Lab 9 - Life_
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School
Florida State University *
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Course
1002
Subject
Astronomy
Date
Dec 6, 2023
Type
Pages
7
Uploaded by Kyndeng36
Astronomy 1010 Lab
–
Life in the Universe
– V2.0
NAME:
Learning Objectives
:
I
Science Processing Skills
: Interpreting data along with applying and
evaluating mathematical relationships.
Learning about the Drake Equation and SETI.
Learning about the Fermi Paradox.
How all of the points above tie together in the search for life.
Introduction
:
In space there are countless constellations, suns and
planets; we see only the suns because they give light; the planets remain
invisible, for they are small and dark.
There are also numberless earths
circling around their suns, no worse and no less than this globe of ours.
– From
De l’Infinito Universo e Mondi
, by Giordano Bruno, 1584.
Pre-Lab Exercises
Take a few minutes to answer the questions below thoughtfully (not simply
yes/no). Integrate as much material from class as you can when answering
and justify your responses.
1)Do you believe there is life outside of Earth? What about “intelligent
life”?
2)Do you believe there is life outside of Earth but within our own Solar
System?
3)Do you believe/suspect, that Earth has been visited by extraterrestrials?
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Drake Equation
In 1961, astronomer Dr.
Frank Drake wrote down a simple formula
for determining how many intelligent civilizations exist in our Milky Way
galaxy. Today, the formula is known as the
Drake Equation
–
N
is the number of technologically advanced civilizations.
R
*
is the rate of star formation per year.
F
p
is the fraction of those stars with planets.
N
e
is the number of habitable planets in a solar system.
F
l
is the fraction of habitable planets in which life forms.
F
i
is the fraction of life-bearing planets where intelligent life emerges.
F
c
is the fraction of intelligent civilizations that send detectable signals.
L
is the length of time a civilization sends detectable signals.
4)Explain why the Drake Equation is different from asking “How prevalent
is life in the Universe?”
5)Take your best shot! Calculate
N
using what you believe are reasonable
values. Note that you are not expected to know these values – use what
you have learned from class and estimate what you think are reasonable
values for the variables in the equation.
6)Supposedly the original values that Drake used were as follows:
R
*
=
10,
F
p
= 0.5,
N
e
= 2,
F
l
= 1,
F
i
= 0.01,
F
c
= 0.01, and
L
= 10,000. How
does your answer to (5) compare with Drake’s original number?
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7)Today, we know that the
observable Universe
is not infinite (this the-
ory will be discussed in detail in 1020)! While there are not “numberless
earths” we suspect that there are so many planets that they are seemingly
countless
. We have confirmed over 5100
exoplanets
– planets beyond our
Solar System. While this number is small, we have truly only begun search-
ing for them, and we believe there are at least 100 billion planets in our
Milky Way. While we currently do not know how many planets may be
habitable, many scientists believe the answer might be astoundingly large.
Current estimates are:
R
*
= 1,
F
p
= 1,
N
e
= 0.2,
F
l
= 1,
F
i
= 1, and
F
c
= 1. You will notice that the only value not included and arguably the
most “controversial” number is the lifetime of a technologically advanced
civilization. The famed astronomer and science communicator, Carl Sagan,
noted that an advanced civilization, such as our own, might “extinguish”
itself through war. Hence, perhaps
L
is only 10,000 years. However, other
scientists believe the value is far larger. Some have argued that
L
is in fact
closer to the age a star could sustain life, and this could be 10 billion years
(or more)! If we are optimistic, what value do we get for
N
?
https://www.seti.org/press-release/seti-institute/press-release/biography-seti-pioneer-
jill-tarter-making-contact
Renowned astronomer Jill Tarter has spent her career studying the pos-
sibility of life existing beyond our own planet Earth!
Page 4
Meet Gliese 357 d
Located only 31 light-years from us, GJ 357 d, is a
super-Earth
or
planet that is more massive than the Earth but less massive than Neptune-
like planets. It is located within its host-star’s
habitable zone
, which is
the region around a star where liquid water could survive on a planet’s
surface.
8)The planet receives as much energy as Mars. Mars, as you learned, has
no detectable liquid water on its surface.
Why might the situation be
different for GJ 357 d?
9)Currently there are very few confirmed “potentially habitable exoplan-
ets”.
A list of such planets can be found in various data sets, including
in
Wikipedia
. Look at one such planet in the list, and compare it with
the Earth and GJ 357 d. What are some similarities and differences? Fur-
thermore, if there are potentially hundreds of millions of such habitable
planets, why are they so difficult to detect?
Page 5
Where are all the aliens???
If the Universe is teeming with life, why is it so quiet in our neck of the
woods?
That question is commonly referred to as the
Fermi paradox
.
Here are a few things to consider:
A)Most galaxies are so far away from us that even if we had advanced
technology to travel between galaxies, millions to billions of years would
pass by the time we got “there”! Thus, galaxies might be teeming with life
far beyond the Milky Way, and we will almost certainly never know.
So let us focus on our galaxy:
B)The Milky Way is believed to be around 13.5 billion years old.
The
Earth is about 4.5 billion years old. Therefore in principle, there should
have been a long period of time for other civilizations to evolve before hu-
manity.
C)While we are currently “a long way” from colonizing the Milky Way,
studies suggest it could actually be very quick, just a few million years!
Again, consider that the galaxy is 13,500 million years old, and you can
see this is, relatively speaking, very quick.
Despite (B) and (C), there currently is no direct evidence for intelligent
civilizations outside of Earth. Why might that be?
10)Can you come up with some ideas? Discuss it with your group.
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12)Based on this lab, has your thoughts on any of the following changed:
Do you believe there is life outside of Earth?
Do you believe
there is intelligent life outside of Earth?
It is always important to be both critical, and open-minded at the same
time. Just because we have not found any life outside of Earth, as of yet,
certainly does not rule it out. That said, one very enjoyable aspect of all
this is imagination – “I wonder what aliens might act and look like?”
13)Sketch below (or describe if your artistic skills are not up to task) an
alien living on another planet! Explain why the alien is the way it is – for
example, perhaps the alien’s planet is orbiting a star much dimmer than
the Sun and therefore needs big eyes! Be creative, have fun in your final
Astronomy 1010 Lab Question
F
Questions, suggestions? –
Dr. Idan Ginsburg
– iginsburg@gsu.edu
Page 8