Light

```Speed of light
A race to compare the speed of
light to other things

A quick comparison of how far things can
go in 1 second.
Start
Fastest Athletes
Cheetah
Fastball
Drag racer
Bullet
Supersonic Jet
Crack of thunder
Flash of lightning
10 m
25 m
45 m
Most are still going
We will continue these throughout the presentation!
They are roughly to scale.
Drag Racer
Bullet (still going)
Supersonic Jet (still going)
Crack of thunder
Flash of lightning
175 m
Astronomical Distances




Light takes 8 minutes to get from the Sun to the
Earth.
It takes 4 years to get here from the next nearest
star aside from the sun, Proxima Centauri which
is 4 light years away.
Light year-The distance light travels in one year
9.5 x1015 m (a really big distance)
Space travel problems

Since we can’t even get close to the speed
of light deep space travel would take
extreme amounts of time.
crack of thunder (340 m)
Looking into the past



Every time you look at the stars you are
looking at the distant past.
If you see a star that was 100 light years
away blow up (supernova) it actually blew
up 100 years ago.
It just took the light that long to get to you.
Speed of light in things other
than a vacuum




Whenever light hits a medium it slows it
down.
The more dense the material the slower
light can travel.
Therefore light tends to travel faster in a
gas, and slowest in a solid.
It travels fastest in a vacuum (nothing)
Speed of light in different
substances
Vacuum
2.99792458 x 108 m/s
Air
2.9970 x 108 m/s
Water
2.26 x 108 m/s
Glass
1.97 x 108 m/s
Diamond
1.24 x 108 m/s
Bullet (780 m)
It may slow down but…


It is still unbelievably fast compared to
everything else.
You can not travel faster than the speed of
light. Several interesting things happen
when you get close.
Supersonic Jet (900 m)
How far will that light go
If I had 15,000 more slides just like this one, I could cover the
distance light would travel (300,000,000 m)
```