Albedo
Excitement
over the recent eclipse of the sun has sent some of us scurrying back
to our astronomy books. Like any science, astronomy has its own
vocabulary and uses some interesting words well worth knowing. One of
the most interesting is the word Albedo. The
word is from Latin and brings together the word Albus
meaning ‘white or whiteness’ and the
suffix -edo, meaning
‘bringing forth’. It can refer to the whitish inner portion of
the rind on an orange or lemon but when astronomers use it they are
thinking of an object’s ability to reflect light (or in some cases
any form of electromagnetic radiation, from radio waves to gamma
rays). When they speak of a planet’s albedo
they are normally referring to its brightness. When light strikes a
planet, some is absorbed by the planet’s surface or its atmosphere,
and some is reflected or scattered. The albedo
is the ratio between how much light strikes an object and how much is
reflected.
Of
the planets in our solar system Venus has the highest albedo.
That is partly why it looks so bright in the sky. It reflects upwards
of 65% of the sunlight that hits it. This is because of a blanket of
highly reflective clouds surrounding it.
Greek
musician Vangelis Papathinassou once released an album called,
intriguingly, Albedo 0.39. The
title track reels off a list of statistics including
Mean
distance from the sun: 92 million 957 thousand and 200 miles
Mean
Orbital velocity: 66,000 miles per hour
Length
of the mean solar day: 24 hours and 3 minutes and 56.5555 seconds at
mean solar time
Length
of the mean sidereal day: 23 hours and 56 minutes and 4.091 seconds
at mean sidereal time
Mass:
6600 million million million tons
Equatorial
diameter: 7,927 miles
Polar
diameter: 7,900 miles
The
list closes with the repeated phrase, Albedo:
0.39.
Estimates
for the earth in fact vary between 30% and 40%. Our moon on the
other hand has an albedo
of somewhere between 0.10 and 0.17, reflecting only about 10% of the
light it receives. The moon appears relatively bright to us only
because it is so near.
Of
all known objects mirrors have the highest albedos.
However, they can only reflect light in one direction and are not
perfect reflectors. A small amount of light always gets trapped by
the mirror’s surface.
In
2 Corinthians 3:18 Paul speaks of how believers all
reflect
the Lord’s glory and
are
being transformed into his likeness with ever-increasing glory, which
comes from the Lord, who is the Spirit. The
Christian should increasingly reflect the Lord Jesus in his life. His
albedo
factor,
as it were, should rise with every passing year. Like the moon some
may appear to be bright Christians yet in fact do little to reflect
the glory of God. Only Jesus Christ, who is the
radiance of God’s glory and the exact representation of his being
perfectly reflects
the glory of God the Father but we should all endeavour by his grace
to shine out for the Lord by reflecting the glory of God as seen in
the face of Christ. What is your spiritual albedo
number?
This article first appeared in Grace Magazine
