Tag Archives: Science

News

New study on tidal heating strengthens stellar habitability argument

7 Comments
Circumstellar Habitable Zone
Circumstellar Habitable Zone

Note: If you need a refresher on the habitability argument, click here.

Here’s an article entitled “Tidal heating shrinks the ‘goldilocks zone’: Overlooked factor suggests fewer habitable planets than thought”. It appeared in Nature, the most prestigious peer-reviewed science journal.

The gist of it is that tidal forces can alter orbits so that planets don’t spend all of their orbit in the habitable zone. If planets go outside the habitable zone, it damages their supply of liquid water, and any life chemistry going on in there is disrupted.

Excerpt:

A previously little-considered heating effect could shrink estimates of the habitable zone of the Milky Way’s most numerous class of stars — ‘M’ or red dwarfs — by up to one half, says Rory Barnes, an astrobiologist at the University of Washington in Seattle. That factor — gravitational heating via tides — suggests a menagerie of previously undreamt-of planets, on which tidal heating is a major source of internal heat. Barnes presented the work yesterday at a meeting of the American Astronomical Society’s Division on Dynamical Astronomy in Timberline Lodge, Oregon.

The habitable zone is the orbital region close enough to a star for a planet to have liquid water, but not so close that all of the water evaporates. For our Sun, the zone extends roughly from the inner edge of the orbit of Mars to the outer edge of that of Venus. For smaller, cooler stars, such as M-class dwarfs, the zone can be considerably closer to the star than Mercury is to the Sun. And because close-in planets are easier to spot than more distant ones, such stars have been a major target for planet hunters seeking Earth-like worlds.

There’s just one problem with finding habitable planets around such stars, says Barnes. Because tidal forces vary dramatically with the distance between a planet and its star, closer orbits also result in massively larger tidal forces.

Since planets do not have perfectly circular orbits, these tidal forces cause the planet to flex and unflex each time it moves closer to or further from its star; kneading its interior to produce massive quantities of frictional heat. Substantial heat can be produced, he added, with even slight deviations from a perfectly circular orbit. And, Barnes notes, other factors — such as the rate of the planet’s rotation and its axial tilt — can also influence heat production.

A similar tidal process makes Jupiter’s moon Io the most volcanic body in the Solar System. “I’m just scaling that Io–Jupiter system up by a factor of 1,000 in mass,” Barnes said at the meeting. “It’s the same process, on steroids.”

So, stars that are smaller and cooler will have a habitable zone that is closer to the star, exposing them to more tidal forces. More tidal forces makes their orbits less likely to stay circular – within the habitable zone around the star. These variations cause an increase in heat production on the planet. Too much heat means that the planet is unable to support liquid water on the surface, making it inhospitable for life. Therefore, solar systems with less massive stars can be ruled out as possible sites for life, because of these tidal forces.

Podcasts

Two astrophysicists dialog: Hugh Ross and Paul Davies on Unbelievable

Leave a comment

Here’s the description from the Unbelievable page:

Hugh Ross is an astronomer and founder of Reasons To Believe, an apologetics organisation aiming to show why modern science confirms and supports the Christian worldview. Paul Davies is a British astrophysicist and popular science author currently based at Arizona State University. An agnostic, much of his writing has focussed on the extraordinary “fine tuning” of the Universe that allows life to exist and why the universe’s order and intelligibility defy a purely naturalistic explanation. Hugh and Paul discuss whether the properties of our Universe may be the result of a creator God, competing hypotheses such as the multiverse, whether science can be used to test the Biblical worldview… and Hugh explains why he wants NASA to look for fossils on the moon.

The MP3 file is here.

Paul Davies is one of the scientists that William Lane Craig often quotes in his debates.

Like this quote for the cosmological argument:

The evidence for the Big Bang theory of the origin of the universe points to the creation of the universe out of nothing.  Not just matter and energy, but physical space and time themselves come into existence at the Big Bang.  In the words of the British physicist P. C. W. Davies, ‘the big bang represents the creation event; the creation not only of all the matter and energy in the universe, but also of spacetime itself.’

