Astronomy

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Originally Posted by Dreamwoven

Something else I have been questioning is the description of a planet as "earth-like". It just means rocky and that it is within the habitable zone in terms of distance from its sun: http://www.universetoday.com/130469/...ma-centauri-b/.

We also have only "life on earth" as a yardstick.

Of course it is encouraging that Proxima Centauri b does fulfil the basic criteria, but then so does Mars...

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The problem with Proxima Centauri, among other things, is that it periodically flares, and unless I'm mistaken is part of a distant binary star system... most people don't understand just how unlikely Life is, even on our extremely "earth-like" planet. Any solar system that falls short of our rather amazing circumstances, would be hard pressed to support higher lifeforms.
Also consider, when our sun was much younger and burned cooler, it was Venus that was in that habitable "goldilocks zone".

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Originally Posted by Dreamwoven

There are risks in long-distance space journeys made by tiny sail propulsion. This post in Universe Today discusses them:

http://www.universetoday.com/130458/...nherent-risks/

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The small sails still seem like something worth exploring. They should try to go to the Moon first. I wonder what kind of information such a small craft could actually provide.

Regarding life on that new exoplanet I expect they will find life on Europa first under the ice layer or on some other object in our solar system. But until one finds an example we still have the possibility that life only occurred on Earth.

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Originally Posted by Iain Sparrow

The problem with Proxima Centauri, among other things, is that it periodically flares, and unless I'm mistaken is part of a distant binary star system... most people don't understand just how unlikely Life is, even on our extremely "earth-like" planet. Any solar system that falls short of our rather amazing circumstances, would be hard pressed to support higher lifeforms.
Also consider, when our sun was much younger and burned cooler, it was Venus that was in that habitable "goldilocks zone".

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I didn't know Proxima Centauri is a flare star. I hadn't thought of that as a dimension to consider, Iain.

Something I leaned today was what a lagrange point was, and how useful it can be for space exploration. I got it from here: http://www.universetoday.com/102785/...grange-points/. The James Webb space telescope will be placed at one of these.

I can intuitively see why there are Lagrange points at L1, L2 and L3. It surprises me that there are also Lagrange points at L4 and L5, but they are the most stable ones. I wonder why there aren't Lagrange points elsewhere.

I finished a book of essays called "What is Consciousness?". I don't recommend it, but one of the essays discussed the "holographic theory of the universe". The idea is that our universe is a 3D projection from a 2D region outside or on the edge of the universe. It didn't make a lot of sense and apparently there is now evidence against it: http://blogs.discovermagazine.com/d-.../#.V8MUkpgrLIU

But failed theories are also useful. The tools and experience used to build those experiments can be put to other uses.

That was a good idea, YesNo. Weird to conceive of space as a hologram...

The latest issue of Popular Astronomy (p. 5) has an interesting article on Gravitational Waves by Melanie Davies on LISA Pathfinder (a collaborative mission with the European Space Agency). The LISA Space Observatory is due to be launched in 2034 and consisting of a three-spacecraft constellation with arm-lengths of a million kilometres using laser interferometry between the satellites able to detect thousands of gravitational wave sources. It will supplement existing signal detection for ground-based gravitational wave observatories like LIGO.

This was an interesting article on the possible existence of a large Plant 9 with an orbit around the sun, but very far out, in the Oort Cloud.:
http://www.universetoday.com/130524/...h-new-objects/.

We are still puzzled over what is in orbit around our own sun...

This is an interesting article on how difficult it is to know such a seemingly simple fact.

At least they are able to increasingly narrow down the possible location of planet 9. It also makes me wonder about dark matter. That is based on gravitational effects. If enough objects are found in the Oort Cloud would that disprove the existence of dark matter in our solar system?

An interesting piece on Mars and one of its moons, Phobos:

http://www.universetoday.com/130544/...roovy-mystery/

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Originally Posted by YesNo

At least they are able to increasingly narrow down the possible location of planet 9. It also makes me wonder about dark matter. That is based on gravitational effects. If enough objects are found in the Oort Cloud would that disprove the existence of dark matter in our solar system?

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It would not prove or disprove either the existence of, or influence of Dark Matter on our solar system.
The theory that seems to be gaining traction lately, is that Dark Matter coalesces in the central plain of spiral galaxies, like our Milky Way. And that our galaxy periodically passes through, or brushes this Dark Matter disk, roughly every 30 million years. Andromeda, our sister galaxy exhibits both rotational irregularities, and debris clusters that seem to support the Dark Matter Disk theory... but let's face it, they simply don't know. Some scientists are linking this 30 million year cycle with mass extinction events on Earth, which to me is just too convenient.

I don't understand the speculations about dark matter well enough to know whether I would find them plausible or not, however, I would like to know more, but getting off my butt to find out is another matter. Having dark matter coalesce seems puzzling. If it can coalesce, why doesn't it coalesce into a planet like ordinary matter? Sometimes I wonder if the supposed existence of dark matter could be explained away by assuming that big-G, the gravitational "constant", is not constant. That set of spacecrafts designed to detect gravitation waves will hopefully give some answers.

I have to confess that I find the debates over dark matter very hard to grasp. Or perhaps it is just too complex for those who are not in the know on this.

It occurred to me that saying that big-G is not constant, as I suggested earlier, doesn't help a lot. It may explain the mathematical anomalies about gravitation, but it opens up other questions: Why is big-G not constant? What makes it change? The change will not likely be "random", meaning that one doesn't have to explain it. The change will vary enough beyond the random that some explanation of that non-random change will be required as well.

Saying something is a constant is more or less a claim that we (hopefully) don't have to explore that part of reality any further.

I don't think we know enough yet about what dark matter is, never mind how it works.

See this link on the Spitzer Space Telescope: http://www.nasa.gov/feature/goddard/...nd-dark-matter

Any form of non-randomness or non-uniformity can be viewed as structure that requires explanation as that shown in the CIB in your link. It is interesting that dark matter could be explained by the existence of many black holes formed during the first second of the existence of the universe.

The claim that the model fit the data was "surprisingly good" makes me wonder how good was the fit. I interpret it as meaning only that the fit was good enough that the model could not be rejected at the moment.