Practice English Speaking&Listening with: Why can't we see the Apollo lunar landers on the Moon from Earth ?

When you look at the moon, just remember

that somewhere on lunar face the

remains of Apollo 11, 12, 14, 15, 16 and 17

along with eight unmanned Russian lunar

missions and five pre Apollo unmanned

American surveyor missions are all still

there silently looking back, unless of

course you're a NASA non-believer.

So why can't we see these from Earth,

why can't we train our best telescopes

on to the moon's surface and see them

exactly where we left them the best part

of 50 years ago.

Well there's a bit of a problem and that

is that the moon is 384,000 kilometers

or 238,000 miles away and the Landers

and all the things that behind are just a

few meters across. To give you an idea of

just how difficult this problem is it's

like looking for an object size of a

coin from a thousand miles away or the

equivalent from New York to Florida, so

you need a pretty serious telescope. One

telescope which springs to mind is the

Hubble Space Telescope, after all if it

can see galaxies billions of light-years

away then it should be able to see the

Apollo landings easily.... shouldn't it.

Well as with many things to do with

space is not that simple.

Yes, the hubble space telescope was indeed

designed to look at very faint objects

at astronomical distances but those

objects are clusters of galaxies

trillions of miles across, it was just

not designed to take high-resolution

images of small objects are fairly close

ranges in astronomical terms like to the

moon.

The problem is down through a resolution

of the images at the telescope produce

and that is ultimately limited by the

law of physics. The resolution determines

the smallest picture element or pixel in

the image the higher resolution the more

the fine detail image can be seen.

In a telescope the bigger the mirror the

more of a magnification so the closer

the object will appear but very large

magnifications be images also affected

by the wavelength of light itself

shorter the wavelength of light like

ultraviolet light a fine of a detail

that can be captured and the resolution

increases but invisible light as we go

from blue to green to red, the wavelength

increases and a resolution is actually

decreased. The Hubble has a mirror which is

2.4 meters in diameter which was the

largest that will fit into space shuttle

by when it was placed in orbit.

This gives it a single pixel resolution

in ultraviolet light of about 43 meters

across on the moon surface, anything

smaller than 43 meters will just be

hidden in a single dot which cannot

resolve any further. In fact we need

really two pixels or more to make out

anything at all. In visible light it's

even worse and the size of the area

covered by a single pixel increases 90

meters. The only way we're going to see

any object few meters across on the

lunar surface is either to increase the

size of a mirror or get closer to the

object we're looking at. Back on earth

the current largest optical telescope in

the world is the GTC on the Canary

Islands with a mirror diameter of 10.4

meters. This increases the resolution

so that the smallest area covered by one

pixel will be 20 meters across invisible

light still too big to see the Apollo lander

which is just over 4 meters across.

In fact to see the Apollo landers from

Earth you need a telescope with a mirror

size 10 times that of GTC or about 100

meters across and that does not yet

exist. Even with a 100 meter telescope

would only give you a two meter

resolution coverage so the lander would be

two pixels in visible light and four

pixels in ultraviolet light, still not

enough to discern any real detail. This

is the reason why we are unable to see any

of the vehicles on the moon from the

earth and although in theory it is

possible to use a group of telescope in

an array to get a higher resolution,

no one has yet done it because telescope

time is in very high demand and very

limited and looking for objects that we

know already exists is just not a high

enough priority just to disprove that

none believers. What we need to do is put

a camera in orbit around the moon just

like the spy satellites or the ones which

gives the satellite mapping services

like Google Earth for example. In 2009

that's exactly what happened when the

Lunar Reconnaissance Orbiter or LRO was

launched to photograph and survey the moon

from a distance between 12 and 100

miles above its surface. Even

with a much smaller camera lens, at its

closest passes,

it has a resolution of just 0.5 meters

or 18 inches per pixel.

So now all of the Apollo sites with the

lunar landers, the rover's as well as the

russian site can now be seen for the

first time since they landed. This also

shows the trails left in the lunar dust

by the astronauts both on foot and in

the lunar Rovers, the science experiments

that were left there over 44 years ago

are still visible and even the shadows

of the American flags can be seen as they

vary in size due to the changing position of

the Sun during lunar. Day we can't

see the flags themselves because they

are hanging vertically and the camera is

looking for top down position

and the flags for just a fraction of an

inch thick. So now we have the

photographic evidence of the Apollo

landers, unless of course you don't

believe anything official that comes out

of NASA and that they were placed

there by robotic Landers or aliens years

later or the moon is a hologram and

the earth is flat.

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