100th Anniversary Debate discussion

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RJN
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100th Anniversary Debate discussion

Post by RJN » Tue Apr 21, 2020 2:39 am

This topic will feature civil discussion of the 100th Anniversary Astronomical Debate: Life in the Universe. Please post here any civil thoughts, comments, questions, or reasonable opposing points of view involving that online debate. The URLs of the debate are
https://apod.nasa.gov/debate/debate100th.html
and
http://phy.mtu.edu/debate/debate100th.html .

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Re: 100th Anniversary Debate discussion / S. Hossenfelder

Post by drprh » Thu Apr 30, 2020 9:35 am

@Sabine Hossenfelder:

Sabine, could you please add some substance to what you said about signal transfer with a speed greater than c?
I'm a physicist, and of course SRT (Special relativity) does not per se preclude velocities exceeding that of light. Only I don't see how they should be obtained or reached. There is no continuous transformation from our timelike reality to "the other side", to the "tachyon world" or whatever one might call it.
Thanks in advance.
Peter

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Re: 100th Anniversary Debate discussion

Post by ems57fcva » Tue May 05, 2020 2:44 am

Just for grins, I'll put in my two cents. I for one am certain that we will find life on Mars. But I also predict that they will be microscopic organisms which are exiles from Earth. Their ancestors will have been blasted off of Earth by one or more giant meteorite impacts, and were lucky enough to not just survive the ejection from Earth and the cruise to Mars but also to land in a place on Mars where their survival was possible. Those organisms will have Earthly DNA, but will also grow and reproduce very slowly in order to deal due to the relative lack of resources on Mars.

It may also be possible that some hitchhikers on our probes to Mars are also survivors, but they will not have had time to adapt and spread like the survivors of an ancient giant meteorite impact would have.

Otherwise I would largely defer to the presenters in this debate. Since the Sun has a higher metallicity than most stars of its age, I wonder if the Earth did not end up with much high levels of "metals" than its analogs did. If so, then the evolution of complex life forms may have been aided by that fortuitous circumstance. But even if we are among the first of the intelligent life forms, life itself still must have appeared on many other planets in many other stellar systems over the billions of years the galaxy has existed, and we eventually will be able to identify their biosignatures.

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Re: 100th Anniversary Debate discussion

Post by Chris Peterson » Tue May 05, 2020 4:42 am

ems57fcva wrote:
Tue May 05, 2020 2:44 am
Just for grins, I'll put in my two cents. I for one am certain that we will find life on Mars. But I also predict that they will be microscopic organisms which are exiles from Earth. Their ancestors will have been blasted off of Earth by one or more giant meteorite impacts, and were lucky enough to not just survive the ejection from Earth and the cruise to Mars but also to land in a place on Mars where their survival was possible. Those organisms will have Earthly DNA, but will also grow and reproduce very slowly in order to deal due to the relative lack of resources on Mars.

It may also be possible that some hitchhikers on our probes to Mars are also survivors, but they will not have had time to adapt and spread like the survivors of an ancient giant meteorite impact would have.

Otherwise I would largely defer to the presenters in this debate. Since the Sun has a higher metallicity than most stars of its age, I wonder if the Earth did not end up with much high levels of "metals" than its analogs did. If so, then the evolution of complex life forms may have been aided by that fortuitous circumstance. But even if we are among the first of the intelligent life forms, life itself still must have appeared on many other planets in many other stellar systems over the billions of years the galaxy has existed, and we eventually will be able to identify their biosignatures.
Although I think neither scenario is likely, it would make more sense for life to have formed on Mars and rode to Earth on meteorites than the other way around. The energy required to get a meteorite off of Mars and to the Earth is much, much less than going in the other direction, meaning any living organisms are more likely to survive.
Chris

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Re: 100th Anniversary Debate discussion

Post by ems57fcva » Tue May 05, 2020 4:38 pm

Chris Peterson wrote:
Tue May 05, 2020 4:42 am
ems57fcva wrote:
Tue May 05, 2020 2:44 am
Just for grins, I'll put in my two cents. I for one am certain that we will find life on Mars. But I also predict that they will be microscopic organisms which are exiles from Earth. Their ancestors will have been blasted off of Earth by one or more giant meteorite impacts, and were lucky enough to not just survive the ejection from Earth and the cruise to Mars but also to land in a place on Mars where their survival was possible. Those organisms will have Earthly DNA, but will also grow and reproduce very slowly in order to deal due to the relative lack of resources on Mars.

It may also be possible that some hitchhikers on our probes to Mars are also survivors, but they will not have had time to adapt and spread like the survivors of an ancient giant meteorite impact would have.

Otherwise I would largely defer to the presenters in this debate. Since the Sun has a higher metallicity than most stars of its age, I wonder if the Earth did not end up with much high levels of "metals" than its analogs did. If so, then the evolution of complex life forms may have been aided by that fortuitous circumstance. But even if we are among the first of the intelligent life forms, life itself still must have appeared on many other planets in many other stellar systems over the billions of years the galaxy has existed, and we eventually will be able to identify their biosignatures.
Although I think neither scenario is likely, it would make more sense for life to have formed on Mars and rode to Earth on meteorites than the other way around. The energy required to get a meteorite off of Mars and to the Earth is much, much less than going in the other direction, meaning any living organisms are more likely to survive.
Life forming on Mars first and seeding Earth is not impossible. Whether any of that original life would have survived the desiccation of Mars is another matter. I suspect that Mars was never as hospitable to life as Earth has been. However, it will be easy to tell the difference between lineages that diverged over 3 billion years ago and those that diverged more recently.

The issue of its being much harder for an Earth rock to get to Mars that for a Mars rock to get to Earth is a good one. However, a big enough impact will eject enough rock that some of it will be lucky enough to end up in a Mars-bound solar orbit. Then with the prevalence of life of Earth it is almost a given that any such rock will contain some organisms. For an organism that has adapted to the general lack of resources in an underground environment, Mars may not be that inhospitable a place. But I will admit that this scenario assumes that an organism can survive the journey and the shocks on either end of it. Even so, it only takes one survivor in a good enough spot to start the bacterial colonization of Mars.

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Re: 100th Anniversary Debate discussion

Post by demessieres » Tue May 26, 2020 2:48 pm

I loved reading over these replies, great perspectives! But why are all of the contributing astronomers white?

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RJN
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Re: 100th Anniversary Debate discussion

Post by RJN » Thu May 28, 2020 6:12 pm

demessieres wrote:
Tue May 26, 2020 2:48 pm
I loved reading over these replies, great perspectives! But why are all of the contributing astronomers white?
Thank you for your kind words about the debate. You raise a good point about diversity and inclusion. We tried to create a diverse base although we followed no formal criteria. We remain open to submissions from everyone and will judge them only by scientific content. Although we did not request the race of submitted entrants, we do know that at least one self-identifies as non-white.

- RJN