It took 300 years of experiment and calculation to
pin down the speed at which light travels in a
vacuum: an impressive 186,282 miles per second. Light will travel slightly slower than this through air,
and some wild experiments have actually slowed
light to a crawl and seemingly made it go backward, but at the scales encountered in our everyday lives, light is so fast that we perceive our
surroundings in real time.



Look up into the night sky and this illusion begins
to falter.
"Because light takes time to get here from there, the
farther away 'there' is the further in the past light
left there and so we see all objects at some time in
the past"... explains Floyd Stecker of NASA's
Goddard Space Flight Center in Greenbelt, Maryland..

Light-years..
We see the relatively close moon as it was 1.2
seconds ago and the more distant sun as it was
about 8 minutes ago. These measurements—1.2
light-seconds and 8 light-minutes—can be thought
to describe both time and distance. The distance to more remote objects such as other
stars is so great it is measured in light-years—the
distance light will travel in a year, or about 6 trillion
miles (10 trillion kilometers).. Even the nearest star
system, Proxima Centauri, lies more than four light-
years away, so it appears to us on Earth as it was just over four years ago when the light began its
journey. In this way, light's finite speed gives us a valuable
view into the past, and as we strain our gaze
deeper into the universe we look further back in
time. "In the case of distant galaxies, we see them as
they were billions of years ago when the universe
was relatively young" Stecker said...
Out of sight
Some galaxies are so remote that their light hasn't
had sufficient time to reach us yet, despite about
13.7 billion years of travel. There could also be
more distant objects that will forever remain
unknown to us. "Because the universe is expanding and the
expansion appears to be accelerating, there may
be distant galaxies which if we can't see them now
because their light has not had time to reach us, we
will never see," Stecker said. So we can never see the universe as it is, only as it
was at various stages of its development. To interact with remote parts of the universe—to
see them as they are now—would require some
exotic means of travel, such as to travel faster than
light which, according to Einstein's special theory of relativity, is impossible as it would require an infinite amount of energy. "The equations of special relativity imply that
nothing can go faster then the speed of light in
empty space. Therefore, if super-luminal speeds are
possible in empty space, they violate the principle
of special relativity," Stecker told SPACE.com. Offbeat theories There are ways to travel faster than light that do not
violate special relativity, but these either outpace
light in a transparent medium such as water or do
not involve the transmission of information. To break light speed in space and gain the same
easy interaction with the universe that we
experience everyday on Earth is a task considered
practically impossible even when offbeat theories
are considered. "There are some postulated but unproven
theoretical models, inspired by the motivation to
unite the quantum theory with the general theory
of relativity, which violate special relativity," Stecker
said. These theories involve accelerating particles with
mass to super-luminal speeds using ultra high
energies. It may also be possible to take a shortcut
to distant parts of the universe through a tunnel in
space-time known as a wormhole. "If stable wormholes can exist in space-time and if
we can survive traveling through them, then they
could provide shortcuts as in the sci-fi movies,"
Stecker said.

Let me have your number on this thread, so that I will send you the video on your whatsapp. Too much eyes on the other thread and hiding of posts.

kevoh:
Let me have your number on this thread, so that I will send you the video on your whatsapp. Too much eyes on the other thread and hiding of posts.

okay..