- 4132 - LIGHT - the fastest known thing. Light is faster than anything else in the known universe, though its speed can change depending on what it's passing through. Light slows down when it passes through air, glass, water, etc. It is only fastest in a vacuum.
-------------- 4132 - LIGHT - the fastest known thing.
- The universe has a speed limit, and it's
the speed of light. Nothing can travel faster than light , according to the
laws of physics.
-
- Light moves at an incredible 186,000 miles
per second (300,000 kilometers per second), equivalent to almost 700 million
mph. That's fast enough to circumnavigate the globe 7.5 times in one second,
while a typical passenger jet would take more than two days to go around once
(and that doesn't include stops for fuel or layovers!).
-
- Light moves so fast that, for much of human
history, we thought it traveled instantaneously. As early as the late 1600s,
though, scientist Ole Roemer was able to measure the speed of light (usually
referred to as “c”) by using observations of Jupiter's moons.
-
- Around the turn of the 19th century,
physicist James Clerk Maxwell created his theories of electromagnetism. Light
is itself made up of electric and magnetic fields, so electromagnetism could
describe the behavior and motion of light including its theoretical speed.
-
- That value was 299,788 kilometers per
second, with a margin of error of plus or minus 30. In the 1970s, physicists
used lasers to measure the speed of light with much greater precision, leaving
an error of only 0.001. Nowadays, the speed of light is used to define units of
length, so its value is fixed; humans have essentially agreed the speed of
light is 299,792.458 kilometers per second, exactly.
-
- Light doesn't always have to go so
fast. Depending on what it's traveling
through air, water, diamonds, etc. it can slow down. The official speed of
light is measured as if it's traveling in a vacuum, a space with no air or
anything to get in the way. You can most clearly see differences in the speed
of light in something like a prism, where certain energies of light bend more
than others, creating a rainbow of light.
-
- The speed of light is no match for the vast
distances of space, which is itself a vacuum. It takes 8 minutes for light from
the sun to reach Earth, and a couple years for light from the other closest
stars (like Proxima Centauri) to get to our planet. This is why astronomers use
the unit light-years, the distance light can travel in one year, to measure vast
distances in space.
-
- Because of this universal speed limit,
telescopes are essentially time machines. When astronomers look at a star 500
light-years away, they're looking at light from 500 years ago. Light from
around 13 billion light-years away (equivalently, 13 billion years ago) shows
up as the cosmic microwave background, remnant radiation from the Big Bang in
the universe's infancy.
-
- The speed of light isn't just a quirk of
physics; it has enabled modern astronomy as we know it, and it shapes the way
we see the world, literally.
-
-
August 28, 2023 LIGHT
- the fastest known thing. 4132
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