Or this quote for the fine-tuning argument :

British physicist P. C. W. Davies has calculated that the odds against the initial conditions being suitable for later star formation (without which planets could not exist) is one followed by a thousand billion billion zeroes, at least.  He also estimates that a change in the strength of gravity or of the weak force by only one part in 10100 would have prevented a life-permitting universe.

It’s interesting that Craig chooses non-theistic scientists as sources to support his premises.

By the way, did you know that Unbelievable is having a conference later this month? Click here to find out about it, especially if you like science apologetics.

Polemics

Ed Feser takes on Lawrence Krauss and Victor Stenger

3 Comments

From Ed Feser’s blog. (H/T Chris R.)

Excerpt:

I recently linked to philosopher of physics David Albert’s take down of Lawrence Krauss’s bookA Universe From Nothing.  (My own review of Krauss will soon appear in First Things.)  A reader calls my attention to this blog post in which Victor Stenger — Adjunct Professor of Philosophy at the University of Colorado, Professor Emeritus of Physics and Astronomy at the University of Hawaii, and author of several atheist tomes — rides to the rescue of Krauss against Albert.  (If only the other philosophically incompetent New Atheists had such a knight in shining armor!  O Dawkins, where is your Stenger?  O Coyne, where is your Victor?)

Unfortunately for Krauss, the intrepid Stenger shoots only blanks.  And misses.  Krauss, as you may know, argues that the laws of quantum mechanics (QM) show how a universe can arise from nothing.  Albert demurs, and Stenger responds:

[Albert] asks, “Where, for starters, are the laws of quantum mechanics themselves supposed to have come from?”  Krauss admits he does not know, but suggests they may arise randomly, in which case some universe like ours would have arisen without a prescribed cause.  In my 2006 book The Comprehensible Cosmos, I attempt to show that the laws of physics arise naturally from the symmetries of the void.

Later Stenger tells us that the “void” or “nothing” in question “can be described mathematically,” “has an explicit wave function,” and “is the quantum gravity equivalent of the quantum vacuum in quantum field theory.”

Of course, the problem with all of this is the same as the problem with the original suggestion that the laws of QM show that a universe can come from nothing.  The laws of QM are not nothing, and neither are “the symmetries of the void” nor anything that “can be described mathematically,” “has an explicit wave function,” etc.  In general, if you can characterize it in terms of physical law — which Krauss, Stenger, and like-minded atheists all want to do vis-à-vis “nothing” — then it isn’t nothing.  It’s something physical, and thussomething rather than nothing.  Obviously.

Obviously, that is, unless you are a New Atheist dogmatically attached to the utterly groundless proposition that all genuine questions simply must be susceptible of a scientific answer.  At this juncture Stenger does what an increasing number of atheists do when it is pointed out to them that their “explanations” of how the universe arose from nothing merely change the subject — they feign ignorance of English.  Writes Stenger:

Clearly, no academic consensus exists on how to define “nothing.”  It may be impossible.  To define “nothing” you have to give it some defining property, but, then, if it has a property it is not nothing!

But this is the muddleheaded stuff of a freshman philosophy paper — treating “nothing” as if it were an especially unusual, ethereal kind of substance whose nature it would require tremendous intellectual effort to fathom.  Which, as everyone knows until he finds he has a motive for suggesting otherwise, it is not.  Nothing is nothing so fancy as that.  It is just the absence of anything, that’s all.  Consider all the true existential claims that there are: “Stones exist,” “”Trees exist,” “Quarks exist,” etc.  To ask why there is something rather than nothing is just to ask why it isn’t the case that all of these statements are false.  Pretty straightforward.

To admit the obvious, though, would be to admit that there are questions that physics cannot answer, such as where the laws of physics themselves came from — or more precisely, since “laws” are just abstractions from a concrete physical reality that behaves in accordance with the laws, where this concrete physical reality itself comes from.  That nothing in physics answers this question was Albert’s point, and Stenger says absolutely nothing to answer it.

Read the rest. It’s really good! and there’s a lot more goodness there. 176 comments at the time I am writing this.

UPDATE: Peter Sean Bradley note that Krauss is now walking back his rhetoric in response to criticisms from people like atheist John Horgan.

I have been writing about Stenger and Krauss a lot lately, so here are the links in case you missed anything: