History Channel
Season. 3 Episode. 3
http://www.history.com/shows/the-universe
http://en.wikipedia.org/wiki/The_Universe_%28TV_series%29
http://www.youtube.com/watch?v=K3uTwni_INQ
EXCERPTS:
LIGHT SPEED
186,000 miles/second
300,000 km/second
"Light is the fastest thing in the universe.
It could circle the Earth 7 times in one second.
"It took 1.3 seconds for the signal travelling gate the speed of light
to reach Neil (Armstrong) from Mission Control
and another 1.3 seconds for his reply
using radio waves to come back.
And that's 2.6 seconds without even thinking.
1.3 seconds from Moon to Earth (or vice versa)
8.+ minute from Sun to Earth.
It takes upto 44 minutes for signals to travel back and forth
to the probes exploring Mars.
More than 3 hours to Cassini at Saturn
and over 29 hours to Voyager 1,
the most distant of all now heading out of the solar system.
The nearest star is red dwarf named Proxima Centaura,
nearly 25 trillion miles away.
That's 25 followed by 12 zeroes.
1 light year = 6 trillion miles (i.e. 6,000,000,000,000 miles)
a distance light travels in one year.
SIRIUS - brightest star, 8.6 light-years away.
VEGA - 25 light years.
BETELGEUSE - 500 light years.
Its a wonderful gift of nature
that because it takes time to travel,
we're able to look back in time.
... We would have no idea what our cosmic history was
if the speed of light traveled instantaneously.
- LAURA DANLY
CRAB NEBULA - 6500 light years.
GALACTIC CORE - center of Milky Way - 26,000 light years.
ANDROMEDA - next door neighbour - 2.5 million light years.
CONSTANCY OF LIGHT SPEED - RED SHIFT
[At one hand Universe Expands, at other hand, light does not give up his constancy]
"In fact the constancy of light speed is result in an aiming tool
for measuring distance in the vastness of space.
The tool is called the Red shift.
It happens as light between galaxies travels at a fixed speed.
When the space between the galaxies expands
the light racing between them gets stretched
turning red in color.
As light goes from one galaxy to another
from a distant galaxy to our own for example
that light gets stretched along with the stretching of space
and that causes intrinsically short-wavelengthlight
like blue light
to gradually become long=wavelenght or redder light.
That fundamentally is the cause of the red shift that we see
in the spectra of galaxies.
Seeing red shifts everywhere
Hubble found that all of the universe's galaxies
were moving away from each other.
... greater the red shift the more distant the galaxy.
LIGHT HORIZON
"Its called our light horizon
a sphere 13.5 billion light years in all directions
containg everything we can see.
If we as what is happening beyond our light horizon
we have to face the fact that
the speed of light really is a barrier.
- Alan Guth
UNIFORMITY OF UNIVERSE
"If everything flew apear from the beginning
why shouldn't it be uniform?
[We know no kind of bang which in uniform]
INFLATION:
This horizon problem can be solved
by a theory that i've worked on
called INFLATION.
which is a twist on the Big Bang. - ALAN GUTH
Inflation is now the widely accepted variation
that makes the Big Bang work
without the limit imposed by the speed of light.
The faster than the speed of light expansion
sets yet another limit on what we can see from Earth
... light from them (from very very distant galaxies)
will never reach you because the space is expanding
faster than the speed of light.
GPS begins
with a networked of 24 satellites
orbiting the Earth
12,500 miles above the surface.
At any one time, the device in your car
receives signals from at least four satellites.
LENGTH CONTRACTIONS
body shrinks when moving at the speed of light for stationary observer, together with the time dilation.
The speed of light may be a constant
but only in the vacuum of space.
When light moves through things like
glass or fluids
IT SLOWS DOWN APPRECIABLY.
if it didn't,
things like telescopes
and human vision would be impossible.
If ligth didn't propagate at different speeds
through different materials.
for example we wouldn't be able to see.
Our eyes wouldn't work the same way.
In a universe where light moved at the same speed
through all materials
we would know little of the world around us.
seeing only vague blobs of dark and light.
Thats because our eyes depend on biological lenses
to focus images on our retinas.
just like lenses made of glass
they work because light slows down as it passes trough them.
Because light is absorbed by the atoms of glass
and then they re-radiate it later so there's a delay factor.
The Delay Factor also causes light to bend.
Light travels trough the glass lenses of telescopes
at about 124,000 miles per second.
2/3 of its sped through a vacuum.
"So as you try to go to faster
and faster and faster...
you actually get to a point
where it takes more and more [and more] energy...
until it's and INFINITE AMOUNT OF ENERGY
to go to speed of light." - MICHELLE THALLER
Virtually all physicists agree
its impossible to travel through space
at faster than light speed.
___________________
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