more than "3 kg"!

the Big Question: Does this not contradict Einstein's first postulate,
the Principle of Relativity, which states that "the laws of physics are
the same in every inertial frame of reference." Because obviously if
Mavis can figure out what velocity the ship is travelling at then there
must be an absolute frame of reference, that is, a frame of reference
from which to measure the velocity of the ship.
----

You can view my paper (which will be completed pending the answers to
this message)

"A Collection of Ideas" at...

....[Only registered users see links. ]

#2
05-07-2005, 09:12 AM
 Martin Hogbin Guest Posts: n/a
Just a big question...

Wrong, Mavis will measure the length to be 60 cm.

..> ..[Only registered users see links. ]

Why not try to understand a theory before attempting to
criticise it?

Martin Hogbin

#3
05-07-2005, 11:24 AM
Just a big question...

<[Only registered users see links. ]> wrote in message

Wrong.

Mavis is *ON* the space ship, so he must not be moving relative to the space
ship.

Due to the Principle of Relativity, his ship will *always* have the same
length *AS MEASURED IN ITS OWN FRAME OF REFERENCE*.

Somebody with whom the ship has a *relative* motion will get a different
result, depending on the *relative* velocity.

There is a *reason* it is called the "Theory of Relativity."

Tom Davidson
Richmond, VA

#4
05-07-2005, 07:53 PM
 Prai Jei Guest Posts: n/a
Just a big question...

tadchem (or somebody else of the same name) wrote thusly in message
<[Only registered users see links. ]>:

Crucially this somebody will also see Mavis' ruler shrunk in the same
proportion as the spaceship itself.

A *guy* named Mavis?!? The only Mavis I know is the female of the species.
--
A couple of questions. How do I stop the wires short-circuiting, and what's
this nylon washer for?

Interchange the alphabetic letter groups to reply
#5
05-07-2005, 09:35 PM
 N:dlzc D:aol T:com \(dlzc\) Guest Posts: n/a
Just a big question...

Dear Prai Jei:

"Prai Jei" <[Only registered users see links. ].uk> wrote in message
news:d5j60f\$fin\$[Only registered users see links. ].pol.co.uk...

I didn't know any guys named Carol, either.

David A. Smith

#6
05-08-2005, 01:32 AM
Just a big question...

"N:dlzc D:aol T:com (dlzc)" <N: dlzc1 D:cox T:[Only registered users see links. ]> wrote in

Would Carroll O'Connor count? ("Archie Bunker"):
[Only registered users see links. ]

I didn't think Marion was a man's name until I heard that Marion Michael
Morrison changed his name to "John Wayne":
[Only registered users see links. ]

Tom Davidson
Richmond, VA

#7
05-08-2005, 04:00 AM
 N:dlzc D:aol T:com \(dlzc\) Guest Posts: n/a
Just a big question...

news:[Only registered users see links. ]...

I was thinking of my ex-father-in-law.

.... and then there was "The Boy Named Sue". ;>)

David A. Smith

#8
05-08-2005, 10:08 PM
Just a big question...

"N:dlzc D:aol T:com (dlzc)" <N: dlzc1 D:cox T:[Only registered users see links. ]> wrote in

I knew one of those, once, but *he* spelled it "Sioux" - on his leathers
*and* his chopper.

Tom Davidson
Richmond, VA

#9
05-09-2005, 08:44 PM
 Prai Jei Guest Posts: n/a
Just a big question...

tadchem (or somebody else of the same name) wrote thusly in message
<[Only registered users see links. ]>:

What about the late JP2? That was his name (though it might have been spelt
with a K) before he was elected.

The Marion who lives next door to me is definitely the female of the
species.

--
A couple of questions. How do I stop the wires short-circuiting, and what's
this nylon washer for?

Interchange the alphabetic letter groups to reply

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