Difference between revisions of "Life on Mars?"
From Universe in Problems
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[[Category:Cosmo warm-up|8]] | [[Category:Cosmo warm-up|8]] | ||
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<div id="Mars1"></div> | <div id="Mars1"></div> | ||
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| − | === Problem 1 === | + | === Problem 1: on intelligent aliens === |
| − | Consider a highly developed alien civilization, actively exploring the Earth in search of intelligent life. How would citizens of opposite part of Milky Way see | + | Consider a highly developed alien civilization, actively exploring the Earth in search of intelligent life. How would citizens of opposite part of Milky Way see those from the Earth? And what about citizens of Andromeda galaxy? |
<div class="NavFrame collapsed"> | <div class="NavFrame collapsed"> | ||
<div class="NavHead">solution</div> | <div class="NavHead">solution</div> | ||
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<div id="Mars2"></div> | <div id="Mars2"></div> | ||
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| − | === Problem 2 === | + | === Problem 2: homo sapiens in the Galaxy === |
Estimate the number of stars, which had already received the signal about homo sapiens being (existence) on the Earth. | Estimate the number of stars, which had already received the signal about homo sapiens being (existence) on the Earth. | ||
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<div id="Mars3"></div> | <div id="Mars3"></div> | ||
<div style="border: 1px solid #AAA; padding:5px;"> | <div style="border: 1px solid #AAA; padding:5px;"> | ||
| − | === Problem 3 === | + | === Problem 3: the Galactic Habitable Zone === |
| − | Inhabited planets in our Galaxy are likely to be located within so--called | + | Inhabited planets in our Galaxy are likely to be located within so--called galactic habitable zone, which has a form of narrow ring with a radius greater or approximately equal to half radius of Galaxy. Explain, why genesis (?) is unlikely to happen at too small and too large galactocentric distances. |
| − | <div class="NavFrame collapsed"> | + | <!-- <div class="NavFrame collapsed"> |
<div class="NavHead">solution</div> | <div class="NavHead">solution</div> | ||
<div style="width:100%;" class="NavContent"> | <div style="width:100%;" class="NavContent"> | ||
<p style="text-align: left;"></p> | <p style="text-align: left;"></p> | ||
</div> | </div> | ||
| − | </div></div> | + | </div> --></div> |
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<div id="Mars4"></div> | <div id="Mars4"></div> | ||
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| − | === Problem 4 === | + | === Problem 4: Habitable Zone dynamics === |
Why does the width of galactic habitable zone gradually increase in time? | Why does the width of galactic habitable zone gradually increase in time? | ||
| − | <div class="NavFrame collapsed"> | + | <!-- <div class="NavFrame collapsed"> |
<div class="NavHead">solution</div> | <div class="NavHead">solution</div> | ||
<div style="width:100%;" class="NavContent"> | <div style="width:100%;" class="NavContent"> | ||
<p style="text-align: left;"></p> | <p style="text-align: left;"></p> | ||
</div> | </div> | ||
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<div id="Mars5"></div> | <div id="Mars5"></div> | ||
<div style="border: 1px solid #AAA; padding:5px;"> | <div style="border: 1px solid #AAA; padding:5px;"> | ||
| − | === Problem 5 === | + | === Problem 5: the Fermi paradox === |
| − | One of the possible formulations of the Fermi paradox, or the ''great silence'' paradox, is the following: if there is intelligent life in the Universe, why does it not emit any signal into space and generally manifest itself in any way? This paradox is related to the name of Fermi, because once having listened to the arguments of his colleagues stating that there | + | One of the possible formulations of the Fermi paradox, or the ''great silence'' paradox, is the following: if there is intelligent life in the Universe, why does it not emit any signal into space and generally manifest itself in any way? This paradox is related to the name of Fermi, because once having listened to the arguments of his colleagues stating that there is a great number of highly developed technological civilizations, he asked after some pause: ''So, where are they?'' Give arguments to support or disprove the paradox. |
| − | <div class="NavFrame collapsed"> | + | <!-- <div class="NavFrame collapsed"> |
<div class="NavHead">solution</div> | <div class="NavHead">solution</div> | ||
<div style="width:100%;" class="NavContent"> | <div style="width:100%;" class="NavContent"> | ||
<p style="text-align: left;"></p> | <p style="text-align: left;"></p> | ||
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| − | === Problem 6 === | + | === Problem 6: varying electron mass === |
| − | * Imagine for a moment, that electron has mass several times larger that | + | $^*$ Imagine for a moment, that electron has mass several times larger that actual. If other conditions ware the same, how would our Universe change? |
| − | <div class="NavFrame collapsed"> | + | <!-- <div class="NavFrame collapsed"> |
<div class="NavHead">solution</div> | <div class="NavHead">solution</div> | ||
<div style="width:100%;" class="NavContent"> | <div style="width:100%;" class="NavContent"> | ||
<p style="text-align: left;"></p> | <p style="text-align: left;"></p> | ||
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| − | === Problem 7 === | + | === Problem 7: electron mass from anthropic principle === |
Our Sun emits energy during billions of years and thus supports life development on the Earth. It is possible due to very slow reaction of deuteron creation from two interacting protons. Find the limiting value of electron mass providing the necessarily low rate of such reaction. | Our Sun emits energy during billions of years and thus supports life development on the Earth. It is possible due to very slow reaction of deuteron creation from two interacting protons. Find the limiting value of electron mass providing the necessarily low rate of such reaction. | ||
| − | <div class="NavFrame collapsed"> | + | <!-- <div class="NavFrame collapsed"> |
<div class="NavHead">solution</div> | <div class="NavHead">solution</div> | ||
<div style="width:100%;" class="NavContent"> | <div style="width:100%;" class="NavContent"> | ||
<p style="text-align: left;"></p> | <p style="text-align: left;"></p> | ||
</div> | </div> | ||
| − | </div></div> | + | </div> --></div> |
Revision as of 15:06, 11 October 2012
Contents
Problem 1: on intelligent aliens
Consider a highly developed alien civilization, actively exploring the Earth in search of intelligent life. How would citizens of opposite part of Milky Way see those from the Earth? And what about citizens of Andromeda galaxy?
solution
Problem 2: homo sapiens in the Galaxy
Estimate the number of stars, which had already received the signal about homo sapiens being (existence) on the Earth.
solution
Problem 3: the Galactic Habitable Zone
Inhabited planets in our Galaxy are likely to be located within so--called galactic habitable zone, which has a form of narrow ring with a radius greater or approximately equal to half radius of Galaxy. Explain, why genesis (?) is unlikely to happen at too small and too large galactocentric distances.
Problem 4: Habitable Zone dynamics
Why does the width of galactic habitable zone gradually increase in time?
Problem 5: the Fermi paradox
One of the possible formulations of the Fermi paradox, or the great silence paradox, is the following: if there is intelligent life in the Universe, why does it not emit any signal into space and generally manifest itself in any way? This paradox is related to the name of Fermi, because once having listened to the arguments of his colleagues stating that there is a great number of highly developed technological civilizations, he asked after some pause: So, where are they? Give arguments to support or disprove the paradox.
Fine-tuning of the Universe
Problem 6: varying electron mass
$^*$ Imagine for a moment, that electron has mass several times larger that actual. If other conditions ware the same, how would our Universe change?
Problem 7: electron mass from anthropic principle
Our Sun emits energy during billions of years and thus supports life development on the Earth. It is possible due to very slow reaction of deuteron creation from two interacting protons. Find the limiting value of electron mass providing the necessarily low rate of such reaction.
